Supersensitive single-particle plasmonic scattering-based cancer antigen 125 nanoimmunosensor by enhanced dark-field microscopy with dual-detection mode

Abstract

A supersensitive nanoimmunosensor of cancer antigen 125 (CA125), which is a stage marker of several types of cancers, was developed based on characterization of single-particle plasmonic scattering by wavelength-dependent enhanced dark-field microscopy with dual-detection mode (EDFM-DM). Considering the optical properties of gold and silver nanoparticles (AuNPs/AgNPs), 40-nm AgNP was selected as an optimal fluorescence-free probe. CA125 was analyzed using the wavelength-dependent plasmonic scattering intensity of 40-nm AgNP-labeled CA125 immunoreacted on gold nanodots under the dual-detection mode. A color digital camera and an electron multiplying charge-coupled device camera were used for qualitative and quantitative analysis, respectively, based on the dark-field scattering images. Under optimal conditions, the developed immunosensor exhibited a lower detection limit of 4μU/mL (S/N=3) with a wide dynamic detection range of 4μU/mL-80U/mL (R=0.9935), which was a 100–375,000-fold lower detection limit with a 100–100,000-fold wider dynamic range than previous methods. In addition, recovery was greater than 98% with the spiking of standard CA125 in human serum samples. This method may be an excellent nanoimmunoassay platform for supersensitive detection at a wide dynamic detection range, supporting the earliest-stage detection of various disease-related protein molecules at the single-molecule level.