Fluorescent gold nanoparticle (GNP) is an easily synthesized and biocompatible optical platform for sensing and imaging with tunable near-infrared (NIR) emission. However, the relatively low fluorescence (FL) quantum yield limits the further improvement of sensitivity and application. Here, we find that, on plasmonic substrates, the FL intensity of protein-directed synthesized GNPs can be enhanced significantly (approx20-fold). Moreover, protein analytes can interact with GNPs and influence the enhanced fluorescence process so that we can obtain distinct FL image patterns. Then, using the array-based sensing strategy, protein discrimination can be achieved. In our present experiment, five GNPs were used as sensing elements and 10 kinds of proteins at three concentrations (0.2, 0.5, and 1 (mu)M) were successfully identified. This array-based sensing strategy using enhanced-fluorescence from GNPs is highly sensitive and differentiable, expanding the application field of GNPs.
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