A DNA dendrimer amplified electrochemical immunosensing method for highly sensitive detection of prostate specific antigen

Highlights: • A DNA dendrimer is designed for loading of a large amount of electroactive molecule to amplify the immunosensing signal. • The DNA dendrimer can be conveniently assembled with a couple of complementary Y-shaped DNAs. • The proposed immunosensing method shows a wide concentration range and a limit of detection down to sub-pg·mL⁻¹. • The good selectivity and accuracy for serum sample analysis demonstrate the potential application of the DNA dendrimer. This work designed a DNA dendrimer for the loading of signal molecule and the construction of amplified electrochemical immunosensing method. The DNA dendrimer was self-assembled by the hybridization of one couple of complementary oligonucleotides (DNA and cDNA) that were covalently conjugated to three arms of a Y-shaped cross-linker, tris(2-maleimidoethyl)amine (TMEA) respectively. The immunosensor was prepared by coating chitosan on glassy carbon electrode to covalently immobilize the capture antibody with glutaraldehyde as a linker. After the target protein was captured on the immunosensor, cDNA-labeled secondary antibody was bound on the surface via a sandwiched immunoreaction to introduce the DNA dendrimer onto immunosensor for loading abundant methylene blue as signal molecule, which amplified greatly the amperometric signal for immunoassay. Using prostate specific antigen (PSA) as a model analyte, this proposed method showed a wide linear range from 1 pg mL⁻¹ to 10 ng mL⁻¹ along with a limit of detection down to 0.26 pg mL⁻¹. The designed strategy avoided complex synthesis of signal tags, and possessed excellent performance for analysis of practical samples, thus providing a new avenue for the development of signal amplification strategy and immunoassay methods.