Importance Of Hydroxyapatite Research Articles

Synthesis of antibacterial silver and zinc doped nano-hydroxyapatite with potential in bone tissue engineering applications

Nano-hydroxyapatite doped with either Ag+ or Zn2+ has been synthesized using the sol-gel precipitation method at conditions of low dopant content (dopant/Ca2+ molar ratio of 0.006 and 0.012) and low temperature (around 200 °C). The synthesized materials show length dimensions of 10–40 nm, low crystallinity, and rod-shaped particles for the Zn2+ doped samples. Through the simulated body fluid assay, the ability of the materials to nucleate the formation of apatite on their surface was examined. The viability of human dental pulp stem cells cultured with the materials was evaluated after 3 and 7 days, and the osteogenic differentiation of cells cultured with the materials was assessed through the activity of the alkaline phosphatase. In addition, the antibacterial activity against Aggregatibacter actinomycetemcomitans, an important microorganism related to oral infections, was studied by counting bacterial colony-forming units cultured in the presence of the materials. All the materials showed biocompatibility with human dental pulp stem cells, osteoinductive potential, and antibacterial activity against Aggregatibacter actinomycetemcomitans, highlighting among them the Zn2+ doped nano-hydroxyapatite samples. Considering the importance of hydroxyapatite in the field of medical and dental applications of ceramic materials, and the pathologies induced by Aggregatibacter actinomycetemcomitans in oral tissues, the adequate balance between the biocidal activity and biocompatibility of these synthetic nano-hydroxyapatite materials highlights their potential for biomedical and dental applications.

APATITIC NANOPOWDERS AND COATINGS: A COMPREHENSIVE REVIEW

The use of artificial biomaterials has been acclaiming potential therapeutic scope in diverse clinical applications. This review started with the description of the basics of biomaterials, and desirable properties, which are the prerequisites to understand biomaterials. The orthopedic biomaterials, their classification and the importance of calcium phosphate (CaP) materials for hard-tissue applications were utterly discussed. Furthermore, among the various CaP biominerals, the importance of hydroxyapatite (HAP) and its synthesis techniques was comprehensively reviewed. The sol–gel route for the synthesis of HAP nanoparticles and deposition of coatings were systematically studied. Among the metallic substrates, Ti6Al4V alloy remained the focus of this study. Moreover, several film pre-preparation methods were also given due importance. The importance of other surface modification techniques, especially in the context of Ti6Al4V substrates, was also discussed. Among several coating techniques to deposit CaP coatings, special attention was paid to the spin and dip coating techniques. In addition to monolithic HAP coatings, reinforced and antimicrobial HAP coatings were also reviewed from broad perspectives. Therefore, this review provides an in-depth insight into the preparation and properties of apatitic nanoparticles and their coatings for orthopedic and dental applications.

Optoelectronics and defect levels in hydroxyapatite by first-principles.

Hydroxyapatite (HAp) is an important component of mammal bones and teeth, being widely used in prosthetic implants. Despite the importance of HAp in medicine, several promising applications involving this material (e.g., in photo-catalysis) depend on how well we understand its fundamental properties. Among the ones that are either unknown or not known accurately, we have the electronic band structure and all that relates to it, including the bandgap width. We employ state-of-the-art methodologies, including density hybrid-functional theory and many-body perturbation theory within the dynamically screened single-particle Green's function approximation, to look at the optoelectronic properties of HAp. These methods are also applied to the calculation of defect levels. We find that the use of a mix of (semi-)local and exact exchange in the exchange-correlation functional brings a drastic improvement to the band structure. Important side effects include improvements in the description of dielectric and optical properties not only involving conduction band (excited) states but also the valence. We find that the highly dispersive conduction band bottom of HAp originates from anti-bonding σ* states along the ⋯OH-OH-⋯ infinite chain, suggesting the formation of a conductive 1D-ice phase. The choice of the exchange-correlation treatment to the calculation of defect levels was also investigated by using the OH-vacancy as a testing model. We find that donor and acceptor transitions obtained within semi-local density functional theory (DFT) differ from those of hybrid-DFT by almost 2 eV. Such a large discrepancy emphasizes the importance of using a high-quality description of the electron-electron interactions in the calculation of electronic and optical transitions of defects in HAp.