Sandwich-like electrochemical immunosensor based on thionine-modified graphene aerogels for ultrasensitive assay of cardiac troponin I in human serum.

Cardiac troponin I (cTnI) is the primary disease marker for acute myocardial infarction (AMI). In this study, we successfully constructed an electrochemical immunosensor based on diazotization reaction to achieve ultrasensitive detection of cTnI. Taking their structural advantages, gold nanostars (Au NSs) were introduced to combine more capture antibodies. Through diazotization reaction, graphene aerogels (GAs) successfully captured thionine (Thi) molecules obtaining GAs-Thi. Specifically, the three-dimensional porous network structure of GAs was utilized to capture more Thi molecules and the chemical bond effect ensures a stable signal output. Meanwhile, the structural advantages of GAs also contribute to the anchoring of detection antibodies. Under the specific recognition effect of antigens and antibodies, a sandwich-like biosensor was successfully constructed, which showed a wide detection range (1 × 10-4 - 100 ng mL-1) and a low detection limit (27.2 fg mL-1). Given the stable signal output, the signal reproducibility of sensors from different batches was excellent with a relative standard deviation (RSD) of only 1.07%. Even more surprisingly, the sensor's signal response remained at 90.35% of the initial value after 3 weeks. Finally, the biosensor demonstrated good accuracy in human serum samples, conforming its high potential for biomedical applications.