Synthesis, characterisation and drug release from a range of novel smart co-biodegrable delivery systems

Abstract

In recent years many biodegradable polymers have been investigated particularly for controlled delivery of drugs or proteins/peptides. The most commonly studied biodegradable polymers for controlled drug delivery are based on poly (esters), such as poly (lactides) of poly (glycolic acid). Limited research of environmentally sensitive and degradable systems capable of controlling drug release in response to a specific stimulus has been undertaken. The present thesis investigates the potential application of a novel intelligent biodegradable hydrogel. A series of novel multifunctional hydrogels that combined the merits of both thermoresponsive and biodegradable polymeric materials were designed by varying both the composition ratios and the molecular weight of the precursor unit. The hydrogels were composed of N- isopropylacrylamide as a thermoresponsive unit and chemically modified poly (lactic acid) (PLA) as a hydrolytically degradable and hydrophobic unit. The chemical structures of the hydrogels were characterised using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The hydrogels were thermoresponsive, with an increase in the lower critical solution temperature (LCST) the higher the percent of lactic acid diacrylate macromoer (FLAM) incorporated into the hydrogels. Swelling properties were dependant on temperature as well as the FLAM content. Increasing the molecular weight of FLAM resulted in both larger pores and a decrease in the crosslinking density; the effect being magnified by the higher molar ratio of FLAM to poly N- isopropylacrylamide (FNIFAAM).