Department of Biological Sciences

Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1922

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Author: search.filters.author.Laskar, Inamur RahamanSubject: search.filters.subject.Chemistry

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Now showing 1 - 4 of 4
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    Evaluation of novel platinum(ii) based AIE compound-encapsulated mesoporous silica nanoparticles for cancer theranostic application
    (RSC, 2018) Chowdhury, Rajdeep; Laskar, Inamur Rahaman
    Advanced biomedical research has established that cancer is a multifactorial disorder which is highly heterogeneous in nature and responds differently to different treatment modalities, due to which constant monitoring of therapy response is becoming extremely important. To accomplish this, different theranostic formulations have been evaluated. However, most of them are found to suffer from several limitations extending from poor resolution, radiation damage, to high costs. In order to develop a better theranostic modality, we have designed and synthesized a novel platinum(II)-based ‘aggregation induced emission’ (AIE) molecule (named BMPP-Pt) which showed strong intra-cellular fluorescence and also simultaneously exhibited potent cytotoxic activity. Due to this dual functionality, we wanted to explore the possibility of using this compound as a single molecule based theranostic modality. This compound was characterized using elemental analysis, NMR and IR spectroscopy, mass spectrometry and single crystal X-ray structure determination. BMPP-Pt was found to exhibit a high AIE property with emission maxima at 497 nm. For more efficient cancer cell targeting, BMPP-Pt was encapsulated into mesoporous silica nanoparticles (Pt-MSNPs) and the MSNPs were further surface modified with an anti-EpCAM aptamer (Pt-MSNP-E). Pt-MSNPs exhibited higher intracellular fluorescence compared to free BMPP-Pt, though both of them induced a similar degree of cell death via the apoptosis pathway, possibly via cell cycle arrest in the G1 phase. Anti-EpCAM aptamer modification was found to increase both cytotoxicity and intracellular fluorescence compared to unmodified MSNPs. Our study showed that EpCAM functionalized BMPP-Pt loaded MSNPs can efficiently internalize and induce apoptosis of cancer cells as well as show strong intracellular fluorescence. This study provides clues towards the development of a potential single compound based theranostic modality in future.
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    A New Aggregation Induced Emission Active Halochromic White Light Emissive Molecule: Combined Experimental and Theoretical Study
    (RSC, 2020) Chowdhury, Rajdeep; Laskar, Inamur Rahaman; Roy, Ram Kinkar
    Red/near infrared-emissive organic molecules that are aggregation induced emission (AIE) active and having a pH-sensitive core are high in-demand for real-world applications. We have designed and synthesized a far-red to near infrared (NIR) fluorogenic donor–acceptor (D–A) type probe 4-((4-(2-(3,3-dimethyl-3H-indole-2-yl)vinyl)phenyl)(phenyl)amino)benzaldehyde (TPA-SCY), that can undergo protonation with a stronger intramolecular charge transfer. The molecule is pH-sensitive and responds to the acidic behavior of chloroform to produce a unique halochromic white-light emission. Owing to its sensitivity toward pH and its highly emissive nature in the red/NIR region at low pH (approximately 3–5), it accumulates in the intracellular lysosomes and can be used as a live-tracker for lysosomes. Successful application of time-dependent density functional theory with the use of an optimally tuned range-separated hybrid functional reproduces the experimental absorption and emission spectra within the 1–5 nm range (which is not observed when conventional range-separated hybrid functionals are used). Thus, the present work embodies synthesis and photophysical studies (supported by an efficient and highly accurate theoretical tool) of a new AIE active halochromic white light emissive molecule with extensive charge transfer properties and having the ability to behave as a live LysoTracker.
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    A multistimuli responsive heteroleptic iridium(iii) complex: role of hydrogen bonding in probing solvent, pH and bovine serum albumin (BSA)
    (RSC, 2020) Chowdhury, Shibasish; Laskar, Inamur Rahaman
    This article focuses on the vital role of hydrogen bonding to explain some unusual photophysical behaviors of an ‘Aggregation-induced emission’ (AIE) active Iridium(III) complex. The preponderance of hydrogen bonding leads to the complex's multifunctional character, viz., sensing ability of base and protein (BSA), pH probing, and solvatochromism. Depending on the hydrogen bonding capacity of the solvents, the emission properties of the complex are changed, i.e., green emission in non-polar solvents, yellowish-green emission in a chlorinated solvent, bright yellow emission in a polar aprotic solvent and weak yellow emission in polar protic solvent. A robust green emission was obtained with the addition of BSA into a solution of 1. The sensitivity of the complex to BSA was measured to be 9.3 pM. The mechanisms in all these cases have been explored based on control experiments and computational calculations/studies (DFT, TD-DFT, Docking).
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    Engineering a light-driven cyanine based molecular rotor to enhance the sensitivity towards a viscous medium
    (RSC, 2021) Chowdhury, Rajdeep; Laskar, Inamur Rahaman; Majumder, Syamantak; Mukherjee, Sudeshna
    This article describes the enhanced sensitivity to a viscous medium by a molecular rotor based fluorophore (RBF), TPSI I. The TPSI I molecule is designed in such a way that it consists of a rotor and a fluorophore with a π-rich bridge between them. TPSI I is a light-responsive material in solution as well as in the solid state. The structural design of the molecule allows flexible rotation and photo-induced cis–trans isomerization both in the solid state as well as in solution. These combined attributes of TPSI I are responsible for the ultrasensitive viscosity response of the new material, which was verified through the Förster–Hoffmann equation. According to this equation, the derived ‘x’ value is 1.02 (x is related to the sensitivity) which is the highest among the contemporary reports for RBFs. The facts were evidenced both by experimental as well as theoretical data. The ultrasensitivity towards viscosity was further analyzed in in vitro studies by detecting the subtle changes in the alteration of intracellular viscosity in normal and cancerous cells. An alteration of intracellular viscosity in cells treated with viscosity modulators was also confirmed using a previously well-established viscosity measurement technique, dynamic measurement through the piezoelectric patch. Our research offers a detailed mechanism to improve viscosity sensors and an efficient probe for detecting minute changes in intracellular viscosity.