Aptasensor based on a flower-shaped silver magnetic nanocomposite enables the sensitive and label-free detection of troponin I (cTnI) by SERS

Acute myocardial infarction (AMI) is nowadays the leading death cause worldwide. For that reason, the early diagnosis of AMI is of central importance to reduce the risk of death. In this sense, aptamer-based sensors for surface-enhanced Raman spectroscopy (SERS aptasensors) emerged as an interesting alternative for future high-performance diagnostic tools. SERS aptasensors combine the fast, precise, and sensitive nature of SERS measurements with the selectivity of aptamers for specific biological targets. Herein, we report an efficient SERS aptasensor for the detection of cardiac troponin I (cTnI), a gold-standard biomarker for AMI. Our SERS platform comprises a magnetite core with an intermediate silica shell, and a flower-shaped silver layer (Fe₃O₄@SiO₂@Ag) to confer excellent plasmonic properties and ease of collection by magnetism. The branched silver structure combined with magnetic aggregation offers a high near-field amplification to superior SERS performance. Additionally, a tailored DNA aptamer with high specificity for cTnI was anchored to the silver surface to produce the aptasensor with increased sensing capability towards cTnI. With our SERS aptasensor, a cTnI concentration as low as 10 ng ml^-1 (10^-11 mol l^-1) could be detected. This value is ten times lower than the upper threshold of the typical concentration range of cTnI of AMI patients. Hence, our SERS aptasensor holds great promise to be explored in AMI diagnosis.