4th Generation Biomaterials Based on PVDF-Hydroxyapatite Composites Produced by Electrospinning: Processing and Characterization.

Biomaterials that effectively act in biological systems, as in treatment and healing of damaged or lost tissues, must be able to mimic the properties of the body's natural tissues in its various aspects (chemical, physical, mechanical and surface). These characteristics influence cell adhesion and proliferation and are crucial for the success of the treatment for which a biomaterial will be required. In this context, the electrospinning process has gained prominence in obtaining fibers of micro- and nanometric sizes from polymeric solutions aiming to produce scaffolds for tissue engineering. In this manuscript, poly(vinylidene fluoride) (PVDF) was used as a polymeric matrix for the manufacture of piezoelectric scaffolds, exploring the formation of the ß-PVDF piezoelectric phase. Micro- and nanometric hydroxyapatite (HA) particles were incorporated as a dispersed phase in this matrix, aiming to produce multifunctional composite membranes also with bioactive properties. The results show that it is possible to produce membranes containing micro- and nanofibers of the composite by the electrospinning process. The HA particles show good dispersion in the polymer matrix and predominance of ß-PVDF phase. Also, the composite showed apatite growth on its surface after 21 days of immersion in simulated body fluid (SBF). Tests performed on human fibroblasts culture revealed that the electrospun membranes have low cytotoxicity attesting that the composite shows great potential to be used in biomedical applications as bone substitutions and wound healing.

Dynamics of the natural genesis of ß-TCP/HAp phases in postnatal fishbones towards gold standard biocomposites for bone regeneration.

The search for gold-standard materials for bone regeneration is still a challenge in reconstruction surgery. The ratio between hydroxyapatite (HAp) and ß-tricalcium phosphate (ß-TCP) in biphasic calcium phosphate ceramics (BCPs) is one of the most important factors in osteoinduction promotion and controlled biodegradability, configurating what is currently considered as a possible gold standard material for bone substitution in reconstructive surgery. Exploring the natural genesis of the HAp and ß-TCP phases in fishbones during their postnatal growth, this study developed a biphasic bioceramic obtained from the calcination of Nile tilapia (Oreochromis niloticus) bones as a function of their ages. The natural genesis dynamics of the structural evolution of the ß-TCP and HAp phases were characterized by physicochemical methods, taking into account of the age of the fish and the material processing conditions. Thermal analysis (TGA / DTA) showed complete removal of the organic matter and transitions associated with the transformation of carbonated hydroxyapatite (CDHA) to HAp and ß-TCP phases. After calcination at 900 °C, the material was characterized by: X-ray diffraction (XRD) and refinement by the Rietveld method; Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR); Raman spectroscopy; Scanning Electron Microscopy (SEM) and Flame Atomic Absorption Spectroscopy (FAAS). The analysis allowed identification and quantitative estimate of the variations of the HAp and ß-TCP phases in the formation of the BCPs. The results showed that the decrease in ß-TCP against the increase in the HAp phases is symmetrical to the dynamics of the natural genesis of these phases, surprisingly maintaining the balanced phase proportion even when bones of young fishes were used. The microstructure analysis confirms the observed transformation. In addition, in vivo tests demonstrated the osteoinductive potential of BCP scaffolds implanted in an ectopic site, and their remarkable regenerative functionality, as bone graft, was demonstrated in alveolar bone after tooth extraction. MTT cytotoxicity assay for BCP samples for MC3T3-E1 pre-osteoblasts and L929 fibroblasts cells showed viability equal or higher than 100%. A logistic empirical model is presented to explain the three stages of HAp natural formation with fish age and it is also compared to the fish size evolution.

In vivo evaluation of interactions between biphasic calcium phosphate (BCP)-niobium pentoxide (Nb2O5) nanocomposite and tissues using a rat critical-size calvarial defect model.

Natural or synthetic biomaterials are increasingly being used to support bone tissue repair or substitution. The combination of natural calcium phosphates with biocompatible alloys is an important route towards the development of new biomaterials with bioperformance and mechanical responses to mimic those of human bones. This article evaluated the structural, physical, mechanical and biological properties of a new mechanical improved nanocomposite elaborated by association of fish biphasic calcium phosphate (BCP) and niobium pentoxide (Nb2O5). The nanocomposite (Nb-BCP) and the pure BCP, used as a positive control, were obtained by powder metallurgy. The density, porosity and microhardness were measured. The structural analysis was determined by X-ray diffraction (XRD) and the biological properties were studied in histological sections of critical size calvaria defects in rats, 7, 15, 30, 45 and 60 days after implantation of disks of both materials. Morphological description was made after scanning electron microscopy (SEM) and optical microscopy analysis. After sintering, the Nb-BCP nanocomposite presented four crystalline phases: 34.36% calcium niobate (CaNb2O6), 21.68% phosphorus niobium oxide (PNb9O25), 42.55% ß-tricalcium phosphate (Ca3(PO4)2) and 1.31% of niobium pentoxide (Nb2O5) and exhibited increases of 17% in density, 66% in Vickers microhardness and 180% in compressive strength compared to pure BCP. In vivo study, showed biocompatibility, bioactivity and osteoconductivity similar to pure BCP. SEM showed the formation of globular accretions over the implanted nanocomposites, representing one of the stages of bone mineralization. In conclusion, the BCP and Nb2O5 formed a nanocomposite exhibiting characteristics that are desirable for a biomaterial, such as bioperformance, higher ß-TCP percentage and improved physical and mechanical properties compared to pure BCP. These characteristics demonstrate the promise of this material for supporting bone regeneration.

Estudo do comportamento do sulfatode cálcio: bioatividade e solubilidade em fluido corpóreo simulado / Studying the behavior of calcium sulfate: bioactivity and solubility in simulated body fluid

Com a finalidade de correção de defeitos ósseos, diversos materiais sintéticos têm sido utilizados, entre os quais está o sulfato de cálcio. Objetivo: o objetivo do presente estudo foi avaliar, in vitro, a bioatividade do sulfato de cálcio em fluido corpóreo simulado (SBF). Métodos: quatro corpos de prova foram preparados em matrizes de policloreto de vinila (PVC) circulares, misturando-se o sulfato de cálcio nas proporções de líquido/pó recomendadas pelo fabricante, com água destilada. As amostras ficaram imersas em 50ml de SBF, a 36,5ºC, por até 21 dias, sendo que a solução foi renovada a cada três dias. A bioatividade foi verificada por meio de Espectroscopia no Infravermelho por Transformada de Fourier (FTIR). Resultados: no teste de bioatividade in vitro, a análise por FTIR detectou a presença de apatita sobre o substrato de sulfato de cálcio, demonstrando tratar-se de um material bioativo. Além disso, foi observada uma redução expressiva do tamanho da amostra vinculada ao processo de reabsorção. Conclusão: dentro das limitações do estudo, pode-se concluir que o sulfato de cálcio é um material bioativo e rapidamente reabsorvido...

Several types of synthetic material have been used to correct bone defects, among which is calcium sulfate. Objective: the present in vitro study aimed at assessing the bioactivityof calcium sulfate in simulated body fluid (SBF). Methods: four specimens were prepared in polyvinyl chloride (PVC) circle matrices by mixing calcium sulfate with distilled water, as recommended by the manufacturer. Samples were immersed in 50 ml of SBF, at 36.5 ºC, for no longer than 21 days. The solutionwas renewed every three days. Bioactivity was assessed by means of Fourier transform infrared spectroscopy (FTIR). Results: The in vitro bioactivity test, carried out by means of FTIR analysis, revealed the presence of apatite formation over calcium sulfate substrate, thereby proving it to be a bioactive material. In addition, there was significant reduction in the size of the sample, which was associated with the process of resorption. Conclusion: within the limitations of the present study, it is reasonable to conclude that calcium sulfate is a bioactive material which is quickly absorbed...