Single- and two-photon absorption induced photocleavage of dimeric coumarin linkers: Therapeutic versus passive photocleavage in ophthalmologic applications

Phototriggered chemical reactions are elegant and spatially selective. However, in application a general problem is that aside of the desired changes, e.g. induced by laser, undesired changes may occur, e.g. induced by daylight or sunlight. One such example which we are studying here is the phototriggered release of drugs from materials suitable for polymeric intraocular lenses (IOL). Through such an IOL sunlight needs to pass for several years without affecting the drug loading, but at the therapeutically required moment the drug release shall be triggered also by light. We studied this using a novel coumarin dimer (7,7′-[3-(tert-butyldimethylsilyloxy)propoxy]-dicoumarin) synthesized from the monomer in a photochemical [2π + 2π] cycloaddition reaction. The cleavage of the obtained photodimer by single-photon (SPA) and two-photon absorption (TPA) excitation was investigated in acetonitrile solution and in polymethylmethacrylate in order to exclude major matrix entrapment effects. The cleavage quantum yields and TPA cross-section were determined to be Φ ≈ 0.13 and δ_TPA ≈ 2.7 GM, respectively. It was found that 10% undesired drug release would require more than 16 years of continuous exposure to sunlight. Release of 90% of drug under therapeutic conditions would be completed within seconds. This shows that photochemically triggered drug release is capable to become a powerful tool for drug delivery in ophthalmology.     

Effects of Light Exposure and Use of Intraocular Lens on Retinal Pigment Epithelial Cells In Vitro

To investigate the effect of a blue light-filtering intraocular lens (IOL) and a UV-absorbing IOL on light-induced damage to retinal pigment epithelial (RPE) cells laden with the lipofuscin fluorophore N -retinylidene- N -retinylethanolamine (A2E), A2E-laden RPE cells were exposed to white light which was filtered by either a blue light-filtering IOL or a UV-absorbing IOL. After 30 min of illumination the cell viability and the level of reactive oxygen species (ROS), free glutathione (GSH), vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) were determined. In the absence of an IOL, the white light exposure decreased cell viability to 37.2% of the nonirradiated control. The UV-absorbing IOL tended to reduce light-induced cell death; however, the decrease was not significant. The blue light-filtering IOL significantly attenuated light-induced cell damage, increasing cell viability to 79.5% of the nonirradiated control. The presence of the blue light-filtering IOL significantly increased GSH and PEDF levels, and decreased ROS and VEGF levels. This study suggests that a blue light-filtering IOL may be more protective against A2E-induced light damage and inhibit more light-induced ROS and VEGF production than a conventional UV-absorbing IOL.     

Ftir study of hydrogen bonding and phase behaviour in poly(vinylpyridines)/poly(ethylene-CO-vinyl alcohol) blends

The specific interactions between polyvinylpyridines and ethylene-vinyl alcohol copolymers of different compositions have been studied by Fourier transform infrared spectroscopy (FTIR). Hydrogen bonding between both polymer components leads to significant spectral modification in pyridine rings spectral bands. Minor modifications in other spectral modes have been also detected. The spectral results indicate at least three competing equilibria processes in the blends: hydroxyl-hydroxyl copolymer self-association and hydroxyl-pyridine interassociation. Painter-Coleman association model was successfully applied and the phase diagram for these systems has been predicted.     

Surface Modification of Hydrophobic PMMA Intraocular Lens by the Immobilization of Hydroxyethyl Methacrylate for Improving Application in Ophthalmology

To improve application of hydrophobic polymethyl methacrylate intraocular lens (PMMA IOL) in a convenient and continuous way, 2-hydroxyethyl methacrylate (HEMA) was immobilized by dielectric barrier discharge plasma at relatively high pressure. The hydrophilicity and topography of the modified IOL surface were comprehensively evaluated by contact angle and atomic force microscopy, while the surface biocompatibility of the modified IOL was investigated by platelets adhesion and cells proliferation experiments. The results revealed that the hydrophilicity of the HEMA-g-PMMA IOL samples were significantly and permanently improved. Less platelets attachment was observed on the modified IOL, especially in the HEMA₂-g-PMMA IOL group (with 1.65 × 10⁻¹ mol/L HEMA concentration), which also suppressed the proliferation of cells.     

Surface modification of acrylate intraocular lenses with dielectric barrier discharge plasma at atmospheric pressure

Surface modification with dielectric barrier discharge (DBD) plasma was carried out at atmospheric pressure (argon as the discharge gas) to improve the biocompatibility of hydrophobic acrylate intraocular lens (IOL). Changes of the plasma-treated IOL surface in chemical composition, morphology and hydrophilicity were comprehensively evaluated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and water contact angle (WCA) measurements. The surface biocompatibility of the untreated and plasma-treated IOLs was compared with the adhesion behavior of platelets, macrophages and lens epithelial cells (LECs) in vitro. After DBD plasma treatment, the hydrophilicity of the IOL surface was obviously improved. The changes in WCA with treatment extension may be attributed to both the introduction of oxygen or/and nitrogen-containing polar groups and the increase of surface roughness induced by plasma etching effect. The existence of low molecular weight oxidized material (LMWOM) was proved on the plasmatreated IOL which was caused by the chain scission effect of the plasma treatment. The plasma-treated IOLs resisted the adhesion of platelets and macrophages significantly. The LECs spreading and proliferation were postponed on the IOLs plasma-treated for more than 180 s, with a well maintained epithelial phenotype of LECs. The IOL biocompatibility was improved after the DBD plasma treatment. We speculate that slighter foreign-body reaction and later incidence of anterior capsule opacification (ACO) may be expected after implantation of the argon DBD plasma-treated IOL. Supported by the Zhejiang Natural Science Foundation of China (Grant No. 2004C23003)     

Synthesis and spectral studies on Co (II) and Ni (II) complexes with polyfunctional quinazoline-(3H)-4-ones

A series of complexes of Co(II) and Ni(II) with 2-(R)-3-(X)-substituted quinazoline-(3H)-4-ones, where R = methyl/phenyl and X = furalamino, uramino and thiouramino have been synthesised and characterised by analytical, conductivity, thermal and magnetic, infrared and electronic spectral data. Based on analytical and conductivity studies the stoichiometries of the complexes have been established. Conductivity data also show that all these complexes are non-electrolytes. Infrared spectral data indicate that all the ligands manifest neutral bidentate with both the metal ions. Geometries for the complexes have been proposed based on electronic spectral data. Various electronic spectral parameters have been calculated for all the complexes and relevant conclusions have been drawn with respect to the nature of bonds present in them.     

PMMA人工晶状体表面的CF4/O2等离子体修饰

为了改善聚甲基丙烯酸甲酯(PMMA)人工晶状体的生物相容性和透光性, 采用CF4/O2等离子体技术修饰其表面. 通过衰减全反射红外光谱(ATR-FTIR)、X射线光电子能谱(XPS)、静态接触角(CA)测定、扫描电子显微镜(SEM)、紫外-可见近红外光谱(UV-Vis)等方法进行表征, 结果表明, 经CF4/O2等离子体处理后, PMMA表面的含氟和含氧基团增加, 其表面的亲水性增强, 生物相容性改善, 紫外光的隔离效率增大. 因此, 通过CF4/O2等离子体修饰能够有效地改善PMMA人工晶状体的性质.     

ICP emission spectrometric analysis of rare earth elements in permanent magnet alloys

An analytical method for the determination of rare earth elements (REE) in a NdFeB permanent magnet alloy by ICP emission spectrometry is described. Spectral interferences, arising from overlapping, as well as matrix effects have been studied. Considering spectral interferences, sensitivities of spectral lines, background intensities and the chemical composition of the sample investigated, optimum spectral lines for each REE have been selected. Because of an unfavourable concentration ratio in samples of a NdFeB permanent magnet alloy, a preliminary separation of matrix elements from rare earth elements by ion chromatography is necessary. Different modes of elution (isocratic and gradient) with -hydroxy-isobutyric acid and different columns (NUCLEOSIL, SULFOPROPYL SI-100, DIONEX HPIC-CS3) have been tested. Optimum separation conditions have been chosen for each element and the separation efficiency at equal or different concentrations of the selected elements have been established. Although the separation of REEs resulted in partly overlapping peaks, the ratio between analyte and interferent is improved and the spectral interferences are diminished. The results obtained are in good agreement with certified values.     

Synthesis, thermal, spectral and magnetic studies of complexes of Co(II), Ni(II), Cu(II), Ru(II), Pd(II) and Pt(II) with 2, 3-disubstituted quinazolin-(3H)-4-ones

A number of complexes of Co(II), Ni(II), Cu(II), Ru(II), Pd(II) and Pt(II) with 2-methyl-3-(carboxy methyl) quinazolin (3H)-4-one (MCMQ) and 2-phenyl-3-(carboxy methyl) quinazolin (3H)-4-one (PCMQ) have been synthesized and characterized by analytical, conductivity, thermal, magnetic, infrared, electronic, proton magnetic resonance and electron spin resonance spectral data. Based on analytical data, the stoichiometry and the association with other molecules of the complexes have been determined. Conductivity data show that all these complexes are nonelectrolytes. Infrared and PMR spectral data indicate that both the ligands are uninegative bidentate with all the metal ions. Based on electronic spectral data, the geometries of the complexes have been indicated. Electronic spectral parameters for Co(II) and Ni(II) and ESR parameters for Cu(II) complexes have been calculated and relevant conclusions have been drawn with respect to the nature of bonds present in them.     

Synthesis,spectroscopic, and antimicrobial studies of the bivalent zinc and mercury complexes of thiosemicarbazide

A series of metal complexes of Zn(II) and Hg(II) having the general composition [ML₂]X₂ with thiosemicarbazide have been prepared and characterized by elemental chemical analysis, molar conductance, and spectral (IR and mass) studies. The IR spectral data suggest the involvement of sulfur and terminal amino nitrogen in coordination to central metal ion. On the basis of spectral studies, a tetrahedral geometry has been assigned for the Zn(II) and Hg(II) complexes. Thiosemicarbazide and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties. The article is published in the original.     

Electron impact mass spectral study of halogenated N-acetyl- and N-propionylcytisines

(-)-Cytisine and its derivatives, characterised by high affinity to neuronal nicotinic acetylcholine receptors with specificity for the α4β2 subtype, have been shown to be important probes in central nervous system (CNS) research. Electron impact mass spectral (EI-MS) fragmentations of halogenated derivatives of N-acetylcytisine and N-propionylcytisine have been investigated. Detailed fragmentation pathways have been identified for all significant ions including a few characteristic fragment ions. The principal mass spectral fragmentation routes of iodine and bromine compounds have been determined on the basis of low (EI), high resolution (HRD) and B(2)/E linked scan mass spectra as well as linked scans at constant B/E.     

Synthesis,spectroscopic, and antimicrobial studies of the bivalent cobalt,nickel, and copper complexes of thioacetamide

A series of metal complexes of cobalt(II), nickel(II), and copper(II) having the general composition [M(L)₂X₂] with thioacetamide have been prepared and characterized by elemental chemical analysis, molar conductance, magnetic susceptibility measurements, mass, IR, EPR, and electronic spectral studies. The IR spectral data suggests the involvement of sulfur and amino nitrogen in coordination to central metal ion. On the basis of spectral studies, an octahedral geometry has been assigned for the cobalt(II) and nickel(II) complexes whereas tetragonal geometry for copper(II) complexes. Thioacetamide and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties.     

Transition probabilities for some infrared O I spectral lines—Application for determining excitation temperatures in low temperature plasmas

Intensities of selected spectral transitions of neutral oxygen emitted from a wall-stabilized arc have been measured. Applying reliable transition probability data taken from literature, Boltzmann plots have been constructed and the temperatures of the plasma have been obtained. At arc plasma conditions ensuring partial local thermal equilibrium, transition probabilities for 4 O I spectral lines from the near infrared spectral range have been obtained. These new results, together with data for two other studied O I spectral lines taken from the National Institute of Standards and Technology data base, are proposed as a suitable set of transition probabilities applicable for diagnostics of low temperature plasmas.     

Construction of spectral sensitivity function using polychromatic UV sources.

A procedure is presented for constructing the spectral sensitivity functions of biological dosimeters, using five polychromatic UV sources possessing different emission spectra. Phage T7 and uracil biological dosimeters have been used for measuring the dose rates of the lamps. Their spectral sensitivity functions consisting of two exponential terms have been constructed. The parameters of the spectral sensitivity functions have been determined by comparing the directly measured and calculated dose-rate values. The parameters of the sensitivity function are accepted as correct values when the deviation of the measured and calculated values is a minimum. Based on the deviations between the constructed and the experimentally determined spectral sensitivities with monochromatic sources, the differences between the measured and calculated results are interpreted. The importance of the correct spectral sensitivity data is demonstrated through the effectiveness spectra of a TL 01 lamp for phage T7 killing, uracil dimerization and erythema induction.     

Multivariate calibration leverages and spectral F‐ratios via the filter factor representation

Diagnostics are fundamental to multivariate calibration (MC). Two common diagnostics are leverages and spectral F‐ratios and these have been formulated for many MC methods such as partial least square (PLS), principal component regression (PCR) and classical least squares (CLS). While these are some of the most common methods of calibration in analytical chemistry, ridge regression is also common place and yet spectral F‐ratios have not been developed for it. Noting that ridge regression is a form of Tikhonov regularization (TR) and using the unifying filter factor representation for MC, this paper develops the filter factor form of leverages and spectral F‐ratios. The approach is applied to a spectral data set to demonstrate computational speed‐up advantages and ease of implementation for the filter factor representation. Copyright © 2010 John Wiley & Sons, Ltd.     

Hydrogen/argon plasma jet with methane addition

Spatial distributions of plasma parameters are presented for a H₂/Ar plasma jet with addition of methane. The plasma has been generated at atmospheric pressure by a 200 A (20 kW) nontransferred do arc. Optical emission spectroscopy has been used for the measurements assuming the plasma jet to be optically thin and to have an axial symmetry. Local spectral ernissivity values have been evaluated using a routine Abel inversion procedure. Half- width and emissivity of H spectral line have been measured to determine the electron density and temperature of the plasma. The densities of excited C, CH radicals have been evaluated from the absolute emissivities of relevant molecular emission bands measured in limited spectral intervals in the visible spectrum. The emissivity ratios have been used to fund rotational and vibrational temperatures. The results supply information on methane decomposition and the behavior of molecular radicals in close-to-thermal plasma jets.     

Synthesis,structure, and spectral fluorescence properties of 1,4-di(5-phenyl-2-oxazolyl)benzene heteroanalogs

Novel organic luminophors belonging to the oxazole and oxadiazole classes of compounds have been synthesized, namely, thiophene and furan analogs of 1,4-di(5-phenyl-2-oxazolyl)benzene. The optical properties of these compunds have been studied both theoretically and experimentally. Their IR spectra have been measured and their UV absorption, fluorescence, and excitation spectra have been analyzed. Details of their electronic structure and their principal spectral fluorescence parameters have been calculated using the PPP method. Possible methods or pathways for improving the spectral fluorescence parameters of organic luminophors in these classes of compounds in the visible region of the spectrum have also been analyzed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1414–1419, October, 1989.     

Interaction between methyl glyoxal and ascorbic acid: experimental and theoretical aspects

The absorption spectral change of methyl glyoxal (MG) due to the interaction with ascorbic acid (AA or Vitamin C) has been investigated using steady-state spectroscopic technique. A plausible explanation for the spectral change has been discussed on the basis of hydrogen bonding interaction between the two interacting species. The equilibrium constant for the complex formation due to hydrogen bonding interaction between MG and AA has been obtained from absorption spectral changes. Ab inito calculations with DFT B3LYP/6/31G (d,p) basis sets have been used to find out the molecular structure of the hydrogen bonded complex. The O...H distance found in the O-H...O hydrogen bond turns out to be quite short (1.974 A) which is in conformity with the large value of the equilibrium constant determined experimentally.     

Repulsion forces in vibrational spectroscopy—I. Spectral shifts in vibrational spectra of condensed media caused by repulsion forces

Repulsional contributions into spectral shifts have been expressed in terms of derivatives of atom displacements with respect to vibrational normal coordinates. Attraction and repulsion have been shown to give a comparable contribution to the overall shift. Working ability of the formulae obtained for spectral shift calculations for molecular (HCl solution in CCl₄) and ionic (molten lithium and rubidium nitrates) liquids is demonstrated.