Quantitative detection of urinary bladder cancer antigen via peptide-immobilized magnetic bead-based SERS probe

Antibody pairing is a difficult step in developing all immune-sandwich assay for antigen detection. Urinary bladder cancer (UBC) antigen is a typical bladder cancer biomarker for the early diagnosis of bladder cancer. Based on peptide-antibody pairing, a surface-enhanced Raman scattering platform for the ultrasensitive detection of UBC is presented. The phage display tech was used to screen and obtain a 12-peptide ligand against UBC (KD = 4.84 × 10^-7 M). Twelve-peptide-conjugate magnetic beads (MNs@12-peptide) and antibody-conjugate silver nanoparticles (AgNPs@Ab) were prepared for SERS measurements. AgNPs@Ab can be linked onto the surface of MNs@12-peptide through ligand/antibody recognition to assess a sandwich-shape complex, which turns on the SERS signal of 4-ABP. Furthermore, the second SERS signal amplification is from the magnetic field-induced spontaneous collection effect. The above design enhances the SERS signal to achieve the limit of detection as 6.25 ng/mL, the clinical threshold of 10 ng/mL. Six clinical urine samples from bladder cancer patients and healthy volunteers were also successfully detected using the dual enhancement SERS measurement. The proposed method provides the future direction of fully automated and ultrasensitive assays.