Abstract
This review discusses a broad range of recent advances (2013–2017) in chemical imaging using electrochemical methods, with a particular focus on techniques that have been applied to study cellular processes, or techniques that show promise for use in this field in the future. Non-scanning techniques such as microelectrode arrays (MEAs) offer high time-resolution (<10 ms) imaging; however, at reduced spatial resolution. In contrast, scanning electrochemical probe microscopies (SEPMs) offer higher spatial resolution (as low as a few nm per pixel) imaging, with images collected typically over many minutes. Recent significant research efforts to improve the spatial resolution of SEPMs using nanoscale probes and to improve the temporal resolution using fast scanning have resulted in movie (multiple frame) imaging with frame rates as low as a few seconds per image. Many SEPM techniques lack chemical specificity or have poor selectivity (defined by the choice of applied potential for redox-active species). This can be improved using multifunctional probes, ion-selective electrodes and tip-integrated biosensors, although additional effort may be required to preserve sensor performance after miniaturization of these probes. We discuss advances to the field of electrochemical imaging, and technological developments which are anticipated to extend the range of processes that can be studied. This includes imaging cellular processes with increased sensor selectivity and at much improved spatiotemporal resolution than has been previously customary.
Highlights
Chemical imaging using electrochemical techniques comprises scanning electrochemical probe microscopies (SEPMs)
Alternating current-scanning electrochemical microscopy (SECM) uses impedance, and relies on an electrochemical signal for feedback which could change during a scan, and tip-position modulation (TPM) may require additional models that take into account the nature of the underlying substrate [33]
Pourmand and coworkers [103] used the ion current through an aptamer functionalized solid-contact transduction by ion nanogating (STING) sensor nanopipette to demonstrate reversible and quantitative detection of thrombin. This technology has been limited to bulk solution measurements far, but imaging using the principles of STING should be practically achievable, since these sensors can be readily and cheaply made at nanometer dimensions and they demonstrate reversibility to changing target concentration, with a response time of a few seconds
Summary
Chemical imaging using electrochemical techniques comprises scanning electrochemical probe microscopies (SEPMs). (h) A double barrel glass pipette, with one barrel filled with pyrolyzed carbon for use as an SECM filled with electrolyte solution, used for scanning ion conductance microscopy (SICM). Thean second barrel functions an SICM probe.used (g) Double meniscus at the pipetteprobe opening that and creates electrochemical cell at theassubstrate surface, for barrel theta glass pipette, with both barrels filled with electrolyte solution, connected by a scanning electrochemical cell microscopy (SECCM). This review elaborates on the possibility of combining miniaturized biosensor platforms with high-resolution imaging techniques and methods of using nanoscale and microscale biosensors amenable to SEPM, even if their full potential is yet to be realized This includes signal transduction by ion nanogating sensors, ion channel probes, and electrochemical aptamer-based sensors. This review will cover chemical imaging using electrochemical imaging methods, offer future perspectives that could be realized with the implementation of recently developed biosensor probes in SEPM, and discuss imaging using electrode array-type platforms for spatially resolved chemical measurements in real time
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