Impact of Self-Assembled Monolayer Design and Electrochemical Factors on Impedance-Based Biosensing

Abstract

Real-time sensing of proteins, especially in wearable devices, remains a substantial challenge due to the need to convert a binding event into a measurable signal that is compatible with the chosen analytical instrumentation. Impedance spectroscopy enables real-time detection via either measuring electrostatic interactions or electron transfer reactions while simultaneously being amenable to miniaturization for integration into wearable form-factors. To create a more robust methodology for optimizing impedance-based sensors, additional fundamental studies exploring components influencing the design and implementation of these sensors are needed. This investigation addresses a sub-set of these issues by combining optical and electrochemical characterization to validate impedance-based sensor performance as a function of (1) biorecognition element density, (2) self-assembled monolayer chain length, (3) self-assembled monolayer charge density, (4) the electrochemical sensing mechanism and (5) the redox reporter selection. Using a pre-existing lysozyme aptamer and lysozyme analyte combination, we demonstrate a number of design criteria to advance the state-of-the-art in protein sensing. For this model system we demonstrated the following: First, denser self-assembled monolayers yielded substantially improved sensing results. Second, self-assembled monolayer composition, including both thickness and charge density, changed the observed peak position and peak current. Third, single frequency measurements, while less informative, can be optimized to replace multi-frequency measurements and in some cases (such as that with zwitterionic self-assembled monolayers) are preferred. Finally, various redox reporters traditionally not used in impedance sensing should be further explored. Collectively, these results can help limit bottlenecks associated with device development, enabling realization of next-generation impedance-based biosensing with customize sensor design for the specific application.

Development of Electrochemical Aptasensor for Lung Cancer Diagnostics in Human Blood

“…The consistent immobilization of LC-18 and BTO led to a surface coverage increase up to ≈70%, almost twice more extensive than for the aptamer alone ( Figure 4 , Table 3 ). As reported by Brothers with co-authors [ 35 ], denser SAMs are preferred for impedance-based biosensors. In our opinion, in the case under study, the modifying layer was dense enough to partially block the surface redox probes reactions, and it sparse enough to avoid steric hindrance for the aptamer molecules to bind target objects (tumor marker molecules).…”

“…Mercaptohexanol (MCH), mercaptoethanol (MET), bovine serum albumin (BSA) [ 60 ], commercial proteins [ 27 ], etc. [ 35 ], are quite widely used as BAs. However, large proteins may lead to a steric hindrance for the sensing aptamer layer ( Figure 1 ), and short thiols form SAMs with a low stability under electrode potential change [ 51 ].…”

“…However, the more complex the system, the less reproducible and stable it is when in use [ 30 ]. Furthermore, an improved understanding of the key factors in the origin and response formation of the biosensor signal is an important step towards developing advanced electrochemical sensing platforms [ 35 ]. Generally, the electrochemical responses of the aptasensors in the presence and absence of target molecules are compared, and known hypothetical mechanisms are suggested [ 36 ].…”

Software Implementation and Design of Information Encryption Algorithm Based on DNA Nano Self‐Assembled Sensor Array

“…DNA molecules follow the W-C principle, DNA strands can react spontaneously without manual participation, and the parallelism is huge. Therefore, in the development process of self-assembly technology, these natural advantages of DNA molecules provide conditions for the development of DNA self-assembly [12]. DNA selfassembly mainly uses DNA molecules as basic materials, and the interaction forces such as base hydrogen bond and van der Waals force between molecules make molecules spontaneously form a relatively stable and complex molecular structure.…”

Electrochemical aptasensors: unravelling the critical interactions between aptamers, ligands, and electrodes

“…The ferri/ferrocyanide system is often chosen for this purpose. 105,106 With the use of a potentiostat directly linked to a three-electrode system (counter, reference, and working electrode), a direct current (DC) is applied and a small perturbation around the redox potential is created via the use of an alternating current (AC). The monitoring of the AC current as a function of frequency is providing information about the electron transfer between the solution and the electrode.…”