A flexible antenna immunosensor with AuPt-graphene film for wireless detection of tetanus toxin

The danger of tetanus originates from the tetanus toxin (TT) produced by Clostridium tetani. This toxin primarily attacks the central nervous system, leading to severe multi-system damage and even posing a threat to life. It is highly potent, with a lethal dose of merely 2.5 ng/kg in humans. However, traditional diagnosis relies on clinical manifestations and lacks quantitative indicators, making it difficult to conduct rapid and on-site diagnosis. Therefore, it is necessary to study unlabeled, real-time, and wireless detection modes.

Hence, this paper introduces a compact, flexible antenna-based immunosensor for TT detection, designed to overcome the aforementioned technical challenges. Operating at 2.45 GHz within the Industrial Scientific Medical (ISM) band, the proposed antenna immunosensor features a unique structure, which grants it a compact dimension of 14 × 14 × 3 mm³ and achieves a wireless sensing range of up to 15 m. A graphene film modified by AuPt nanoparticles is deposited onto the radiation patch as a sensitive layer. A change in TT concentration leads to a shift in the resonant frequency of the antenna immunosensor, caused by the specific antibody-antigen binding, thereby enabling the quantitative detection of TT. The antenna immunosensor exhibits a sensitivity of 2.755 MHz/lg(fg/mL), with an antigen concentration range from 10^-1 to 10⁸ fg/mL. A comprehensive performance analysis of the immunosensor reveals that it demonstrates remarkable regenerability, reproducibility, long-term stability, and specificity. In practical application, the corresponding TT concentration were accurately detected from centrifuged blood samples, with the results being verified as reliable. This demonstrates that the use of inactivated tetanus toxoid as a substitute for the native toxin can yield valid and convincing detection outcomes.

This study combines microwave sensing technology with highly specific biometric antibodies, creating a new way of detecting tetanus toxin. The antenna immunosensor utilizes the shifts in resonant frequency before and after toxin binding to achieve label free, real-time, and wireless detection. Furthermore, this study provides a promising alternative for the highly integrated, miniaturized sensing platforms capable of continuous monitoring.