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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.

The simultaneous detection of multiple biomarkers plays an important role in the accurate diagnosis of cancer. In this study, we developed a novel, surface-enhanced Raman scattering (SERS)-based microfluidic device for the simultaneous detection of free prostate-specific antigen (f-PSA) and total PSA (t-PSA) markers. A fully automatic droplet-based microfluidic platform for the rapid and sensitive detection of f-PSA and t-PSA was designed. Magnetic immunocomplexes were aligned on one side of the channel using a permanent magnet embedded in the microfluidic device, and parent microdroplets containing magnetic immunocomplexes and supernatant solutions were split into two smaller daughter droplets at the Y-shaped junction of the channel. Then, Raman signals of sequential droplets including supernatant solutions were measured for the quantitative analysis of the PSA markers. Two parallel microfluidic channels were designed and fabricated for the simultaneous detection of f-PSA and t-PSA. Our results showed a good linear response for both PSA markers in the range from 0.05 to 100 ng mL -1 . The limits of detection were estimated to be below 0.1 ng mL -1 for both the f-PSA and t-PSA. This SERS-based assay in a microfluidic channel was completed in 10 min without any manual incubation and washing steps. Our method is a very promising clinical tool for PSA-based screening test of prostate cancer., (Copyright © 2018 Elsevier B.V. All rights reserved.)

We report a novel wash-free magnetic immunoassay technique for prostate-specific antigen (PSA) that uses a surface-enhanced Raman scattering (SERS)-based microdroplet sensor. The magnetic bar embedded in a droplet-based microfluidic system segregates the free and bound SERS tags by splitting the droplets into two smaller parts. The presence of PSA targets leads more SERS tags to immunocomplex in one droplet so that fewer SERS tags remain in another supernatant solution droplet. Thus, SERS signal measurement enables the quantitative evaluation of PSA markers. This approach can provide a rapid and sensitive assay that is applicable for PSA cancer markers in serum without any washing. Specifically, SERS signals were measured at 174 droplets per minute and averaged for quantitative evaluation of PSA. The limit of detection (LOD) determined by our SERS-based microdroplet sensor was estimated to be below 0.1 ng mL(-1), which is significantly below the clinical cut-off value for the diagnosis of prostate cancer. In addition, because the entire assay can be carried out automatically, only a minimal amount of sample is needed. Accordingly, the approach is expected to be useful as a potential clinical tool for the early diagnosis of prostate cancer.

We reported a novel multifunctional nanocone array as solid immunoassay plate and surface-enhanced Raman scattering (SERS) substrate for the simultaneous immunoassay of prostate-specific antigen (PSA) and thrombin based on microfluidic chip. In traditional immunoassays, microtiter plates are often used as solid capture plates to form immunocomplexes. However, the two-dimensional surface of the microtiter plate limits the efficiency of target antigen capture due to its steric inhibition. To solve this problem, a nanocone array covered with deposited gold film was successfully fabricated on glass slides that could be directly sealed with PDMS microfluidic chip. As a SERS active substrate, it can also provide a large surface area for capture aptamer conjugation to form a "sandwich" immunocomplex. On the strength of this integrated microfluidic chip, we could detect PSA and thrombin simultaneously with the detection limits of 0.01 ng mL−1 and 0.01 nM. Compared to previous reports, this detection strategy demonstrated the rapid and automatic performance with comparable detection limits. It is believed that the proposed microfluidic sensor has great potential for the early diagnosis of prostate cancer. • A novel SERS-based microfluidic sensor was proposed to achieve the detection of dual prostate cancer markers. • The unique nanocone array with nanoscale wrinkles acted as the solid capture plate and SERS substrate for immunoassay. • The SERS substrate can further enhance the Raman signal of SERS nanotags by the link of "sandwich" immunocomplexes. [ABSTRACT FROM AUTHOR]