Kim D, Aktalay A, Jensen N, Uno K, Bossi ML, Belov VN, Hell SW. Supramolecular Complex of Photochromic Diarylethene and Cucurbit[7]uril: Fluorescent Photoswitching System for Biolabeling and Imaging.
J Am Chem Soc 2022;
144:14235-14247. [PMID:
35895999 PMCID:
PMC9376957 DOI:
10.1021/jacs.2c05036]
[Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
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Photoswitchable fluorophores—proteins and synthetic
dyes—whose
emission is reversibly switched on and off upon illumination, are
powerful probes for bioimaging, protein tracking, and super-resolution
microscopy. Compared to proteins, synthetic dyes are smaller and brighter,
but their photostability and the number of achievable switching cycles
in aqueous solutions are lower. Inspired by the robust photoswitching
system of natural proteins, we designed a supramolecular system based
on a fluorescent diarylethene (DAE) and cucurbit[7]uril
(CB7) (denoted as DAE@CB7). In this assembly, the photoswitchable DAE molecule is encapsulated by CB7 according to the host–guest
principle, so that DAE is protected from the environment
and its fluorescence brightness and fatigue resistance in pure water
improved. The fluorescence quantum yield (Φfl) increased
from 0.40 to 0.63 upon CB7 complexation. The photoswitching of the DAE@CB7 complex, upon alternating UV and visible light irradiations,
can be repeated 2560 times in aqueous solution before half-bleaching
occurs (comparable to fatigue resistance of the reversibly photoswitchable
proteins), while free DAE can be switched on and off
only 80 times. By incorporation of reactive groups [maleimide and N-hydroxysuccinimidyl (NHS) ester], we prepared bioconjugates
of DAE@CB7 with antibodies and demonstrated both specific
labeling of intracellular proteins in cells and the reversible on/off
switching of the probes in cellular environments under irradiations
with 355 nm/485 nm light. The bright emission and robust photoswitching
of DAE-Male3@CB7 and DAE-NHS@CB7 complexes
(without exclusion of air oxygen and addition of any stabilizing/antifading
reagents) enabled confocal and super-resolution RESOLFT (reversible
saturable optical fluorescence transitions) imaging with apparent
70–90 nm optical resolution.
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