A comprehensive review on biological and environmental applications of chitosan-hydroxyapatite biocomposites

In the past couple of decades, there has been significant rise in interest towards formulation and application of biomaterials for the purpose of bone-tissue engineering as well as environmental bioremediation. Hydroxyapatite is a bioceramic which has gained much attention in this regard, because it resembles the mineral composition of bone and can be used as bone substitute, teeth filler, or as a coating material on orthopedic and dental implants, etc. On the other side, chitosan is a natural biopolymer that is renowned for its bioactivity, biodegradability, and biocompatibility. Chitosan and hydroxyapatite-based biocomposites have been created and studied for their capacity for biomineralization, mechanical performance, and porous interconnected structure, all of which are highly desired for tissue engineering applications. Together with defluoridation usage, hydroxyapatite has also been identified as a possible material for dye and heavy metal removal, because of its high capacity for adsorption, a low water solubility, and a high level of stability in both oxidizing and reducing conditions. However, due to significant pressure drop, it cannot be employed in powder form or in a fixed bed design. Hence, adding hydroxyapatite to a chitosan matrix improves mechanical strength and increases stability, overcoming its drawbacks. The objective of this review paper is to provide an in-depth analysis of the literature on chitosan-hydroxyapatite based biocomposites having different formulations such as scaffold, hydrogel, nanocomposite, film, powder, etc., and the potential applications of these composites in two important research fields, namely tissue engineering and wastewater bioremediation.