Signal amplification strategy for biomarkers: Structural origins of epitaxial-growth twinned nanocrystals and D-π-A type polymers.

The combination of nanoparticles and biomarkers yields functional nanostructured biointerface, which is playing a notable role in biotechnology development. Due to the 5-fold twined structure in the Au-Pt star-shaped decahedra not only allowed it to act as efficient scaffold for immobilization of antibody, but it also exhibits superior electrocatalytic activity toward H2O2 reduction, the nanocrystal as the efficient signal transduction label is first employed to construct an electrochemical immunosensor. Donor-π-Acceptor (D-π-A) linking fashion generates a dipolar push-pull system and assures superior intramolecular charge transfer. It is considered as a suitable π-conjugated backbone for conducting polymer on biointerface application. Under a D-π-A architecture which imidazole as the π-bridge and amino phenyl/phenyl groups as peripheral electron-donating/withdrawing functional groups, 4-(2,4,5-triphenyl-1H-imidazol-1-yl) aniline (TPIDA) is designed and synthesized for good biocompatibility and high conductivity. In this proposal, we attempt to integrate the above-mentioned two features from nanobiotechnology and organic bioelectronics. Then, a novel nonenzymatic sandwich-type immunosensor is performed by Au-Pt core-shell with surface-engineered twinning as a label and π-conjugated D-π-A polymers as the signal amplification platform. Human IgG (HIgG) as the model target protein can be detected with a wide linear range from 0.1 pg mL-1 to 100 ng mL-1. The detection limit is down to 0.06 pg mL-1 (S/N = 3). Moreover, as a practical application, the prepared biosensor is used to monitor HIgG level in human serum with desirable results obtained.