Abstract Kefir is a natural probiotic produced by kefir grains fermentation. Biofilms produced from fresh kefir grains in natura were studied for presenting structural characteristics that will be of great interest in the area of regenerative medicine. This work presents a study on the surface of kefir biofilms, obtained by the cultivation of kefir grains in commercial white sugar. Four different films were produced, varying the concentration of sugar. The crystallinity of the biofilms was analyzed and revealed that sugar concentration influences biofilm amorphousness. Morphology showed that the biofilms presented excellent superficial adhesiveness. Fractal parameters were studied and revealed that there was homogeneity in the biofilm microtexture. Both fractal succolarity and surface entropy showed that the degree of water penetration and topographic homogeneity of the biofilms was not influenced by sugar concentration. These results show that kefir biofilms have excellent structural and morphological properties to be used in the biomedical field.

In this work, chitosan and collagen-chitosan porous scaffolds were produced by the freeze drying method and characterized as potential skin substitutes. Their beneficial effects on soft tissues justify the choice of both collagen and chitosan. Samples were characterized using scanning electron microscope, Fourier Transform InfraRed Spectroscopy (FTIR) and thermogravimetry (TG). The in vitro cytocompatibility of chitosan and collagen-chitosan scaffolds was evaluated with three different assays. Phenol and titanium powder were used as positive and negative controls, respectively. Scanning electron microscopy revealed the highly interconnected porous structure of the scaffolds. The addition of collagen to chitosan increased both pore diameter and porosity of the scaffolds. Results of FTIR and TG analysis indicate that the two polymers interact yielding a miscible blend with intermediate thermal degradation properties. The reduction of XTT ((2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) and the uptake of Neutral Red (NR) were not affected by the blend or by the chitosan scaffold extracts, but the blend and the titanium powder presented greater incorporation of Crystal Violet (CV) than phenol and chitosan alone. In conclusion, collagen-chitosan scaffolds produced by freeze-drying methods were cytocompatible and presented mixed properties of each component with intermediate thermal degradation properties.

Titanium (Ti) is a biocompatible material, and calcium phosphate coating on titanium is commonly applied in order to obtain faster osseointegration around metallic implant. Osteoblast adhesion on three different Ti surfaces was evaluated. The investigated surfaces were commercially pure Ti (cp Ti), Ti coated with sodium titanate (Na-Ti), and Na-Ti followed by octacalcium phosphate coating (Ti-OCP) done by immersion in a calcium and phosphate-rich solution. The studied materials exhibited different morphology and composition. However, all the surfaces promoted cellular adhesion and showed cytocompatibility. No statistically significant difference was observed among the evaluated samples in relation to the number of cells.

O contato de metais, usados como biomateriais, em soluções que simulam a parte inorgânica e acelular do plasma sanguíneo (SBF) permite avaliar sua capacidade de precipitar fosfatos de cálcio. Estes fosfatos podem se formar na interface material-tecido, sendo importantes quando o material é implantado in vivo. Para tanto, várias soluções que possibilitam a deposição biomimética, como as de Kokubo, Neuman e Ringer são usadas na promoção da precipitação de fosfatos. Estas soluções utilizam diversos reagentes, sendo que muitos deles não são necessários na estequiometria dos principais fosfatos de cálcio. A partir de um estudo teórico que prevê a estabilidade termodinâmica de soluções, houve a motivação para projetar e experimentar in vitro uma solução simplificada. Desta forma, amostras de Ti foram lixadas, tratadas com NaOH 1M e posteriormente submetidas à exposição na solução simplificada. Após esta exposição por vários dias as superfícies foram analisadas por MEV/EDS e DRX para avaliar a ocorrência e as características do depósito. Pelos resultados experimentais é possível afirmar que a fase precipitada é o fosfato octacálcico, o que está de acordo com os resultados teóricos.

The contact of materials such as metals used as biomaterials in simulated body solutions (SBF) that mimetize the inorganic and acellular part of blood plasma allows the evaluation of its capacity of calcium phosphate precipitation. These phosphates can precipitate by biomimetic route in the interface material-tissue, being important when the material is in vivo implanted. In addition, there are several solutions that favor this biomimetic deposition such as named as Kokubo, Neuman and Ringer, and they are used in the promotion of precipitation. These solutions employed several reagents; some of them are not necessary in the stoichiometry of the main calcium phosphates. From a theoretical study that showed the possibility of using a simplified solution, we decide to investigate this solution in vitro precipitation conditions. In this way, samples of Ti were grinding, treated with 1M NaOH and subsequently exposed to simplified SBF. After the exposure of surfaces, they were analyzed by SEM/EDS and XRD to characterize the deposits. The experimental results show that the precipitated phase is octacalcium phosphate, which corroborate theoretical findings.