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1.
Bovine serum albumin (BSA)–squaraine supramolecular adducts with aggregation‐induced emission (AIE) properties were prepared and characterized by spectroscopic methods. While squaraine dyes showed a very low fluorescence quantum yield in water, a great enhancement in the fluorescence of the aggregated BSA adducts was achieved due to the abnormal aggregation‐induced emission properties of squaraines. The adducts formation was studied from a kinetic point of view showing unexpected structure–properties relationships. 相似文献
2.
Pseudorotaxane complexes of squaraine dyes and tetralactam macrocycles are converted into permanently interlocked rotaxane structures using copper-catalyzed and copper-free cycloaddition reactions with bulky stopper groups. The photophysical properties of the encapsulated squaraine depend on the structure of the macrocycle. In one case, squaraine rotaxanes are produced in near-quantitative yields and with intense near-IR fluorescence. In another case, squaraine fluorescence is greatly diminished upon macrocyclic encapsulation but the signal can be restored by dye displacement with anions. 相似文献
3.
With the objective of developing near-infrared fluorescence probes for biological applications, a few squaraine dyes 3a-d, containing amphiphilic substituents, were synthesized and their photophysical properties have been investigated in the presence and absence of the organized media. These dyes exhibited absorption in the range 630-650 nm, with significant absorption coefficients (epsilon = 1-3 x 10(5) M(-1) cm(-1)) in the aqueous medium. The fluorescence spectra of these dyes showed emission maximum from 660 to 675 nm, depending on the nature of substituents. The fluorescence quantum yields were in the range from 0.15 to 0.21 in ethanol, but 10 times lower values were observed (phi(f) = 0.01-0.02) in the aqueous medium. In the presence of micelles such as cetyltrimethylammonium bromide, sodium dodecyl sulfate, and Triton X-100, these dyes showed negligible changes in their absorption properties, whereas a significant enhancement (5-10-folds) in their fluorescence yields was observed. Picosecond time-resolved studies indicated that these dyes show single-exponential decay in ethanol and ethanol-water mixtures; however, they exhibit biexponential decay with longer lifetimes in the presence of the micellar media. The results indicate that these novel amphiphilic squaraine dyes 3a-d, which exhibit favorable photophysical properties, good solubility in the aqueous medium, and interact efficiently with micelles, can have potential biological applications as near-infrared fluorescence sensors. 相似文献
4.
Water-soluble near-infrared (NIR) fluorescent labeling probes, named KSQ-3 and -4, which are based on a squaraine backbone, were synthesized and applied to biological labeling. The presented results demonstrate that the large, planar and hydrophobic squaraine dye becomes fully soluble in aqueous solution by the introduction of several sulfo group terminated alkyl substituents. Especially KSQ-4, which is substituted with four sulfo groups, exhibited perfect water solubility and significant fluorescence emission at the NIR region (817 nm) in the presence of bovine serum albumin (BSA). BSA was covalently labeled with KSQ-4, and the conjugate showed a strong absorption peak at 787 nm, which indicates compatibility with commercially available NIR laser diodes used for exciting the fluorophore. Furthermore, strong fluorescence emission was observed at 812 nm (phi = 0.08). 相似文献
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Dr. Pichandi Ashokkumar Dr. Mayeul Collot Dr. Andrey S. Klymchenko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(22):6795-6803
To overcome the limited brightness of existing fluorogenic molecular probes for biomolecular targets, we introduce a concept of fluorogenic dendrimer probe, which undergoes polarity-dependent switching due to intramolecular aggregation-caused quenching of its fluorophores. Based on a rational design of dendrimers with four and eight squaraine dyes, we found that octamer bearing dyes through a sufficiently long PEG(8) linker displays >400-fold fluorescence enhancement from water to non-polar dioxane. High extinction coefficient (≈2,300,000 m −1 cm−1) resulted from eight squaraine dyes and quantum yield (≈25 %) make this octamer the brightest environment-sensitive fluorogenic molecule reported to date. Its conjugate with cyclic RGD used at low concentration (3 nm ) enables integrin-specific fluorescence imaging of cancer cells with high signal-to-background ratio. The developed dendrimer probe is a “golden middle” between molecular probes and nanoparticles, combining small size, turn-on response and high brightness, important for bioimaging. 相似文献
7.
Cosmin Butnarasu Carlotta Pontremoli Maria Jesus Moran Plata Nadia Barbero Sonja Visentin 《Photochemistry and photobiology》2023,99(2):562-569
Mucins are a family of long polymeric glycoproteins which can be overexpressed in several types of cancers, and over recent years, great attention was addressed to identify mucins as an important biomarker of adverse prognosis. Fluorometric detection mediated by fluorescent probes could represent a winning strategy in the early diagnosis of different pathologies. Among promising biological fluorescent probes, squaraines are gaining particular attention, thanks to their sharp and intense absorption and emission in the NIR region. In this contribution, three squaraine dyes bearing different substituents and with different lipophilicity have been investigated for their ability to detect mucin. The turn-on response upon the addition of mucin has been investigated by means of absorbance and fluorescence spectroscopy. After a preliminary screening, the squaraine (S6) bearing bromine as a substituent and C4 aliphatic chains showed the highest fluorescence turn-on and highest affinity for mucin than albumin. To further highlight the selectivity of S6 for mucin, the fluorescence response has been evaluated in the presence of serum and site-specific proteins different than albumin. Absorption spectroscopy was used to characterize the binding mechanism of squaraine to mucin. 相似文献
8.
Kulathinte M. Shafeekh Mohanannair S. Soumya Moochikkadavath A. Rahim Annie Abraham Suresh Das 《Photochemistry and photobiology》2014,90(3):585-595
Here, we report the synthesis, photophysical properties and photodynamic effects in DLA live cells of three water soluble squaraine dyes, viz. bisbenzothiazolium squaraine dyes SQMI and SQDI with iodine in one and both benzothiazolium units, respectively, and an unsymmetrical squaraine dye ASQI containing iodinated benzothiazolium and aniline substituents. The diiodinated SQDI showed an anomalous trend in both fluorescence and triplet quantum yields over the monoiodinated SQMI, with SQDI showing higher fluorescence and lower triplet quantum yields compared to SQMI. Nanosecond laser flash photolysis of SQDI and SQMI indicated the formation of triplet excited states with quantum yield of 0.19 and 0.26, respectively. On photoirradiation, both the SQDI and SQMI generate singlet oxygen and it was observed that both dyes undergoing oxidation reactions with the singlet oxygen generated. ASQI which exhibited a lower triplet quantum yield of 0.06 was, however, stable and did not react with the singlet oxygen generated. In vitro cytotoxicity studies of these dyes in DLA live cells were performed using Trypan blue dye exclusion method and it reflect an order of cytotoxicity of SQDI>SQMI>ASQI. Intracellular generation of the ROS was confirmed by dichlorofluorescein assay after the in vitro PDT. 相似文献
9.
Wenhai Wang Afu Fu Jingbo Lan Prof. Dr. Ge Gao Prof. Dr. Jingsong You Prof. Dr. Lijuan Chen Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(17):5129-5137
We herein present an effective strategy to create water‐soluble fluorescent bioimaging dyes by introducing the imidazolium‐based ionic liquid (IL) pendants into a fluorescent skeleton. A new type of water‐soluble imidazolium‐anchored squaraine dye was synthesized accordingly. The relationship between the aggregate of squaraines and their fluorescent cell imaging application was elucidated in detail. Firstly, the aggregation behavior of squaraines in water solutions could be suppressed by varying the alkyl chain attached to the imidazolium unit. Secondly, the capability of cellular uptake and staining of dyes was also dramatically enhanced upon increasing the length of the paraffinic chain. These squaraine dyes displayed an excellent photostability that could permit real‐time fluorescence bioimaging experiments to be monitored over a long time period with constant sample irradiation. Additionally, we designed for the first time an FeII‐ion probe on the basis of an attack of the hydroxyl radical to the four‐membered ring of squaraine. The results demonstrated that the imidazolium‐anchored squaraines could perform “naked‐eye” detection of the Fe2+ ion over a wide range of other interfering metals in aqueous media. More surprisingly, this process showed a fluorescence “turn‐off” and “‐on” response through the regeneration of squaraines in cells. 相似文献
10.
Two novel water‐soluble indocyanine dyes were synthesized. Their chemical structures were confirmed by 1H NMR, IR, MS and UV‐vis techniques. The absorptions of the prepared dyes in different solvents were measured. Two dyes exhibited negative solvatochromism, with a blue shift of the absorption and an emission maximum in (bovine serum albumin) protonic solvent relative to non protonic solvent. The fluorescence properties of the dyes in both free state and BSA were investigated. Significant enhancement of the fluorescence intensity for the Dye2 was observed in the presence of BSA. Dye2 could be proposed as fluorescent dyes for BSA detection in aqueous solution. 相似文献
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Danaboyina Ramaiah Abraham Joy Nese Chandrasekhar Nadukkudy V. Eldho Suresh Das Manapurathu V. George 《Photochemistry and photobiology》1997,65(5):783-790
Abstract— We describe the synthesis and photophysical studies, including measurements of quantum yields of triplet excited states and singlet oxygen generation of bis(3,5-dibromo-2,4,6-trihydroxyphenyl)squaraine (2) and bis(3,5-diiodo-2,4,6-trihydroxyphenyl)squaraine (3). These dyes exist in solution in the protonated, neutral, single and double depro-tonated forms, depending on pH. The pKa values of these dyes were found to be relatively lower than those of the parent bis(2,4,6-trihydroxyphenyl)squaraine (1). Only the single deprotonated forms (Sq) of 2 and 3 showed measurable fluorescence. In microheterogeneous media such as in the presence of β-cyclodextrin, cetyltrunethylammonium bromide and polyvinylpyrrolidone), bathochromic shifts in the absorption and emission spectra of Sq were observed with a substantial enhancement in their fluorescence yields. Triplet excited states are the main transient intermediates obtained upon 532 nm laser excitation of the various forms of 2 and 3 in methanol. These triplets have lifetimes in the range from 0.061 to 132 μs. The triplet quantum yields of double deprotonated forms are low (φT = <0.01), whereas the neutral and Sq?forms of 2 (φr = 0.12 and 0.22) and 3 (φT= 0.24 and 0.5), respectively, exhibited significant triplet yields. Quantum yields of singlet oxygen generation by Sq?forms of 2 and 3 were determined in methanol and were found to be 0.13 and 0.47, respectively, which are in good agreement with the triplet yields obtained in these systems. 相似文献
12.
Alex S Basheer MC Arun KT Ramaiah D Das S 《The journal of physical chemistry. A》2007,111(17):3226-3230
The squaraine dye bis(2,4,6-trihydroxyphenyl)squaraine (SqH) was earlier reported to form J-type dimer aggregates in acetonitrile solutions at higher concentrations. Subsequent studies have suggested that concentration-dependent changes in the absorption spectrum of SqH in acetonitrile could be attributed to shifts in the acid-base equilibrium due to the presence of water as an impurity. In this work, we describe our studies on the effect of varying acid and dye concentration on the absorption spectra of the bromo and iodo substituted dyes, bis(3,5-dibromo-2,4,6-trihydroxyphenyl)squaraine (SqBr) and bis(3,5-diiodo-2,4,6-trihydroxyphenyl)squaraine (SqI). Analysis of the changes in the absorption spectra as a function of dye concentration and the nature of the solvent composition confirmed the formation of J-type dimer aggregates in aprotic solvents in this class of dyes. Further confirmation for the formation of the J-type dimer aggregates could be obtained by comparing the differences in the triplet excited state properties of the neutral and aggregated forms of the dyes using time-resolved spectroscopy. 相似文献
13.
A novel class of dialkylanthracene containing squaraine dyes (Sq1-3) possessing intense absorption and emission in the NIR region has been synthesized. Structural and electronic features investigated using DFT methods suggest that the significant bathochromic shifts observed on replacing dialkylaniline by dialkylanthracene in this class of molecules can be attributed to a reduction in the HOMO-LUMO gap mainly due to enhanced hydrogen bonding between the carbonyl group of the cyclobutane ring and the neighboring aromatic hydrogen in the dyes containing the anthracene moiety. The absence of fluorescence in aqueous media and high fluorescence when encapsulated into hydrophobic domains make this class of dyes especially useful as probes for mapping such domains in biological systems. 相似文献
14.
Deing KC Mayerhöffer U Würthner F Meerholz K 《Physical chemistry chemical physics : PCCP》2012,14(23):8328-8334
In this study, we investigated bulk-heterojunction solar cells composed of PC(61)BM and squaraine dyes with different donor subunits. Both, H- and J-aggregates, have been observed for the squaraine dyes in the mixture, even for the same dye depending on the annealing conditions of the blends. Supramolecular organization of the squaraine dyes noticeably affects solar cell performance. The J-aggregate exhibits a red-shift of the absorption maximum that results in a significant increase in the short-circuit current and decrease in the open-circuit voltage compared to the as-cast device. The H-aggregate shows a blue-shift in the absorption maximum and concomitantly only a moderate increase in the short-circuit current as well as an increase in the open-circuit voltage. The course of domain growth during annealing was monitored by local photocurrent mapping. 相似文献
15.
Chun-Lin Sun Qing Liao Ting Li Jun Li Jian-Qiao Jiang Zhen-Zhen Xu Xue-Dong Wang Rong Shen De-Cheng Bai Qiang Wang Sheng-Xiang Zhang Hong-Bing Fu Hao-Li Zhang 《Chemical science》2015,6(1):761-769
Small organic dyes with large two-photon absorption (TPA) cross sections (δ) are more desirable in many applications compared with large molecules. Herein, we proposed a facile theoretical method for the fast screening of small organic molecules as potential TPA dyes. This method is based on a theoretical analysis to the natural transition orbitals (NTOs) directly associated with the TPA transition. Experimental results on the small indolic squaraine dyes (ISD) confirmed that their TPA cross sections is strongly correlated to the delocalization degree of the NTOs of the S2 excited states. Aided by this simple and intuitive method, we have successfully designed and synthesized a small indolic squaraine dye (ISD) with a remarkable δ value above 8000 GM at 780 nm. The ISD dye also exhibits a high singlet oxygen generation quantum yield about 0.90. The rationally designed TPA dye was successfully applied in both two-photon excited fluorescence cell imaging and in vivo cerebrovascular blood fluid tracing. 相似文献
16.
The design and development of novel squaraine dyes as sensitisers for photodynamic therapy (PDT) applications has grown tremendously in the last decade from the time when a squaraine dye was proposed to be a potential candidate, to-date when the use of such dyes have been demonstrated in animal models for skin cancer. This perspective article highlights the basic design, tuning of absorption, triplet excited state and two-photon absorption properties and recent developments of the squaraines as PDT sensitisers. 相似文献
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[reaction: see text] Synthesis of new quinaldine-based squaraine dyes linked to cellular recognition elements that exhibit near-infrared absorption (>740 nm) are described. Both product analysis and theoretical calculations substantiate the interesting electronic effects of various substituents in the dye formation reaction. These results are useful in the synthesis of symmetrical and unsymmetrical squaraine dyes that can have potential biological and photodynamic therapeutical applications. 相似文献
19.
Jisha VS Arun KT Hariharan M Ramaiah D 《Journal of the American Chemical Society》2006,128(18):6024-6025
With the objective of developing small molecule based probes for proteins, interactions of polyhydroxyl-substituted squaraine dye (SQ) with bovine serum albumin (BSA) have been investigated by absorption, steady-state and time-resolved fluorescence, circular dichroism (CD), cyclic voltammetry (CV), 1H NMR, scanning electron, and tapping mode atomic force microscopic techniques. Increase in addition of BSA resulted in increase in absorbance and fluorescence quantum yields (80-fold) of SQ, along with significant bathochromic shifts in the absorption and fluorescence maxima. Half-reciprocal analysis of the absorption data gave a 1:1 stoichiometry for the complex between BSA and SQ with high association (Kass) constant of (1.4 +/- 0.1) x 106 M-1 and change in free energy of -35 kJ/mol. The complex formation was further confirmed by observation of induced CD signal corresponding to the SQ chromophore at 610 nm, upfield shift (about Deltadelta 0.1 ppm) of aromatic protons of SQ in 1H NMR spectra, and decrease in current intensity (CV) of SQ when bound to BSA. The picosecond time-resolved fluorescence studies indicated that the BSA-SQ complex exhibits biexponential decay with significantly enhanced lifetimes of 0.5 and 1.5 ns when compared to the lifetime of SQ (tau = 121 ps) in the absence of BSA. Employing displacement cum fluorimetry using site-specific binding ligands, such as dansylproline and dansylamide, indicated that SQ binds with protein selectively at site II involving hydrophobic, hydrogen bonding, and electrostatic interactions. The uniqueness of this molecular system is that it interacts with BSA selectively at site II and signals the binding event through dual mode recognition of "visual color" change and "turn on" fluorescence mechanism. 相似文献