Novel intramolecular photoinduced electron transfer-based probe for the Human Ether-a-go-go-Related Gene (hERG) potassium channel

Non-invasive hERG channel screening based on electrical impedance tomography and extracellular voltage activation (EIT-EVA)

hERG channel screening has been achieved based on electrical impedance tomography and extracellular voltage activation (EIT-EVA) to improve the non-invasive aspect of drug discovery. EIT-EVA screens hERG channels by considering the change in extracellular ion concentration which modifies the extracellular resistance in cell suspension. The rate of ion passing in cell suspension is calculated from the extracellular resistance Rex, which is obtained from the EIT measurement at a frequency of 500 kHz. In the experiment, non-invasive screening is applied by a novel integrated EIT-EVA printed circuit board (PCB) sensor to human embryonic kidney (HEK) 293 cells transfected with the human ether-a-go-go-related gene (hERG) ion channel, while the E-4031 antiarrhythmic drug is used for hERG channel inhibition. The extracellular resistance Rex of the HEK 293 cells suspension is measured by EIT as the hERG channels are activated by EVA over time. The Rex is reconstructed into extracellular conductivity distribution change Δσ to reflect the extracellular K+ ion concentration change Δc resulting from the activated hERG channel. Δc is increased rapidly during the hERG channel non-inhibition state while Δc is increased slower with increasing drug concentration cd. In order to evaluate the EIT-EVA system, the inhibitory ratio index (IR) was calculated based on the rate of Δc over time. Half-maximal inhibitory concentration (IC50) of 2.7 nM is obtained from the cd and IR dose-response relationship. The IR from EIT-EVA is compared with the results from the patch-clamp method, which gives R2 of 0.85. In conclusion, EIT-EVA is successfully applied to non-invasive hERG channel screening.

Molecular Design Strategy of Protein Isoform-Specific Fluorescent Probes by Considering Molecule in Its Entirety

Generally, different isoforms of proteins exert separate biological functions. However, due to similar structures and identical catalysis functions, distinguishing isoforms is challenging. Summarizing a molecular design strategy has great significance in developing a protein-specific fluorescent probe. Usually, recognition of a group was deemed to be the key to a protein isoform-specific response. However, some novel literature reported that fluorophore could play a vital role in the protein isoform-specific response. It means that any part of the fluorescent probe could affect the detected properties. In this work, we report the generation of the first probe to specifically recognize HexA(β-N-acetylhexosaminidase A), Hex-C4, by adjusting the length of the linker. Hex-C4 exhibits specific recognition of HexA both in vitro and in living cells. The integration of the fluorescent spectrum and the MD (molecular dynamics) results provide two factors for the molecular design of isoform-specific fluorescent probes. One is the interaction between tetraphenyl ethylene (AIE fluorogen) and amino acid residues, and the other is the interaction between amino acid residues and the binding group. In this work, a powerful tool to detect HexA in living cells is reported for the first time. Further, a workable molecular design strategy for protein isoform-specific fluorescent probes is summarized.

Astemizole Derivatives as Fluorescent Probes for hERG Potassium Channel Imaging

The detection and imaging of hERG potassium channels in living cells can provide useful information for hERG-correlation studies. Herein, three small-molecule fluorescent probes, based on the potent hERG channel inhibitor astemizole, for the imaging of hERG channels in hERG-transfected HEK293 cells (hERG-HEK293) and human colorectal cancer cells (HT-29), are described. These probes are expected to be applied in the physiological and pathological studies of hERG channels.

Environment-Sensitive Fluorescent Probe for the Human Ether-a-go-go-Related Gene Potassium Channel

A novel environment-sensitive probe S2 with turn-on switch for Human Ether-a-go-go-Related Gene (hERG) potassium channel was developed herein. After careful evaluation, this fluorescent probe showed high binding affinity with hERG potassium channel with an IC₅₀ value of 41.65 nM and can be well applied to hERG channel imaging or cellular distribution study for hERG channel blockers. Compared with other imaging techniques, such as immunofluorescence and fluorescent protein-based approaches, this method is convenient and affordable, especially since a washing procedure is not needed. Meanwhile, this environment-sensitive turn-on design strategy may provide a good example for the probe development for these targets that have no reactive or catalytic activity.