When heart muscles are damaged, a protein, cardiac troponin I, is released into the bloodstream. The change in the level of this protein helps confirm the diagnosis and assess the extent of the damage.
Elevated levels of cardiac troponin I can be detected using antibodies specifically created against the protein. The method is very sensitive and specific to myocardial injury. However, anti-troponin antibodies generated by the body interfere with these tests, leading to inaccurate results.
Recently, researchers from the Vel Tech Rangarajan Dr Sagunthala R&D Institute of Science and Technology and the National Institute of Technical Teachers Training and Research, Chennai collaborated with a researcher in Taiwan, to address the problem.
They tried surface plasmon resonance to detect troponin 1. Surface plasmon resonance detects biomolecular binding by exciting surface plasmons at a metal-dielectric interface. Binding events on the sensor surface increase mass concentration, altering the local refractive index. This change shifts the resonance angle, which can be measured in real-time and displayed, quantifying the binding.
For the metal part, the researchers used molybdenum tungsten disulfide, which exhibits surface plasmonic resonance with specificity. Previous studies report that this material has low cytotoxicity and genotoxicity.
The team had already worked with the material to detect cardiac troponin T. Cardiac troponin I is, however, a better marker. The researchers used hydrothermal exfoliation, the method they had used in the previous instance, to synthesise molybdenum tungsten disulfide nanosheets. Though the method is laborious, boringly repetitive and takes a few days, it provides high purity nanosheets.
Field emission scanning electron microscopy showed that each layer is about three nanometres. The material was crystalline and hexagonal.
To fabricate the device, the researchers removed some material from one side of a fibre, creating a flat surface for interaction. On this surface, they deposited the molybdenum tungsten disulfide nanosheets as a thin layer. Then, they placed specific antibodies designed for cardiac troponin I on top of the molybdenum tungsten sulfide. This whole setup went inside a small polydimethylsiloxane chamber with an inlet and an outlet for liquids.
They passed a white light through one end of the fibre and, using a spectrometer, they recorded the wavelengths coming through at the other end. The spectrometer was connected to a computer to save the patterns of frequencies that emerged.
To test the sensor, they pumped different concentrations of cardiac troponin I solutions into the chamber for fifteen minutes each at a slow speed. They then recorded the changes in the light patterns for each antibody concentration using the computer. When troponin I interacts with the antibody, the molybdenum tungsten disulfide nanosheets respond by changing the resonance angle of the light passing through the fibre.
The researchers found that their biosensor had a consistent linear response for cardiac troponin I antibody concentrations from 100 to 300 picograms per millilitre. A good and reliable response for detecting cardiac troponin I from human serum!
Diagnostic manufacturing companies need to test these research findings in real world conditions to produce devices for the preclinical diagnosis of cardiovascular diseases.
DOI: 10.1109/TNB.2025.3548823
Reported by Sileesh Mullasseri
Assistant Professor, St. Albert’s College, Ernakulam
STEAMindiaReports 
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