Cellular responses to chemical and morphologic aspects of biomaterial surfaces. I. A novel in vitro model system

The clinical success of any implant is directly dependent upon the cellular behavior in the immediate vicinity of the interface established between the host tissue and the biomaterial(s) used to fabricate the device. All biomaterials have morphologic, chemical, and electrical surface characteristics that influence the cellular response to the implant. Quantitative measurement of specific aspects of this local host response to different but well-characterized biomaterial surfaces provides a crucial link in the understanding of the overall phenomenon of implant biocompatibility. A system has been devised for in vitro examination of responses of cells to controlled but independent changes in both the chemistry and morphology of polystyrene (PS) tissue culture surfaces. Micromachined silicon wafers were used as templates to solvent-cast PS replicas [using 0, 1, or 2 wt % styrene (S) monomer additions] with either none, 0.5- or 5.0-microns-deep surface grooves arranged in a radial array. When all possible morphologies were combined with all possible polymers, nine model biomaterial surfaces (MBSs) were produced. The chemical characteristics of the MBSs were determined using electron spectroscopy for chemical analysis, secondary ion mass spectroscopy, and contact angle techniques and were found to be distinct. The types and amount of proteins that adsorb onto these surfaces from serum containing media were examined and found to consist of multiple molecular layers of relatively uniform composition. Self-contained tissue culture vessels formed from the MBSs were capable of supporting the growth of confluent cultures of rat calvarial cells. The model biomaterial system described here can be used to examine how simultaneous stimuli resulting from the chemical and morphological characteristics of a test material may influence biologic responses. Such multifactorial biocompatibility research is needed to properly document material-host interactions.