Noble-metal nanozymes have demonstrated great potential
in various
fields. However, aggregation of single-particle nanoparticles severely
affects their exposed catalytically active sites to the extent of
exhibiting weak enzyme-like activity. Here, we present an organic
block surfactant (polyvinylpyrrolidone, PVP) to construct monodisperse
water-stable Pt nanoclusters (Pt NCs) for an enhanced immunoassay
of cardiac troponin I (cTnI). The PVP-modified Pt NC nanozyme exhibited
up to 16.3 U mg–1 peroxidase-mimicking activity,
which was mainly attributed to the ligand modification on the surface
and the electron-absorbing effect of the ligand on the Pt NCs. The
PVP-modified Pt NCs have a lower OH-transition potential, as determined
by density functional theory. Under optimized experimental conditions,
the enhanced nanozyme immunoassay strategy exhibited an ultrawide
dynamic response range of 0.005–50 ng mL–1 for cTnI targets with a detection limit of 1.3 pg mL–1, far superior to some reported test protocols. This work provides
a designable pathway for the design of artificial enzymes with high
enzyme-like activity to further expand the practical range of enzyme
alternatives.