Multimodal fluorescence modulation using molecular photoswitches and upconverting nanoparticles (original) (raw)
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Reversible Fluorescence Modulation in a Dyad Comprising Phenothiazine Derivative and Spiropyran
Asian Journal of Organic Chemistry, 2018
With the objective of developing fluorescent switch molecule, we have designed, synthesized and photophysically characterized a novel fluorophore-photochrome dyad molecule comprising Phenothiazine derivative (PTCN, 4) and photochromic spiropyran (SP, 6). We successfully demonstrate that the photochromic behaviours of spiropyran unit regulate the fluorescence behaviours of phenothiazine derivative in terms of change in fluorescence intensity in PTCN-SP(8) dyad in the solution as well as in the solid state by employing steady state spectroscopic techniques. The as prepared PTCN-SP(8) is strongly fluorescent with fluorescent quantum yield more than 10% and regards as fluorescent "on" state. The spiropyran ring of photochrome (SP) opens up forming isomeric conformer, known as marocyanin (MC), upon UV irradiation in the dyad. This photogenerated isomer (MC) acts as an energy acceptor for PTCN fluorophore and energy transfer occurs from PTCN to MC via Fӧrster resonance energy transfer (FRET) mechanism which leads to quench the fluorescence of PTCN and it is assigned to fluorescent "off" state. Subsequent visible light irradiation or thermal stimulation to the dyad is accompanied by ring close isomer SP along with complete reversal of the characteristic fluorescence of the PTCN(4), fluorescent "on" state. As a result, the photoinduced reversible transformations of the photochromic component within the dyad effectively bring "on" and "off" states of the PTCN fluorescence emission. Indeed, the fluorescence of this photoswitchable dyad is modulated for several cycles with excellent fatigue resistance under optical control for both in solution and solid phases. Thus, the choice of PTCN(4) as fluorescent probe in the dyad can ultimately lead to the development of valuable photoswitchable fluorescent probe for device applications.
Ultrafast Fluorescence Photoswitch Incorporating Diketopyrrolopyrrole and Benzo[1,3]oxazine
Journal of Physical Chemistry C, 2017
With the objective of developing ultrafast fluorescent switch molecules we have designed and synthesized fluorescence switch molecules incorporating two oxazine photochromes (OX) at the two end of single diketopyrrolopyrrole (DPP) fluorophore giving the shape of the dyad molecule as OX-DPP-OX. In view to precise characterization, steady state photophysical properties, acid-base induced spectroscopic studies and ultrafast transient absorption spectroscopic studies are performed. In acetonitrile (ACN) solution, the benzo[1,3]oxazine ring of studied oxazine derivatives in OX-DPP-OX opens up and reduces the fluorescence intensity of DPP by 66% upon addition of fifty equivalent trifluoroaceticacid (CF 3 COOH, TFA) and addition of equivalent amount of base, tetrabutylammonium hydroxide ((C 4 H 9) 4 NOH, TBAOH) closes the oxazine ring reverting the fluorescence intensity of DPP unit back to its original intensity. Likewise, upon 330 nm laser excitation oxazine ring opens up in less than 135 ps in ACN solution reducing the DPP fluorescence by 90%. Both the processes, acidochromic effect and 330 nm laser excitation, generate a 3Hindolium cation, para-nitrophenolate (protonated) and para-nitrophenolate anion respectively. The photogenerated isomer lives for 1.5−1.9 ns in room temperature and reverts to its original conformer with first-order kinetics. This photochromic dyad tolerates thousands of
Rapid, Photoactivatable Turn-On Fluorescent Probes Based on an Intramolecular Photoclick Reaction
Journal of the American Chemical Society, 2011
Photoactivatable fluorescent probes are invaluable tools for the study of biological processes with high resolution in space and time. Numerous strategies have been developed in generating photoactivatable fluorescent probes, most of which rely on the photo-"uncaging" and photoisomerization reactions. To broaden photoactivation modalities, here we report a new strategy in which the fluorophore is generated in situ through an intramolecular tetrazole-alkene cycloaddition reaction ("photoclick chemistry"). By conjugating a specific microtubule-binding taxoid core to the tetrazole/alkene pre-fluorophores, robust photoactivatable fluorescent probes were obtained with fast photoactivation (~1 min) and high fluorescence turn-on ratio (up to 112fold) in acetonitrile/PBS (1:1). Highly efficient photoactivation of the taxoid-tetrazoles inside the mammalian cells was also observed under a confocal fluorescent microscope when the treated cells were exposed to either a mercury lamp light passing through a 300/395 filter or a 405 nm laser beam. Furthermore, a spatially controlled fluorescent labeling of microtubules in live CHO cells was demonstrated with a long-wavelength photoactivatable taxoid-tetrazole probe. Because of its modular design and tunability of the photoactivation efficiency and photophysical properties, this intramolecular photoclick reaction based approach should provide a versatile platform for designing photoactivatable fluorescent probes for various biological processes.
Supramolecular Strategies To Construct Biocompatible and Photoswitchable Fluorescent Assemblies
Journal of the American Chemical Society, 2011
We designed and synthesized an amphiphilic copolymer with pendant hydrophobic decyl and hydrophilic poly(ethylene glycol) chains along a common poly(methacrylate) backbone. This macromolecular construct captures hydrophobic boron dipyrromethene fluorophores and hydrophobic spiropyran photochromes and transfers mixtures of both components in aqueous environments. Within the resulting hydrophilic supramolecular assemblies, the spiropyran components retain their photochemical properties and switch reversibly to the corresponding merocyanine isomers upon ultraviolet illumination. Their photoinduced transformations activate intermolecular electron and energy transfer pathways, which culminate in the quenching of the boron dipyrromethene fluorescence. As a result, the emission intensity of these supramolecular constructs can be modulated in aqueous environments under optical control. Furthermore, the macromolecular envelope around the fluorescent and photochromic components can cross the membrane of Chinese hamster ovarian cells and transport its cargo unaffected into the cytosol. Indeed, the fluorescence of these supramolecular constructs can be modulated also intracellularly by operating the photochromic component with optical inputs. In addition, cytotoxicity tests demonstrate that these supramolecular assemblies and the illumination conditions required for their operation have essentially no influence on cell viability. Thus, supramolecular events can be invoked to construct fluorescent and photoswitchable systems from separate components, while imposing aqueous solubility and biocompatibility on the resulting assemblies. In principle, this simple protocol can evolve into a general strategy to deliver and operate intracellularly functional molecular components under optical control.
The use of upconverting nanoparticles to drive organic photoreactions
One of the primary disadvantages of organic photochemistry is the need for high-energy UV light, light that has many detrimental qualities. A viable solution to this problem is the use of upconverting nanoparticles (UCNP) that can locally convert near infrared (NIR) laser light into UV light or visible light of sufficient energy to drive organic photoreactions.
With the objective of developing near-infrared fluorescence switch molecules for potential applications, synthesis of new dyad with two methyl 3-(3',3'-dimethyl-6-nitrospiro[chromene-2,2'-indolin]-1'-yl)propanoate (6), spiropyran (SP), units as the photochromic acceptors and a near-infrared fluorescence probe, (E)-4-((1-(2-hydroxyethyl)-3,3-dimethyl-3H-indol-1ium-2-yl)methylene)-2-((E)-(1-(2-hydroxyethyl)-3,3-dimethylindolin-2-ylidene)methyl)-3-oxocyclobut-1-en-1-olate (SQ), (3) as fluorescent donor are described. Two SP units are attached to the two indole nitrogen of squarine core with almost no conjugation with the SQ unit. The spectroscopic properties of the newly synthesized dyad, SP-SQ-SP (7), and corresponding model compounds (SP, SQ) have been studied in acetonitrile solution, poly(ethylene glycol) (PEG) polymer matrices and in nanoparticle form dispersed in aqueous medium. These dyes (3 and 7) exhibited absorption in the range 550-670 nm, with significant absorption coefficients (10-5 M-1 cm-1) in the ACN. The fluorescence emission spectra of these dyes cover very broad range from 630 to 750 nm and fluorescence quantum yields are of the order of 0.2 in ACN solution. External stimulations (ultraviolet light and visible light) generate reversible changes in the structure of 7, resulting in changes in the absorption specta due to the presence of the two spiropyran units. The absorption spectrum of the MC, a ring open form of SP, in dyad SP-SQ-SP (7) has large spectral overlap with the fluorescence spectrum of the SQ unit. Thus, the fluorescence intensity of dyad 7 is modulated by reversible conversion among the two states of the photochromic spiropyran units and the fluorescence resonance energy transfer (FRET) between the MC form and the SQ unit. Highcontrast "on/off" fluorescence switching is successfully achieved with remarkably fatigue resistance in solution, in polymer film and in nanoparticle form of dyad (7). The described results indicate that this system may represent an efficient fluorescent switch molecule in potentially rewritable high-density optical data or image storage utilizing near-infrared luminescence intensity readout schemes.
Journal of Materials Chemistry C, 2018
The development of single-molecule imaging and super-resolution microscopic tequniques has promoted the study of fluorescence switchable molecules that have been important for the in-depth understanding of activities of organelles and geometries of materials in nano-and microscales. The utilization of photochromic compounds as the photo-switching trigger is one of the efficient strategies to reversibly control the fluorescent "ON" and "OFF" states. In this study, we demonstrated the red-color fluorescence switching of a perylene bisimide (PBI) derivative by using the fast photochromic [2.2]paracyclophanebridged imidazole dimer. The transient colored biradical species as the fluorescence quencher is generated upon UV light irradiation. Because the biradical species has broad absorption bands in the whole visible light and the near-infrared regions (500-900 nm), the fluorescence of PBI could be efficiently quenched by Förster resonance energy transfer (FRET). The fluorescence intensity was switched by the fast photochromic cycles within a few tens of milliseconds. The potential capability of the transient biradical species to switch the fluorescence in the visible and NIR regions will open up the multicolor fluorescence imaging.