Mario Díaz-Dosque

Designing antimicrobial bioactive glass materials with embedded metal ions synthesized by the sol-gel method.

Bioactive glasses (SiO2-P2O5-CaO) having tailored concentrations of different biocide metal ions (copper or silver) were produced by the sol-gel method. All the particles release phosphorous ions when immersed in water and simulated body fluid (SBF). Moreover, a surface layer of polycrystalline hydroxy-carbonate apatite was formed on the particle surfaces after 10 day immersion in SBF as confirmed by X-ray diffraction and scanning electron microscopy (SEM) showing the bioactive materials. Samples with embedded either copper or silver ions were able to further release the biocide ions with a release rate that depends on the metal embedded and the dissolution medium: water or SBF. This biocide ion release from the samples explains the antimicrobial effect of our active particles against Escherichia coli DH5α ampicillin-resistant (Gram-negative) and Streptococcus mutans (Gram-positive) as determined by the Minimum Bactericidal Concentration (MBC) method. The antimicrobial behavior of the particles depends on the bacteria and the biocide ion used. Noteworthy, although samples with copper are able to release more metal ion than samples with silver, they present higher MBC showing the high effect of silver against these bacteria.

Synthesis of nanostructured porous silica coatings on titanium and their cell adhesive and osteogenic differentiation properties

Nanostructured porous silica coatings were synthesized on titanium by the combined sol-gel and evaporation-induced self-assembly process. The silica-coating structures were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and nitrogen sorptometry. The effect of the nanoporous surface on apatite formation in simulated body fluid, protein adsorption, osteoblast cell adhesion behavior, and osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) is reported. Silica coatings with highly ordered sub-10 nm porosity accelerate early osteoblast adhesive response, a favorable cell response that is attributed to an indirect effect due to the high protein adsorption observed on the large-specific surface area of the nanoporous coating but is also probably due to direct mechanical stimulus from the nanostructured topography. The nanoporous silica coatings, particularly those doped with calcium and phosphate, also promote the osteogenic differentiation of hBMSCs with spontaneous mineral nodule formation in basal conditions. The bioactive surface properties exhibited by the nanostructured porous silica coatings make these materials a promising alternative to improve the osseointegration properties of titanium dental implants and could have future impact on the nanoscale design of implant surfaces.

Preparation and bioactive properties of novel bone-repair bionanocomposites based on hydroxyapatite and bioactive glass nanoparticles †

Bionanocomposites based on ceramic nanoparticles and a biodegradable porous matrix represent a promising strategy for bone repair applications. The preparation and bioactive properties of bionanocomposites based on hydroxyapatite (nHA) and bioactive glass (nBG) nanoparticles were presented. nHA and nBG were synthesized with nanometric particle size using sol-gel/precipitation methods. Composite scaffolds were prepared by incorporating nHA and nBG into a porous alginate (ALG) matrix at different particle loads. The ability of the bionanocomposites to induce the crystallization of the apatite phase from simulated body fluid (SBF) was systematically evaluated using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. Both nHA/ALG and nBG/ALG composites were shown to notably accelerate the process of crystallization and growth of the apatite phase on the scaffold surfaces. For short immersion times in SBF, nBG (25%)-based nanocomposites induced a higher degree of apatite crystallization than nHA (25%)-based nanocomposites, probably due to the more reactive nature of the BG particles. Through a reinforcement effect, the nanoparticles also improve the mechanical properties and stability in SBF of the polymer scaffold matrix. In addition, in vitro biocompatibility tests demonstrated that osteoblast cells are viable and adhere well on the surface of the bionanocomposites. These results indicate that nHA- and nBG-based bionanocomposites present potential properties for bone repair applications, particularly oriented to accelerate the bone mineralization process.

Influence of chitosan grafted poly(vinyl sulfonic acid) as template on the calcium carbonate crystallization

Chitosan was grafted with polyvinylsulfonic acid (CHI-graft-PVS) through either chemical activation (CA) or ultrasound radiation (US) methods and the percentages of grafting (%G), grafting efficiency (%E) and the average degree of polymerization (R) were determined. The effect of CHI-graft-PVS as templates for in vitro crystallization of CaCO3 was evaluated by using gas diffusion method at different pH. It was found that CHI-graft-PVS act as an efficient modifier of crystal morphology or inhibit the crystallization depending on the experimental media and the method of grafting used. SEM analysis revealed that CHI-graft-PVS obtained through US method act as an inhibitor for CaCO3 crystallization. When CHI-graft-PVS from CA method was used, SEM analysis showed different CaCO3 morphologies such as spherical, prismatic, biconcave and needle-like crystals. Additionally, EDS confirmed the presence of S atoms from CHI-graft-PVS adsorbed on the surface of CaCO3 crystals. Results indicated that CHI-graft-PVS controls the nucleation, polymorphs and morphology of CaCO3 crystals. The composition of this new template and the control of pH of the mineralization solution seem to be crucial during CaCO3 crystallization. CHI-graft-PVS template represents an alternative approach for understanding the biomineralization process and offers a wide range of possibility for polymer controlled crystallization.