Graphene Oxide Modulating the Bioelectronic Properties of Penicillinase Immobilized in Lipid Langmuir-Blodgett Films

In this paper, graphene oxide was incorporated in penicillinase-lipid Langmuir monolayers and transferred to solid supports as Langmuir-Blodgett (LB) films so that the enzyme catalytic properties could be evaluated. Adsorption of penicillinase and graphene oxide on dimyristoylphosphatidic acid (DMPA) monolayers at the air-water interface was investigated by tensiometry, vibrational spectroscopy, and Brewster angle microscopy. The LB films were characterized by quartz crystal microbalance, infrared spectroscopy, luminescence spectroscopy, and atomic force microscopy. Enzyme activity was studied with UV-vis spectroscopy, and the feasibility of the supramolecular device nanostructured as ultrathin films was essayed as an optical sensor device. The presence of graphene oxide in the enzyme-lipid LB film not only tuned the catalytic activity of penicillinase but also helped conserve its enzyme activity after weeks. These results may be related not only to the molecular architecture provided by the film but also to the synergism between the compounds on the active layer, leading to a molecular architecture that allowed a fast analyte diffusion owing to a suitable molecular accommodation which also preserved the penicillinase activity. This work then demonstrates the feasibility of employing LB films composed of lipids, graphene oxide, and enzymes as optical devices for biosensing applications as a proof-of-concept experiment.