Microscale cephalosporin ion-selective amperometric/voltammetric sensors based on a micropipette-supported liquid/liquid interface: Multiple purposes of transmembrane studies and real-time determinations

Abstract

The permeability of cephalosporins through cell membranes is crucial for their efficacy against gram-negative bacteria. To address this, a microsoft biphasic sensor utilizing the interface between two immiscible electrolyte solutions (ITIES) has been introduced for studying the ion transfer of cefotiam (CTM), ceftazidime (CAZ) and cefepime (CPM). The typical voltammograms of cephalosporin ion transfer can be further used to determine the formal ion transfer potentials (${∆}_{\text{o}}^{\text{w}}{\phi }_{\text{A}}^{\prime }$), ion transfer Gibbs free energies (${∆}_{\text{o}}^{\text{w}}{G}_{\text{A}}^{\prime }$), effective hydrophilicity (logP_i), geometry of micro-ITIES, diffusion coefficient (D_w) and ion transfer rate constant (k⁰). In addition, the partitioning of CTM⁺, CAZ⁺, and CPM⁺ in two phases at different pH values was revealed by the corresponding ion partition diagrams (IPDs). The IPDs can further elucidate the mechanism of cephalosporin ion transfer across the ITIES at different pH values. Finally, the determination of CTM⁺, CAZ⁺ and CPM⁺ was achieved via real-time chronoamperometry. An excellent linear range for cephalosporin ions with a satisfactory limit of detection was obtained. The findings show the superb selectivity and anti-interferent ability of micro-ITIES sensors toward cephalosporins. The constructed micro-ITIES sensors for cephalosporin could contribute to medicinal design, single microorganism metabolism analysis, clinical diagnosis, and food safety inspection.