Absorbance amplification using chromophore-nanoplasmon coupling for ultrasensitive protein quantification.

A plasmonic nanoscale Lycurgus cup array (nanoLCA), via near-field interaction with chromophores in commercial colorimetric biochemical assays, can drastically enhance assay sensitivity by over 2 orders of magnitude. A 96-microwell plate modified by placing the plasmonic nanoLCA on the well-bottom was used with the commercial Bradford protein quantification assay. Plasmons on the nanoLCA serve as an energy donor to matched resonance chromophores, and the near-field plasmonic energy coupling effect results in an increase in absorbance value at the plasmonic resonance wavelength. Even with a 5.1-fold reduced sample volume, a limit of detection enhancement factor of 200 is accomplished using the nanoLCA compared to using the conventional Bradford assay without plasmon aid. The nanoLCA-microplate sensing platform is readily scalable to 384- or 1536-microwell plates, which further reduces the sensing volume and boosts detection throughput with the enhanced sensitivity.