Electrochemiluminescence-Based Capacitance Microscopy for Label-Free Imaging of Antigens on the Cellular Plasma Membrane

Abstract

Electrochemiluminescence (ECL)-based capacitance microscopy using a square-wave voltage is established unprecedentedly to realize the label-free visualization of species on electrode surfaces and cellular plasma membranes. The drop in the local capacitance upon the binding of species to the surface or to a cellular membrane is derived to induce a relatively larger potential drop (V dl) across the double layer on the local electrode surface, which is utilized to prompt enhanced ECL at the binding position. The square-wave voltage with a frequency of as high as 1.5 kHz is proven to be favorable for the discrimination of the local ECL from the surrounding signal. Using this new detection principle and resultant capacitance microscopy, carcinoembryonic antigens (CEA) at amounts of as low as 1 pg can be visualized. Further application of this approach permits the direct imaging of CEA antigens on single MCF-7 cells through the capacitance change after the formation of the antigen–antibody complex. Successful visualization of the analyte without any ECL tag will allow not only special capacitance microscopy for label-free bioassays but also a novel ECL detection approach for the sensitive detection of biomolecules.

Spatially resolved electrochemiluminescence through a chemical lens

“…It provides high ECL efficiency in heterogeneous as well as homogeneous formats and it is the most widely exploited ECL system to detect various biomolecules (e.g., proteins, peptides, ligands and oligonucleotides) and DNA, for immunological assays and ECL microscopy. [11][12][13][14][15][16][17][18][19][20][21][22] The heterogeneous ECL mechanism of the [Ru(bpy) 3 ] 2+ /TPrA system is an active area of investigation. 14,32,33,43,44 In such a conguration, the ECL luminophore is not free to diffuse and cannot be directly oxidised at the electrode.…”

“…[15][16][17] Different approaches have also been proposed to image cells by ECLM. 12,13,[18][19][20][21][22] Furthermore, the surface-conned emission allows ECLM to quantify different analytes simultaneously [23][24][25][26] as well as permitting high resolution visualization of nanomaterials such as nanoparticles and nanorods. [27][28][29][30][31] In ECL, the emission layer is typically conned in the near proximity of the electrode surface 32 and it is limited by the lifetime of the coreactant radicals (vide infra) and cannot be easily controlled.…”

Electrochemiluminescence Single‐Cell Analysis: Intensity‐ and Imaging‐Based Methods

“…Zhang et al reported the ECL-based capacitance microscopy for the first time. [68] In their work, a square wave voltage with high frequency was applied to the electrode while recording the ECL image. Upon the binding of nonconductive antibody (without ECL tags), the local capacitance decreases, which results in a higher potential drop across the double layer (V dl ) in these regions.…”

“…As depicted in Figure 8a, cell-matrix adhesions are exactly in this space. Ru (bpy) 3 2 + generates bright emission at the bare surface, whereas cell-matrix adhesions function as inhibitors and steric exclusion [68] with permission from the American Chemical Society. sites of ECL reaction and thus appear as dark shadows under ECL microscopy.…”

Influence of Cholesterol on the Orientation of the Farnesylated GTP-bound KRas-4B Binding with Anionic Model Membranes

“…Plasma membrane (PM) systems have been extensively studied over several decades [1][2][3][4][5] on their association with proteins. Recent studies have shown that the role of proteins and their interactions with components of PM is extremely important to understand the mechanisms of protein anchoring into the membrane that can lead to oncogenesis [6].…”