Electrochemical sensors using gold submicron particles modified electrodes based on calcium complexes formed with alizarin red S for determination of Ca2+ in isolated rat heart mitochondria

A simple glassy carbon electrode (GCE) modified with gold submicron particles (AuSPs), characterized by a mean diameter of about 0.15-0.20 μm has been developed. Herein, the complexation reaction of Ca2+ with alizarin red S (ARS), in 0.1 M KOH, has been followed by electrochemical methods using the modified electrode which is able to catalyze the electro-reduction of ARS. When the stoichiometry ratio of Ca2+ and ARS is 1:2, a new reduction peak at a higher negative potential of −0.975 V appeared, and the peak of ARS at −0.815 V disappeared. The peak current of ARS in alkaline solution is proportional to the concentration of Ca2+ in the range 6.0×10−7-1.2×10−4 M with a limit of detection (LOD) of 5.1×10−7 M. Furthermore, the complex site of Ca2+ with ARS was analysized by the experimental UV-vis and infrared spectrums and those calculated electronic and vibrational spectroscopies with density functional theory (DFT). The good accordance between theoretical and experimental data confirms that chelation of calcium ion preferentially occurs at the deprotonated catechol site. Then, we implemented an electrochemical assay for the investigation of Ca2+ in preparations of isolated rat heart mitochondria, which demonstrates the submicron particles modified electrode is a simple and rapid sensor for determining the Ca2+ in the biological samples.