Inorganic-Organic Interfaces in the Synthesis and Performance of Bioceramic Materials

Sandra L. Burkett

Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA Department of Chemistry, Amherst College, Amherst, MA

Traditionally, materials have been selected and developed for biomedical applications on the sole basis of their mechanical properties. However, extent to which a synthetic material will be tolerated by or compatible with a living system is not well- understood or predictable. The physiological response to the presence of a foreign object, such as a biomedical device, is determined by the interactions between biomolecules and the surfaces of the synthetic material. In particular, adsorption of proteins to the surface of the synthetic material is the first step in the sequence of events that constitutes the physiological response, and the adsorbed proteins provide the critical intervening layer through which the material and the cells of the living system interact. In order for a protein to function while adsorbed to a surface, it must be situated not only such that the three-dimensional conformation of amino acids at the active site is retained, but also such that the site is accessible to the external environment.

The primary research goal is to develop a fundamental, molecular-level understanding of the effects of the surface chemistry and topology of ceramic materials on the conformation, orientation, and spatial arrangement of adsorbed proteins. Although the sub-nanometer-sized pores of zeolites have been used as hosts for the preparation of ordered arrays of organic molecules, the periodicity of zeolite surfaces has not previously been exploited for the formation of ordered arrays of molecules that are too large to fit inside the zeolite pores. In the present work, interactions between zeolites and structurally well-defined polypeptides provide a model system for systematic study of the effects of surface chemistry and topology on protein adsorption. A series of zeolites has been prepared such that surface geometry and surface chemical composition are varied systematically and independently, and the effects of each of these parameters on protein adsorption have been studied at the molecular level. Results from these studies are relevant to a variety of applications that involve proteins adsorbed on ceramic surfaces, including biocatalysis and biosensing using immobilized enzymes, protein chromatography, surface-induced protein crystallization, drug and vaccine delivery on ceramic supports, and biocompatible ceramic materials.