Amperometric detection of Escherichia coli heat-labile enterotoxin by redox diacetylenic vesicles on a sol-gel thin-film electrode.

Supramolecular assemblies (bilayer vesicles) prepared from ferrocenic diacetylene lipid and the cell surface receptor ganglioside GM1 are utilized to construct an amperometric biosensor for Escherichia coli heat-labile enterotoxin on a sol-gel thin-film electrode. The bilayer vesicles adsorbed on the sol-gel film provide an open platform for molecular recognition, while the electrochemical communication between the incorporated redox lipids and the electrode is influenced by the binding of the toxin. Cyclic voltammetric studies suggest a facile redox reaction for the adsorbed supramolecular assembly, which allows the sensor to detect enterotoxin up to 3 ppm (3.6 x 10(-8) M) concentration. The apparent diffusion coefficients for the redox lipids in the assembly were observed to be in the range of 4.73 x 10(-8) -2.30 x 10(-8) cm/s2. A mechanism of lateral electron transport of redox lipids controlled by biomolecular recognition is proposed.