Water/AOT/Isopropyl Myristate Reverse Microemulsions as Media for Biocatalytic Reactions

This work examines the possibility of controlling biocatalytic reactions in self-organizing systems using cytochrome C as a catalyst. It is known that it can accelerate biological processes acting as a catalyst for cellular respiration. Microemulsions based on sodium bis(2-ethylhexyl)sulfosuccinate (AOT) are of significant interest as nanosized transport and reaction systems in biocatalysis, as they are capable of stabilizing enzymes while maintaining their functional activity. In this study, three-component water/AOT/isopropyl myristate systems with different compositions and degrees of hydration have been obtained. They have the structure of water-in-oil microemulsions with droplet sizes of 4.2–8.7 nm, as well as the structure of liquid crystals. The structure-related phase transformations in the systems under consideration have been studied upon increasing AOT concentration from microemulsions to a liquid crystalline mesophase. It has been found that the incorporation of cytochrome C into the microemulsions results in its good solubilization, which leads to a slight decrease in droplet sizes and their narrower distribution in the system. The UV–Vis and luminescence spectroscopy data have shown the occurrence of the adsorption interaction between the protein and the polar groups of AOT. The applicability of the obtained systems to biocatalysis has been investigated using the example of guaiacol oxidation with hydrogen peroxide in the presence of cytochrome C. To controllably increase the yield of the catalytic reaction product in the microemulsion, hydrophilic Cd0.9Mn0.1S/ZnS quantum dots stabilized with mercaptopropionic acid have been added to the microemulsion. It has been found that the yield of tetraguaiacol in the reaction increases in direct proportion to the concentration of the introduced quantum dots. Thus, the catalytic processes can be accelerated or slowed down using the microemulsions as reaction media.