Aim. Our study aimed at investigating the effect of plant alkaloid Chelidonin as a monotherapy and in the co-treatment with carbon nanoparticles fullerene C₆₀ on the K⁺ ion permeability through hERG potassium channel using FluxOR assay. Conclusions. Thus, studies on potassium channels permeability are extremely important due to their wide-ranging effects on various physiological processes. The use of the FluxOR screening assay is an effective tool for identifying molecules that inhibit the cellular hERG potassium channels. The inhibitory effect of Chelidonin on the hERG potassium channels can be reduced by C₆₀ fullerene nanoparticles.