Reversible Near‐Infrared Fluorescence Photoswitching in Aqueous Media by Diarylethene: Toward High‐Accuracy Live Optical Imaging

Abstract

over geometry or function is needed at the molecular level. For instance, DAEs have been used to switch fluorescence on and off repeatedly in bioimaging. [5][6][7][8][9][10][11][12][13][14] Unlike irreversibly switchable fluorescence probes, [15][16][17] reversible fluorescence photoswitches can enhance the spatial resolution and accuracy of signals-even for images manifesting autofluorescence signals-via their rigorously controlled photo-responsive switching between ONand OFF-states. [18][19][20][21] This can be fulfilled, in terms of molecular design, either by placing a fluorophore and a DAE moiety (or multiple copies of each) nearby in the same molecule (e.g., a dyad) [5,8,9,11,14,21,22] so that fluorescence quenching is feasible through fluorescence resonance energy transfer (FRET) [23] or by using a DAE derivative alone that can fluoresce in its closed form (Scheme S1, Supporting Information). [10,[24][25][26] Recently, the latter type of fluorescence photoswitches, in particular, based on turn-on mode sulfone derivatives of DAE, [5,[24][25][26][27][28][29][30][31][32][33][34] has been intensively investigated for super-resolution imaging [5,27,29,30,[32][33][34][35][36] in aqueous solutions. [5,27,32,33] While some nanoparticulate fluorophores such as conjugated polymers [7,9] or quantum dots [20,37] of superior brightness have been reported, the dyad-type reversible fluorescence photoswitch typically employs a conventional and potentially safer small-molecule fluorescent dye as the FRET donor with relatively high molar absorptivity (e.g., cyanine [38] ). Thus, for a given DAE derivative (FRET acceptor), the performance of fluorescence photoswitching at the intended emission wavelength, as assessed by the on-off contrast, brightness, and fatigue resistance, can be improved by pairing with a fluorophore of, conceivably, better matching optical properties-e.g., absorption and emission maxima, Stokes shift, spectral bandwidth, molar absorptivity, and quantum yield.Fluorescence imaging [16,39] has been one of the most versatile and frequently used techniques in laboratories conducting experiments related to biology and medicine. Furthermore, in the clinical setting, the usage of fluorescence probes in the operation room can provide visual guidance for tissue inspection without the need for bulky and expensive instrumentation, potentially leading to substantially improved surgical outcomes. [40][41][42][43] Despite the benefits of simplicity, low cost, and Fluorescence imaging is an indispensable tool in modern biological research, allowing simple and inexpensive color-coded visualizations of real-time events in living cells and animals, as well as of fixed states of ex vivo specimens. The accuracy of fluorescence imaging in living systems is, however, impeded by autofluorescence, light scattering, and limited penetration depth of light. Nevertheless, the clinical use of fluorescence imaging is expected to grow along with advances in imaging equipment, and will increasingly demand high-accuracy probes to avoid ...

Supramolecular Polymers with Photoswitchable Multistate Fluorescence for Anti-Counterfeiting and Encryption

“…SPCOOH and SDTE derivatives were synthesized via multistep reactions according to reported methods. , First, the host molecule CDSP was prepared via a simple esterification reaction of SPCOOH and β-CD (Scheme S1). To obtain the guest polymer P1, a one-pot free radical copolymerization was used to incorporate functional adamantane-containing monomer (BAC, Scheme S2) and photochromic fluorescent diarylethylene monomer (SDTE) with structural monomers as BA and MMA (Scheme S4).…”

Small-molecule photoswitches for fluorescence bioimaging: engineering and applications

“…24 Kim and co-workers developed dendrimers decorated with cyanine fluorophores and cross-linked with DAEs which could be internalised by living cells and zebrafish and showed 50% fluorescence quenching upon isomerisation. 25,26 Fluorescence switching using upconversion nanoparticles decorated with DAEs was also shown in C. elegans and mouse. 27,28 Recent examples demonstrated the use of photoswitchable FRET nanosystems for the specific marking of cells of interest, enabling their tracking or isolation from a sample pool.…”

Visible-light-driven bistable photoswitching with enhanced solid state NIR-fluorescence for multi-level optical storage

“…Decorating NIR-fluorescence groups on photochromic diarylethene is a common strategy to construct photoswitchable NIR fluorescent diarylethene molecules. For example, NIR fluorophores, such as porphyrins, 28 benzothiadiazole-derivative, 24 cyanine dyes, 29,30 cyanovinylene-backboned conjugated polymers, 31 transition metal 32 or lanthanide complex, 14 PdS nanocrystal, 33 terrylene diimide (TDI), 34 have been introduced in diarylethene systems recently, making great progress on NIR fluorescence photoswitching. Among them, TDI is the higher rylenediimides similar to perylene diimides (PDI), 35 which possesses outstanding optical properties, such as high fluorescence quantum yield, large molar extinction coefficient, and outstanding photostability.…”