Revealing the analytical potential of thin organic film electrodes: Electrochemical insights into anticancer drug docetaxel at liquid|liquid interfaces

Abstract

A thin organic film electrode (TOFE) system was employed for the indirect electrochemical investigation of docetaxel (DTX), an anticancer drug from the class of mitotic inhibitors. The TOFE consists of a thin membrane immobilized on a carbon electrode substrate, composed of a water-immiscible organic solvent that forms a stable liquid│liquid interface upon immersion in an aqueous electrolyte. Due to the high oxidation potential of DTX at solid electrodes, an alternative detection strategy was adopted based on the interaction between DTX and the liquid|liquid interface of the TOFE. Systematic optimization of the organic and aqueous phase compositions, as well as the electrode material, was first performed in the absence of DTX to ensure reliable and reproducible conditions at the interface. The optimized TOFE system, based on nitrobenzene as the organic solvent, perchlorate anions as the supporting electrolyte, and an edge-plane pyrolytic graphite as electrode material, provided the best performance. The optimal electrochemical response was also observed when perchlorate anions were present in the aqueous phase, while the nature of the cations in the aqueous phase had negligible influence. The optimized TOFE system was then used to study the effect of DTX on ion transfer processes at the liquid│liquid interface, where a pronounced, concentration-dependent inhibitory effect was observed. Electrochemical investigations using cyclic voltammetry and square-wave voltammetry (SWV), including frequency- and amplitude-dependent analyses, demonstrated that DTX adsorbs to the membrane│water interface, forming blocking layer that markedly slowing ion transfer and displacing the quasi-reversible maxima beyond the instrumentally accessible window. The system exhibited a linear analytical response in the concentration range of 10.0–100.0 μmol L⁻¹ DTX, with low detection and quantification limits when analyzed by SWV. The LOD values were 3.27 μmol L⁻¹ (anodic) and 3.26 μmol L⁻¹ (cathodic), while the LOQ were 9.90 μmol L⁻¹ and 9.89 μmol L⁻¹, respectively. These findings validate the TOFE platform as a robust and versatile tool for the indirect detection of redox-inactive pharmaceutical compounds in biphasic electrochemical systems. Given the key role of mitotic inhibitors like DTX in cancer therapy, studying their behavior at biomimetic interfaces may advance understanding of drug–membrane interactions and support the development of improved delivery and diagnostic strategies.