Aggregation-Enabled Electrochemistry in Confined Nanopore Capable of Complementary Faradaic and Non-Faradaic Detection.

Electrochemistry that empowers innovative nanoscopic analysis has long been pursued. Here, the concept of aggregation-enabled electrochemistry (AEE) in a confined nanopore is proposed and devised by reactive oxygen species (ROS)-responsive aggregation of CdS quantum dots (QDs) within a functional nanopipette. Complementary Faradaic and non-Faradaic operations of the CdS QDs aggregate could be conducted to simultaneously induce the signal-on of the photocurrents and the signal-off of the ionic signals. Such a rationale permits the cross-checking of the mutually corroborated signals and thus delivers more reliable results for single-cell ROS analysis. Combined with the rich biomatter-light interplay, the concept of AEE can be extended to other stimuli-responsive aggregations for electrochemical innovations.

Electrochemical Immunoassay of Endothelin-1 Based on a Fenton-Type Reaction Using Cu(II)-Containing Nanocomposites as Nanozymes.

Endothelin-1 (ET-1) is a powerful endogenous vasoconstrictor and it is closely related to the pathogenesis of endothelial dysfunction that is commonly involved in the initiation of vascular inflammation and in the development of vascular diseases. A new method for the electrochemical immunoassay of ET-1 was put forward in this work. ET-1 antibodies (Ab), gold nanoparticles (GNPs), and copper ions were employed to synthesize nanoenzyme-labeled antibodies, Ab-GNPs-Cu(II) nanocomposites, and the latter was evaluated using transmission electron microscopy, dynamic light scattering, UV-vis absorption spectrophotometry, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. These nanocomposites could be captured on a glassy carbon electrode (GCE) modified with poly(thionine) (PTH) and ET-1, GCE/PTH/ET-1. The immobilized nanoenzymes, GNPs-Cu(II) nanoparticles, played a peroxidase mimic role. Hydroxyl radicals, •OH, generated by a Fenton-type reaction, oxidized PTH and induced the considerable cathodic current on an assembled sandwich-type electrode. Owing to the competitive immunoreaction, ET-1 in the solution inhibited the capture of Ab-GNPs-Cu(II) nanocomposites. The deficiency of •OH caused the decline of the electrochemical response. The cathodic current change was in proportion to the ET-1 concentration from 0.5 to 500 ng mL-1. Cell morphology and viability investigations show that human umbilical vein endothelial cells, HUVECs, suffered from dysfunction when they were incubated in the presence of high-concentration glucose. Analyses on the growth medium using the developed method reveal that ET-1 was secreted by the injured cells and the release level of ET-1 was associated positively with the glucose concentration in the growth medium.