A review on bovine hydroxyapatite; extraction and characterization

Oxidative hydrothermal treatment of bovine bones: A lower CO2 emission process to obtain high specific surface area hydroxyapatite

Hydroxyapatite (HA) is known to be the main component of the mineral part of bones. Due to its properties HA is studied for various applications such as bone graft, drug carrier, heterogeneous catalyst or sorbent for waste water treatment. HA can be synthesized or valorized from bone wastes, as the food industry produce billions of kilograms of animal bones. The oxidative hydrothermal treatment presented in this work offers an alternative to the conventional calcination in order to remove the organic matter contained in bones. The impact of adding dioxygen into the hydrothermal system on the degradation of organic matter was studied by varying the partial O2 pressure from 0 to 30 bar. In addition, the influence of temperature (220, 250, and 280 °C) and dwelling time (0 and 2 h) at these temperatures was investigated. The degradation of the organic matter was proved by TGA-DSC and FTIR. The presence of organic compounds dissolved in water was assessed by TOC measurements and the production of CO2 was followed by Raman spectroscopy. A hydroxyapatite powder with an organic content <1 wt% has been successfully recovered at a lower temperature, for a shorter duration and with a lower production of CO2 compared to calcination. In addition, the recovered HA has a much higher specific surface area (up to 164 m2/g) compared to calcined bones (up to 83.1 m2/g), which is favorable for biomedical and sorbent applications.

Natural hydroxyapatite-based nanobiocomposites and their biomaterials-to-cell interaction for bone tissue engineering

Hydroxyapatite (HA) is an extensively used biomaterial for dental and orthopaedic applications because of its biocompatibility and biomimetic nature. HA is extensively used as a bone-graft substitute. HA bone graft substitutes of bovine or synthetic origins have been extensively studied. However, caprine-based HA has not been explored. In this study, we aimed to determine the utilization of goat bone-derived HA for commercial applications. HA from caprine bone and teeth was isolated using thermal calcination. The developed HA can be used as a bone graft substitute. Chemical characterization of the isolated HA was carried out using Fourier transform infrared spectroscopy, X-Ray Diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The biocompatibility and apatite formation of isolated HA were assessed using MG-63 cells, MC3T3-E1, L929 cells, MSCs, adipose derived stem cells, human dermal tissue derived fibroblast cells and osteoblast-like cell line, The studies demonstrate that HA support cell adhesion and osteogenic properties. To improve sheep, lamp, or caprine bone-derived HA, several other composites have been developed with MgO2, ZrO2, ZnO2, and other polymeric substances. 3D printed technology was used to develop a bioink using sheep-derived HA and printed the composite scaffold as a bone graft substitute. Furthermore, the biomedical applications of sheep-derived HA been studied in terms of their antimicrobial activity, bone-forming ability, and wound healing applications. Sheep-, goat-, and caprine-derived HA are still underutilized and require further research to develop commercial possibilities and sustainable raw materials for HA-based bone graft substitutes.

A Comparative Study of HA/DBM Compounds Derived from Bovine and Porcine for Bone Regeneration

This comparative study investigated the tissue regeneration and inflammatory response induced by xenografts comprised of hydroxyapatite (HA) and demineralized bone matrix (DBM) extracted from porcine (P) and bovine (B) sources. First, extraction of HA and DBM was independently conducted, followed by chemical and morphological characterization. Second, mixtures of HA/DBM were prepared in 50/50 and 60/40 concentrations, and the chemical, morphological, and mechanical properties were evaluated. A rat calvarial defect model was used to evaluate the tissue regeneration and inflammatory responses at 3 and 6 months. The commercial allograft DBM Puros® was used as a clinical reference. Different variables related to tissue regeneration were evaluated, including tissue thickness regeneration (%), amount of regenerated bone area (%), and amount of regenerated collagen area (%). The inflammatory response was evaluated by quantifying the blood vessel area. Overall, tissue regeneration from porcine grafts was superior to bovine. After 3 months of implantation, the tissue thickness regeneration in the 50/50P compound and the commercial DBM was significantly higher (~99%) than in the bovine materials (~23%). The 50/50P and DBM produced higher tissue regeneration than the naturally healed controls. Similar trends were observed for the regenerated bone and collagen areas. The blood vessel area was correlated with tissue regeneration in the first 3 months of evaluation. After 6 months of implantation, HA/DBM compounds showed less regenerated collagen than the DBM-only xenografts. In addition, all animal-derived xenografts improved tissue regeneration compared with the naturally healed defects. No clinical complications associated with any implanted compound were noted.

An Eco-Friendly Process to Extract Hydroxyapatite from Sheep Bones for Regenerative Medicine: Structural, Morphologic and Electrical Studies

Hydroxyapatite (HA) promotes excellent bone regeneration in bone-tissue engineering, due to its similarity to bone mineral and its ability to connect to living tissues. These factors promote the osteointegration process. This process can be enhanced by the presence of electrical charges, stored in the HA. Furthermore, several ions can be added to the HA structure to promote specific biological responses, such as magnesium ions. The main objective of this work was to extract hydroxyapatite from sheep femur bones and to study their structural and electrical properties by adding different amounts of magnesium oxide. The thermal and structural characterizations were performed using DTA, XRD, density, Raman spectroscopy and FTIR analysis. The morphology was studied using SEM, and the electrical measurements were registered as a function of frequency and temperature. Results show that: (i) an increase of MgO amount indicates that the solubility of MgO is below 5%wt for heat treatments at 600 °C; (ii) the rise of MgO content increases the capacity for electrical charge storage; (iii) sheep hydroxyapatite presents itself as a natural source of hydroxyapatite, environmentally sustainable and low cost, and promising for applications in regenerative medicine.

Biomineralization-inspired mineralized hydrogel promotes the repair and regeneration of dentin/bone hard tissue

Maxillofacial hard tissue defects caused by trauma or infection often affect craniofacial function. Taking the natural hard tissue structure as a template, constructing an engineered tissue repair module is an important scheme to realize the functional regeneration and repair of maxillofacial hard tissue. Here, inspired by the biomineralization process, we constructed a composite mineral matrix hydrogel PAA-CMC-TDM containing amorphous calcium phosphates (ACPs), polyacrylic acid (PAA), carboxymethyl chitosan (CMC) and dentin matrix (TDM). The dynamic network composed of Ca²⁺·COO^- coordination and ACPs made the hydrogel loaded with TDM, and exhibited self-repairing ability and injectability. The mechanical properties of PAA-CMC-TDM can be regulated, but the functional activity of TDM remains unaffected. Cytological studies and animal models of hard tissue defects show that the hydrogel can promote the odontogenesis or osteogenic differentiation of mesenchymal stem cells, adapt to irregular hard tissue defects, and promote in situ regeneration of defective tooth and bone tissues. In summary, this paper shows that the injectable TDM hydrogel based on biomimetic mineralization theory can induce hard tissue formation and promote dentin/bone regeneration.

Mesenchymal Stem Cells–Hydrogel Microspheres System for Bone Regeneration in Calvarial Defects

The repair of large bone defects in clinic is a challenge and urgently needs to be solved. Tissue engineering is a promising therapeutic strategy for bone defect repair. In this study, hydrogel microspheres (HMs) were fabricated to act as carriers for bone marrow mesenchymal stem cells (BMSCs) to adhere and proliferate. The HMs were produced by a microfluidic system based on light-induced gelatin of gelatin methacrylate (GelMA). The HMs were demonstrated to be biocompatible and non-cytotoxic to stem cells. More importantly, the HMs promoted the osteogenic differentiation of stem cells. In vivo, the ability of bone regeneration was studied by way of implanting a BMSC/HM system in the cranial defect of rats for 8 weeks. The results confirmed that the BMSC/HM system can induce superior bone regeneration compared with both the HMs alone group and the untreated control group. This study provides a simple and effective research idea for bone defect repair, and the subsequent optimization study of HMs will provide a carrier material with application prospects for tissue engineering in the future.