Patients having experienced the
ischemia-reperfusion process are particularly vulnerable to subsequent
heart attacks because this process can induce myocardial
fibrosis, hallmarked by the release of
reactive oxygen species and some
proteases, such as
cathepsin G, into the circulating blood. If these risk indicators can be monitored from the peripheral serum, early diagnosis and intervention may become a reality. For this purpose, we have designed an assay of free
copper ions and
cathepsin G in serum using only synthetic small molecules as the biosensing elements. No
antibodies are needed to recognize the target
protein, and no
enzymes are needed to generate and amplify the biosensing signal. In this design, a short
peptide can target-specifically recognize
protease, while the
copper ion in the serum can stimulate the photoelectrochemical activity of the probe, resulting in cross-linking of the
serum proteins in a target
protein-specific manner. Using this method, serum
cathepsin G and free
copper ion are found to be significantly elevated in the blood samples collected from patients with acute
myocardial infarction and successful
percutaneous coronary intervention in comparison with healthy controls, indicating a higher risk of subsequent myocardial injury and cardiovascular events. These results may point to the possible application of the proposed assay to evaluate the severity and prognosis of cardiac
ischemia/reperfusion in the near future.