ИСТИНА

A potentiometric biosensor for the detection of the DNA hybridization with the use of polyaniline (PANI) composite materials as indicator electrode was fabricated. The PANI composite materials were prepared chemically with template technique using Nylon. The resulting PANI-Nylon films were used as prepared. The non-covalent immobilization of single stranded oligonucleotides (probe) was carried out. The decrease of the indicator electrode potential was observed during the immobilization due to electrostatic interactions between positively charged PANI surface and negatively charged phosphate groups of oligonucleotide strands. The addition of the complementary stranded oligonucleotide (target) to the solution containing indicator electrode with immobilized probe leads to the increase of the indicator electrode due to the hybridization event occurring on the surface of PANI and leave the hybrid from the surface of the indicator electrode. The formation of the double helix and its release form PANI surface was proved with fluorescent spectroscopy. The covalent immobilization of the probe causes the similar drop of the potential of the indicator electrode. Addition of the target gives the similar positive response however is not accompanied with the release of the duplex from the electrode surface. The response amplitude of the biosensor depends on the amount of bases in the immobilized target and does not depend on the amount of guanine bases in the sequence. The experiments with synthetic polyanions have shown that the addition of the negatively charged polymer to the solution containing PANI as an indicator electrode causes minor response compared to that observed on probe immobilization. This fact indicates that interactions of single stranded oligonucleotides with polyaniline have rather specific nature than electrostatic.