Gold/vertical-graphene-based dual-channel electrochemical immunosensor for point-of-care testing of tetanus toxin in blood.

The tetanus spasm toxin has been identified as the main pathogenic substance responsible for tetanus, and its trace detection is expected to provide reliable diagnostic biomarkers. In this study, we developed the first electrochemical tetanus-toxin immunosensor capable of rapid on-site detection and real-time analysis. This electrochemical sensor was developed by combining a mutually verifiable dual-channel (oxidation and reduction channels) strategy and a gold-nanoparticle-embedded vertical graphene (Au-VG) microelectrode with a high antibody-loading capacity, which led to a sensor with superior detection reliability and performance stability. Integrating immune responses, the redox reactions of probes, and in-house-developed real-time-analysis software enabled tetanus toxin to be specifically detected based on current response. The sensor exhibited a wide linear detection range (0.1 fg mL-1 to 100 ng mL-1) and a low limits of detection of 0.024 and 0.021 fg mL-1 for the oxidation and reduction channels, respectively. Furthermore, a needle sensor and test-box system that incorporated flexible Au-VG microelectrodes were successfully validated for the quantitative detection of tetanus toxin in clinical sera and whole blood samples. This study developed a novel immunosensor and a rapid on-site detection strategy with significant applications potential for the early screening and diagnosis of tetanus.