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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.

Scientists of the Ural Federal University (UrFU) have created a completely new sensor device for measuring the level of cholesterol in the blood. The system does not use protein compounds, particularly enzymes. Chemists replaced them with copper chloride, which is an inorganic analog. This made it possible to create more affordable cholesterol meters and improve the speed, convenience and accessibility of blood testing. The results of the study were recently published Journal of Electroanalytical Chemistry.

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

He continues. “Enzymes are also natural polymers, proteins, therefore, tend to denature and require certain storage conditions, temperature and acidity regimes. We decided to choose a non-biological analogue of this enzyme to make the process of cholesterol analysis cheaper, easier and faster. One of the most accessible options is copper chloride, which we found for the first time to be highly sensitive to cholesterol,” explains Andrey Okhokhonin, Associate Professor at the Department of Analytical Chemistry at UrFU.

Andrey Okhokhon

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

The new technology simply requires a small amount of blood to detect cholesterol levels. The blood is placed in an analyzer containing a solution of copper chloride in acetonitrile. This chip includes an electrode connected to a voltammetric analyzer that provides the analysis results. The new chip’s ability to analyze cholesterol levels also features magnetic nanoparticles with molecularly imprinted polymers that selectively absorb cholesterol while filtering other blood substances important to blood composition.

“Molecularly imprinted polymers are needed to efficiently separate cholesterol from blood. After trying several options, we chose ethylene glycol dimethacrylate as the crosslinking agent and vinylpyridine as the functional monomer. The polymer synthesized on the surface of magnetic nanoparticles effectively absorbs cholesterol, so we can talk about the high selectivity of the analysis, because no other substance interferes,” Andrey Okhokhonin emphasizes.

The microfluidic chip, in which all the elements of the system are integrated, is printed on a 3D printer, which also simplifies the manufacturing process of the device, making it faster. The scientists note that the first test they performed was not on biological samples, but on model solutions simulating 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 without developing enzyme sensors to determine the amount of biologically important substances such as glucose, urea, creatinine, etc.

Cholesterol

Total cholesterol contained in the body within normal limits is an important substance without which the proper functioning of the body is impossible. It can be found in certain amounts in all body fluids and tissues. Cholesterol is a mandatory component of cell membranes, it is responsible for the order, compactness and stability of the lipid biofilm. In addition, it is involved in regulating the permeability of cell walls, determining which molecules can enter the cell and which cannot.

High blood cholesterol is a symptom of a number of diseases, such as 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 for Enzyme-Free and Low-Potential Cholesterol Detection in a 3D-Printed Microfluidic Flow Cell” by Andrei V. Okhokhoni, Marina I. Stepanova, Tatiana Son. and Alisa N. Kozitsina, 28 September 2022. Journal of Electroanalytical Chemistry.
DOI: 10.1016/j.jelechem.2022.116853



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