High-performance SERS biosensor based on in-situ reduction of silver nanoparticles in an ultra-filtration centrifuge device for label-free detection of colon cancer in serum

Label-free surface-enhanced Raman scattering (SERS) technology is used to screen for colon cancer for its rapid identification, high specificity and non-invasiveness. Here, we have developed a high-performance SERS biosensor that has combined concentration, separation and detection for effective screening of colon cancer. This SERS biosensor is equipped with a centrifuge tube and a filter that consists of two ultrafiltration membranes (UFMs). First, silver nanoparticles (Ag NPs) are uniformly reduced in-situ on the UFM using a controlled "silver mirror reaction", then the filter and centrifuge tube are assembled into an ultrafiltration centrifuge tube containing Ag NPs (Ag NPs/UFT biosensor). And finally, the Ag NPs/UFT biosensor is applied to concentrate and separate colon cancer serum. The biosensor reduces signal fluctuations in the detection of liquid phase substrates (Ag NPs colloids), which are prone to aggregation and instability, more importantly minimizes the interference of large amounts of small molecule proteins and also concentrates and retains molecular weight proteins of high diagnostic value. Furthermore, we employed SERS spectroscopy by portable Raman, combined with principal component analysis-linear discriminant analysis (PCA-LDA) models, to further assess the screening diagnosis of colon cancer. As a proof of concept, we achieved 100% specificity and 87.5% accuracy with our sensors. This study will contribute to the field of non-invasive, rapid and practical screening for colon cancer together with the ultrafiltration system.