Development of Cubosomes as a Cell-Free Biosensing Platform

The parallel between the lipidic microenvironments of the inverse bicontinuous cubic phase and the biological membrane distinguishes cubic phases as an attractive option for development of cell-free biosensors containing protein or glycolipid receptors. Herein we describe a novel strategy toward the creation of a biosensing platform derived from the surface attachment of a colloidally stable inverse cubic structure (cubosomes). We report the preparation of cubosomes composed of the amphiphile phytantriol, the membrane glycolipid receptor monosialoganglioside-G(M1) and the biotin-functionalized amphiphile 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[biotinyl(polyethyleneglycol)-2000] (bDSPE). The tethering of cubosomes to the various surfaces was mediated through bDSPE binding to streptavidin-and avidin-modified surfaces. Allylamine plasma polymer surface modification enhanced the surface immobilization of avidin, which increased the density of bound cubosomes. The resultant polymer-protein-cubosome complex was imaged by cryo-transmission electron microscopy analysis and the cubosome structure was impressively preserved within the complex. Cholera toxin binding to cubosomes containing G(M1) was used to assess the performance of the cubosomes, subsequent to surface attachment, via a modified enzyme-linked immunosorbent assay. Specific immobilization of complex protein-receptor-cubosome systems paves the way for development of a structurally complex, heterogeneous platform for sensing applications.