Osteoblast Adhesion and Activity On Biomaterial Surfaces: Influence of Adsorbed Protein

Critical steps toward biomaterial integration include cell adhesion, proliferation, and differentiation. These physiological events are strongly dependent on a material's physicochemical surface properties as well as on the presence and the nature of specific biomolecules coated on the biomaterial and/or present in the cell culture medium. In the present study, we examine MC3T3-E1 osteoblast-like cell behavior (adhesion, proliferation, differentiation) on silicon oxide (SO) and poly(L-lactic acid) (PLA) base materials. We consider the specific role and effects of an adhesive protein, fibronectin (Fn), and a common plasmatic non-adhesive component, albumin (Alb), competitively adsorbed onto the material substrate and/or selectively present in the cell culture medium. We characterize adsorbed protein layers using optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microgravimetry with dissipation (QCMD), and measure cell adhesion / function using a panel of cell biological tests (optical microscopy visualisation, adhesion assays, immunostaining, mitochondrial activity). In terms of initial cell adhesion, no statistical differences are observed between SO and PLA. We observe adsorbed Fn to significantly enhance the percentage of initially adherent cells in culture media containing either Alb alone or within a mixture of serum molecules, and pre-adsorbed Alb to significantly diminish initial adhesion in an Alb-free medium. Cell spreading is greater on SO versus PLA; this difference is minimized in the presence of adsorbed Fn. We observe cell viability to be significantly enhanced i) on PLA versus SO at 7 (but not 1 or 3) days and ii) in the presence of pre-adsorbed Fn. These results demonstrate how substrate and adsorbed protein layer act together to control osteoblastic cell behavior, and suggest biomolecular layers to be an important consideration in the design of biomaterials as implants and/or tissue engineering scaffolds. ->