Ionic interactions are monitored to detect hybridization. The measurement may be done measuring the potential change in the solution with the ion sensitive electrode (which may be the conducting polymer (e.g., polyaniline) itself), without applying any external energy during the binding. The double helix formation during the complimentary hybridization makes this electrode act as an ion selective electrode—the nucleotide hydrogen bonding is specific and thus monitoring the ionic phosphate group addition becomes selective. Polyaniline on the surface of nylon film forms a positively charged polymer film. Thiol linkage can be utilized for polyaniline modification and thiol-modified single strand oligonucleotide chains can be added to polyaniline. The sensitivity is because the double helix formation during the complimentary hybridization makes this electrode act as an ion selective electrode as the nucleotide hydrogen bonding is specific and thus monitoring the ionic phosphate group addition becomes selective.