Researchers in Kazan have created a sensor that quickly measures blood levels of the amino acid L-cysteine. This substance is a building block for proteins, and a drop in its levels can lead to serious diseases such as diabetes, Alzheimer’s and Parkinson’s. The device uses an electrode coated with a thin film of ionic liquid. The oxidized form of the liquid reacts with L-cysteine, altering the sensor’s signal and effectively acting as a detector for the presence of this amino acid in human blood. In future, the device could measure L-cysteine levels in the field, much like a glucometer used to self-monitor blood sugar.
The sensor’s operating principle is similar to an electrocardiogram: the device records current peaks, and their height reveals the amount of L-cysteine in the sample.
To test the sensor, the scientists prepared artificial blood samples containing different amounts of L-cysteine. They immersed the ionic-liquid-coated electrode into the solution and applied a voltage. An electrochemical analyser connected to the electrode recorded oxidation peaks. The more L-cysteine in the sample, the more the ionic liquid peak decreased.
“Our sensor is easy to assemble both in the lab and in the field, and all the materials are quite cheap,” said Yuri Kuzin, lead researcher on the project at the Butlerov Institute of Chemistry at Kazan Federal University. “Using disposable electrodes made by screen printing, the method can be scaled up and used outside medical facilities.”
The scientists also demonstrated that the sensor works in the presence of molecules similar to L-cysteine in structure and properties. They said they plan to develop sensors based on other sensing compounds to expand the range of organic substances the device can detect.
Current medical practice uses liquid chromatography to measure blood L-cysteine levels — a method that separates blood components under high pressure. However, this approach is time‑consuming, requires trained personnel and a stationary laboratory, and the chromatography equipment is expensive.