Effect of acid molecules on biomimetic mineralisation of calcium phosphate and carbonate within biopolymer films using small angle neutron scattering

Abstract

This study investigates the mineralisation calcium phosphate (CaP) and carbonate (CaCO3) within chitosan/iota-carrageenan multilayer films using a simulated body fluid (SBF) and simulated sea-water (SSW), respectively. Small angle neutron scattering measurements were taken on a range of mineralisation conditions including exposure time (0.5, 3 and 18 h), Ca2+:carboxylic acid molecule molar ratio (1:1, 1000:1) and the type of acid molecule (l-glutamic acid, citric acid and poly(acrylic acid). The modelling of the SANS data was used to obtain two physical parameters indicative of the extent of mineralisation, SANS power law slope and the lamellar neutron scattering density within the multilayer biopolymer film. Mineralisation of CaCO3 within these templates was enhanced with the addition of each of the acid molecules. However, no obvious trend could be found in relation to extent of exposure time or concentration. The enhanced CaCO3 mineralisation was also observed using in-situ ellipsometry at the solid-liquid interface of a 2-bilayer chitosan/iota-carrageenan film. Thickness increase rates as high as 5.3 nm min−1 were observed for the acid molecule containing SSW compared to a rate of 2.3 nm min−1 in the SSW not containing acid molecules.