We show how the macrocyclic host cucurbit[8]uril (CB[8]) and a fluorescent dye form a biosensing ensemble while its cavity simultaneously traps tryptophan, the upstream substrate of IDO1 enzymes, therefore providing a label-free method to monitor the activity of IDO1 in real time. Incubation of malignant HeLa and HepG2 cells overexpressing IDO1 with the associative biosensor resulted in its spontaneous uptake and a fluorescence switch-on response in situ, which can be traced to the displacement of tryptophan from CB[8] upon IDO1-catalyzed oxidation. The results, for the first time, establish a supramolecular sensing concept for the detection of intracellular enzymatic activity in live cells, thus allowing direct cell-based analysis and inhibitor screening compatible with commercial instruments including microplate reader, fluorescent microscopy, and flow cytometry.
Keyphrases
- label free
- cell cycle arrest
- induced apoptosis
- flow cytometry
- cell death
- hydrogen peroxide
- quantum dots
- endoplasmic reticulum stress
- single cell
- stem cells
- single molecule
- cell therapy
- signaling pathway
- oxidative stress
- high resolution
- energy transfer
- endothelial cells
- diabetic rats
- gold nanoparticles
- deep learning
- bone marrow
- mass spectrometry
- high throughput
- living cells
- sensitive detection