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In this work, a microfluidic chip using Au@SiO2 array–based highly active SERS substrates was developed for quantitative detection of squamous cell carcinoma antigen (SCCA) and carcinoembryonic antigen (CEA) associated with cervical cancer. The chip consisted of six functional units with pump-free design, enabling parallel detection of multiple samples in an automatic manner without external pumps and improving the portability. Ag nanocubes (AgNCs) were labeled with Raman reporters and coupled with antibodies (labeling) to prepare SERS tags, while the Au nanoparticle–modified SiO2 microsphere (Au@SiO2) array was conjugated with antibodies (coating) to generate the highly SERS-active capturing substrate. In the presence of target biomarkers, they were captured by SERS tags and capturing substrate, resulting in the formation of "sandwich" structures which were trapped in the detection chamber. As the immune reaction proceeded, a large number of "hot spots" were generated by the proximity of the Au@SiO2 array substrate and AgNCs, greatly amplifying SERS signals. With this chip, the limits of detection of the SCCA and CEA levels in human serum were estimated to be as low as 0.45 pg mL−1 and 0.36 pg mL−1, respectively. Furthermore, the good selectivity and reproducibility of this chip were confirmed. Finally, clinical serum samples were analyzed by this chip, and the outcomes were consistent with those of enzyme-linked immunosorbent assay (ELISA). Thus, the proposed microfluidic chip can be potentially applied for the clinical diagnosis of cervical cancer. [ABSTRACT FROM AUTHOR]

Ultrasensitive detection of specific biomarkers in clinical serum is helpful for early diagnosis of cervical cancer. In this paper, a surface-enhanced Raman scattering (SERS)-based immunoassay was developed for the simultaneous determination of squamous cell carcinoma antigen (SCCA) and osteopontin (OPN) in cervical cancer serum. Au-Ag nanoshuttles (Au-AgNSs) as SERS tags and hydrophobic filter paper-based Au nanoflowers (AuNFs) as capture substrate were constructed into a sandwich structure which served as an ultrasensitive SERS-based immunoassay platform. Finite difference time domain simulation confirmed that the electromagnetic field coupled between the AuNFs had a prominent SERS signal enhancement effect, which improved the detection sensitivity. SERS mapping showed that hexadecenyl succinic anhydride hydrophobic treatment could prevent the analyte from being quickly absorbed by the filter paper and increase the retention time to be more evenly distributed on the filter paper substrate. The immunoassay platform was verified to have good selectivity and reproducibility. With this method, the detection limits of SCCA and OPN in human serum were as low as 8.628 pg/mL and 4.388 pg/mL, respectively. Finally, in order to verify the feasibility of its clinical application, the serum samples of healthy subjects; cervical intraepithelial neoplasia I (CINI), CINII, and CINIII; and cervical cancer patients were analyzed, and the reliability of the results was confirmed by enzyme-linked immunosorbent assay experiments. The constructed SERS-based immunoassay platform could be used as a clinical tool for early screening of cancers in the future. [ABSTRACT FROM AUTHOR]