Neostigmine Potentiometric Sensors Based on Microfabricated Copper Electrodes Using Poly(3-octylthiophene) as an Ion-to-Electron Transducer Layer

The microfabricated potentiometric electrodes have been used in the field of medicine and biological sciences in the last few decades due to their various in-vivo sensing applications in addition to the cost effectiveness and easy processing. The proposed microfabricated electrodes use a low cost copper (Cu) substrate material on sensitized printed circuit board (PCB) which is easily patterned and compatible with the microfabrication processing. In this study, we further introduce the chemically prepared poly(3-octylthiophene) (POT) as an ion-to-electron transducer layer between the microfabricated Cu electrode and the ionophore-doped ion-selective membrane. The incorporation of POT reduced the potential drift from ∼7 mV h −1 for bare Cu electrodes to ∼1 mV h −1 for POT modified Cu electrodes because of its hydrophobic nature. In addition, the dynamic response time was obviously decreased from (11 ± 7 s) to (3 ± 2 s) due to the fast transduction. Furthermore, ionophore screening has been performed using calix[6]arene and calix[4]arene to enhance the membrane selectivity towards neostigmine (NEO) as a model drug analyte. The proposed sensors showed higher sensitivity, lower LOD when compared to the ionophore-free membrane. The incorporation of calix[4]arene ionophore improved the selectivity towards NEO in the presence of its potential impurities.