ABSTRACT
A magnetic biochar nanomaterial derived from fungal hyphae was introduced into the sample preparation field. The magnetic fungal hyphae-derived biomass carbon (MFHBC) could be produced by a controllable hydrothermal method. In order to obtain the best sorbent for magnetic solid-phase extraction (MSPE), the reaction conditions containing temperature, time and the consumption of fungal hyphae were investigated. A series of MFHBC materials were characterized by vibrating sample magnetometers, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. A material with a satisfactory saturation magnetization (21.58 emu g-1) and largest surface area (88.06 m2 g-1) was selected as the sorbent to extract ten typical organochlorine pesticides (OCPs). The extraction conditions were optimized as 20 mL of sample solution with 70 mg of sorbent and 2.0 g of NaCl oscillated at 50 °C for 5.0 min. And the optimum desorption was performed by oscillating sorbent in 1.0 mL acetonitrile for 5.0 min. Then, the MFHBC-based MSPE-GC-MS/MS methods were established for different samples including water samples, tea beverages, and Chinese traditional medicines. The linearities were 10-2500 ng L-1 or 100-25,000 ng kg-1, and the limits of detection were 0.3-13.9 ng L-1 for water sample, 0.1-9.7 ng L-1 for tea beverage samples, 0.1-21.4 ng L-1 for Shenqi Fuzheng injection samples, and 7.2-278.3 ng kg-1 for Astragali Radix decoction pieces. Except for satisfactory repeatability (RSDs ≤13.8%) in intra-day and inter-day tests (n = 3), the reproducibility (RSDs ≤13.5%, n = 3) of MFHBC was acceptable. The methods were applied in the determination of OCPs from above real samples, with the recoveries of 80.5-117.2% and the RSDs (n = 3) <8.9%. The methods were suitable in the sensitive determination of OCPs from simple to complex matrix samples.
ABSTRACT
Photodynamic therapy (PDT) has become an effective antibiosis method for overcoming antibiotic resistance. In this study, we developed a versatile bacterial membrane-binding chimeric peptide PpIX-[PEG8-(KLAKLAK)2]2 (denoted as PPK) by conjugating a photosensitizer protoporphyrin IX (PpIX) with an antimicrobial peptide (KLAKLAK)2 (KLA) for effective photodynamic inactivation of bacteria. The chimeric peptide PPK with positively charged properties and an α-helical conformation could rapidly bind to microbial cells through electrostatic interactions and membrane insertion. Moreover, PPK could disrupt the bacterial membrane and further elicit lipid bilayer leakage to kill bacteria by toxic reactive oxygen species (ROS) generated by PpIX under 660 nm light. In vitro experiments demonstrated that cationic PPK possessed excellent antimicrobial activity against both Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli). Afterward, PPK also exhibited perfect therapeutic effects on S. aureus-infected mice without any systemic side effects. This chimeric peptide PPK will show great potential for photodynamic antibiosis.
