Nano-scale manipulation of silicate-substituted apatite chemistry impacts surface charge, hydrophilicity, protein adsorption and cell attachment

Abstract

This study characterised the effect of nano-scale variation in hydroxyapatite (HA) surface-chemistry, by manipulation of silicate substitution level, on surface charge, hydrophilicity, protein adsorption and cell attachment. Substitution with 0.4 wt% Si (SA04) had a significant impact on surface charge, but did not affect hydrophilicity as compared to stoichiometric HA. Increasing silicon content to 0.8 wt% (SA08) did not alter surface charge, but significantly increased hydrophilicity as compared to SA04. A silicon content of 1.5 wt% (SA15) significantly altered surface charge but showed no statistical variation in hydrophilicity as compared to SA08. Study of both competitive (serum) and single (fibronectin) protein adsorption, in addition to osteoblast-like cell attachment, demonstrated increased protein adsorption and cell attachment on SA08. In contrast protein adsorption to SA04 and SA15 showed equivalent to intermediate behaviour while cell attachment demonstrated impaired to equivalent performance as compared to HA. This data indicates that the enhanced bioactivity of SA08 may be related to the influence that surface physiochemical characteristics have on its interaction with serum proteins.