Mineral‐Coated Polymer Microspheres for Controlled Protein Binding and Release

Abstract

sized that protein-mineral interactions could be used as an alternative mechanism to create biodegradable micro-carriers for controlled protein binding and release. In particular, we employ the calcium phosphate mineral hydroxyapatite as a substrate for protein binding and release, as it has been used for over 50 years in chromatographic protein separations based on its ability to bind and release both acidic and basic proteins under particular solution conditions. Here we provide a demonstration that biodegradable polymer microspheres can be coated with an inorganic hydroxyapatite layer using biomimetic process by incubating microspheres in a modified simulated body fluid (mSBF), and that this biodegradable coating can be used as a substrate for binding and sustained release of acidic and basic proteins. Our approach involves nucleation and growth of inorganic calcium phosphate mineral coatings on the surface of organic, biodegradable polymer microspheres at near physiologic temperature and pH. This mineral growth process mimics natural biomineralization processes, [10] and results in a mineral coating that is similar in structure (platelike nanostructure) and composition (carbonated-substituted, calcium-deficient hydroxyapatitephase) tohuman bonemineral, asdetailed previouslyon macroscopic polymer films. [11,12] Specifically, protein-releasing,