Fluorescence anisotropic probe for sensing cardiac troponin-I antigen through target-specific antibody-conjugated gold nanoclusters

Fluorescence anisotropy (FA) is a versatile and efficient platform for developing biosensors that rely on the rate of rotations of fluorescence molecular entities in biochemical systems. However, by virtue of its intricate complexity, FA is a neglected and less explored area for developing biosensors. Herein, we experimented with the possibility of developing a fluorescence anisotropic probe to detect cardiac troponin I (cTnI), the gold standard biomarker for acute myocardial infarction, via target-specific monoclonal antibody-conjugated gold nanoclusters. The successful detection of cTnI antigen in clinically relevant concentration with a low detection limit of 0.91 ng mL-1 was achieved. The specific molecular interaction between the cTnI antigen and its monoclonal antibody tagged at the surface of gold nanoclusters has restricted the free rotation of gold nanoclusters and increased the FA value. This incremental increase in FA can be correlated to the concentration of cTnI antigen in the sample, thereby achieving the quantitative linear detection of cTnI. The schematic representation of the molecular interaction enables fluorescence anisotropic detection of cTnI antigen.