A three-stage amplified pressure bioassay for sensitive detection of cardiac troponin

Cardiac troponin I (cTnI) level in human blood is a key biomarker associated with acute myocardial infarction (AMI). Rapid, convenient, inexpensive and highly sensitive point-of-care (POC) bioassays for cTnI in home and community are of great importance in saving the lives of AMI patients. Herein, we present a three-stage amplified pressure-sensing bioassay system for highly sensitive detection of cTnI. Specifically, the magnetic bead-cTnI-Pt nanoclusters protein complex formed by the immunoconjugation of antigen and antibody can be conveniently subjected to magnetic separation to reduce background interference and achieve first-stage amplification. Then, the Pt nanoclusters in the complex can effectively catalyze the decomposition of H₂O₂ into O₂, thus achieving the secondary amplification of the pressure signal. Finally, the biotin and streptavidin cross-linked Pt nanoclusters significantly increase the amount of catalyst, enabling the tertiary amplification of the bioassay. The method has good linearity in the range of 10 to 1 × 10⁴ pg/mL for quantitative detection, and the detection limit of the method was calculated to be 3.8 pg/mL (in water), which is 30 times more sensitive than the original secondary amplification detection system. In addition, the results of clinical samples tested with the developed method were consistent with those tested with commercial kits. Given the automation, rapid response and miniaturization of pressure-based sensors, our bioassay is expected to be a powerful tool for home and community-based POC diagnosis of patients with various acute diseases in the future.