Aggregation-induced emission luminogen based ELISA for highly sensitive protein detection

Enzyme-linked immunosorbent assay (ELISA), as the most commonly used immunological detection technique, has been widely used in the clinical diagnosis of disease marker proteins. The key of the traditional ELISA is the probe, the horseradish peroxidase (HRP), which influences the sensitivity. However, the application of tradi-tional ELISA in the biomedical field is limited due to low sensitivity. In this work, an aggregation-induced emission luminogen (AIEgen) was designed as a replacement of HRP in ELISA. It was synthesized by function-alizing a tetraphenylethylene (TPE) fluorogen with phosphorylated peptides (TPE-phenylalanine-phenylalanine-tyrosine(H2PO3)-OH, TPE-FFYp). The TPE-FFYp fluoresced weakly in an aqueous solution. Upon addition of the target protein, the phosphate group was hydrolyzed by alkaline phosphatase (ALP) on the immune complex while forming highly emissive AIE aggregates. Utilizing alpha-fetoprotein (AFP) as the model target, this pro-posed method has a detection limit as low as 0.78 ng/mL. Besides, the detection of AFP with TPE-FFYp was not only uninterrupted by other proteins, but also performed well in human serum. More importantly, it could be used to detect other targets by changing the corresponding antibodies, which further extended the application of AIEgen in bioassays.