Modulation of zinc release from bioactive sol-gel derived SiO \u3c inf\u3e 2 -CaO-ZnO glasses and ceramics

Zinc is an essential trace element which may be effective in promoting hard tissue healing. Glasses in the SiO2-CaO-ZnO system were synthesized via sol-gel methods. Using a constant silica content (70 mol %), the ratio of Ca to Zn was varied (1.5, 3.5, or 6.5), as was the stabilization temperature (650, 750, or 850°C), to examine such effects on the bioactive response and zinc release in simulated body fluid (SBF). XRD revealed the development of CaSiO3 and Ca2ZnSi2O7 crystalline phases during stabilization at 850°C only. N2 adsorption analysis determined that the specific surface area (BET) varied between 14 and 179 m2/g and was dependent on composition and stabilization temperature, as was the average initial pore size (51-125 Å). The formation of hydroxycarbonate (HCA) and amorphous calcium phosphate (ACP) was observed at 14 days for samples stabilized at 650 or 750°C. Only ACP layers were observed on such samples prior to 14 day. Relative to the Ca levels at 14 day (60-485 μg/ml), Zn levels in solution were relatively low (0.06-1.18 μg/ml). EDX and ICP data suggested that released Zn was incorporated into the forming calcium phosphate reaction layer, thereby preventing concentrations of the essential trace element from reaching potentially toxic levels

Surface modified glasses and composites thereof

An inorganic glass having an aliphatic polymer covalently bonded to the surface thereof is disclosed for providing improved adhesion to a matrix polymer when the glass is employed as a composite filler, as well as for the formation of a composite absent a separate matrix polymer. The polymer is grafted onto the glass by a method which includes the steps of pretreating the surface of the glass with an activator which an activating moiety to the surface, functionalizing the pretreated surface by bonding functional moieties thereto, and polymerizing a cycloaliphatic monomer onto the functionalized surface in the presence of a ring opening polymerization catalyst. Also disclosed are novel inorganic glasses which contain both silicate and phosphate linkages

A Rapid, Quantitative Method for Assessing Axonal Extension on Biomaterial Platforms

Measuring outgrowth of neuronal explants is critical in evaluating the ability of a biomaterial to act as a permissive substrate for neuronal adhesion and growth. Previous methods lack the ability to quantify robust outgrowth, or lack the capacity to quantify growth on opaque substrates because they exploit the transparent nature of culture dishes to segregate neuronal processes from an image background based on color intensity. In this study, we sought to investigate the ability of opaque silica sol-gel materials to facilitate axonal outgrowth; therefore, a method was developed for quantifying outgrowth of neurites from dorsal root ganglion explants on these unique surfaces. Dorsal root ganglia were isolated from stage-nine chick embryos and cultured for 48 h on sol-gel materials presenting agarose and chitosan polysaccharides individually or in combination. Explants were then imaged, and basic image analysis software was used by three independent observers to obtain axonal length and axonal area measurements. Robust axon length and axonal spread measurements for ganglia cultured on agarose-chitosan sol-gel matrices yield an estimate of strong neural compatibility for these substrates over silica matrices presenting no polysaccharides, or silica matrices presenting chitosan or agarose individually. We suggest that this simple protocol for quantifying material biocompatibility offers an analysis strategy that can be used universally to the same end

Sintering of alumina ceramics reinforced with a bioactive glass of 3CaO.P₂O₅-SiO₂-MgO system

Alumina-based ceramics, Al2O3, exhibit a combination of properties which favor its use as biomaterial, specifically as structural dental prosthesis. Its most important properties as biomaterial are its elevated hardness, chemical stability and biocompatibility. Usually, Al2O3 is processed by solid-state sintering at a temperature of about 1600 oC, but it is very difficult to eliminate the porosity due to its diffusional characteristics. The objective of this work was the development and characterization of sintered Al2O3 ceramics, densified with a transient liquid phase formed by a bioactive 3CaO.P2O5-SiO2-MgO glass. Powder mixtures of 90 wt.% Al2O3 and 10 wt.% bioglass were milled, compacted and sintered at 1200 oC to 1450 oC. Comparatively, monolithic Al2O3 samples were sintered at 1600 oC/120 min. The sintered specimens were characterized by relative density, crystalline phases, microstructure and mechanical properties. The results indicate that the specimen sintered at 1450 oC/120 min present the best properties. Under this sintering condition, a relative density of 95% was reached, besides hardness higher than 9 GPa and fracture toughness of 6.2 MPa.m1/2. XRD analysis indicate alumina (\αAl2O3), whitlockite (3CaO.P2O5) and diopsite [3(Ca,Mg)O.P2O5], as crystalline phases. Comparatively, monolithic sintered Al2O3 samples presented 92% of relative density with 17.4 GPa and 3.8 MPa.m1/2 of hardness and fracture toughness respectively

Sol-gel derived 45S5 bioglass: synthesis, microstructural evolution and thermal behaviour

In this work, the 45S5 bioactive glass was synthesized through an aqueous sol–gel method. Characteristic functional groups were evidenced by Fourier transform infrared spectroscopy, the thermal behaviour was investigated by thermogravimetric and differential thermal analysis, crystallization kinetics and phase evolution were followed by X-ray diffraction measurements. The sintering behaviour of the sol–gel derived 45S5 was then studied by dilatometry and the microstructural evolution was followed step-by-step, interrupting the thermal cycle at different temperatures. In vitro dissolution tests were performed in order to assess the degradation behaviour of sol–gel derived 45S5 samples thermally treated at different temperatures. A relevant influence of the calcination conditions (namely, dwelling time and temperature) of the as-prepared powder on the phase appearance and its sintering behaviour as well as on the porosity features, in terms of pore dimension and interconnectivity, of the fired materials was stated