Carbon composite thermoplastic electrodes integrated with mini-printed circuit board for wireless detection of calcium ions.

Abstract

Here, a smartphone-based portable sensing system is developed for real-time detection of Ca2+ ions in a variety of biofluids. A solid-contact calcium-selective electrode (Ca2+-ISE) consisting of anion-selective membrane (ISM), carbon black nanomaterial and polystyrene-graphite nanoplatelets as a solid contact was fabricated. The polyvinylchloride (PVC)-based ISM was optimized using different plasticizers and ion-exchangers. Under optimized conditions, the solid contacts were electrochemically characterized byelectrochemical impedance spectroscopy(EIS), chronopotentiometric andpotentiometric measurements. The Ca2+-ISE showed a Nernst response with a slope of 31.2 ± 0.6mV/decade in the concentration range from 0.1M to 10-4M Ca2+ with a limit of detection (LOD) of 1.0 × 10-5M. In addition, the ISEs exhibited good selectivity to Ca2+ ions over various interfering electrolytes and metabolites. The Ca2+-ISEs were applied in human urine and, artificial serum and cerebrospinal fluid samples. The ISEs showed good recoveries between 90 and 105%, indicating potential applicability of these electrodes in biological fluids. The portable lab-made potentiometer provides wireless data signaling and transmission to a smartphone and final Ca2+ concentration display due to its customized software. Therefore, the developed smartphone-based sensing platform offers low cost (< $25), rapid, user-friendly detection of Ca2+ especially in resource-limited areas.