Interactions of Catalytic Enzymes with n-Type Polymers for High-Performance Metabolite Sensors

Abstract

The tight regulation of the glucose concentration in the body is crucial for balanced physiological function. We developed an electrochemical transistor comprising an n-type conjugated polymer film in contact with a catalytic enzyme for sensitive and selective glucose detection in bodily fluids. Despite the promise of these sensors, the property of the polymer that led to such high performance has remained unknown, with charge transport being the only characteristic under focus. Here, we studied the impact of the polymer chemical structure on film surface properties and enzyme adsorption behavior using a combination of physiochemical characterization methods and correlated our findings with the resulting sensor performance. We developed five n-type polymers bearing the same backbone with side chains differing in polarity and charge. We found that the nature of the side chains modulated the film surface properties, dictating the extent of interactions between the enzyme and the polymer film. Quartz crystal microbalance with dissipation monitoring studies showed that hydrophobic surfaces retained more enzymes in a densely packed arrangement, while hydrophilic surfaces captured fewer enzymes in a flattened conformation. X-ray photoelectron spectroscopy analysis of the surfaces revealed strong interactions of the enzyme with the glycolated side chains of the polymers, which improved for linear side chains compared to those for branched ones. We probed the alterations in the enzyme structure upon adsorption using circular dichroism, which suggested protein denaturation on hydrophobic surfaces. Our study concludes that a negatively charged, smooth, and hydrophilic film surface provides the best environment for enzyme adsorption with desired mass and conformation, maximizing the sensor performance. This knowledge will guide synthetic work aiming to establish close interactions between proteins and electronic materials, which is crucial for developing high-performance enzymatic metabolite biosensors and biocatalytic charge-conversion devices.

Unraveling the Electrochemical Electrode Coupling in Integrated Organic Electrochemical Transistors

“…Such a capacitance‐dependent change in the transfer characteristics is expected, [ 6 ] and it is the basis of OECT‐based biosensing, for example, in metabolite sensors. [ 39 ] Subsequently, we investigated the EEC‐induced shift in the threshold/turn‐off voltage in Figure S4c–e (Supporting Information) for devices with a small, medium, and large gate, respectively. All devices show a significant shift with increasing V ds , ranging from 854 (small gate) to 735 (medium gate) to 657 mV V ‐1 (large gate).…”

Materials design and applications of n-type and ambipolar organic electrochemical transistors

“…When the surface carries a negative charge, it encourages the enzyme to adopt an optimal orientation for effective catalysis. 20 In addition, the potential of using enzymatic fuel cells for self-powered sensors was also explored. A glucose-fueled power supply was developed utilizing a GOx-adsorbed P-90 anode and an organic cathode p(EDOT- co -EDOTOH) (Fig.…”

“…In recent years, there has been a growing focus on the application research of n-type materials and ambipolar materials. These include constructing complementary logic circuits, 16–18 enhanced electrophysiological recordings, 19 high-sensitivity electrochemical biosensing, 20–22 and versatile neuromorphic simulation 23 (Fig. 1).…”

Spiers Memorial Lecture: Challenges and prospects in organic photonics and electronics

“…To enhance glucose sensitivity, Ohayon et al employed multiphoton lithography to 3D-print oxygen-sensitive materials encapsulating glucose oxidase (GOx). 76 In the study of OECTs, Torricelli and colleagues conducted a comprehensive investigation into the ionic-electronic interactions within these devices. They revealed that the measurements were comprehensively explained by the electrostatic bulk uptake of ions within the OECTs, which neutralized both xed and mobile electronic charges.…”

“…To enhance glucose sensitivity, Ohayon et al employed multiphoton lithography to 3D-print oxygen-sensitive materials encapsulating glucose oxidase (GOx). 76…”