Effect of surface morphology of calcium phosphate on osteoblast-like HOS cell responses

Abstract

Calcium phosphate (CaP) films with different surface roughness are synthesized on a polystyrene surface as a possible candidate for improving the biocompatibility of solid surfaces. These CaP films are used to investigate the influences of the surface roughness and chemical composition on the HOS osteoblast-like cells adhesion, spreading, proliferation, and differentiation. A polystyrene culture plate is used as the control surface. The CaP substrates are designated as a smooth, moderate, and rough surface according to the surface roughness. For smooth and moderate surfaces, a relatively small difference in the surface roughness is observed but the difference in their chemical composition is more significant than the others. Cell adhesion, spreading, proliferation, and differentiation appear to be dependent on surface roughness. These cellular responses are more active on the smoother surfaces than on the rough surface but are more pronounced on the moderate surface. The cell responses are reduced when HOS cells are cultured on the rough surface. The number of cells released from the control surface by trypsinization is greater than the CaP surfaces after a short period of incubation (5 h). However the cells released from smooth and moderate CaP surfaces are equivalent to or greater than the control at the longer period of incubation (17 h). Spreading and proliferation are greater on the CaP surfaces than on the control. The alkaline phosphatase-specific activity is very low during 1 and 2 weeks of culturing but dramatically increases after 3 weeks on all surfaces. The enzyme activity on the control is greater than on the CaP surfaces. The moderate surface shows the greatest enzyme activity in all cases among the CaP surfaces. Although a direct relation between surface chemistry and cell responses has not been established, the surface composition may play a cooperative role in characterizing the cellular responses. According to these results, the moderate surface is the most favorable substrate in terms of surface roughness and chemical composition for cell adhesion, spreading, proliferation and differentiation among all the CaP surfaces.