Multilayered films made from tannic acid and alkaline phosphatasewith enzymatic activity and electrochemical behavior

Layer-by-layer-deposition of enzymes and polyphenols, like tannic acid may provide a reservoir of antioxidant and antibacterial molecules of controlled thickness and degradability with an additional activity due to the presence of the enzyme. The layer-by-layer deposition of films made from tannic acid and alkaline phosphatase is shown to yield an exponential growth with the number of deposited layer pairs. The films display the electrochemical behavior of tannic acid and the enzymatic activity of alkaline phosphatase. However, it is shown that only the enzyme close to the film-solution interface is active and follows the Michaelis-Menten mechanism. Similarly, only tannic acid close to the electrode-film interface can be oxidized. The enzymatic activity is almost completely lost when the multilayer film is treated with sodium periodate which oxidizes tannic acid even if the solubilized enzyme is not affected by the oxidant. This shows that the formation of covalent bonds between alkaline phosphatase and tannic acid is deleterious for its conformation and activity.