Abstract Boron phosphate glasses are known for their unique properties and have been investigated as biodegradable materials for biomedical applications. In this context, the present research studied the characterization of physical, mechanical, and bioactive properties of new boron-phosphate glass in the CaO-P2O5-K2O-B2O3 system produced by the melt-quenching method. The structure and morphology of the material were investigated by FTIR, XRD, DSC, SEM-EDS, laser diffraction, and BET-BJH methods. Additionally, density and Vickers hardness were determined, and its bioactive potential was evaluated by immersion in simulated body fluid (SBF). The results demonstrated higher values of Vickers hardness (7.45 GPa) for the new glass when compared to other glasses. Furthermore, the material exhibited apatite-forming ability after immersion in SBF, which was confirmed by the information obtained through surface analysis. The newly created glass presented a promising potential for applications in tissue engineering.

Resumo A casca de arroz é um resíduo abundante no Rio Grande do Sul, Brasil, e pode ser utilizada para produção de sílica pura. As biovitrocerâmicas têm a sílica como principal componente. A biocompatibilidade desses materiais pode ser incrementada adicionando componentes, como SrO. Este trabalho objetivou o uso da sílica proveniente da casca de arroz como um precursor de baixo custo para se obter biovitrocerâmica do sistema 50%SiO2-25%Na2O-(25-x)%CaO-x%SrO (% em mol) via sol-gel e investigar seu potencial como biomaterial. Duas amostras (BGC branco e BGC-5%Sr) foram obtidas e caracterizadas por difração de raios X (DRX), espectroscopia no infravermelho por transformada de Fourier (FTIR) e determinação de carbono elementar por método da combustão. A microscopia eletrônica de varredura (MEV) foi usada para investigar a morfologia das biovitrocerâmicas, enquanto o teste MTT de viabilidade celular foi usado para caracterização in vitro. A sílica obtida apresentou estrutura amorfa e pequena quantidade de carbono. As biovitrocerânicas apresentaram principalmente fases com Si, Ca, Na e Sr na sua estrutura. Ambas as amostras não apresentaram citotoxicidade frente às células mononucleares do sangue periférico (PBMC) e a incorporação de 5% de SrO aumentou a biocompatibilidade.

Abstract Rice husk is an abundant waste at the Rio Grande do Sul, Brazil, and it can be used to produce pure silicon dioxide, which is the main component of bioglass-ceramics. The addition of compounds, such as SrO, can improve the biocompatibility of these biomaterials. Therefore, the goal of this paper was to use rice husk silicon dioxide as a cheap precursor to obtaining bioglass-ceramics of the system 50%SiO2-25%Na2O-(25-x)%CaO-x%SrO (mol%) by sol-gel and investigate its potential use as a biomaterial. Two samples (BGC blank and BGC-5%Sr) were synthesized and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and elemental carbon analysis by the combustion method. Scanning electron microscopy (SEM) was used to investigate the morphology of the bioglass-ceramics, while MTT assay of cell viability was used for in vitro characterization. The obtained silicon dioxide was amorphous and presented a small carbon content. Also, the bioglass-ceramics showed main phases with Si, Ca, Na, and Sr on their structure. Both samples were not cytotoxic against peripheral blood mononuclear cells (PBMC), and the incorporation of 5% SrO improved biocompatibility.

Rice husk ashes are a potential source of pollution, thus there is continued interest in its recycling. An environmentally friendly solution is its conversion into products such as aluminosilicates that are designed for use as fertilizer. Aluminosilicates that present a high cationic exchange capacity becomes an excellent material to be used in soil for accumulating and liberating nutrients slowly to the plants. The aim of this study is to investigate the effects of the alkali concentration in the cationic exchange capacity of an aluminosilicate obtained from rice husk ashes. The obtained products were characterized by X-ray diffraction, scanning electron microscopy, atomic absorption spectroscopy, and cationic exchange capacity. The particles that were produced are composed of crystals smaller than 5 μm. The experimental conditions employed in this work produced a semi-crystalline aluminosilicate with a high cationic exchange capacity. The alkali concentration used had an influence on this property.