Development of Ultrasensitive New Sensor Based on Functionalized Triangular Gold Nanosheets Layers for SARS-CoV-2 Detection

An ultrasensitive new sensor based on functionalized triangular gold nanosheet layers for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection was proposed. For this purpose, 3-mercaptopropyltrimethoxysilane (MPTMS) was used to fix triangular gold nanosheets (AuTNPs) on the surface of optical fiber. AuTNPs have a unique tip structure and excellent localized surface plasmon resonance (LSPR) effect, which can improve the sensitivity of the sensor. Then, the monoclonal antibodies (mAbs) are fixed to the surface of the AuTNPs by covalent bonds to make biosensors. The combination of AuTNPs and mAb on the surface of optical fiber through a covalent bond was verified by ultraviolet (UV)–vis and infrared characterization. The mAb attached to the surface of AuTNPs binds to the SARS-CoV-2 antigen through physical adsorption, and the effective refractive index of the fiber surface changes, resulting in the peak shift. At the same time, it is proved that the LSPR shift is not caused by the refractive index to be measured. The Au-mAb biosensor displays a linear response in the SARS-CoV-2 spike antigen concentration of 1.56–312 ng/mL and the sensitivity is 0.035 nm/(ng/mL). The biosensor has a short response time (10 min), good stability, and can be reused. The Au-mAb biosensor has broad application prospects in the medical diagnostic field.