Introduction: Over the last decades, the production of nanomaterials and nanoparticles has been rapidly growing on the global scale. Different tests are available for the purposes of determining interactions between different nanoparticles and biological systems. In the master’s thesis, the enzyme test is used which aims to evaluate the biological reactivity of various nanoparticles with the test of inhibition and adsorption of acetylcholinesterase test. The data on biological activity is crucial in evaluating their safe use and in the development of new products containing nanomaterials. Purpose: The purpose of this master's thesis is to evaluate the rate of adsorption of the TiO2 particle suspension on the acetylcholinesterase enzyme and the inhibition of enzymatic activity using the spectrophotometric Ellman method. The purpose is also to show how the concentration and properties of the particles affect the enzyme activity and to compare the relation between enzyme adsorption and inhibition. Methods: A modified Ellman method, adapted to work with microtiter plates, was used. The effect of twelve different TiO2 particles on the inhibition and adsorption of acetylcholinesterase was measured. The reaction between the nanoparticles which were used, the Ellman’s reagent, the enzyme and the added acetylthiocholine chloride substrate results in the formation of a yellow-colored complex, which was recorded at a wavelength of 405 nm. Eserine was used as a positive control. Results: TiO2 particles with sizes between 5 and 100 nm showed the highest rate of inhibition and adsorption of acetylcholinesterase, whereas the particles with sizes between 100 and 500 nm showed a lower rate. The different crystal structure of the particles in our study did not affect the enzyme activity. At higher particle concentrations, the effect on enzyme activity was greater, especially with particles which had more than 10 % impact on enzyme activity. In the particles used, the effect on inhibition was greater than the effect on adsorption. Discussion and conclusion: The method described in the master's thesis can be used to further investigate the interactions between enzymes and nanoparticles.