Guanyue Gao

The timely identification of drug-resistant pathogens and rapid differentiation of antibacterial mechanisms are critical in combating the escalating crisis of antimicrobial resistance. However, traditional broth culturing methods are inherently time-consuming and lack single-cell sensitivity. In this study, we reported a highly responsive biosensing platform based on single-entity impact electrochemistry (SIE) to rapidly differentiate bacterial activity at the single bacterium level. This method utilized p-benzoquinone (BQ) and BQ-K3Fe(CN)6 as redox mediators that were continuously reduced by the bacterial respiratory chain. Upon the collision of an individual bacterium with the ultramicroelectrode, these mediators were re-oxidized, generating transient current spikes that serve as a direct indicator of cellular viability. By tracking these distinct electrochemical signals, we successfully discriminated the responses of Escherichia coli to three antibacterial agents. Specifically, the heavy metal stress induced by Pb2+ exposure resulted in a progressive decline in collision spike amplitude, with the total transferred charge decreasing from (7.51 ± 0.48) × 10–2 pC to (2.50 ± 0.14) × 10–2 pC per bacterium. The bacteriostatic effect of doxycycline yielded negligible immediate signal change due to its protein synthesis inhibition mechanism. In contrast, the membrane-disrupting effect of polymyxin B triggered a rapid cessation of collision signals alongside an increase in total current amplitude due to the leakage of intracellular redox contents. Based on these unique electrochemical signatures, we successfully identified polymyxin B-resistant E. coli mutants and achieved rapid validation of alternative antibiotics against this drug-resistant strain. This work expanded the analytical capabilities of SIE, offering a highly efficient platform for bacterial phenotypic screening and drug resistance monitoring.

The extensive use of the alkaloid quinine (QN) in the cosmetic and food industries has induced major concerns relating to its impact on human health, considering its potential toxicity. Therefore, developing sensitive and selective electrochemical sensors is crucial for monitoring QN in environmental, food, and pharmaceutical samples. To respond to this need, a surfactant-supported green synthesis approach, based on a straightforward, organic solvent-free hydrothermal method was employed to synthesize highly crystalline pseudospherical bismuth oxychloride (BiOCl) nanoparticles. This material was used for the enrichment of carbon paste electrodes and its further utilization for the detection and quantification of quinine. They have superior electrocatalytic performance, due to their size and morphology, and facilitate the interactions of the target with the electrode surface. Under optimal operating conditions, differential pulse voltammetry demonstrated a remarkable feature: a broad linear working range of 10 to 140 μM, a detection limit of 0.14 μM, and a high sensitivity of 1.995 μA μM⁻¹ cm⁻². The suggested method’s satisfactory sensitivity, along with its good stability, repeatability, and reproducibility, strongly point to a possible use for identifying quinine in real samples.

Staphylococcus aureus is one of the leading causes of skin and soft tissue infections, and it is even life-threatening if it enters the bloodstream, lung or heart. In the present work, we proposed a novel colorimetric biosensor for the detection of S. aureus through hydrogen peroxide consumption. An onion-like carbon nanozyme with high peroxidase-like activity was prepared, which competed with the endogenous catalase of S. aureus in consuming hydrogen peroxide. This reaction was further characterized by the colorimetric reaction of 3,3′,5,5′-tetramethylbenzidine. The results showed that our approach allowed for the simple and rapid determination of S. aureus, with a linear range of 2 × 10⁴ to 2 × 10⁷ CFU/mL. Moreover, our method displayed good selectivity, with Bacillus subtilis and Escherichia coli showing negligible responses at the concentration of 2 × 10⁵ CFU/mL. The application of the as-prepared biosensor to analyze S. aureus in real water samples yielded recovery rates ranging from 95% to 112%, with relative standard deviations less than 7%. The method demonstrated good accuracy and specificity, which offers a novel approach for the simple and selective detection of S. aureus.