Synthesis and Biological Properties of Alanine-Grafted Hydroxyapatite Nanoparticles

Surface Modification of Nano-Hydroxyapatite/Polymer Composite for Bone Tissue Repair Applications: A Review

Nano-hydroxyapatite (n-HA) is the main inorganic component of natural bone, which has been widely used as a reinforcing filler for polymers in bone materials, and it can promote cell adhesion, proliferation, and differentiation. It can also produce interactions between cells and material surfaces through selective protein adsorption and has therefore always been a research hotspot in orthopedic materials. However, n-HA nano-particles are inherently easy to agglomerate and difficult to disperse evenly in the polymer. In addition, there are differences in trace elements between n-HA nano-particles and biological apatite, so the biological activity needs to be improved, and the slow degradation in vivo, which has seriously hindered the application of n-HA in bone fields, is unacceptable. Therefore, the modification of n-HA has been extensively reported in the literature. This article reviewed the physical modification and various chemical modification methods of n-HA in recent years, as well as their modification effects. In particular, various chemical modification methods and their modification effects were reviewed in detail. Finally, a summary and suggestions for the modification of n-HA were proposed, which would provide significant reference for achieving high-performance n-HA in biomedical applications.

Are hydroxyapatite-based biomaterials free of genotoxicity? A systematic review

Hydroxyapatite (HA) is a biomaterial widely used in clinical applications and pharmaceuticals. The literature on HA-based materials studies is focused on chemical characterization and biocompatibility. Generally, biocompatibility is analyzed through adhesion, proliferation, and differentiation assays. Fewer studies are looking for genotoxic events. Thus, although HA-based biomaterials are widely used as biomedical devices, there is a lack of literature regarding their genotoxicity. This systematic review was carried out following the PRISMA statement. Specific search strategies were developed and performed in four electronic databases (PubMed, Science Direct, Scopus, and Web of Science). The search used "Hydroxyapatite OR Calcium Hydroxyapatite OR durapatite AND genotoxicity OR genotoxic OR DNA damage" and "Hydroxyapatite OR Calcium Hydroxyapatite OR durapatite AND mutagenicity OR mutagenic OR DNA damage" as keywords and articles published from 2000 to 2022, after removing duplicate studies and apply include and exclusion criteria, 53 articles were identified and submitted to a qualitative descriptive analysis. Most of the assays were in vitro and most of the studies did not show genotoxicity. In fact, a protective effect was observed for hydroxyapatites. Only 20 out of 71 tests performed were positive for genotoxicity. However, no point mutation-related mutagenicity was observed. As the genotoxicity of HA-based biomaterials observed was correlated with its nanostructured forms as needles or rods, it is important to follow their effect in chronic exposure to guarantee safe usage in humans.

Study on a co-hybrid nano-hydroxyapatite with lignin derivatives and alendronate and the reinforce effect for poly(lactide-co-glycolide)

A novel co-hybrid nano-apatite (n-HA) by introducing lignin derivatives (LDs) and alendronate (ALE) was designed to reinforce poly(lactide-co-glycolide) (PLGA). The effect of different addition methods and contents of LDs, lignin derivatives sorts of lignosulfonate (LS), alkali lignin (AL) and carboxymethyl lignin (CML), and the addition order of ALE on the dispersion of hybrid n-HA, and reinforce effective for PLGA were investigated by FTIR, XRD, TEM, TGA, XPS, N2 adsorption/desorption, zeta potential, dispersion experiments, universal testing machine, SEM, DSC and POM. The results showed that the addition order could regulate the growth of n-HA crystal planes by binding with Ca2+, and co-hybrid HA by LDs and ALE possessed better dispersion owing to the synergistic effect. Moreover, 10 wt% LS-ALE-n-HA displayed the best reinforce effect, and the tensile strength of composite was 24.43 % higher than that of PLGA, even 15 wt% LS-ALE-n-HA was added, it still exhibited reinforce effect for PLGA. In vitro soaking in simulated body fluid (SBF) results indicated that LS-ALE-n-HA delayed tensile strength reduce of PLGA and promoted bone-like apatite deposition. The cell proliferation results demonstrated that the hybrid n-HA by the introduction of ALE endowed PLGA with better cell adhesion and proliferation.

Additive manufacturing of poly (lactic acid)/hydroxyapatite/carbon nanotubes biocomposites for fibroblast cell proliferation

Bone tissue is one of the most important in the human body. In this study, scaffolds of poly (lactic acid) PLA reinforced with hydroxyapatite (HA) and carbon nanotubes (CNT) were manufactured, evaluating their mechanical and biological properties. HA was synthesized by wet method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The scaffolds were produced using additive manufacturing and characterized by optical microscopy, SEM, thermogravimetric analysis (TGA), Raman spectroscopy and biological tests. The SEM results showed that the PLA surface was affected by the incorporation of CNT. TG showed that the incorporation of HA into the polymer matrix compromised the thermal stability of PLA. On the other hand, the incorporation of CNT to the polymer and the impregnation with HA on the surface by thermal effect increased the stability of PLA/CNT scaffolds. Raman spectra indicated that HA impregnation on the surface did not modify the polymer or the ceramic. In the compression tests, PLA and PLA/CNT scaffolds displayed the best compressive strength. In the biological tests, more than 85% of the cells remained viable after 48 h of incubation with all tested scaffolds and groups with CNT in the composition disclosing the best results.