Human cardiac troponin I sensor based on silver nanoparticle doped microsphere resonator

Abstract

Human cardiac troponin I (cTnI) is a specific biomarker for diagnosis of acute myocardial infarction (AMI). In this paper, a composite sensing system of an optical microsphere resonator and silver nanoparticles based on surface enhanced Raman scattering (SERS) and stimulated Raman scattering (SRS) techniques towards a point of care diagnostic system for AMI using the cTnI biomarker in HEPES buffered solution (HBS) is proposed. Pump and Raman signals enter the optical fiber coupling into the microsphere, and then SRS occurs in the microsphere. The presence of silver nanoparticles on the microsphere surface provides a tremendous enhancement of the resulting Raman signal through an electromagnetic enhancement of both the laser excitation and Stokes-shifted light of the order of 1010. This enhancement occurs in metals as surface plasmon resonance (SPR), which increases the Raman gain through the SERS effect. Our simulation results show that this sensor presents a linear response for cTnI detection. The calculated enhanced Raman signal can be employed to detect the cTnI molecules around the microsphere.