The study presents the preparation and characterization of new scaffolds based on bacterial cellulose and keratin hydrogel which were seeded with adipose stem cells. The bacterial cellulose was obtained by developing an Acetobacter xylinum culture and was visualized using SEM (scanning electron microscopy) and elementally determined through EDAX (dispersive X-ray analysis) tests. Keratin species (β–keratose and γ-keratose) was extracted by hydrolytic degradation from non-dyed human hair. SEM, EDAX and conductometric titration tests were performed for physical–chemical and morphological evaluation. Cytocompatibility tests performed in vitro confirmed the material non-toxic effect on cells. The scaffolds, with and without stem cells, were grafted on the burned wounds on the rabbit’s dorsal region and the grafts were monitored for 21 days after the application on the wounds. The clinical monitoring of the grafts and the histopathological examination demonstrated the regenerative potential of the bacterial cellulose–keratin scaffolds, under the test conditions.

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Biodegradable alloys and especially magnesium-based alloys are considered by many researchers as materials to be used in medicine due to their biocompatibility and excellent mechanical properties. Biodegradable magnesium-based materials have applications in the medical field and in particular in obtaining implants for small bones of the feet and hands, ankles, or small joints. Studies have shown that Mg, Zn, and Ca are found in significant amounts in the human body and contribute effectively and efficiently to the healing process of bone tissue. Due to its biodegradability, magnesium alloys, including Mg–Ca–Zn alloys used in the manufacture of implants, do not require a second surgery, thus minimizing the trauma caused to the patient. Other studies have performed Mg–Ca–Zn system alloys with zinc variation between 0 and 8 wt.% and calcium variation up to 5 wt.%, showing high biocompatibility, adequate mechanical properties, and Mg2Ca and Mg6Ca2Zn compounds in microstructure. Biocompatibility is an essential factor in the use of these materials, so that some investigations have shown a cell viability with values between 95% and 99% compared with the control in the case of Mg–0.2Ca–3Zn alloy. In vivo analyses also showed no adverse reactions, with minimal H2 release. The aim of this review includes aspects regarding microstructure analysis and the degradation mechanisms in a specific environment and highlights the biocompatibility between the rate of bone healing and alloy degradation due to rapid corrosion of the alloys.

The AlCrFeCoNi high entropy alloy exhibits unexpected properties that can be obtained after mixing five different elements, which could not be obtained from any one independent element. The difference to conventional alloys is that these alloys may have, at the same time, both hardness and plasticity, can be used in severe impact applications. In order to study the influence of aluminum content on the microhardness and microstructure of the high entropy alloys AlxCrFeCoNi (x: atomic ratio, x= 0.2 to 2.0) nine types of samples were obtained as mini-sized ingots (50x15x9.5 mm and 40 g weight). The mini-ingots were obtained using arc melt casting process in a vacuum arc remelting device (VAR MRF ABJ 900). The influence of the chemical elements on the microstructure, phases morphology and microhardness of AlxCrFeCoNi system was studied. The results have confirmed that mechanical properties could be greatly adjusted by the chemical composition change. The main element that influences the microhardness of the analyzed system is aluminum, due to the formation of Al-Fe compounds with high hardness. Increasing the aluminum content in the alloy to values greater than 1.8 ... 2 at.% contribute to the increase of hardness and also to the embrittlement thereof. Other elements like Cr, Fe, Co and Ni can contribute to mitigate increasing the hardness of the alloy. The type of phases formed in high entropy alloy are dependent to the aluminum concentration. So, depending on of aluminium content, different phases are obtained, like FCC for low Al content, mixture of FCC and BCC for about 2.5 %Al and BCC for high Al content. The crystallite size depends on the chemical composition and increase with the aluminium content.

Many high entropy alloy systems have been exploited in the past decade and among them AlCrFeCoNi alloy is widely studied. The structural and mechanical properties of AlCrxFeCoNi alloy was studied in this paper for different content of chromium (atomic ratio, x= 0.2 to 2.0 at. %). In this study, ten samples having different chemical composition were prepared from raw materials using RAV equipment, type MRF ABJ 900. The microstructure features, crystallite sizes and microhardness depends on chemical composition of the alloy. The microhardness values for AlCrxFeCoNi (x = 0.2 to 2 at. %) increases from 389.6 to 562.6 HV0.1. The maximum value of microhardness for the high entropy alloy AlCrxFeCoNi (x = 1), has been obtained for 20.55 wt% Cr and has the value 562.6 HV0.1.