An experimental and theoretical approach on stability towards hydrolysis of triethyl phosphate and its effects on the microstructure of sol-gel-derived bioactive silicate glass

Synthesis and Characterization of Bioactive Glass via CTAB Modified Sol-Gel Method for In Vitro Biological Activities

Bone defect repair methods have significant drawbacks and limitations. The discovery and development of bioactive glasses (BGs) have greatly advanced the treatment of bone diseases. BGs can uniquely bond to living tissues, including bone, due to the formation of a hydroxyapatite (HAp) layer on their surface. These glasses synthesized using various catalysts and structure-directing agents to enhance their biological activities. However, most catalysts generate toxicity, alter pH levels, and work at high concentrations. Similarly, many surfactants have limited surface areas, poor capacity to create well-defined mesoporous structures, and potential toxicity, reducing the bioactivity, biocompatibility, and biodegradability of the BGs. To address these issues, this study evaluates a bioactive glass synthesized via the sol-gel process, using low concentration CTAB as a structure-directing agent and citric acid as a catalyst. The phase composition, surface morphology, specific surface area, inner structure, crystal structure, elemental composition, and functional groups of the samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive x-ray spectroscopy (EDS), and Fourier-transform infrared microscopy (FTIR) techniques, respectively. The in vitro bioactivity was tested by soaking samples in simulated body fluid and analyzing the HAp layer formation using XRD, SEM, and FTIR. In addition, the in vitro biocompatibility, and an in vitro biodegradability were measured. 0.3 M of CTAB (BG3) exhibited a larger specific surface area with spherical-shaped particles and pore volume with a mesoporous structure results better in bioactivity and biodegradability. Furthermore, all samples exhibited cell viability above 70%, indicating that the prepared materials are biocompatible. The findings highlight the potential of CTAB-modified BGs for biomedical applications, especially in bone repair and regeneration.

Spray-dried ternary bioactive glass microspheres: Direct and indirect structural effects of copper-doping on acellular degradation behavior

Silicate-based bioactive glass nano/microspheres hold significant promise for bone substitution by facilitating osteointegration through the release of biologically active ions and the formation of a biomimetic apatite layer. Cu-doping enhances properties such as pro-angiogenic and antibacterial behavior. While sol-gel methods usually yield homogeneous spherical particles for pure silica or binary glasses, synthesizing poorly aggregated Cu-doped ternary glass nano/microparticles without a secondary CuO crystalline phase remains challenging. This article introduces an alternative method for fabricating Cu-doped ternary microparticles using sol-gel chemistry combined with spray-drying. The resulting microspheres exhibit well-defined, poorly aggregated particles with spherical shapes and diameters of a few microns. Copper primarily integrates into the microspheres as Cu0 nanoparticles and as Cu2+ within the amorphous network. This doping affects silica network connectivity, as calcium and phosphorus are preferentially distributed in the glass network (respectively as network modifiers and formers) or involved in amorphous calcium phosphate nano-domains depending on the doping rate. These differences affect the interaction with simulated body fluid. Network depolymerization, ion release (SiO44-, Ca2+, PO43-, Cu2+), and apatite nanocrystal layer formation are impacted, as well as copper release. The latter is mainly provided by the copper involved in the silica network and not from metal nanoparticles, most of which remain in the microspheres after interaction. This understanding holds promising implications for potential therapeutic applications, offering possibilities for both short-term and long-term delivery of a tunable copper dose. STATEMENT OF SIGNIFICANCE: A novel methodology, scalable to industrial levels, enables the synthesis of copper-doped ternary bioactive glass microparticles by combining spray-drying and sol-gel chemistry. It provides precise control over the copper percentage in microspheres. This study explores the influence of synthesis conditions on the copper environment, notably Cu0 and Cu2+ ratios, characterized by EPR spectroscopy, an aspect poorly described for copper-doped bioactive glass. Additionally, copper indirectly affects silica network connectivity and calcium/phosphorus distribution, as revealed by SSNMR. Multiscale characterization illustrates how these features impact acellular degradation in simulated body fluid, highlighting the therapeutic potential for customizable copper dosing to address short- and long-term needs.

Calcium Phosphate-Based Nanomaterials: Preparation, Multifunction, and Application for Bone Tissue Engineering

Calcium phosphate is the main inorganic component of bone. Calcium phosphate-based biomaterials have demonstrated great potential in bone tissue engineering due to their superior biocompatibility, pH-responsive degradability, excellent osteoinductivity, and similar components to bone. Calcium phosphate nanomaterials have gained more and more attention for their enhanced bioactivity and better integration with host tissues. Additionally, they can also be easily functionalized with metal ions, bioactive molecules/proteins, as well as therapeutic drugs; thus, calcium phosphate-based biomaterials have been widely used in many other fields, such as drug delivery, cancer therapy, and as nanoprobes in bioimaging. Thus, the preparation methods of calcium phosphate nanomaterials were systematically reviewed, and the multifunction strategies of calcium phosphate-based biomaterials have also been comprehensively summarized. Finally, the applications and perspectives of functionalized calcium phosphate biomaterials in bone tissue engineering, including bone defect repair, bone regeneration, and drug delivery, were illustrated and discussed by presenting typical examples.