Developing Electrochemical Biosensors for Point-of-care Diagnostics of Cardiovascular Biomarkers

Troponin is known as a type of reliable biomarker for the detection of cardiac disorders. Cardiac troponin I (cTnI), as a subunit of troponin, is highly sensitive to cardiac injury; therefore, the cTnI level is used as an index to diagnose myocardial damage, particularly acute myocardial infarction. It can be also used in cardiospecific diagnosis, risk stratification therapeutic treatment and post risk management. In this research, an amperometric immunosensor was developed based on planar electrode and sandwich ELISA format. The electrical response corresponding to biological information was obtained via four main procedures, including electrode modification, immunoreaction, signal amplifications and amperometric detection. Enzyme labels such as horseradish peroxide (HRP) and alkaline phosphatase (ALP) were used for signals amplification. Since alkaline phosphatase works better in low background current levels and has great reproducibility, it was used for nanomaterials, chitosan, gold nanoparticle, carbon nanotube as electrode modification investigation. The anti-cTnI antibody is detectable by electrochemical technology. Necessary conditions and interferences of the experiment were examined. Detection range was from 0.001 ng ml-1 to 300 ng ml-1 on PDDA-MWCNT sensor, and from 0.02 ng ml-1 to 200 ng ml-1 on chitosan-AuNPs sensor. The detection range was investigated using cyclic voltammetry. The signal behavior recorded was linear to cTnI concentration. This behavior makes the developed biosensor be able to widely use in clinical practice. Likewise, two liquid substrates were catalyzed by hydroquinone and 3, 3’, 5, 5’-teteramethylbenzidine respectively. Hydrogen peroxide (H2O2) is a product of glucose oxidizes catalyzing the oxidation of β-D-glucose by oxygen. It is also used as an oxidizing agent in catalyzing HRP. Hence, an HRP-based immunosensor is important in integrating an immunosensor and an enzyme sensor for the purpose of achieving multianalyte detection compacted on one chip. The cTnI immunosensor developed here is rapid, easy-to-use, cost-efficient and robust