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Protein adsorption plays a key role in determining the biological properties of calcium phosphate biomaterials. Calcium (Ca) and phosphate (P) ions are involved in the protein adsorption process and influence the protein adsorption behaviors. In this study, the proteins adsorption on hydroxyapatite (HA) (001), (100), (110), (010) surfaces with Ca, P ions in solution were investigated by Molecular Dynamics (MD) simulation. The results reveal that basic proteins were more favorable to adsorb on HA surface than acidic proteins. HA (110) surface absorbed more acidic proteins than HA (001) and (100). HA (010) surface adsorbed more basic protein. Basic residues play a more important role than acidic residues in the adsorption process, as the basic residues have shown higher absorption energy than acidic residues, and they were more likely to adsorb on HA surfaces than to bind P ions in solution. Most of the active sites of protein, especially for acidic residues, are prefer to interact with HA surface through water molecules. Basic residues are more likely to adsorb onto HA surfaces directly. The presence of Ca, P ions in solution can influence the adsorption behaviors of protein. The formation of Ca, P ion cluster may lead to desorption of proteins. And they can compete with water molecules to bond to HA surfaces, acting as a bridge of protein interacting with HA surfaces instead of water-bridge. This Ca, P ions bridge connection make the adsorption energy of protein weakened. The results of this study provided new information at atomic/molecular level to further interpret the mechanism of protein adsorption on calcium phosphate surfaces with Ca, P ions. It is also helpful for designing new calcium phosphate biomaterials with specific surface properties to adsorb target protein for biomedical applications. [ABSTRACT FROM AUTHOR]

Porous bioceramics have been widely studied for bone tissue engineering. A deep understanding on the mechanism of bone growth and biomineralization depends on the extracted interface information between the new precipitated calcium phosphates (CaPs) and the porous substrate at a nanometer scale. However, due to their intrinsic brittleness and the complexity of the sample shape, there is still lack of such information. Here, by a combination of focused ion beam ( FIB) and transmission electron microscopy ( TEM), in-situ cross-sectional electron transparent interface was prepared. The precipitated dense apatite layer is composed of individual microgranules which further consist of tiny flake-like crystals. The new crystallites grow along c-axis and are mostly oriented perpendicular to HA substrate. This preferred orientation is more pronounced in the presence of protein. This work offers a novel and feasible approach using FIB- TEM to in situ image porous bioceramic scaffold and precipitated apatite layer interface and can be extended to study many other biointerfaces. [ABSTRACT FROM AUTHOR]

Abstract: Proteins play an important role in the process of biomineralization, which is considered the critical process of new bone formation. The calcium phosphate (Ca-P) mineralization happened on hydroxyapatite (HA), β-tricalcium phosphate (β-TCP) and biphasic calcium phosphate (BCP) when proteins presented were investigated systematically. The results reveal that the presence of protein in the revised simulated body fluid (RSBF) did not alter the shape and crystal structure of the precipitated micro-crystals in the Ca-P layer formed on the three types of bioceramics. However, the morphology of the Ca-P precipitates was regulated but the structure of Ca-P crystal was unchanged in vivo. The presence of proteins always inhibits Ca-P mineralization in RSBF and the degree of inhibitory effect is concentration dependent. Furthermore, Protein presence can increase the possibility of HA precipitation in vitro and in vivo. The results obtained in this study can be helpful for better understanding the mechanism of biomineralization induced by the Ca-P bioceramics. [Copyright &y& Elsevier]

Fluoridated hydroxyapatite (FHA) [Ca 10 (PO 4) 6 F x (OH) 2−x , x = 0–2] is believed to be a promising calcium phosphate (CaP) to replace pure hydroxyapatite (HA) for next-generation implants, owing to its better biocompatibility, higher antibacterial activity, and lower solubility. Notably, the shape and size of the CaP crystals play key roles in their performance and can influence their applications. One-dimensional (1D) FHA nanorods are important CaP materials which have been widely used in regenerative medicine applications such as restorative dentistry. Unfortunately, the traditional synthesis methods for FHA nanorods either employ surfactants or take a relatively long time. In this study, we aimed to propose a facile synthesis route to fabricate FHA nanorods without any surfactants using an electrochemical deposition method for the first time. This study focused on preparing FHA nanorods without the assistance of any surfactant, unlike the traditional synthesis methods, to avoid chemical impurities. FHA nanorods with lengths of 124–2606 nm, diameters of 28–211 nm, and aspect ratios of 4.4–21.8 were synthesized using the electrochemical method, followed by a heat treatment. For the as-synthesized FHA nanorods, the Ca/P ratio was 1.60 and the atomic concentration of F was 2.06 at.%. An ultrastructure examination revealed that each FHA nanorod possessed long-range order, good crystallinity, and a defect-free lattice with a certain crystallographic plane orientation along the whole rod. In short, we propose a novel, surfactant-free, cost-saving, and more efficient route to synthesize FHA nanorods which can be widely applied in multiple biomedical applications, including drug delivery, bone repair, and restorative dentistry. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effects of osteogenic differentiated adipose-derived stem cell (ADSC) loaded beta-tricalcium phosphate (β-TCP) in the restoration of bone defects under intraperitoneal administration of 1α,25-dihydroxyvitamin D3(1α,25(OH) 2 D 3 ). ADSCs were isolated from the fat tissue of 8 week old Wister rats and co-cultured with β-TCP for 21 days under osteogenic induction. Then the ADSC-β-TCP complexes were implanted into bone defects in the femora of rats. 1α,25(OH) 2 D 3 (VD) or normal saline (NS) was administrated intraperitoneally every other day after the surgery. Femora were harvested at day 7, day 14 and day 28 post-surgery. There were 4 groups for all specimens: β-TCP-NS group; β-TCP-ADSC-NS group; β-TCP-VD group and β-TCP-ADSC-VD group. Alkaline phosphatase (ALP) was up-regulated obviously in ADSC groups compared with non-ADSC groups at day 7, day 14 and day 28, although high expression of runt-related transcription factor 2 (RUNX2) was only seen at day 7. Furthermore, the number of TRAP-positive osteoclasts and the expression of cathepsin K (CK) were significantly decreased in VD groups compared with non-VD groups at day 7 and day 14. As a most significant finding, the β-TCP-ADSC-VD group showed the highest BV/TV ratio compared with the other three groups at day 28. Taken together, ADSC-loaded β-TCP under the administration of 1α,25(OH) 2 D 3 made a promising therapy for bone defects restoration. [ABSTRACT FROM AUTHOR]

Titanium has been widely used in medical implants for hard tissue replacements. Nevertheless, the bioinert innate oxide layer on the titanium implant surface usually makes the implant fail to osseointegrate with the surrounding tissue after surgery. To improve the bioactivity of titanium implants, the deposition of calcium phosphate (CaP) coatings attracts much research interest owing to the excellent bioactivity and biocompatibility of CaP. This work successfully developed a promising synthetic method to prepare uniform fluoridated CaP coatings with ultrathin thicknesses (∼170 nm) and desired phases on acid etched pure titanium (AETi) substrates. A dense ultrathin coating with a dominant phase of fluoridated amorphous CaP (FACP) was obtained by an electrochemical deposition method in galvanostatic mode. After a heat treatment at 600 °C for 3 h in a humid atmosphere, the as-prepared coating was transformed to a coating with a dominant phase of fluoridated hydroxyapatite (FHA). Additionally, the dominant phase of the coating could be transformed from FACP to α-tricalcium phosphate (α-TCP) by a heat treatment at 800 °C for 3 h. Unlike previously reported fluoridated CaP coatings with thicknesses of around several micrometers, the ultrathin thickness could potentially enhance the adhesive strength and ductility of coating. Notably, the fluorine incorporation in the coating could bring in additional benefits such as lower solubility, higher antibacterial activity, and higher adhesive strength. Electrochemical deposition associated with post heat treatment could obtain fluoridated CaP coatings with different desired phases in a controllable manner, which is very important since CaPs with different phases possess different properties and may be suitable for different biomedical applications. This study proposed a promising, simple, and low-cost method which can endow complex-shaped titanium implants with better bioactivity for dental and orthopedic applications. • Unlike previously reported fluoridated CaP coatings with thicknesses of around several micrometers, the ultrathin thickness (∼170 nm) could potentially enhance the adhesive strength and ductility of coating. • The fluorine incorporation in the coating could bring additional benefits such as lower solubility, higher antibacterial activity, and higher adhesive strength. • Electrochemical deposition associated with post heat treatment could obtain fluoridated CaP coatings with different desired phases in a controllable manner, which is very important since CaPs with different phases possess different properties and may be suitable for different biomedical applications. • Proposed a promising, simple, and lower-cost route to endow complex-shaped titanium implants with better bioactivity, which could be widely applied in dental and orthopedic applications. [ABSTRACT FROM AUTHOR]