silicon and octacalcium-phosphate

The biomaterials that can control the active ions delivery to enhance cell activity are regarded as promising bone regenerative materials. In this study, a new approach aiming to layer-by-layer (LbL) assemble the bioavailable zinc ions in the core-shell-like silica@octacalcium phosphate (OCP) nanosphere and to analyze its efficacy on improving controlled-release was reported. Firstly, a pH-responsive electrostatic interaction was used to adsorb zinc ions on silica nanospheres with different zinc concentration, which was followed by coating silica gel layer. Then the nanospheres were LbL assembled with zinc ions and silica gel alternately until the desired multilayered nanospheres were achieved. Finally, the porous OCP shells were capped onto the outside surface of the nanospheres tailored by poly(aspartic acid) sodium molecules. The ion release tests in Tris buffers in vitro indicated that zinc release was controlled by pH and storage capacity, and silicon release was regulated by the OCP shell barrier. A temporal gradient within short times and sustained-dosage for a prolonged time toward the zinc and silicon ions could be obtained in this multilayer system. The results of this organized active ion assembly might open a promising future direction for effective delivery of trace elements in bone defect therapy.

Topics: Adsorption; Buffers; Calcium; Calcium Phosphates; Delayed-Action Preparations; Hydrogen-Ion Concentration; Microscopy, Electron, Transmission; Nanostructures; Phosphorus; Silicon; Silicon Dioxide; Solutions; Spectroscopy, Fourier Transform Infrared; X-Ray Diffraction; Zinc

Recently, calcification was observed on implanted intraocular lens (IOL) surfaces when viscoelastic substances were applied during surgery. To elucidate the mechanisms of mineral formation, the crystallization of calcium phosphates on IOL surfaces was studied in vitro with nanomolar sensitivity using a constant composition method. Three different commercial viscoelastic materials (Viscoat, OcuCoat, and Amvisc Plus) were investigated and it was found that some IOLs treated with Viscoat or Amvisc Plus induced the nucleation and growth of octacalcium phosphate crystallites under biological conditions. After treatments, the IOL surfaces became more hydrophilic probably because of the high viscoelastic phosphate and carboxylate contents. In contrast to Viscoat, the use of OcuCoat during surgery resulted in virtually no octacalcium phosphate nucleations. Calcification studies of IOL surfaces treated with fatty acids, which are present in human aqueous humor, suggest that hydrophobic cyclic silicones adsorbed on the IOL surfaces interact strongly with hydrophobic hydrocarbon chains of the fatty acids, creating a layer of amphiphiles oriented with functional carboxylate groups exposed to the aqueous solution and serving as active calcification sites.

Topics: Calcinosis; Calcium Phosphates; Crystallization; Cyclization; Fatty Acids; Lenses, Intraocular; Microscopy, Electron, Scanning; Molecular Structure; Silicon