Journal of Fluorescence (v.22, #2)
FITC Labeled Silica Nanoparticles as Efficient Cell Tags: Uptake and Photostability Study in Endothelial Cells
by Srivani Veeranarayanan; Aby Cheruvathoor Poulose; Sheikh Mohamed; Athulya Aravind; Yutaka Nagaoka; Yasuhiko Yoshida; Toru Maekawa; D. Sakthi Kumar (pp. 537-548).
The use of fluorescent nanomaterials has gained great importance in the field of medical imaging. Many traditional imaging technologies have been reported utilizing dyes in the past. These methods face drawbacks due to non-specific accumulation and photobleaching of dyes. We studied the uptake and internalization of two different sized (30 nm and 100 nm) FITC labeled silica nanoparticles in Human umbilical vein endothelial cell line. These nanomaterials show high biocompatability and are highly photostable inside live cells for increased period of time in comparison to the dye alone. To our knowledge, we report for the first time the use of 30 nm fluorescent silica nanoparticles as efficient endothelial tags along with the well studied 100 nm particles. We also have emphasized the good photostability of these materials in live cells.
Keywords: Fluorescent silica nanoparticles; Photobleaching; Photostability; Cell tags; Human umbilical vein endothelial cell; Endothelial cell imaging
Spectrofluorimetric Determination of Aliskiren in Tablets and Spiked Human Plasma through Derivatization with Dansyl Chloride
by Zeynep Aydoğmuş; Ferhat Sarı; Sevgi Tatar Ulu (pp. 549-556).
A simple and sensitive method has been developed and validated for the determination of aliskiren (ALS) in its dosage forms and spiked plasma. The method was based on the reaction of the drug with dansyl chloride in the presence of bicarbonate solution of pH 10.5 to give a highly fluorescent derivative which was measured at 501 nm with excitition at 378 nm in dichloromethane. Different experimental parameters affecting the development of the method and stability were carefully studied and optimized. The calibration curves were linear over the concentration ranges of 100–700 and 50–150 ng/mL for standard solution and plasma, respectively. The limits of detection were 27.52 ng/mL in standard solution, 4.91 ng/mL in plasma. The developed method was successfully applied to the analysis the drug in the commercial tablets and spiked plasma samples. The mean recovery of ALS from tablets and plasma was 100.10 and 97.81%, respectively. A proposal of the reaction pathway was presented.
Keywords: Aliskiren; Dansyl chloride; Spectrofluorimetry; Tablets; Spiked plasma
Determination of Ofloxacin using a Highly Selective Photo Probe Based on the Enhancement of the Luminescence Intensity of Eu3+—Ofloxacin Complex in Pharmaceutical and Serum Samples
by M. S. Attia; Amr A. Essawy; A. O. Youssef; Marwa S. Mostafa (pp. 557-564).
A rapid, simple and sensitive spectrofluorimetric method for determination of trace amount of ofloxacin was developed. At pH 5.1 the ofloxacin enhances the luminescence intensity of the Eu3+ ion in Eu3+- ofloxacin complex at λex = 365 nm. The produced luminescence intensity of Eu3+-ofloxacin complex was in proportional to the concentration of ofloxacin. The working range for the determination of ofloxacin was 5.0 × 10-9–5.0 × 10-6 mol L-1 with lower detection limit (LOD) and quantitative detection limit (QDL) of 3 × 10-9 and 9 × 10-9 mol L-1, respectively. The enhancement mechanism of the luminescence intensity in the Eu3+-ofloxacin system has been also explained. The method revealed good selectivity for ofloxacin in the presence of coexisting substances and used successfully for the assay of ofloxacin in pharmaceutical preparations and serum. A comparison with other standard methods was also discussed.
Keywords: Ofloxacin; Europium; Luminescence; Enhancement; Energy transfer; Photo probe
A New Piezochromic Fluorescence and Aggregation-Induced Emission Compound Containing Tetraphenylethylene and Triphenylamine Moieties with Morphology-alterable Property
by Xie Zhou; Hai-yin Li; Zhen-guo Chi; Bing-jia Xu; Xi-qi Zhang; Yi Zhang; Si-wei Liu; Jia-rui Xu (pp. 565-572).
A novel piezochromic fluorescent (PCF) compound with aggregation-induced emission (AIE) effect and morphology-alterable emission property was developed. The amorphous and crystalline aggregates were obtained, and their spectroscopic properties and morphological structures were reversibly and repeatedly exhibited upon pressing (fuming) or annealing. The piezochromic fluorescent nature was generated through crystalline-amorphous phase transformation. It was proposed that AIE compounds existing a twisted propeller-shaped conformation will exhibit PCF activity. The common relationship betweeen AIE and PCF established will guide researchers in identifying and synthesizing more piezochromic fluorescent materials.
Keywords: Piezochromic fluorescence; Morphology-alterable emission; Phase transformation; Tetraphenylethylene; Aggregation-induced emission
Studies on Calcium Release and H2O2 Level Produced by the Elicitor Induced Plant Cell by Fluorescence Probing
by Quan Gan; Bin Jia; Xiao Liu; Yizhu Zhang; Manxi Liu (pp. 573-581).
Using fluorescence probing technology, we studied the mechanism and interrelations of calcium release and H2O2 production in situ in living tissues of tobacco and cotton plants which were induced by pathogen elicitor, salicylic acid (SA) and pectinase respectively. Results showed that (1) pathogen elicitors could induced H2O2 response in epidermis cells regardless of environmental calcium, but in mesophyll protoplast, H2O2 response could only be induced at calcium condition. Similarly, SA and pectinase induced H2O2 response could only be observed at calcium condition; (2) pathogen elicitors could induce calcium response in both epidermis cells and protoplasts regardless of environmental calcium, while calcium response couldn’t be induced at non-calcium condition by SA and pectinase; (3) H2O2 response and calcium response in protoplast were faster than that in the whole cell. These results indicated that pathogen elicitors can induce the release of cell wall calcium and the cell wall calcium release is independent to pectinase. And it is concluded that free calcium influx is necessary for the oxidative burst and cell wall calcium has an irreplaceable role in defense signal transduction.
Keywords: Calcium; Cotton; Hydrogen peroxide; Pathogen elicitor
The Role of Intermolecular Interactions in Solid State Fluorescent Conjugated Polymer Chemosensors
by Sherryllene S. Pinnock; Catherine N. Malele; Justin Che; Wayne E. Jones Jr. (pp. 583-589).
A functionalized fluorescent conjugated polymer, tolylterpyridine poly(p-phenyleneethynylene-thienyleneethynylene (ttp-PPETE), was designed and synthesized to detect trace amounts of toxic transition metal pollutants in ground water. Photophysical studies in tetrahydrofuran (THF) successfully demonstrated this polymer as a selective and sensitive chemosensor for Ni2+ and Co2+ in aqueous solution. Solid state composites of these chemosensors have now been prepared which can be modified to provide for inexpensive and portable field based chemical detection. A solid composite of ttp-PPETE, blended with poly (methyl methacrylate) shows UV–vis absorption and fluorescence emission spectra which are red- shifted when compared to solution phase spectra, suggesting an increase in conjugation in the solid state. An additional absorption peak, not present in solution, is also observed in the solid state. The presence of this new peak provides evidence of interacting FCP chains in the solid state. Concentration dependent experiments were done on the solid composite showing red-shifted emission peaks accompanied by a significant reduction in the fluorescent quantum yield. These observations are consistent with the formation of aggregated polymer species in the solid state. Intermolecular interactions of this type can be manipulated in the design of sensitive and selective solid state fluorescent conjugated polymer sensors.
Keywords: Chemosensors; Aggregation; Solid state; Intermolecular interactions
Determination of Paracetamol Based on its Quenching Effect on the Photoluminescence of CdTe Fluorescence Probes
by Li Li; Yaxiang Lu; Yaping Ding; Yu Cheng; Wanchen Xu; Fenfen Zhang (pp. 591-596).
L-Cysteine capped CdTe nanoparticles (NPs) were synthesized in aqueous medium, and their application as fluorescence probes in the determination of paracetamol was studied. The L-cysteine capped CdTe NPs were characterized by transmission electron microscopy, X-ray diffraction spectrometry, spectrofluorometry, ultraviolet-visible and Fourier transform infrared spectrometry. Based on the distinct fluorescence quenching of CdTe fluorescence probes in the presence of paracetamol, a simple, rapid and specific method for paracetamol determination was presented. Under optimum conditions, the relative fluorescence intensity of CdTe NPs was linearly proportional to paracetamol concentration from 1.0 × 10−8 mol/L to 1.6 × 10−7 mol/L with a detection limit of 4.2 × 10−9 mol/L. The proposed method was applied to detect paracetamol in commercial tablets with satisfactory results.
Keywords: CdTe nanoparticles; Fluorescence probe; Paracetamol
Studies on Curcumin and Curcuminoids. XLVI. Photophysical Properties of Dimethoxycurcumin and Bis-dehydroxycurcumin
by L. Nardo; A. Andreoni; M. Bondani; M. Másson; T. Haukvik; H. H. Tønnesen (pp. 597-608).
The steady-state absorption and fluorescence, as well as the time-resolved fluorescence properties of dimethoxycurcumin and bis-dehydroxycurcumin dissolved in several solvents differing in polarity and H-bonding capability are presented. The singlet oxygen generation efficiency of the two compounds relative to curcumin is estimated. The photodegradation quantum yield of the former compound in acetonitrile and methanol is determined. The dimethoxycurcumin and bis-dehydroxycurcumin decay mechanisms from the S 1 state are discussed and compared with those of curcumin, dicinnamoylmethane and bis-demethoxycurcumin.
Keywords: Curcuminoid; Fluorescence decay mechanisms; Intramolecular hydrogen bonding; Solute-solvent interactions; Excited state intramolecular proton transfer
Nanosphere Templated Metallic Grating Assisted Enhanced Fluorescence
by Ravi Kumar Kannadorai; U. S. Dinish; Chit Yaw Fu; Gopalkrishna Hegde; Malini Olivo; Anand Asundi (pp. 609-614).
In this paper, enhanced fluorescence from a silver film coated nanosphere templated grating is presented. Initially, numerical simulation was performed to determine the plasmon resonance wavelength by varying the thickness of the silver film on top of a monolayer of 400 nm nanospheres. The simulation results are verified experimentally and tested for enhancing fluorescence from fluorescein isothiocyanate whose excitation wavelength closely matches with the plasmon resonance wavelength of the substrate with 100 nm silver film over nanosphere. The 12 times enhancement in the intensity is attributed to the local field enhancement in addition to the excitation of surface plasmon polaritons along the surface.
Keywords: Metal enhanced fluorescence; Surface plasmons; Nanosphere monolayer; Finite-difference time domain method
Quantitative Determination of Proteins Based on Strong Fluorescence Enhancement in Curcumin-Chitosan-Proteins System
by Feng Wang; Wei Huang; Lingyan Jiang; Bo Tang (pp. 615-622).
We found that the fluorescence intensity of curcumin (CU) can be highly enhanced by protein bovine serum albumin (BSA) and human serum albumin (HSA) in the presence of chitosan (CTS). Based on this finding, a new fluorimetric method to determine the concentration of protein was developed. Under optimized conditions, the enhanced intensities of fluorescence are quantitatively in proportion to the concentrations of protein in range of 0.007–100 μg·mL−1 for BSA and 0.004–100 μg·mL−1 for HSA at 426 nm excitation, and 0.007–100 μg·mL−1 for BSA and 0.01–100 μg·mL−1for HSA at 280 nm excitation, while corresponding qualitative detection limits (S/N = 3) can lower to 3.96, 2.46, 4.56, 9.20 ng·mL−1, respectively. The method has been successfully used for the determination of HSA in real samples. Based on resonance light scattering and UV-visible absorption spectroscopic analysis, mechanism studies suggested that the highly enhanced fluorescence of CU was resulted from synergic effects of favorable hydrophobic microenvironment provided by BSA and CTS and efficient intermolecular energy transfer between BSA and CU. Protein BSA may bind to CTS through hydrogen bonds, which causes the protein conformation to convert from β-fold to α-helix. CU can combine with the BSA-CTS complex through its center carbonyl carbon, and CTS plays a key role in promoting the energy transfer process by shortening the distance between BSA and CU.
Keywords: Curcumin (CU); Chitosan (CTS); Protein; Fluorescence
Water Deficit and Salt Stress Diagnosis Through LED Induced Chlorophyll Fluorescence Analysis in Jatropha curcas L.
by E. A. Silva Jr; A. S. Gouveia-Neto; R. A. Oliveira; D. S. Moura; P. C. Cunha; E. B. Costa; T. J. R. Câmara; L. G. Willadino (pp. 623-630).
LED induced chlorophyll fluorescence analysis is employed to investigate the effect of water deficit and salt stress upon the growth process of Jatropha curcas L.. Red(Fr) and far-red(FFr) chlorophyll fluorescence around 685 nm and 735 nm, respectively, were observed and examined as a function of the stress intensity(salt concentration and water deficit). The fluorescence ratio Fr/FFr which is a valuable nondestructive and nonintrusive indicator of the chlorophyll content of leaves was exploited to monitor the jatropha plants under stress. The data indicated that salinity plays a minor role in the chlorophyll concentration of leaves for NaCl concentrations in the 25 to 200 mM range. The fluorescence ratio also permitted the detection of damage caused by water deficit in the early stages of the plants growing process. A significant variation of the Fr/FFr ratio was observed in the first 10 days of the experiment, and before signs of visual stress became apparent. The results suggest that the Fr/FFr ratio is an early-warning indicator of water deficit stress
Keywords: Fluorescence; Chlorophyll; Abiotic-stress; Jatropha curcas; Biofuel; Water; Salt
Synthesis, Photo- and Electro-Luminescence of 3-Benzoxazol-2-yl-Coumarin Derivatives
by Yuling Zhao; Tianzhi Yu; Youzhi Wu; Hui Zhang; Duowang Fan; Zunwei Gan; Liangliang Yang; Xiaoqian Han; Yumei Zhang (pp. 631-638).
Two coumarin derivatives containing electron-transporting benzoxazolyl moiety, 7-(diethylamino)-3-(benzoxazol-2-yl)coumarin (DABOC) and 3-(benzoxazol-2-yl)benzo[5,6]coumarin (BOBC), were synthesized and characterized. The photoluminescence and electroluminescence of the compounds were investigated detailedly. The compounds exhibited strong blue-green emissions in both solution and solid states, but the devices with DABOC as the emitting layer exhibited orange emission and maximum luminous efficiency of 2.8 cd/A and maximum luminance of 8,800 cd/m2, and the devices with BOBC displayed orange-white emission and maximum luminous efficiency of 0.13 cd/A and maximum luminance of 540 cd/m2.
Keywords: Synthesis; UV-vis Absorption; Photoluminescence; Electroluminescence; Coumarin derivative; Benzoxazolyl derivative
Synthesis of Novel Eu(III) Luminescent Probe Based on 9- Acridinecarboxylic Acid Skelton for Sensing of ds-DNA
by Hassan A. Azab; Belal H. M. Hussein; Abdullah I. El-Falouji (pp. 639-649).
Eu(III)-9-acridinecarboxylate (9-ACA) complex was synthesized and characterized by elemental analysis, conductivity measurement, IR spectroscopy, thermal analysis, mass spectroscopy, 1H-NMR, fluorescence and ultraviolet spectra. The results indicated that the composition of this complex is [Eu(III)-(9-ACA)2(NCS)(C2H5OH)2] 2.5 H2O and the oxygen of the carbonyl group coordinated to Eu(III). The interaction between the complex with nucleotides guanosine 5′- monophosphate (5′-GMP), adenosine 5′-diphosphates (5′-ADP), inosine (5′-IMP) and CT-DNA was studied by fluorescence spectroscopy. The fluorescence intensity of Eu(III)-9-acridinecarboxylate complex was enhanced with the addition of CT-DNA. The effect of pH values on the fluorescence intensity of Eu(III) complex was investigated. Under experimental conditions, the linear range was 9–50 ng mL−1 for calf thymus DNA (CT- DNA) and the corresponding detection limit was 5 ng mL−1. The results showed that Eu(III)-(9-ACA)2 complex binds to CT-DNA with stability constant of 2.41 × 104 M .
Keywords: Eu(III)-9-acridinecarboxylate; Luminescent probe; ds- DNA; Nucleotides
Syntheses and Fluorescence Properties of Two Novel Lanthanide (III) Perchlorate Complexes with Bis(benzylsulfinyl)methane
by Wen-Xian Li; Ying-Jie Li; Wen-Juan Chai; Tie Ren; Yu Liu; Jing Zhang; Bo-Yang Ao (pp. 651-658).
A novel ligand with double sulfinyl groups, bis(benzylsulfinyl)methane, was synthesized by a new method and its two lanthanide (III) complexes were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR, TG-DSC, 1HNMR and UV spectra. The results indicated that the composition of these complexes was REL2.5(ClO4)3·3H2O (RE = Tb (III), Dy (III), L = C6H5CH2SOCH2SOCH2C6H5). The FT-IR results revealed that the perchlorate group was bonded with the lanthanide ion by the oxygen atoms, and the coordination was bidentate. The fluorescent spectra illustrated that both the Tb (III) and Dy (III) complexes displayed characteristic fluorescence in solid state, especially for the Tb (III) complex, the peak of 5D4 → 7 F5 of the Tb (III) ion in 544 nm was stronger than that of others. It indicated that the Tb (III) complex could emit purer green fluorescence. By analysis fluorescence and phosphorescence spectra, it was found that the ligand had the advantage to absorb energy and transfer it to the Tb (III) and Dy (III) ions. The phosphorescence spectra and fluorescence lifetimes of the complexes were also measured.
Keywords: Rare earth complexes; Bis(benzylsulfinyl)methane; Fluorescence; Phosphorescence
Fluorescence and Electrochemical Sensing of Pesticides Methomyl, Aldicarb and Prometryne by the Luminescent Europium-3-Carboxycoumarin Probe
by Hassan A. Azab; Axel Duerkop; E. M. Mogahed; F. K. Awad; R. M. Abd El Aal; Rasha M. Kamel (pp. 659-676).
This work describes the application of time resolved fluorescence in microtiterplates and electrochemical methods on glassy carbon electrode for investigating the interactions of europium-3-carboxycoumarin with pesticides aldicarb, methomyl and prometryne. Stern-volmer studies at different temperatures indicate that static quenching dominates for methomyl, aldicarb and prometryne. By using Lineweaver-Burk equation binding constants were determined at 303 K, 308 K and 313 K. A thermodynamic analysis showed that the reaction is spontaneous with ΔG being negative. The enthalpy ΔH and the entropy ΔS of reactions were all determined. A time-resolved (gated) luminescence-based method for determination of pesticides in microtiterplate format using the long-lived europium-3-carboxycoumarin has been developed. The limit of detection is 4.80, 5.06 and 8.01 μmol L−1 for methomyl, prometryne and aldicarb, respectively. This is the lowest limit of detection achieved so far for luminescent lanthanide-based probes for pesticides. The interaction of the probe with the pesticides has been investigated using cyclic voltammetry (CV), differential pulse polarography (DPP), square wave voltammetry (SWV) and linear sweep voltammetry (LSV) on a glassy carbon electrode in I = 0.1 mol L−1 p-toluenesulfonate at 25 °C. The diffusion coefficients of the reduced species are calculated. The main properties of the electrode reaction occurring in a finite diffusion space are the quasireversible maximum and the splitting of the net SWV peak for Eu(III) ions in the ternary complex formed . It was observed that the increase of the cathodic peak currents using LSV is linear with the increase of pesticides concentration in the range 5 × 10−7 to 1 × 10−5 mol L−1. The detection limit (DL) were about 1.01, 2.23 and 1.89 μmolL−1 for aldicarb, methomyl and prometryne, respectively. In order to assess the analytical applicability of the method, the influence of various potentially interfering species was examined. Influence of interfering species on the recovery of 10 μmol L−1 pesticides has been investigated.
Keywords: Europium-3-carboxycoumarin; Time resolved fluorescence; Pesticides aldicarb; Methomyl; Prometryne; Cyclic voltammetry; Differential pulse voltammetry; Linear sweep voltammetry; Glassy carbon electrode
Fluorescent Studies of Salicylaldehyde and Other Related Carbonyl Compounds for the Selective and Sensitive Detection of Zinc(II) Ions in Aqueous Solution
by Soleiman Hisaindee; Osama Zahid; Mohammed A. Meetani; John Graham (pp. 677-683).
Salicylaldehyde was found to have a high selectivity for zinc ions with simultaneous enhancement of fluorescence in aqueous buffer solution at optimum pH 8.5. The stoichiometry of the complex was determined to be 1:1 with a K a value of 3.4 × 104 M−1 at 298 K. The fluorescence of the complex is not affected by common anions and Zn2+ binds preferentially to salicylaldehyde in the presence of alkali, alkaline earth and heavy metal cations (Hg2+, Cd2+, Cr3+ and Ni2+). This property is not observed with related phenolic compounds bearing a carbonyl group such as esters, amides, carboxylic acids and ketones.
Keywords: Salicylaldehyde; Zinc; Fluorescence; Selectivity; Metal ions
Investigation and Development of Quantum Dot-Encoded Microsphere Bioconjugates for DNA Detection by Flow Cytometry
by Sarah Thiollet; Séamus Higson; Nicola White; Sarah L. Morgan (pp. 685-697).
The development of screening assays continues to be an active area of research in molecular diagnostics. Fluorescent microspheres conjugated to biomarkers (nucleic acids, proteins, lipids, carbohydrates) and analyzed on flow cytometer instruments offered a new approach for multiplexed detection platform in a suspension format. Quantum dots encoded into synthetic microspheres have the potentials to improve current screening bioassays and specifically suspension array technology. In this paper, commercialized quantum dot-encoded microsphere were evaluated and optimized as fluorescent probes to address some of the limitations of suspension array technologies. A comprehensive study was undertaken to adapt the bioconjugation procedure to the quantum dot-encoded microsphere structural and optical properties. Both the leaching-out of quantum dots and microspheres degradation under bioconjugation experimental conditions were minimized. A rapid, efficient and reproducible conjugation method was developed for the detection of single-stranded DNA with the commercialized quantum dot-encoded microsphere. Approximately ten thousand microspheres were conjugated to short amino-modified DNA sequences in one hour with high efficiency. The bioconjugated microspheres acting as fluorescent probes successfully detected a DNA target in suspension with high specificity. Quantum dot-encoded microsphere commercial products are limited which strongly prevents reproducible and comparative studies between laboratories. The method developed here contributes to the understanding of quantum dot-encoded microsphere reactivity, and to the optimization of adapted experimental procedure. This step is essential in the development of this new fluorescent probe technology for multiplex genotyping assay and molecular diagnostic applications.
Keywords: Quantum dot-encoded microsphere; Flow cytometry; Bioconjugation; Suspension array technology
In vivo Monitoring of Organ-Selective Distribution of CdHgTe/SiO2 Nanoparticles in Mouse Model
by Haiyan Chen; Sisi Cui; Zhenzhen Tu; Yueqing Gu; Xuemei Chi (pp. 699-706).
CdHgTe/SiO2 nanoparticles were prepared by SiO2 capping on the surface of CdHgTe QDs. The characteristics, such as optical spectra, photostability, size and cell toxicity were investigated. The dynamic distribution of CdHgTe/SiO2 nanoparticles was in vivo monitored by near infrared fluorescence imaging system. CdHgTe/SiO2 nanoparticles acted as a novel fluorescence probe have a maximum fluorescence emission of 785 nm and high photo-stability. The hydrodynamic diameter of CdHgTe/SiO2 nanoparticles could be adjusted to 122.3 nm. Compared to CdHgTe QDs, inhibitory effects of CdHgTe/SiO2 nanoparticles on proliferation of HCT116 cells decreased to a certain extent. CdHgTe/SiO2 nanoparticles had their specific dynamic distribution behavior, which provided new perspectives for bio-distribution of nanoparticles.
Keywords: CdHgTe/SiO2 ; Nanoparticles; Organ selective; Bio-distribution; Near infrared
Influence of Substituent and Solvent on the Radiative Process of Singlet Excited States of Novel Cyclic Azacyanine Derivatives
by Digambara Patra; Nagham N. Malaeb; Makhluf J. Haddadin; Mark J. Kurth (pp. 707-717).
The photophysical properties of novel cyclic azacyanine derivatives have been investigated in acetonitrile, N-butyronitrile, methanol, ethanol, DMF and water. Introduction of electron donating or accepting groups on the cyclic azacyanine has a direct impact on the spectroscopic and photophysical properties. Irrespective of the nature of the substitution, azacyanine shows a general solvent relaxation in accordance with Lippert-Mataga’s prediction; however, in protic solvent, specific interactions are encountered. Fluorescence lifetime decay suggests a relaxation in the nanosecond time scale with monoexponential decay in polar solvents and biexponential decay in non polar solvents. The fluorescence lifetime of azacyanines are found to be longer than popular cy3 dyes. An electron donating substituent increases the fluorescence lifetime and influences the radiative process, whereas an electron withdrawing group marginally increases the excited state lifetime but remarkably enhances the radiative process. The fluorescence quantum yield of substituted cyclic azacyanine in water is noted to be at least five fold higher than the popular cy3 dye.
Keywords: Cyclic Azocyanine; Solvent effect; Substituent effect; Excited state process; Fluorescence lifetime, Radiative process
Development of Novel Nanocarrier-Based Near-Infrared Optical Probes for In Vivo Tumor Imaging
by Yoichi Shimizu; Takashi Temma; Isao Hara; Ryo Yamahara; Ei-ichi Ozeki; Masahiro Ono; Hideo Saji (pp. 719-727).
Optical imaging with near-infrared (NIR) fluorescent probes is a useful diagnostic technology for in vivo tumor detection. Our plan was to develop novel NIR fluorophore-micelle complex probes. IC7-1 and IC7-2 were synthesized as novel lipophilic NIR fluorophores, which were encapsulated in an amphiphilic polydepsipeptide micelle “lactosome”. The fluorophore-micelle complexes IC7-1 lactosome and IC7-2 lactosome were evaluated as NIR fluorescent probes for in vivo tumor imaging. IC7-1 and IC7-2 were synthesized and then encapsulated in lactosomes. The optical properties of IC7-1, IC7-2, IC7-1 lactosome and IC7-2 lactosome were measured. IC7-1 lactosome and IC7-2 lactosome were administered to tumor-bearing mice, and fluorescence images were acquired for 48 h. IC7-1 and IC7-2 were successfully synthesized in 12% and 6.3% overall yield, and maximum emission wavelengths in chloroform were observed at 858 nm and 897 nm, respectively. Aqueous buffered solutions of IC7-1 lactosome and IC7-2 lactosome showed similar fluorescence spectra in chloroform and higher or comparable quantum yields and higher photostability compared with ICG. Both lactosome probes specifically visualized tumor tissue 6 h post-administration. IC7-1 lactosome and IC7-2 lactosome could be promising NIR probes for in vivo tumor imaging.
Keywords: Optical; Near-infrared; Micelle; Molecular imaging
Photophysical Properties of Ternary RE3+ (RE = Eu, Tb, Sm) Hybrids with β-Diketone Functionalized Linkages and 4-(4-nitrostyryl)pyridine Though Coordination Bonding
by Yan-Yan Li; Bing Yan; Lei Guo (pp. 729-736).
In this paper, the organic ligands TTA and TAA are grafted onto the coupling agent to achieve the organic precursors (TTA-Si, TAA-Si) as first ligand and the organic 4-(4-nitrostyryl)pyridine (Nspy) is synthesized as the second ligand. Both of them are coordinated to the rare ions with the carbonyl group and nitrogen atom respectively. After the hydrolysis and copolycondensation between the teraethoxysilane (TEOS) and the ternary rare earth organic complex via the sol–gel process, the chemical bonded hybrid materials are constructed and characterized in detail. The obtained hybrid materials present superior thermal stabilities and regular and homogenous square blocks microstructure. Among the hybrids Eu(TTA-Si)3Nspy shows a more strong characteristic emission and longer lifetime than the hybrids Eu(TAA-Si)3Nspy, while hybrids Tb(TAA-Si)3Nspy exhibits the stronger characteristic emission and longer lifetime than the hybrids Tb(TTA-Si)3Nspy. For Sm3+ hybrid materials, the photoluminescence of Sm(TAA-Si)3Nspy is too weak to find in the characteristic emission spectra, meanwhile, Sm(TTA-Si)3Nspy has the excellent luminescent intensity.
Keywords: Rare earth ion; Hybrid materials; Luminescence; Photophysical property
Kamlet-Taft and Catalan Studies of Some Novel Y-Shaped Imidazole Derivatives
by J. Jayabharathi; V. Thanikachalam; K. Brindha Devi; M. Venkatesh Perumal (pp. 737-744).
Some novel Y-shaped imidazole derivatives were developed and characterized by NMR and mass spectral techniques. The photophysical properties of these imidazole derivatives were studied in several solvents. The Kamlet-Taft and Catalan’s solvent scales were found to be the most suitable for describing the solvatochromic shifts of the absorption and fluorescence emission. The adjusted coefficient representing the electron releasing ability or basicity of the solvent, C β or C SB has a negative value, suggesting that the absorption and fluorescence bands shift to lower energies with the increasing electron-donating ability of the solvent. This effect can be interpreted in terms of the stabilization of the resonance structures of the chromophore. The observed lower fluorescence quantum yield may be due to an increase in the non-radiative deactivation rate constant. This is attributed to the loss of planarity in the excited state provided by the non co-planarity of the cinnamaldehyde ring attached to C(2) atom of the imidazole ring. Such a geometrical change in the excited state leads to an important Stokes shift, reducing the reabsorption and reemission effects in the detected emission in highly concentrated solutions.
Keywords: NMR; Kamlet-Taft; Catalan parameters; Aggregation
Luminescence Properties of Dual Valence Eu Doped Nano-crystalline BaF2 Embedded Glass-ceramics and Observation of Eu2+ → Eu3+ Energy Transfer
by Kaushik Biswas; Atul D. Sontakke; R. Sen; K. Annapurna (pp. 745-752).
Europium doped glass-ceramics containing BaF2 nano-crystals have been prepared by using the controlled crystallization of melt-quenched glasses. X-ray diffraction and transmission electron microscopy have confirmed the presence of cubic BaF2 nano-crystalline phase in glass matrix in the ceramized samples. Incorporation of rare earth ions into the formed crystalline phase having low phonon energy of 346 cm−1 has been demonstrated from the emission spectra of Eu3+ ions showing the transitions from upper excitation states 5DJ (J = 1, 2, and 3) to ground states for the glass-ceramics samples. The presence of divalent europium ions in glass and glass-ceramics samples is confirmed from the dominant blue emission corresponding to its 5d-4f transition under an excitation of 300 nm. Increase in the reduction of trivalent europium (Eu3+) ions to divalent (Eu2+) with the extent of ceramization is explained by charge compensation model based on substitution defect mechanisms. Further, the phenomenon of energy transfer from Eu2+ to Eu3+ ion by radiative trapping or re-absorption is evidenced which increases with the degree of ceramization. For the first time, the reduction of Eu3+ to Eu2+ under normal air atmospheric condition has been observed in a BaF2 containing oxyfluoride glass-ceramics system.
Keywords: Glasses; Transparent oxyfluoride glass ceramics; Optical probe; Eu-Luminescence
Probing the Interior of Self-Assembled Caffeine Dimer at Various Temperatures
by Soma Banerjee; Pramod Kumar Verma; Rajib Kumar Mitra; Gautam Basu; Samir Kumar Pal (pp. 753-769).
The self-assembly of non-toxic well-consumed small caffeine molecules into well-defined structures has important implications for future medical applications seeking to target the transport of small drugs in human body. Particularly, the solvation of the microenvironments of the self assembly ultimately dictates the interaction with the drug molecules and their therapeutic efficacy. We present femtosecond-resolved studies of the dynamics of aqueous solvation within self-assembled dimeric structure of caffeine molecules. We have placed small hydrophobic probes 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl) 4H-pyran (DCM), coumarin 500 (C500) into the caffeine dimer to enable spectroscopic examinations of the interior. While molecular modeling and NMR studies of the probes in the caffeine dimers reveal a well-defined location (stacked in between two caffeine molecules), dynamical light scattering (DLS), Fourier transform infrared (FTIR) spectroscopy, densimetric and sonometric experiments explore the structural evolution of the dimer upon complexation with the probes. We have extended our studies in various temperatures in order to explore structural evolution of the self assembled structure and consequently the dynamics of solvation in the interior of the dimer. Picoseconds/femtosecond resolved dynamics and the polarization gated spectroscopic studies unravel the hydration and energetics associated with activated viscous flow of the confined probes. Our studies indicate that the interior of the caffeine dimer is well-solvated; however, the dynamics of solvation is retarted significantly compared to that in bulk water, clearly revealing the dimers maintain some ordered water molecules. We have also explored the consequence of the retarded dynamics of solvation on the photo-induced electron transfer (ET) reaction of a model probe, 2-(p-toluidino) naphthalene-6-sulfonate (TNS) encapsulated in the dimer.
Keywords: Femtosecond-resolved hydration dynamics; Caffeine dimer interior; NMR spectroscopy of caffeine-TNS hetero association; TICT in caffeine dimer; Activation energy for the viscous flow
Interaction of CdTe Quantum Dots with 2,2-Diphenyl-1-Picrylhydrazyl Free Radical: A Spectroscopic, Fluorimetric and Kinetic Study
by Oluwasesan Adegoke; Wadzanai Chidawanyika; Tebello Nyokong (pp. 771-778).
The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH●) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV–vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH● radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH● may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH● is proposed.
Keywords: 2,2-Diphenyl-1-picrylhydrazine; Fluorescence quenching; Quantum dots; Thioglycolic acid
Spectrofluorimetric Assessment of Chlorzoxazone and Ibuprofen in Pharmaceutical Formulations by using Eu-Tetracycline HCl Optical Sensor Doped in Sol–Gel Matrix
by M. S. Attia; M. N. Ramsis; L. H. Khalil; S. G. Hashem (pp. 779-788).
A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol–gel matrix. The chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol–gel matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λex = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10−9–1 × 10−4 and 1 × 10−8–7 × 10−5 mol L−1, and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10−10 , 9.6 × 10−10 and 5.6 × 10−10, 1.7 × 10−9 mol L−1, respectively.
Keywords: Chlorzoxazone; Ibuprofen; Luminescence intensity; Optical sensor; Europium-tetracycline HCl complex