Structure and prolonged transport in a biodegradable poly(R-3-hydroxybutyrate)-drug system

In order to create new biodegradable systems for the targeted transport of drugs, poly(3-hydroxy-butyrate) films containing the antibiotic rifampicin in an amount of 5-15 wt % as a model drug are prepared. Film surfaces are studied via scanning electron microscopy, and various structural elements (globules and fibrils) are found. Polymer samples isolated from melt or solution feature different degrees of porosity. It is shown that the kinetic profiles of rifampicin release are of an abnormal character. An analysis of the profiles shows that the release of rifampicin is controlled by the superposition of two processes: its desorption via the diffusion mechanism (the nonlinear segment) and hydrolytic degradation of poly(3-hydroxybutyrate) (the extended linear segment), which becomes well defined after completion of the diffusion stage. The diffusionkinetic model of the process is developed.