Di(Thioether Sulfonate)‐Substituted Quinolinedione as a Rapidly Dissoluble and Stable Electron Mediator and Its Application in Sensitive Biosensors

Abstract

The commonly required properties of diffusive electron mediators for point-of-care testing are rapid dissolubility, high stability, and moderate formal potential in aqueous solutions. Inspired by nature, various quinone-containing electron mediators have been developed; however, satisfying all these requirements remains a challenge. Herein, a strategic design toward quinones incorporating sulfonated thioether and nitrogen-containing heteroarene moieties as solubilizing, stabilizing, and formal potential-modulating groups is reported. A systematic investigation reveals that di(thioether sulfonate)-substituted quinoline-1,4-dione (QLS) and quinoxaline-1,4-dione (QXS) display water solubilities of ≈1 m and are rapidly dissoluble. By finely balancing the electron-donating effect of the thioethers and the electron-withdrawing effect of the nitrogen atom, formal potentials suitable for electrochemical biosensors are achieved with QLS and QXS (−0.15 and −0.09 V vs Ag/AgCl, respectively, at pH 7.4). QLS is stable for >1 d in PBS (pH 7.4) and for 1 h in tris buffer (pH 9.0), which is sufficient for point-of-care testing. Furthermore, QLS, with its high electron mediation ability, is successfully used in biosensors for sensitive detection of glucose and parathyroid hormone, demonstrating detection limits of ≈0.3 × 10 −3 m and ≈2 pg mL −1 , respectively. This strategy produces organic electron mediators exhibiting rapid dissolution and high stability, and will find broad application beyond quinone-based biosensors.

Evaluation of the chemical composition and nutritional value of lettuce (Lactuca sativa L.) biofortified in hydroponics with iodine in the form of iodoquinolines

“…In our study, the highest content of iodine was found in lettuce enriched with 8-hydroxy-7-iodo-5quinolinesulfonic acid, and a higher level of iodine than in plants supplemented with KIO 3 was also found in lettuce treated with 5,7diiodo-8-quinolinol. The explanation why the highest iodine concentration was observed in plants supplemented with 8hydroxy-7-iodo-5-quinolinesulfonic acid may be that in the presence of a highly polar sulfone group (-SO 3 H), hydrophobic aromatic compounds become hydrophilic and acidic, which increases their solubility in the water (Nandhakumar et al, 2022).…”

Dicarboxylate-containing and fully substituted ferrocene with rapid dissolvability, high solubility, good stability, and moderate formal potential for mediated electrochemical detection

“…Therefore, this interference significantly decreases detection accuracy. When three major interfering\species (UA, AcP, and AA) [29][30][31] were additionally present, the slope in the chronocoulogram (curve iii of Fig. 5c) became considerably larger than that obtained in their absence (curve ii), indicating that these interfering species significantly influenced the electrochemical background currents.…”

“…Phosphate-buffered saline (PBS, pH 7.4) contained 10 mM phosphate, 0.138 M Carbon ultramicroelectrodes (diameter = 10 mm) were prepared as previously reported. 31 The synthetic procedures of five Fc compounds (Fc9m1c, Fc8m1c, Fc8m2c, Fc1c, and Fc2c in Fig. 2) are shown in Fig.…”

“…27 Moreover, the applied potential should be close to 0 V vs. Ag/AgCl (preferably between À0.1 and 0.1 V) to minimize electrochemical background currents caused by factors such as electroactive interfering species and electrode redox reactions. [29][30][31] Consequently, the E 0 0 of an Fc compound should preferably be located within the range of 0.0-0.2 V. However, an Fc compound that can simultaneously satisfy the desired E 0 0 range along with rapid dissolvability, high solubility, and high stability cannot easily be obtained.…”

Overview on the Development of Electrochemical Immunosensors by the Signal Amplification of Enzyme- or Nanozyme-Based Catalysis Plus Redox Cycling

“…For instance, Ichzan et al designed an EN redox cycling system involving ITO electrodes, 1,4-naphthoquinone, DT-D, and NADH [ 155 ]. Nandhakumar et al developed an electrochemical immunosensor with di(thioether sulfonate)-substituted quinoline-1,4-dione (QLS) as the electron mediator for DT-D-involving EN redox cycling [ 156 ]. As shown in Figure 13 A, the naphthoquinone core was substituted with a thioether sulfonate group for the achievement of high hydrophilicity, rapid dissolubility, high stability, moderate formal potential, and high electron mediation ability.…”