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 prostatespecific 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.
We developed a new plasmonic nanostripe microcone array
(PNMA)
substrate-integrated microfluidic chip for the simultaneous surface-enhanced
Raman scattering (SERS)-based immunoassay of the creatine kinase MB
isoenzyme (CK-MB) and cardiac troponin (cTnI) cardiac markers. The
conventional immunoassay usually employs a microtiter plate as the
solid capture plate to form the immunocomplexes. However, the two-dimensional
(2D) surface of the microtiter plate limits the capture efficiency
of the target antigens due to the steric hindrance effect. To address
this issue, a gold film-coated microcone array with nanostripes was
developed that can provide a large surface area for capture antibody
conjugation and serve as a SERS-active substrate. This unique nano–microhierarchical
structure showed an excellent light trapping effect and induced surface
plasmon resonance to further enhance the Raman signals of the SERS
nanoprobes. It significantly improved the sensitivity and applicability
of SERS-based immunoassay on the microfluidic chip. With this integrated
microfluidic chip, we successfully performed the simultaneous detection
of CK-MB and cTnI, and the detection limit can reach 0.01 ng mL–1. It is believed that the PNMA substrate-integrated
microfluidic chip would play a critical role in the rapid and sensitive
diagnostics of cardiac diseases.
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