Biofunktionalität von Biomaterialien im Knochenkontakt — Neue prädiktive Parameter auf molekularbiologischer Grundlage

Cell adhesion to biomaterials is one of the key determinators of biocompatibility and biofunctionality of these materials in vivo. Integrin-mediated signaling has emerged as one of the fundamental pathways during cell-cell and cell-matrix interactions. In this study we wanted to determine whether some of the molecules involved during these signaling processes could serve as quantitative and more accurate markers of biocompatibility in vitro and possibly play their part in a screening assay during biomaterial evaluations for their potential as scaffolds or temporary tissue substitutes. We used osteoblasts (MC3T3-El) on various protein-coated and uncoated biomaterials such as polystyrene and two clinically well-known titanium and steel alloys and measured cellular paxillin tyrosine phosphorylation (protein level) and c-fos gene expression (mRNA level) following 60 min of adhesion. Paxillin tyrosine phosphorylation increased 2.5-fold on protein-coated vs. uncoated charged polystyrene (p < 0.05), but was not altered on uncharged polystyrene. C-fos expression levels showed differences (up to 5-fold) on charged and uncharged polystyrene surfaces. Both parameters showed a clearly significant (5-fold) increase on titanium vs. steel alloy and thus resembled the clinically well-known better biocompatibility of titanium in the vicinity of bone. We conclude that among other molecular parameters yet to be determined, paxillin tyrosine phosphorylation and c-fos expression can serve as in vitro screening parameters for a biomaterial’s projected Performance in vivo. We are currently developing tools to monitor several hundred molecular parameters within a cell at once to gain a better understanding of osteoblast adhesion to biomaterials in general and to screen for materials with higher biofunctionality in an in vivo Situation.