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Cucurbit[7]uril-Tetramethylrhodamine Conjugate for Direct Sensing and Cellular Imaging
Andrew T Bockus, Lauren C Smith, Amy G Grice
1Department of Chemistry and Biochemistry, University of Maryland , College Park, Maryland 20742, United States.
Journal of the American Chemical Society
|December 22, 2016
Summary
A new fluorescent sensor, cucurbit[7]uril-tetramethylrhodamine (Q7R), was synthesized. It accurately detects analytes by reporting guest binding without altering host affinity, enabling sensitive molecular sensing.
Area of Science:
- Supramolecular Chemistry
- Chemical Biology
- Materials Science
Background:
- Synthetic host molecules like cucurbiturils (Q7) are valuable for molecular recognition.
- Developing responsive sensors that report analyte binding without perturbing host properties is a key challenge.
Purpose of the Study:
- To design and synthesize a fluorescent conjugate of cucurbit[7]uril (Q7) and tetramethylrhodamine (TMR), named Q7R.
- To characterize Q7R's optical properties, guest-binding behavior, and cellular uptake.
- To establish Q7R as a sensitive, single-component sensor for guest binding and cellular imaging.
Main Methods:
- Two-step synthesis of Q7R from azidobutyl-Q7 and NHS-activated TMR.
- Fluorescence quenching assays to determine equilibrium dissociation constants (Kd).
- Confocal fluorescence microscopy for cellular uptake and localization studies in HT22 neurons.
Main Results:
- Q7R was successfully synthesized and characterized.
- Guest binding to Q7R resulted in fluorescence quenching, enabling Kd determination.
- Q7R exhibited Kd values identical to unmodified Q7, demonstrating no perturbation of binding affinity.
- Q7R showed sensitive detection of guests across 3 orders of magnitude and at low nanomolar concentrations.
- Q7R was efficiently taken up by HT22 neurons, localized in the cytoplasm, and showed no cytotoxicity.
Conclusions:
- Q7R serves as a direct, single-component host-indicator conjugate for sensitive analyte detection.
- The design strategy is generalizable for creating other host-indicator systems.
- Q7R is a promising cell-permeable fluorescent probe for imaging and sensing applications in biological systems.
