Simultaneous determination of drug surface concentration and polymer degradation kinetics in biodegradable polymer/drug membranes: a model drug delivery system

摘要

This paper reports new simultaneous ToF-SIMS analysis to determine both the earliest stage of polymer degradation and the surface concentration of a drug additive. The static SIMS spectra of a model Ph_3N/poly(L-lactic acid) (PLLA) (20:80 wt.%) blend matrix (t ～ 0.4 μm on 1.0 cm~2) hydrolyzed in buffered conditions are simultaneously and independently analyzed in the low mass range for the surface accumulation profile of Ph_3N and in the high mass for the hydrolytic degradation kinetics of PLLA, respectively. The rate of PLLA degradation at pH 10.0 is ～ 2 times faster than that at pH 7.4, but the corresponding rate of Ph_3N accumulation at the surface is accelerated by a factor of ～ 10.5 times faster. The results provide new insight in evaluating the surface concentration of Ph_3N (pK_b = 0) from the blends, indicating that the initial rapid increase in surface concentration of Ph_3N is related to but not singularly dependent on the rate of PLLA degradation.