A New Device for Measuring Cholesterol

New technology is less expensive, more efficient, and quicker than traditional analogs.

Researchers at the Ural Federal University (UrFU) have created a brand-new sensor device for measuring blood cholesterol levels. The system does not use protein compounds, namely enzymes. They were replaced by chemists with copper chloride, an inorganic analog. This made it possible to create cholesterol meters more affordably and to improve the speed, convenience, and accessibility of blood testing. The study’s findings were recently published in the Journal of Electroanalytical Chemistry.

“Cholesterol determination is currently performed using colorimetry, chromatography, and enzymes. However, these methods use either extremely aggressive reagents or complex and expensive equipment, or – as recognizing and sensitive 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 acidity regimes. We decided to select a non-biological analog of this enzyme to make the process of cholesterol analysis cheaper, easier and faster. One of the most affordable options is copper chloride, which we first discovered to be highly sensitive to cholesterol,” explains Andrei Okhokhonin, Associate Professor at the UrFU Department of Analytical Chemistry.

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

The new technology just requires a small amount of blood to detect cholesterol levels. The blood is put in an analyzing chip containing a solution of copper chloride in acetonitrile. This chip includes an electrode that is coupled to a voltammetric analyzer that gives the analysis’s results. The new chip’s ability to analyze cholesterol levels also has the benefit of including magnetic nanoparticles with polymers with molecular imprints that selectively absorb cholesterol while filtering out other substances of blood that are important for blood composition.

“Molecular imprinted polymers are needed to effectively separate cholesterol from other substances in the 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 sorbs cholesterol, so we can talk about high selectivity of analysis, as no other substances interfere,” emphasizes Andrei Okhokhonin.

The microfluidic chip, in which all elements of the system are integrated, is printed on a 3D printer, which also facilitates the production process of the device, making it faster. 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 for determining the number of biologically important substances, such as glucose, urea, creatinine, and others.

Cholesterol

Total cholesterol contained in the body within normal limits is an important substance, without which the proper functioning of the body is impossible. In a certain 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.

Elevated 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 new electrocatalytic system based on copper (II) chloride and magnetic molecularly imprinted polymer nanoparticles in 3D printed microfluidic flow cell for enzymeless and Low-Potential cholesterol detection” by Andrei V. Okhokhonin, Marina I. Stepanova, Tatiana S. Svalova and Alisa N. Kozitsina, 28 September 2022, Journal of Electroanalytical Chemistry.
DOI: 10.1016/j.jelechem.2022.116853