Authors: C. Parthiban, Pavithra. M, Vinod Kumar Reddy. L, Dwaipayan Sen and N. D. Pradeep SinghVol: 2 Pages: 3728-3734Journal: ACS Appl. Nano Mater. Year: 2019 Posted: 11 Jul 2019
Light-responsive fluorescent organic nanoparticles (NPs) based on tetraphenylethylene (TPE) have been developed for the release of 4 equiv of chlorambucil (Cbl) and photodynamic therapy (PDT) utilizing aggregation-induced-emission (AIE) phenomena. Our newly developed TPE(Cbl)4 NPs displayed strong fluorescence because of its AIE. Upon exposure to visible light, our TPE(Cbl)4 NPs simultaneously produced singlet oxygen and uncaged 4 equiv of the anticancer drug in a sequential manner in their aggregated state. On the other hand, the released photoproduct also exhibited PDT activity. In vitro studies showed that TPE(Cbl)4 NPs exhibited properties like self-tracking, cellular imaging, photoregulated chemo-photodynamic therapy, enhanced anticancer activity, and biocompatibility.<\/p>")">
Authors: Amrita Paul, Angana Biswas, Sreyashi Sinha, Sk. Sheriff Shah, Manoranjan Bera, Mahitosh Mandal and N. D. Pradeep SinghVol: 21 Pages: 2968-2972Journal: Org. Lett. Year: 2019 Posted: 11 Jul 2019
For the first time we have utilized push–pull stilbene as a visible light activated photoremovable protecting group (PRPG) for the uncaging of alcohols and carboxylic acids. The PRPG efficiently release caged molecules with good photochemical quantum yield. It is capable of monitoring the release in real time owing to its fluorescence “turn on” phenomenon upon photorelease in polar medium. The efficient photorelease and real time monitoring abilities of push–pull stilbene were employed for in vitro<\/em> drug delivery.<\/p>")">
Authors: Yarra Venkatesh, Kumari Shanti Kiran, Sk. Sheriff Shah, Amrita Chaudhuri, Satyahari Dey and N. D. Pradeep SinghVol: 17 Pages: 2640-2645Journal: Org. Biomol. Chem. Year: 2019 Posted: 11 Jul 2019
One- and two-photon activated sulfur dioxide donors based on a 4,5-dimethoxy-2-nitrobenzyl phototrigger have been developed. The designed donors have the ability to release not only SO2<\/small> but also a hydroxy-compound in a simultaneous manner. Furthermore, we demonstrated their application in combinatorial therapy by the dual release of SO2<\/small> and an active drug, i.e.<\/em> ferulic acid ethyl ester (FAEE) with self-monitoring ability. Next, we investigated the in vitro<\/em> cellular uptake and the capability of SO2<\/small> generation from the donors using a well-known coumarin-hemicyanine fluorescent probe. Finally, we evaluated the antibacterial activity of the designed donors (5a<\/strong>, 5b<\/strong> and 6<\/strong>) by broth dilution and agar well diffusion methods on E. cloacae<\/em> cells (MTCC 509). The results show that the donor 5a<\/strong> exhibits enhanced antibacterial efficacy compared to 5b<\/strong> and 6<\/strong>, due to the synergetic effect of dually released SO2<\/small> and FAEE.<\/p>")">
Authors: Melvin S.Samuel, Jayanta Bhattacharya, Sankalp Raj, Needhidasan Santhanam, Hemant Singh, N. D. Pradeep SinghVol: 121 Pages: 285-292Journal: International Journal of Biological Macromolecules Year: 2019 Posted: 11 Jul 2019
Authors: Amrita Chaudhuri, Yarra Venkatesh, Joyjyoti Das, Krishna Kalyani Behara, Smita Mandal, Tapas K. Maiti, and N. D. Pradeep SinghVol: 1 Pages: 6312-6319Journal: ACS Appl. Nano Mater. Year: 2018 Posted: 11 Jul 2019
In this paper, we have developed photoresponsive fluorescent organic nanoconjugates based on a single-component system for effective cancer treatment by a synergistic combination of photodynamic therapy (PDT) and chemotherapy. Our single-component system was synthesized by coupling the squaric acid and the coumarin-chlorambucil conjugate. Next, multifunctional squaric acid-coumarin-chlorambucil (Sq-Cou-Cbl) nanoconjugates were prepared by “simple reprecipitation technique”. The unique properties of the newly designed Sq-Cou-Cbl nanoconjugates are (i) a phototrigger for controlled anticancer drug (chlorambucil) release and a photosensitizer for PDT upon visible light irradiation (ii) cellular imaging and self-monitoring of the drug release by a noninvasive fluorescent technique and (iii) PDT activity of the released photoproduct thereby resulting in the improved therapeutic efficiency. Further, in vitro studies showed that Sq-Cou-Cbl nanoconjugates exhibited an enhanced anticancer activity by synergistic cytotoxic effect of PDT and chemotherapy on HeLa cells.<\/p>")">
Authors: C. Parthiban, Pavithra. M, Vinod Kumar Reddy. L, Dwaipayan Sen, Melvin Samuel. S and N. D. Pradeep SinghVol: 1 Pages: 6281-6288Journal: ACS Appl. Nano Mater. Year: 2018 Posted: 11 Jul 2019
In this paper, we have developed a light-activated single component fluorescent organic nanoparticles for synergistic combination therapy (chemo-photodynamic therapy) utilizing the combined benefits of aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) phenomena. The single-component organic nanoparticles were synthesized by coupling tetraphenylethylene (TPE) moiety with the p-hydroxy phenacyl-chlorambucil conjugate. Then, tetraphenylene-p<\/em>-hydroxyphenacyl-chlorambucil (TPE-p<\/em>HP-Cbl) nanoparticles were prepared by a simple reprecipitation technique. Our designed TPE-p<\/em>HP-Cbl NPs exhibited the unique benefits such as (i) aggregation-induced emission enhancement, (ii) large Stoke’s shift, (iii) the photoirradiation wavelength >410 nm, (iv) the drug release occurs only in the aggregated state upon photolysis, (v) PDT activity, (vi) real-time monitoring of drug release by a noninvasive fluorescence color change approach, and (vii) PDT activity of the released photoproduct (TPE-p<\/em>HP-OH), thereby resulting in the improved therapeutic efficiency. In vitro experiments show that TPE-p<\/em>HP-Cbl NPs display excellent properties such as cellular imaging, synergistic combination therapy, and biocompatibility.<\/p>")">
Authors: Melvin S.Samuel, Jayanta Bhattacharya, C. Parthiban, Gayathri Viswanathan, N. D. Pradeep Singhh,Vol: 49 Pages: 215-221Journal: Ultrasonics - Sonochemistry Year: 2018 Posted: 11 Jul 2019
In this study, the metal organic framework MOF [Zn(BDC)(DMF)] crystal was synthesized via<\/em> ultrasonic irradiation and solvothermal method. The synthesized MOF [Zn(BDC)(DMF)] crystal was characterized by PXRD, FTIR, FESEM-EDX, TGA, UV-DRS and BET. The catalytic activity of MOF [Zn(BDC)(DMF)] was investigated by 4-nitrophenol (4-NP) degradation under direct sunlight irradiation. The influence of various degradation parameters such as initial 4-NP concentration, dosage, pH and H2O2 concentration were investigated. The results indicated that the synthesized MOF [Zn(BDC)(DMF)] exhibited strong photocatalytic activity in the presence of NaBH4 under sunlight irradiation and the reduction of 4-NP to 4-aminophenol (4-AP) completed within 10?min. The study provides the synthesized MOF [Zn(BDC)(DMF)] crystal can be used as a high performance catalyst for the treatment of dyes in wastewater.<\/p>")">
Authors: C. Parthiban, M. Pavithra, L. Vinod Kumar Reddy, Dwaipayan Sen, S. Melvin Samuel and N. D. Pradeep SinghVol: 16 Pages: 7903-7909Journal: Org. Biomol. Chem. Year: 2018 Posted: 11 Jul 2019
Hydrogen sulfide (H2S) behaves like a two-edged sword, at low concentrations it has beneficial and cytoprotective effects, while at higher concentrations it exhibits toxicity. Hence there is a keen interest in developing light responsive H2S donors with a spatio-temporal controlled release. Herein, we report visible light activatable tetraphenylethylene conjugated p-hydroxyphenacyl (TPE-pHP-H2S) nanoparticles for the release of hydrogen sulfide (H2S) with a real time monitoring ability. Our newly designed photoresponsive single component organic nanoparticle based H2S donor is built by integrating the tetraphenylethylene (TPE) moiety and p-hydroxyphenacyl (pHP) group so that it can display both aggregation-induced emission (AIE) and excited state intramolecular proton transfer (ESIPT) properties. Aggregation-induced emission enhancement was exhibited by our TPE-pHP-H2S NP donor, which was then explored for the cellular imaging application. The ESIPT by the pHP moiety provided unique advantages to our TPE-pHP-H2S NP donor which include (i) the excitation wavelength extended to >410 nm (ii) a large Stokes shift (iii) a low inner filter effect and (iv) real-time monitoring of H2S release by a simple fluorescent colour change. In vitro studies showed that the TPE-pHP-H2S NP donor presents excellent properties like real-time monitoring, photoregulated H2S release and biocompatibility.<\/p>")">
Authors: Sk. Sheriff Shah, Amrita Paul, Manoranjan Bera, Yarra Venkatesh and N. D. Pradeep SinghVol: 20 Pages: 5533–5536.Journal: Org. Lett. Year: 2018 Posted: 11 Jul 2019
The direct hydroxylation of 2-arylpyridines and 2-arylbenzothiazoles via the merger of organic photoredox and metal catalysis is reported where 4CzIPN is used as the visible-light photocatalyst and Pd(OAc)2 as the metal catalyst. This method has been employed to synthesize organic molecules exhibiting excited-state intramolecular proton transfer properties for generating tunable luminescence responses.<\/p>")">
Authors: Krishna Kalyani Behara, Y Rajesh, Amrita Chaudhuri, Moumita Gangopadhyay, Mahitosh Mandal and N. D. Pradeep SinghVol: 6 Pages: 6042-6046Journal: J. Mater. Chem. B Year: 2018 Posted: 11 Jul 2019
Nitric oxide photodonor (NOD) conjugated perylene tetracarboxylate ester (TPT) based fluorescent organic TPT(NOD)4<\/small> nanoparticles (NPs) with aggregation induced NIR emission have shown photoinduced nitric oxide delivery along with a red to green emission transition. Time dependent imaging and dose dependent cytotoxicity studies of these NPs using U87MG cells demonstrate the self monitoring and real time reporting abilities and potential anticancer activity of the system, respectively.<\/p>")">
Authors: Sandipan Biswas, Y. Rajesh, Shrabani Barman, Manoranjan Bera, Amrita Paul, Mahitosh Mandal and N. D. Pradeep SinghVol: 54 Pages: 7940-7943Journal: Chem. Commun. Year: 2018 Posted: 11 Jul 2019
A new strategy for the detection of hypoxia and NO succeeded by photocontrolled delivery of an anticancer agent has been demonstrated. The developed system is able to produce distinct responses (dual channel) upon interaction with hypoxia and NO. This probe can also release anticancer drugs upon photoirradiation acting potentially as both a dual-analyte imaging agent and a prodrug.<\/p>")">
Authors: Yarra Venkatesh, Hemant Kumar Srivastava, S. Bhattacharya, Muneshwar Mehra, P. K. Datta, S. Bandyopadhyay, and N. D. Pradeep SinghVol: 20 Pages: 2241-2244.Journal: Org. Lett. Year: 2018 Posted: 07 Jul 2019
A one- and two-photon activated photoremovable protecting group (PRPG) was designed based on a carbazole fused o<\/em>-hydroxycinnamate platform for the dual (same or different) release of alcohols. The mechanism for the dual release proceeds through a stepwise pathway and also monitors the first and second photorelease in real time by an increase in fluorescence intensity and color change, respectively. Further, its application in staining live neurons and ex vivo imaging with two-photon excitation is shown.<\/p>")">
Authors: Yarra Venkatesh, Joyjyoti Das, Amrita Chaudhuri, Anupam Karmakar, Tapas K. Maiti, and N. D. Pradeep SinghVol: 54 Pages: 3106-3109.Journal: Chem. Commun. Year: 2018 Posted: 07 Jul 2019
An ESIPT based light activated hydrogen sulfide (H2<\/small>S) donor using a p<\/em>-hydroxyphenacyl phototrigger has been developed. The unique feature of our H2<\/small>S donor system is that it provides real-time monitoring of H2<\/small>S release by a non-invasive fluorescence colour change approach.<\/p>")">
Authors: Melvin S.Samuel, Vasudevan Subramaniyan, Jayanta Bhattacharya, Ramalingam Chidambaram, Tanvir Qureshi, N. D. Pradeep SinghVol: 48 Pages: 412–417.Journal: Ultrasonics - Sonochemistry Year: 2018 Posted: 07 Jul 2019
Authors: Melvin S.Samuel, Sk. Sheriff Shah, Vasudevan Subramaniyan, Tanvir Qureshi, Jayanta Bhattacharya, N. D. Pradeep SinghVol: 119 Pages: 540–547Journal: International Journal of Biological Macromolecules Year: 2018 Posted: 07 Jul 2019
Authors: Melvin S.Samuel, Vasudevan Subramaniyan, Jayant Bhattacharya, C.Parthiban, Santanu Chand, N. D. Pradeep SinghVol: 152 Pages: 116-125Journal: Composites Part B Year: 2018 Posted: 07 Jul 2019
In the present study, a novel nanocomposite<\/a> adsorbent<\/a> material was synthesized using chitosan<\/a> (CS), graphene oxide<\/a> (GO) and metal organic framework<\/a> (MOF [Zn(BDC)(DMF)]) for the adsorption of Chromium<\/a> (VI) heavy metal<\/a> from aqueous solution. The characterization<\/a> of the prepared GO-CS@MOF [Zn(BDC)(DMF)] was accomplished by powder X-ray diffraction<\/a> (PXRD), Fourier transform<\/a> infrared (FT-IR) spectroscopy, scanning electron microscopy<\/a> (SEM) and Brunauer–Emmett–Teller (BET), followed by Cr(VI) adsorption-desorption studies. Experimental parameters such as effect of pH, temperature, contact time, adsorbent dosage and shaking speed were optimized. The GO-CS@MOF [Zn(BDC)(DMF)] showed an adsorption capacity<\/a> of 144.92?mg\/g for Cr(VI) at pH 3.0. Thermodynamic properties (ΔGo, ΔHo, ΔSo) have been calculated and the process is found to be endothermic, favourable and spontaneous. The adsorption study of Cr(VI) by GO-CS@MOF [Zn(BDC)(DMF)] comprises both kinetic and isotherm<\/a> studies. The equilibrium adsorption followed Langmuir model and adsorption reaction was found to be pseudo-second order confirming chemisorption<\/a>. The developed GO-CS@MOF [Zn(BDC)(DMF)] nanocomposite material will serve as a new type of platform for removing Cr(VI) from wastewater.<\/p>")">
Authors: Sandipan Biswas, Rakesh Mengji, Shrabani Barman, Venugopal Vangala, Avijit Jana and N. D. Pradeep SinghVol: 54 Pages: 168-171Journal: , Chem. Commun Year: 2018 Posted: 07 Jul 2019
‘Aggregation Induced Emission + Excited State Intramolecular Proton Transfer (AIE + ESIPT)’-assisted photorelease of an anticancer drug by a p<\/em>-hydroxyphenacyl (pHP) phototrigger with real-time monitoring has been demonstrated.<\/p>")">
Authors: Sk. Sheriff Shah and N. D. Pradeep Singh ,Vol: 59 Pages: 247-251Journal: Tetrahedron Letters Year: 2018 Posted: 07 Jul 2019
Pseudohalides are well known to do similar chemistry like halides. Thiocyanate, a pseudohalide acts like halides in many ways. Thiocyanate radicals (
Authors: Krishna Kalyani Behara, Y Rajesh, Yarra Venkatesh, Bhaskar Rao Pinninti, Mahitosh Mandal, N. D. Pradeep SinghVol: 53 Pages: 9470 - 9473Journal: Chem. Commun Year: 2017 Posted: 07 Jul 2019
We report a new strategy, viz.<\/em> cascade photocaging, for protecting diethylamine diazeniumdiolate (O<\/em>2<\/small>-position), a light sensitive molecule. Upon photolysis, the cascade photocage at first releases the light activatable linker (latent fluorophore) O<\/em>2<\/small>-caged diazeniumdiolate, which undergoes spontaneous 1,8-elimination, triggering the release of the diazeniumdiolate anion and the fluorophore.<\/p>")">
Authors: Moumita Gangopadhyay, Rakesh Mengji, Amrita Paul, Yarra Venkatesh, Venugopal Vangala, Avijit Jana, N. D. Pradeep SinghVol: 53 Pages: 9109 - 9112Journal: Chem. Commun Year: 2017 Posted: 07 Jul 2019
A FRET donor–acceptor xanthene–coumarin conjugate has been designed for redox-regulated synergic treatment of photodynamic therapy and chemotherapy with real-time monitoring. The “locked” FRET pair was selectively “unlocked” by biological reducing thiols via<\/em> rupture of a sacrificial disulfide linker. A distinct change in fluorescence color and selective cancer cell toxicity were observed in vitro<\/em>.<\/p>")">
Authors: Sandipan Biswas, Joyjyoti Das, Shrabani Barman, Bhaskara Rao Pinninti, Tapas K. Maiti, and N. D. Pradeep SinghVol: 9 Pages: 28180–28184Journal: ACS Appl. Mater. Interfaces Year: 2017 Posted: 07 Jul 2019
Remedial cancer therapy deals with a large number of theranostic applications. However, systems, so far known, are only capable of single surveillance for both diagnostic and therapeutic modes of action. A nanosystem, which can be localized to the cancer and deliver the chemotherapeutic agent on demand, will provide effective therapeutic activity. Herein, we designed a single component nanoprodrug ANPD-X (Activatable Nano Pro-Drug-X) which indentified the tumor sites by fluorescent color change (signal 1, blue to green fluorescence) using H2O2-mediated oxidation of boronate fluorophore. In the next step, precise spatiotemporal irradiation of light only on identified tumor sites resulted in the release of anticancer drug chlorambucil. The real time information on drug release was achieved by a second fluorescence color change (signal 2, green to blue fluorescence). Thus, nanoprodrug ANPD-X provided overall two-step surveillance in the anticancer drug delivery. Activation of the ANPD-X after addition of H2O2 and drug release upon photoirradiation was investigated in vitro<\/em> by monitoring its fluorescence in the HeLa cell line.<\/p>")">
Authors: Amrita Chaudhuri, Yarra Venkatesh, Krishna Kalyani Behara, and N. D. Pradeep SinghVol: 19 Pages: 1598-1601Journal: Org. Lett. Year: 2017 Posted: 07 Jul 2019
A series of ester conjugates of carboxylic and amino acids were synthesized based on bimane fluorescent photoremovable protecting group (FPRPG). The photorelease of single and dual (same as well as different) carboxylic and amino acids is demonstrated from a single bimane molecule on irradiation with visible light (λ ≥ 410 nm). The detailed mechanistic study of photorelease revealed that the release of two caged acids is simultaneous but in a stepwise pathway.<\/p>")">
Authors: . Laurynas Pukenas, Panida Prompinit, B. Nishitha, Daniel J. Tate, N. D. Pradeep Singh, Richard J. Bushby, Christoph Wälti, and Stephen D. EvansVol: 9 Pages: 18388-18397Journal: ACS Appl. Mater. Interfaces Year: 2017 Posted: 07 Jul 2019
Under a layer of 0.1 M HCl in isopropanol, soft ultraviolet (UV) (365 nm) photolysis of the thiol-on-gold self-assembled monolayer (SAM) derived from the lipoic acid ester of α-hydroxy-1-acetylpyrene results in the expected removal of the acetylpyrene protecting group. When photolyzing through a mask, this can be used to produce a patterned surface and, at a controlled electrochemical potential, it is then possible to selectively and reversibly electrodeposit copper on the photolyzed regions. Rather surprisingly, under these photolysis conditions, there is not only the expected photodeprotection of the ester but also partial removal of the lipoic acid layer which has been formed. In further studies, it is shown that this type of acid-catalyzed photoremoval of SAM layers by soft UV is a rather general phenomenon and results in the partial removal of the thiol-on-gold SAM layers derived from other ω-thiolated carboxylic acids. However, this phenomenon is chain-length dependent. Under conditions in which there is a ∼60% reduction in the thickness of the SAM derived from dithiobutyric acid, the SAM derived from mercaptoundecanoic acid is almost unaffected. The process by which the shorter-chain SAM layers are partially removed is not fully understood because these compounds do not absorb significantly in the 365 nm region of the spectrum! Significantly, this study shows that acid catalysis photolysis of thiol-on-gold SAMs needs to be used with caution.<\/p>")">
Authors: Amrita Paul, Rakesh Mengji, Olive Abraham Chandy, Surajit Nandi, Manoranjan Bera, Avijit Jana, Anakuthil Anoop and N. D. PradeepVol: 15 Pages: 8544–8552Journal: Org. Biomol. Chem. Year: 2017 Posted: 07 Jul 2019
o-Hydroxycinnamate derivatives are well-known phototriggers for fast and direct release of alcohols and amines without proceeding through the cleavage of carbonate or carbamate linkages. Despite these unique features, o-hydroxycinnamates lack extensive applications in biological systems mainly because of their non-fluorescent nature. To overcome this limitation, we have attached a 2-(2’-hydroxyphenyl) benzothiazole (HBT) moiety, capable of rapid excited-state intramolecular proton transfer (ESIPT) to the o-hydroxycinnamate group. The ESIPT effect induced two major advantages to the o-hydroxycinnamate group: (i) large Stokes’ shifted fluorescence (orange colour) properties and (ii) distinct fluorescence colour change upon photorelease. In vitro studies exhibited an image guided, photoregulated release of bioactive molecules by the o-hydroxycinnamate–benzothiazole–methyl salicylate conjugate and real-time monitoring of the release action.<\/p>")">
Authors: arra Venkatesh, Surajit Nandi, Maniklal Shee, Biswajit Saha, Anakuthil Anoop and N. D. Pradeep SinghVol: Pages: 6121-6130Journal: Eur. J. Org. Chem. Year: 2017 Posted: 07 Jul 2019
In this paper, we present fluorescent photoremovable protecting groups (FPRPG) based on bis-acetyl carbazole for the release of two different functional groups such as carboxylic acids, alcohols, thiols, and amines in a sequential fashion. Dualarm caged bis-acetyl carbazoles with different combinations of two unlike functional groups were synthesized. Photophysical studies showed that caged bis-acetyl carbazoles are blue fluorescent and their emission properties are sensitive to the environment. Sequential photorelease of two different functional groups by bis-acetyl carbazole was analyzed by HPLC, UV and emission spectroscopy. The mechanism of the dual release by bis-acetyl carbazole was investigated and supported by TD-DFT calculations. To demonstrate the applicability of the dual release ability of bis-acetyl carbazole FPRPG, we synthesized a drug delivery system (DDS) in which one arm of bis-acetyl carbazole is linked to the carboxylic functional group of chlorambucil (CBL) and the other arm is attached to the hydroxyl group of ferulic acid ethyl ester (FAEE). In vitro studies showed that our DDS presents excellent properties such as photoregulated dual drug delivery, cellular uptake, and biocompatibility.<\/p>")">
Authors: Krishna Kalyani Behara, Y Rajesh, Amrita Chaudhuri, Sandipan Biswas, Mahitosh Mandal, N. D. Pradeep SinghVol: 2 Pages: 4033-4038Journal: Chemistry Select Year: 2017 Posted: 06 Jul 2019
Development of new photoresponsive drug delivery systems for combination chemotherapy is sought?after due to their precise spatio?temporal control over delivering drugs. Further, design of wavelength dependent drug delivery systems with each individual drug release being “one on one” triggered by light of different activating wavelengths, is an emerging topic for its high selective control over the release of individual drug. Herein we are reporting design of a new wavelength dependent photoresponsive dual drug delivery system i. e. nitric oxide donor linked coumarin chlorambucil conjugate (NOD?Cou?Cbl) for sequentially delivering anticancer agents with orthogonal mode of actions. NOD?Cou?Cbl has shown a sequential release of nitric oxide (NO) followed by chlorambucil under step wise irradiation with visible light and UV light, respectively. We have also studied in?vitro<\/em> cytotoxicity activity and real time bioimaging property of dual DDS on MDA?MB?231 cell line.<\/p>")">
Authors: Shrabani Barman, Joyjyoti Das, Sandipan Biswas, T. K. Maiti, and N. D. Pradeep SinghVol: 5 Pages: 3940-3944Journal: Journal of Materials Chemistry B Year: 2017 Posted: 06 Jul 2019
In spite of inventing several anticancer agents the clinical payoff still remains unsatisfactory because of their severe host toxicity due to their nonspecific biodistribution in the body. To achieve high efficiency in anti-cancer drug delivery, thus, we designed and developed a single component photoresponsive drug delivery system, a fusion of two platforms spiropyran and coumarin, which synchronizes two controlling factors: first, the lower pH of cancer tissue, which acts as an internal control and leads to the ring opening of spiropyran resulting in a distinct colour change and fluorescence activation of coumarin; and second, the release of the anti-tumor drug by the externally controlled light. Highly fluorescent nature and promising biocompatibility make the SP–Cou–Cbl<\/strong> system suitable for cell imaging and in vitro<\/em> studies.<\/p>")">
Authors: S. Karthik, Avijit Jana, M. Selvakumar, Yarra Venkatesh, Amrita Paul, Sk. Sheriff Shah, and N. D. Pradeep SinghVol: 5 Pages: 1734-1741Journal: Journal of Materials Chemistry B Year: 2017 Posted: 06 Jul 2019
Highly sensitive hypoxia (H2<\/small>O2<\/small>)-activated photoresponsive polymeric nanoparticles for cocktail delivery of anticancer drugs doxorubicin (Dox) and chlorambucil (Cbl) were developed. The photoresponsive polymer conjugate was constructed by ring-opening polymerization (ROP) of caprolactone (as the tail) with 7-hydroxycoumarin chlorambucil (as the head). During nanoprecipitation, the polycaprolactone chain wrapped around the hydrophobic core (coumarin chlorambucil) to form a “shell”. Interestingly, the polycaprolactone-tagged coumarin-chlorambucil (PCL-CC) NPs provided sufficient space for co-encapsulation of another hydrophobic anticancer drug Dox with a loading efficiency of 13 wt%. The controlled release of Dox and Cbl from Dox–PCL-CC NPs was investigated under three different conditions: (i) in the presence of H2<\/small>O2<\/small> (tumor microenvironment), (ii) photoirradiation using UV light of ≥365 nm for 60 min, and (iii) photoirradiation using UV light of ≥365 nm for 15 min in the presence of H2<\/small>O2<\/small>. Results showed that photoirradiation in the presence of H2<\/small>O2<\/small> results in generation of reactive oxygen species (HOO–, OH–), which assist hydrolysis of the ester group in the polymeric backbone of Dox–PCL-CC NPs and UV irradiation leads to cleavage of the coumarin-chlorambucil ester linkage, leading to burst release of Dox and Cbl. The drug release profile from the NPs under three different conditions was monitored by different instrumental techniques, e.g.<\/em> emission spectroscopy, MALDI-Tof mass spectrometry, DLS and HPLC analysis. In vitro<\/em> biological studies revealed that the present system can efficiently deliver the cocktail anticancer drugs with full control over release into the tumor cells by means of H2<\/small>O2<\/small> and light activation.<\/p>")">
Authors: Shrabani Barman, Sourav K. Mukhopadhyay, Sandipan Biswas, Surajit Nandi, Moumita Gangopadhyay, Satyahari Dey, Anakuthil Anoop, N. D. Pradeep SinghVol: 55 Pages: 1-6Journal: Angew. Chem. Intd. Ed. Year: 2016 Posted: 06 Jul 2019
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Authors: Yarra Venkatesh, Y. Rajesh, S. Karthik, A C Chetan, Mahitosh Mandal, Avijit Jana, and N. D. Pradeep SinghVol: 81 Pages: 11168-11175Journal: J. Org. Chem Year: 2016 Posted: 06 Jul 2019
A new fluorescent photoremovable protecting group (FPRPG) based on acetylcarbazole framework has been explored for the first time release of single and dual (similar or different) substrates from single chromophore. Mechanistic studies of the photorelease process revealed that photorelease of two (similar or different) substrates from acetyl carbazole proceeds via a stepwise pathway. Further, we constructed photoresponsive dual drug delivery system (DDS) to release two different anticancer drugs (caffeic acid and chlorambucil, 1 equiv each). In vitro study reveals that our DDS exhibit excellent properties like biocompatibility, cellular uptake, and photoregulated dual drug release.<\/p>")">
hree Arm, Biotin-tagged Carbazole-Dicyanovinyl-Chlorambucil Conjugate: Simultaneous Tumor Targetting, Sensing and Photoresponsive Anticancer Drug Delivery
Authors: Yarra Venkatesh, S. Karthik, Y. Rajesh, Mahitosh Mandal, Avijit Jana, and N. D. Pradeep SinghVol: 11 Pages: 3482-3486Journal: Yarra Venkatesh, S. Karthik, Y. Rajesh, Mahitosh Mandal, Avijit Jana, and N. D. Pradeep Singh Year: 2016 Posted: 06 Jul 2019
Authors: Yarra Venkatesh, Y. Rajesh, S. Karthik, A C Chetan, Mahitosh Mandal, Avijit Jana, and N. D. Pradeep SinghVol: 81 Pages: 11168-11175Journal: J. Org. Chem. Year: 2016 Posted: 03 Jul 2019
A new fluorescent photoremovable protecting group (FPRPG) based on acetylcarbazole framework has been explored for the first time release of single and dual (similar or different) substrates from single chromophore. Mechanistic studies of the photorelease process revealed that photorelease of two (similar or different) substrates from acetyl carbazole proceeds via a stepwise pathway. Further, we constructed photoresponsive dual drug delivery system (DDS) to release two different anticancer drugs (caffeic acid and chlorambucil, 1 equiv each). In vitro study reveals that our DDS exhibit excellent properties like biocompatibility, cellular uptake, and photoregulated dual drug release.<\/p>")">
Authors: Yarra Venkatesh, S. Karthik, Y. Rajesh, Mahitosh Mandal, Avijit Jana, and N. D. Pradeep SinghVol: 11 Pages: 3482 – 3486Journal: Chem. Asian J. Year: 2016 Posted: 03 Jul 2019
The design, synthesis, and in vitro biological studies of a biotin–carbazole–dicyanovinyl–chlorambucil conjugate (Bio-CBZ-DCV-CBL; 6) are reported. This conjugate (6) is a multifunctional single-molecule appliance composed of a thiol-sensor DCV functionality, a CBZ-derived phototrigger as well as fluorescent reporter, and CBL as the anticancer drug, and Bio as the cancer-targeting ligand. In conjugate 6, the DCV bond undergoes a thiol– ene click reaction at pH<7 with intracellular thiols, thereby shutting down internal charge transfer between the donor CBZ and acceptor DCV units, resulting in a change of the fluorescence color from green to blue, and thereby, sensing the tumor microenvironment. Subsequent photoirradiation results in release of the anticancer drug CBL in a controlled manner.<\/p>")">
Authors: Sandipan Biswas, Joyjyoti Das, Shrabani Barman, Sk. Sheriff Shah, Moumita Gangopadhyay,Tapas K. Maity, N. D. Pradeep SinghVol: 244 Pages: 327-333Journal: Sensors & Actuators: B. Chemical. Year: 2016 Posted: 03 Jul 2019
The early stage detection, diagnosis and treatment of prostate cancer are life-saving events in patients housing potentially invasive disease. The healthy human prostate accumulates the maximum amount of zinc compared to any soft tissue in the body. But in the contrary, an inability of cancer cells to accumulate zinc has been found with the development of malignancy resulting in a dramatic reduction in the zinc content of prostate tissue. In this current study, we designed and developed a dipicolylamine-coumarin-chlorambucil (Dpa-Cm-Cmbl) based system which can act as a sensor (for the prostatic zinc i.e. diagnosis) as well as photoresponsive drug delivery system (treatment). We demonstrated that Dpa-Cm-Cmbl being a single component system, first guided us to locate the diseased area by using cellular zinc concentration as a biomarker and in the next there was on-demand release of anticancer drug chlorambucil by employing the external stimulus light. In-vitro studies showed that Dpa-Cm-Cmbl presents excellent properties like detection of cancerous regions in the prostate, photoregulated drug delivery in controlled manner, biocompatibility and all together an efficient chemotherapy.<\/p>")">
Authors: Moumita Gangopadhyay, Avijit Jana, Y. Rajesh, Manoranjan Bera, Sandipan Biswas, Nilanjana Chowdhury, Yanli Zhao, Mahitosh Mandal, and N. D. Pradeep SinghVol: 1 Pages: 6523 – 6531Journal: ChemistrySelect Year: 2016 Posted: 03 Jul 2019
Photodynamic therapy (PDT) is a non?invasive cancer treatment. For target?specific PDT, targeting “overexpression” of some specific cellular markers will be highly beneficial. As CuII content is higher in cancer cells than in normal cells, selective binding with CuII can be the most effective mode for intracellular heterogeneity?responsive targeted PDT. Thus, a photosensitizer showing competent PDT activity only after CuII chelation is important for tumor?targeted PDT. Herein, we report a new ratiometric fluorescent chemosensor based on anthracene?N?phenylethylenediamine nanoparticles (ANT?pen NPs), which showed fluorescence color change from green to red upon CuII chelation. Only the CuII?bound state showed selective PDT activity; hence, this color change was used for real?time monitoring of targeted PDT. Cellular images in cancerous HeLa and non?cancerous NIH 3T3 cell lines showed the change in fluorescence of ANT?pen NPs on selective binding with CuII in HeLa cells only. MTT assay in both cells suggested massive cell destruction by ANT?pen?CuII NPs only in HeLa cells upon visible light exposure, whereas NPs remained non?toxic to NIH 3T3 cells.<\/p>")">
Authors: Ramalingam Dineshkumar, Amrita Paul, Moumita Gangopadhyay, N. D. Pradeep Singh, and Ramkrishna SenVol: 5 Pages: 852?861Journal: ACS Sustainable Chem. Eng. Year: 2016 Posted: 03 Jul 2019
One of the major technological challenges in developing a microalgal biorefinery is to minimize the fossil energy inputs, particularly in two important downstream unit operations, cell harvesting and disruption. Hence, this study involved synthesizing and applying biopolymer nanocomposite to achieve concomitant biomass harvesting, cell disruption, and nanocomposite recovery by exploiting its cationic, photocatalytic, and magnetic properties respectively, in an integrated and optimized process chain. Accordingly, dual-functionalized chitosan-TiO2 conjugated particles (CTC) and trifunctionalized magnetic nanocomposites (MNCs) namely, chitosan coated core−shell structures of Fe3O4−TiO2, were prepared and characterized. The harvesting efficiency of >98% was achieved at the optimal dosages of chitosan, CTC and MNCs of 0.11, 0.09, and 0.07 g g−1 Chlorella minutissima biomass, respectively. TiO2 driven photocatalysis could effectively disrupt harvested wet-biomass, when exposed to UV irradiation in the presence of either CTC or MNCs for 2 h, and when subjected to visible light with only MNCs for 3 h. Photocatalytic cell disruption helped recover 96−97% of the intracellular lutein and lipid, when compared to ultrasonication as control. Subsequently, the MNCs were separated from residual biomass by physicochemical treatment, resulting in over 98% detachment efficiency for reuse in the downstream process chain. To the best of our knowledge, this integrated green process is novel, in terms of meeting a contemporary technological challenge in downstream processing of microalgal biomass, and this research outcome may inspire the development of sustainable microalgal biorefinery for the production of lutein and biodiesel<\/p>")">
Authors: Moumita Gangopadhyay, Sourav K. Mukhopadhyay, Sree Gayathri, Sandipan Biswas, Shrabani Barman, Satyahari Dey and N. D. Pradeep SinghVol: 4 Pages: 1862--1868Journal: J. Mater. Chem. B Year: 2016 Posted: 03 Jul 2019
Nanocarrier-mediated photodynamic therapy (PDT) is an effective tool for anti-tumour treatment due to the targeted and image-guided delivery of photosensitizers (PSs) to diseased tissues. These nanocarriers range from inorganic, ceramic, polymeric to biological nanoparticles (NPs). Such PS-grafted bicomponent nanocarriers have limitations like (i) difficulty in surface modification, (ii) lower loading percentages of the therapeutic agent, (iii) unstable physical encapsulation, etc. By any means, if we can prepare PSs directly as NPs then we can surpass the above drawbacks. Hence, we synthesised new two-photon fluorene–functionalised morpholine (Fluo–Mor)-based organic NPs that showed strong fluorescence and profound photodynamic therapy (PDT) activity only in acidic medium. Such a pH-responsive appearance of fluorescence enables Fluo–Mor NPs for the real time monitoring of photodynamic therapeutic activity selectively in low-pH organelles viz. lysosome. Cytotoxicity of Fluo–Mor NPs was monitored using time-dependent and dosedependent cancer cell viability assay and confocal imaging.<\/p>")">
Authors: Amrita Paul, Avijit Jana, S. Karthik, Manoranjan Bera, Yanli Zhao and N. D. Pradeep SinghVol: 4 Pages: 521-528Journal: J. Mater. Chem. B Year: 2016 Posted: 03 Jul 2019
Recently, photoresponsive nanoparticles have been widely used to develop drug delivery systems (DDSs) wherein light is used as an external stimulus to trigger drug release in a spatially and temporally controlled fashion. Real time monitoring DDSs are also gaining much interest due to their capability of monitoring drug release in situ. In this context we designed a new photoresponsive real time monitoring nanoparticle based on photoluminescent silicon quantum dots (SiQDs) using the o-nitrobenzyl (ONB) derivative as a phototrigger for the controlled release of anticancer drug chlorambucil (Cbl). The strong fluorescence of SiQDs was initially quenched by ONB. Upon irradiation ONB triggered the release of the drug switching on the fluorescence of SiQDs to monitor the drug release. We reported a new and simple strategy to synthesise amine functionalised silicon quantum dots and covalently conjugated phototrigger ONB with caged anticancer drug Cbl onto it. Newly designed photoresponsive theranostic ONBCbl–SiQDs performed three important functions: (i) nanocarriers for drug delivery, (ii) controlled drug release under both one photon and two-photon excitation, and (iii) photoswitchable fluorescent nanoparticles for real-time monitoring of drug release based on the photoinduced electron transfer (PET) process. In vitro biological studies revealed the efficient cellular internalisation and cancer cell destruction ability of ONBCbl–SiQDs upon photoirradiation. ONBCbl–SiQDs exhibit a successful example of combining multiple functions into a single system for drug delivery systems.<\/p>")">
Authors: Sanghamitra Atta, Amrita Paul, Rakesh Banerjee, Manoranjan Bera, Mohammed Ikbal, Dibakar Dhara and N. D. Pradeep SinghVol: 5 Pages: 99968-99975Journal: RSC Adv. Year: 2015 Posted: 03 Jul 2019
We report an excellent photoresponsive controlled release formulation based on a coumarin copolymer for pesticide 2,4-D. In the present work, acrylate and polyethylene glycol (PEG) based coumarin photoresponsive polymers were synthesised. The newly synthesised coumarin based polymers exhibited dual functionalities, namely as “fluorophores” and “phototriggers” for the controlled release of pesticide 2,4-D. The fluorescence properties of coumarin based polymers helped us to monitor the release of 2,4-D from the polymeric formulation. Release of the pesticide by coumarin based polymers was achieved on exposure to UV light. TGA results indicated that the coumarin polymer encapsulated pesticide has a good thermal stability compared to the free pesticide 2,4-D. A further leaching experiment also showed that the polymer encapsulated pesticide leaches slowly compared to the free pesticide 2,4-D. Bioassay studies in a plant suggest that the coumarin polymer encapsulated pesticide efficiently delivered 2,4-D inside the plant tissues (pumpkin plant Cucurbita maxima<\/em>) improving its herbicidal activity. Our results indicated that use of a fluorescent coumarin polymer based delivery device for controlled release of pesticide by light holds great interest for field application.<\/p>")">
Authors: Sanghamitra Atta, Manoranjan Bera, Tirthartha Chattopadhyay, Amrita Paul, Mohammed Ikbal, Mrinal K. Maiti, N. D. Pradeep SinghVol: 5 Pages: 86990-86996Journal: RSC Adv. Year: 2015 Posted: 03 Jul 2019
In recent times, nano-pesticide formulations have gained great popularity since they enable effective usage of smaller quantities of the pesticides without creating much damage to the environment. The benefits of a nano-pesticide formulation can be further expanded by adding to its arsenal both tracking ability and precise control over the pesticide release. Recently, fluorescent photoresponsive nanocarriers have gained considerable momentum in the field of drug delivery since they can act as both a “fluorophore” for cell luminescence imaging and a “phototrigger” for regulated drug release by external light stimuli. Hence, we report for the first time a nano-pesticide formulation based on fluorescent photoresponsive organic nanoparticles of perylene-3-ylmethanol for regulated release of pesticide 2,4- dichlorophenoxyacetic acid (2,4-D). Further, the fluorescent nature of the photoresponsive organic nanoparticles was used to study the morphological changes induced by 2,4-D inside the plant system using confocal imaging studies. Additionally, the fluorescent colour change by photoresponsive organic nanoparticles before and after photorelease was exploited for real time monitoring of 2,4-D release inside the plants. Bioassay experiments revealed that nano-pesticide, Pe-2,4-D efficiently delivered 2,4-D inside the plant tissues improving its herbicidal activity. Such photoresponsive multifunctional nanocarriers with good fluorescence, cellular uptake property and efficient photoregulated release ability will be of great benefit in the construction of nano-pesticide formulations.<\/p>")">
Authors: Moumita Gangopadhyay, Tanya Singh, Krishna Kalyani Behara, S. Karwa,S. K. Ghosh and N. D. Pradeep SinghVol: 14 Pages: 1329Journal: Photochem. Photobiol. Sci. Year: 2015 Posted: 03 Jul 2019
Single component fluorescent organic polymeric nanoparticles (NPs) have been synthesized based on a star shaped 4-arm PEG containing coumarin chromophore for the concomitant employment of photodynamic therapy (PDT) and chemotherapy synergistically to wipe out tumour cells with a high efficiency. Polymeric NPs are emerging as the most promising nanoparticulates in the area of drug delivery systems due to their ability to overcome the disadvantages like premature and imprecise control over the drug release, lack of loading capacity etc. Among polymeric NPs, star shaped branched polymers have attracted great attention mainly due to their multiple functionalization properties. Hence, herein we have made use of a multi-arm PEG, functionalized with a targeting unit biotin and a coumarin fluorophore for site-specific and image guided synergic treatment of cancer cells. The anticancer drug chlorambucil is released by the coumarin chromophore in a photocontrolled manner. In addition to that, coumarin also generated singlet oxygen upon irradiation with UV\/vis light (≥365 nm) with a moderate quantum yield of ∼0.37. In vitro application of thus prepared organic polymeric nanoparticles (PEG–Bio–Cou–Cbl) in the HeLa cell line shows a reduction of cell viability by up to ∼5% in the case of a combined treatment of PDT and chemotherapy whereas analogous organic polymeric NPs without the chemotherapeutic drug (PEG– Bio–Cou) result in ∼49% cell viability by means of PDT process only.<\/p>")">
Authors: Shrabani Barman, Sourav K. Mukhopadhyay, Moumita Gangopadhyay,Sandipan Biswas, Satyahari Dey and N. D. Pradeep SinghVol: 3 Pages: 3490Journal: J. Mater. Chem. B Year: 2015 Posted: 02 Jul 2019
We have developed an ESIPT based drug delivery system (DDS), Cou–Benz–Cbl conjugate, by incorporating a benzothiazole group at the 8th position of the 7-hydroxy-coumarin moiety for pH sensitive fluorescence properties and photocontrolled release of the anticancer drug chlorambucil. The Cou–Benz–Cbl conjugate exhibited unique photophysical properties like good absorbance at around 350 nm, a large Stokes shift (B151 nm) and pH sensitive fluorescence properties. The pH sensitive fluorescence properties of the Cou–Benz–Cbl conjugate can be ascribed to an ESIPT turn ‘‘on and off’’ mechanism. At physiological pH, the ESIPT gets turned ‘‘off’’ and a blue fluorescence of the coumarin moiety was observed, but at acidic pH, the ESIPT gets turned ‘‘on’’ and a green fluorescence was noted. Photolysis of the Cou–Benz–Cbl conjugate using UV light of wavelength Z365 nm resulted in the efficient release of the anticancer drug chlorambucil. Cellular uptake studies revealed that the Cou–Benz–Cbl conjugate was easily internalized inside the cancer cells. Further, an MTT assay showed that the Cou–Benz–Cbl conjugate has a good biocompatibility and low cytotoxicity towards the MDA-MB-231 cell line, whereas upon exposure to UV light, the Cou–Benz–Cbl conjugate exhibited enhanced cytotoxicity compared to the free drug due to the effective release of the anticancer drug chlorambucil inside the cancer cell.<\/p>")">
Authors: Sk. Sheriff Shah, S. Karthik and N. D. Pradeep SinghVol: 5 Pages: 45416Journal: RSC Adv. Year: 2015 Posted: 02 Jul 2019
A highly efficient one-pot strategy has been developed for the synthesis of disulfide in the presence of air under the irradiation of Vis\/ NIR light. Copper hydroxyphosphate (CHP) Cu2(OH)PO4, has been used as a Vis\/NIR active photocatalyst. Disulfide forms on the surface of the catalyst by a radical mechanism. The protocol is useful for solvent free disulfide synthesis from a variety of thiols.<\/p>")">
Authors: Moumita Ganguly, Sourav K. Mukhopadhyay, Karthik S, Sharabani Barman and Pradeep N.D. SinghVol: 6 Pages: 769–777Journal: Med.Chem.Commun. Year: 2015 Posted: 02 Jul 2019
Coupling of photodynamic therapy (PDT) with chemotherapy is an emerging treatment modality because of its ability to improve the antitumor effect and reduce the toxicity of the anticancer agents. Metallic NPs, silica NPs and carbon nanotubes have become rising stars as drug carriers for both photosensitizers and chemotherapeutic agents. But to date there are only a few reports using the aforesaid NPs as a platform for PDT combined with chemotherapy. Hence, we have developed a targeted metallic single nanoparticle system for the amalgamation of PDT with chemotherapy. The NPs for combination therapy have been constructed using two main ingredients: folic acid decorated TiO2 NPs and coumarin chromophore. The newly synthesized coumarin chromophore performed three important roles: (i) being a fluorophore for cell imaging, (ii) photosensitizer for PDT and (iii) a phototrigger for regulated anticancer drug release. Furthermore, folic acid decorated TiO2 NPs help with internalization of the drug to inside the cancer cells. In vitro biological studies reveal that this targeted combination treatment results in an enhanced tumor accumulation of TiO2 nanoparticles, significant inhibition of tumor cell proliferation and increased induction of apoptosis. Such metallic photoresponsive NPs that are benign to the physiological system, permeate easily into cells and exhibit high therapeutic efficacy, will have significant prospects for use against drug-resistant tumors.<\/p>")">
Authors: Karthik S, Prashanth Kumar B N, Moumita Gangopadhyay, Mandal Mahitosh,Pradeep N.D. SinghVol: 3 Pages: 728-732Journal: J. Mater. Chem. B Year: 2015 Posted: 02 Jul 2019
We have developed a new targeted image-guided photoresponsive drug delivery system (DDS) based on a dual locking strategy. Excitation of the DDS by fluorescent light results in the first unlocking and activation of the drug, and allows real-time monitoring of the prodrug. Extended irradiation results in a second unlocking, giving drug release within cancer cells<\/p>")">
Authors: Sridhar Rajam, Abhijit V. Jadhav, Qian Li, Sujan K. Sarkar, Pradeep N. D. Singh, Ahleah Rohr, Tamara C. S. Pace, Rui Li, Jeanette A. Krause, Cornelia Bohne, Bruce S. Ault, and Anna D. GudmundsdottirVol: 79 (19) Pages: 9325–9334Journal: J. Org. Chem. Year: 2014 Posted: 02 Jul 2019
Photolysis of vinylazide 1<\/strong>, which has a built-in acetophenone triplet sensitizer, in argon-saturated toluene results in azirine 2<\/strong>, whereas irradiation in oxygen-saturated toluene yields cyanide derivatives 3<\/strong> and 4<\/strong>. Laser flash photolysis of azide 1<\/strong> in argon-saturated acetonitrile shows formation of vinylnitrene 1c<\/strong>, which has a λmax at ∼300 nm and a lifetime of ∼1 ms. Vinylnitrene 1c<\/strong> is formed with a rate constant of 4.25 × 105 s–1 from triplet 1,2-biradical 1b<\/strong>. Laser flash photolysis of 1<\/strong> in oxygen-saturated acetonitrile results in 1c-O<\/strong> (λmax = 430 nm, τ ≈ 420 μs acetonitrile). Density functional theory (DFT) calculations were used to aid in the characterization of the intermediates formed upon irradiation of azide 1<\/strong> and to validate the proposed mechanism for its photoreactivity.<\/p>")">
Authors: S. Karthik, Avijit Jana, Biswajit Saha, B. Krishna Kalyani, Sudip Kumar Ghosh, Yanli Zhao and N. D. Pradeep SinghVol: 3 Pages: 728-732Journal: J. Mater. Chem. B Year: 2014 Posted: 02 Jul 2019
We developed excellent charge reversal photoresponsive nanoparticles for targeted delivery of the anticancer drug chlorambucil. The charge reversal photoresponsive nanoparticles were constructed using two main ingredients, namely folic acid decorated mesoporous silica and quinoline chromophore. The newly synthesized quinoline chromophore performed three important roles, i.e., (i) fluorescent chromophore for cell imaging, (ii) phototrigger for regulated release of anticancer drug, and (iii) charge reversal based on its zeta potential for nuclear localization. Furthermore, folic acid decorated mesoporous silica facilitated active internalization of the drug inside the cancer cells. In vitro biological studies reveal that our photoresponsive DDS could deliver the anticancer drug chlorambucil into the tumor cells, killing the cancer cells by both one photon ($365 nm) and two photon (675 nm) irradiation<\/p>")">
Authors: S. Dasgupta, S. Atta, N. D. Pradeep Singh, D. Deb, W. S. Kassel, M. BhattacharjeeVol: 30 Pages: 5125-5134Journal: Eur.J. Inorg. Chem. Year: 2014 Posted: 02 Jul 2019
A new biogenic potentially tetradentate ligand, L-2-(3,5-ditert-butyl-2-hydroxybenzylamino)succinic acid, has been synthesized. Upon reaction with FeCl3 in the presence of triethylamine, it afforded the complex [Et3NH][Fe(HL)2] (1). The complex was structurally characterized and was used forhomogeneous photocatalytic degradation of methylene blue (MB), malachite green (MG), crystal violet (CV) and rhodamine B (RhB) under visible-light irradiation in aqueous solution in the presence of H2O2.<\/p>")">
Authors: R. K. Sahoo, S. Atta, N.D.P Singh, C. JacobVol: 25 Pages: 279–285Journal: Materials Science in Semiconductor Processing Year: 2014 Posted: 28 Jun 2019
A layer of a coumarin derivative\\multiwall carbon nanotube (MWCNT) composite wassandwiched between an indium tin oxide (ITO) layer and a top metal electrode. This layeracted as the active hetero-junction (middle hetero-junction) in a triple hetero-junctionorganic solar cell. The composition of the organic material in the middle hetero-junctioncomponent, second from the ITO layer, was varied, keeping the weight percentage of theMWCNTs constant, to investigate the photovoltaic properties of the cell. The choice ofamino-coumarin and its derivatives were dictated by the need for a high efficiency organicup-converter. Amino-coumarin is a two photon absorbing organic donor whereas CNTsare acceptors and ballistic charge transport media. For those reasons, amino-coumarin-CNT composite materials were selected as a photo active layer to will absorb the sub-bandphotons effectively. Additionally, the radial self-assembling of the CNTs inside the organicmatrix (during synthesis) enhances the photovoltaic characteristics of the material. Thephoto induced charge transport mechanism between the MWCNTs and organics wasanalyzed using photo luminescence (PL) measurements. By the use of 15 wt% of CNTs withthe organics, more than 90% of the PL signal was quenched, indicating an ultrafasttransport mechanism between the donor and acceptor materials<\/p>")">
Authors: Shrabani Barman , Sourav K. Mukhopadhyay , Krishna Kalyani Behara , Satyahari Dey , and N. D. Pradeep SinghVol: 6 Pages: 7045?7054Journal: ACS Applied Materials & Interfaces Year: 2014 Posted: 28 Jun 2019
Photoresponsive 1-acetylpyrene−salicylic acid (AcPy-SA) nanoparticles (NPs) were developed for the regulated release of a natural antimicrobial compound, salicylic acid. The strong fluorescent properties of AcPy-SA NPs have been extensively used for potential in vitro cell imaging. The phototrigger capability of our newly prepared AcPy-SA NPs was utilized for the efficient release of an antimicrobial compound, salicylic acid. The photoregulated drug release of AcPy-SA NPs has been shown by the subsequent switching off and on of a visible-light source. In vitro biological studies reveal that AcPy-SA NPs of ∼68 nm size deliver the antimicrobial drug salicylic acid into the bacteria cells (Pseudomonas aeruginosa) and efficiently kill the cells upon exposure to visible light (≥410 nm). Such photoresponsive fluorescent organic NPs will be highly beneficial for targeted and regulated antimicrobial drug release because of their biocompatible nature, efficient cellular uptake, and light-induced drug release ability.<\/p>")">
Authors: Mohammed Ikbal, Rakesh Banerjee, Shrabani Barman, Sanghamitra Atta, DibakarDhara, N. D. Pradeep SinghVol: 2 Pages: 4622–4630Journal: Journal of Materials Chemistry C Year: 2014 Posted: 28 Jun 2019
A newsworthy class of carboxylate and sulfonate esters of 1-acetylferroceneoxime has been demonstrated as non-ionic photoacid generators (PAGs). PAGs based on 1-acetylferroceneoxime were synthesized in good yields by simple treatment of 1-acetylferroceneoxime with various carboxylic and sulfonyl chlorides. Newly developed PAGs of 1-acetylferroceneoxime showed good absorbance >350 nm. On irradiation using UV light ($365 nm), carboxylates and sulfonates of 1-acetyl ferroceneoxime in aqueous acetonitrile solvent underwent efficient homolytic cleavage of N–O bond, resulting in the generation of carboxylic and sulphonic acids, respectively, with high chemical and good quantum yields. Further, we demonstrated the application of our newly developed 1-acetylferroceneoxime-based PAGs for gelation of biopolymer alginate on UV irradiation. More interestingly, we synthesized a ferroceneoxime bound photoresponsive polymer, 1-acetylferroceneoxime-polycaprolactone (AFO-PCL), and demonstrated its controlled surface wettability and generation of patterned surfaces.<\/p>")">
Authors: Mohammed Ikbal,Biswajit Saha,Sharabani Barman,Sanghamitra Atta,Debranjan Banerjee,Sudip Ghosh, N.D.Pradeep SinghVol: 12 Pages: 3459–3469Journal: Organic & Biomolecular Chemistry Year: 2014 Posted: 28 Jun 2019
A newsworthy class of carboxylate esters based on the (benzo[a]acridin-12-yl)methyl (BAM) chromophore has been shown to perform dual functions as a “pH sensitive fluorescent probe” and a “phototrigger” for acids. The photophysical properties of all the BAM ester conjugates were investigated and found to be highly sensitive to solvent polarity, H-bonding capability and pH of the environment. On irradiation using UV light (≥410 nm), BAM ester conjugates underwent heterolytic cleavage of C–O bonds resulting in efficient release of carboxylic and amino acids. Interestingly, the newly synthesized BAM chromophore was also explored for the construction of a drug delivery system (DDS). In the current DDS, the BAM chromophore plays two important roles: (i) a “fluorophore” for cell imaging and (ii) a “phototrigger” for the drug release. In vitro biological studies revealed that the newly developed BAM based DDS has a good biocompatibility, cellular uptake properties and efficient photoregulated anticancer drug release ability.<\/p>")">
Authors: Nilanjana Chowdhury, Moumita Gangopadhyay, S. Karthik, Mithu Baidya, S.K. Ghosh,N.D. Pradeep SinghVol: 130 Pages: 188–198Journal: Journal of Photochemistry and Photobiology B: Biology Year: 2014 Posted: 28 Jun 2019
Novel fluorescent quinoxaline and quinoline hydroperoxides were shown to perform dual role as bothfluorophores for cell imaging and photoinduced DNA cleaving agents. Photophysical studies of newlysynthesized quinoxaline and quinoline hydroperoxides showed that they all exhibited moderate to goodfluorescence. Photolysis of quinoxaline and quinoline hydroperoxides in acetonitrile using UV light above350 nm resulted in the formation of corresponding ester compoundsviac-hydrogen abstraction byexcited carbonyl chromophore. Single strand DNA cleavage was achieved on irradiation of newly synthe-sized hydroperoxides by UV light (P350 nm). Both hydroxyl radicals and singlet oxygen were identifiedas reactive oxygen species (ROS) responsible for the DNA cleavage. Further, we showed quinoline hydro-peroxide binds to ct-DNAviaintercalative mode. In vitro biological studies revealed that quinoline hydro-peroxide has good biocompatibility, cellular uptake property and cell imaging ability. Finally, we showedthat quinoline hydroperoxide can permeate into cells efficiently and may cause cytotoxicity upon irradi-ation by UV light.<\/p>")">
Photoresponsive polymer based on coumarin moiety for the controlled release of pesticide 2,4-D
Authors: Sanghamitra Atta, Rakesh Banerjee, Mohammed Ikbal, Dibakar Dhara, N. D. Pradeep SinghJournal: Patent : granted (Ref : 867/Kol/2013 ) Year: 2013 Posted: 28 Jun 2019
Nano-pesticide formulation based on fluorecsent organic photoresponsive nanoperticles: for controlled release of 2,4-D and real time monitoring of morphological changes induced by 2,4-D in plant system
Authors: Sanghamitra Atta, Tirthartha Chattopadhyay, Mohammed Ikbal, Mrinal, K. Maiti, N. D. Pradeep SinghJournal: Patent : granted (Ref : 555/Kol/2013 ) Year: 2013 Posted: 28 Jun 2019
Authors: Avijit Jana, Biswajit Saha, Deb Ranjan Banerjee, Sudip Kumar Ghosh, Kim Truc Nguyen, Xing Ma , Qu Qiuyud Yanli Zhao and N. D. Pradeep SinghVol: 24(11) Pages: 1828?1839Journal: Bioconjugate Chemistry Year: 2013 Posted: 28 Jun 2019
We report for the first time an organic nanoparticle based nuclear-targeted photoresponsive drug delivery system (DDS) for regulated anticancer drug release. Acridin-9- methanol fluorescent organic nanoparticles used in this DDS performed three important roles: (i) ″nuclear-targeted nanocarrier″ for drug delivery, (ii) ″phototrigger″ for regulated drug release, and (iii) fluorescent chromophore for cell imaging. In vitro biological studies reveal acridin-9-methanol nanoparticles of ∼60 nm size to be very efficient in delivering the anticancer drug chlorambucil into the target nucleus, killing the cancer cells upon irradiation. Such targeted organic nanoparticles with good biocompatibility, cellular uptake property, and efficient photoregulated drug release ability will be of great benefit in the field of targeted intracellular controlled drug release.<\/p>")">
Authors: S. Karthik, Biswajit Saha, Sudip Kumar Ghosh and N. D. Pradeep SinghVol: 49 Pages: 10471--10473Journal: ChemComm Year: 2013 Posted: 28 Jun 2019
A photoresponsive nano drug delivery system (DDS) was constructed using two new ingredients: fluorescent carbon dots and a quinoline based phototrigger. The strong fluorescent properties of carbon dots have been explored for in vitro cellular imaging application, and the phototrigger ability of quinoline was exploited for efficient anticancer drug release using both one-photon and two-photon excitation.<\/p>")">
Authors: S. Karthik, Nagaprasad Puvvada, B. N. Prashanth Kumar, Shashi Rajput, Amita Pathak, Mahitosh Mandal,and N. D. Pradeep SinghVol: 5 Pages: 5232?5238Journal: ACS Applied Materials & Interfaces Year: 2013 Posted: 28 Jun 2019
Recently, photoresponsive nanoparticles have received significant attention because of their ability to provide spatial and temporal control over the drug release. In the present work, we report for the first time photoresponsive multifunctional magnetic nanoparticles (MNPs) fabricated using coumarin-based phototrigger and Fe\/Si MNPs for controlled delivery of anticancer drug chlorambucil. Further, newly fabricated photoresponsive multifunctional MNPs were also explored for cell luminescence imaging. In vitro biological studies revealed that coumarin tethered Fe\/Si MNPs of ∼9 nm size efficiently delivered the anticancer drug chlorambucil into cancer cells and thereby improving the drug action to kill the cancer cells upon irradiation. Such multifunctional MNPs with strong fluorescence, good biocompatibility and efficient photocontrolled drug release ability will be of great benefit in the construction of light-activated multifunctional nano drug delivery systems.<\/p>")">
Authors: Avijit Jana , Biswajit Saha , Karthik S , Sharabani Barman , Mohammed Ikbal , Sudip Ghosh and Pradeep N.D. SinghVol: 12(6) Pages: 1041-52Journal: Photochemical & Photobiological Sciences Year: 2013 Posted: 28 Jun 2019
A series of carboxylic acids including amino acids were protected as their corresponding fluorescent ester conjugates by coupling with an environment sensitive fluorophore 9-methylacridine. Photophysical properties of all the ester conjugates along with the protecting group have been investigated. Interestingly, the emission properties of the ester conjugates and 9-methylacridine were found to be highly sensitive to polarity, H-bonding and pH of the environment. Photolysis of all the ester conjugates was carried out using UV light above 360 nm and it was found that in every case the corresponding carboxylic acids were released in high chemical yield. Further, intercalation and the preferred binding mode of acridine-9-methanol and its ester conjugates with DNA were studied. In vitro biological studies revealed that acridine-9-methanol has good biocompatibility, cellular uptake property and cell imaging ability.<\/p>")">
Authors: Partha Sarathi Addy , Baisakhee Saha , N. D. Pradeep Singh , Amit K. Das , Jacob T. Bush , Clarisse Lejeune , Christopher J. Schofield and Amit BasakVol: 49 Pages: 1930-1932Journal: Chem Comm Year: 2013 Posted: 28 Jun 2019
The synthesis of small molecule based 1,3,5-trisubstituted benzenes for photo-mediated capture of human carbonic anhydrase II with visualisation by fluorescence is described.<\/p>")">
Authors: Sanghamitra Atta, Mohammed Ikbal, Nishitha Boda, Samiran S. Gaurib and N. D. Pradeep SinghVol: 12 Pages: 393–403Journal: Photochemical & Photobiological Sciences Year: 2013 Posted: 28 Jun 2019
Photoremovable protecting groups (PRPGs) were demonstrated as a delivery device for controlled release of pheromone under both UV light (≥350 nm) and direct sunlight irradiation. In the present work, (Z<\/em>)-11-hexadecen-1-ol (sex pheromone of Chilo infuscatellus<\/em> Snellen) was chemically caged by four different photoremovable protecting groups (7-hydroxy-4-hydroxymethylcoumarin, 1-pyrenemethanol, 9-anthracenemethanol and 2-(hydroxymethyl)anthraquinone) individually. Photophysical studies showed that the caged pheromone with coumarin, pyrene and anthracenederivatives exhibited strong fluorescence. Controlled release of (Z<\/em>)-11-hexadecen-1-olwas achieved by irradiating the caged compounds in aqueous ethanol both under UV and sunlight. Further, to mimic the environmental conditions, controlled release of (Z<\/em>)-11-hexadecen-1-ol was also studied in soil medium under direct sunlight. Thermogravimetric analysis showed that caging of (Z<\/em>)-11-hexadecen-1-ol by PRPGs significantly reduced its volatility. Bioassay experiments indicated that PRPGs are harmless to soil bacteria (Azotobacter<\/em> sp. and Pseudomonas aeruginosa<\/em>) and in vitro<\/em>cytotoxicity studies on eukaryotic L929 cells showed that PRPGs are also non-toxic. Field bioassays were performed using caged pheromone against maize stalk borer (Chilo partellus<\/em>) and the results showed that the caged alcohol is effective in a number of moths catches instead of free alcohol in a blend for a longer period of time. Our studies indicated that use of PRPGs as delivery device for controlled release of pheromone by sunlight holds great interest for field applications.<\/p>")">
Authors: Mohammed Ikbal, Rakesh Banerjee, Dibakar Dhara, Anakuthil Anoop, N. D. Pradeep SinghVol: 77 Pages: 10557?10567Journal: The Journal of Organic Chemistry (JOC) Year: 2012 Posted: 28 Jun 2019
We have introduced a series of nonionic photoacid generators (PAGs) for carboxylic and sulfonic acids based on Nhydroxyanthracene-1,9-dicarboxyimide (HADI). The newly synthesized PAGs exhibited positive solvachromatic emission (λmax(hexane) 461 nm, λmax(ethanol) 505 nm) as a function of solvent polarity. Irradiation of PAGs in acetonitrile (ACN) using UV light above 410 nm resulted in the cleavage of weak N−O bonds, leading to the generation of carboxylic and sulfonic acids in good quantum and chemical yields. Mechanism for the homolytic N−O bond cleavage for acid generation was supported by time-dependent density functional theory (TD-DFT) calculations. More importantly, using the PAG monomer N-(p-vinylbenzenesulfonyloxy)anthracene-1,9-dicarboxyimide (VBSADI), we have synthesized N-(p-vinylbenzenesulfonyloxy)- anthracene-1,9-dicarboxyimide−methyl methacrylate (VBSADI-MMA) and N-(p-vinylbenzenesulfonyloxy)anthracene-1,9-dicarboxyimide−ethyl acrylate (VBSADI-EA) copolymer through atom transfer radical polymerization (ATRP). Finally, we have also developed photoresponsive organosilicon surfaces using the aforementioned polymers.<\/p>")">
Authors: Avijit Jana,a Biswajit Saha,b Mohammed Ikbal,a Sudip Kumar Ghoshb and N. D. Pradeep Singh*Vol: 11 Pages: 1558–1566Journal: Photochemical & Photobiological Sciences Year: 2012 Posted: 28 Jun 2019
1-(Hydroxyacetyl)pyrene has been introduced as a new fluorescent phototrigger for alcohols and phenols. Alcohols and phenols were protected as their corresponding carbonate esters by coupling with fluorescent phototrigger, 1-(hydroxyacetyl)pyrene. Photophysical studies of caged carbonates showed that they all exhibited strong fluorescence properties. Irradiation of the caged carbonates by visible light (≥410 nm) in aqueous acetonitrile released the corresponding alcohols or phenols in high chemical (95–97%) and quantum (0.17–0.21) yields. The mechanism for the photorelease was proposed based on Stern–Volmer quenching experiments and solvent effect studies. Importantly, 1-(hydroxyacetyl)pyrene showed as a phototrigger for rapid photorelease of the biologically active molecule adenosine. In vitro biological studies revealed that 1-(hydroxyacetyl)pyrene has good biocompatibility, cellular uptake property and cell imaging ability<\/p>")">
Authors: Nilanjana Chowdhury, Sansa Dutta, Swagata Dasgupta, N. D. Pradeep Singh, Mithu Baidyaa and S. K. GhoshVol: 115 Pages: 1239–1250Journal: Photochemical & Photobiological Sciences Year: 2012 Posted: 28 Jun 2019
A new series of (E)-pyrene oxime ester conjugates of carboxylic acids including amino acids were synthesized by coupling with an environment sensitive fluorophore 1-acetylpyrene. (E)-Pyrene oxime esters exhibited strong fluorescence properties and interestingly their fluorescence properties were found to be highly sensitive to the surrounding environment. Direct irradiation of the (E)-pyrene oxime esters by UV light (≥350 nm) resulted in both the photo-Beckmann rearrangement product and products resulting from N–O bond homolysis. Photoproduct formation and their distribution were found to be solvent dependent. Further, we also showed (E)-pyrene oxime esters intercalated into DNA efficiently and photocleaved DNA. Finally we also showed these oxime esters can permeate cells efficiently and may cause cytotoxicity upon irradiation of light<\/p>")">
Authors: Mohammed IkbalVol: 18(38) Pages: 11968 – 11975Journal: Chemistry- A European Journal Year: 2012 Posted: 28 Jun 2019
A new class of carboxylate and sulfonate esters of 1?hydroxy?2(1H<\/em>)?quinolone has been demonstrated as nonionic photoacid generators (PAGs). Irradiation of carboxylates and sulfonates of 1?hydroxy?2(1H<\/em>)?quinolone by UV light (λ<\/em>≥310?nm) resulted in homolysis of weak N?O bond leading to efficient generation of carboxylic and sulfonic acids, respectively. The mechanism for the homolytic N?O bond cleavage was supported by time?dependent DFT calculations. Photoresponsive 1?(p<\/em>?styrenesulfonyloxy)?2?quinolone–methyl methacrylate (SSQL?MMA) and 1?(p<\/em>?styrenesulfonyloxy)?2?quinolone–lauryl acrylate (SSQL?LA) copolymers were synthesized from PAG monomer 1?(p<\/em>?styrenesulfonyloxy)?2?quinolone, and subsequently controlled surface wettability was demonstrated for the above?mentioned photoresponsive polymers.<\/p>")">
Authors: Nilanjana Chowdhury, Swagata Dasgupta, N.D. Pradeep SinghVol: 22 Pages: 4668–4671Journal: Bioorganic & Medicinal Chemistry Letters Year: 2012 Posted: 28 Jun 2019
Two different series of naphthalene and anthracene based hydroxamic acids having amino acid deriva-tives were synthesized. Single strand DNA cleavage was achieved on irradiation of newly synthesizedhydroxamic acids by UV light (P350 nm). Both reactive oxygen species (ROS) and generated radicalsfrom hydroxamic acids were shown to be responsible for the DNA cleavage. Further, DNA cleaving abilityof hydroxamic acids was found to be dependent on its concentration and on its structure.<\/p>")">
Perylene-3-ylmethanol: Fluorescent Organic Nanoparticles as a Single-Component Photoresponsive Nanocarrier with Real-Time Monitoring of Anticancer Drug Release
Authors: Journal: J. Am. Chem. Soc Year: 2012 Posted: 28 Jun 2019
Synthesis, photophysical, photochemical, DNA cleavage/binding and cytotoxic properties of pyrene oxime ester conjugate
Authors: Journal: SYNTHESIS Year: 2012 Posted: 28 Jun 2019
Application of photoremovable protecting group for controlled release of plant growth regulators by sunlight
Authors: Journal: Journal of Photochemistry and Photobiology B: Biology Year: 2012 Posted: 28 Jun 2019
erylen-3-ylmethyl: fluorescent photoremovable protecting group (FPRPG) for carboxylic acids and alcohols
Authors: Journal: Tetrahedron Year: 2012 Posted: 28 Jun 2019
Photoacid generators (PAGs) based on N-acyl-N-phenylhydroxylamines for carboxylic and sulfonic acids
Authors: Journal: Tetrahedron Year: 2011 Posted: 28 Jun 2019
1-acetylpyrene with dual functions as an environment-sensitive fluorophore and fluorescent photoremovable protecting group
Authors: Journal: Tetrahedron Year: 2010 Posted: 28 Jun 2019
Fluorescent Caged Compounds of 2,4-Dichlorophenoxyacetic Acid (2,4-D): Photorelease Technology for Controlled Release of 2,4-D
Authors: Journal: J. Agric. Food Chem Year: 2010 Posted: 28 Jun 2019
Photodegradation of organic dyes in the presence of [Fe(III)-salen]Cl complex and H2O2 under visible light irradiation
Authors: Journal: Journal of Hazardous Materials Year: 2010 Posted: 28 Jun 2019
N,O-Diacyl-4-benzoyl-N-phenylhydroxylamines as photoinduced DNAcleaving agents
Authors: Journal: Bioorganic & Medicinal Chemistry Letters Year: 2010 Posted: 28 Jun 2019
Site-selective synthesis of in situ Ni-filled multi-walled carbon nanotubes using Ni(salen) as a catalyst source
Authors: Journal: Nanotechnology Year: 2010 Posted: 28 Jun 2019
Effect of growth temperature on the CVD grown Fe filled multi-walled carbon nanotubes using a modified photoresist
Authors: Journal: Materials Research Bulletin Year: 2010 Posted: 28 Jun 2019
Lithographically defined site-selective growth of Fe filled multi-walled carbon nanotubes using a modified photoresist
Authors: Journal: Carbon Year: 2010 Posted: 28 Jun 2019
Photochemical Functionalization of Polymer Surfaces for Microfabricated Devices
Authors: Journal: Langmuir Year: 2008 Posted: 28 Jun 2019
Selective Formation of Triplet Alkyl Nitrenes from Photolysis of ß-Azido-Propiophenone and Their Reactivity
Authors: Journal: J. Am. Chem. Soc Year: 2007 Posted: 28 Jun 2019
Supported Bilayer Lipid Membrane Arrays on Photopatterned Self-Assembled Monolayers
Authors: Journal: Chem. Eur. J. Year: 2007 Posted: 28 Jun 2019
A novel method to fabricate tethered bilayer lipid membrane on patterned SAMs substrate
Authors: Journal: Langmuir Year: 2007 Posted: 28 Jun 2019
Photoinduced C-N Bond Cleavage in 2-Azido-1,3-diphenyl-propan-1-one Derivatives: Photorelease of Hydrazoic Acid
Authors: Journal: J. Org. Chem. Year: 2007 Posted: 28 Jun 2019
Authors: Muthukrishnan,S.;Mandel,S.M.;Hackett,J.C.; Singh,Pradeep.N.D.; Hadad,C.M.; Krause, J.A.; Gudmundsdottir, A. D.Vol: 72 Pages: 2757-2768Journal: Tetrahedron Letter Year: 2007 Posted: 27 Jun 2019
Molecular modeling demonstrates that the first excited state of the triplet ketone (T1K) in azide 1b has a (π,π*) configuration with an energy that is 66 kcal\/mol above its ground state and its second excited state (T2K) is 10 kcal\/mol higher in energy and has a (n,π*) configuration. In comparison, T1K and T2K of azide 1a are almost degenerate at 74 and 77 kcal\/mol above the ground state with a (n,π*) and (π,π*) configuration, respectively. Laser flash photolysis (308 nm) of azide 1b in methanol yields a transient absorption (λmax ) 450 nm) due to formation of T1K, which decays with a rate of 2.1 × 105 s-1 to form triplet alkylnitrene 2b (λmax ) 320 nm). The lifetime of nitrene 2b was measured to be 16 ms. In contrast, laser flash photolysis (308 nm) of azide 1a produced transient absorption spectra due to formation of nitrene 2a (λmax ) 320 nm) and benzoyl radical 3a (λmax ) 370 nm). The decay of 3a is 2 × 105 s-1 in methanol, whereas nitrene 2a decays with a rate of ∼91 s-1 . Thus, T1K (π,π*) in azide 1b leads to energy transfer to form nitrene 2b; however, R-cleavage is not observed since the energy of T2K (n,π*) is 10 kcal\/mol higher in energy than T1K, and therefore, T2K is not populated. In azide 1a both R-cleavage and energy transfer are observed from T1K (n,π*) and T2K (π,π*), respectively, since these triplet states are almost degenerate. Photolysis of azide 1a yields mainly product 4, which must arise from recombination of benzoyl radicals 3a with nitrenes 2a. However, products studies for azide 1b also yield 4b as the major product, even though laser flash photolysis of azide 1b does not indicate formation of benzoyl radical 3b. Thus, we hypothesize that benzoyl radicals 3 can also be formed from nitrenes 2. More specifically, nitrene 2 does undergo R-photocleavage to form benzoyl radicals and iminyl radicals. The secondary photolysis of nitrenes 2 is further supported with molecular modeling and product studies<\/p>")">
Authors: Mandel, S. M.; Singh, Pradeep. N. D.; Muthukrishnan, S.; Chang, M.; Krause, J. A.; Gudmundsdottir, A. D.Vol: 8 Pages: 4207-4210Journal: Organic Letter Year: 2006 Posted: 27 Jun 2019
Solid-state photolysis of 1<\/strong> yields 2<\/strong> in a crystal-to-crystal reaction. The reaction takes place by α-cleavage to form a benzoyl and an azido alkyl radical pair. The azido alkyl radicals rearrange into iminyl radicals and N2. The iminyl and benzoyl radicals are held in close proximity within the crystal lattice, which allows them to combine and form 2<\/strong>. X-ray structure analysis, molecular modeling and trapping studies support this mechanism.<\/p>")">
Authors: Singh, Pradeep N. D.; Klima, Rodney F.; Muthukrishnan, Sivaramakrishnan; Murthy, Rajesh S.; Sankaranarayanan, Jagadis; Stahlecker, Heidi M.; Patel, Bhavika; Gudmundsdottir, Anna D.Vol: 46 Pages: 4213-4217Journal: Tetrahedron Letter Year: 2005 Posted: 27 Jun 2019
<\/p>\r\n\r\nA simple and efficient method for synthesizing pyrrolines and tetrahydropyridines via an intramolecular aza-Wittig reaction has been achieved by microwave irradiation of the corresponding chloro-alkane derivatives in the presence of tertiary phosphite and sodium azide. The in situ formation of the alkyl azides makes this a facile and safe method for aza-Wittig reactions.<\/p>")">
Authors: Singh, Pradeep N. D.; Pika, Jana; Krause Bauer, Jeanette A.; Gudmundsdottir, Anna D.Vol: 12 Pages: 2390-2392Journal: Acta Crystallograpgica Section E : Structure Reports Online Year: 2004 Posted: 27 Jun 2019
Photolysis of a 2-(2-isopropyl-benzoyl)benzoate ester derivative in an oxygen-free environment results in the liberation of the alcohol from the ester and formation of the title spirolactone, C20H20O2. The molecule of the title compound adopts the syn<\/em> configuration with respect to the benzene rings, with a dihedral angle of 87.19 (5)° between the benzocyclobutene and isobenzofuranone ring planes. The cyclobutene ring is nearly planar, giving rise to ring distortion, as manifested in the bond distances and angles.<\/p>")">
Authors: Singh, Pradeep. N. D.; Mandel, S. M.; Zhu, Z.; Franz, R.; Ault, B. S.; Gudmundsdottir, A. D.Vol: 68 Pages: 7951-7960Journal: The Journal of Organic Chemistry Year: 2003 Posted: 27 Jun 2019
We report the first detection of triplet alkyl nitrenes in fluid solution by laser flash photolysis of α-azido acetophenone derivatives, 1<\/strong>. Αzides 1<\/strong>contain an intramolecular triplet sensitizer, which ensures formation of the triplet alkyl nitrene by bypassing the singlet nitrene intermediate. At room temperature, azides 1<\/strong> cleave to form benzoyl and methyl azide radicals in competition with triplet energy transfer to form triplet alkyl nitrene. The major photoproduct 3<\/strong> arises from interception of the triplet alkyl nitrene with benzoyl radicals. The triplet alkyl nitrene intermediates are also trapped with molecular oxygen to yield the corresponding 2-nitrophenylethanone. Laser flash photolysis of 1<\/strong> reveals that the triplet alkyl nitrenes have absorption around 300 nm. The triplet alkyl nitrenes were further characterized by obtaining their UV and IR spectra in argon matrices. 13C and 15N isotope labeling studies allowed us to characterize the C−N stretch of the nitrene intermediate at 1201 cm-1.<\/p>")">
Designing Esters Which Release Alcohols Upon Exposure To Light.
Authors: Pika, J.; Konosonoks, A.; Singh, Pradeep. N. D.; Gudmundsdottir, A. D.Vol: 16 Pages: 12-17Journal: The Spectrum Year: 2003 Posted: 27 Jun 2019
Authors: Singh, Pradeep. N. D.; Muthukrishnan, S.; Murthy, R. S.; Klima, R. F.; Mandel, S. M.; Hawk, M.; Yarbrough, N.; Gudmundsdóttir. A. D.Vol: 44 Pages: 9169-9171Journal: Tetrahedron Letter Year: 2003 Posted: 27 Jun 2019
A simple and efficient method for preparing β- and γ-azido substituted arylketones has been achieved by short microwave irradiation of the corresponding halo arylketones and sodium azide in DMSO.<\/p>\r\n\r\nA simple and efficient method for preparing β- and γ-azido substituted arylketones has been achieved by short microwave irradiation of the corresponding halo arylketones and sodium azide in DMSO<\/p>")">
Authors: Singh, Pradeep. N. D.; Carter, C. L.; Gudmundsdóttir, A. D.Vol: 44 Pages: 6763-6765Journal: Tetrahedron Letter Year: 2003 Posted: 27 Jun 2019
An efficient and environmentally friendly method preparing 2H-azirines in good yield has been achieved by microwave irradiation of vinyl azides in solvent free conditions.<\/p>\r\n\r\nAn efficient and environmentally friendly method preparing 2H-azirines has been achieved by microwave irradiation of vinyl azides in solvent free conditions.<\/p>")">
Authors: Pika, J.; Konosonoks, A.; Robinson, R. M.; Singh, Pradeep. N. D.; Gudmundsdottir, A. DVol: 68 Pages: 1964-1972Journal: The Journal of Organic Chemistry Year: 2003 Posted: 27 Jun 2019
We have designed molecules which release alcohols upon exposure to UV light independent of the reaction media, making it possible to liberate alcohols in a controlled manner in applications. Photolysis of 2-(2-isopropylbenzoyl)benzoate ester derivatives 4<\/strong> in various solvents and in thin films results in the liberation of the alcohol moiety from the ester. The reaction mechanism for the release of the alcohol has been elucidated by time-resolved laser flash photolysis. Upon irradiation the triplet excited state of ketone, 4<\/strong> is formed, and its lifetime can be estimated to be between 0.08 and 0.8 ns. The triplet excited state decays by efficient intramolecular H-atom abstraction to form a 1,4-biradical, 8<\/strong>, that has a lifetime of less than 17 ns and is trapped by molecular oxygen. In the absence of oxygen, biradical 8<\/strong> intersystem crosses to form photoenols (Z<\/em>)-9<\/strong> and (E<\/em>)-10<\/strong> in a ratio of 5:2, respectively. Photoenol (Z<\/em>)-9<\/strong> has a lifetime of ∼3000 ns in protic solvents and returns to the starting material through 1,5 intramolecular hydrogen transfer. The other isomer, (E<\/em>)-10<\/strong>, is much longer lived (>1 ms) and releases the alcohol moiety through an intramolecular lactonization.<\/p>")">
Authors: Gopalakrishnan, G.; Kasinath, V.; Pradeep Singh, N. DVol: 4 Pages: 781-782Journal: Org. Lett Year: 2002 Posted: 27 Jun 2019
A novel procedure for the preparation of 3-(4-alkoxyphenyl)-3-methylbutan-2-one in excellent yield is described via polymer-supported AlCl3-catalyzed rearrangement of 1-(4-ethoxyphenyl)-2,2-dimehtylpropan-1-one, followed by O-alkylation under microwave irradiation condition<\/p>")">
Authors: Geetha Gopalakrishnan.; N. D. Pradeep Singh.; V. Kasinath.Vol: 7 Pages: 112-118Journal: A. Juss.Molecules Year: 2002 Posted: 27 Jun 2019
Nimonol (1), a tetranortriterpenoid isolated from the leaves of Azadirachta indica A. Juss (Meliaceae), upon photolysis undergoes both Diels-Alder and ene reactions with singlet oxygen at different sites leading to 14,15,20,21-diepoxy-23-nimonolactone (3), along with nimonolide (4), which have been well-characterised. The novelty of the reported reactions lies in hitherto unreported formation of an α-epoxide in the ring D in tetranortriterpenoids. The photoproduct 4 exhibited antifeedancy comparable to that of azadirachtin-A, the most potent antifeedant constituent isolated from neem<\/p>")">
Authors: Geetha Gopalakrishnan.; Viswanathan Kasinath.; N.D.Pradeep Singh.;V.P.Santhana Krishnan.; K.Anand Solomon.; S.S.Rajan.Vol: 7 Pages: 412-419Journal: Molecules. Year: 2002 Posted: 27 Jun 2019
A facile regio- and chemoselective bromomethoxylation of alkenes under microwave irradiation conditions employing a new polymer supported brominechloride resin is reported. The resin is prepared from the commercially available chloride resin by a simple one step procedure.<\/p>")">
Authors: Gopalakrishnan, G.; Pradeep Singh, N. D.; Kasinath, V.; Siva Rama Krishnan, M.; Malathi, R.; Rajan, S. S.Vol: 50 Pages: 4484-4490Journal: journal of agriculture and food chemistry Year: 2002 Posted: 27 Jun 2019
Structure-related insect antifeedant relationship of 56 limonoids (both natural and modified) from the plants belonging to the order Rutales was attempted considering substitution patterns, oxidation states, and hydrophobicity, as well as distant geometry derived through conformational analysis on molecular modeling. Orientation of the furan and hydroxylation at specific carbon sites have been shown to influence the antifeedancy against the fall armyworm, Spodoptera litura<\/em>.<\/p>")">
Microwave- and ultrasound-assisted oxidation of bio-active limonoids.
Authors: Vol: 42 Pages: 6429-6619Journal: Tetrahedron Letter Year: 2001 Posted: 27 Jun 2019
Photomediated oxidation of Salannin,a Tetranortriterpenoid from Azadiracta indica A.Juss”
Authors: Vol: 6 Pages: 551-556Journal: Molecules Year: 2001 Posted: 27 Jun 2019
Photooxidation of cedrelone, a tetranortriterpenoid from Toona ciliate.
Authors: Vol: 4 Pages: 464-466Journal: Photochem. Photobio. Year: 2000 Posted: 27 Jun 2019
A new synthetic route to dihydrobbenzopyran via Tandem demethylation cyclisation
Authors: Vol: 5 Pages: Journal: Molecules Year: 2000 Posted: 27 Jun 2019
A process for neem formulation with stable active ingredient - the terpenoid Azadirachtin was developed using novel, cost-effective and natural-based ultraviolet stabilizer.
Authors: Journal: Natural Product Lett Year: 1999 Posted: 27 Jun 2019
Authors: Sandipan Biswas, Moumita Gangopadhyay, Shrabani Barman, Jit Sarkar, N.D. Pradeep SinghVol: 222 Pages: 823-828Journal: Sensors and Actuators B: Chemical Year: Posted: 03 Jul 2019
New, simple and inexpensive receptors based on coumarin-thiocarbohydrazone (CTC) and coumarin-carbohydrazone (CC) were synthesized for fluoride ion in CH3CN\/DMSO. Receptor CTC showed specific selectivity and sensitivity toward fluoride giving rise to an ON1–OFF–ON2 fluorescent response and visual colorimetric change. The recognition mechanism was investigated using UV–vis, fluorescence spectroscopy, and 1H NMR titration experiments. The Job's plot analysis and Benesi–Hildebrand equation revealed that the binding between the CTC or CC with F− is in 1:1 stoichiometry. Formation of such 1:1 complex led to the quenching of green fluorescence of CTC and upon excess addition of F−, the [CTC–F−] complex underwent an intracomplex proton transfer from N
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