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The mismatch between the mechanical properties of bioceramics and natural tissue has restricted in several cases a wider application of ceramics in medical and dental fields. To overcome this problem, polymer matrix composites can be designed to combine bioactive properties of some bioceramics with the superior mechanical properties of some engineering plastics. In this work, polymer particulate composites composed of a high mechanical-property polymer and bioactive glass particles were produced and both the in vitro bioactivity and properties of the system were investigated. Composites with different volume fraction and particle size were prepared. In vitro tests showed that hydroxy-carbonate-apatite can be deposited on the surface of a composite as early as 20 h in a simulated body fluid. Ionic evolution from a composite with 40% volume fraction of particles was demonstrated to be similar to bulk bioactive glasses. The mechanical properties of some of the obtained composites had values comparable with the ones reported for bone. Moreover, a physical model based on dynamical mechanical tests showed evidences that the interface of the composite was aiding in the stress transfer process.

A research program was initiated with both experimental and computational chemistry based molecular modeling components to investigate specific amino acid-surface interactions. The experimental portion of this study, with details reported elsewhere, investigated the adsorption of selected molecular weights of poly(L-lysine) onto silica glass microspheres with the adsorption enthalpy per adsorbed mer determined to be -0.23 +/- 0.13 kcal/mol (mean +/- 95% confidence interval). Molecular modeling of this system was then conducted using two approaches: an AM1 semiempirical molecular orbital method to predict L-lysine/glass interaction energy and an MM2 molecular mechanics method to investigate the structural configuration for poly(L-lysine). The modeling predicted a minimum energy configuration of a rotational backbone structure for poly(L-lysine) with approximately one full rotation occurring about every 8 mers, and that the amine side chains of the L-lysine will hydrogen bond with the silica surface with an average adsorption energy of approximately -0.34 kcal/mol/mer. The molecular modeling results are in good agreement with the experimentally measured value and provide insights into possible molecular-level behavior which would be very difficult to determine by experimental analyses alone. This work demonstrates the use of molecular modeling in conjunction with experimental studies to investigate complex molecular interactions.

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