Manganese porphyrin-dsDNA complex: a mimicking enzyme for highly efficient bioanalysis.

Manganese porphyrin (MnTMPyP)-dsDNA complex was reported as an excellent mimicking enzyme of peroxidase. It possessed high catalytic activity and much quicker catalytic kinetics and better stability with exposure to light irradiation and high temperature than both horseradish peroxidase and hemin/G-quadruplex DNAzyme. The groove binding of MnTMPyP to the dsDNA scaffold efficiently maintained the catalytic activity of the MnTMPyP center and improved its stability. By combining with an isothermal hybridization chain reaction (HCR) and in situ formation of MnTMPyP-dsDNA, a highly efficient chemiluminescent (CL) immunosensing method was proposed. After a sandwich immunoreaction, a biotinylated DNA strand, which was bound to biotinylated signal antibody by streptavidin, triggered the HCR and growth of MnTMPyP-dsDNA on the immunocomplex. The in situ, HCR-assisted enzyme formation brought numerous enzymatic catalytic centers, MnTMPyP, on the immunocomplex, resulting in significant CL signal amplification and highly sensitive CL detection. Using carcinoembryonic antigen as the model target, the proposed CL immunoassay method showed a wide linear range from 10 pg/mL to 100 ng/mL with a detection limit of 6.8 pg/mL. The new MnTMPyP-dsDNA complex could be conveniently synthesized, functionalized, and combined with DNA amplification strategies, showing a promising potential in bioanalysis and other relative fields.