Time-resolved Fluorescence Decay Study of Hematoporphyrin Derivative

Timefluorescence decays were first performed on hematoporphyrin derivative laser No.3 in buffer at different micelles concentration.The flu.orescence lifetime constants,measured with a time-correlated single photon counting system;could be fitted by two or three exponential components with different relative peak amplitudes depending on the observation wavelength^thus indicating the presence of different emitting molecular species and/or of molecular species in different aggregational states.

Time-Resolved Fluorescence Study of C_(60) Solution

Using a picosecond excitation source and a time-resolved streak camera detection system,the time-resolved fluorescence spectra of purified C_(60) have been recorded from toluene solution at room temperature.A fluorescence peak at about 730nm was detected and its lifetime was directly determined to be 1.1±0.1 ns.Two fluorescence peaks obtained from the mixture of C_(60) and C_(70) at 676 and 696nm were mainly related to C_(70) content.

Assembling Tunable Time-Resolved Fluorescence Layer onto Nano-Gold

The assembling of a coating of time-resolved fluorescent chelator BSPDA (abbreviated for 4,7-bis(sulfhydrylphenyl)-1,10-phenanthroline-2,9-dicarboxylic acid) onto a nano-gold layer was demonstrated. First, BSPDA was synthesized by simple procedures, and then an approach was developed to immobilize BSPDA onto the nano-gold layer deposited on a silane modified glass substrate, whereby europium ion (Ⅲ, Eu3+) was captured and released owing to the interactive process of complexation and dissociation between BSPDA functionalized coating and Eu3+ solution. The fluorescence spectra and related lifetimes were determined. Also, the BSPDA functionalized coating′s specific complexation with Eu3+ on the BSPDA assembly layer and the nonspecific adsorption of Eu3+ on the nano-gold layer were compared. These results allowed a selective complexation of Eu3+ by assembling a BSPDA chelating layer on the nano-gold layer; thus, a tunable time-resolved fluorescent layer was covalently attached. The results of the nanoparticle assembling and probing (or labeling) processes to specific bio-systems were very interesting and had significant implications to time-resolved-fluorescence-based detection on biosensor surfaces such as DNA chip and to arrayed light display devices.

Enhancement of rapid lifetime determination for time-resolved fluorescence imaging in forensic examination

An enhancement method of rapid lifetime determination is proposed for time-resolved fluorescence imaging to discriminate substances with approximate fluorescence lifetime in forensic examination. In the method, an image-exclusive-OR treatment with filter threshold adaptively chosen is presented to extract the region of interest from dual-gated fluorescence intensity images, and then the fluorescence lifetime image is reconstructed based on the rapid lifetime determination algorithm. Furthermore, a maximum and minimum threshold filtering is developed to automatically realize visualization enhancement of the lifetime image. In proof experiments, compared with traditional fluorescence intensity imaging and rapid lifetime determination method, the proposed method automatically distinguishes altered and obliterated documents written by two brands of highlighters with the same color and close fluorescence lifetime.

Ultrafast carrier dynamics in GeSn thin film based on time-resolved terahertz spectroscopy

We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn under femtosecond laser excitation at 2500 nm,and its pump-induced photoconductivity can be explained by the Drude–Smith model.The carrier recombination process is mainly dominated by defect-assisted Auger processes and defect capture.The firstand second-order recombination rates are obtained by the rate equation fitting,which are(2.6±1.1)×10^(-2)ps^(-1)and(6.6±1.8)×10^(-19)cm^(3)·ps^(-1),respectively.Meanwhile,we also obtain the diffusion length of photo-generated carriers in GeSn,which is about 0.4μm,and it changes with the pump delay time.These results are important for the GeSn-based infrared optoelectronic devices,and demonstrate that Ge Sn materials can be applied to high-speed optoelectronic detectors and other applications.

NIR-II fluorescence imaging in liver tumor surgery: A narrative review

In liver tumor surgery,the recognition of tumor margin and radical resection of microcancer focis have always been the crucial points to reduce postoperative recurrence of tumor.However,naked-eye inspection and palpation have limited effectiveness in identifying tumor boundaries,and traditional imaging techniques cannot consistently locate tumors in real time.As an intraoperative real-time navigation imaging method,NIRfluorescence imaging has been extensively studied for its simplicity,reliable safety,and superior sensitivity,and is expected to improve the accuracy of liver tumor surgery.In recent years,the research focus of NIRfluorescence has gradually shifted from the-rst near-infrared window(NIR-I,700–900 nm)to the second near-infrared window(NIR-II,1000–1700 nm).Fluorescence imaging in NIR-II reduces the scattering effect of deep tissue,providing a preferable detection depth and spatial resolution while signi-cantly eliminating liver autofluorescence background to clarify tumor margin.Developingfluorophores combined with tumor antibodies will further improve the precision offluorescence-guided surgical navigation.With the development of a bunch offluorophores with phototherapy ability,NIR-II can integrate tumor detection and treatment to explore a new therapeutic strategy for liver cancer.Here,we review the recent progress of NIR-IIfluorescence technology in liver tumor surgery and discuss its challenges and potential development direction.

Self-confocal NIR-II fluorescence microscopy for multifunctional in vivo imaging

Fluorescence imaging in the second near-infrared window(NIR-II,900–1880 nm)with less scattering background in biological tissues has been combined with the confocal microscopic system for achieving deep in vivo imaging with high spatial resolution.However,the traditional NIR-IIfluorescence confocal microscope with separate excitation focus and detection pinhole makes it possess low confocal e±ciency,as well as di±cultly to adjust.Two types of upgraded NIR-IIfluorescence confocal microscopes,sharing the same pinhole by excitation and emission focus,leading to higher confocal e±ciency,are built in this work.One type is-ber-pinhole-based confocal microscope applicable to CW laser excitation.It is constructed forfluorescence intensity imaging with large depth,high stabilization and low cost,which could replace multiphotonfluorescence microscopy in some applications(e.g.,cerebrovascular and hepatocellular imaging).The other type is air-pinhole-based confocal microscope applicable to femtosecond(fs)laser excitation.It can be employed not only for NIR-IIfluorescence intensity imaging,but also for multi-channelfluorescence lifetime imaging to recognize different structures with similarfluorescence spectrum.Moreover,it can be facilely combined with multiphotonfluorescence microscopy.A single fs pulsed laser is utilized to achieve up-conversion(visible multiphotonfluorescence)and down-conversion(NIR-II one-photonfluorescence)excitation simultaneously,extending imaging spectral channels,and thus facilitates multi-structure and multi-functional observation.

Isomeric fluorescence sensors for wide range detection of ionizing radiations

In order to achieve a wider range of ionizing radiations detection,novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduced electron transfer(PET)effect.Two perylene diimide isomers PDI-P and PDI-B were designed and synthesized,and their molecular structures were characterized by high-resolution Fourier transform mass spectrometry(HRMS),nuclear magnetic resonance hydrogen and carbon spectroscopy(~1H and~(13)C NMR).The interaction between ionizing radiation and fluorescent molecules was simulated by HCl titration.The results show that combining PDIs and HCl can improve fluorescence through the retro-PET process.Despite the similarities in chemical structures,the fluorescent enhancement multiple of PDI-B with aromatic amine as electron donor is much higher than that of PDI-P with alkyl amine.In the direct irradiation experiments of ionizing radiation,the emission enhancement multiples of PDI-P and PDI-B are 2.01 and 45.4,respectively.Furthermore,density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations indicate that the HOMO and HOMO-1 energy ranges of PDI-P and PDI-B are 0.54 e V and 1.13 e V,respectively.A wider energy range has a stronger driving force on electrons,which is conducive to fluorescence quenching.Both femtosecond transient absorption spectroscopy(fs-TAS)and transient fluorescence spectroscopy(TFS)tests show that PDI-B has shorter charge separation lifetime and higher electron transfer rate constant.Although both isomers can significantly reduce LOD during PET process,PDI-B with aromatic amine has a wider detection range of 0.118—240 Gy due to its larger emission enhancement,which is a leap of three orders of magnitude.It breaks through the detection range of gamma radiation reported in existing studies,and provides theoretical support for the further study of sensitive and effective new materials for ionizing radiation detection.

Near-Infrared Fluorescence Imaging Contrast Agents for Clinical Research: Limitations and Alternatives

Introduction: Near-infrared fluorescence imaging is a technique that will establish itself in the short term at the international level because it is recognized for its potential to improve the performance of surgical interventions, its moderate investment and operating costs and its portability. Although the technology is now mature, there is currently the problem of the availability of contrast agents to be injected IV. The aim of this methodology article is to propose an alternative solution to the need for contrast agents for clinical research, particularly in oncology. Methodology: They consist of coupling a fluorescent marker in the form of an NHS derivative, such as IR DYE manufactured in compliance with GMP, with therapeutic monoclonal antibodies having marketing authorization for molecular imaging. For a given antibody, the marking procedure must be the subject of a validation file on the final preparation filtered on a sterilizing membrane at 0.22 μm. Once the procedure has been validated, it would be unnecessary to repeat the tests before each clinical research examination. A check of the marking by thin-layer chromatography (TLC) and place it in a sample bank at +4˚C for 1 month of each injected formulation would be sufficient for additional tests if necessary. Conclusion: Molecular near-infrared fluorescence imaging is experiencing development, the process of which could be accelerated by greater availability of clinical contrast agents. Alternative solutions are therefore necessary to promote clinical research in this area. These methods must be shared to make it easier for researchers.

A ratiometric fluorescent probe for hypoxanthine detection in aquatic products based on the enzyme mimics and fluorescence of cobalt-doped carbon nitride

A ratiometric fluorescent probe for hypoxanthine(Hx)detection was established based on the mimic enzyme and fluorescence characteristics of cobalt-doped graphite-phase carbon nitride(Co doped g-C_(3)N_(4)).In addition to emitting strong fluorescence,the peroxidase activity of Co doped g-C_(3)N_(4)can catalyze the reaction of O-phenylenediamine and H_(2)O_(2)to produce diallyl phthalate which can emit yellow fluorescence at 570 nm.Through the decomposition of Hx by xanthine oxidase,Hx can be indirectly detected by the generating hydrogen peroxide based on the measurement of fluorescent ratio I(F_(570)/F_(370)).The linear range was 1.7-272.2 mg/kg(R^(2)=0.997),and the detection limit was 1.52 mg/kg(3σ/K,n=9).The established method was applied to Hx detection in bass,grass carp,and shrimp,and the data were verified by HPLC.The result shows that the established probe is sensitive,accurate,and reliable,and can be used for Hx detection in aquatic products.

Determination of Benzo[a]pyrene in Edible Oil by High Performance Liquid Chromatography-Fluorescence Detector (HPLC-FL)

In this study, an optimized high performance liquid chromatography-fluorescence detector (HPLC-FL) method for the determination of benzo[a]pyrene in edible oil was established. HPLC was performed with Thermo Fisher Scientific C18 column (250 mm×4.6 mm, 5 μm) as the chromatographic column and acetonitrile and water as the mobile phase, and the excitation wavelength and emission wavelength of fluorescence detector were 286 and 430 nm, respectively. The response was high, and the linear range was 0.5-10.0 ng/ml. The lowest limit of detection was 0.11 ng/ml, and the average recovery was 92.5%. This method is suitable for quantitative analysis of benzo[a]pyrene content in edible oil.

Energy transfer mechanism of PBS-thylakoid complexes——By time-resolved fluorescence spectra technique

IN a previous paper, we have studied the energy transfer mechanism among the PBS-thy-lakoid complex in detail by using steady-state spectra and deconvolution techniques. The ex-perimental results indicated that the energy transfer from PBS to two reaction centers of PS Ⅰand PS Ⅱ were parallel, and confirmed the model which was suggested by Mullineaxu.

TIME-RESOLVED FLUORESCENCE SPECTROSCOPY OF HEMATOPORPHYRIN DERIVATIVE LASER No. 3

Ⅰ. INTRODUCTIONPhotodynamic therapy (PDT) which utilizes hematoporphyrin derivative (HpD) as a photosensitizing drug has increasingly being used for the local treatment of malignant tumors. The success of this method is attributed to the ability of HpD to accumulate to

STEADY-STATE AND TIME-RESOLVED FLUORESCENCE STUDY OF TRIPLE EXCIPLEX IN THE SYSTEM OF POLYACENAPHTHALENE AND TEREPHTHALIC DIMETHYLESTER

Triple exciplex formed between polyacenaphthalene and terephthalic dimethylester （TDE） has been studied by means of the steady-state and time-resolved fluorescence spectra. The theoretical model of the triple exciplex formation for a flexible polymer chain in a dilute solution has been proposed. The fluorescence decays of the monomer, the exciplex and the triple exciplex obey a double exponential rule in the pbotophysical processes of the triple exciplex formation. The association rate constant of the exciplex formation is k3=6.0×109s-1（mol/L）-1; the association rate constant of the triple exciplex formation is k6=5.2×107s-1. A mechanism for the triple exciplex formation from the exciplex to the triple exciplex has been proved through the noncrystal films corresponding to the same concentrations of the solution systems and the fluorescence lifetimes of the intramolecular excimer.

TIME-RESOLVED FLUORESCENCE STUDY OF TRIPLE EXCIPLEX FORMED IN THE SYSTEM OF POLY(2-VINYL) NAPHTHALENE AND TEREPHTHALIC DIMETHYLESTER

An intramolecular excimer of poly（2- vinyl） naphthalene was formed by non-adjacentchromophores interaction, then a triple exciplex was formed by interaction with the acceptormolecule further in dilute solution. The lifetime of the intramolecular excimer of poly（2-vinyl） naphthalene, τ2 = 18.83 ns and the rate constant for the triple exciplex formation,k7 = 4. 18× 109 （mol/L）-1s-1, under diffusion-control were measured. An excimer or anexciplex could be an intermediate of the triple exciplex formation. A theoretical model ofthe triple exciplex formation is proposed.

Indocyanine green fluorescence in gastrointestinal surgery:Appraisal of current evidence

Applying indocyanine green(ICG)fluorescence in surgery has created a new dimension of navigation surgery to advance in various disciplines.The research in this field is nascent and fragmented,necessitating academic efforts to gain a comprehensive understanding.The present review aims to integrate diverse perspectives and recent advances in its application in gastrointestinal surgery.The relevant articles were selected by using the appropriate keyword search in PubMed.The angiography and cholangiography property of ICG fluorescence is helpful in various hepatobiliary disorders.In gastroesophageal and colorectal surgery,the lymphangiography and angiography property of ICG is applied to evaluate bowel vascularity and guide lymphadenectomy.The lack of objective parameters to assess ICG fluorescence has been the primary limitation when ICG is used to evaluate bowel perfusion.The optimum dose and timing of ICG administration need to be standardized in some new application areas in gastrointestinal surgery.Binding tumor-specific ligands with fluorophores can potentially widen the fluorescence application to detect primary and metastatic gastrointestinal tumors.The narrative review outlines prior contributions,limitations,and research opportunities for future studies across gastrointestinal sub-specialty.The findings of the present review would be helpful for scholars and practitioners to explore and progress in this exciting domain of gastrointestinal surgery.

From static to dynamic:live observation of the support system after ischemic stroke by two photon-excited fluorescence laser-scanning microscopy

Ischemic stroke is one of the most common causes of mortality and disability worldwide.However,treatment efficacy and the progress of research remain unsatisfactory.As the critical support system and essential components in neurovascular units,glial cells and blood vessels(including the bloodbrain barrier)together maintain an optimal microenvironment for neuronal function.They provide nutrients,regulate neuronal excitability,and prevent harmful substances from entering brain tissue.The highly dynamic networks of this support system play an essential role in ischemic stroke through processes including brain homeostasis,supporting neuronal function,and reacting to injuries.However,most studies have focused on postmortem animals,which inevitably lack critical information about the dynamic changes that occur after ischemic stroke.Therefore,a high-precision technique for research in living animals is urgently needed.Two-photon fluorescence laser-scanning microscopy is a powerful imaging technique that can facilitate live imaging at high spatiotemporal resolutions.Twophoton fluorescence laser-scanning microscopy can provide images of the whole-cortex vascular 3D structure,information on multicellular component interactions,and provide images of structure and function in the cranial window.This technique shifts the existing research paradigm from static to dynamic,from flat to stereoscopic,and from single-cell function to multicellular intercommunication,thus providing direct and reliable evidence to identify the pathophysiological mechanisms following ischemic stroke in an intact brain.In this review,we discuss exciting findings from research on the support system after ischemic stroke using two-photon fluorescence laser-scanning microscopy,highlighting the importance of dynamic observations of cellular behavior and interactions in the networks of the brain’s support systems.We show the excellent application prospects and advantages of two-photon fluorescence laser-scanning microscopy and predict future research developments and directions in the study of ischemic stroke.

Molecular fluorescence significantly enhanced by gold nanoparticles@zeolitic imidazolate framework-8

Noble metal nanoparticles exhibit unique surface plasmon resonance dependent optical properties.On this basis,gold nanoparticles(AuNPs)encapsulated in metal–organic frameworks(MOFs)can form AuNPs@MOFs composites to modulate the optical properties of fluorescent molecules,which is less reported.In this paper,based on the fluorescence enhancement effect of AuNPs on 2-(2-hydroxyphenyl)-1H-benzimidazole(HPBI)molecules,zeolitic imidazolate framework-8(ZIF-8)crystals with structural stability were introduced.AuNPs@ZIF-8 exhibited a significantly pronounced fluorescence enhancement of the HPBI molecules.In addition,by comparing the fluorescence characteristics of the HPBI molecules adsorbed on AuNPs@ZIF-8 and those captured in AuNPs@ZIF-8,we found that the ZIF-8 can act as a spacer layer with highly effective near-field enhancement.All our preliminary results shed light on future research on the composite structures of noble metal particles and MOFs for fluorescent probes and sensing applications.

Experimental Study on Ultrasonic Cavitation Intensity Based on Fluorescence Analysis

The Ultrasonic cavitation effect has been widely used in mechanical engineering,chemical engineering,biomedicine,and many other fields.The quantitative characterization of ultrasonic cavitation intensity has always been a difficulty.Based on this,a fluorescence analysis method has been adopted to explore ultrasonic cavitation intensity in this paper.In the experiment of fluorescence intensity measurement,terephthalic acid(TA)was used as the fluorescent probe,ultrasonic power,ultrasonic frequency,and irradiation time were independent variables,and fluorescence intensity and fluorescence peak area were used as experimental results.The collapse of cavitation bubble will cause molecular bond breakage and release·OH,and the non-fluorescent substance TA will form the strong fluorescent substance TAOH with·OH.The spectra of the treated samples were measured by a F-7000 fluorescence spectrophotometer.The results showed that the fluorescence intensity and fluorescence peak area increased rapidly after ultrasonic cavitation treatment,and then increased slowly with the increase of ultrasonic power,which gradually increased with the increase of irradiation time.They first decreased and then increased with the increase of ultrasonic frequency from 20 kHz to 40 kHz.The irradiation time was the most influential factor,and the cavitation intensity of low frequency was higher overall.The fluorescence intensity and fluorescence peak area of the samples increased by 2-20 times after ultrasonic treatment,which could increase from 69 and 5238 to 1387 and 95451,respectively.After the irradiation time exceeded 25 min,the growth rate of fluorescence intensity slowed down,which was caused by the decrease of gas content and TA concentration in the solution.The study quantitatively characterized the cavitation intensity,reflecting the advantages of fluorescence analysis,and provided a basis for the further study of ultra-sonic cavitation.

Construction of Fluorescence Sensing Platform on the Basis of Carbon Nitride Nanosheet for the Detection of Interferon-γ

Purpose: Interferon-γ (INF-γ) is a cytokine that participates in the immune reaction of the body. Its level of secretion can reflect the immune response condition after the body is infected by pathogens, which is a significant indication of clinically-related diseases. Therefore, it is of great significance in application to develop a fluorescence biosensor to inspect INF-γ with rapidness, high sensitivity and high practicability. Method: The fluorescence sensor is made on the basis of the two-dimensional nano-material namely Carbon Nitride Nanosheet (CNNS) and the Aptamer probe to identify INF-γ (Apt®INF-γ). CNNS can quickly quench the Cy5 fluorescent dye modified on the Apt®INF-γ probe due to the Photoinduced Electron Transfer (PET), but when the INF-γ exists, Apt®INF-γ specifically identifies and combines it. The complex of Apt®INF-γ and INF-γ is away from CNNS, which can effectively block the fluorescent signal of Apt?INF-γ being quenched by CNNS. Result: The sensitive detection of IFN-γ protein can be achieved through the application of CNNS/Apt®INF-γ fluorescence sensing platform. In this method, the intensity of the fluorescent signal is positively correlated with the concentration of IFN-γ, of which the liner response range is 0.5 - 100 ng/mL and the limit of detection is 0.303 ng/mL. In addition, this fluorescence sensing platform has the advantages of high specificity, simple operation and low costs. It can inspect the content of IFN-γ in clinical serum samples without interference. The actual recovery rate of serum samples is 97.11% - 106.96%. Conclusion: Therefore, the CNNS/Apt®INF-γ sensing platform is expected to be implemented in the actual clinical detection, also conducive to developing a universal fluorescence biosensor to inspect other target materials.