Detailed Consideration of Physicochemical Properties of CO3 apatites as Biomaterials in Relation to Carbonate Content Using ICP, X-ray Diffraction, FT-IR, SEM, and HR-TEM

Phosphorus removal from wastewater by waste concrete: influence of P concentration and temperature on the product

This study investigated the feature of phosphorus uptake by low-cost waste concrete. Adsorption isotherms, metal dissolution, influence of P concentration and temperature, as well as adsorbent regeneration were investigated. Chemical extraction, SEM, XRD, FTIR, and XPS were employed to determine the products of P sequestration. Results demonstrated that phosphate adsorption fitted the Langmuir isotherm model well, with estimated maximum phosphate adsorption capacity of 80.5 mg/g (10 °C). Of adsorbed phosphate, 72.1% could be desorbed when 0.1 M citrate buffer was used as eluant, and waste concrete could be recovered and reused for 4 times by the combination of eluting and roasting. Mechanisms including Ca/alkali dissolution, surface adsorption, and chemical precipitation are involved in the sequestration of phosphorus from wastewater by waste concrete. Weakly adsorptive phosphorus and Ca-P precipitate were the main products. P concentration was the major factor that affected P removal capacity and the product types, while temperature had certain effect at low P concentration. The dominant product was weakly adsorptive phosphorus for low P concentration at low temperature, which was substituted by Ca-P precipitate as temperature or P concentration increased. The increase of P concentration assisted both the increase of P removal potential and the formation of Ca-P precipitate to crystal DCPD.

Comparative study on the resorbability and dissolution behavior of octacalcium phosphate, β-tricalcium phosphate, and hydroxyapatite under physiological conditions

The dissolution behaviors of octacalcium phosphate (OCP), β-tricalcium phosphate (β-TCP), and hydroxyapatite (HA) were compared by implanting the materials in rat subcutaneous pouches for 8 weeks using a filter chamber or immersing them in simulated body fluid (SBF) or Tris-HCl buffer for 2 weeks at pH 7.4 and 37(o)C. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and chemical analysis were conducted on these materials. Degree of supersaturation (DS) in the two solutions immersed with each calcium phosphate material was calculated from their chemical compositions. The results showed that OCP partially converted to apatitic crystals, while β-TCP and HA remained unchanged after the implantation. The DS of the SBF solution remained slightly supersaturated with respect to OCP and β-TCP, but slightly undersaturated in the Tris-HCl buffer. These findings suggest that previously reported OCP and β-TCP biodegradation could be induced through cell-mediated osteoclastic resorption rather than a simple dissolution process.

A novel glass ionomer cement containing MgCO(3 )apatite induced the increased proliferation and differentiation of human pulp cells in vitro

This study aimed to investigate the in vitro biological response of human dental pulp cells to glass ionomer cement (GIC, Fuji IX GP(®)) containing 2.5% magnesium carbonate apatite (MgCO(3)Ap). MgCO(3)Ap was synthesized by wet method and characterized using FT-IR, XPS, and SEM. Fuji IX GP(®) served as a control. Test and control cements were prepared by encapsulated mixing the powder with Fuji IX-liquid (P/L=3.6:1). Eluates from cements extracted by 1 mL culture medium were collected at day 1, 7 and 14, and used for WST-1 proliferation assay. For ALPase activity, cells were maintained with cements in transwells, harvested and enzyme activity was measured at day 1, 4, 7, 14, and 21. We found a higher cell proliferation and increased ALPase activity by pulp cells in the test group compared to the control. This suggests the potential of GIC containing this novel biological apatite as a restorative material for pulp-dentin regeneration.