New functional proteo-glycolipidic molecular assembly for biocatalysis analysis of an immobilized enzyme in a biomimetic nanostructure

A new organized biomimetic nanostructure embedding a monoclonal antibody in a lipidic matrix has been designed to sequester a hydrophilic enzyme in an oriented position and allowed to preserve the enzyme activity over a few months. The nanostructure was constituted of a glycolipid and a noninhibitory monoclonal IgG directed against the soluble form of acetylcholinesterase (AChE). A mixed monolayer (IgG-glycolipid) was obtained by spreading mixed IgG-glycolipid vesicles at the air/buffer interface. Several measurements (pi-A isotherms, surface potential measurements, and compression-decompression cycles) allowed us to demonstrate the presence of IgG in the monolayer, as well as a reorientation of IgG molecules during the compression. After transfer on solid supports by the Langmuir-Blodgett technique, the presence of IgG in the mixed monolayer was characterized by ATR FTIR spectroscopy. Linking of the AChE on the IgG-glycolipid matrix was realized by immunoaffinity, and the enzyme was shown to retain its activity. The opportunity to detect a strong enzymatic activity, even after transfer at high surface pressures, suggested a preferential orientation of the antibody, favorable to retain the enzyme active at the surface of the nanostructure. The homogeneity of the transferred monolayer before and after immunoassociation, observed by Nomarski microscopy, did not display any structural modification. The enzyme kinetics was typical of the biocatalytic behavior of an immobilized enzyme, with a decrease of reaction rates due to the lower accessibility to the substrate at higher enzyme content. With the advantages of stability and favorable orientation of IgG, this new active matrix induces, in turn, a favorable orientation of the enzyme bound by immunoaffinity. The typical enzymatic behavior of the ternary nanostructure (glycolipid-IgG-AChE) demonstrates the usefulness of such a functional molecular assembly for biocatalysis study in a biomimetic situation.