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Bone and tooth enamel surface are made up of different crystallographically hydroxyapatite (HA), whereby bone comprises a(b)-planes of HA whilst tooth enamel comprises c-planes of HA. The reason behind the difference between HA orientations in both tissues are still yet to be discovered. We report the fabrication of anisotropic coatings of a-plane oriented HA according to the following process: (i) synthesis of a-plane oriented HA powders via a hydrothermal reaction and (ii) fabrication of a-plane oriented HA coatings via a Drop-on-Demand (DoD) micro-dispensing technique. Two types of HAs with high a-plane orientation degree of 72.2 and 75.6% (HA10 and HA84, respectively) was synthesised for the DoD coatings. The HA84 coating demonstrated more uniform and flatter surface than HA10 coating. The heat treatment of HA10 and HA84 coatings prepared with mesh-sieved particles led to a low adhesion strength for the substrates. However, the orientation degrees of those coatings (96.0 and 94.6%, respectively) were higher than the coatings without mesh-sieving. [ABSTRACT FROM AUTHOR]

An injectable chelate-setting hydroxyapatite cement (IP6-HAp), formed by chelate-bonding capability of inositol phosphate (IP6), was developed. The effects of ball-milling duration of starting HAp powder and IP6 concentration on the material properties such as injectability and mechanical strength of the cement were examined. The cement powder was prepared by ball-milling the as-synthesized HAp powder for 5 min using ZrO2 beads with a diameter of 10 mm, followed by another 60 min with ZrO2 beads with a diameter of 2 mm, and thereafter surface-modified with 5000 ppm of IP6 solution. Injectable cement was then fabricated with this HAp powder and 2.5 mass% chitosan as a mixing solution, with a setting time of 36.3 ± 4.7 min and a compressive strength of 19.0 ± 2.1 MPa. The IP6-HAp cements prepared with chitosan showed favorable biocompatibility in vitro using an osteoblast cell model, and osteoconductivity in vivo using a pig tibia model. [ABSTRACT FROM AUTHOR]

Autograft has been carried out for anterior cruciate ligament (ACL) reconstruction surgery. However, it has negative aspect because patients lose their healthy ligaments from other part. We focus on a chitosan-hydroxyapatite (HAp) composite fiber as a scaffold of ligament regeneration. Chitosan- HAp composite fiber was made by using coagulation method. Chitosan-NaH 2 PO 4 solution was coagulated with coagulation bath including calcium ion to get the mono-fiber and then treated with sodium hydroxide solution to form HAp in fiber matrix. The mechanical property of the fiber was improved by the stretching of the wet one because of the orientation of chitosan molecule and the interaction between chitosan and HAp. Maximum stress was improved with increasing of sodium dihydrogen phosphate until 0.03 M. The swelling ratio of the fiber was inhibited by composited with HAp. Additionally, bone-bonding ability was confirmed by SBF soaking tests. [ABSTRACT FROM AUTHOR]

Current treatments for musculoskeletal disease and injury are restricted with the usage of autografts and allografts. Tissue engineering that applies the principles of biology and engineering to develop functional substitutes has potential promise of therapeutic regeneration for musculoskeletal tissues. However, engineering sizable tissues needs a vascular network to supply cells with nutrients, oxygen and signals after implantation. For this purpose, recent developments on therapeutic nanomaterials have been explored in delivering different vessel-inductive growth factors, small biomolecules and ions for scalable engineering into vascularizable scaffolds. Here, we provide an overview on the current efforts, and propose future perspectives for precise regulation on vascularization processes and musculoskeletal tissue functionality. [ABSTRACT FROM AUTHOR]

Abstract: Hydroxyapatite (HAp), with its high biocompatibility and osteoconductivity, readily absorbs proteins, amino acids and other substances, which in turn favor the adsorption and colonization of bacteria. To prevent bacterial growth and biofilm formation on HAp discs, silver-containing (1–20mol%) HAp (Ag-HAp) powders were synthesized using an ultrasonic spray pyrolysis (USSP) technique. The X-ray diffraction (XRD) peaks were very broad, indicating low crystallinity, and this induced the release of Ag+ ions from Ag-HAp powders. In addition, a gradual increase in Ca2+ ion release was observed. These results suggest that dissolution of Ca2+ ion in Ag-HAp triggered the release of Ag+ ions. The antimicrobial efficacy of Ag-HAp disc was tested against Staphylococcus aureus. Samples with Ag contents of more than 5mol% were found to be highly effective against bacterial colonization and biofilm formation in vitro. In vivo antibacterial tests using bioluminescent strains also showed reductions in the viability of bacteria with Ag-HAp (5mol%) discs. Biocompatibility tests using a modified Transwell® insert method showed that Ag-HAp (5mol%) discs have negative effects on osteoblast proliferation. These results indicate that Ag-HAp (5mol%) has effective antibacterial activity and good biocompatibility both in vitro and in vivo together with good biocompatibility, thus confirming its utility as a bactericidal material. [Copyright &y& Elsevier]