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A novel bipolar electrode (BPE)-electrochemiluminescence (ECL) device was constructed for the ultra-sensitive detection of Staphylococcus aureus (S. aureus) by combining polymerase chain reaction (PCR) amplification and DNA network-loaded polymethylene blue nanoparticles (pMB NPs). The presence of target triggered the dissociation of double-stranded DNA on Fe 3 O 4 NPs and the release of T strand, which initiated the PCR. The PCR product contains two protruding single-stranded DNA fragments that serve as bridges to connect Au NPs labeled probes. The PCR-Au products were captured by the probes on cathode of BPE to form three-dimensional DNA networks, which offer multiple adsorption sites for pMB NPs, leading to the remarkable enhancement of ECL intensity. Under optimal circumstances, a wide linear range from 10 to 10 8 CFU/mL and a low detection limit of 0.78 CFU/mL were achieved. This research opens new horizons for the application of PCR-based biosensors for the accurate and sensitive measurement of pathogenic bacteria., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Meisheng Wu reports financial support was provided by National Natural Science Foundation of China. Meisheng Wu reports financial support was provided by Qinglan Project of Jiangsu Province of China. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Pathogenic bacteria have a significant impact on food safety. Herein, an innovative dual-mode ratiometric aptasensor was constructed for ultrasensitive and accurate detection of Staphylococcus aureus (S. aureus) based on recycling of DNAzyme activation on gold nanoparticles-functionalized MXene nanomaterials (MXene@Au NPs). Electrochemiluminescent (ECL) emitter-labeled probe DNA (probe 2-Ru) containing the blocked DNAzyme was partly hybridized with aptamer and then captured by electrochemical (EC) indicator-labeled probe DNA (probe 1-MB) on electrode surface. When S. aureus presented, the conformation vibration of probe 2-Ru activated the blocked DNAzymes, leading to recycling cleavage of probe 1-MB and ECL tag close to electrode surface. Based on the reverse change tendencies of ECL and EC signals, aptasensor achieved S. aureus quantification from 5 to 10 8 CFU/mL. Moreover, the self-calibration characteristic of the aptasensor with dual-mode ratiometric readout ensured the reliable measurement of S. aureus in real samples. This work showed useful insight into sensing foodborne pathogenic bacteria., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Pathogenic bacteria infections pose a major threat to human health which can be found in contaminated food and infected humans. Herein, an electrochemical sensor was developed for pathogenic bacteria assay using a dual amplification strategy of polymethylene blue nanoparticles (pMB NPs) and dumbbell hybridization chain reaction (DHCR). The strong binding ability of aptamer to targets endowed outstanding performance in identifying Staphylococcus aureus (S. aureus) among other typical bacteria. The released T strands were hybridized with capture DNA on electrode surface which triggered DHCR in the presence of two dumbbell-shaped helper DNA, leading to the formation of extended and tight dsDNA polymers. In combination with pMB NPs (redox indicators), S. aureus was quantitatively detected in a range of 10-10 8 CFU/mL and the detection limit reached 1 CFU/mL. Moreover, this sensor was successfully applied for S. aureus detection in human serum and foods, demonstrating the reliability in practical applications., (Copyright © 2022 Elsevier Ltd. All rights reserved.)