Preparation,Properties And The Drug Release Of PH-sensitive P(CMC-g-AA) Hydrogels

The environment-sensitive hydrogels which characterized by its stimuliresponsive property have been used widely in many areas, especially in the controlled drug release and targeted drug delivery field, and thus attracting much attention of the scholars at home and abroad recently. At present, the theoretical study on the environment-sensitive gels has been mainly confined to the study of the equilibrium swelling state, and the research of swelling processes still needs to be promoted. According to the literature review, the thermodynamic characteristics (volume phase transition) of environment-sensitive hydrogels can effectively control drugs reaching targeted point, but how to control the targeted delivery system release drug properly(that is, how to maintain the plasma-drug concentration inside the treatment window), is related firmly to the research of kinetic theories especially with that of swelling kinetic theories. Based on this, two series of pH-sensitive hydrogels were synthesized and the effect of the weak interaction on the property of the hydrogels was studied from the following aspects:(1) A series of hydrogels were synthesized by graft cross-link copolymerization of carboxyl methylcellulose (CMC) and acrylic acid (AA) using N, N'-methy-lene-bis-(acrylamide) as a cross-linker, and the structure was characterized; (2)The swelling kinetics of P(CMC-g-AA) hydrogels were studied; (3)The deswelling kinetics of P(CMC-g-AA) hydrogels were studied; (4)The controlled release properties of P(CMC-g-AA) hydrogels were studies; (5) PAA Hydrogels were synthesized, both of the swelling and deswelling kinetics were studied.The results show that the overshoot effect was observed in pH＜pKa buffer solutions for both and the swelling processes follow a quantitative model proposed by E. D(?)ez-Pe(?)a et al, the theoretical curves are in very good agreement with the experimental data. While in pH＞pKa buffer solutions, the overshoot effect does not appear and the swelling processes follow Schott second-order rate equation; In pH2.2～6.0 buffer solution, the deswelling processes of both hydrogels appear two different situations respectively: in pH2.2～3.0 buffer solution, hydrogels deswelled directly, while in pH 4.0～6.0 buffer solution, hydrogels swelled for a short time before the deswelling. We contributed the phenomenon to the shielding effect of sodium ions on the carboxylic ion of the network, based on wich we proposed two different kinds of deswelling kinetics model, the theoretical curves are in very good agreement with the experimental data. In 37℃pH2.0 buffer solution, the drug release dynamics of P(CMC-g-AA) fits the Ritger-Peppa model, and the mechanism of drug release were Fick diffusion, while in pH7.4 buffered solution, the drug release dynamics of P(CMC-g-AA) fits the diffuse-relaxation model, and the mechanism of drug release were diffusion and relaxation.