Bioactive glasses (BG) are versatile materials for various biomedical applications due to their capacity to bond to hard and soft tissues. These materials can be produced with different nominal compositions, such that include fluoride ions. Fluorine-containing-BG (BGF) can be produced by the sol-gel method, and its properties can be changed by altering the synthesis parameters. Here, BGF particle size between 235 nm-390 nm were obtained through sol-gel method assisted by ultrasound energy (BGU) or through mechanical stirring (BGM). The BGM and BGU particles showed highly dispersed spherical shape, moreover BGM are mesoporous and BGU are dense structures, indicating mixing mode can alter mainly the material textural characteristics. All compositions have apatite forming ability, verified by DRX from 14 days in SBF. The results showed CaF2 on the surface of BGF particles, indicating that part of F ions was not incorporated in the material network. The samples did not show any cytotoxicity towards human cells in Cellular Metabolic Activity and Calcein assays. This study showed that mechanical agitation was more efficient to produce mesoporous particles to be applied as carrier of drugs and molecules to the biological environment, so BGM can be used as a more efficient biomaterial for such applications.

ABSTRACT 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.

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.

Tissue engineering has evolved from the use of biomaterials for bone substitution that fulfill the clinical demands of biocompatibility, biodegradability, non-immunogeneity, structural strength and porosity. Porous scaffolds have been developed in many forms and materials, but few reached the need of adequate physical, biological and mechanical properties. In the present paper we report the preparation of hybrid porous polyvinyl alcohol (PVA)/bioactive glass through the sol-gel route, using partially and fully hydrolyzed polyvinyl alcohol, and perform structural characterization. Hybrids containing PVA and bioactive glass with composition 58SiO2-33CaO-9P2O5 were synthesized by foaming a mixture of polymer solution and bioactive glass sol-gel precursor solution. Sol-gel solution was prepared from mixing tetraethoxysilane (TEOS), triethylphosphate (TEP), and calcium chloride as chemical precursors. The hybrid composites obtained after aging and drying at low temperature were chemically and morphologically characterized through infrared spectroscopy and scanning electron microscopy. The degree of hydrolysis of PVA, concentration of PVA solution and different PVA-bioglass composition ratios affect the synthesis procedure. Synthesis parameters must be very well combined in order to allow foaming and gelation. The hybrid scaffolds obtained exhibited macroporous structure with pore size varying from 50 to 600 µm.

Híbridos de vidro bioativo/polímero são materiais de grande interesse em aplicações biomédicas devido às suas propriedades, que combinam a bioatividade dos materiais cerâmicos, com a flexibilidade dos polímeros. Para regeneração do tecido ósseo, propriedades mecânicas da matriz são críticas e o módulo e a resistência mecânica do material devem ser similares aos do osso natural. Em trabalhos anteriores desenvolvidos no grupo obtiveram-se espumas híbridas 80% vidro bioativo/20% álcool polivinílico (PVA), para aplicação em engenharia de tecidos. Neste trabalho foi aumentado o teor de PVA dos híbridos para otimizar suas propriedades mecânicas. Os híbridos foram preparados com fase inorgânica 70%SiO2-30%CaO e teores de PVA de 20 a 60%, através da hidrólise ácida de tetraetil ortosilicato, adição de CaCl2, PVA, surfactante e HF. A secagem das espumas mostrou-se crítica, ocorrendo grande contração do gel As amostras foram secas por duas rotas: (1): pré-secagem a 40°C em estufa e secagem a vácuo; (2): pré-secagem a 40°C em estufa com circulação de ar e secagem a alto vácuo. A rota de secagem 2 apresentou maior perda de água e menor contração das amostras. Corpos de prova cúbicos, 10x10x10mm, foram submetidos a ensaios de compressão com velocidade de aplicação de carga de 0,5mm/min. Observou-se que o aumento do teor de polímero na composição das espumas melhorou suas propriedades mecânicas.

Bioactive glass/ polymer hybrids are materials of high interest for biomedicals applications because their assets, they combine the bioactivity of ceramics, with the flexibility of the polymers. In bone regenerations, mechanicals properties of the scaffold are criticisms and they must be similar to the bone properties. In previous works, hybrid foams with 80% bioactive glass and 20% polyvinyl alcohol (PVA) were prepared by sol-gel process to application as scaffold for bone tissue engineering. In this work, the PVA fraction of the hybrids was increase for to improve their mechanicals properties. The hybrids were prepared with composition inorganic of 70%SiO2-30%CaO and PVA fractions of 20 to 60% by sol-gel method. The drying of the foams was a criticism stage, occurring ample contraction from the gel. The samples were drying for two routes: (1) pre-drying at 40ºC for 7 days and drying at vacuum for 48 hours; (2) pre-drying with air circulation at 40ºC for 7 days and drying at high vacuum for 48 hours. The drying route 2 had the most lost of water and the least contraction of samples. Five specimens of hybrids samples with dimensions 10x10x10mm were compressed at 0,5mm/min-1. The increase of PVA fraction in the hybrids improves their mechanicals properties.

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.

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.