Figure 9.

(a) Impedance spectra acquired on a bare WE, the same WE after modification of the electrode surface with a DNA probe and after hybridization with a complementary DNA (cDNA) using the on chip and an external reference electrode. The difference between spectra recorded with the two different REs is minimal after the first modification but is increased when the surface of the on-chip reference electrode is further modified by the cDNA. However, detection of DNA hybridization is clearly possible using the on-chip RE; (b) Control experiment (using RE on chip) where a non-complementary DNA strand is first hybridized on chip. The EIS spectra remain virtually unchanged as no binding occurs between the DNA probe and the non-complementary strand.