Cost-effective amperometric immunosensor for cardiac troponin I as a step towards affordable point-of-care diagnosis of acute myocardial infarction

Early detection of cardiac troponin I in blood is vital for acute myocardial infarction diagnosis. A low-cost thin film gold electrode array was used with affordable ELISA antibodies and reagents to fabricate two cardiac troponin I amperometric immunosensors. The HRP-labelled sandwich immunocomplex was constructed on the gold electrode surface, and chronoamperometry was used to quantify cTnI indirectly by measuring the amount of TMB+ produced at the electrode surface. First, the system was evaluated using a physisorption approach to immobilise the capture antibody to the electrode with a 309 pg/mL LOD observed. Subsequently, a second sensor variant was produced using sulfo-LC-SPDP as a crosslinker to control antibody immobilisation, which resulted in an improved sensitivity with an LOD of 109 pg/mL. The chemisorption sensor outperformed the working range of the commercially available ELISA kit used (8000–125 pg/mL), demonstrating the power of enhanced antibody immobilisation and electrochemical detection for clinically relevant levels of cardiac troponin I. Amperometric immunosensors offer vital advantages including being cost-effective, simple to use, and compatible with commercially available reagents. These features make the sensor accessible to users and easy to manufacture. With further improvements to sensitivity and performance in complex samples, the sensor could be deployed to streamline acute myocardial infarction diagnosis and reduce the burden of chest pain patients on the healthcare system.