Ultrasensitive detection of SARS-CoV-2 (2019-nCoV) S Protein RBD based on optical fiber plasmonic sensor

Surface plasmon resonance (SPR) technology, boasting prominent advantages including anti-electromagnetic interference, high sensitivity, rapid response, label-free detection, and minimal sample consumption, holds broad application prospects in life sciences, clinical diagnostics, drug screening, and other related fields. However, current optical fiber biochemical sensors are generally plagued by poor probe practicality and stability, low refractive index sensitivity, and inadequate detection capability for ultra-low concentration biomolecules in clinical settings. In this study, we developed a low-cost, high-sensitivity optical fiber SPR biosensor for SARS-CoV-2 antigen detection in the standard sample, employing gold@silver‑platinum (Au@AgPt) core-shell nanospheres as the sensing enhancement module. Au@AgPt core-shell nanospheres possess unique localized surface plasmon resonance (LSPR) properties. When incident light interacts with the nanomaterial surface, it induces a localized electric field enhancement effect. This surface enhancement effect significantly amplifies the optical signal intensity, thereby effectively improving the sensor's detection sensitivity toward the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein. This sensing platform achieves fg/mL-level detection sensitivity, excellent linearity, and rapid response performance, offering new technical support for expanding the application of optical fiber sensors in the quantitative detection of ultra-low concentration disease markers.