PH-Responsive biomineralization onto chitosan grafted biodegradable substrates

Bioactive composites that enable the formation of an apatite layer onto the surface are important in the development of osteoconductive biomaterials in orthopaedic applications. In this work, the surface of biodegradable and bioactive substrates, composed of poly(L-lactic acid) (PLLA) reinforced with Bioglass', was modified by coupling chitosan to the surface, using plasma activation. The wettability of the modified films was analysed by contact angle (CA) measurements as a function of pH. It was found that this surface property changed significantly with pH. Moreover, the apatite formation on the surface upon immersion of the modified films in a simulated body fluid (SBF) solution was analysed at pH 5.4 and pH 7.4 by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). It was found that such modification, together with the effect of pH, could block the formation of apatite onto the biodegradable substrate upon immersion in a simulated body fluid solution when the pH changed to 5.4. On the other hand, a dense apatite layer was formed at pH 7.4. For the unmodified substrates an apatite layer was formed at both pHs. These results suggest that the formation of apatite or possibly other kinds of minerals could be controlled by such a smart surface, in this case pH-responsive.