Supramolecular Room-Temperature Phosphorescent Hydrogel Based on Hexamethyl Cucurbit[5]uril for Cell Imaging

The host–guest interaction between hexamethyl
cucurbit[5]uril
(HmeQ[5]) and 1,4-diaminobenzene (DB) was investigated, and a new
low-molecular-weight supramolecular gel was prepared by a simple heating/mixing
cooling method. The structure and properties of the supramolecular
gel were characterized. Results revealed that DB molecules did not
enter the cavity of HmeQ[5] and that hydrogen bonding between the
carbonyl group at the HmeQ[5] port and the DB amino groups, together
with dipole–dipole interactions and outer wall interactions,
were the main driving forces for the formation of the supramolecular
gel. The HmeQ[5]/DB gel system exhibits temperature sensitivity. The
phosphor 6-bromo-2-naphthol (BrNp) was embedded in the gel to give
the gel fluorescent phosphorescence double emission. The double emission
ability at room temperature can be attributed to the ordered microstructure
of the supramolecular gel, which effectively avoids the nonradiative
transition of BrNp. Meanwhile, HmeQ[5]/DB-BrNp has good biocompatibility
and low biotoxicity, which is compatible with HeLa cells to achieve
cytoplasmic staining of HeLa in the red channel. The supramolecular
gels constructed by this supramolecular assembly strategy not only
have good temperature sensitivity but also extend the application
of Q[n]s in biomedical fields.