A portable CRISPR-Cas12a triggered photothermal biosensor for sensitive and visual detection of Staphylococcus aureus and Listeria monocytogenes.

The detection of foodborne pathogens is crucial for ensuring the maintenance of food safety. In the present study, a portable CRISPR-Cas12a triggered photothermal biosensor integrating branch hybrid chain reaction (bHCR) and DNA metallization strategy for sensitive and visual detection of foodborne pathogens was proposed. The sheared probes were utilized to block the locker probes, which enabled preventing the assembly of bHCR in the absence of target bacteria, while target bacteria can activate the cleavage of sheared probes through CRISPR-Cas12a. Therefore, the locker probes functioned as initiating chains, triggering the formation of the branching double-stranded DNA consisting of H1, H2, and H3. The silver particles, which were in situ deposited on the DNA structure, functioned as a signal factor for conducting photothermal detection. Staphylococcus aureus and Listeria monocytogenes were selected as the foodborne pathogens to verify the analytical performance of this CRISPR-Cas12a triggered photothermal sensor platform. The sensor exhibited a sensitive detection with a low detection limit of 1 CFU/mL, while the concentration ranged from 100 to 108 CFU/mL. Furthermore, this method could efficiently detect target bacteria in multiple food samples. The findings demonstrate that this strategy can serve as a valuable reference for the development of a portable platform enabling quantitative analysis, visualization, and highly sensitive detection of foodborne bacteria.

Simultaneous high-performance liquid chromatography with diode array detection and time-of-flight mass spectrometric confirmation of the ten bioactive compounds in Semen Sojae Preparatum.

Semen Sojae Preparatum is one of the most widely used traditional Chinese medicines. A reliable and accurate high-performance liquid chromatography with diode array detection method has been developed and validated for the quantitative determination of the ten bioactive compounds contained in Semen Sojae Preparatum. The samples were first extracted by pressurized liquid extraction using 80% ethanol at 100°C for 15 min and three static extraction cycles. Chromatographic separation was conducted on a C18 column using a mobile phase consisting of water and acetonitrile under gradient elution, and the detection wavelength was set at 210 nm. The samples were further analyzed on a high-performance liquid chromatography with time-of-flight mass spectrometry system to confirm the determination results. All the ten analytes were well separated, and the calibration curves showed good linearity. The intra- and interday precisions were evaluated in terms of relative standard deviation values within the ranges of 0.20-1.43% and 0.40-4.78%, respectively. The recoveries for the ten analytes were all in the ranges of 96.2-104.3%, with relative standard deviation values < 3.85%. The established high-performance liquid chromatography method could serve as a reliable and accurate method for the quality evaluation of Semen Sojae Preparatum from different origins.