3D nanocomposite chitosan/bioactive glass scaffolds obtained using two different routes: an evaluation of the porous structure and mechanical properties

Porous synthetic substrates are developed through tissue engineering technologies to grow new tissue, restoring the function of tissue or an organ. For bone regeneration, these scaffolds must support the dynamic load exerted on this tissue, achieved primarily by increasing their compression strength, as established in the literature. The aim of this paper was to incorporate an inorganic composite bioactive glass (60%SiO2 - 36%CaO - 4%P2O5) as a reinforcing agent in mechanical 3D scaffolds that must remain porous. Two strategies were adopted: a co-precipitation method to obtain a nanoparticulate dispersion of bioactive glass (BGNP) and a sol-gel method to combine a bioactive glass solution (BG) with a previously prepared chitosan polymer solution. Moreover, a lyophilization process was also used, generating highly porous scaffolds. Various aspects of the scaffold were evaluated, including the morphology, orientation and size of the pores, and mechanical strength, as obtained using the two synthetic methods. The data for compressive strength revealed increased strength after the incorporation of bioactive glass, which was more pronounced when utilizing the nanoscale bioactive glass

Engineered Hybrid Scaffolds of Poly(vinyl alcohol)/Bioactive Glass for Potential Bone Engineering Applications: Synthesis, Characterization, Cytocompatibility, and Degradation

The synthesis, characterization, preliminary cytocompatibility, and degradation behavior of the hybrids based on 70% Poly(vinyl alcohol) and 30% bioactive glass (58SiO2–33CaO–9P2O5, BaG) with macroporous tridimensional structure is reported for the first time. The effect of glutaraldehyde covalent crosslinker in the organic-inorganic nanostructures produced and, as a consequence, tailoring the hybrids properties was investigated. The PVA/BaG hybrids scaffolds are characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray Microcomputed tomography analysis (μCT). Cytotoxicity assessment is performed by the MTT method with VERO cell culture. Additionally, the hybrid in vitro degradation assay is conducted by measuring the mass loss by soaking in deionized water at 37°C for up to 21 days. The results have clearly shown that it is possible to modify the PVA/BaG hybrids properties and degradation behavior by engineering the structure using different concentrations of the chemical crosslinker. Moreover, these hybrid crosslinked nanostructures have presented 3D hierarchical pore size architecture varying within 10–450 μm and a suitable cytocompatibility for potential use in bone tissue engineering applications

Comparison of the Effect of Sol-Gel and Coprecipitation Routes on the Properties and Behavior of Nanocomposite Chitosan-Bioactive Glass Membranes for Bone Tissue Engineering

Recent studies in tissue engineering have highlighted the importance of the development of composite materials based on biodegradable polymers containing bioactive glasses, in particular, composites for high load support and excellent cell viability for potential application in bone regeneration. In this work, hybrid composite films were obtained by combining chitosan with bioactive glass in solution form and in nanoparticle dispersion form obtained by the two different synthesis routes: the sol-gel method and coprecipitation. The bioactive glass served both as a mechanical reinforcing agent and as a triggering agent with high bioactivity. The results of in vitro assays with simulated body fluid demonstrated the formation of a significant layer of fibrils on the surface of the film, with a typical morphology of carbonated hydroxyapatite, reflecting induction of a favorable bioactivity. Maximum tensile stress increased from 42 to 80 MPa to the sample with 5% wt bioactive glass. In addition, samples containing 5% and 10% wt bioactive glass showed a significant increase in cell viability, 18 and 30% increase compared to the control group. The samples showed significant response, indicating that they could be a potential material for use in bone regeneration through tissue engineering

Effects of manganese incorporation on the morphology, structure and cytotoxicity of spherical bioactive glass nanoparticles

Bioactive glass nanoparticles (BGNPs) are of great interest in tissue engineering as they possess high dissolution rate and capability of being internalized by cells, releasing their dissolution products with therapeutic benefits intracellularly. A modified Stöber process can be applied to obtain different BGNPs compositions containing therapeutic ions while maintaining controllable particle morphology, monodispersity and reduce agglomeration. Here, BGNPs containing Mn, an ion that has been shown to influence the osteoblast proliferation and bone mineralization, were evaluated. Particles with up to 142.3 ± 10.8 nm and spherical morphology were obtained after MnO incorporation in the SiO2 – CaO system. X-ray photoelectron spectroscopy (XPS) indicated the presence of Mn2+ species and also a reduction in the number of bridging oxygen bonds due to the Ca and Mn. The Ca and Mn network modifier role on the silica network was also confirmed by magic-angle spinning 29Si solid-state nuclear magnetic resonance (MAS NMR). MTT evaluation showed no reduction in the mitochondrial metabolic activity of human mesenchymal stem cells exposed to the glass ionic products. Thus, evaluation showed that Mn could be incorporated into BGNPs by the modified Stöber method while maintaining their spherical morphology and features as a promising strategy for tissue regeneration

Effect of severe plastic deformation on the biocompatibility and corrosion rate of pure magnesium

It is well established that magnesium has a considerable potential for use as a biodegradable material. This report describes the effect of processing by severe plastic deformation (SPD) on the grain refinement, mechanical behavior, biocompatibility and corrosion behavior of commercial purity magnesium. The material was received as cast slabs and processed by rolling, equal-channel angular pressing and high-pressure torsion to produce samples with average grain sizes in the range of ~0.5–300 ?m. The results show that severe plastic deformation does not affect the biocompatibility. However, the corrosion behavior is affected by the processing route. Specifically, SPD processing leads to general corrosion as opposed to localized corrosion in the as-cast and hot-rolled condition

Antioxidant, photoprotective and inhibitory activity of tyrosinase in extracts of Dalbergia ecastaphyllum.

Dalbergia ecastaphyllum is a native Brazil plant with importance for beekeeping, and widely used in folk medicine. For the first time, the extracts of this plant were assessed for the presence of hydrophilic and lipophilic antioxidants, as well as inhibition of tyrosinase, free radicals scavenging and sunscreen protection. The antioxidant activity was evaluated by free radical scavenging (DPPH) and β-carotene bleaching assay. The tyrosinase inhibitory activity was evaluated and calculated the EC50. The photoprotective activity was measured using different concentrations of D. ecastaphyllum extracts. The Sun Protection Factor (SPF) of the samples was higher than 6, and the sample from Ilhéus showed the most pronounced photoprotective effect. Sample from Canavieiras presented the highest antioxidant activity by free radical scavenging DPPH and β-carotene bleaching method, with 92.41% and 48.34%, respectively. All samples inhibited the tyrosinase, especially the sample from Prado that was most effective (124.62 μg.mL-1). Significant negative correlation was found between flavonoid contents and inhibition of tyrosinase. The overall results provide relevant information about the Dalbergia ecastaphyllum species, indicating as potential material to cosmetic and pharmaceutical industry