Development of L-Amino Acid Based Polymer Brushes

Abstract

The necessity for controlled and targeted drug delivery continues to grow, demanding the development of highly efficient, sustainable, and biodegradable carriers for drug delivery applications. Among various biomaterials, L-amino acids serve as commendable bio-resources for designing unique polymeric architectures due to their inherent biocompatibility and biodegradability. In this thesis, we focus on the design and synthesis of a novel biodegradable polymer, specifically a propargyl-functionalized L-tyrosine-based poly(ester-urethane) backbone. To introduce functionality, we separately synthesize azide-containing tetraphenylethylene (TPE), a fluorophore exhibiting Aggregation-Induced Emission (AIE), along with polyethylene glycol (PEG)-azide of varying chain lengths. These components are then conjugated onto the polymer backbone via a highly efficient click reaction, leading to the formation of biodegradable fluorescent polymer brushes with tuneable compositions of TPE. The synthesized polymer brushes are thoroughly characterized using nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and Fourier-transform infrared (FTIR) spectroscopy. Their thermal and crystallinity properties are investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and powder Xray diffraction (PXRD), allowing us to analyse the effect of PEG chain length and composition on the crystallinity of the polymeric brushes. Further, we explore the self-assembly behaviour of these polymer brushes and evaluate how self-organization influences the AIE properties of the TPE-tagged fluorophore through photophysical analysis. The size and morphology of the resulting nanoparticles are examined via dynamic light scattering (DLS) and transmission electron microscopy (TEM). Finally, to assess their potential in drug delivery applications, we evaluate their drug or dye loading capacity (DLC) by encapsulating Nile Red dye, ensuring the suitability of these polymer brushes as efficient carriers in drug delivery systems