Heart monitor

Engineering researchers at the University of Arkansas have fabricated and tested a biosensor that measures concentrations of potassium and hydrogen ions in the human heart.


The research could lead to a superior method of monitoring indicators of acute myocardial ischemia (AMI): one of the leading causes of cardiovascular failure.


‘AMI is triggered by insufficient blood supply to the heart muscles,’ said Taeksoo Ji, assistant professor of electrical engineering. ‘This lack of blood supply results in excess anaerobic metabolism, or lack of oxygen, which we know is accompanied by an increase in potassium and hydrogen ions released from cardiovascular cells. The goal is to develop a robust – yet inexpensive – sensor that rapidly detects these chemicals that signal the onset of AMI.’


Various types of biosensor designs, including ion-selective optical fibres, waveguides, nanoparticle fluorescence sensors and ion-selective electrodes, have been used to detect potassium and hydrogen in the blood stream.


Working in the Organic Electronics and Devices Laboratory, Ji, research assistant professor Soyoun Jung and student Pratyush Rai took a different approach by developing an ion-sensitive field-effect transistor – another type of sensor used to detect potassium and hydrogen in blood.


Most ion-sensitive field-effect transistors are silicon based. Instead of silicon, Ji’s team worked with a low-cost organic semiconductor known as poly 3-hexylthiophene, which they fabricated on a flexible substrate.


The researchers also developed a smoothing and noise calculation technique to cut down the effect of external electric fields on the devices from the heart itself.


The myocardium, or the middle section of the heart wall, for example, has intense electrical activity. To operate properly, implantable biosensor devices must be immune to these electric fields or background noise.