Dual Monitoring of Surface Reactions in Real Time by Combined Surface-Plasmon Resonance and Field-Effect Transistor Interrogation

Abstract

By combining surface plasmon resonance (SPR) and electrolyte gated field-effect transistor (EG-FET) methods in a single analytical device we introduce a novel tool for surface investigations, enabling simultaneous measurements of the surface mass and charge density changes in real time. This is realized using a gold sensor surface that simultaneously serves as a gate electrode of the EG-FET and as the SPR active interface. This novel platform has the potential to provide new insights into (bio)adsorption processes on planar solid surfaces by directly relating complementary measurement principles based on (i) detuning of SPR as a result of the modification of the interfacial refractive index profile by surface adsorption processes and (ii) change of output current as a result of the emanating effective gate voltage modulations. Furthermore, combination of the two complementary sensing concepts allows for the comparison and respective validation of both analytical techniques. A theoretical model is derived describing the mass uptake and evolution of surface charge density during polyelectrolyte multilayer formation. We demonstrate the potential of this combined platform through the observation of layer-bylayer assembly of PDADMAC and PSS. These simultaneous label-free and real-time measurements allow new insights into complex processes at the solid−liquid interface (like non-Fickian ion diffusion), which are beyond the scope of each individual tool.

Simplifying Molecular Transport in Polyelectrolyte Multilayer Thin Films

“…have introduced a new tool to analyze the surface charge density through real‐time analysis by using combining surface plasmon resonance (SPR) and electrolyte gated field‐effect transistor (EG‐FET). [ 158 ] Using this novel platform, they have demonstrated the potential of their technique by the observation of LbL assembly of (PDDAC/PSS). A significant feature of this technique is that the complex processes at the solid–liquid interface can be investigated from multiple viewpoints.…”

Reduced graphene oxide–based field effect transistors for the detection of E7 protein of human papillomavirus in saliva

“…Upon non-specific interaction with the surface, it increases the negative charge at the semiconductor surface and counteracts the applied electric field. On the other hand, the electric field will increase upon specific binding of the aptamer to HPV-16 E7 proteins, due to the conformational change and increased distance of the negatively charged RNA from the surface [32,33].…”

Label free detection of miRNA-21 with electrolyte gated organic field effect transistors (EGOFETs)

“…Electrolyte gated organic field effect transistors (EGOFET) are a new label-free platform able to quantify picomolar concentrations of several biomarkers (Casalini et al, 2015(Casalini et al, , 2013Di Lauro et al, 2016;Macchia et al, 2020;Magliulo et al, 2013). This architecture offers the opportunity to integrate complementary techniques sensitive to biorecognition, such as fluorescence microscopy or surface plasmon resonance (Aspermair et al, 2020). EGOFET enables ultrasensitive detection of antigens because the electrostatic potential of the gate, which is affected by antigen binding on recognition sites, is capacitively coupled to the channel, and yields an amplified shift on the Fermi level of the organic semiconductor, even for low amount of biomolecules adsorbed or grafted on the gate electrode (Berto et al, 2016).…”