SERS-Based Pump-Free Microfluidic Chip for Highly Sensitive Immunoassay of Prostate-Specific Antigen Biomarkers

Highly sensitive analysis of cancer biomarkers demonstrates an important impact in early diagnosis and therapies of cancer. A novel surface-enhanced Raman scattering (SERS) based immunoassay using microfluidic technique was reported for rapid analysis of prostate-specific antigen (PSA) biomarker. It is a useful screening test to discriminate prostate cancer and other diseases related to prostate. A "sandwich" immunoassay based on SERS nanotags, PSA biomarkers, and magnetic beads was applied on a pump-free microfluidic sensor. Magnetic immunocomplexes are isolated and trapped at the detection chamber by a permanent magnet integrated into the chip. The PBS buffer washed magnetic immunocomplexes and brought the free gold nanoparticles to the downsteam channel for waste. Our results show a good linear response in the range from 0.01 to 100 ng mL^-1. The limit of detection of the PSA level is estimated to be below 0.01 ng mL^-1 using this chip. This detection level of PSA biomarker in human serum can be accomplished in 5 min without manual incubation and a heavy syringe pump. To the best of our knowledge, this is the first SERS-based immunoassay which applied a pump-free microfluidic chip as a detection platform. We believe that the proposed method reveals a valuable potential tool for the diagnosis of prostate cancer.