Multifunctional cardiac tropin I sensing using MWCNTs-COOH/PoPD composites for integrated warning, screening and protection assessment of traditional Chinese medicine-induced cardiotoxicity.

Cardiac troponin I (cTnI), the most sensitive and specific biomarker of myocardial injury, enables early detection of subclinical cardiotoxicity. Highly sensitive cTnI testing is therefore crucial for early safety assessment of TCM. This study developed an electrochemical immunosensor for cTnI using a carboxylated multi-walled carbon nanotube/poly(o-phenylenediamine) (MWCNTs-COOH/PoPD) composite sensing membrane. This design leverages the large surface area and high conductivity of MWCNTs-COOH along with PoPD's biocompatibility to enhance electrochemical performance. Antibodies achieved controllable covalent immobilization with preferential orientation via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) cross-linking, facilitating specific recognition of cTnI. Under optimized conditions, the sensor exhibited excellent linearity across the ranges of 0.2-40 pg/mL and 0.05-50 ng/mL, with detection limits of 0.06 pg/mL and 4.17 pg/mL, respectively, demonstrating high sensitivity, specificity, and stability. Successfully applied to screen cardiotoxic TCM components, the sensor accurately detected cTnI released from cardiomyocytes, enabling precise quantification of toxins such as aconitine. It was also extended to evaluate myocardial protectants such as baicalin and their synergistic detoxification effects. This work establishes an efficient, sensitive platform for early TCM cardiotoxicity warning and toxic substance identification based on cTnI, while also supporting the screening of protective components. It is crucial for safeguarding the clinical safety of TCM and fostering the sustainable development of its industry.