In vitro mineralisation of chitosan membranes carrying phosphate functionalities

Squid chitosan membranes were phosphorylated through the H3PO4/P2O5/Et3PO4/butanol method. P-chitosan membranes were immersed in Ca(OH)(2) or NaOH solutions, in order to obtain the Na or the Ca salts, respectively. These materials were investigated regarding their ability to nucleate calcium phosphates, under simulated physiologic conditions. SEM-EDS studies revealed the presence of a calcium phosphate mineral layer all over the surface of P-chitosan membranes, after incubation in Ca(OH)(2) solution. The release of ionically bound phosphate functionalities under alkaline conditions, possibly contributed to the formation of calcium phosphate precursor sites, due to the chelation of calcium ions from solution. During the immersion in Simulated Body Fluid (SBF), a multilayer porous mineral structure composed of poorly crystalline carbonated apatite was formed on the surface of these membranes, as shown by EDS and ATR-FTIR analysis. Unmodified membranes and P-chitosan membranes pre-incubated in NaOH solution did not mineralise.