Multiplexed Detection of Cancer Protein Biomarkers via Surface‐Enhanced Raman Scattering Immunoassays on Natural Diatomite Strips

In this study, we used flexible and inexpensive diatomite/AgNPs strips and Layer‐by‐Layer (LbL) assembly to develop sandwich assays for the detection of cancer biomarkers of interest via Surface‐enhanced Raman scattering (SERS). The modified SERS active strips were used to capture antigens of interest, incubate Raman probes, and generate SERS maps based on specific Raman peaks of the Raman probes. Simultaneous detection and quantification of multiple biomarkers, including HER2, CA15‐3, CA27‐29, PSA, and MUC4, were demonstrated by the immobilization of specific antibodies and the use of uniquely labeled Raman probes. Spatially resolved and co‐immobilized multiplexing strategies were developed and successfully validated, showing high specificity and sensitivity with negligible background interference from serum components. The flexible and cost‐effective nature of the diatomite/AgNPs substrate, combined with its strong SERS enhancement, offers significant advantages over traditional immunoassay techniques.