Synthesis, characterization and cytotoxicity of Chitosan/Polyvinyl Alcohol/Bioactive Glass hybrid scaffolds obtained by lyophilization

One of the important research topics in tissue engineering is the development of optimum three-dimensional scaffolds for regeneration and growth of bone tissue. The scaffold developed should promote an initial bio-mechanical support, provide the formation, deposition and organization of the new organic matrix generated, and degrade proportionally to the growth of the new tissue. In this study hybrid scaffolds based on the blend Chitosan (CHI)/Poly (vinyl alcohol) (PVA), with two different CHI:PVA molar ratios (1:1, and 3:1), and Bioactive Glass as the inorganic phase, were developed by a sol-gel route, followed by lyophilization. The materials were cross-linked with Glutaraldehyde. The obtained porous scaffolds were characterized by SEM, FTIR, porosity measurements by Archimedes method, and compression test. The in vitro degradation was studied by immersion in simulated body fluid for several time periods and evaluation of mass loss. Citotoxi-city analysis was carried out on samples as prepared and after immersion in PBS solution for 24hrs, using human fibroblast cells and MTT method to evaluate cell viability. The matrices obtained showed promising results, presenting about 96% porosity, pore size varying in the range 20-300 μm, and interconnected pores. The mass loss presented by the matrices with CHI/PVA ratios 3:1 and 1:1 during the degradation test in vitro, was around 10% after a week of testing, with macroscopic preservation of their physical structure. Cytotoxi-city tests showed that the samples were toxic as produced and not toxic after treatment with PBS, showing this approach was suitable as a final preparation step of these samples.Fil: Da Silva, Alexandra Rodrigues Pereira. Universidade Federal de Minas Gerais; BrasilFil: Macedo, Tais Lício. Universidade Federal de Minas Gerais; BrasilFil: Coletta, Dante Jesus. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Osteoarticular, Ingeniería Tisular y Terapias Emergentes; ArgentinaFil: Feldman, Sara. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Osteoarticular, Ingeniería Tisular y Terapias Emergentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Pereira, Marivalda de Magalhães. Universidade Federal de Minas Gerais; Brasi

Synthesis, characterization and cytotoxicity of Chitosan/Polyvinyl Alcohol/Bioactive Glass hybrid scaffolds obtained by lyophilization

One of the important research topics in tissue engineering is the development of optimum three-dimensional scaffolds for regeneration and growth of bone tissue. The scaffold developed should promote an initial biomechanical support, provide the formation, deposition and organization of the new organic matrix generated, and degrade proportionally to the growth of the new tissue. In this study hybrid scaffolds based on the blend Chitosan (CHI)/Poly (vinyl alcohol) (PVA), with two different CHI:PVA molar ratios (1:1, and 3:1), and Bioactive Glass as the inorganic phase, were developed by a sol-gel route, followed by lyophilization. The materials were cross-linked with Glutaraldehyde. The obtained porous scaffolds were characterized by SEM, FTIR, porosity measurements by Archimedes method, and compression test.  The in vitro degradation was studied by immersion in simulated body fluid for several time periods and evaluation of mass loss. Citotoxicity analysis was carried out on samples as prepared and after immersion in PBS solution for 24hrs, using human fibroblast cells and MTT method to evaluate cell viability. The matrices obtained showed promising results, presenting about 96% porosity, pore size varying in the range 20-300 µm, and interconnected pores. The mass loss presented by the matrices with CHI/PVA ratios 3:1 and 1:1 during the degradation test in vitro, was around 10% after a week of testing, with macroscopic preservation of their physical structure. Cytotoxicity tests showed that the samples were toxic as produced and not toxic after treatment with PBS, showing this approach was suitable as a final preparation step of these samples. Keywords: Chitosan, PVA, bioactive glass, lyophilization, porosity, scaffold

Calcium phosphate formation on alkali-treated titanium alloy and stainless steel

Alternatives to the plasma spraying method have been developed to obtain calcium phosphate coatings, like the biomimetic method. This process is a physicochemical method in which a substrate is soaked in a solution that simulates the physiological conditions, for a period of time enough to form a desirable layer of the calcium phosphate on the substrate. The titanium substrate usually investigated in the literature is subjected to an alkali treatment to induce the calcium phosphate formation and improve adhesion of the coating. The goals of this work are to compare the effect of alkaline treatments on two substrates titanium alloy and stainless steel, usually used for implants and orthopedic prostheses. The metallic substrates were treated with NaOH 5N at 60 °C for 24 h and NaOH 20N at 90 °C for 30 min. The samples were immersed in simulated body fluid for 3 days and in a solution with a higher calcium concentration for another three days. The modified substrates and coatings were characterized using profilometry, scanning electron microscopy and X-ray diffraction analysis. The alkaline treatment modified the characteristics of both substrates and allowed the nucleation a calcium phosphate film

Analysis of bioactive glasses obtained by sol-gel processing for radioactive implants

This paper presents the chemical and physical characterizations of SiO2 and SiO2-CaO bioactive glasses incorporated with samarium atoms, produced by sol-gel synthesis. The objective is to provide biocompatible and biodegradable radioactive seeds as an alternative to be used in Brachytherapy for the treatment of prostate cancer. The glasses were produced and analyzed by X-ray fluorescence spectroscopy (XRF), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), He picnometry and nitrogen adsorption analysis. A theoretical evaluation of the specific activity of the samples upon neutron activation is proposed. The XRF and EDS results demonstrate the incorporation of samarium atoms in the glass matrix. The experimental data coupled with the theoretical studies in neutron activation suggest that it is possible to obtain radioactive seeds with activities equivalent to 125I seeds used in brachytherapy prostatic

Characterization of calcium phosphate coating and zinc incorporation on the porous alumina scaffolds

Bone ingrowth requires materials with the existence of open and interconnected pores with diameters larger than 150 µm for proper circulation of nutrients. Such materials must possess enough mechanical strength to avoid failure whilst offering a bioactive surface for bone regeneration. We have developed porous ceramic alumina scaffold with compressive strength that achieves 3.3 MPa by replication method by using the network structure of cellular polymer foam. However, the biocompatibility of ceramics based on Al2O3 requires further improvement so that it could have strong bonding to natural bone tissue. To address this problem of the interface between alumina and bone, we have developed a novel calcium phosphate with Zn2+ (CaP-Zn) coating onto porous alumina ceramic scaffold by impregnating with calcium phosphate/poly(vinyl alcohol) slurry. The tri-dimensional alumina scaffold coated with CaP-Zn was extensively characterized by SEM, EDS and FTIR

Effect of polyvinyl alcohol content and after synthesis neutralization on structure, mechanical properties and cytotoxicity of sol-gel derived hybrid foams

Bioactive glass/polymer hybrids are promising materials for biomedical applications because they combine the bioactivity of these glasses with the flexibility of polymers. In this work it was evaluated the effect of increasing the PVA content of the on structural characteristics and mechanical properties of hybrid. The hybrids were prepared with 70 wt. (%) SiO2-30 wt. (%) CaO and PVA fractions of 20 to 60 wt. (%) by the sol-gel method. The structural and mechanical characterization was done by FTIR, SEM and compression tests. To reduce the acidic character of the hybrids due to the catalysts added, different neutralization solutions were tested. The calcium acetate alcoholic solution was the best neutralizing method, resulting in foams with final pH of about 7.0 and small sample contraction. The foams presented porosity of 60-85 wt. (%) and pore diameters of 100-500 μm with interconnected structure. An increase of PVA fraction in the hybrids improved their mechanical properties. The scaffolds produced provided a good environment for the adhesion and proliferation of osteoblasts

Preparation and biocompatibility of poly (methyl methacrylate) reinforced with bioactive particles

Calcium phosphates and bioactive glasses have been used in many biomedical applications for more than 30 years due basically to their bioactive behavior. However, ceramics are too brittle for applications that require high levels of toughness and easy processability. In this work, a biphasic calcium phosphate (BCP) and a bioactive glass composition (BG) were combined with polymers to produce composites with tailorable properties and processability. The BCP particles were synthesized by a precipitation technique. The BG particles were produced by sol-gel processing. The BCP particles were treated with a silane agent to improve the compatibility between particles and the polymer matrix. Dense samples were produced by hot pressing (200 °C) a mixture of 30 wt.% of particles in poly (methyl methacrylate). The samples produced were characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Mechanical properties were evaluated by a three point bending test. Samples were also submitted to in vitro bioactivity test and in vivo toxicity test. Results showed that the production of the composites was successfully achieved, yielding materials with particles well dispersed within the matrices. Evaluation of the in vivo inflammatory response showed low activity levels for all composites although composites with silane treated BCP particles led to milder inflammatory responses than composites with non-treated particles