Study of the fundamental chemical and physical interactions between chitosan and hydroxyapatite

Hydroxyapatite and chitosan are widely used in biomedical applications due to their biocompatibility and biodegradability. Various studies show that composites made of hydroxyapatite and chitosan exhibit desirable properties for applications in bone tissue engineering. When creating a composite it is important to understand the interfacial chemistry and physical interactions between the composite materials. An understanding of these properties gives more insight into the resulting structure of the composite on multiple levels (nano- micro- macro). This structure affects the chemical, physical, and mechanical properties of the material, thus analysis of these properties gives a better understanding of how a material will perform when used in various applications. The goal of this research project was to explore the chemical and physical interactions that occur between hydroxyapatite nanoparticles (HANPs) and the polymer chitosan in a novel nanocomposite. In this project, composites of HANPs and chitosan were synthesized using varying concentrations of the two materials. The composites were analyzed through particle size analysis, Scanning Electron Microscopy (SEM), Dispersive X-ray spectroscopy (EDX), Nuclear Magnetic Resonance spectroscopy (NMR), and X-ray Diffraction (XRD). The results of the study showed mixtures of 10% chitosan and 90% HANPs (dry weight fraction) produce composites with the smallest particle size. The particle size of this composite was then further reduced through chemo-mechanical processing to create a nanocomposite. NMR data suggests that chemical interactions occur between the materials and from analysis of their chemical structures these interactions are most likely hydrogen bonding and coordination bonds. XRD analysis shows a phase change does not occur in the composite after mixing, however there are some phase changes after chemo-mechanical processing.