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The use of plasmonic metasurface for sensing has great potential on label-free detection of human tumor markers, which could benefit clinical examination. In this work, we adopt nanoimprint and plasma etching to optimize the nanofabrication for low-cost flexible plasmonic metasurface sensors with gold nanobump arrays, which enable facile surface bio-functionality, high sensitivity and simple optical measurement in the visible range. A high bulk refractive index sensitivity of 454.4 nm/RIU is achieved for the prototype plasmonic metasurface sensors at the wavelengths from 620 nm to 720 nm. The rapid quantitative tumor marker sensing of carcinoembryonic antigen in human serum samples from less than 10 ng/mL to more than 87 ng/mL is achieved, which demonstrates good agreement with the conventional chemiluminescence immunoassay system and sufficiently covers the threshold tumor marker concentration of 20 ng/mL for early cancer prediction. Our method is capable of low-cost high-throughput manufacturing for flexible lightweight plasmonic metasurface sensors, which will facilitate wide applications on portable biomedical sensing devices for future point-of-care diagnosis and mobile healthcare. • Large-scale metasurfaces on lightweight flexible substrates for portable biosensing. • Cost-effective fabrication for mass production by soft nanoimprint lithography. • The entire gold encapsulation benefits the process of antibody functionalization. • Low-cost and compact reflection-type sensing system in the visible range. • High sensitivity for detecting tumor markers, which is competitive with the conventional immunoassay system. [ABSTRACT FROM AUTHOR]

Prostate-specific antigen (PSA) test is widely used to diagnose early prostate cancer (PCa). Its low sensitivity, especially in the gray zone, usually incurs overtreatment or missed diagnosis. As an emerging tumor marker, exosomes have attracted great interest in non-invasive diagnosis of PCa. However, the quick direct detection of exosomes in serum is still a big challenge for convenient screening of early PCa due to their high-degree heterogeneity and complexity. Here we develop the label-free biosensors based on wafer-scale plasmonic metasurfaces, and establish a flexible spectral methodology of exosomes profiling, which facilitates their identification and quantification in serum. We combine the metasurfaces functionalized by anti-PSA and anti-CD63, respectively, and build a portable immunoassay system to detect serum PSA and exosomes simultaneously within 20 min. Our scheme can discriminate early PCa from benign prostatic hyperplasia with a diagnostic sensitivity of 92.3%, which is much higher that of 58.3% for conventional PSA tests. The receiver operating characteristic analysis in clinical trials demonstrates significant PCa distinguishing capability with an area under the curve up to 99.4%. Our work provides a rapid and powerful approach for precise diagnosis of early PCa, and will inspire more exosomes metasensing studies for other early cancer screening. [ABSTRACT FROM AUTHOR]

Plasmonic metasurface biosensors have great potential on label-free high-throughput clinical detection of human tumor markers. In the past decades, nanopillar and nanohole metasurfaces have become the common choices for plasmonic biosensing, because they typically enable universal simple large-area nanopatterns via a low-cost reproducible fabrication manner. The two kinds of metasurfaces have the complementary shapes and are used to be assumed as the same type of two-dimensional plasmonic nanograting for biosensing. Up to date, there is still a lack of comparison study on their biosensing performance, which is critical to guide their better applications on tumor marker detection. In this study, we compare the bulk/surface refractive index and sensitivity of plasmonic nanopillar (PNP) and plasmonic nanohole (PNH) metasurfaces in order to evaluate their biosensing capabilities. The sensing physics about their space near-field utilization is systematically revealed. The PNH metasurface demonstrates a higher biomolecule sensitivity versus the complementary PNP metasurface, and its limit of detection for bovine serum albumin reaches ∼0.078 ng/mL, which implies a greater potential of detecting cancer biomarkers. We further adopt the PNH metasurfaces for immunoassay of three typical tumor markers by testing clinical human serum samples. The results imply that the immunodetection of alpha-fetoprotein has the most optimal sensing efficiency with the lowest detection concentration (<5 IU/mL), which is much lower than its clinical diagnosis threshold of ∼16.5 IU/mL for medical examination. Our work has not only illuminated the distinct biosensing properties of complementary metasurfaces, but also provided a promising way to boost plasmonic biosensing for point-of-care testing. • The study of complementary plasmonic metasurfaces is performed to guide their clinical detection of multiplex tumor markers. • The plasmonic nanohole metasurface demonstrates a higher sensitivity, whose limit of detection for BSA reaches ~0.078 ng/mL. • The immunosensing of AFP indicates the most optimal detection capability much lower than the clinical diagnosis threshold. [ABSTRACT FROM AUTHOR]