Optical Glass Microsphere Enabled Rapid Single‐Molecular Fluoroimmunoassay

Abstract Determination of low‐abundance proteins in body liquid is the significant strategy for the early diagnosis of diseases and the discovery of signal paths in pathobiology. Here, the limit of detection of 113 aM for model human IgA is successfully obtained by the fluoroimmunoassay developed on an optical soda lime glass microsphere in micrometers that is illumed by the microsphere amplified fluorescence (MAF), which can be identified to the most sensitive immunoassay so far. In this case, the fluorescence signal of fluoroimmunoassay can be physically amplified by MAF while the large reacting area will be supplied by the glass microsphere to complete the fluoroimmunoassay. Therefore, the assay time of the fluoroimmunoassay can be shortened to 12 min via the optical glass microsphere‐enabled ultrasensitive fluoroimmunoassay at the same time. The developed fluoroimmunoassay indicates a possibility to perform the ultrasensitive immunoassay on the optical glass microsphere in 10 min and more, which may greatly facilitate the development of the ultrasensitive immunoassay for the urgent measurements and promote the development of portable fluoroimmunoassay.