Simultaneous Analysis of Ascorbic Acid, Uric Acid, and Dopamine at Bare Polystyrene Thermoplastic Electrodes

Surface Modification of Thermoplastic Electrodes for Biosensing Applications via Copper-Catalyzed Click Chemistry

Cu(I)-catalyzed 1,3-dipolar cycloaddition (CuAAC), also known as click chemistry, has been demonstrated to be highly robust while providing versatile surface chemistry. One specific application is biosensor fabrication. Recently, we developed thermoplastic electrodes (TPEs) as an alternative to traditional carbon composite electrodes in terms of cost, performance, and robustness. However, their applications in biosensing are currently limited due to a lack of facile methods for electrode modification. Here, we demonstrate the feasibility of using CuAAC following the diazonium grafting of TPEs to take advantage of two powerful technologies for developing a customizable and versatile biosensing platform. After a stepwise characterization of the electrode modification procedures was performed, electrodes were modified with model affinity reagents. Streptavidin and streptavidin-conjugated IgG antibodies were successfully immobilized on the TPE surface, as confirmed by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy.

Characterization of Factors Affecting Stripping Voltammetry on Thermoplastic Electrodes

Thermoplastic carbon electrodes (TPEs) are an alternative form of carbon composite electrodes that have shown excellent electrochemical performance with applications in biological sensing. However, little has been done to apply TPEs to environmental sensing, specifically heavy metal analysis. The work here focuses on lead analysis and based on their electrochemical properties, TPEs are expected to outperform other carbon composite materials; however, despite testing multiple formulations, TPEs showed inferior performance. Detailed electrode characterization was conducted to examine the cause for poor lead sensing behavior. X-Ray photoelectron spectroscopy (XPS) was used to analyze the surface functional groups, indicating that acidic and alkaline functional groups impact lead electrodeposition. Further, scanning electron microscopy (SEM) and electrochemical characterization demonstrated that both the binder and graphite can influence the surface morphology, electroactive area, and electron kinetics.

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

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 an ion-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 by electrochemical impedance spectroscopy (EIS), chronopotentiometric and potentiometric measurements. The Ca²⁺-ISE showed a Nernst response with a slope of 31.2 ± 0.6 mV/decade in the concentration range from 0.1 M to 10^-4 M Ca²⁺ with a limit of detection (LOD) of 1.0 × 10^-5 M. 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.