Comparison between DNA Immobilization Techniques on a Redox Polymer Matrix

In this paper we report a label-free detection method of unmodified DNA using polypyrrole as an immobilization matrix by impedance measurement. A probe and a target complementary DNA sequence specific for the bacterial pathogen, Bacillus cereus are used. Impedance measurements are performed without using additional redox probes. The effects of hybridization and non-specific binding are compared when the Probe DNA molecules were immobilized by two different methods: electrochemical adsorption and entrapment. The probe DNA immobilized using electrochemical adsorption yielded better hybridization signals compared to that immobilized using the entrapment method. Control experiments were also performed to prove the specificity of the biosensor in the presence of non complementary DNA. Negligible unspecific binding with the immobilized probe was observed with the electrochemically adsorbed probe, whereas the entrapped probe responded to the non complementary target. The performance of the DNA sensor was characterized using both cyclic voltammetry and impedance spectroscopy techniques and proved to be effective in terms of specificity of hybridization events.