Formation of hydroxyapatite coating using novel chemo-biomimetic method

Current Challenges and Innovative Developments in Hydroxyapatite-Based Coatings on Metallic Materials for Bone Implantation: A Review

Biomaterials are in use for the replacement and reconstruction of several tissues and organs as treatment and enhancement. Metallic, organic, and composites are some of the common materials currently in practice. Metallic materials contribute a big share of their mechanical strength and resistance to corrosion properties, while organic polymeric materials stand high due to their biocompatibility, biodegradability, and natural availability. To enhance the biocompatibility of these metals and alloys, coatings are frequently applied. Organic polymeric materials and ceramics are extensively utilized for this purpose due to their outstanding characteristics of biocompatibility and biodegradability. Hydroxyapatite (HAp) is the material from the ceramic class which is an ultimate candidate for coating on these metals for biomedical applications. HAp possesses similar chemical and structural characteristics to normal human bone. Due to the bioactivity and biocompatibility of HAp, it is used for bone implants for regenerating bone tissues. This review covers an extensive study of the development of HAp coatings specifically for the orthopaedic applications that include different coating techniques and the process parameters of these coating techniques. Additionally, the future direction and challenges have been also discussed briefly in this review, including the coating of HAp in combination with other calcium magnesium phosphates that occur naturally in human bone.

Fabrication of chitosan/hydroxylapatite composite rods with a layer-by-layer structure for fracture fixation

A composite rod for fracture fixation using chitosan (CHI)/hydroxylapatite (HA) was prepared by means of in situ precipitation, which had a layer-by-layer structure, good mechanical properties, and cell compatibilities. The CHI/HA composite rods were precipitated from the chitosan solution with calcium and phosphorus precursors, followed by treatment with a tripolyphosphate-trisodium phosphate solution (pH >13) to crosslink the CHI and to hydrolyze the calcium phosphates to nanocrystalline HA. The results of FTIR, XRD, and TEM measurements confirmed that HA had been formed within the CHI matrix. The effects of the CHI/HA ratios (20/0, 20/1, 20/2, 20/4, and 20/5, w/w) on the mechanical properties were investigated. At the CHI/HA ratio of 20/4 (w/w), the bending strength and modulus of the rods were 133 MPa and 6.8 GPa, respectively. Pre-osteoblast MC3T3-E1 cells were cultured in an extract of the CHI/HA rods (20/4, w/w) to study the cell compatibilities of the composite. The observations indicated that the CHI/HA composite could promote the growth of MC3T3-E1 cells better than the composite without HA (p < 0.05). Furthermore, the co-cultivation of the cells and the CHI/HA composite showed that cells fully spread on the surface of the composite with an obvious cytoskeleton organization, which also revealed that the CHI/HA composite had a good biocompatibility.