The exact mechanism behind the antibacterial efficacy of nanoparticles has remained unexplored to date. This study aims to shed light the mechanism adopted using magnesium oxide nanoparticles prepared in ethyl alcohol against gram-negative and gram-positive bacterial cells, and the generation of reactive oxygen species (ROS) is proposed to be the dominant mechanism. This paradigm is supported by the quantification of the hydroxyl radical and superoxide anions produced in the nanoparticle treated and untreated bacterial solutions, and by the reduction of the antibacterial efficiency after the addition of a radical scavenger. The production of free Mg2+ ions from the nanoparticle is supposed to be the causative agent behind this uncontrolled ROS generation, resulting in excessive oxidative stress, which the antioxidants of the bacterial cells are unable to nullify, leading to cell damage. The amount of proteins, carbohydrates and lipids leaked due to the distortion of the cellular membrane is also quantified, and it is observed that their leakage trend varies on the structure of the bacterial cell. FESEM images taken at certain time intervals show the gradual internalization of the nanoparticles, and increasing rupture of bacterial cell membranes, leading to cell necrosis.

An insight into the mechanism of antibacterial activity by magnesium oxide nanoparticles.

http://manuscript.elsevier.com/S0162013422000915/pdf/S0162013422000915.pdf

Synthesis of phytonic silver nanoparticles as bacterial and ATP energy silencer.

The photoelectric response is crucial for photocatalysis, having applications in solar cells and photoelectrochemical (PEC) sensors. In this study, we demonstrate improvements in the near-infrared (NIR)-light-driven PEC response via synergism between reduced graphene oxide (rGO) and MoS2. Intriguingly, rGO modulates the morphology of MoS2, facilitating carrier generation and migration, improving the PEC performance of the resultant rGO-MoS2 sheets (GMS), and yielding an approximately 8-fold increase in the photocurrent compared to that of the pure MoS2. Based on these findings, a NIR-responsive PEC immunosensing platform for the "turn-on" analysis of Escherichia coli O157:H7 on 980 nm light irradiation is reported. Specifically, the device is a three-dimensional magnetic screen-printed paper-based electrode assembled on a home-made PEC cell, and it enables integrated separation and detection. Using a sandwich-type immunocomplex bridged by E. coli O157:H7 and a GMS PEC probe, the immunosensing platform detected E. coli O157:H7 between 5.0 and 5.0 × 106 CFU mL-1, having an extremely low detection limit of 2.0 CFU mL-1. Further, the assay enables the direct analysis of E. coli O157:H7 in milk without the need for pretreatment. Our findings suggest directions for the development of NIR-responsive paper-based PEC materials for portable biomolecule sensing.

Photoelectrochemical Sensors with Near-Infrared-Responsive Reduced Graphene Oxide and MoS2 for Quantification of Escherichia Coli O157:H7.

Amino Acid-Functionalized MoS2 Quantum Dots for Selective Antibacterial Activity

Encapsulating MoS2-nanoflowers conjugated with chitosan oligosaccharide into electrospun nanofibrous scaffolds for photothermal inactivation of bacteria

A novel, recyclable, portable, and low-cost SERS sensor-AuBPs@MoS2@tinfoil box is fabricated layer-by-layer by self-assembly method for the first time, which achieved the purpose of high throughput SERS tracking. Diquat (DQ) is one of the most widely used herbicides in the world since paraquat was banned. Benefiting from the “hot spots” generated by AuBPs@MoS2, the sensor successfully realizes straightforward SERS recognition of DQ in complex compounds, which detection limit is as low as 1.0 × 10−15 M. The preprocessing is not required for the detection of real samples, which promotes the practical application of forensic medicine and environmental engineering.

Recyclable and green AuBPs@MoS2@tinfoil box for high throughput SERS tracking of diquat in complex compounds

Crown monitoring: Trace the dynamic changes of caspase-3 and H2O2 in real-time imaging based on FRET/SERS.

To tackle the devastating microbial infections for the public health, a continuous search for effective and safe nanobiocides based on their prominent nanoscale effects has been extensively explored during past decades. In this study, a green electrolysis method was employed to synthesize silver-doped molybdenum sulfide (Ag@MoS2) composite materials. The obtained nanocomposites exhibited a sheet-like structure with a large specific surface area, which contributed to the efficient loading and refined distribution of silver nanoparticles. G−E. coli and G+S. aureus were used as model bacteria for the antibacterial test, which revealed enhanced antibacterial activity of produced nanocomposites with an identified destructive effect on preformed biofilms. It was found that within 72 hour incubation, 20 μg mL−1 Ag@MoS2 was sufficient to inhibit the growth of E. coli and S. aureus without visible colony formation, pointing to a desirable long-term antibacterial activity. Further a mechanistic antibiosis study of Ag@MoS2 indicated the involvement of a generation of reactive oxygen species. Notably, owing to the well-distributed silver nanoparticles on the nontoxic MoS2 nanosheet, the cytotoxicity evaluation results revealed that produced nanocomposites exhibited negligible toxicity to mammalian cells, and thereby held promising potential for biomedical applications.

/pdf/a-green-electrolysis-of-silver-decorated-mos2-nanocomposite-1615rz7zz3.pdf

A green electrolysis of silver-decorated MoS2 nanocomposite with an enhanced antibacterial effect and low cytotoxicity

Paper-based electrochemical sensor

Paraquat and diquat are well-known toxic herbicides, at least responsible for hundreds of fatal poisoning events worldwide. However, the determination of diquat and paraquat in plasma and urine is very challenging because of their high polarity and double charge characteristics. In this study, we aim to develop a rapid and reliable method for the determination of paraquat and diquat in human plasma and urine by ultraperformance liquid chromatography–tandem mass spectrometry. The chromatographic separation of paraquat and diquat was tested with different chromatographic columns and different mobile phase conditions. The mass parameters were optimized by product ions, source gas flow, cone flow, desolvation temperature, and capillary voltage. The isocratic elution mode gave rapid appearance of peak of paraquat and diquat. The sharp peak shapes for paraquat and diquat were achieved with CORTECS® UPLC® HILIC (100 × 2.1 mm, 1.6 μm) column by adding formic acid and ammonium acetate in mobile phase in isocratic elution mode. The lower limit of quantification of 1.0 ng/mL for paraquat and diquat were achieved using only 50 μL of human plasma or urine. The running time for analysis of both paraquat and diquat was as short as 3.5 min per sample. A rapid and reliable method for the determination of paraquat and diquat was developed and applied to 387 clinical poisoning cases and 22 poisoning cases were found to be paraquat or diquat poisoning.

Development and validation of a sensitive and high throughput UPLC–MS/MS method for determination of paraquat and diquat in human plasma and urine: application to poisoning cases at emergency departments of hospitals

Yang Sun

Papers

Recyclable and green AuBPs@MoS2@tinfoil box for high throughput SERS tracking of diquat in complex compounds

Crown monitoring: Trace the dynamic changes of caspase-3 and H2O2 in real-time imaging based on FRET/SERS.

A green electrolysis of silver-decorated MoS2 nanocomposite with an enhanced antibacterial effect and low cytotoxicity

Paper-based electrochemical sensor

Development and validation of a sensitive and high throughput UPLC–MS/MS method for determination of paraquat and diquat in human plasma and urine: application to poisoning cases at emergency departments of hospitals