Lactate is an important intermediate of metabolic processes, which is formed during anaerobic respiration. Accumulation of this compound may indicate various diseases, including cancer, so detection of lactate is important from a medical point of view. We report on the novel electrochemical lactate biosensors based on Prussian blue nanoparticles.

Synthesis of Prussian blue nanoparticles was carried out by means of the reaction between potassium hexacyanoferrate (III), iron (III) chloride and hydrogen peroxide, followed by ultrasonic dispersing of the suspension. The size of nanoparticles was determined using dynamic light scattering analysis and further operations were conducted using particles with diameters ranging from 20 to 60 nm. Prussian blue modified sensors were prepared by depositing nanoparticles on the surface of screen-printed carbon electrodes. The quality of electroactive coating was tested using cyclic voltammetry. The immobilization of lactate oxidase was performed through drop-casting on the sensor surface of mixture containing enzyme, (3-aminopropyl)triethoxysilane and isopropyl alcohol. Thus, after the formation of the (3-aminopropyl)triethoxysiloxane membrane biosensors were ready for electrochemical lactate detection.

The apparent Michaelis constant and inactivation constant (assuming that inactivation is pseudo first order reaction) were calculated (0.29±0.03 mM and 1.5±0.3 ms^-1, respectively) and compared with values obtained for previously known biosensors based on Prussian blue films. The developed lactate biosensors are not inferior in characteristics to those previously known, while the manufacturing process is less laborious and more reproducible.

Obtained values also indicate that lactate biosensors based on Prussian blue nanoparticles and lactate oxidase have sufficient sensitivity and operational stability for analytical purposes in medical and biological researches.