Temporin-Like Peptides Show Antimicrobial and Anti-Biofilm Activities against Streptococcus mutans with Reduced Hemolysis.

In our previous study, temporin-GHaR (GHaR) showed potent antimicrobial activity with strong hemolytic toxicity. To overcome its weakness, we designed GHaR6R, GHaR7R, GHaR8R, GHaR9R, and GHaR9W by changing the number of positive charges and the hydrophobic surface of GHaR. With the exception of GHaR7R, the hemolytic toxicity of the derived peptides had been reduced, and the antimicrobial activities remained close to the parent peptide (except for GHaR9R). GHaR6R, GHaR7R, GHaR8R, and GHaR9W exhibited a great bactericidal effect on Streptococcus mutans (S. mutans), which is one of the main pathogens causing dental caries. According to the membrane permeation and scanning electron microscope (SEM) analysis, these derived peptides targeted to the cell membranes of planktonic bacteria, contributing to the disruption of the membrane integrity and leakage of the intracellular contents. Moreover, they inhibited the formation of biofilms and eradicated the mature biofilms of S. mutans. Compared with GHaR7R, the derived peptides showed less cytotoxicity to human oral epithelial cells (HOECs). The derived peptides are expected to be the molecular templates for designing antibacterial agents to prevent dental caries.

Synthesis of sheet-like polypyrrole nanowires for the microextraction of trace residues of pyrethroid pesticides in human plasma and molecular dynamics-aided study of adsorption mechanism.

The synthesized sheet-like polypyrrole (ppy) nanowires were used as solid phase extraction materials, followed by gas chromatography-mass spectrometry (GC-MS) for the detection of traces residues of pyrethroid pesticides in human plasma. A multiresidue method was developed and verified for the determination of trace pyrethroid residues (transfluthrin, allethrin, resmethrin, fenpropathrin, etofenprox, fenvalerate) in human plasma. In this study, using the cationic surfactant cetyltrimethylammonium bromide (CTAB) as a soft template, ppy nanowires with regular morphology were prepared by oxidative polymerization. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and other techniques were employed for characterization. Molecular dynamics analyses were used to simulate the adsorption mechanism of each pyrethroid and ppy nanowires. Based on density analysis, molecular recognition analysis, and binding energy, the van der Waals force was considered as an important driving force for the adsorption of pyrethroids and ppy nanowires. The limits of detection (LOD) of six pyrethroids were 0.008-0051 ng mL-1, and the limits of quantification (LOQ) were 0.028-0.162 ng mL-1. The relative standard deviations of ppy nanowires were 2.12-5.09%, and the recoveries of six pyrethroids ranged from 76.9 to 110.4%. The enrichment factors were within the range of 47.09-51.30. The experimental results showed that the method could be an efficient detection method for trace residue analysis of pyrethroid pesticides in complex biological samples. It would be advantageous for clinical monitoring and toxicological studies of pyrethroids.

Amino Acid Profiling Study of Psidium guajava L. Leaves as an Effective Treatment for Type 2 Diabetic Rats.

Type 2 diabetes mellitus (T2DM) has become a major disease threatening human health worldwide. At present, the treatment of T2DM cannot cure diabetes and is prone to many side effects. Psidium guajava L. leaves have been reported to possess hypoglycemic activity, and they have been widely used in diabetes treatment in the folk. However, the antidiabetic mechanism has not been clearly explained. Also, the change in amino acid profile can reflect a metabolic disorder and provide insights into system-wide changes in response to physiological challenges or disease processes. The study found that P. guajava L. leaves can decrease fasting blood glucose and lipid levels in type 2 diabetic rats induced by streptozotocin. Through the analysis of amino acid profiling following 20 days of gavage administration, the concentration data were modeled by principal component analysis and orthogonal partial least squares discriminant analysis to find the different metabolites and related metabolic pathways (including cysteine and methionine metabolism, valine, leucine, and isoleucine biosynthesis, phenylalanine, tyrosine, and tryptophan biosynthesis) for the explanation of the hypoglycemic mechanism of P. guajava L., which provides an experimental and theoretical basis for diabetes prediction and for the development of new drugs for the treatment of diabetes.