Self-reporting plasmonic nanoflowers enable magnetically enriched SERS immunoassay for ultrasensitive prostate cancer biomarker detection.

Nanoengineering of plasmonic/magnetic nanocrystals plays a pivotal role in advancing biomolecular detection, offering emerging strategies for cancer diagnostics and therapeutic monitoring. Early and precise detection of cancer biomarkers is critical for timely intervention. Yet conventional immunoassays are often hindered by limited sensitivity, nonspecific binding, and inefficient target enrichment, reducing their clinical reliability. Herein, we develop a self-reporting bimetallic plasmonic nanoflowers-based SERS immunoassay that integrates magnetic enrichment and plasmonic field amplification for ultrasensitive detection of total prostate-specific antigen (t-PSA). The bimetallic Ag-Au nanoflowers were synthesized through a novel nanocrystal engineering approach that integrates the structural stability of gold with the superior plasmonic enhancement of silver, while intrinsically incorporating self-reporting SERS labels on the surface. Serving as intrinsic Raman probes, these nanoflowers eliminate the need for external labeling, thereby simplifying the detection process and enhancing reproducibility. Simultaneously, antibody-functionalized magnetic nanoparticles facilitate efficient target separation and enrichment, significantly improving detection sensitivity. This synergistic strategy achieves an ultra-low detection limit of 100 fg mL and enables precise quantification within the diagnostic gray zone (4.0-10.0 ng mL), a critical range for early prostate cancer screening. Furthermore, the reliability of the SERS immunoassay was further confirmed by testing t-PSA-spiked serum samples, showing consistent analytical performance and excellent agreement with conventional ELISA measurements. The combination of self-reporting plasmonic nanostructures, magnetic-assisted biomarker capture, and hotspot-driven SERS amplification offers promising and highly sensitive biosensing nanoprobes for early prostate cancer diagnosis.