Researchers have fabricated a sensitive biochip based on modified graphene that can detect extremely low concentrations of cardiac troponin I, a marker protein that signals the onset of a heart attack1. This biochip could potentially be used to measure the serum levels of the protein troponin for diagnosing heart attacks.
Troponins are intracellular proteins that regulate muscle contraction. Of the various troponins, troponins I and T regulate the activity of the heart muscle cells. During heart attacks (for example, acute myocardial infarctions), cardiac muscle cells die and release troponin I into blood. Existing techniques for measuring the levels of troponin I are tedious and time consuming.
To devise a fast and simple technique for detecting troponin I, the researchers produced a biochip by depositing modified graphene on a silicon chip containing finger-like electrodes made from gold and titanium and then attaching troponin-I-specific antibodies to it.
To assess the troponin-I-sensing efficiency of this biochip, the researchers performed electrochemical studies by exposing it to carbonate buffer solutions containing different concentrations of troponin I, which acted as an antigen. When the biochip was exposed to the highly charged troponin protein, its conductance deceased. This change in the observed current was attributed to the charges induced in the graphene channel in the biochip due to interactions between the antibodies and the antigens.
Detailed analysis revealed that the biochip could detect troponin I concentrations of between 0.01 and 1 nanogram per millilitre. This biochip could selectively detect troponin I even in the presence of interfering chemical agents usually present in biological fluids. This biochips’ ability to detect the marker protein in human serum samples has the potential to be harnessed in clinical research and diagnosis.
