Rapid diagnosis of acute myocardial infarction (AMI) is critical in the clinical setting. An automated and rapid chemiluminescence immunoassay system based on digital microfluidics (DMF) is suggested for cardiac troponin I (cTnI). This method involves a double antibody sandwich structure. The cTnI antigen in the sample to be analyzed was captured by magnetic beads encapsulated with the cTnI antibody, which was subsequently recognized by the biotin-labeled secondary antibody. Horseradish peroxidase (HRP)-labeled streptavidin may be conjugated to biotin and used to mark the cTnI antigen because of the unique way that biotin binds to avidin. The simultaneous recognition of the cTnI antigen by primary and secondary antibodies in sandwich form, as well as the high specificity of the reaction between streptavidin and biotin, considerably improves the sensitivity and specificity of this technique for cTnI detection. This approach has decent stability. For cTnI samples, the full process took 40 minutes, with a limit of detection (LOD) of 0.39 ng mL− 1. Additionally, there was a significant correlation range from 0.39 to 25 ng mL− 1, with a correlation value of 0.994. The CV (Coefficient of variation) value was 2.26%. This system is anticipated to be used for the clinical measurement of cTnI in human serum.

Herein, we have constructed a magnetic graphene field-effect transistor biosensor for highly sensitive detection of cardiac troponin I (CTNI). Graphene film was used as a conductive channel and transferred onto a glass substrate with two indium tin oxide (ITO) electrodes. CTNI aptamer was immobilized onto the graphene film via 1-pyrene-butanoic acid succinimidyl ester (PBASE) to capture CTNI. Magnetic nanobeads modified with CTNI antibody were added to the reaction chamber to form an aptamer/CTNI/antibody/magnetic nanobeads sandwich-type complex. By applying a periodic magnetic field, we found that the magnetic force exerted on the complex leads to an impedance change of the graphene film. The results were rationalized using a model wherein the magnetic force causes the CTNI aptamer strand to bend, thereby resulting in magnetic nanobeads/CTNI aptamer modulation of the double conductive layer of graphene transistors. With periodic sampling integration, different concentrations of CTNI can be detected with high sensitivity. Due to the specific binding property of the aptamer to the antigen, the magnetic graphene field-effect transistor biosensor can be used for the specific detection of different kinds of proteins and can potentially be a detection tool for DNA, specific cells, etc.