Nanostructured SERS biosensors for rapid detection and discrimination of Shiga toxins using principal component analysis

Shiga toxin-producing Escherichia coli (STEC) is responsible for severe human infections, including hemolytic uremic syndrome (HUS). Rapid and precise detection of Shiga toxins (Stxs) is crucial for timely diagnosis and treatment. In this study, we developed a nanostructured biosensor based on Surface-Enhanced Raman Spectroscopy (SERS) for the sensitive detection and differentiation of Stx1a, Stx2a, and its cleaved form (Stx2a-cl). The sensor utilizes a plasmonic metasurface featuring a hexagonal array of asymmetric nanocavities (NCs) in a gold film, designed to maximize near-field enhancement and SERS signal amplification. Specific antibodies were immobilized on the sensor surface, enabling selective binding of the target toxins. Principal Component Analysis (PCA) was applied to the acquired SERS spectra, demonstrating clear spectral differentiation among the toxins, including Stx2a and its cleaved form. The PCA results, with an explained variance exceeding 80%, confirm the sensor's high discrimination capability. These findings highlight the potential of the developed biosensor as a potential powerful diagnostic tool for the rapid and accurate detection of STEC infections in clinical and environmental settings.