Development of Bone-Like Nano Hydroxyapatite-Chitosan Composites for an Enhanced Bone Fixation

Abstract

The composite nature of bone inspires biomedical scientists to fabricate materials that can be used for partial or total replacement of defective bone. Bone is composed of collagen nanofibers that are further reinforced by hydroxyapatite (HAp) nanocrystallites. The chemical and mechanical interlooking between HAp and the collagen fibers provides the unique biomechanical properties of natural bone. HAp has a generic stoichiometric formula of Ca(10-x)(HPO4)x(PO4)(6-x)(OH)(2-x) with x:0-1. This provides a range of HAp structures with stoichiometric (1.67) and nonstoichiometric (1.5 -<1.67). Formation of HAp in nature takes place through a mineralization process where HAp nuclei deposit onto specific functional groups along the collagen fibers. These functional groups include –COO

H, -OH, -NH2, and –SO3H. In order to mimic the natural mineralization process, the current study investigates the mineralization of a biocompatible natural polymer (chitosan; CS) through the growth of HAp nanocrystallites with different degrees of stoichiometry (Ca/P: 1.5, 1.6, 1.67). Additionally, two (2) different molecular weights of naturally obtained CS will be used; designated as low and high molecular weights. The main aim of the study is to mimic the natural process of bone formation via the growth of HAp onto chitosan. In addition, the effect of varying the Ca/P molar ratio of the HAp precursors, the molecular weight of CS and its proportion, on the structure and morphology of the obtained bone-like composite will be investigated using x-ray diffraction, infrared spectroscopy, thermal analysis, size and surface properties, physical properties (texture, porosity, and pore size distribution), and scanning as well as transmission electron microscopies. Thermally-treated HAp-CS bodies will be further evaluated in terms of their mechanical properties and in vitro using a generic MC3T3 cell culture experiments to test the suitability of the HAp-CS composites to be used for the fixation and partial replacement of defective bone.

Date of Award	Apr 2023
Original language	American English
Supervisor	KINDA Khalaf (Supervisor)