Voltammetric Understanding of Ionizable Doxorubicin Transfer Reactions across Liquid/liquid Interfaces and Sensor Development

Highlights: •Voltammetric studies of doxorubicin transfer reaction across liquid/liquid interfaces. •Establish phase diagram for doxorubicin and provide lipophilicity information. •Thermodynamic properties for doxorubicin transfer across liquid/liquid interfaces. •Doxorubicin sensitive sensor using a microhole array-liquid/gel interface. •Good detection limit with good selectivity over interfering species. -- Abstract: The transfer characteristics of the ionizable anticancer drug doxorubicin (DOX) across a polarized interface between two immiscible electrolyte solutions (ITIES) were investigated using voltammetry. Aqueous buffer solutions at different pH with a controlled ionic strength were interfaced with 1,2-dichloroethane in order to understand the nature of charged DOX. Following voltammetric investigation, an ionic partition diagram was established which can be correlated to the lipophilicity of DOX and further used for predicting specific charged forms of DOX in the aqueous phase at a certain pH value. Thermodynamic properties including the formal transfer potential, partition coefficient and Gibbs energy of DOX transfer processes at the water/1,2-DCE interface were also evaluated. At a buffer solution of pH 7 the peak current responsible for protonated DOX (HDOX⁺) transfer across the ITIES gave a good linear relationship with the DOX concentration enabling a DOX sensitive voltammetric sensor to be developed. As a sensing demonstration for practical applications, a microhole supported water/organic gel interface was fabricated and used in conjunction with differential pulse stripping voltammetry (DPSV) to quantitatively analyze HDOX⁺ in buffer followed by applying to local river water and human serum sample solutions. The results from the HDOX⁺ sensor were then compared to those obtained using conventional high-performance liquid chromatography (HPLC).