This study examines zein protein-induced growth of calcium phosphate (CaP) thin films at air-liquid interfaces. The results demonstrate that zein protein films in contact with simulated body fluids (SBF) promote the growth of hemispherical CaP particles of 150 nm radius, which combine to form a film. The CaP films formed on zein were less continuous than those obtained using a hexadecanoic acid monolayer self-assembled at the air-liquid interface. In situ ellipsometry measurements were used to follow the nucleation and growth of CaP in these systems. The kinetic parameters extracted from the ellipsometry data were dependent on the organic layer and also the SBF concentration. The mineralisation process was slower and final CaP film thicknesses smaller when zein films were used. XPS analyses revealed the presence of zein protein only on the air-facing side of the CaP films, confirming that the zein protein is involved in nucleating the unusual hemispherical CaP morphology. The zein protein-induced CaP thin films showed iridescence with a distinct range of colours as a function of CaP film thickness. Templated CaP mineralisation with zein protein is a simple and chemically facile method for synthesising CaP films with novel morphologies and controllable thicknesses. Fig. 4 Mineralisation profiles obtained by ellipsometry showing the CaP thickness under zein protein and hexadecanoic acid (HDA) films using 1Â and 2Â SBF concentrations. Dashed lines show growth rate, calculated using the first derivative.

Bone strength in human cortical bone is determined by the composition and structure of both the mineral and collagen matrices and influenced by factors such as age, gender, health, lifestyle and genetic factors. Age-related changes in the bone matrix are known to result in loss of mechanical strength and increased fragility. In this study we show how Raman spectroscopy, with its exquisite sensitivity to the molecular structure of bone, reveals new insights into age- and sex-related differences. Raman analysis of 18 samples of cortical hip bone obtained from people aged between 47–82 years with osteoarthritis (OA) found subtle changes in the lipid and collagen secondary structure, and the carbonate (CO32−) and phosphate (PO43−) mineral ratios in the bone matrix. Significant differences were observed between older and younger bones, and between older female and older male bones; no significant differences were observed between younger male and female bones. Older female bones presented the lowest mineral to matrix ratios (MMR) and highest CO32−/PO43− ratios, and relative to lipid/collagen –CH2 deformation modes at 1450 cm−1 they had lowest overall mineral content, higher collagen cross linking and lipid content but lower levels of α-helix collagen structures than older male and younger male and female bones. These observations provided further insight on bone composition changes observed in the bone volume fraction (BV/TV) for the older female bones from microCT measurements on the same samples, while tissue mineral density (TMD) measurements had shown no significant differences between the samples.

This work systematically explores the biomineralization of calcium phosphate (CaP) and carbonate (CaCO) within chitosan/iota-carrageenan multilayer films. Multilayer films of chitosan and iota-carrageenan (up to 128-coupled layers) were prepared on glass substrates by a layer-by-layer dip-coating technique. Cryo-scanning electron microscopy revealed dense interfaces between the chitosan and iota-carrageenan layers with thicknesses in the range 250 and 350 nm in the hydrated state, accounting for the iridescent nature of multilayer films when wet. Immersion of the multilayered films in simulated body fluid or simulated seawater at 25 °C resulted in the mineralization of CaP and CaCO, respectively, at the interfaces between the biopolymer layers and modified the iridescence of the films. Lamellar scattering features in small-angle neutron scattering measurements of the mineralized films provided evidence of the localized mineralization. Further evidence of this was found through the lack of change in the dynamic and static correlation lengths of the polymer networks within the bulk phase of the chitosan and iota-carrageenan layers. CaP mineralization occurred to a greater extent than CaCO mineralization within the films, evidenced by the higher lamellar density and greater rigidity of the CaP-mineralized films. Results provide valuable new insights into CaP and CaCO biomineralization in biopolymer networks.