A new 3D-printed sensor device that uses an inorganic analogue has been developed that can determine cholesterol levels in blood 

Scientists at the Ural Federal University (UrFU) have developed a new sensor device for determining cholesterol levels in the blood. The system does not use protein compounds, namely enzymes. Chemists replaced them with an inorganic analogue – copper chloride. This made the process of creating cholesterol meters cheaper as well as making blood testing easier, faster and more accessible.

Andrei Okhokhonin, an associate professor at the UrFU Department of Analytical Chemistry, said: “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 recognising 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. Enzymes are also natural polymers, proteins, so they are prone to denaturation and require certain storage conditions, temperature and acidity regimes.

“We decided to select a non-biological analogue 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.”

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separate cholesterol

To measure cholesterol levels with the new device, just a small amount of blood is needed. The blood is placed in an analysing chip containing a solution of copper chloride in acetonitrile, then an electrode is integrated into this chip, which is connected to a voltammetric analyser that gives the results of the analysis.

The advantage of the new chip analysing cholesterol levels is that it also contains magnetic nanoparticles with polymers with molecular imprints that selectively sorb cholesterol, screening out any other substances characteristic of blood composition.

Okhokhonin added: “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 synthesised on the surface of magnetic nanoparticles effectively sorbs cholesterol, so we can talk about high selectivity of analysis, as no other substances interfere.”

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. 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.

The scientists have been conducting research for several years to develop enzyme-free sensors for determining a number of biologically important substances, such as glucose, urea, creatinine, and others.

The study is published in the Journal of Electroanalytical Chemistry.

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