Developing a localized surface plasmon aptasensor for the early detection of acute myocardial infarction

Abstract

Acute myocardial infarction (AMI) is a deadly disease wherein the coronary arteries become blocked, causing irreversible death to myocardial wall tissue which can result in heart failure. Current clinical methods lack the sensitivity and time efficiency needed to effectively diagnose AMI. Aptamer-based sensors (aptasensors) have been investigated as a potential rapid diagnostic technique for AMI. The high binding coefficient and selectivity of aptamers make them a desirable alternative to protein-based antibodies for developing new diagnostic platforms. Cardiac troponin I (cTnI) is one of the protein biomarkers released into the bloodstream when an AMI event occurs. Some aptasensors have been developed for cTnI detection, but not much work has used localised surface plasmon resonance (LSPR) as a sensing platform. LSPR sensing is fast, easy to use and highly sensitive to the dielectric environment on the surface of noble metal nanostructures and has shown promise for bioanalytical sensing. The objective of this thesis was to build a plasmonically active aptasensor specific to cTnI using LSPR as a proof-of-concept detection method. A glass cover slip was used as the substrate upon which silver nanostructures were assembled in a single layer using nanosphere lithography. The aptamer was immobilised onto this surface and thiols were used to fill in surface gaps to reduce non-specific binding and avoid false positives. The aptasensor was then tested to determine its ability to detect the presence of cTnI. Control measurements determined that the thiols and the aptamer did not hinder the LSPR readings. Unfortunately, the sensor could not be successfully functionalized by the aptamer because the reducing agent used in the aptamer causes delamination of the silver on the substrate and destroys the plasmonic functionality of the sensor. More studies are needed to optimize this new sensor platform.