Multi-branched carbazole derivatives for two-photon absorption and two-photon excited fluorescence

Carbazole-core multi-branched chromophores 9-ethyl- 3, 6-bis （ 2- { 4- [ 5- （4-tert-butyl-phenyl） - [ 1, 3, 4 ] oxadiazol-2-yl ] - phenyl }-vinyl） -carbazole（3） and 9-ethyl-3-（ 2- {4-[ 5-（4-tert-butyl- phenyl） -[ 1, 3, 4 ] oxadiazol-2-yl ] -phenyl }-vinyl ） -carbazole （ 2 ） are synthesized through Wittig reaction and characterized by nuclear magnetic resonance（NMR）and infrared（IR）. The two- photon absorption properties of chromophores are investigated. These chromophores exhibit large two-photon absorption crosssections and strong blue two-photon excited fluorescence. The cooperative enhancement of two-photon absorption（TPA） in the multi-branched structures is observed. This enhancement is partly attributed to the electronic coupling between the branches. The electronic push-pull structures in the arm and their cooperative effects help the extended charge transfer for TPA.

Two-photon Excited Fluorescence of Bithiophene Derivatives

Two new bithiophene derivatives named as 5, 5-bis(p-N,N-dimethylaminostyryl)-2, 2 -bithiophene (BMSBT), and 5, 5-bis(p-N,N-diethylaminostyryl)-2, 2-bithiophene (BESBT) have been synthesized. Both compounds can emit strong single-photon excited fluorescence (SPEF) and two-photon excited fluorescence (TPEF) with the emission peaks around ~560 nm and with the lifetime of ~1ns.

Crystal Structure, One-and Two-photon Excited Fluorescence and Bioimaging of a D-π-A Structural Triphenylamine Derivative

An electron donor-π-bridge-electron acceptor(D-π-A) optical functional organic compound comprising a triphenylamine moiety as the electron donor and pyridine moiety as the electron acceptor was synthesized. The structure of the compound was solved by single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group P21, with a = 9.753(5), b = 8.815(5), c = 25.554(5) ?, β = 96.315(5)°, V = 2184(2) ?~3, Z = 2, D_c = 1.136 g/m^3, F(000) = 792, Μr = 746.92, μ = 0.069 mm^(-1), the final R = 0.0658 and wR = 0.1730 for 6790 observed reflections with I > 2(I). Study of nonlinear optical properties shows that the compound exhibits excellent two-photon excited fluorescence with the two-photon absorption cross-section value of 116 GM. The structure-property relationship was researched in detail through X-ray crystallography and quantum chemical calculation. Result of living cell imaging experiment shows its potential in fluorescence microscopy bioimaging.

New Thiophene Derivatives with Two-photon Excited Fluorescence

Two new compounds involving a thiophene moiety named as 2,5-bis[4-(N,N- diphenyl- amino)styryl]thiophene (BPST) and 2,5-bis[4-(N,N-diethylamino)styryl]thiophene (BEST) have been synthesized. The two-photon absorption cross section of BPST was measured as large as 256 × 10-50 cm4·s/photon, when it was excited by 800 nm femtosecond laser.

Single & Two-photon Excited Fluorescence of Two New Compounds with 2-Benzothiazolyl as Electron Acceptor

Two new D--A type compounds, where electron-donor D is tertiary amino group, electron-acceptor A is 2-benzothiazolyl and ?is two conjugated styryl units, have been synthesized. They are named as trans, trans-2-{4-[4-(N, N-diethylamino)styryl]styryl}-1, 3-benzothiazole and trans, trans-2-{4-[4-(N, N-diphenylamino)styryl]styryl}-1, 3-benzothiazole. Both compounds show strong two-photon excited fluorescence in yellow-orange region when excited by a femtosecond laser at 800 nm.

Two-photon excitation fuorescence lifetime imaging microscopy:A promising diagnostic tool for digestive tract tumors

Digestive tract tumors acount for 15%and 19.3%of the cancer incidence and deaths,respec-tively.Early detection of digestive tract tumors is crucial to the reduction of global cancer burden.Two-photon excitation fuorescence lifetime imaging microscopy(TP-FLIM)allows non-invasive,label free,three-dimensional,high-resolution imaging of living tisues with not only histological but also biochemical characterization ability in both qualitative and quantitative way.Benefiting from these advantages,this technology is protmising for clinical diagnosis of digestive tract tumors.In recent years,many efforts have'been made in this field and some remarkable progress has been achieved.In this paper,we overview the recent progress of TP-FLIM-based researches on digestive tract tumor detection.Among them,our latest results on the gastric cancer and esophageal cancer are elaborately depicted.Finally,we outlook and discuss the potential advantages and challenges of TP-FLIM in future clinical applications.

FRET-based two-photon benzo[a]phenothiazinium photosensitizer for fluorescence imaging-guided photodynamic therapy

To overcome the conflict between the long-wavelength excitation and high singlet oxygen quantum yield of photosensitizers,we conjugated a two-photon fluorophore,tetrahydroquinoxaline coumarin(TQ),and an efficient photodynamic therapeutic agent,benzo[a]phenothiazinium(NBS-NH_(2)),through a hexamethylene linker to build a two-photon photosensitizer,TQ-NBS.In TQ-NBS,TQ served as an energy donor and NBS-NH_(2) acted as an energy acceptor;and TQ-NBS was a F?rster resonance energy transfer(FRET)cassette with a 92.8%efficiency.The large two-photon absorption cross-section of TQ allowed photosensitizer TQ-NBS to work in a 900 nm two-photon excitation(TPE)mode,which greatly benefited the deep tissue penetration in PDT treatment.Meanwhile,the excellent phototoxicity and near-infrared fluorescence of NBS-NH2was kept in TQ-NBS under a TPE mode via a FRET process.Photosensitizer TQ-NBS exhibited a high phototoxic efficacy in living cells and tumor-bearing mice.

生物组织背向SHG和TPEF的影响因素

由于生物组织的复杂性和多样性,以及样品制备等因素的影响,实验观察到的生物组织的背向二次谐波(second harmonic generation,SHG)和双光子激发荧光(two-photon excitation fluorescence,TPEF)效应的差异较大。以鼠尾组织作为实验对象,共40个切片,分为横向和纵向、HE染色和未染色四组,采用飞秒激光器作为激发光,用双光子激光扫描共焦显微镜(two-photon laser scanning confocal microscope,TPLSCM)观察和分析了样品在不同的制备方式、激发波长、激发功率、扫描深度等条件下的背向SHG和TPEF的变化曲线,讨论和比较了生物组织的背向SHG和TPEF的影响因素以及二者之间的异同,并尝试对实验现象做出了一定的解释。

Synthesis and Two-photon Absorption Properties of s-Triazine Derivatives

Two new s-triazine derivatives, which belong to linear dipolar type and triangle octupolar type respectively, have been synthesized. The structure of the dipolar compound has been determined by X-ray diffraction. The two-photon absorption cross-section σ, and the two-photon excited fluorescence (TPEF) intensities are increased significantly from dipolar compound to octupolar compound.

Non-invasive imaging of pathological scars using a portable handheld two-photon microscope

Background:Pathological scars are a disorder that can lead to various cosmetic,psychological,and functional problems,and no effective assessment methods are currently available.Assessment and treatment of pathological scars are based on cutaneous manifestations.A two-photon microscope(TPM)with the potential for real-time non-invasive assessment may help determine the under-surface pathophysiological conditions in vivo.This study used a portable handheld TPM to image epidermal cells and dermal collagen structures in pathological scars and normal skin in vivo to evaluate the effectiveness of treatment in scar patients.Methods:Fifteen patients with pathological scars and three healthy controls were recruited.Imaging was performed using a portable handheld TPM.Five indexes were extracted from two dimensional(2D)and three dimensional(3D)perspectives,including collagen depth,dermo-epidermal junction(DEJ)contour ratio,thickness,orientation,and occupation(proportion of collagen fibers in the field of view)of collagen.Two depth-dependent indexes were computed through the 3D second harmonic generation image and three morphology-related indexes from the 2D images.We assessed index differences between scar and normal skin and changes before and after treatment.Results:Pathological scars and normal skin differed markedly regarding the epidermal morphological structure and the spectral characteristics of collagen fibers.Five indexes were employed to distinguish between normal skin and scar tissue.Statistically significant differences were found in average depth(t=9.917,P<0.001),thickness(t=4.037,P<0.001),occupation(t=2.169,P<0.050),orientation of collagen(t=3.669,P<0.001),and the DEJ contour ratio(t=5.105,P<0.001).Conclusions:Use of portable handheld TPM can distinguish collagen from skin tissues;thus,it is more suitable for scar imaging than reflectance confocal microscopy.Thus,a TPM may be an auxiliary tool for scar treatment selection and assessing treatment efficacy.

Optical second-harmonic generation imaging for identifying gastrointestinal stromal tumors

Gastrointestinal stromal tumors(GISTs)are the most common mesenchymal tumors arising in the digest tract.It brings a challenge to diagnosis because it is asymptomatic clinically.It is well known that tumor development is often accompanied by the changes in the morphology of collagen fibers.Nowadays,an emerging optical imaging technique,second-harmonic generation(SHG),can directly identify collagen fibers without staining due to its noncentrosymmetric properties.Therefore,in this study,we attempt to assess the feasibility of SHG imaging for detecting GISTs by monitoring the morphological changes of collagen fibers in tumor microenvironment.We found that collagen alterations occurred obviously in the GISTs by comparing with normal tissues,and furthermore,two morphological features from SHG images were extracted to quantitatively assess the morphological difference of collagen fibers between normal muscular layer and GISTs by means of automated image analysis.Quantitative analyses show a significant difference in the two collagen features.This study demonstrates the potential of SHG imaging as an adjunctive diagnostic tool for label-free identification of GISTs.

uorescence microendoscopy imaging based on GRIN lenses with one- and two-photon excitation modes

With the rapid development of life sciences, there is an increasing demand for intravital fluorescence imaging of small animals. However, large dimensions and limited working distances of objective lenses in traditional fluorescence microscopes have limited their imaging applications mostly to superficial tissues. To overcome these disadvantages, researchers have developed the graded-index （GRIN） probes with small diameters for imaging internal organs of small animals in a minimally invasive fashion. However, dynamic imaging based on GRIN lens has not been studied extensively. Here, this paper presented a fluorescence endoscopic imaging system based on GRiN lenses using one-photon and two-photon excitation. GRIN lenses with 1.15 mm diameter and 7.65 mm length were used in the system. The images were acquired by a compact laser scanning imaging system with a resonant galvo-mirror system to scan the laser beam and a photomultiplier tube （PMT） to detect fluorescence signals. Experimental results showed that this system using two-photon excitation could implement dynamic fluorescence microendoscopic imaging and monitor the movement of blood flow beneath the skin in anesthetized mice while producing images with higher contrast and signal to noise ratio （SNR） than those using one photon excitation. It would be a useful tool for studying biological processes of small animals or plants in vivo.

ULTRASHORT PULSE MULTISPECTRAL NON-LINEAR OPTICAL MICROSCOPY

Ultrashort pulse,multispectral non-linear optical microscopy(NLOM)is developed and used to image,simultaneously,a mixed population of cells expressing different fluorescent protein mutants in a 3D tissue model of angiogenesis.Broadband,sub-10-fs pulses are used to excite multiple fluorescent proteins and generate second harmonic in collagen.A 16-channel multispectral detector is used to delineate the multiple non-linear optical signals,pixel by pixel,in NLOM.The ability to image multiple fluorescent protein mutants and collagen,enables serial measurements of cell-cell and cell-matrix interactions in our 3D tissue model and characterization of fundamental processes in angiogenic morphogenesis.

pH-responsive metal nanoparticles as high contrast theranostic agents for selective imaging and synergistic cancer therapy

The low signal-to-noise ratio(S/N)and single functionality of fluorescence imaging agents have limited their practical applications.Bright two-photon excitation(2PE)imaging probes are highly desirable in vivo with larger imaging depth,minor autofluorescence background,and less photodamage.Herein,we developed responsive aggregated gold nanoparticles(Au NPs)as high contrast 2PE imaging agents,capable of emitting red fluorescence upon excitation of near-infrared(NIR)laser and possessing a high signal-to-noise ratio(S/N of 2,475).By forming aggregates in situ inside tumor tissue,doxorubicin hydrochloride(DOX)-loaded mix-charged gold nanoparticles(DOX-MC-Au NPs)were utilized to act as selective fluorescence imaging probes and precise therapy agents.These high-contrast theranostic agents offer a promising potential for precise cancer imaging and therapy,which might open a new venue to multifunctional and noninvasive theranostics.

Synthesis of two carbazole-based dyes and application of two-photon initiating polymerization

Two carbazole-based polymerization initiators possessing blue fluorescence emission have been synthesized via Wittig reaction in the solid phase at room temperature.Two-photon excited fluorescence(TPEF) spectra for them were investigated under 800 nm fs laser pulse and two-photon absorption cross sections were determined by the Z-scan technique.Then two-photon initiating polymerization(TPIP) microfabrication experiments were successfully carried out.Three-dimensional lattice and artificial defects were gained,indicating that they were viable candidates for the two-photon polymerization initiator in practical application of microfabrication.

Strong optical nonlinearities of self-assembled polymorphic microstructures of phenylethynyl functionalized fluorenones

Highly efficient nonlinear optical（NLO） materials with well-defined architectures in the wavelength and subwavelength length scales are of particular importance for next generation of integrated photonic circuits. Fluorenone analogues have been demonstrated to be promising candidates as building blocks for assembly of organic NLO materials thanks to their synergistic supramolecular interactions and brilliant optical properties. Here we have studied the polymorphs of a phenylethynyl functionalized fluorenone derivative, and their controlled self-assembly for microstructures with different morphologies. These polymorphic microcrystals exhibit very distinctive NLO properties, highly related to their supramolecular and electronic structures.

Nonlinear optical metal-organic frameworks for ratiometric temperature sensing in physiological range

The precise and real-time sensing of the temperature within the physiological range is of great significance in biology and medicine.Here,a Zn-based metal-organic framework(MOF)named ZnTCOMA is synthesized with good SHG performance due to its unique structure of the ligand and 3 D frameworks.By encapsulating the two-photon fluorescent dye DMASE into the pores of Zn-TCOMA,the composite Zn-TCOMA■DMASE is obtained and simultaneously exhibits SHG response and two-photon fluo rescence.Utilizing the intensity ratio between two-photon fluorescence of DMASE and SHG signal of Zn-TCOMA,Zn-TCOMA■DMASE exhibits ratiometric temperature sensing property at physiological temperature region of 20~60℃with high sensitivity.This MOF thermometer also shows excellent repeatability,good biocompatibility,and high temperature resolution of 0.018℃,opening a new avenue to develop diverse optical thermometric or thermographic applications in biotechnology or other areas.