Zhilan Sun

Clostridium perfringens is an important foodborne pathogen, and due to the lack of aptamers, its detection has been dependent on DNA extraction. It is not only time-consuming and costly but also unable to distinguish between live and dead bacteria. Herein, a high affinity and specificity aptamer (K_d = 66.91 ± 22.02 nM) targeting C. perfringens was first reported, which was screened by the whole-bacteria SELEX. Building on this, we developed a reusable dual-mode aptasensor based on a bipolar electrode (BPE) system. The cathode end was used to modulate the current through the extracellular electron transfer (EET) mechanism of living bacteria, and CeO₂@polyaniline (CeO₂@PANI) nanocomposite was utilized to collect voltage at the anode. In addition, connecting an LED in series with the BPE not only provided a G-value signal but also allowed the BPE to be reused (12 times). Ultimately, the synergistic effect of the cathode and anode resulted in detection limits of 2.50 CFU/mL (voltage) and 2.58 CFU/mL (G-value) for the aptasensor. Benefiting from the physical action of BPE, the matrix effect was less than 7% in both chicken breast and milk. Furthermore, the aptasensor achieved consistent results with the qPCR assay in the testing of 48 actual samples. And the combination of the aptamer and BPE reduced the detection time to 3 min. This method not only provides a new direction for BPE to be reusable but more importantly provides new ideas for the identification of live and dead bacteria.

Clostridium perfringens is a significant foodborne pathogen in chicken products. Rapid on‐site detection of C. perfringens is crucial for mitigating the incidence of foodborne illnesses by enabling the prompt identification and recall of contaminated food products. A rapid and visual detection method for C. perfringens in chicken products was developed using helical loop‐mediated isothermal amplification (HAMP) technology combined with SYBR Green I fluorescent staining. The reaction temperature, time, and reagent concentrations of HAMP technique were optimized firstly. HAMP displayed high specificity, effectively distinguishing C. perfringens from 18 other common pathogens in chicken products. HAMP also exhibited higher sensitivity (78 fg/µL) compared to endpoint PCR and real‐time quantitative PCR (qPCR). The detection limit of HAMP for non‐enriched samples was 6.8 × 10 ² CFU/g, which improved to 68 and 6.8 CFU/g after 5 and 10 h of enrichment, respectively. The detection limit of HAMP was lower by 2 and 1 orders of magnitude compared to endpoint PCR and qPCR under the same conditions. On‐site testing of commercially available ready‐to‐eat chicken products showed that HAMP had the same results as traditional culture methods, indicating the significant potential of HAMP for on‐site detection of C. perfringens . This method offered a rapid, accurate, and visual means of detecting C. perfringens in chicken products, making it well‐suited for on‐site testing. This research represented the first use of the HAMP method for detecting C. perfringens .

Pseudomonas aeruginosa is one of the foodborne pathogenic bacteria that greatly threatens human health. An ultrasensitive technology for P. aeruginosa detection is urgently demanded. Herein, based on the mechanism of aptamer-specific recognition, an electrochemical-colorimetric dual-mode ultrasensitive sensing strategy for P. aeruginosa is proposed. The vertices of DNA tetrahedral nanoprobes (DTNPs), that immobilized on the gold electrode were modified with P. aeruginosa aptamers. Furthermore, the G-quadruplex, which was conjugated with a P. aeruginosa aptamer, was synthesized via rolling circle amplification (RCA). Once P. aeruginosa is captured, a hemin/G-quadruplex, which possesses peroxidase-mimicking activity, will separate from the P. aeruginosa aptamer. Then, the exfoliated hemin/G-quadruplexes are collected for oxidation of the 3,3′,5′,5′-tetramethylbenzidine for colorimetric sensing. In the electrochemical mode, the hemin/G-quadruplex that is still bound to the aptamer catalyzes polyaniline (PANI) deposition and leads to a measurable electrochemical signal. The colorimetric and electrochemical channels demonstrated a good forward and reverse linear response for P. aeruginosa within the range of 1–10⁸ CFU mL⁻¹, respectively. Overall, compared with a traditional single-mode sensor for P. aeruginosa, the proposed dual-mode sensor featuring self-calibration not only avoids false positive results but also improves accuracy and sensitivity. Furthermore, the consistency of the electrochemical/colorimetric assay was verified in practical meat samples and showed great potential for applications in bioanalysis.

Spoilage bacteria play a remarkable role in the spoilage of chilled chicken. In this paper, a total of 42 isolates belonging to 16 species of four genera were isolated from chilled chicken and displayed different characterizations of psychrotrophic spoilage. Six isolates of J7, J8, Q20, Q23, R1, and R9 with differences in proteolytic capabilities were further characterized for in situ spoilage potential evaluation. Pseudomonas lundensis J8 exhibited the strongest spoilage potential in situ, displaying a fast growth rate, increased pH velocity, high total volatile basic nitrogen, and high peptide content in the chicken samples. The volatile flavor analysis of chicken samples via electronic nose indicated that the content of characteristic odors representing spoilage, including sulfides, organic sulfide, and hydride, increased during storage. Additionally, the principle component and correlation analyses revealed that the spoilage odors produced by different species of bacteria were significantly different and positively correlated with the results of protease activity in vitro. The characteristics of spoilage bacteria in chilled chicken provided a comprehensive insight into microbial assessment during storage.

Clostridium perfringens is a major pathogen causing foodborne illnesses. In this experiment, the inactivation effects of heat and lactic acid (LA) treatments on C. perfringens spores was investigated. Heat treatment (80 °C, 90 °C and 100 °C), LA (0.5% and 1%), and combined LA and heat treatments for 30 and 60 min were performed. Residual spore counts showed that the count of C. perfringens spores was below the detection limit within 30 min of treatment with 1% LA and heat treatment at 90 °C. Scanning electron microscopy and confocal scanning laser microscopy results showed that the surface morphology of the spores was severely disrupted by the co-treatment. The particle size of the spores was reduced to 202 nm and the zeta potential to −3.66 mv. The inner core of the spores was disrupted and the co-treatment resulted in the release of 77% of the nuclear contents 2,6-pyridinedicarboxylic acid. In addition, the hydrophobicity of spores was as low as 11% after co-treatment with LA relative to the control, indicating that the outer layer of spores was severely disrupted. Thus, synergistic heating and LA treatment were effective in inactivating C. perfringens spores.

Clostridium perfringens is an important foodborne pathogen, which has caused serious public health problems worldwide.