A new polymer composition based on bacterial poly-3-hydroxybutyrate and chitosan encapsulating the wide-spectrum antibiotic rifampicin was developed. Both biopolymers are biocompatible and can undergo enzymatic and hydrolytic degradation. Variations in the ratio of poly-3-hydroxybutyrate and chitosan in the mixture, altering the ratio of hydrophilic and hydrophobic components, influenced not only the sorption capacities for water and drug but also the controlled release profile of the drug. Analysis of kinetic curves for rifampicin release showed that drug release was determined by the superimposition of two processes: drug desorption by a diffusional mechanism and hydrolytic degradation of poly-3-hydroxybutyrate, which was most marked after the initial diffusional stage. Kinetic parameters (the constant of hydrolysis of poly-3-hydroxybutyrate k and the coefficient of diffusion of rifampicin D) were required for a full description of the poly-3-hydroxybutyrate-chitosan-rifampicin system. The fact that the kinetic curves had a prolonged linear region suggests that this composition may have value as a biodegradable therapeutic system for local controlled drug release.The creation of polymer therapeutic systems for prolonged and targeted delivery of biologically active substances is a relevant but quite difficult practical task. Intense studies of a variety of polymeric drug formulations [1 -5] have led to two principal conclusions: first, that at the micro and submicro levels, the most advantageous biodegradable polymer systems are those whose macromolecules are degraded to nontoxic intermediate and end products [6 -8], and secondly, that the search for polymer carriers often requires the use of mixed compositions with the condition that their physicochemical and delivery properties improve on or modify the properties of the starting polymers [9].With these points in mind, a new polymer system based on bacterial poly-3-hydroxybutyrate (PHB) and chitosan encapsulating the wide-spectrum antibiotic rifampicin (3-[[4-methyl-1-piperazinyl)imino]methyl]rifamycin) was studied. These components for the polymer mixture were selected on the basis that the two polymers are biocompatible [10,11] and can undergo enzymatic and hydrolytic degradation [12,13]. The potential value of PHB-chitosan mixtures arises from the fact that they have an amphiphilic composition and that the hydrophilic:hydrophobic balance of the system can be adjusted. While the polyester PHB is quite hydrophobic and its sorption capacity for water is no greater than 1% (w/w) in normal conditions [14], the equilibrium sorption of water by chitosan, because of its amine and hydroxyl groups, reaches tens of % [15]. Thus, changes in the component ratio allow the water content of the composition to be altered, while the presence of functional groups in chitosan promotes significant increases in the sorption capacity for drugs in the mixture. EXPERIMENTAL SECTIONStudies were performed using bacterial poly(R-3-hydroxybutyrate) as granules obtained from Biomer Co ...

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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.

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