VISCOELASTIC, SWELLING KINETIC AND DRUG RELEASE CHARACTERIZATION OF POLY (ACRYLIC ACID)-GRAFTED-GELLAN

Lyophilic, viscoelastic, swelling kinetic and drug release characterizations of poly (acrylic acid) –grafted-gellan (PAAc-g-GG) were the main objective of this study. At first, a suitable solvent for PAA-g-GG was found out by lyophilicity study followed by viscoelastic study on PAAc-g-GG with different degree of grafting. The study showed that the degree of grafting greatly influences the viscoelastic nature of copolymer, which further governs the drug release pattern from the polymer matrix. The copolymer with highest grafting showed much higher starting % strain (17.73%), stress (53.3 Pa) for structural breakdown at Gꞌ = Gꞌꞌ (213.5 Pa), higher storage modulus (G’), much higher values of complex viscosity (11.46 Pa.s) and cross-over point (Gꞌ = Gꞌꞌ =271.86 Pa) compared to that of low-grafted copolymer. In 0.1N HCl, swelling index (%WE) is found to be directly proportional to percentage grafting (%G) and batches with higher grafting exhibited lowest initial swelling rate demonstrating its inversely proportional relation to %G. Equilibrium swelling and hydration are also found to be proportional to %G. The same effect has been observed in PBS with exception that the magnitude of the parameters obtained in PBS is very much higher compared to that in 0.1N HCl. The copolymer showed sustained drug release over 10 hours period and the study revealed Case-1 Fickian diffusion or square root of time kinetic based release mechanism. The study reveales that viscoelastic and swelling study might be useful to understand how the degree of grafting governs the drug release.