{Reference Type}: Journal Article
{Title}: Detection of estradiol with a digital immunoassay using an anti-immunocomplex antibody and single-molecule observation of gold nanoparticles.
{Author}: Muto Y;Hirao G;Zako T;
{Journal}: Anal Sci
{Volume}: 40
{Issue}: 6
{Year}: 2024 Jun 29
{Factor}: 1.967
{DOI}: 10.1007/s44211-024-00518-6
{Abstract}: Gold nanoparticles (AuNPs) have been widely applied to molecular sensors due to their optical properties. We previously reported a molecular detection by observing the scattered light of AuNPs at a single nanoparticle level using dark field microscopy (DFM). Recently, a molecular detection method using digital immunoassay has been reported, taking advantage of the characteristics of DFM. However, the digital immunoassays reported so far have been performed by a conventional sandwich immunoassay, which is difficult to apply to the detection of small molecules. In this study, with the aim of small molecule detection, we developed a digital immunoassay method using an anti-immunocomplex antibody that specifically recognizes immunocomplexes of small molecules with antibodies. The number of AuNPs modified with anti-immunocomplex antibody bound to immunocomplex of estradiol and anti-estradiol antibody was counted at a single nanoparticle level using DFM. We demonstrated for the first time that estradiol molecule can be detected by digital immunoassay using DFM and an anti-immunocomplex antibody with a detection sensitivity of 1 pg/mL.