Dynamics and Application s of Graphene Quantum Dots in Drug Delivery, Catalysis ROS Generation Generation

Sinha, Riya (2023) Dynamics and Application s of Graphene Quantum Dots in Drug Delivery, Catalysis ROS Generation Generation. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Riya Sinha (18RS071)) 18RS071.pdf - Submitted Version Restricted to Repository staff only Download (23MB)

Abstract

My thesis mainly deals with the synthesis of bare and functionalized graphene quantum dots (GQDs), a zero-dimensional nanomaterial consisting of 1-10 layers of the 2-D magic material graphene, via several bottom-up approaches, tunability of the unique optical properties (arising due to quantum confinement effect & edge effect) and improvement of physical and chemical properties of pristine GQDs by chemical modification to explore their applications in drug delivery, singlet oxygen generation using resonance energy transfer as an investigatory tool and catalysis. In the first work, we have synthesized bare GQDs via pyrolysis of citric acid and used it as a carrier for delivering the chemotherapeutic drug daunomycin (DN) to DNA exploiting π–π stacking and electrostatic interactions between the drug & the crystalline GQDs. Fluorescence resonance energy transfer (FRET) mechanism was used to provide the quantitative details of DN delivery by GQDs and its subsequent uptake by the DNA duplex. This entire process was found to be regulated by the difference in binding constants. In the second work, we have used fluorescence lifetime imaging spectroscopy (FLIM) and FRET to show that preloaded bare GQDs assist the drug DN (mainly located at the membrane surface and hydrophobic bilayer) to translocate inside the aqueous core of DPPC giant unilamellar vesicles. In the third work, we have synthesized amine-functionalized GQDs (AGQDs) via one-pot hydrothermal method and a porphyrin derivative 5,10,15,20-tetra(m-nitrophenyl) porphyrin (TNPP). Here, we have demonstrated effective singlet oxygen generation by TNPP-AGQD composites through energy transfer, the singlet oxygen quantum yield being comparable to standard photosensitizer Meso-tetraphenylporphyrin (TPP). Moreover, TNPP-AGQD pair was found to be much less cytotoxic as compared to free TNPP. In the last work, we have synthesized two more variants of GQDs, BSA-protected and GSH-protected along with the bare ones and applied them as catalysts for efficient reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). A 100-fold enhancement in reduction rate was observed on using GSH- and BSA-GQDs instead of bare GQDs.

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