Plasmonically Enhanced Microarray Immunoassay for High‐Sensitivity Monitoring of Heart Failure

Point‑of‑care testing (POCT) demands diagnostic platforms that pair high analytical sensitivity with compact, low‑cost readout hardware, yet fluorescence‑based immunoassays face a fundamental tradeoff between detector cost and detection performance. Plasmonic nanocavities-such as metal-dielectric-metal nanopatch antennas-offer a powerful signal‑amplification strategy by dramatically enhancing fluorophore emission, enabling sensitive fluorescence detection with inexpensive optics. Here, we introduce a plasmonically enhanced fluorescence microarray immunoassay that integrates nanopatch antennas for high‑sensitivity, low‑cost quantification of key heart‑failure biomarkers, NT‑proBNP, NGAL, and galectin‑3, using a custom smartphone‑based detector. The nanopatch antennas yield up to 485‑fold fluorescence enhancement enabling quantitative and multiplexed detection with limits of detection of 0.055, 3.932, and 0.864 ng/mL, respectively. Analysis of NT‑proBNP-positive human samples shows strong correlation with clinically validated assays, demonstrating the potential of this plasmonically enhanced platform to deliver high‑performance heart‑failure biomarker monitoring at low cost in resource‑limited and point‑of‑care settings.