Small-Volume Plasmonic Microwell Array with 3D Hierarchical Nanomaterials for Plasmon-Enhanced Fluorescence Immunoassay

Developing a small-volume bioassay using microliter-scale biofluids is crucial for achieving a rapid, sensitive, and high-throughput screening and medical diagnosis. Herein, a new plasmonic microwell array (PMA) containing 3D hierarchical nanomaterials for multiplexed bioassays is presented. The microwell array is formed by performing a sequential bottom-up fabrication involving dispensing UV-curable photopolymers and plasmonic Ag nanowires (NWs) on a flat substrate. The plasmonic Ag NWs are developed into a multilayer stack of Ag@Au core-shell NWs having surfaces densely decorated with Au nanoparticles. This multi-stacked hybrid plasmonic nanostructure provided 3D multiscale hotspots and large effective surfaces for molecular binding sites. Highly improved sensitivities are demonstrated for a plasmon-enhanced fluorescence-based immunoassay of cardiac troponin I (cTnI), a diagnostic biomarker for acute myocardial infarction, using a small volume of 5 mu L. The limit of detection is determined to be 2.02pgmL(-1) for cTnI, representing a 30-fold greater sensitivity than the clinical cut-off value. Furthermore, 3D PMA chips exhibit a highly uniform fluorescence intensity with a coefficient of variation of 3.4%. The 3D PMA provides a sensitive and reliable detection in a high-throughput manner for point-of-care bioanalysis.