The aim of our study was to prepare and characterize chitosan-based nanoparticles encapsulating propolis extract by ionotropic gelation and glutaraldehyde cross-linking technique. Both spectroscopic (UV-Vis, FTIR) and microscopic techniques (AFM) were applied for structural characterization of nanoparticles, along with entrapment and release study of propolis extract. The physico-chemical properties and morphological features of the obtained nanoparticles demonstrated a good correlation between all the investigated methods. Moreover, the bioactive compounds were stable upon the encapsulation procedure. Propolis release from the polymeric matrix was monitored in both simulated gastric acid and simulated intestinal fluids, concluding that our proposed formulation is suitable for controlled release. These results may provide a novel design, with improved bioavailability, stability and nutritional value of propolis bioactive compounds during processing and storage, with possible applications in food and nutraceutical industries.

A novel strategy to improve the success of soft and hard tissue integration of titanium implants is the use of nanoparticles coatings made from basically any type of biocompatible substance, which can advantageously enhance the properties of the material, as compared to its similar bulk material. So, most of the physical methods approaches involve the compaction of nanoparticles versus micron-level particles to yield surfaces with nanoscale grain boundaries, simultaneously preserving the chemistry of the surface among different topographies. At the same time, nanoparticles have been known as one of the most effective antibacterial agents and can be used as effective growth inhibitors of various microorganisms as an alternative to antibiotics. In this paper, based on literature research, we present a comprehensive review of the mechanical, physical, and chemical methods for creating nano-structured titanium surfaces along with the main nanoparticles used for the surface modification of titanium implants, the fabrication methods, their main features, and the purpose of use. We also present two patented solutions which involve nanoparticles to be used in cranioplasty, i.e., a cranial endoprosthesis with a sliding system to repair the traumatic defects of the skull, and a cranial implant based on titanium mesh with osteointegrating structures and functional nanoparticles. The main outcomes of the patented solutions are: (a) a novel geometry of the implant that allow both flexible adaptation of the implant to the specific anatomy of the patient and the promotion of regeneration of the bone tissue; (b) porous structure and favorable geometry for the absorption of impregnated active substances and cells proliferation; (c) the new implant model fit 100% on the structure of the cranial defect without inducing mechanical stress; (d) allows all kinds of radiological examinations and rapid osteointegration, along with the patient recover in a shorter time.

No abstract

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.

Open wounds treatment is very often a challenge for both the physician and patient. They require long term complex treatment with surgical debridement, dressing changing, additional therapies including expensive medication, with a high risk of failure. The most difficult to treat are the diabetic wounds and those that are associated with advanced arterial disease. In these special cases, the peripheral vascularization is severely impaired and the complications are imminent. Sixteen patients were selected from those appearing to our hospital departments of orthopedic and plastic surgery. Inclusion criteria included patients with a recurrent mixed fibrotic and granular wound base following trauma or diabetes, in which NPWT was indicated, without exclusion criteria. Patients enrolled were treated with regularly scheduled NPWT dressing change and using of a collagen scaffold. Patients were followed until healing, with visual representations of wound progression and time to full healing recorded. Both applications of these therapies appeared to accelerate the wound healing by clearing degenerative fibrous tissue and expediting wound granulation without additional complication. Some of the patients were healed partially and plastic surgery techniques were applied. Use of collagen scaffolds in conjunction with negative pressure wound therapy in the care of complex wounds is a reliable and effective method combining both the new granular tissue formation capacity of the scaffold to hold osteoblasts. In our experience, we have noticed that the patients benefit greatly when collagen scaffolds is combined with NPWT. It is our belief that this combination therapy combines the molecular clearing of non-viable collagen with the wound granulation necessary to advance complex wounds in healing.

The paper describes how to determine the noise in a production hall where there are production machines and equipment. The chosen plant is a production unit where filling of the polyurethane foam tubes is performed. The main activity is the production of professional insulators and wholesale of other products from the same range enumerating the following: wholesale chemical products; production of professional insulators; trade in chemicals and chemical industry. The recommended maximum admissible value for a normal 8h work program is 85 dB (A). The objective is to determine the level of noise in the factory and how it acts as a physical professional risk factor and its effects on the human body. The way in which the proposed objective was achieved was to determine the value of the noise level with the specialized equipment. Following the determinations that will be presented in the following chapters, appropriate protective measures have been taken.

This work investigates the alloying degree of HfNbTaTiZr high entropy alloy in equimolar percentages from raw, high purity powder, using solid state processing, for further uses in coating work components in harsh environments like marine, geothermal or oil and gas industry. The combination of elements was chosen according their properties, tailoring the composition for the final purpose. The alloying has been performed in a planetary ball mill with stainless steel vial and balls in a protective argon atmosphere to prevent oxidation, contamination or ignition and N-heptane as a process control agent to improve the material’s behavior during welding and re-welding in mechanical alloying process. Samples were taken at regular periods of time and analyzed to check the alloying degree evolution and to establish the optimum parameters for milling, best results being obtained at a speed of 300 rpm for 180 min (effective time) providing an alloying degree over 50% was achieved.

The antioxidant and disinfectant properties of silver have been known for a long time, but explaining its antibacterial mechanism was only possible through the modern methods of investigation and analysis, such as radioactive isotopes and the electron microscopy. The effective forms of silver that determine the microbial inhibition are the silver salts, and the optimal antimicrobial effect is obtained by releasing continuously a moderate amount of silver ions. On the other hand, many studies show that the size and shape of the silver nanoparticles play a key role in their antibacterial activity. The paper presents some results of the research regarding the chemical deposition of the metallic silver with antibacterial role on the oral implant of the Ti10Zr bio-alloy. The research was conducted in the Chemistry Laboratory of the Sciences and Environment Faculty from the Lower Danube University of Galati. To establish the optimum chemical deposition conditions of the metallic silver we used several experimental regimes in different conditions of experimentation. The paper presents the experimental results obtained when introducing the implants to be covered in the Tollens�s reagent following the influence of the hold time in the solution on the character of the deposition, on the dispersion, on the deposition uniformity and on particle size deposited. To cover chemically with metallic Ag we used solutions prepared with chemically pure reagents and bidistilled water under experimental regimes of chemical deposition. Electron microscopy analyses with electron scanning (SEM) and the EDX elemental analysis revealed the presence of the silver on the surface of implants, the degree of dispersion and the morphology of silver particles deposited according to the experimental regimes.