Wrapping-Trapping versus Extraction Mechanism of Bactericidal Activity of MoS2 Nanosheets against Staphylococcus aureus Bacterial Membrane

Recent progress in hydrogels combined with phototherapy for bacterial infection: A review

Phototherapy has become one of the most effective antibacterial methods due to its associated lack of drug resistance and its good antibacterial effect. For the purpose of avoiding the aggregation and premature release of photosensitive/photothermal agents during phototherapy, they can be mixed into three-dimensional hydrogels. The combination of hydrogels and phototherapy combines the merits of both hydrogels and phototherapy, overcomes the disadvantages of traditional antibacterial methodologies, and has broad application prospects. This review presents recent advancements in phototherapeutic antibacterial hydrogels including photodynamic antibacterial hydrogels, photothermal antibacterial hydrogels, photodynamic and photothermal synergistic antibacterial hydrogels, and other synergistic antibacterial hydrogels involving phototherapy.

Screening of Short-Chain Antimicrobial Peptide LKARI with Broad-Spectrum Bactericidal Properties and Its Application in Promoting Wound Healing

Due to the extensive use of antibiotics, many highly resistant bacteria and extensively resistant bacteria have been produced. In recent years, the increase of drug-resistant bacteria and the resulting proliferation of drug-resistant bacteria have increased the incidence of hospital-acquired infections and caused great harm to human health. Antimicrobial peptides (AMPs) are considered to be an innovative antibiotic and belong to the latest advances in this field. We designed a polypeptide and verified its low minimum inhibitory concentration and broad-spectrum activity against Gram-positive bacteria, Gram-negative bacteria, and fungi in microbiology and pharmacology. Several experiments have confirmed that the screened antimicrobial peptides have significant antidrug resistance and also show significant therapeutic properties in the treatment of systemic bacterial infections. In addition, through our experimental research, it was proved that the antibacterial hydrogel composed of poly(vinyl alcohol), sodium alginate, and antimicrobial peptides had excellent antibacterial properties and showed good wound healing ability.

Cholesterols Induced Distinctive Entry of the Graphene Nanosheet into the Cell Membrane

Graphene nanosheets are highly valued in the biomedical field due to their potential applications in drug delivery, biological imaging, and biosensors. Their biological effects on mammalian cells may be influenced by cholesterols, which are crucial components in cell membranes that take part in many vital processes. Therefore, it is particularly important to investigate the effect of cholesterols on the transport mechanism of graphene nanosheets in the cell membrane as well as the final stable configuration of graphene, which may have an impact on cytotoxicity. In this paper, the molecular details of a graphene nanosheet interacting with a 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC) membrane with cholesterols were studied using molecular dynamics simulations. Results showed that the structure of the graphene nanosheet transits from the cut-in state in a pure DPPC membrane to being sandwiched between two DPPC leaflets when cholesterols reach a certain concentration. The underlying mechanism showed that cholesterols are preferentially adsorbed on the graphene nanosheet, which causes a larger disturbance to the nearby DPPC tails and thus guides the graphene nanosheet into the core of lipid bilayers to form a sandwiched structure. Our results are helpful for understanding the fundamental interaction mechanism between the graphene nanosheet and cell membrane and to explore the potential applications of the graphene nanosheet in biomedical sciences.

Stability of Cytoplasmic Membrane of Escherichia coli Bacteria in Aqueous and Ethanolic Environment

The mechanism of action of any antibacterial agent or disinfectant depends largely on their interaction with the bacterial membrane. Herein, we use the SPICA (surface property fitting coarse graining) force-field and develop a coarse-grained (CG) model for the structure of the cytoplasmic membrane of Escherichia coli (E. coli) and its interaction with water and ethanol. We elucidate the impact of different concentrations of ethanol on the cytoplasmic membrane bilayers and vesicles of E. coli using the CG molecular dynamics (CG MD) simulations. Our modeling approach first focuses on the parametrization of the required force-field for POPG lipid and its interaction with water, ethanol, and POPE lipid. Subsequently, the structural stability of the E. coli bacterial membrane in the presence of high and low concentrations of ethanol is delineated. Both flat bilayers as well as vesicles of E. coli membrane were considered for the CG MD. Our results reveal that, at low ethanol concentrations (<30 mol %), the size of the E. coli vesicles increases with discernible deformations in their shapes. Because of ethanol-induced interdigitation, thinning of the E. coli vesicular membrane is also observed. However, at higher ethanol concentrations (>30 mol %), the integrity of the vesicles is lost because of deteriorating invasion of ethanol molecules into the vesicle bilayer and significant weakening of lipid-lipid interactions. At higher ethanol concentrations (40 and 70 mol %), both the multivesicle and single-vesicle bacterial membranes exhibit a similar rupturing pattern wherein the extraction of lipids from the membrane and formation of aggregates of the component lipids are observed. These aggregates consist of polar head groups of 3-5 POPE/POPG lipids with intertwined nonpolar tails.

Screening of low-toxic zinc oxide nanomaterials and study the apoptosis mechanism of NSC-34 cells

With the increasing application of ZnO nanomaterials (ZnO-NMts) in the biomedical field, it is crucial to assess their potential risks to humans and the environment. Therefore, this study aimed to screen for ZnO-NMts with low toxicity and establish safe exposure limits, and investigate their mechanisms of action. The study synthesized 0D ZnO nanoparticles (ZnO NPs) and 3D ZnO nanoflowers (ZnO Nfs) with different morphologies using a hydrothermal approach for comparative research. The ZnO-NMts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Mouse brain neuronal cells (NSC-34) were incubated with ZnO NMts for 6, 12, and 24 h, and the cell morphology was observed using TEM. The toxic effects of ZnO Nfs on NSC-34 cells were studied using CCK-8 cell viability detection, reactive oxygen species (ROS) measurement, caspase-3 activity detection, Annexin V-FITC/PI apoptosis assay, and mitochondrial membrane potential (Δφm) measurement. The results of the research showed that ZnO-NMts caused cytoplasmic vacuolization and nuclear pyknosis. After incubating cells with 12.5 µg mL-1 ZnO-NMts for 12 h, ZnO NRfs exhibited the least toxicity and ROS levels. Additionally, there was a significant increase in caspase-3 activity, depolarization of mitochondrial membrane potential (Δφm), and the highest rate of early apoptosis.This study successfully identified ZnO NRfs with the lowest toxicity and determined the safe exposure limit to be < 12.5 µg mL-1 (12 h). These findings will contribute to the clinical use of ZnO NRfs with low toxicity and provide a foundation for further research on their potential applications in brain disease treatment.