Preparation and properties of polyhydroxybutyrate microspheres as drug carriers

Designing of controlled-release drug delivery systems is a promising and rapidly developing line of pharmacology. The main advantage of using drug delivery systems is that drug concentration in a patient’s blood and/or tissues can be maintained at a target level for an extended time (Kost 2001). The principal requirement for fabricating prolonged-action controlled-release drug delivery systems is availability of an appropriate material, which must be absolutely harmless to an organism and possess the necessary physical-mechanical and biomedical properties, including degradability in biological media. Polyhydroxyalkanoates (PHAs) are good candidates for fabrication of drug delivery systems (Ueda 2003, Piddubnyak 2004), because they possess all the properties required of materials for these systems. These polymers are biocompatible and inert towards animal tissues; in biological environments they are degraded to end products (CO2 and H2O). In contrast to other materials that are widely used in controlled drug delivery, such as gelatine, proteins, polylactide and poly(ethyleneglycol)-poly(D,L-lactide), PHAs are available in a chemically pure form (Gürsel 1995) and their degradation rate in biological media is low. By varying the chemical structure of PHAs or blending them with different materials, one can control porosity and degradation rate of the polymeric matrix and, hence, the rate of drug release. The purpose of this study was to prepare microspheres from PHA and to test their in vitro.