Fluorescence resonance energy transfer in a novel two-photon absorbing system

A novel fluorescence resonance energy transfer (FRET) system containing a two-photon absorbing dye and a nile red chromophore has been synthesized. Upon two-photon excitation by laser at 815 nm this molecule displays efficient energy transfer from the two-photon absorbing dye to the nile red moiety, with an 8-fold increase in emission compared to the model compound. Similarly, single-photon excitation of the two-photon absorbing moiety at 405 nm results in >99% energy-transfer efficiency, along with a 3.4-fold increase in nile red emission compared to direct excitation of the nile red chromophore at 540 nm. This system provides an effective way to use IR radiation to excite molecules that, by themselves, have little or no two-photon absorption.     

双光子荧光有机纳米粒子的细胞染色

本文采用具有较大双光子吸收截面的有机分子2,5,2′,5′-(4′-N,N-二苯胺苯乙烯基)联苯(DPA-TSB)(双光子吸收截面δ: 3288 GM, 1 GM=1×10^-50 cm⁴·s·photon^-1·molecule^-1), 通过再沉淀法制备水相分散的纳米粒子. 研究表明, 这种有机双光子纳米粒子可以有效地富集在细胞质中, 对细胞染色显示出良好的荧光成像能力.     

Two‐Photon Photochromism of a Diarylethene Enhanced by Förster Resonance Energy Transfer from Two‐Photon Absorbing Fluorenes

Resonance energy transfer from two-photon absorbing fluorene derivatives to the photochromic compound 3,4-bis-(2,4,5-trimethyl-thiophen-3-yl)furan-2,5-dione (PC 1) is investigated in hexane under one- and two-photon excitation. The quenching of the steady-state fluorescence of donor molecules in the presence of the diarylethene acceptor is used to study the nature of resonance energy transfer. The F?rster distances and critical acceptor concentrations are determined for nonbound donor-acceptor pairs in homogeneous molecular ensembles. Quite significantly, up to a two-fold enhancement in the velocity of the photochromic transformation of 1, in the presence of two-photon absorbing fluorene derivatives, is demonstrated.     

Two-photon sensor for metal ions derived from azacrown ether

A two-photon sensor for the metal ions derived from azacrown ether as the receptor is reported. The sensor emits strong two-photon fluorescence when excited by 800 nm laser photons. Moreover, the binding constants measured by the one- and two-photon fluorescence are similar. This result may be useful for the design of efficient two-photon fluorescence probes for biological substrates.     

双光子荧光探针研究及其应用*

双光子荧光显微成像兼具诸如近红外激发、暗场成像、避免荧光漂白和光致毒、定靶激发、高横向分辨率与纵向分辨率、降低生物组织吸光系数及降低组织自发荧光干扰等特点而显著地优于单光子荧光显微成像,为生命科学研究提供了更为锐利的工具。而用于像离子的含量及其对生理的影响、离子参与的生理活动机制、离子与分子的作用、特定分子的分布及其相互作用等方面研究的双光子荧光探针,是实现成像的关键。双光子荧光探针的研究旨在促进双光子荧光显微镜应用的发展,促进生命科学、医学科学的快速发展,同时也带动双光子荧光探针所隶属的化学这一学科的发展。因此对双光子荧光探针的研究具有重要的理论和实践意义。该文综述了双光子荧光显微成像的优点、双光子荧光探针设计的原理及双光子荧光探针在离子分析方面的应用,并展望了这类荧光探针的发展趋势与应用前景。     

基于咔唑的双光子荧光次氯酸根探针光学性质及响应机理

采用含时密度泛函理论与响应函数理论相结合的方法,研究了两种实验室新合成的水溶性双光子荧光次氯酸根（ClO^-）探针分子HCH和HCM的单光子吸收、双光子吸收和荧光发射性质。计算结果表明,HCH和HCM分子与ClO^-反应后,生成物的光吸收和光发射性质均发生明显变化,相应的吸收和发射峰位都发生了明显蓝移,荧光强度展现出明显的增强。另外,两探针分子都具有较大的双光子吸收截面,且与ClO^-反应后,生成物的双光子吸收截面值显著增加,因此两分子均可作为性能优良的双光子荧光探针分子。此外,通过分析HCH和HCM分子与ClO^-反应前后的Mulliken电荷布居情况,从理论上证实了该系列荧光探针分子的识别机理是C＝N异构化。     

Two-photon Lysotrackers for in vivo imaging

We report two-photon Lysotrackers (CLT-blue and CLT-yellow) that can be excited by 750-840 nm femtosecond laser pulses and emit at 470 and 550 nm, respectively. They can be easily loaded into cells and tissue slices for visualization of lysosomes in live cells and tissues for a long period of time through two-photon microscopy. When combined with appropriate two-photon probes for other biological targets, these novel probes would greatly facilitate the two-photon microscopy colocalization experiments.     

Folic acid-functionalized two-photon absorbing nanoparticles for targeted MCF-7 cancer cell imaging

We report a facile strategy to synthesize folic acid-functionalized two-photon absorbing (TPA) nanoparticles with aggregation-induced emission for targeted cancer cell imaging using a two-photon fluorescence microscope.     

氧芴三苯胺多枝分子的双光子吸收与电化学行为

研究了3个氧芴/三苯胺衍生物: E-2,8-双(4-二苯胺基苯乙烯基)氧芴(简称OT-G1)、E-2,8-双[4-(二苯基氨基-二苯乙烯基)(4’-溴苯基)氨基-苯乙烯基]氧芴(简称OT-G1.5)和E-2,8-双-[4’,4″-二-(二苯胺基苯乙烯基)-4-二苯胺基苯乙烯基]氧芴(简称OT-G2)的双光子吸收和电化学行为. 研究结果表明, 分子“代数”从1→1.5→2增高, 氧芴三苯胺多枝分子的HOMO能级升高、双光子荧光强度和双光子吸收截面明显增大. 由于HOMO能级的升高有利于分子的电荷转移, 因而分子表现出强的双光子吸收能力, 这表明可通过电化学行为来推断出分子的双光子吸收性能.     

Two-photon fluorescent probes for long-term imaging of calcium waves in live tissue

2-Acetyl-6-(dimethylamino)naphthalene-derived two-photon fluorescent Ca2+ probes (ACa1-ACa3) are reported. They can be excited by a 780 nm laser beam, show 23-50-fold enhancement in one- and two-photon excited fluorescence in response to Ca2+, emit fourfold stronger two-photon excited fluorescence than Oregon Green 488 BAPTA-1 upon complexation with Ca2+, and can selectively detect intracellular free Ca2+ ions in live cells and living tissues with minimum interference from other metal ions and membrane-bound probes. Moreover, these probes are capable of monitoring calcium waves at a depth of 120-170 microm in live tissues for 1100-4000 s using two-photon microscopy with no artifacts of photobleaching.     

3D Stereolithography by Using Two-Photon Photopolymerization

Summary: This article describes the development and evolution of two-photon lithography of 3-dimensional (3D) polymeric structures through two-photon photopolymerization (TPP) and the materials used to facilitate the same. The first part elaborates on the advantages of TPP over conventional lithographic techniques used in the fabrication of 3D microelectromechanical systems (MEMS). The second part introduces the preparation of highly efficient organic two-photon absorbing materials based on the centro-symmetric π-conjugated system and their performance as sensitizers in two-photon polymerization.     

Synthesis of triphenylamine-cored dendritic two-photon absorbing chromophores

[structure: see text]. A new series of dendritic two-photon absorbing chromophores containing triphenylamine moiety as a core or branching points have been synthesized through a convergent synthetic strategy. One-photon and two-photon optical properties of these molecules were characterized. In the nanosecond time domain, these molecules exhibited large two-photon absorption (TPA) cross sections up to 7.56-12.2 x 10(-44) s cm(4) at 800 nm, indicating that these molecular structures were viable candidates for various two-photon related applications.     

Recent advances in mitochondria-and lysosomes-targeted small-molecule two-photon fluorescent probes

This review summarized the recent advances in small-molecule two-photon fl uorescent probes for monitoring a wide variety of biomolecules and changes inside micro-environment in mitochondria and lysosomes, or served as mitotracker and lysotracker with the assistance of two-photon microscopy.     

6-Substituted quinoline-based ratiometric two-photon fluorescent probes for biological Zn2+ detection

New ratiometric two-photon fluorescent probes are developed from 6-substituted quinolines for biological Zn(2+) detection. They show large red shifts and good ratiometric responses upon Zn(2+) binding. They also exhibit high ion selectivities and large two-photon absorption cross sections at nearly 720 nm. Because the new probes are cell-permeable, they can be used to detect intracellular zinc flux under two-photon excitation.     

Metal ion sensing novel calix[4]crown fluoroionophore with a two-photon absorption property

1,3-Alternate calix[4]arene-based fluorescent chemosensors bearing two-photon absorbing chromophores have been synthesized, and their sensing behaviors toward metal ions were investigated via absorption band shifts as well as one- and two-photon fluorescence changes. Free ligands absorb the light at 461 nm and weakly emit their fluorescence at 600 nm when excited by UV-vis radiation at 461 nm, but no two-photon excited fluorescence is emitted by excitation at 780 nm. Addition of an Al(3+) or Pb(2+) ion to a solution of the ligand causes a blue-shifted absorption and enhanced fluorescence due to a declined resonance energy transfer (RET) upon excitation by one- and two-photon processes. Addition of a Pb(2+) ion to a solution of 1.K(+) results in a higher fluorescence intensity than the original 1.Pb(2+) complex regardless of one- or two-photon excitation, due to the allosteric effect induced by the complexation of K(+) with a crown loop.     

Syntheses of Novel Asymmetric Cyclopentanone Dyes and Measurement of Two－photon Absorption Cross－section

A simple synthesis route with a high yield of novel asymmetric cyclopentanone dyes 3a—3e and their highly two-photon up-converted fluorescences are reported. The dyes have good solubilities in most of ordi-nary solvents, a wide UV absorption wavelength range from 380—540 nm, and high fluorescence quantum yields. The two-photon absorption cross-sections of dyes 3a—M were measured in chloroform by a two-pho-ton induced fluorescence method. All of these properties of the new dyes make them suitable for being used as two-photon fluorescent probes.     

Towards "smart" multiphoton fluorophores: strongly solvatochromic probes for two-photon sensing of micropolarity

New fluorophores, combining broad, very high two-photon absorption in the near-infrared region with a marked dependence of their emission spectra on solvent polarity, have been designed as model probes for two-photon sensing of the chemical environment.     

Y-shaped two-photon absorbing molecules with an imidazole-thiazole core

Two new classes of two-photon absorbing Y-shaped molecules have been developed to possess an imidazole-thiazole core and a stilbene-type conjugation pathway with either nitro or sulfonyl as terminal electron-accepting group.     

Photophysics of a series of efficient fluorescent pH probes for dual-emission-wavelength measurements in aqueous solutions

This paper evaluates the 5-aryl-2-pyridyloxazole backbone to engineer donor-acceptor fluorescent pH probes after one- or two-photon absorption. Parent fluorophores, as well as derivatives that can be used to label biomolecules, can be easily obtained in good yields. These molecules exhibit a large one-photon absorption in the near-UV range, and a strong fluorescence emission that covers the whole visible domain. The 5-aryl-2-pyridyloxazole derivatives also possess significant cross sections for two-photon absorption. Upon pyridine protonation, large shifts were observed in the absorption spectra after one- and two-photon excitation, as well as in the emission spectra. This feature was used to measure the pK(a) of the investigated compounds that range between 2 and 8. In most of the investigated derivatives, the pK(a) increased upon light excitation and protonation exchanges took place during the lifetime of the excited state, as shown by phase-modulation fluorometry analysis. Several 5-aryl-2-pyridyloxazole derivatives are suggested as efficient probes to reliably measure the pH of aqueous solutions by means of ratiometric methods that are dependent on fluorescence emission.     

Novel multi-branched two-photon polymerization initiators of ketocoumarin derivatives

Novel multi-branched two-photon absorbing dyes containing highly efficient UV–vis curing initiator, ketocoumarin (3-acetyl-7-diethylaminocoumarin), were synthesized. There linear and non-linear optical properties were studied and the cooperatively enhanced two-photon absorption of two- and three-branched dyes were confirmed by femtosecond laser pulses. The largest two-photon absorption cross-section was obtained as 1117 GM. The results of photobleaching experiments showed that all dyes had very fast electron transferring speed with the commercial coinitiator o-Cl-hexaarylbisimidazoles (HABI). The two-photon polymerization initiated by a bimolecular system composed of the two-branched dye and HABI was investigated. This photopolymer system presented high photoinitiating efficiency. The single-shot two-photon exposure of the resin film was achieved with a threshold as 1 TW/cm² at 800 nm.