Direct and Glow Chemiluminescence of Dual-Stabilizer-Capped Au Nanocrystals for Automatic Immunoassays

The commercialized immunoassay of glow-type chemiluminescence (CL) is always performed in an enzyme-assisted and indirect CL way, with molecular luminophores as tags. Herein, dual-stabilizer-capped Au nanoclusters (NCs) are proposed as nanoparticulate glow-CL luminophores and perform automatic immunoassays on commercialized in vitro diagnosis (IVD) instruments in a direct and enzyme-free CL way. The thiosalicylic acid (TSA) and bovine serum albumin (BSA) stabilized AuNCs (TSA/BSA-AuNCs) are water-soluble, biocompatible, and n-type CL luminophores, which can give off dark-red and glow-type CL with the coexistence of both hydrazine hydrate (N₂H₄·H₂O) and hydrogen peroxide (H₂O₂). The glow-CL of TSA/BSA-AuNCs is generated in a combined route of bandgap-engineered CL (∼711 nm) and surface-defect-engineered CL (∼860 nm), and its total emission is strong enough to linearly determine procalcitonin (PCT) from 0.1 to 5000 pg/mL with a limit of detection of 0.05 pg/mL (S/N = 3), which is superior to the limit of detection for all of the commercialized CL immunoassays. Promisingly, TSA/BSA-AuNCs can be safely stored over 5 months and safely labeled to proteins without permanent precipitation and damage, which are strongly anticipated for the design of CL reagent kits with nanoparticles as tags and might initiate the commercialized application of NCs CL.