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With reduced background and high sensitivity, photoelectrochemistry (PEC) may be applied as an intracellular nanotool and open a new technological direction of single‐cell study. Nevertheless, the present palette of single‐cell tools lacks such a PEC‐oriented solution. Here a dual‐functional photocathodic single‐cell nanotool capable of direct electroosmotic intracellular drug delivery and evaluation of oxidative stress is devised by engineering a target‐specific organic molecule/NiO/Ni film at the tip of a nanopipette. Specifically, the organic molecule probe serves simultaneously as the biorecognition element and sensitizer to synergize with p‐type NiO. Upon intracellular delivery at picoliter level, the oxidative stress effect will cause structural change of the organic probe, switching its optical absorption and altering the cathodic response. This work has revealed the potential of PEC single‐cell nanotool and extended the boundary of current single‐cell electroanalysis. [ABSTRACT FROM AUTHOR]

Single nanoparticle collision (SNC) technology has attracted increasing attention to explore single nanoparticle electrochemistry. By improving the temporal resolution of electrochemical recording, several recent studies have uncovered the intermittent electron transfer processes during the SNC of single silver nanoparticles. The electrode current curve displayed multiple current peaks that were completely separated, instead of a single peak. In the present work, we employed surface plasmon resonance microscopy to monitor the collision and oxidation processes of single silver nanoparticles. Simultaneous optical and electrochemical recordings provided comprehensive capability to correlate the physical movement of nanoparticles (from optical signal) and the electron transfer activity (from electrochemical signal). While previous studies hypothesized the physical detachment of nanoparticles from the electrode due to electrostatic repulsion or Brownian motion, the optical imaging revealed that nanoparticles often remained in physical touch with the electrode even though no electron transfer was occurring. These results demonstrated that the electrical contact between nanoparticle and electrode, which could be rather stochastic due to thermal motion and micro‐convection, played critical roles in regulating the multi‐peak behavior of single silver nanoparticles. In touch: surface plasmon resonance microscopy is utilized to monitor collision and oxidation processes of single silver nanoparticles. Simultaneous optical and electrochemical recordings reveal that nanoparticles often remain in physical touch with the electrode even though no electron transfer is occurring. The electrical contact plays critical roles in regulating the multi‐peak behavior of single silver nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Ionic current rectification (ICR) based nanopipettes allow accurate monitoring of cellular behavior in single living cells. Herein, we proposed a 30 nm nanopipette functionalized with G‐quadruplex DNAzyme as an efficient biomimetic recognizer for ROS generation at subcellular level via the changes of current–voltage relationship. Taking advantages of the ultra‐small tip, the nanopipette could penetrate into a single living cell repeatedly or keep measuring for a long time without compromising the cellular functions. Coupled with precision nanopositioning system, generation of ROS in mitochondria in response to cell inflammation was determined with high spatial resolution. Meanwhile, the changes of aerobic metabolism in different cell lines under drug‐induced oxidative stress were monitored continuously. We believe that the ICR‐nanopipette could be developed as a powerful approach for the study of cellular activities via electrochemical imaging in living cells. [ABSTRACT FROM AUTHOR]

The evolution of photoelectrochemical (PEC) bioanalysis has resulted in substantial progress in its analytical performance and biodetection applications. The aim of this review is to provide a panoramic snapshot of the state of the art in this dynamically developing field, with special emphasis on PEC DNA analysis, immunoassay, enzymatic biosensing and cell-related detection. The future prospects in this area are also evaluated and discussed. This work will serve as a useful source to inform the interested audience of the latest developments and applications in the field of PEC bioanalysis. [ABSTRACT FROM AUTHOR]

Single-cell analysis (SCA) could provide in-depth understanding of cell biology yet is of great challenge. Many attempts have been made to develop novel techniques for SCA. Nanopipette-based ion current rectification (ICR) electroanalysis represents an emerging methodology to combat in this arena. In this review, the working rationale of ICR and its key regulation factors are discussed, followed by the sensing strategies established for SCA using illustrative examples. Future perspectives in this field are also proposed. • Ion current rectification (ICR)-nanopipette technique for single-cell analysis (SCA) is reviewed. • The fundamentals, operation rationales, and the state of the art are discussed. • Trends and prospects of this field are presented. [ABSTRACT FROM AUTHOR]

Conformational fluctuations play a central role in the electron transfer reactions of molecules. Because the fluctuations can be extremely fast in kinetics and small in amplitude, a technique with fast temporal resolution and high conformational sensitivity is needed to follow the transient electron transfer processes. Here we report on an electrochemically controlled plasmonic detection technique capable of monitoring conformational changes in redox molecules with ns response time. Using the technique, we study the electron transfer reaction and the associated conformational gating of a redox protein (cytochrome c). The study reveals that the conformational gating takes place over a broad range of time scales, from microsecond to millisecond. [ABSTRACT FROM AUTHOR]