The role of carboxyl group of pressure sensitive adhesive in controlled release of propranolol in transdermal patch: Quantitative determination of ionic interaction and molecular mechanism characterization.

Acrylic pressure sensitive adhesives (PSAs) are widely used in transdermal drug delivery system (TDDS). However, there was little research about the quantitative relationship between drug release and drug-PSAs interaction. In this study, five acrylic PSAs with different molar fraction of carboxyl group were designed and synthesized. Propranolol (PRO) was used as model drug to evaluate release profiles in the PSAs in vitro and in vivo. The drug release percent in the PSAs were 81.66, 78.22, 51.66, 21.81 and 11.73%, and their release behaviors were decreased with carboxyl group content of PSAs. Furthermore, it was found that quantity of carboxyl group of PSAs was equal to residual drug by the quantitative determination. In addition, the ionic interaction between PRO and PSAs was confirmed by FT-IR and MDSC results qualitatively. Using the FT-IR, MDSC, Flory-Huggins interaction parameters and molecular dynamic simulation, interaction strength between drug and PSAs was determined quantitatively, which demonstrated that the drug release amount decreased linearly with interaction strength. Based on above results, we proposed that the PRO was possibly binding to the carboxyl group of PSAs one-by-one, which provided references for the accurate design of TDDS.