No abstract

The abnormal expression of microRNA (miRNA) can affect the RNA transcription and protein translation, leading to tumor progression and metastasis. Currently, the accurate detection of aberrant expression of miRNA, particularly using a portable detection system, remains a great challenge. Herein, a novel dual-mode biosensor with high sensitivity and robustness for miR-21 detection was developed based on the cis-cleavage and trans-cleavage activities of Cas12a. miRNA can be combined with hairpin DNA-horseradish peroxidase anchored on a CdS/g-C 3 N 4 /B-TiO 2 photoelectrode, thus the nonenzymatic amplification was triggered to form numerous HRP-modified double-stranded DNA (HRP-dsDNA). Then, HRP-dsDNA can be specifically recognized and efficiently cis-cleaved by Cas12a nucleases to detach HRP from the substrate, while the remaining HRP on HRP-dsDNA can catalyze 4-chloro-1-naphthol (4-CN) to form biocatalytic precipitation (BCP) on the surface of the photoelectrode, and thus the photocurrent can be changed. Meanwhile, the trans-cleavage ability of Cas12a was activated, and nonspecifically degrade the FQ-reporter and a significant fluorescence signal can be generated. Such two different kinds of signals with independent transmission paths can mutually support to improve the performance of the detection platform. Besides, a portable device was constructed for the point-of-care (POC) detection of miR-21. Moreover, the dual-mode detection platform can be easily expanded for the specific detection of other types of biomarkers by changing the sequence of hairpin DNA, thereby promoting the establishment of POC detection for early cancer diagnosis.

No abstract

The detection of rosiglitazone (RSG) in food is of great importance since the excessive intake of RSG could cause adverse effects on the human body. Although liquid chromatography–mass spectrometry and gas chromatography–mass spectrometry are the preliminary methods for the detection of hazardous materials in food, they are not suitable for point-of-care or on-site detection. Herein, a time-based readout (TBR) device with an application software (APP) controlled by a smart phone was developed for the sensitive and selective immunoassay of RSG. The homemade TBR device was based on a two-electrode system, where the immune molecule-modified glassy carbon electrode was used as the bioanode, and Prussian blue-modified FTO was used as the cathode. By using Au-modified octahedral Cu2O with high catalytic activity as mimetic peroxidase, an insulating layer was generated on the cathode by catalyzing 4-chloro-1-naphthol (4-CN) into benzo-4-chlorohexadienone (B4Q). The time to reach a fixed potential varied indirectly with the concentrations of RSG and was recognized by the APP, while the electrochromic property on the cathode was also correspondingly changed. Under optimum conditions, both the square root of the time and the chroma value of the electrochromism exhibited linear responses for the detection of RSG ranging from 5 × 10–10 to 5 × 10–7 g/L, while the limits of detection were 8.2 × 10–11 and 1.3 × 10–10 g/L, respectively. With easy operation and portability, this TBR device showed a promising application for point-of-care monitoring of hazardous materials in food or the environment.