Hydrophobicity, surface tension, and zeta potential measurements of glass-reinforced hydroxyapatite composites

Wettability and zeta potential studies were performed to characterize the h ydrophobicity, surface tension, and surface charge of P2O5-glass-reinforced hydroxyapatite composites. Quantitative phase analysis was performed by th e Rietveld method using GSAS software applied to X-ray diffractograms. Surf ace charge was assessed by zeta potential measurements. Protein adsorption studies were performed using vitronectin. Contact angles and surface tensio ns variation with time were determined by the sessile and pendent drop tech niques, respectively, using ADSA-P software. The highest (-18.1 mV) and low est (-28.7 mV) values of zeta potential were found for hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), respectively, with composite mate rials presenting values in between. All studied bioceramic materials showed similar solid surface tension. For HA and beta-TCP, solid surface tensions of 46.7 and 45.3 mJ/m(2), respectively, were obtained, while composites pr esented intermediate surface tension values. The dispersive component of su rface tension was the predominant one for all materials studied. Adhesion w ork values between the vitronectin solution and HA and beta-TCP were found to be 79.8 and 88.0 mJ/m(2), respectively, while the 4.0 wt % glass composi tes showed slightly lower values than the 2.5 wt % ones. The presence of P- TCP influenced surface charge, hydrophobicity, and protein adsorption of th e glass-reinforced HA composites, and therefore indirectly affected cell-bi omaterial interactions. (C) 1999 John Wiley & Sons, Inc.