Enzymatic hydrolysis by cutinase of PEG-co PLA copolymers spread monolayers

The mechanism of the hydrolysis by cutinase and the progressive fragmentation of lactic chains in diblock copolymers of PLA with various sizes attached to PEG were studied in a 2D monolayers model system. The hydrolysis kinetics was followed by measuring simultaneously the decrease of the surface area and evolution of the surface potential with time at barostatic conditions. The decrease of the surface area is due to the solubilization of the copolymers as well as of their hydrolytic products: detached PEG blocks and small soluble PLA fragments. The evolution of the surface potential detects the transient interfacial accumulation of charged insoluble PLA fragments. A kinetic model describing the enzymatic hydrolysis was developed and the values for the global hydrolytic kinetic constant were obtained without any fitting parameter. It was found that the global kinetic constant no practically depend on the length of the lactic and the presence of polyethylene–glycol chains.