Development of nanocomposites based on hydroxyapatite/sodium alginate: Synthesis and characterisation

In this study, a novel method was used to produce a nanostructured composite consisting of hydroxyapatite and sodium alginate by varying the composition of sodium alginate. The structure, morphology, simulated body fluid response and mechanical properties of the synthesised nanocomposites were characterised. From X-ray diffraction analysis, an increase in crystallite size and degree of crystallinity with an increase in the composition of sodium alginate up to 1.5 wt.% was observed. Further, it was found to decrease with an increase in the composition of sodium alginate. A notable peak shift from 1635 to 1607 cm− 1 and 1456 to 1418 cm− 1 in the Fourier transform infrared spectra of the nanocomposite was observed towards the lower wave number side when compared with pure hydroxyapatite. It reveals a strong interaction between the positively charged calcium (Ca2+) and the negatively charged carboxyl group (COO−) in sodium alginate. Transmission electron microscopy images of pure hydroxyapatite showed a short nanorod-like morphology with an average particle size of 13 nm. Bioresorbability of the samples was observed by immersing them in simulated body fluid medium for 14 days to evaluate the changes in pH and Ca2+ ion strength. Microhardness shows an increasing trend with an increase in the composition of sodium alginate from 1.5 to 3.0 wt.%, which is similar to that in the density.