High-Yield Production of Nano-Lateral Size Graphene Oxide by High-Power Ultrasonication.

Nanographene oxide (GOn) constitutes a nanomaterial of high value in the biomedical field. However, large scale production of highly stable aqueous dispersions of GOn is yet to be achieved. In this work, we explored high-power ultrasonication as a method to reduce particle size of GO and characterized the impact of the process on the physicochemical properties of the material. GOn was obtained with lateral dimensions of 99 ± 43 nm and surface charge of -39.9 ± 2.2 mV. High-power ultrasonication enabled an improvement of stability features, particularly by resulting in a decrease of the average particle size, as well as zeta potential, in comparison to GO obtained by low-power exfoliation and centrifugation (287 ± 139 nm; -29.7 ± 1.2 mV). Remarkably, GOn aqueous dispersions were stable for up to 6 months of shelf-time, with a global process yield of 74%. This novel method enabled the production of large volumes of highly concentrated (7.5 mg mL-1) GOn aqueous dispersions. Chemical characterization of GOn allowed the identification of characteristic oxygen functional groups, supporting high-power ultrasonication as a fast, efficient, and productive process for reducing GO lateral size, while maintaining the material's chemical features.

Near-Infrared Radiation-Based Mild Photohyperthermia Therapy of Non-Melanoma Skin Cancer with PEGylated Reduced Nanographene Oxide.

Using a one-step thermal reduction and non-covalent chemical functionalization process, PEGylated reduced nanographene oxide (rGOn-PEG) was produced from nanographene oxide (GOn) and characterized in terms of particle size, dispersion stability, chemistry, and photothermal properties, in view of its use for photothermal therapy (PTT) of non-melanoma skin cancer. GOn infrared spectrum presented more intense bands assigned to oxygen containing functional groups than observed for rGOn-PEG. GOn C/O ratio decreased more than 50% comparing with rGOn-PEG and nitrogen was present in the latter (N at % = 20.6) due to introduction of PEG-NH2. Thermogravimetric analysis allowed estimating the amount of PEG in rGOn-PEG to be of about 56.1%. Simultaneous reduction and PEGylation increased the lateral dimensions from 287 ± 139 nm to 521 ± 397 nm, as observed by transmission electron microscopy and dynamic light scattering. rGOn-PEG exhibited ≈13-fold higher absorbance in the near-infrared radiation (NIR) region, as compared to unmodified GOn. Low power (150 mW cm-2) NIR irradiation using LEDs resulted in rGOn-PEG heating up to 47 °C, which is within the mild PTT temperature range. PEGylation strongly enhanced the dispersibility of rGOn in physiological media (phosphate buffered saline, fetal bovine serum, and cell culture medium) and also improved the biocompatibility of rGOn-PEG, in comparison to GOn (25-250 µg mL-1). After a single NIR LED irradiation treatment of 30 min, a decrease of ≈38% in A-431 cells viability was observed for rGOn-PEG (250 µg mL-1). Together, our results demonstrate the potential of irradiating rGOn-PEG using lower energy, cheaper, smaller, and safer LEDs, as alternative to high power lasers, for NIR mild hyperthermia therapy of cancer, namely non-melanoma skin cancer.

Genetic variation in the conjugative plasmidome of a hospital effluent multidrug resistant Escherichia coli strain.

Bacteria harboring conjugative plasmids have the potential for spreading antibiotic resistance through horizontal gene transfer. It is described that the selection and dissemination of antibiotic resistance is enhanced by stressors, like metals or antibiotics, which can occur as environmental contaminants. This study aimed at unveiling the composition of the conjugative plasmidome of a hospital effluent multidrug resistant Escherichia coli strain (H1FC54) under different mating conditions. To meet this objective, plasmid pulsed field gel electrophoresis, optical mapping analyses and DNA sequencing were used in combination with phenotype analysis. Strain H1FC54 was observed to harbor five plasmids, three of which were conjugative and two of these, pH1FC54_330 and pH1FC54_140, contained metal and antibiotic resistance genes. Transconjugants obtained in the absence or presence of tellurite (0.5 µM or 5 µM), arsenite (0.5 µM, 5 µM or 15 µM) or ceftazidime (10 mg/L) and selected in the presence of sodium azide (100 mg/L) and tetracycline (16 mg/L) presented distinct phenotypes, associated with the acquisition of different plasmid combinations, including two co-integrate plasmids, of 310 kbp and 517 kbp. The variable composition of the conjugative plasmidome, the formation of co-integrates during conjugation, as well as the transfer of non-transferable plasmids via co-integration, and the possible association between antibiotic, arsenite and tellurite tolerance was demonstrated. These evidences bring interesting insights into the comprehension of the molecular and physiological mechanisms that underlie antibiotic resistance propagation in the environment.

Applications of optical DNA mapping in microbiology.

Optical mapping (OM) has been used in microbiology for the past 20 years, initially as a technique to facilitate DNA sequence-based studies; however, with decreases in DNA sequencing costs and increases in sequence output from automated sequencing platforms, OM has grown into an important auxiliary tool for genome assembly and comparison. Currently, there are a number of new and exciting applications for OM in the field of microbiology, including investigation of disease outbreaks, identification of specific genes of clinical and/or epidemiological relevance, and the possibility of single-cell analysis when combined with cell-sorting approaches. In addition, designing lab-on-a-chip systems based on OM is now feasible and will allow the integrated and automated microbiological analysis of biological fluids. Here, we review the basic technology of OM, detail the current state of the art of the field, and look ahead to possible future developments in OM technology for microbiological applications.