A sandwich SERS immunoassay platform based on a single-layer Au-Ag nanobox array substrate for simultaneous detection of SCCA and survivin in serum of patients with cervical lesions.

The evaluation of tumor biomarkers in blood specimens is vital for patients with cervical lesions. Herein, an ultrasensitive surface enhanced Raman scattering (SERS) platform was proposed for simultaneous detection of cervical-lesion-related serum biomarkers. Raman reporter labeled Au-Ag nanoshells (Au-AgNSs) acted as SERS tags and an Au-Ag nanobox (Au-AgNB) array substrate prepared by the oil-water interface self-assembly method was used as a capture substrate. This single-layer Au-AgNB array substrate was proved to have exceptional uniformity by atomic force microscopy and SERS mapping. Numerous "hot spots" and specific adsorption surfaces offered by the Au-AgNB array substrate were confirmed by the finite difference time domain method, which could generate a SERS signal in electromagnetic enhancement. Binding of antigens between antibodies on Au-AgNSs and the Au-AgNB array substrate led to the formation of a sandwich-structure by the two metal nanostructures. Consequently, an ultralow detection limit of 6 pg mL for squamous cell carcinoma antigen (SCCA) and 5 pg mL for survivin in a wide linear logarithmic range of 10 pg mL to 10 μg mL was acquired. High selectivity and reproducibility with relative standard deviations of 7.701% and 6.943% were detected. Furthermore, the simultaneous detection of the two biomarkers in practical specimens was conducted, and the results were consistent with those of the enzyme-linked immunosorbent assay. This platform exhibited good robustness in the rapid and sensitive detection of SCCA and survivin, which could be a promising tool in early clinical diagnosis for different grades of cervical lesions.