Magnetically immobilized nanoporous giant proteoliposomes as a platform for biosensing.

We report a biosensing method that is based on magnetically immobilized functional liposomes. The vesicles encapsulate magnetic nanoparticles (MNP) and enzymatic sensing reagents. Magnetic attraction between MNP and external magnets first immobilizes liposomes onto the surface of a coverglass. With the assistance from α-hemolysin (aHL), translocations of analytes through a lipid membrane trigger intravesicular enzymatic reactions. After 90 s incubation, the product from the sensing reactions, resorufin, was probed by laser-induced fluorescence. Detection of two analytes, glucose and ethanol, was demonstrated using two types of functional vesicles. The effects of MNP-containing vesicles and biotinylated vesicles on aHL's translocations of analytes were also compared. Unlike biotinylated lipids, MNP facilitate immobilization of liposomes without compromising the integrity of membrane and pore-forming activity of aHL.