A new device to measure cholesterol

Printed microfluidic chip

The microfluidic chip, in which all the elements of the system are integrated, is printed on a 3D printer. Credit: Rodion Narudinov / UrFU

The new technology is less expensive, more efficient and faster than traditional analogues.

researchers of the Ural Federal University (UrFU) have created a new sensor device to measure cholesterol levels in the blood. The system does not use protein compounds, namely enzymes. They were replaced by chemicals with copper chloride, an inorganic analogue. This made it possible to create more affordable cholesterol meters and improve the speed, convenience, and accessibility of blood tests. The study findings were recently published in the Journal of Electroanalytical Chemistry.

“Currently, the determination of cholesterol is done by colorimetry, chromatography and enzymes. However, these methods use extremely aggressive reagents or complex and expensive equipment, or, as sensitive and recognition elements that determine cholesterol levels, enzymes, biological molecules that are extracted from living organisms. For example, the enzyme cholesterol oxidase is produced by some species of bacteria.

He continues: “Also enzymes are natural polymers, proteins, therefore they are prone to denaturation and require certain storage conditions, temperature and acid regimes. We decided to select a non-biological analogue of this enzyme to make the cholesterol testing process cheaper, easier, and faster. One of the most affordable options is copper chloride, which we found for the first time to be very sensitive to cholesterol,” explains Andrei Okhokhonin, associate professor at UrFU’s Department of Analytical Chemistry.

Andrei Ojohonin

According to Andrei Okhokhonin (pictured), the chips are immediately printed in the laboratory. Credit: Rodion Narudinov / UrFU

The new technology only requires a small amount of blood to detect cholesterol levels. The blood is placed on a test chip containing a solution of copper chloride in acetonitrile. This chip includes an electrode that is coupled to a voltammetric analyzer that outputs the analysis results. The new chip’s ability to analyze cholesterol levels also has the advantage of including magnetic nanoparticles with molecularly fingerprinted polymers that selectively adsorb cholesterol while filtering other substances from the blood that are important to blood composition.

“Molecular imprinting polymers are needed to effectively separate cholesterol from other substances in the blood. After testing several options, we chose ethylene glycol dimethacrylate as the crosslinking agent and vinylpyridine as the functional monomer. The polymer synthesized on the surface of the magnetic nanoparticles effectively absorbs cholesterol, so we can talk about a high selectivity of analysis, since no other substance interferes”, emphasizes Andrei Okhokhonin.

The microfluidic chip, in which all the elements of the system are integrated, is printed on a 3D printer, which also facilitates the production process of the device, making it faster. The scientists note that the first test they conducted was not on biological samples, but on model solutions that mimic blood serum. The next stage of the researchers’ work is to test the system on real blood samples.

Scientists have been conducting research for several years to develop enzyme-free sensors to determine the amount of biologically important substances such as glucose, urea, creatinine, and others.

Cholesterol

The total cholesterol contained in the body within normal limits is an important substance, without which the proper functioning of the body is impossible. In some amount, it can be found in all body fluids and tissues. Cholesterol is an obligatory component of cell membranes, it is responsible for the ordering, compactness and stability of the lipid biolayer. In addition, it is involved in regulating the permeability of cell walls, determining which molecules can penetrate the cell and which cannot.

High blood cholesterol is a symptom of a number of diseases, including atherosclerosis, hereditary diseases, chronic kidney failure, nephroptosis, hypertension, liver disease, and pancreatic diseases.

Reference: “A Novel Electrocatalytic System Based on Copper(II) Chloride and Magnetic Molecularly Imprinted Polymer Nanoparticles in a 3D-Printed Microfluidic Flow Cell for Enzyme-Free and Low-Potential Cholesterol Detection” by Andrei V. Okhokhonin, Marina I. Stepanova, Tatiana S. Svalova and Alisa N. Kozitsina, September 28, 2022, Electroanalytical Chemistry Journal.
DOI: 10.1016/j.jelechem.2022.116853

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