Ozone as an alternative decontamination process for N95 facemask and biosafety gowns.

COVID-19 pandemic created a global shortage of medical protective equipment. Here, we considered ozone (O3) a disinfectant alternative due to its potent oxidative activity against biological macromolecules. The O3 decontamination assays were done using SARS-CoV-2 obtained from patients to produce artificial contamination of N95 masks and biosecurity gowns. The quantification of SARS-CoV-2 was performed before and after exposing the samples to different ozone gas concentrations for times between 5 and 30 min. Viral loads as a function of the O3 exposure time were estimated from the data obtained by the RT-PCR technique. The genetic material of the virus was no longer detected for any tested concentrations after 15 min of O3 exposure, which means a disinfection Concentration-Time above 144 ppm min. Vibrational spectroscopies were used to follow the modifications of the polymeric fibers after the O3 treatment. The results indicate that the N95 masks could be safely reused after decontamination with treatments of 15 min at the established O3 doses for a maximum of 6 cycles.

Biocide effect against SARS-CoV-2 and ESKAPE pathogens of a noncytotoxic silver-copper nanofilm.

Nanometric materials with biocidal properties effective against severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) and pathogenic bacteria could be used to modify surfaces, reducing the risk of touching transmission. In this work, we showed that a nanometric layer of bimetallic AgCu can be effectively deposited on polypropylene (PP) fibers. The virucidal properties of the AgCu nanofilm were evaluated by comparing the viral loads remaining on uncoated and coated PP after contact times between 2 and 24 h. Quantification of virion numbers for different initial concentrations indicated a reduction of more than 95% after 2 h of contact. The bactericidal action of the AgCu nanofilm was also confirmed by inoculating uncoated and coated PP with a pool of pathogenic bacteria associated with pneumonia (ESKAPE). Meanwhile, no cytotoxicity was observed for human fibroblasts and keratinocyte cells, indicating that the nanofilm could be in contact with human skin without threat. The deposition of the AgCu nanofilm on the nonwoven component of reusable cloth masks might help to prevent virus and bacterial infection while reducing the pollution burden related to the disposable masks. The possible mechanism of biocide contact action was studied by quantum chemistry calculations that show that the addition of Ag and/or Cu makes the polymeric fiber a better electron acceptor. This can promote the oxidation of the phospholipids present at both the virus and bacterial membranes. The rupture at the membrane exposes and damages the genetic material of the virus. More studies are needed to determine the mechanism of action, but the results reported here indicate that Cu and Ag ions are good allies, which can help protect us from the virus that has caused this disturbing pandemic.

Comparison of the osteogenic, adipogenic, chondrogenic and cementogenic differentiation potential of periodontal ligament cells cultured on different biomaterials.

It has been shown that the cellular responses such as adhesion, proliferation and differentiation are influenced by the surface properties, such as the topography or the surface energy. However, less is known about the effect of the chemical composition and type of material on the differentiation potential. The objective of the present paper is to compare the differentiation potential of periodontal ligament cells (HPLC) into adipocytes, osteoblasts, chondroblasts and cementoblasts of three type of materials (metals, ceramics and polymers) without using any biological induction media, but keeping the average roughness values within a limited range of 2.0-3.0µm. The samples were produced as discs of 14×2mm; (n=30 for each type of material). Two samples of each type were chosen; stainless-steel 316L and commercially pure titanium for the metallic samples. The polymers were polymethyl methacrylate and high-density polyethylene, and finally for the ceramics; zirconia and dental porcelain were used. The surfaces properties of the samples (wettability, chemical composition and point of zero charge, PZC) were measured in order to correlate them with the biological response. To evaluate the potential of differentiation, human periodontal ligament cells obtained from extracted teeth were used since they are a promising source for periodontal tissue regeneration. Cell proliferation was initially tested to assure non-toxic effects using a viability colorimetric assay. Finally, the differentiation pattern was evaluated using real time reverse transcription quantitative polymerase chain reaction for 5, 10 and 15days without adding any induction medium. The results indicated that the relative expression of genes related to a particular phenotype were different for each surface. However, not clear correlation between the type of material or their surface properties (morphology, chemical composition, wettability or point of zero charge) and the expression pattern could be identified. For example, bone markers were mainly expressed on cpTi and PMMA; one metallic hydrophobic and one polymeric hydrophilic sample which have similar Ra values but presented different topographical features, although both samples have in common a PZC below 7.

Oral bacterial adhesion on amorphous carbon and titanium films: effect of surface roughness and culture media.

Implant infections can cause severe problems from malfunctioning to dangerous sepsis affecting the health of the patient. For many years, titanium has been the most common material used on dental implants due to their mechanical and biocompatibility properties. Recent studies suggest that amorphous carbon (a-C) films can be possible candidates for coating dental implants, improving some important features like biocompatibility and bone formation. In the oral cavity, the risk of an implant infection is high due to multiple species are capable to colonize this site and these biofilm infections can limit the use of these medical devices. The purpose of this study was to evaluate the influence of the surface chemistry, roughness, and culture media in the bacterial colonization process. To achieve this, a-C and Ti films were deposited on rough and smooth surfaces and cultured with different microorganisms belonging to the oral microbiota with mycoplasma medium (MM) or human saliva (HS). Samples were incubated for 24 h, after this, samples were sonicated and the number of attached bacteria was determined by counting the colony-forming units (CFU's) from each sample. The proportion of the species in the biofilms was determined using checkerboard DNA-DNA hybridization. Data were analyzed by Student's t test using Bonferroni's modification of Student's t test and differences on the proportion of the bacterial species attached to each surface were determined using the Mann-Whitney test. Results show an increased number of CFU's on rough surfaces, especially on the a-C surfaces. The incubation media were an important factor on the adhesion of certain taxa, whereas other species were more sensitive to surface chemistry and others to surface roughness.

Unbalanced magnetic field configuration: plasma and film properties.

Coatings of CrN, TiN, ZrN, TaN and NbN were deposited using an unbalanced magnetron sputtering system with two different degrees of unbalancing to investigate the effect of the degree of unbalancing on both plasma characteristics and film properties. The degree of unbalancing was determined by an extensive characterization of the magnetic field fluxes in the X-Z plane perpendicular to the target. Then, the plasma parameters, such as electron temperature, plasma potential, plasma density and ion current density, were obtained for each target and as a function of the unbalance coefficient. The film microstructure, hardness, corrosion and wear resistant were measured to determine the effect of the degree of unbalancing on these properties. The results suggested that the degree of unbalancing, through the variations induced in the ion bombardment and plasma ionization, had a strong influence on the film hardness, microstructure and preferred orientation.

In vitro cytotoxicity of amorphous carbon films.

Amorphous carbon (a-C), carbon nitride (a-CN) and titanium films were deposited on stainless steel substrates (SS) using a dc magnetron sputtering system attached to a high vacuum chamber. Films were deposited using a base pressure of 1.3x10(-4) Pa. For the carbon films a pure graphite target was eroded in an Argon plasma. For the case of the a-CN films, the Ar flux was substituted by 100% N2 gas. Titanium films were deposited in a different chamber, using a pure Ti target and an argon plasma. In vitro studies were carried out on the coated samples using human osteoblasts cells. Cytotoxicity of carbon films was assessed by cellular adhesion and proliferation, as determined by direct cellular counting using a spectroscopic technique and a well-defined standard curve. Osteoblasts cells were also grown on uncoated steel and prepared Petri dishes for comparison. The percentage of osteoblasts adhesion measured at 24 hrs attained maximum values for the a-C films. Similarly, cellular proliferation evaluated at three, five and seven days showed an outstanding increase of osteoblasts cells for the a-C and Ti coatings in contrast to the uncoated steel. The cell functionality was evaluated by the MTT test after incubation periods of 3, 5 and 7 days. The absorbance values obtained for a-C, a-CN and Ti surfaces resulted significantly higher with respect to the positive control, indicating that the surface did not induce any toxic effect. Preliminary bio-mineralization was evaluated by measuring the elemental composition of the mineral grown on the substrates after periods up to 14 days.