Enzyme-induced in situ generation of polymer carbon dots for fluorescence immunoassay

Current fluorescence immunoassays generally employ synthetic fluorophore-labeled antibody and complicated fluorescence regulation process. We are dedicated to developing a conceptual fluorescent enzyme-linked immunosorbent assay (ELISA) based on enzyme-induced in situ fluorogenic reaction to resolve such issues. For the construction of novel fluorescent ELISA, discovering a moderate but rapid fluorogenic reaction and choosing a preferable substrate are both necessary and significant. In this study, we have demonstrated that 4-aminophenol (AP) can react with ethylenediamine at 37 degrees C for 2 h to produce strong green fluorescent polymer carbon dots (PCDs) for the first time. Inspired by this simple reaction and alkaline phosphatase (ALP)-triggered specific hydrolysis of 4-aminophenyl phosphate (APP) into AP, we have developed a strategy for detecting ALP activity via in situ formation of fluorescent PCDs. Furthermore, employing conventional ELISA platform and commercial antibodies to cardiac troponin I (cTnI), we construct a simple and convenient ALP-based fluorescent ELISA for quantitatively evaluating the cTnI level in human serum. Such original ELISA via in situ generation of fluorescent nanomaterials from scratch has great potential for the early diagnosis of disease markers in the near future.