Restricted cell functions on micropillars are alleviated by surface-nanocoating with amino groups

Abstract

The topographical and chemical surface features of biomaterials are sensed by the cells, affecting their physiology at the interface. On titanium we recently discovered an attempted caveolae-mediated phagocytosis of the sharp-edged microstructures by osteoblasts. This active, energy-consuming process resulted in decreased osteoblastic cell functions, e.g. extracellular matrix proteins. However, chemical modification with plasma polymerized allylamine (PPAAm) was able to amplify osteoblast adhesion and spreading, resulting in better implant osseointegration in vivo. In the present in vitro study we analyzed whether this plasma polymer nanocoating is able to attenuate the microtopography-induced changes of osteoblast physiology. On PPAAm we found a higher cell interaction with the geometrical micropillars already after 30 min, and a less distinct reduction in the mRNA expression of collagen type I, osteocalcin and fibronectin after 24 h of cell growth. Interestingly, the cells are more active and sensitive on PPAAm-coated micropillars and react with an impressive calcium ion mobilization after stimulation with adenosine triphosphate (ATP). These results highlight the importance of the osteoblasts establishment of cell-surface contact for the manifestation of their cell function.