Abstract
Enzyme-based assays have been widely applied in clinical diagnosis for decades. However, the intrinsic limitations of enzymes, such as low operation stability, mediocre sensitivity, and high cost in production and purification, heavily constrain their detection application. Here, an enzyme-free assay is reported that relies on the strong chelating capability of ethylenediamine tetraacetic acid disodium salt (EDTA•2Na, the chelator) for Au(3+) ions, in which the cheap EDTA•2Na labeled by targeting moieties can selectively regulate the growth of plasmonic gold nanoparticles (AuNPs) at the target site subjecting to the concentration of analyte in samples. Independent of ambient temperature and unstable H(2)O(2), EDTA•2Na perform superregulation in AuNPs plasmonic signal generation with distinct tonality and outstanding reliability. Upon integrating with silica nanoparticles as the signal amplifying platform, EDTA•2Na-regulated bioassay can lead to detection-sensitivity enhancements exceeding three orders of magnitude in protein detection, compared with the gold-standard assay. The limit of detection of the HBsAg and alpha fetoprotein (AFP) pushes down to 2.6 × 10(-15) and 2.5 × 10(-19) g mL(-1), respectively. EDTA•2Na-regulated bioassay is also challenged in the clinical serum sample detection and a good consistency is found with the chemiluminescence immunoassay method in clinics.