Development of a paper microfluidic surface enhanced Raman scattering assay for cardiac troponin I

The accurate and rapid diagnosis of myocardial infarction (MI) is essential to implement timely and definitive treatment to the patient. Cardiac Troponin I (cTnI) has been widely used as a biomarker for early diagnosis of MI. Point-of-care (POC) testing is favored because it can provide timely results when the patient is first encountered (e.g. ambulance, clinic, or emergency department). However, the clinical cut-off of cTnI for diagnosis of MI is in the pico- to femto-molar range (i.e. 0.01-0.1 ng/ml). Thus, a sensitive sensing system is needed to quantitively measure cTnI at the POC. Surface-enhanced Raman spectroscopy (SERS) is a sensitive optical technique that can be used to measure trace analytes in a sample. Moreover, paper-based sensing systems have demonstrated potential as a platform to implement assays, especially at the POC. This research describes the development of a paper-based SERS assay for detection of cTnI in the physiological relevant range. Aptamer is used in the assay for recognizing the cTnI in a sample. SERS is used to sensitively transduce the sensing signal from the assay. A handheld Raman spectrometer is used to measure the SERS signal. By measuring the change in the SERS signal, the concentration of target molecule is quantitatively determined. Moreover, spectral processing techniques are used to evaluate their effect on signal-to-noise ratio as well as sensitivity of the assay. Results showed the designed sensing system can be used to measure cTnI (0-0.5 ng/mL) in standard buffer solutions.