Polyelectrolyte Polyethylenimine–DNA Complexes in the Composition of Voltammetric Sensors for Detecting DNA Damage

A voltammetric DNA sensor based on the polyelectrolyte complexes of polyethylenimine and DNA obtained by self-assembly from solutions of components on a glassy carbon electrode has been developed. Cyclic voltammetry was used to study the preparation conditions and characterize the permeability of the complex for low-molecular-weight redox indicators differing in the mechanism of interaction with DNA (methylene blue and methylene green). The formation of the polyelectrolyte complex was independently confirmed by surface plasmon resonance measurements. The redox peak currents of methylene blue and methylene green varied differently depending on the number of layers of the complex and the nature of the outer layer due to different mechanisms of binding the indicators to DNA molecules and varied assembly density of the complex polyelectrolytes. An increase in the concentration of polyions from 0.1 to 10 μg/mL suppressed the effect of the charge of the outer layer on the indicator currents. Polyelectrolyte coatings were tested to detect specific DNA interactions including intercalation with the anticancer drug doxorubicin and the thermal and chemical denaturation of DNA. It was found that the introduction of decacarboxylated pillar[5]arene into the layer increased the sensitivity of the methylene blue signal to the thermal denaturation of DNA. A comparison between changes in the peak currents of methylene blue and methylene green makes it possible to distinguish the mechanism of DNA damage and separately take into account the contribution of the considered chemical and physical damaging factors. The developed DNA sensor makes it possible to semiquantitatively evaluate the protective effect of antioxidants, which decrease the effect of reactive oxygen species on DNA in the biosensor.