Facile and Sensitive Method for Detecting Cardiac
Markers using Ubiquitous pH Meters
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Abstract
A sensitive and easy method was developed
for the detection of
the cardiac marker troponin I using magnetic immunoassay and ubiquitous
pH meters. Monoclonal antibody-functionalized Fe<sub>3</sub>O<sub>4</sub> magnetic nanoparticle clusters (MNCs) were synthesized to
capture troponin in human serum, and MNC–troponin complexes
were magnetically isolated using a permanent magnet. These complexes
were subsequently conjugated to polyclonal antibody-functionalized
acetylcholinesterase (AchE) and dispersed in acetylcholine (Ach) solution.
As the Ach was hydrolyzed to choline and acetic acid, the pH of the
solution decreased, and the resulting pH change was measured in real
time using a pH meter. The sensitivity of detection of this assay
was found to be 10 pg/mL of troponin in human serum after 10 min of
the hydrolysis reaction. Further, the pH change could be determined
with the naked eye from the color change of a pH indicator strip
