DNA sensor based on carbon black/Methylene Blue arylamine analogue composite for doxorubicin detection

In modern analytical chemistry, various methods are being actively developed to simplify and reduce the cost of electrochemical sensor fabrication, thereby increasing the accessibility of these technologies for a wide range of users, including medical institutions, industrial enterprises, and research laboratories. In this study, we present a DNA sensor based on a screen‑printed carbon electrode modified with a carbon black suspension in propylene carbonate and diffusion‑free 3,7‑bis(4‑aminophenylamino)phenothiazin‑5‑ium chloride for doxorubicin detection. The sensor operates via drop‑based analysis using a printed graphite electrode, which ensures compactness and enhanced practical usability. The addition of carbon black to the SPСE surface significantly enhances the signal of diffusion‑free phenothiazine in buffer solution, thereby improving both sensitivity and the quality of the analytical signal during biospecific analyte–DNA interactions. The specificity of this interaction was confirmed by substituting sodium polystyrene sulfonate for DNA. The sensor demonstrated high sensitivity in detecting doxorubicin both in buffer solutions and in model biological fluid samples containing high levels of interfering components. The detectable doxorubicin concentration ranges from 1 pM to 1 μM, with a limit of detection of 0.8 pM. The developed DNA sensor offers several advantages that render it promising for clinical applications, including minimal reagent requirements, high sensitivity, and ease of use.