Sensitive detection of adipokines for early diagnosis of type 2 diabetes using enzyme-linked antibody-aptamer sandwich (ELAAS) assays

We developed an enzyme-linked antibody-ssDNA aptamer sandwich (ELAAS) method to detect three adipokines for diagnosing type 2 diabetes. For this application, three different aptamers for retinol-binding protein-4 (RBP4), visceral adipose tissue-derived serpin (Vaspin), and nicotinamide phosphoribosyltransferase (Nampt/visfatin) were used as capturing probes, and enzyme-linked polyclonal antibodies were used for signal generation. The sensitivities of this method for all three proteins were enhanced by at least 20-fold to up to 68-fold higher than that of the surface plasmon resonance (SPR) system, which only uses aptamers as capturing probes. In addition, this assay method exhibited equal sensitivity in the detection of each adipokine spiked in diluted human serum. In particular, the detection limit for RBP4 was similar to that obtained by western blotting, as reported previously. The simplicity, reproducibility, and high sensitivity of the ELAAS method could allow it to be extensively utilized in field.