EVALUATION OF A GLASSY-CARBON ELECTRODE MODIFIED BY A BILAYER-LIPID MEMBRANE WITH INCORPORATED DNA

The objective of the present work was the evaluation and characterizat ion of a glassy carbon (GC) electrode modified by a bilayer lipid memb rane (BLM) with incorporated single-stranded deoxyribonucleic acid (ss DNA). Various procedures were developed and tested for the incorporat ion of ss DNA at the electrode modified by the lipidic membrane: 1. fo rmation of self-assembled BLMs over ss DNA adsorbed on the electrode s urface; 2. direct adsorption of ss DMA into a BLM modified GC electrod e; 3. formation of a BLM with incorporated ss DNA at the electrode sur face using the monolayer folding technique. Differential pulse voltamm etry (i.e. oxidation of guanine and adenine residues) was used to moni tor the incorporation of ss DNA at the GC electrode modified by the BL M. The results have shown that the lipid membrane enhances the stabili ty of ss DNA during a ''medium-exchange'' of the electrode and prohibi ts its diffusion from the electrode surface. The third scheme was prov en to be the most appropriate as both electrode modification by the BL M and DNA adsorption occur in one stage and much faster (as no BLM thi nning process is required) as compared to the former two techniques; f urthermore, maximized loading of DNA in BLMs is achieved which reduces by ca. 10-fold the DNA amounts that can be detected electrochemically . Conventional planar ''free-suspended'' and self-assembled metal supp orted BLMs were used to monitor in situ the incorporation of ss DNA in these membranes. The results have shown that the adsorption of ss DNA at lipid membranes (as a medium for DNA incorporation on an electrode surface) can occur much faster, using milder conditions and smaller a mounts of DNA than by previously described techniques.