Papers by Keyword: Silicon-Substituted Hydroxyapatite

Abstract: Series of silicon-substituted hydroxyapatite were prepared and characterized, and their ability to degrade methyl orange and Congo red in aqueous solutions were studied. The effect of substituted silicon amount on the photocatalytic degradation efficiency of the dyes was investigated. The substitution of SiO₄⁴⁻ groups for PO₄³⁻ groups caused OH⁻ loss and difference in the microstructure of hydroxyapatite, and the elimination rates of silicon-substituted hydroxyapatite decreased with the increasing of substituted silicon amount compared to that of pure hydroxyapatite.

Abstract: Studies about silicon-substituted hydroxyapatites exhibit several shortcomings that leave unanswered questions regarding the properties and subsequent biological outcomes generated by this biomaterial. Firstly, samples characterization is often incomplete, meaning that phase purity on the pellet surface is not assured. In fact, ceramic materials used in literature that are claimed to be pure are actually polluted through second phase as superficial polymerized silicate. In this study, we have successfully synthesized a phase pure silicon hydroxyapatite powder Ca₁₀(PO₄)_5.5(SiO₄)_0.5(OH)_1.5 (Si_0.5HA) compressed this powder into pellets, sintered them, and evaluated the biological response of osteoblast cells (C3H10 line) seeded on the pellet surface. Besides, the solubility in aqueous media of HA and Si_0.5HA pellets were determined through static experiments. These tests attempt to provide a comprehensive picture of the cellular response to the SiHA material, in order to determine the mechanism by which Si evokes the improved in vitro biological outcomes described in the literature. Results revealed first an equivalent solubility of Si_0.5HA and HA pellets, and second that cells do not react favourably to the pure SiHA surface.

Abstract: The addition of silicon ions to hydroxyapatite (HA) provides a more inorganic bone-like chemical composition compared to stoichiometric HA. It is known to aid the bioactivity of the material and to improve the rates of osseointegration, osteoconduction and bone mineralisation. The literature, however, lacks detailed information regarding each step of the aqueous precipitation procedure to produce silicon-substituted HA (Si-HA). The current work utilised Raman spectroscopy at each stage of the aqueous precipitation method to determine how the silicate is incorporated into the HA structure when producing Si-HA. Raman spectra indicated that at the initial stages of the reaction the disilicate ion (Si₂O₇^6-) formed with the orthosilicate (SiO₄^4-) ion becoming more dominant after sintering. The results demonstrated that the form of silicate in the Si-HA aqueous precipitation method can be tracked using Raman spectroscopy.

Abstract: Two inorganic compounds containing CO32- and SiO44- groups were introduced and ultrasound-aided coprecipitation method was applied to fabricate carbonated silicon-substituted hydroxyapatite (CSi-HA) nanopowder. The synthetic process was optimized and the crystalline phase, grain dimension and morphology of the CSi-HA nanopowder were characterized. The obtained results demonstrate that H3PO4 addition into alkaline Ca(OH)2 ammonia liquid with ultrasonic application can obviously prevent secondary phase formation and make the nascent HA product pure, highly dispersed and gel-like. The introduction of Na2SiO3 and Na2CO3 mixed solution as doping source into the nascent HA product with also continuous ultrasound utilization can effectively realize the ionic group substitution of HA by CO32- and SiO44- and make the final CSi-HA nanopowder fine and uniform. It was also found that the CSi-HA grain size shows a decrease trend with the increase of CO32- and SiO44- substitution in the experimental range.

Abstract: We have developed novel hydroxyapatite (HAp) cement, “chelate-setting HAp cement” on the basis of chelate bonding of inositol hexaphosphate (IP6). In order to create the cement with enhanced bioactivity, we used a silicon-substituted hydroxyapatite (Si-HAp) as a starting material instead of pure HAp powder. The Si-HAp powders were prepared via an aqueous precipitation reaction and surface-modified with IP6 (IP6-Si-HAp). The Si-HAp were synthesized with desired Si contents (0, 0.4, 0.8, 1.6, and 2.4 mass%). Regardless of the amount of Si, the XRD patterns and FT-IR spectra of the powders were similar to each other. Additionally, chemical composition of Si-HAp powders were the almost same as the nominal one. The substitution of Si resulted in a decrease in the a-axis and increase in the c-axis of unit cell of HAp. While, the compressive strength of IP6-Si-HAp cements was higher than that of Si-HAp cements. These results suggest that surface-modification of any powders with IP6 is effective for enhancement of mechanical property. Comparison of mechanical property between HAp and Si-HAp cement specimens revealed that the substitution of lower levels of Si into0 HAp lattice did not greatly influence compressive strength. However, the substitution of high dose of Si (over 2.4 mass%) reduced the compressive strength. Therefore, to fabricate the chelate-setting cements with enhanced bioactivity, it is necessary to control the amount of Si.

Abstract: The adhesion of bovine collagen type I, bovine serum albumin, bovine IgG, 1 % and 10 % (v/v) human serum to hydroxyapatite (HA), silicon-substituted hydroxyapatite (Si-HA) and tissue culture plastic were studied. The materials were incubated at 37 °C for 30 minutes, after which the protein solution was removed and analyzed. The adsorbed protein was evaluated by electrophoresis and immunoassay after extraction from the materials. The degree of adhesion was higher for collagen, followed by IgG and albumin on all materials. However there was no difference in the amount of collagen adsorbed onto the surface of each material and this was also the finding with albumin and IgG. These results suggest that the increased bioactivity seen with Si-HA is not due to the degree of protein adhesion, but may possibly be due to changes in the conformation of the bound proteins.