Hydroxyapatite (HAp) has significant biological activity, degradability, and osteoconductivity. In recent decades, it has been widely used in dentistry, anti-tumour drug carriers, and orthopaedic repair. However, hydroxyapatite has limit features which are poor mechanical properties for directly inducing tooth enamel remineralization, particle size and morphology issues on drug delivery and brittleness for bone transplantation. This article summarizes the problems encountered in the preparation, application, and modification of hydroxyapatite in the above-mentioned fields and the current research progress, combining theory with experiment. Therefore, the greatest significance of this review is to comprehensively integrate and argue the forms and effects of nHA-based biomaterials, which provides a theoretical basis for the application of this material and help readers have clear insights into future research.

Recent advances in biomedical engineering of nano-hydroxyapatite including dentistry, cancer treatment and bone repair

Advances in ultra high molecular weight polyethylene/hydroxyapatite composites for biomedical applications: A brief review.

Structure, apatite inducing ability, and corrosion behavior of chitosan/halloysite nanotube coatings prepared by electrophoretic deposition on titanium substrate.

The present study focuses on simultaneous influence of graphene nanoplatelets (GNP) and hydroxyapatite (HAp) nanopowder on microstructural, wear, tensile and biofunctional behavior of UHMWPE based nanocomposites used in biomedical applications, with the aim to utilize GNP's mechanical strength and wear resistance, while benefitting from HAp's biocompatibility at the same time. 0.1, 0.5 and 1 wt% GNP with 10 wt% optimized concentration of HAp were added to the UHMWPE matrix through an easy two-step approach consisting of solvent mixing and ultrasonication in ethanol as a liquid media. The dried nanocomposite samples of powder were then hot pressed at an optimized temperature and pressure to ensure complete melting and flowing of the polymeric material. Tensile testing results indicated a 114% & 24% increase in elastic modulus and yield strength in the sample containing 1 wt% GNP and 10 wt% HAp, respectively, as compared to UHMWPE. However, the sample containing 0.5 wt% GNP showed greatest tensile performance with an increase of 101% and 31% improvement in elastic modulus and yield strength, which proves that the strengthening mechanism is influenced by the content of the reinforcement, especially in case of 2D reinforcing phases such as GNP. Microstructural analysis revealed the nucleating effect of GNPs on the crystalline structure of UHMWPE, to which the escalated mechanical properties could be attributed. Furthermore, the assessments disclosed the dependency of nucleating, and in consequence strengthening effect of GNPs to their concentration and apparent clustering threshold. Moreover, pin-on-disk tribological testing results showed a somewhat similar result for the coefficient of friction, which decreased by 50% with 1 wt% GNP, while the similar parameter for the sample containing 0.5 wt% GNP underwent 54% reduction. Whereas a steady decreasing pattern was observed in the case of wear rate with an 82% decrease in the sample containing 1 wt% GNP, coming to a conclusion that GNP is much more effective in improving wear properties rather than in mechanical strengthening. Biological examinations also demonstrated that HAp promises biocompatibility, osteoconductivity and the elimination of adverse cellular response, while cell adhesion was still dependent on the concentration and was affected adversely with increasing GNP. This destructive biological effect of GNPs was seemingly attributed to the functional groups of the material, or to the inherent edge-shaped structure by means of FTIR, wettability and compaction analyses.

Optimizing tribological, tensile & in-vitro biofunctional properties of UHMWPE based nanocomposites with simultaneous incorporation of graphene nanoplatelets (GNP) & hydroxyapatite (HAp) via a facile approach for biomedical applications

Medical engineering advances in total joint replacements and societies’ rising demand for long-lasting materials have proven it essential to manufacture materials that are more similar to the original tissue in the fields of mechanical, tribological, and biological properties. Ultra-high molecular weight polyethylene (UHMWPE) is a polymer widely used in arthroplasty applications due to its biocompatibility, chemical stability, and reasonable mechanical properties; however, it still fails to entirely meet the standards of the hip joint implant. In this study, different concentrations of nanosized zirconia were added to UHMWPE and HAp matrix with an intended application in arthroplasty. Liquid-phase ultrasonication and hot pressing were employed to disperse the reinforcing phases and to form the final standard samples, respectively. Tensile, Vickers hardness, and pin-on-disk tests were carried out to evaluate mechanical and wear properties of the samples. In the meanwhile, in vitro biological properties were studied via MTT assay, alkaline phosphatase enzyme activity, and cell morphology tests. Dispersion features, microstructural structures, and cell adhesion were also assessed using scanning electron microscopy (SEM). Results indicate improvement in both tensile and wear properties by zirconia addition; for instance, the sample containing 10 wt% zirconia and 10 wt% HAp exhibits 45% increase in yield strength and 64% reduction in coefficient of friction. On the other hand, biological properties have also significantly improved with zirconia incorporation, at which all samples proved to be biocompatible with an increase in both osteoblasts activity and cell adhesion with increasing zirconia concentration.

Improved wear, mechanical, and biological behavior of UHMWPE-HAp-zirconia hybrid nanocomposites with a prospective application in total hip joint replacement

Ultrahigh molecular weight polyethylene–based nanocomposites reinforced with nano-sized hydroxyapatite particles were fabricated using internal mixer and compression molding with different weight percent of the nano-hydroxyapatite. In this study, first, hydroxyapatite nanoparticles were synthesized by sol–gel. Then, the mechanical and biological properties of nanocomposites were studied by tensile test and proliferation and cell adhesion assays using MG-63 osteoblast cells, respectively. Results of the tensile test showed that incorporation of 50 wt% nano-hydroxyapatite led to a 345.64% and 57.58% increase in Young's modulus and yield strength (compared to the pure ultrahigh molecular weight polyethylene), respectively. The effect of the nano-hydroxyapatite powders on the MG-63 osteoblast cells behavior was compared to those of a composite (positive control) and a negative control samples. Scanning electron microscopy micrographs revealed that cell–biomaterial interaction was carried out on the surface of...

Mohammadali Sattari

Papers

Tensile and biocompatibility properties of synthesized nano-hydroxyapatite reinforced ultrahigh molecular weight polyethylene nanocomposite: