Preparation of thermo-responsive acrylic hydrogels useful for the application in transdermal drug delivery systems

In this research, hydrogel membranes mainly composed of three kinds of latex particles within carboxymethyl cellulose (CMC) matrix were prepared for the purpose of transdermal drug release. All three latex particles were acrylic systems and synthesized by emulsion polymerization with the addition of an initiator, potassium persulfate, and a crosslinking agent, methylene bisacrylamide. Among them, poly(acrylic acid-co-sodium acrylate) copolymer was applied to increase the swelling ability of hydrogel membrane. Degree of neutralization or the amount of added crosslinking agent was changed to give the optimum properties endowed to the membrane. Poly(acrylic acid-co-2-ethylhexyl acrylate) copolymer latex was used to provide the adhesive ability for the membrane. Finally, to give a thermo-responsive behavior in swelling, poly(N-isopropyl acrylamide) latex and its copolymers were synthesized by polymerization of N-isopropyl acrylamide with different amounts of acrylic acid, in which lower critical solution temperature (LCST) could be modulated. Besides blending these microgel particles with CMC and several other compounds such as tartaric acid and PAA oligomer used to adjust pH value of doping solution, aluminum ion (Al3+) was applied to give ionic interaction with carboxylate groups distributed in all three latex particles, thus giving interconnected interactions among all microgel particles and in turn a good membrane formability. Morphology, structures and swelling capability of prepared hydrogel membranes were then examined. Caffeine, used as the model drug, was incorporated into membranes and the drug release behavior at different temperatures was evaluated. These prepared hydrogel membranes have potential in the application of transdermal drug delivery system.