@article {42496, title = {New chemodosimetric reagents as ratiometric probes for cysteine and homocysteine and possible detection in living cells and in blood plasma}, journal = {Chemistry a European Journal}, volume = {18}, year = {2012}, month = {NOV}, pages = {15382{\textendash}15393}, abstract = {

In this work, we have rationally designed and synthesized two new reagents (L1 and L2), each bearing a pendant aldehyde functionality. This aldehyde group can take part in cyclization reactions with β- or γ-amino thiols to yield the corresponding thiazolidine and thiazinane derivatives, respectively. The intramolecular charge-transfer (ICT) bands of these thiazolidine and thiazinane derivatives are distinctly different from those of the molecular probes (L1 and L2). Such changes could serve as a potential platform for using L1 and L2 as new colorimetric/fluorogenic as well as ratiometric sensors for cysteine (Cys) and homocysteine (Hcy) under physiological conditions. Both reagents proved to be specific towards Cys and Hcy even in the presence of various amino acids, glucose, and DNA. Importantly, these two chemodosimetric reagents could be used for the quantitative detection of Cys present in blood plasma by using a pre-column HPLC technique. Such examples are not common in contemporary literature. MTT assay studies have revealed that these probes have low cytotoxicity. Confocal laser scanning micrographs of cells demonstrated that these probes could penetrate cell membranes and could be used to detect intracellular Cys/Hcy present within living cells. Thus, the results presented in this article not only demonstrate the efficiency and specificity of two ratiometric chemodosimeter molecules for the quantitative detection of Cys and Hcy, but also provide a strategy for developing reagents for analysis of these vital amino acids in biological samples.

}, keywords = {charge transfer; chemodosimetric detection; cysteine/ homocysteine sensors; fluorescent probes; imaging agents; ratiometric probes}, doi = {10.1002/chem.201201621}, author = {Das, Priyadip and Mandal, Amal Kumar and Chandar, Nellore Bhanu and Baidya, Mithu and Bhatt, Harshad B. and Ganguly, Bishwajit and Ghosh, Sudip K. and Das, Amitava} } @article { ISI:000325552900018, title = {New chemodosimetric probe for the specific detection of Hg2+ in physiological condition and its utilisation for cell imaging studies}, journal = {Dalton Transactions}, volume = {42}, number = {42}, year = {2013}, month = {JUL}, pages = {15097-15105}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A dithiane derivative of BODIPY is synthesized. This new reagent could be used for the specific and instantaneous detection of Hg2+ in physiological condition. This dithiane reagent reacts specifically with Hg2+ to regenerate the parent BODIPY-aldehyde with consequential change in visually detectable optical responses and this provides the possibility of using this reagent as a colorimetric probe or as a fluorescent biomarker/imaging reagent. Further, non-covalent interactions could be utilized for formation of an inclusion complex with biologically benign beta-cyclodextrin for enhancing its solubility in aqueous environment and this included adduct could be used as a fluorescent marker and imaging reagent for Hg2+. Uptake of Hg2+ ions in live HeLa cells, exposed to a solution having Hg2+ ion concentration as low as 2 ppb, could also be detected by confocal laser microscopic studies.

}, issn = {1477-9226}, doi = {10.1039/c3dt51744f}, author = {Saha, Sukdeb and Agarwalla, Hridesh and Gupta, Hariom and Baidya, Mithu and Suresh, E. and Ghosh, Sudip K. and Das, Amitava} } @article { ISI:000324928000035, title = {New receptor with a FRET based fluorescence response for selective recognition of fumaric and maleic acids in aqueous medium}, journal = {Chemical Communications}, volume = {49}, number = {84}, year = {2013}, month = {AUG}, pages = {9818-9820}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Preferential binding of a new reagent to fumaric acid could be utilized for its estimation in aqueous medium and in commercial fruit juice.

}, issn = {1359-7345}, doi = {10.1039/c3cc45051a}, author = {Reddy, Upendar G. and Lo, Rabindranath and Roy, Sovan and Banerjee, Tanmay and Ganguly, Bishwajit and Das, Amitava} } @article {42491, title = {Newly designed resorcinolate binding for Ru(II)- and Re(I)- polypyridyl complexes on oleic acid capped tio2 in non-aqueous solvent: prolonged charge separation and substantial thermalized 3MLCT injection}, journal = {Journal of Physical Chemistry C}, volume = {117}, year = {2013}, month = {JAN}, pages = {3084{\textendash}3092}, abstract = {

Femtosecond pump{\textendash}probe spectroscopic studies on a series of newly synthesized resorcinol-based Ru(II) and Re(I) complexes on oleic acid capped TiO2 nanoparticles have been carried out in chloroform, and the results are compared with those of the catechol analogues. The ruthenium complex shows biexponential injection; the second component arises due to injection from the thermally equilibrated 3MLCT states as a result of a weaker strength of the resorcinolate binding. Also, in comparison with catechol binding, as a result of a greater diffusion of the injected electrons into TiO2, the back electron transfer (BET) is slowed down significantly for the ruthenium complex. These are distinctive observations for any mononuclear ruthenium{\textendash}polypyridyl{\textendash}enediol complex reported thus far. However, the rhenium complex educes single exponential ultrafast injection (\<120 fs) because of apparent injection in a high density of states and shows the most prominent results with \~{}50\% slowdown in the charge recombination rate as compared to the analogous catechol bound system. These results exemplify the probable development of highly capable sensitizer dyes with resorcinol as the anchoring group for the development of efficient dye-sensitized solar cells.

}, doi = {10.1021/jp310570n}, author = {Banerjee, Tanmay and Kaniyankandy, Sreejith and Das, Amitava and Ghosh, Hirendra Nath} } @article { ISI:000341282100018, title = {New Ru(II)/Os(II)-polypyridyl complexes for coupling to TiO2 surfaces through acetylacetone functionality and studies on interfacial electron-transfer dynamics}, journal = {Dalton Transactions}, volume = {43}, number = {36}, year = {2014}, month = {SEP}, pages = {13601-13611}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

New Ru(II)- and Os(II)-polypyridyl complexes have been synthesized with pendant acetylacetone (acac) functionality for anchoring on nanoparticulate TiO2 surfaces with a goal of developing an alternate sensitizer that could be utilized for designing an efficient dye-sensitized solar cell (DSSC). Time-resolved transient absorption spectroscopic studies in the femtosecond time domain have been carried out. The charge recombination rates are observed to be very slow, compared with those for strongly coupled dye molecules having catechol as the anchoring functionality. The results of such studies reveal that electron-injection rates from the metal complex-based LUMO to the conduction band of TiO2 are faster than one would expect for an analogous complex in which the chromophoric core and the anchoring moiety are separated with multiple saturated C-C linkages. Such an observation is rationalized based on computational studies, and a relatively smaller spatial distance between the dye LUMO and the TiO2 surface accounted for this. Results of this study are compared with those for analogous complexes having a gem-dicarboxy group as the anchoring functionality for covalent binding to the TiO2 surface to compare the role of binding functionalities on electron-transfer dynamics.

}, issn = {1477-9226}, doi = {10.1039/c4dt01571a}, author = {Banerjee, Tanmay and Biswas, Abul Kalam and Sahu, Tuhin Subhra and Ganguly, Bishwajit and Das, Amitava and Ghosh, Hirendra Nath} } @article { ISI:000340513400023, title = {Novel fluorescence probe for estimation of cysteine/histidine in human blood plasma and recognition of endogenous cysteine in live Hct116 cells}, journal = {Chemical Communications}, volume = {50}, number = {69}, year = {2014}, month = {SEP}, pages = {9899-9902}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A new Cu(II)-complex is used as a {\textquoteleft}{\textquoteleft}Turn-On{\textquoteright}{\textquoteright} luminescence probe for specific detection of endogenous Cys in live Hct116 cells and Cys present in human blood plasma without any interference from other amino acids, especially GSH and Hcy. Difference in the mechanistic pathway for Cys and His recognition is discussed.

}, issn = {1359-7345}, doi = {10.1039/c4cc04214j}, author = {Reddy, Upendar G. and Agarwalla, Hridesh and Taye, Nandaraj and Ghorai, Suvankar and Chattopadhyay, Samit and Das, Amitava} } @article { ISI:000360658000003, title = {New imaging reagents for lipid dense regions in live cells and the nucleus in fixed MCF-7 cells}, journal = {Journal of Materials Chemistry B}, volume = {3}, number = {36}, year = {2015}, month = {AUG}, pages = {7177-7185}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Two new uracil (U) and 5-flurouracil (5-FU) labeled ruthenium(II)-polypyridyl based cellular imaging reagents are reported. Confocal laser scanning microscopic images with live and paraformaldehyde (PFA) fixed MCF-7 cells are examined using these two low-cytotoxic reagents. Experimental results show that these two complexes, appropriately functionalized with U (1) and 5-FU (2), have specific affinity for the lipid dense regions like the endoplasmic reticulum, cell membrane, and cytoplasmic vacuoles in live MCF-7 cells, and dye internalization in these regions happened following an endocytosis pathway. Interestingly, these two complexes are found to be localized in the nucleus of the PFA fixed cells. For fixed cells, presumably the lipid layer disruption helped in the explicit localization of the complexes 1 and 2 in the cell nucleus through specific interaction with cellular DNA. Poor and non-specific internalization of an analogous model complex 3, without having a U or 5-FU moiety, reveals the definite influence of U or 5-FU as well as the role of lipophilicity of the respective complex 1 and 2 in the cellular internalization process. Apart from these, a large Stokes shift (similar to 160 nm) and an appreciably long lived (MLCT)-M-3 excited state (similar to 320 ns) in aq. buffer medium (pH 7.4) are other key features for complexes 1 and 2. Unlike the common nuclear DNA staining reagents like DAPI, these low-cytotoxic reagents are found to be highly stable towards photo-bleaching upon irradiation with 455 nm at the MLCT band for these complexes.

}, issn = {2050-750X}, doi = {10.1039/c5tb01309g}, author = {Ramu, Vadde and Ali, Firoj and Taye, Nandaraj and Garai, Bikash and Alam, Aftab and Chattopadhyay, Samit and Das, Amitava} } @article { ISI:000349325400040, title = {New turn on Pd2+-specific fluorescence probe and its use as an imaging reagent for cellular uptake in Hct116 cells}, journal = {Chemical Communications}, volume = {51}, number = {17}, year = {2015}, month = {JAN}, pages = {3649-3652}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A new coumarin-rhodamine conjugate is used as a specific probe for Pd2+ ions and this could even delineate Pd(II) from Pd(0) or Pd(IV) in aqueous buffer medium (pH similar to 7). Laser confocal microscopic studies reveal that efficient cellular internalization of this reagent helps in imaging the cellular uptake of Pd2+ as low as 0.1 ppm in Hct 116 cells. This reagent could even be used for estimation of Pd2+ in human urine samples.

}, issn = {1359-7345}, doi = {10.1039/c4cc10171e}, author = {Reddy, Upendar G. and Ali, Firoj and Taye, Nandaraj and Chattopadhyay, Samit and Das, Amitava} }