Abstract
Dual-emissive systems showing color-specific photoswitching are promising in bioimaging and super-resolution microscopy. However, their switching efficiency has been limited because a delicate manipulation of all the energy transfer crosstalks in the systems is unfeasible. Here, we report a perfect color-specific photoswitching, which is rationally designed by combining the complete off-to-on fluorescence switching capability of a fluorescent photochromic diarylethene and the frustrated energy transfer to the other fluorescent dye based on the excited-state intramolecular proton transfer (ESIPT) process. Upon alternation of UV and visible light irradiations, the system achieves 100% switching on/off of blue emission from the diarylethene while orange emission from the ESIPT dye is unchanged in the polymer film. By fabricating this system into biocompatible polymer nanoparticles, we demonstrate microscopic imaging of RAW264.7 macrophage cells with reversible blue-color specific fluorescence switching that enables super-resolution imaging with a resolution of 70 nm.
Highlights
Dual-emissive systems showing color-specific photoswitching are promising in bioimaging and super-resolution microscopy
Light is absorbed by the ground-state enol form (E → E*), but the fluorescence is emitted by the excited-state keto form (K* → K), which features an abnormally large Stokes shift with no overlap between its absorption and emission spectra
The absorption band of orange-fluorescent HPNIC is confined within UV-light region, which is in sharp contrast to visible absorption bands of other common orange-fluorescent dyes
Summary
Dual-emissive systems showing color-specific photoswitching are promising in bioimaging and super-resolution microscopy. Photoswitchable nanoparticles, whose fluorescence emission can be turned on/off reversibly by light irradiations, have attracted great attention because of their potential in fluorescence imaging[1,2,3,4,5,6,7] They can selectively highlight bio-systems by eliminating autofluorescence, and allow for super-resolution microscopy such as PALM (photoactivation localization microscopy), STORM (stochastic optical reconstruction microscopy), and RESOLFT (reversible saturable optical linear fluorescence transitions)[8,9,10,11,12,13,14,15,16], whose fundamental principles rely on optical switching[17,18,19,20]. Jovin et al suggested using separate excitation sources to readout individual fluorescence signals from quantum dot nanoparticles[42] Both the dual-emissive systems achieved selective single-color photoswitching by blocking the interfluorophore energy transfer, the efficiencies of switching on/. Off by diarylethenes, one of the most commonly used photochromic dyes[43,44], were compromised (80 and 50%, respectively) with other problems, such as the limitation of nanoparticle size control, complex fabrication process, and additional cost for special readout instruments
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