Label-free, zeptomole cancer biomarker detection by surface-enhanced fluorescence on nanoporous gold disk plasmonic nanoparticles.

We experimentally demonstrate a label-free biosensor for the ERBB2 cancer gene DNA target based on the distance-dependent detection of surface-enhanced fluorescence (SEF) on nanoporous gold disk (NPGD) plasmonic nanoparticles. We achieve detection of 2.4 zeptomole of DNA target on the NPGD substrate with an upper concentration detection limit of 1 nM. Without the use of molecular spacers, the NPGD substrate as an SEF platform was shown to provide higher net fluorescence for visible and NIR fluorophores compared to glass and non-porous gold substrates. The enhanced fluorescence signals in patterned nanoporous gold nanoparticles make NPGD a viable material for further reducing detection limits for biomolecular targets used in clinical assays. With patterned nanoporous gold disk (NPGD) plasmonic nanoparticles, a label-free biosensor that makes use of distance-dependent detection of surface-enhanced fluorescence (SEF) is constructed and tested for zeptomole detection of ERBB2 cancer gene DNA targets.