Fabrication of Te and Te-Au Nanowires-Based Carbon Fiber Fabrics for Antibacterial Applications

Enhancing tellurite and selenite bioconversions by overexpressing a methyltransferase from Aromatoleum sp. CIB

Pollution by metalloids, e.g., tellurite and selenite, is of serious environmental concern and, therefore, there is an increasing interest in searching for ecologically friendly solutions for their elimination. Some microorganisms are able to reduce toxic tellurite/selenite into less toxic elemental tellurium (Te) and selenium (Se). Here, we describe the use of the environmentally relevant β-proteobacterium Aromatoleum sp. CIB as a platform for tellurite elimination. Aromatoleum sp. CIB was shown to tolerate 0.2 and 0.5 mM tellurite at aerobic and anaerobic conditions, respectively. Furthermore, the CIB strain was able to reduce tellurite into elemental Te producing rod-shaped Te nanoparticles (TeNPs) of around 200 nm length. A search in the genome of Aromatoleum sp. CIB revealed the presence of a gene, AzCIB_0135, which encodes a new methyltransferase that methylates tellurite and also selenite. AzCIB_0135 orthologs are widely distributed in bacterial genomes. The overexpression of the AzCIB_0135 gene both in Escherichia coli and Aromatoleum sp. CIB speeds up tellurite and selenite removal, and it enhances the production of rod-shaped TeNPs and spherical Se nanoparticles (SeNPs), respectively. Thus, the overexpression of a methylase becomes a new genetic strategy to optimize bacterial catalysts for tellurite/selenite bioremediation and for the programmed biosynthesis of metallic nanoparticles of biotechnological interest.

Biocompatible tellurium nanoneedles with long-term stable antibacterial activity for accelerated wound healing

Tellurium (Te) nanomaterials (NMs) have emerged as a new antibacterial candidate to respond to the complex global health challenge of bacterial resistance. Herein, Te nanoneedles (NNs) that act both chemically and physically on bacteria are synthesized by a facile method using Na₂TeO₃, urea and glucose. It is found that the prepared Te NNs have a strong affinity to the cell membrane of bacteria and subsequently promote the generation of reactive oxygen species (ROS) in bacteria, resulting in an excellent antibacterial effect toward Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). What's more, this needle-like morphology also can physically damage the bacterial cell membranes. The Te NNs per se are inert in mammalian cells to produce ROS at a proper concentration, indicating considerable biocompatibility of this material. As a proof-of-concept, the antibacterial Te NNs were used as an anti-inflammatory reagent for promoting bacteria-infected wound healing in vivo, during which Te NNs caused no evident side effects to major organs in mice. Additionally, the antibacterial activity is maintained in the presence of surface oxidation of Te NNs after long-term dispersion in phosphate buffered saline solution. The needle-like Te NMs with long-term antibacterial stability and good biocompatibility have great potential for the treatment of associated infectious diseases.

Plug-In Safe-by-Design Nanoinorganic Antibacterials

Due to antimicrobial resistance and the adverse health effects that follow broad and inappropriate use of antibacterial agents, new classes of antibacterials with broad and strong bactericidal activity and safety for human use are urgently required globally, increasingly so with the onset of climate change. However, R&D in this field is known to be rarely profitable, unless a cost-effective, flexible, and convenient platform that ensures the production of workable candidate antibacterials can be developed. To address this issue, inorganic nanomaterials have been considered for their bactericidal activities, yet further investigations of composition crystalline modifications and/or surface biomaterial coatings are still required to provide effective and safe antibacterial nanoparticles. In this study, we developed a plug-in system comprising a spark plasma reactor and a flow heater under nitrogen gas flow to supply precursor inorganic nanoparticles (Cu-Te configuration) that can be modulated in-flight at different temperatures. From antibacterial and toxicological assays in both in vitro and in vivo models, bactericidal and toxicological profiles showed that the plug-in system-based platform can be used to identify key parameters for producing safe-by-design agents with antibacterial activity [>88% (in vitro) and >80% (in vivo) in antibacterial efficiency] and safety (>65% in in vitro viability and >60% in in vivo survival rate).

Comparison of cytocompatibility and anticancer properties of traditional and green chemistry-synthesized tellurium nanowires

Background

Traditional physicochemical approaches for the synthesis of compounds, drugs, and nanostructures developed as potential solutions for antimicrobial resistance or against cancer treatment are, for the most part, facile and straightforward. Nevertheless, these approaches have several limitations, such as the use of toxic chemicals and production of toxic by-products with limited biocompatibility. Therefore, new methods are needed to address these limitations, and green chemistry offers a suitable and novel answer, with the safe and environmentally friendly design, manufacturing, and use of minimally toxic chemicals. Green chemistry approaches are especially useful for the generation of metallic nanoparticles or nanometric structures that can effectively and efficiently address health care concerns.

Objective

Here, tellurium (Te) nanowires were synthesized using a novel green chemistry approach, and their structures and cytocompatibility were evaluated.

Method

An easy and straightforward hydrothermal method was employed, and the Te nanowires were characterized using transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and optical microscopy for morphology, size, and chemistry. Cytotoxicity tests were performed with human dermal fibroblasts and human melanoma cells (to assess anticancer properties). The results showed that a treatment with Te nanowires at concentrations between 5 and 100 μg/mL improved the proliferation of healthy cells and decreased cancerous cell growth over a 5-day period. Most importantly, the green chemistry -synthesized Te nanowires outperformed those produced by traditional synthetic chemical methods.

Conclusion

This study suggests that green chemistry approaches for producing Te nanostructures may not only reduce adverse environmental effects resulting from traditional synthetic chemistry methods, but also be more effective in numerous health care applications.

In Vitro Activity of 3-Bromopyruvate, an Anticancer Compound, Against Antibiotic-Susceptible and Antibiotic-Resistant Helicobacter pylori Strains

Helicobacter pylori (H. pylori) is a bacterium capable of inducing chronic active gastritis, which in some people, develops into gastric cancers. One of the substances that may be useful in the eradication of this microorganism is 3-Bromopyruvate (3-BP), an anticancer compound with antimicrobial properties. The aim of this article was to determine the activity of 3-BP against antibiotic-susceptible and antibiotic-resistant H. pylori strains. The antimicrobial activity was determined using a disk-diffusion method, broth microdilution method, time-killing assay, and checkerboard assay. The research was extended by observations using light, fluorescence, and scanning electron microscopy. The growth inhibition zones produced by 2 mg/disk with 3-BP counted for 16–32.5 mm. The minimal inhibitory concentrations (MICs) ranged from 32 to 128 μg/mL, while the minimal bactericidal concentrations (MBCs) for all tested strains had values of 128 μg/mL. The time-killing assay demonstrated the concentration-dependent and time-dependent bactericidal activity of 3-BP. The decrease in culturability below the detection threshold (<100 CFU/mL) was demonstrated after 6 h, 4 h, and 2 h of incubation for MIC, 2× MIC, and 4× MIC, respectively. Bacteria treated with 3-BP had a several times reduced mean green/red fluorescence ratio compared to the control samples, suggesting bactericidal activity, which was independent from an induction of coccoid forms. The checkerboard assay showed the existence of a synergistic/additive interaction of 3-BP with amoxicillin, tetracycline, and clarithromycin. Based on the presented results, it is suggested that 3-BP may be an interesting anti-H. pylori compound.