Surface-Bound Lipid Vesicles Encapsulating Redox Species for Amperometric Biosensing of Pore-Forming Bacterial Toxins

A new method is described to signal the presence of a staphylococcal toxin (streptolysin, SLO) by a membrane-based biosensor fabricated with bilayer vesicles of phosphatidylcholine lipids and cholesterol on a gold electrode. The controlled release of encapsulated redox species from the surface-bound vesicles is mediated by the pore-formation functionality of SLO, allowing amperometric detection of the targeted toxin. Effects of BSA and Triton-100 on membrane permeability and redox release have been assessed, and a thin layer electrolysis mechanism has been proposed to account for the observed voltammetric behavior. The method is applicable to the detection of functionally similar protein toxins.