SERS-based Magnetic Immunoassay for Simultaneous Detection of cTnI and H-FABP Using Core-Shell Nanotags

Acute myocardial infarction (AMI) is the single leading cause of mortality and morbidity worldwide. Heart-type fatty acid-binding protein (H-FABP) and Cardiac troponin I (cTnI), as biomarkers emerging at different stages of AMI, form complementary advantages in specificity and sensitivity. Therefore, we developed a magnetic immunoassay method based on surface-enhanced Raman scattering (SERS) to detect H-FABP and cTnI simultaneously. Herein, two mutually independent Raman reporter molecules were embedded between the gold core and silver shell and then combined with the tracer antibody to form SERS immunoprobe. During detection, the SERS immunoprobe, target antigen and captured antibody conjugated with biotin undergo immune reaction to form a sandwich structure, and then the immune complex was enriched by a specific reaction of streptavidin on the surface of magnetic beads with biotin. Finally, the concentration of biomarkers was quantified by detecting the characteristic Raman peaks intensities of the two Raman reporter molecules. Under the optimized conditions, the minimum detection limits of H-FABP and cTnI were 0.6396 and 0.0044 ng/mL, respectively. Besides, the target antigen does not cross-react with non-specific proteins, showing good specificity. Therefore, our proposed SERS-based magnetic immunoassay method has the advantages of accuracy, rapidity and good selectivity, and has great potential for early diagnosis of acute myocardial infarction disease.