Progesterone (P4) belongs to a factor that affects stress response and is a potential carcinogen, and saliva levels are expected to be a standard measurement for clinical diagnosis. In this study, a new type of nanoflower with both recognition functionality and catalytic substrate ability was prepared by copper phosphate, Pt/IrO2 nanocomposites (Pt/IrO2 NPs), streptavidin (SA) and horseradish peroxidase (HRP) via a one-pot co-precipitation strategy. Due to the enhanced catalytic activity and stability of Pt/IrO2@SA@HRP nanoflowers, we developed a powerful and sensitive multiple-catalysis ELISA to monitor progesterone in saliva. Multiple-catalysis ELISA based on a specific antibody and Pt/IrO2@SA@HRP nanoflowers exhibited a linear interval range from 0.217 ng mL−1 to 7.934 ng mL−1. The median inhibitory concentration (IC50) for progesterone is 1.311 ng mL−1 and the limit of detection (LOD = IC10) is 0.076 ng mL−1 in the proposed method. Satisfactory recoveries were in a range of 79.6–107% with an acceptable coefficient of variation (below 10.6%). Results of the multiple-catalysis ELISA and LC-MS/MS had a good coincidence. Our result unraveled that multiple-catalysis ELISA is a potentially serviceable tool for the detection of progesterone in saliva.
Ochratoxin A (OTA) is considered as one of the most hazardous mycotoxins commonly occurring in grains. Thus, the monitoring of OTA is extremely significant. Herein, a synergistic strategy to detect OTA in grains based on the combination of DNA tetrahedron-structured aptamer (DTA) and hybridization chain reaction (HCR) was proposed. Briefly, DTA was assembled on the gold electrode. In the presence of OTA, the trigger DNA on the top of the DTA was exposed to unfold the biotin-modified hairpin structure DNA to HCR. It could conjugate plentiful streptavidin-labeled horseradish peroxidase (SA-HRP) to form polyaniline (PANI), which was regarded as electrochemical active molecule to detect OTA. In this way, the synergistic effect of DTA and HCR not only can provide stable probe structure to improve the recognition rate of OTA, but also can supply a large number of templates to synthesize PANI under mild conditions. As a result, the biosensor has a good analytical performance for OTA in a linear range of 0.05 to 50 ng mL −1 , with a detection limit of 0.017 ng mL −1 . The accuracy of sensor is similar with high-performance liquid chromatography (HPLC) analysis.
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