Atmospheric Pressure Plasma Activation of Hydroxyapatite to Improve Fluoride Incorporation and Modulate Bacterial Biofilm.

Despite the technological progress of the last decade, dental caries is still the most frequent oral health threat in children and adults alike. Such a condition has multiple triggers and is caused mainly by enamel degradation under the acidic attack of microbial cells, which compose the biofilm of the dental plaque. The biofilm of the dental plaque is a multispecific microbial consortium that periodically develops on mammalian teeth. It can be partially removed through mechanical forces by individual brushing or in specialized oral care facilities. Inhibition of microbial attachment and biofilm formation, as well as methods to strengthen dental enamel to microbial attack, represent the key factors in caries prevention. The purpose of this study was to elaborate a cold plasma-based method in order to modulate microbial attachment and biofilm formation and to improve the retention of fluoride (F-) in an enamel-like hydroxyapatite (HAP) model sample. Our results showed improved F retention in the HAP model, which correlated with an increased antimicrobial and antibiofilm effect. The obtained cold plasma with a dual effect exhibited through biofilm modulation and enamel strengthening through fluoridation is intended for dental application, such as preventing and treating dental caries and enamel deterioration.

Hybrid Nanostructures Obtained by Transport and Condensation of Tungsten Oxide Vapours onto CNW Templates.

We present hybrid nanomaterial architectures, consisting of carbon nanowalls (CNW) templates decorated with tungsten oxide nanoparticles, synthesized using a mechanism based on tungsten oxide sublimation, vapor transport, followed by vapor condensation, in the absence or presence of plasma. The key steps in the decoration mechanism are the sublimation of tungsten oxides, when are exposed in vacuum at high temperature (800 °C), and their redeposition on colder surfaces (400-600 °C). The morphology and chemical composition of the hybrid architectures, as obtained from Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy, are discussed with respect to substrate nature and the physical conditions of synthesis. We pointed out that the decoration process is strongly dependent on the temperature of the CNW templates and plasma presence. Thus, the decoration process performed with plasma was effective for a wider range of template temperatures, in contrast with the decoration process performed without plasma. The results are useful for applications using the sensing and photochemical properties of tungsten oxides, and have also relevance for fusion technology, tungsten walls erosion and material redeposition being widely observed in fusion machines.

In Vitro Human Microbiota Response to Exposure to Silver Nanoparticles Biosynthesized with Mushroom Extract.

The ability to orally administer silver nanoparticles (AgNPs) in enteric capsules implies a direct interaction with the colon microbiota. The in vitro effect provides a portrayal of the functional properties under in vivo conditions. The purpose of this study was to describe a green AgNP synthesis process, using aqueous extract from Lactarius piperatus mushroom, and to characterize the nanomaterial. We determined its antimicrobial and antioxidant effects in vitro in the microbiota of healthy individuals via the GIS1 system-a colon transit simulator. Per the quantitative polymerase chain reaction (qPCR) results, the antimicrobial properties of the AgNPs affected the initial share of different enteric species by decreasing the Bacteroides, Enterobacteriaceae, and Lactobacillus populations and favoring the Bifidobacterium group. The association between AgNPs and wild mushroom L. piperatus extract had a synergistic antibacterial activity against various pathogenic microorganisms while the mushroom extract reduced biofilm formation. Administration of AgNP maintained its constant antioxidant status, and it was correlated with a reduction in ammonium compounds. The physicochemical characterization of these NPs complemented their biochemical characterization. The maximum ultraviolet-visible spectroscopy (UV-VIS) absorbance was observed at 440 nm, while the Fourier transform infrared (FT-IR) spectrum reached a peak at 3296 cm⁻1, which was correlated with the high-performance liquid chromatographic analysis (HPLC). The major phenolic compound was homogentisic acid. The size (49 ± 16 nm in diameter) and spherical shape of the NPs were correlated with their biological effects in vitro.