Corrosion protection of AZ31 alloy and constrained bacterial adhesion mediated by a polymeric coating obtained from a phytocompound.

The prevention of microbial biofilm formation on a biomaterial surface is crucial in avoiding implants failures and the development of antibiotic resistant bacteria. It was reported that biodegradable Mg alloys may show antimicrobial effects due to the alkalinization of the corroding area. However, this issue is controversial and deserves a detailed study, since the processes occurring at the [biodegradable metal/biological medium] interface are complex and varied. Results showed that bacterial adhesion on AZ31 was lower than that of the titanium control and revealed that was dependent on surface composition, depicting some preferential sites for bacterial attachment (C-, P-, O-containing corrosion products) and others that are particularly avoided (active corrosion sites). As a key challenge, a strategy able to improve the performance of Mg alloys by both, reducing the formation of corrosion products and inhibiting bacterial adhesion was subsequently developed. A polymeric layer (polyTOH) was obtained by electropolymerization of thymol (TOH), a phytophenolic compound. The polyTOH can operate as a multifunctional film that improves the surface characteristics of the AZ31 Mg alloy by enhancing corrosion resistance (ions release was reduced to almost the half during the first days) and create an anti-adherent surface (bacterial attachment was 30-fold lower on polyTOH-AZ31 than on non-coated Mg alloy and 200-fold lower than Ti control and was constrained to specific regions). This anti-adherent property implies an additional advantage: enhancement of the efficacy of antibiotic treatments.

Quality, storability, and essential oil content of Ligularia fischeri during modified atmosphere packaging storage.

Modified atmosphere packaging (MAP) enhanced the quality and storability of Ligularia fischeri. Oxygen transmission rate (OTR) films were used as a MAP. MAP storage displayed lower fresh weight loss than perforated film. The oxygen, carbon dioxide, and ethylene concentration were properly maintained by a 10,000 cc OTR packaging film at 8 °C and 30,000 cc OTR packaging film at 24 °C. On the last day of storage, the off-odor, such as the acetaldehyde and ethanol concentration, was the lowest in the 10,000 cc OTR film at 8 °C and 30,000 cc OTR film at 24 °C treatments. The 10,000 cc OTR film treatment at 8 °C and 30,000 cc OTR film treatments at 24 °C had the highest chlorophyll content, total phenolic content, leaf toughness, antioxidant activity, vitamin C, and less off-flavor. The shelf life of 10,000 cc OTR film was 13 days, at 8 °C storage temperature. At 24 °C storage temperature, the shelf life of 30,000 cc OTR film was 4 days. The MAP storage of the Ligularia treated with 10,000 cc OTR film at 8 °C and 30,000 cc OTR film at 24 °C had the highest essential oil content. These results suggest that the best MAP film for cold-chain distribution was the 10,000 cc OTR film, and the 30,000 cc OTR film was a more suitable MAP film for local distribution without the cold-chain system of L. fischeri.

Biological effects of magnesium particles degradation on UMR-106 cell line: influence of fluoride treatments.

Mg-based materials are promising for orthopedic, dental, and cardiovascular applications but their high degradation rate in vivo (release of Mg ions and debris particles) is cause of great concern. Protective treatments involving fluoride conversion coatings have been proposed in order to reduce corrosion rates. The aim of this study was to evaluate Mg debris biodegradation and its possible cytotoxic effects on osteoblastic cells in situ. Neutral Red dying and Acridine Orange staining techniques were used as endpoints to analyse the cytotoxic effects at 100-2000 µg/mL concentration range. Results showed a marked variation of Mg ion concentration in the culture medium after different exposure periods (1, 2, or 24h). Interestingly, the release rate of magnesium ions was dependent on the presence or absence fluoride treatment. Adverse effects induced by ≥1000 µg/mL MP doses and Mg ion concentrations higher than 480 µg/mL were observed on cells. Results showed significant differences between the concentration of Mg ions in the presence and absence of cells. This fact reveals a dynamic equilibrium mediated by Mg ion input and output in the cells that leads to the change in MP corrosion rates. Fluoride release from conversion coatings did not show cytotoxic effects.

Spontaneous adsorption of silver nanoparticles on Ti/TiO2 surfaces. Antibacterial effect on Pseudomonas aeruginosa.

Titanium is a corrosion-resistant and biocompatible material widely used in medical and dental implants. Titanium surfaces, however, are prone to bacterial colonization that could lead to infection, inflammation, and finally to implant failure. Silver nanoparticles (AgNPs) have demonstrated an excellent performance as biocides, and thus their integration to titanium surfaces is an attractive strategy to decrease the risk of implant failure. In this work a simple and efficient method is described to modify Ti/TiO(2) surfaces with citrate-capped AgNPs. These nanoparticles spontaneously adsorb on Ti/TiO(2), forming nanometer-sized aggregates consisting of individual AgNPs that homogeneously cover the surface. The modified AgNP-Ti/TiO(2) surface exhibits a good resistance to colonization by Pseudomonas aeruginosa, a model system for biofilm formation.

Corrosion inhibition of powder metallurgy Mg by fluoride treatments.

Pure Mg has been proposed as a potential degradable biomaterial to avoid both the disadvantages of non-degradable internal fixation implants and the use of alloying elements that may be toxic. However, it shows excessively high corrosion rate and insufficient yield strength. The effects of reinforcing Mg by a powder metallurgy (PM) route and the application of biocompatible corrosion inhibitors (immersion in 0.1 and 1M KF solution treatments, 0.1M FST and 1M FST, respectively) were analyzed in order to improve Mg mechanical and corrosion resistance, respectively. Open circuit potential measurements, polarization techniques (PT), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were performed to evaluate its corrosion behavior. SECM showed that the local current of attacked areas decreased during the F(-) treatments. The corrosion inhibitory action of 0.1M FST and 1M FST in phosphate buffered solution was assessed by PT and EIS. Under the experimental conditions assayed, 0.1M FST revealed better performance. X-ray photoelectron spectroscopy, energy dispersive X-ray and X-ray diffraction analyses of Mg(PM) with 0.1M FST showed the presence of KMgF(3) crystals on the surface while a MgF(2) film was detected for 1M FST. After fluoride inhibition treatments, promising results were observed for Mg(PM) as degradable metallic biomaterial due to its higher yield strength and lower initial corrosion rate than untreated Mg, as well as a progressive loss of the protective characteristics of the F(-)-containing film which ensures the gradual degradation process.

Filtrado del aire

El aire es el medio mas importante para la diseminación de microorganismos, por lo tanto su filtrado debe ser lo suficientemente efectivo como para retener la mayor cantidad. En hospitales e industria farmaceutica interesan los filtros cuya eficiencia se determina en función del número de particulas retenidas; son filtros de altisima eficiencia o absolutos. El segundo aspecto es la contaminación interior, que se soluciona con el flujo laminar