mJ Cm-2 Research Articles

Reactive Oxygen Species in HaCaT Keratinocytes After UVB Irradiation Are Triggered by Intracellular Ca2+ Levels

It is recognized that reactive oxygen species (ROS) are responsible for skin damage due to UVB-radiation (UVB-R). However, the triggering substance(s) for ROS generation after UVB-R is uncertain with respect to the activation of NADPH oxidase (Nox), xanthine oxidase (XOD), and respiratory chain-chain reactions in mitochondria. As a first step in identifying the trigger(s) for UVB-induced ROS generation, we examined the relationship between Ca(2+) levels and ROS generation in HaCaT keratinocytes. UVB-R exposure of HaCaT keratinocytes resulted in an immediate elevation of ROS that recurred 7 hours later. This was accompanied by immediately elevated intracellular Ca(2+) . A Ca(2+) chelating agent, BAPTA, abolished the elevation of ROS after UVB-R completely. In addition, exogenous H(2)O(2) did not increase intracellular Ca(2+) levels. This suggests that intracellular Ca(2+) is the first trigger for UVB-induced ROS generation.Journal of Investigative Dermatology Symposium Proceedings (2009) 14, 50-52; doi:10.1038/jidsymp.2009.12.

Organo-Soluble Low CTE Polyimides and their Applications to Photosensitive Cover Layer Materials in Flexible Printed Circuit Boards

A novel cover layer material for flexible printed circuit (FPC) applications was developed in this work. A high molecular weight of polyimide composed of four monomers, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BisApAf) was prepared by the one-pot polycondensation in N-methyl-2-pyrrolidone (NMP) without precipitation and gelation. The polyimide (PI) was highly soluble in various common organic solvents. Interestingly, the PI film formed by simple solution-casting of the PI solution had a low CTE value close to that of copper foil, therefore almost no curling of the PI/copper laminate was observed when the PI film was directly formed on a copper foil. The PI film also exhibited other combined properties, including a low CTE, a high Tg, high thermal stability, low water absorption, comparatively good transparency, the highest levels of non-flammability, good insulation properties and sufficient film flexibility. In addition, fine positive-tone patterns could be obtained from DNQ-containing PI with a sensitivity of 238 mJ cm-2. The results revealed that the present PI system is a promising candidate as a novel cover layer material.

Feasibility Study of Chemically Amplified Extreme Ultraviolet Resists for 22 nm Fabrication

The trade-off between sensitivity, resolution, and line edge roughness is the most important concern for the development of high-performance resists based on chemical amplification. Below sub-30 nm patterns, a chemical balance between acids and quenchers basically controls the quality of latent images. Under this situation, an ideal chemically amplified resist is the one in which the neutralization between acids and quenchers proceeds before the start of acid catalytic reactions and chemical reactions occur with a diffusion-controlled rate. In this study, the qualities of latent images were compared among exposure doses of 2, 5, 10, and 20 mJ cm-2 under the ideal condition. The authors found that chemically amplified resists with a 22 nm resolution and a 10 mJ cm-2 sensitivity are feasible under the ideal condition. However, a high-quality image is unlikely to be obtained upon 5 mJ cm-2 exposure without increasing polymer absorption or acid generation efficiency per photon.

Organo-Soluble Low CTE Polyimides and their Applications to Photosensitive Cover Layer Materials in Flexible Printed Circuit Boards

A novel cover layer material for flexible printed circuit (FPC) applications was developed in this work. A high molecular weight of polyimide composed of four monomers, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BisApAf) was prepared by the one-pot polycondensation in N-methyl-2-pyrrolidone (NMP) without precipitation and gelation. The polyimide (PI) was highly soluble in various common organic solvents. Interestingly, the PI film formed by simple solution-casting of the PI solution had a low CTE value close to that of copper foil, therefore almost no curling of the PI/copper laminate was observed when the PI film was directly formed on a copper foil. The PI film also exhibited other combined properties, including a low CTE, a high Tg, high thermal stability, low water absorption, comparatively good transparency, the highest levels of non-flammability, good insulation properties and sufficient film flexibility. In addition, fine positive-tone patterns could be obtained from DNQ-containing PI with a sensitivity of 238 mJ cm-2. The results revealed that the present PI system is a promising candidate as a novel cover layer material.

Direct and Sensitized Photolysis of Dispersed Photoacid Generators

This work proposes water-borne photopolymers cast and developed solely with neutral water by incorporating mechanically milled sub-micron particles of poorly water-soluble photoacid generators (PAGs) to make a poly(vinyl alcohol) film insoluble in water with aid of an acid-sensitive crosslinker. Fluorescence measurements of milled mixtures of anthracene and a tiny amount of tetracene in water revealed that the solid-state energy transfer occurs through singlet exciton migration as a result of mechanochemical crystal mixing. Solid-state electron transfer was also verified by fluorescence quenching of milled mixtures of PAG and emissive sensitizers including anthracene derivatives as a consequence of exciton diffusion in sensitizer crystals to reach at the particle surface to transfer an electron to PAG solid. Factors affecting solid-state electron transfer efficiency include the nature of PAG and sensitizers, particle sizes and exciton diffusion length, whereas bis[p-(tert-butylphenyl)]iodonium hexafluorophosphate (1a) was the best solid-state quencher. Solid-state sensitized photoacid generation was confirmed by irradiating aqueous dispersions of co-milled PAG and a sensitizer. Based on these results, three-component photopolymers comprised of an aqueous dispersion of PAG in absence or in the presence of a co-milled sensitizer, poly(vinyl alcohol) and a water-soluble diepoxy were prepared to exhibit photosensitivity of 17 mJ cm-2 by the direct photolysis of a dispersed sulfonium salt and that of ca.120 mJ cm-2 by the photolysis of 1a sensitized with co-milled 9, 10-dipropoxyanthracene.

A study of the photodegradation of leukotriene B4 by ultraviolet irradiation (UVB, UVA)

In view of the presence of the polymorphonuclear leukocyte (PMN) chemoattractant Leukotriene B4 (LTB4) in the surface scale of the psoriatic lesion and the known therapeutic effect of phototherapy in psoriasis, the photostability of LTB4 was investigated. LTB4 was irradiated with dosages of UVB (290-320 nm) ranging from 100-1500 mJ cm-2 and with dosages of UVA (320-400 nm) ranging from 5-40 J cm-2. Topical application of UVB irradiated LTB4 to the forearm skin of normal volunteers showed a marked reduction in cutaneous erythema, paralleled histologically by reduced transepidermal PMN migration when compared with sites of application of unirradiated and UVA irradiated LTB4. High performance liquid chromatography (HPLC) demonstrated a dose-dependent photodegradation of LTB4 by UVB irradiation. UVA irradiation produced no such effect. The wavelengths responsible lie within the absorption spectrum of LTB4. In vitro chemotaxis studies, using an under agarose technique, showed a statistically significant reduction in the migration of PMN from both psoriatic and non-psoriatic subjects to the UVB irradiated LTB4 compared with the unirradiated LTB4, whilst UVA irradiated LTB4 produced a normal PMN chemotactic response.

Impact of iron particles in groundwater on the UV inactivation of bacteriophages MS2 and T4

To investigate the impact of iron particles in groundwater on the inactivation of two model viruses, bacteriophages MS2 and T4, by 254-nm ultraviolet (UV) light. One-litre samples of groundwater with high iron content (from the Indianapolis Water Company, mean dissolved iron concentration 1.3 mg l(-1)) were stirred vigorously while exposed to air, which oxidized and precipitated the dissolved iron. In parallel samples, ethylenediaminetetra-acetic acid (EDTA) was added to chelate the iron and prevent formation of iron precipitate. The average turbidity in the samples without EDTA (called the 'raw' samples) after 210 min of stirring was 2.7 +/- 0.1 NTU while the average turbidity of the samples containing EDTA (called the 'preserved' samples) was 1.0 +/- 0.1 NTU. 'Raw' and 'preserved' samples containing bacteriophage MS2 were exposed to 254-nm UV light at doses of 20, 40, or 60 mJ (cm(2))(-1), while samples containing bacteriophage T4 were exposed to 2 or 5 mJ (cm(2))(-1), using a low pressure UV collimated beam. The UV inactivation of both phages in the 'raw' groundwater was lower than in the EDTA-'preserved' groundwater to a statistically significant degree (alpha = 0.05), due to the association of phage with the UV-absorbing iron precipitate particles. A phage elution technique confirmed that a large fraction of the phage that survived the UV exposures were particle-associated. Phages that are associated with iron oxide particles in groundwater are shielded from UV light to a measurable and statistically significant degree at a turbidity level of 2.7 NTU when the phage particle association is induced under experimental conditions. While the particle association of the phage in this study was induced experimentally, the findings provide further evidence that certain particles in natural waters and wastewaters (e.g. iron oxide particles) may have the potential to shield viruses from UV light.

Stimulated emission of disordered media based on crystalline ZnO powders

Low-threshold lasing (Eth = 0.94 mJ cm-2) is obtained in crystalline ZnO powders at room temperature. The stimulated emission spectra exhibit a distinct mode structure. The powders consisting of nanocrystals with the tetrapod-shaped morphology were synthesised by high-temperature pyrolysis of organic zinc salts.

Cell disintegration by laser-induced transient microbubbles and its simultaneous monitoring by interferometry

Selective retina treatment (SRT) is a novel short pulsed laser therapy of several retinal diseases associated with a decreased metabolism at the retinal pigment epithelium (RPE). The range of laser pulse energies is small, in which the desired selective RPE disintegration is achieved without adverse effects to the neural retina. Thus, a real-time dosimetry control is required. We investigated a noninvasive interferometric technique able to monitor microbubble formation around the intracellular melanin granula, which is the origin of the desired RPE damage. A porcine ex vivo RPE model was irradiated by single pulses (350 ns1.7 mus) of a neodymium: yttrium lithium fluoride laser (527 nm). The specimen was simultaneously probed by a Michelson interferometer (helium neon-laser: 633 nm) and by a hydrophone. Cell viability assays (Calcein-AM) were performed after irradiation. At threshold radiant exposure for cell death (ED(50)=129+/-5 mJ cm2 for 350 ns; ED50=180+/-5 mJ cm2 for 1.7 mus), the interferometric transients changed due to microbubble formation. No major differences in the bubble dynamics were observed between both pulse durations. An algorithm to determine cell death from the interferometric transients showed less than 10% false positive or false negative results for the applied laser expositions compared to the viability assay. Interferometry is a reliable noncontact technique to monitor RPE disintegration and may serve as real-time dosimetry control during SRT.

N-retinoyl-D-glucosamine, a new retinoic acid agonist, mediates topical retinoid efficacy with no irritation on photoaged skin

Chronic ultraviolet (UV) radiation from sunlight induces wrinkle formation. Retinoic acid (RA) can markedly improve wrinkles, although RA does have some side-effects, such as skin irritation. As the efficacy and cytotoxicity of RA has been traced to its free carboxylic acid, we synthesized a new molecule, N-retinoyl-D-glucosamine (GRA), in which a glucosamine has been attached to the polar end group of all-trans retinoic acid. To analyse the effect of topical GRA in wrinkle repair and anti-irritation in photoaged mice compared with topical RA, as well as to determine retinoic acid receptor (RAR) and retinoid X receptor (RXR) transactivation activity in vitro. Hairless mice were irradiated with 60 mJ cm-2 of UVB for 10 weeks, and then topically treated with 0.05% GRA or 0.05% RA for 8 weeks. An in vitro transcriptional assay was performed and the activity of GRA in 293 cells transfected with RAR-alpha or RXR-alpha expression plasmid and luciferase reporter plasmid then determined. Topical GRA and RA brought about almost complete disappearance of the wrinkles caused by UVB irradiation. The two ligands promoted both a wide repair zone histologically, and the expression of type 1 collagen in the skin. In contrast, topical GRA treatment did not produce irritation such as erythema or roughness, or alteration of transepidermal water loss values, compared with RA. In the in vitro luciferase assay, GRA resulted in significant dose-dependent RAR transactivation activity in a 100 times higher concentration range than RA. GRA did not mediate RXR transactivation activity at all. Topical GRA appears to be able to repair photoaged skin damage without any of the irritation caused by topical RA, probably via RAR transactivation activity.

Ultrafast and Low Barrier Motions in the Photoreactions of the Green Fluorescent Protein

Green fluorescent protein (GFP) fluoresces efficiently under blue excitation despite major electrostatic rearrangements resulting from photoionization of the chromophore and neutralization of Glu-222. A competing phototransformation process, which ionizes the chromophore and decarboxylates Glu-222, mimics the electrostatic and structural changes in the fluorescence photocycle. Structural and spectroscopic analysis of the cryogenically stabilized photoproduct at 100 K and a structurally annealed intermediate of the phototransformed protein at 170 K reveals distinct structural relaxations involving protein, chromophore, solvent, and photogenerated CO2. Strong structural changes of the 100 K photoproduct after decarboxylation appear exclusively within 15 angstroms of the chromophore and include the electrostatically driven perturbations of Gln-69, Cys-70, and water molecules in an H-bonding network connecting the chromophore. X-ray crystallography to 1.85 angstroms resolution and static and picosecond time-resolved IR spectroscopy identify structural mechanisms common to phototransformation and to the fluorescence photocycle. In particular, the appearance of a 1697 cm(-1) (+) difference band in both photocycle and phototransformation intermediates is a spectroscopic signature for the structural perturbation of Gln-69. This is taken as evidence for an electrostatically driven dynamic response that is common to both photoreaction pathways. The interactions between the chromophore and the perturbed residues and solvent are decreased or removed in the T203H single and T203H/Q69L double mutants, resulting in a strong reduction of the fluorescence quantum yield. This suggests that the electrostatic response to the transient formation of a buried charge in the wild type is important for the bright fluorescence.

Highly Efficient Photogeneration of Surface Relief Structure and Its Immobilization in Cross-Linkable Liquid Crystalline Azobenzene Polymers

A new family of azobenzene containing polymer applicable for photoinduced surface relief formation is reported. An azobenzene containing acrylate was copolymerized with methacrylate monomers bearing an oligo(ethylene oxide) chain via free radical copolymerization, yielding soft liquid crystalline polymers. These copolymers displayed a smectic liquid crystal phase at room temperature. After preexposure to ultraviolet light, thin films of the liquid crystalline polymers showed highly sensitive photoinduced material transfer to generate the surface relief structures. The typical exposure dose required for full polymer migration was as low as 50 mJ cm-2. The inscribed surface relief structures could be rapidly and fully erased either upon incoherent nonpolarized ultraviolet light irradiation or by heating close to the clear point of the soft liquid crystalline polymers. On the other hand, the chemical cross-linking, using a mixed vapor of hydrogen chloride and formaldehyde after surface relief inscription, re...

Effect of Annealing on the Tolerance of LiCaAlF6 Single Crystals against F2 Laser Irradiation

The optical tolerance of annealed LiCaAlF6 single crystals against F2 laser irradiation was investigated. Annealed LiCaAlF6 (t=1.45 mm) shows an improved transmittance at 157 nm, 94.4% after the compensation of the surface reflection loss. Furthermore, after the initial increase by F2 laser cleaning, transmittance at 157 nm remains almost unchanged even after irradiation with a F2 laser beam up to 105 pulses at a fluence of approximately 160 mJ cm-2 pulse-1.

New Positive-type Photosensitive Polyimide Having Sulfo Groups 2. Polyimides from 2,2'-oxy(or thio)bis(5-aminobenzenesulfonic acid) 4,4'-oxydianiline, and 4,4'-hexafluoro propylidene-bis(phthalic anhydride)

New positive-working photosensitive polyimides (PSPIs) based on polyimides bearing sulfo groups (PISs) and 1-{1,1-bis[4-(2-diazo-1-(2H)naphthalenone-5-sulfonyloxy)phenyl]ethyl} -4-{1-[4-(2-diazo-1(2H)naphthalenone-5-sulfonyloxy)phenyl]methylethyl}benzene (S-DNQ) as a photosensitive compound have been developed. PISs were prepared by ring-opening polyaddition of 2,2'-oxybis(5-aminobenzenesulfonic acid) (OBAS) or, 2,2'-thiobis(5-aminobenzenesulfonic acid) (TBAS) and 4,4'-oxydianiline (ODA), with 4,4'-hexafluoropropylidenebis(phthalic anhydride) (6FDA), followed by thermal cyclization in m-cresol. PIS containing 30wt% of S-DNQ showed a sensitivity of 100 mJ cm-2 and a contrast of 2.6, when it was exposed to 365-nm light followed by developing with 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution at room temperature. A fine positive image featuring 20μm line and space patterns was observed on the film of the photoresist exposed to 200 mJ cm-2 of UV-light at 365 nm by the contact mode. The positive image was successfully converted to the polyimide pattern by thermal treatment.

How light irradiance and curing time affect monomer conversion in light‐cured resin composites

We tested the hypothesis that the degree of conversion of a light-cured dental composite relates to the calculated (s x mW cm-2 = mJ cm-2) rather than to the irradiance value (mW cm-2) of the light source. Two light-curable composite resins were cured with three different light irradiance values over different curing times. The specimens tested were 2, 4 or 6 mm thick, and the degree of conversion values were measured with Raman spectroscopy on the top and the bottom surfaces of the specimens. The highest conversion value of one of the materials was just below 60%, while the maximal conversion value of the other material was just below 65%. That difference in conversion values could be related to differences in monomer systems used in the two composites. By considering light energy per square centimeter (J cm-2) rather than light irradiance (mW cm-2), we found that equivalent energy values gave similar conversion values for a certain sample thickness. From these findings, we conclude that our experimental results support our hypothesis.

Ultra-fast dynamics of electron thermalization, cooling and transport effects in Ru(001)

Time-resolved two-photon photoelectron spectroscopy is used to study the dynamics of non-equilibrium electron and hole distributions at bare and D2O-covered Ru(001) following optical excitation (55-fs, 800-nm pulses) with variable fluence (0.04–0.6 mJ cm-2). Within the first 0.5 ps we observe an ultra-fast transient of the excited-carrier population and energy density at the surface which is accompanied by pronounced deviations of the electron-energy distribution from a (thermalized) Fermi–Dirac distribution. Comparison of the transient energy density of the photoexcited electrons at the surface with predictions of the two-temperature model provides fair agreement up to 400 fs, but exhibits a systematically lower energy density at later times, where electrons and phonons are equilibrated. We propose that this reduced energy density at the surface originates from ultra-fast energy transport of non-thermal electrons into the bulk in competition to electron–phonon coupling at the surface. This is corroborated by extending the two-temperature model to account for non-thermal, photoexcited electrons, whereby quantitative agreement with experiment can only be achieved if ballistic transport and reduced electron–phonon coupling is incorporated for non-thermal electrons. Implications for surface femtochemistry are discussed.

KUVA (khellin plus ultraviolet A) stimulates proliferation and melanogenesis in normal human melanocytes and melanoma cells in vitro.

Khellin is a naturally occurring furochromone which, when combined with artificial ultraviolet (UV) A or solar irradiation (KUVA), is reported to repigment vitiligo skin as effectively as PUVA photochemotherapy. The exact mechanism of KUVA-induced repigmentation is unknown. The aim of this study was to test the effect of khellin and KUVA on proliferation and melanogenesis of normal human melanocytes and Mel-1 melanoma cells in vitro. Cultured normal human melanocytes, Mel-1 melanoma cells and fibroblasts were treated with khellin, UVA and KUVA and the effect on proliferation determined by cell counting. The effect on melanogenesis was determined by a radiometric melanin formation assay. Changes in gene expression and protein synthesis were determined by Northern blot, reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analyses. Khellin stimulated proliferation of Mel-1 melanoma cells and melanocytes at concentrations between 1 nmol L-1 and 0.5 mmol L-1 with a peak effect at 0.01 mmol L-1 khellin. In contrast, khellin inhibited proliferation of fibroblasts over the entire concentration range tested. At concentrations above 0.5 mmol L-1, khellin was cytotoxic to both melanocytic cells and fibroblasts. Exposure of khellin-treated cells to single doses of UVA between 150 and 280 mJ cm-2 resulted in an enhanced proliferative effect. Khellin and KUVA also stimulated the melanogenic enzyme activity of pigmented cells, with the most effective treatment being 0.01 mmol L-1 khellin with 250 mJ cm-2 UVA. Western blot, Northern blot and RT-PCR analysis revealed that these increases in melanogenic enzyme activity were not due to increases in gene expression or protein synthesis. UVA treatment resulted in an increase in enzyme glycosylation and this correlated with the increase in melanogenesis. We conclude that khellin activated by UVA stimulates melanocyte proliferation and melanogenesis. Our results point to the possibility that current treatment regimens might be improved if reduced khellin doses are applied and suggest that improved delivery vehicles be tested.

157-nm laser micromachining of N-BK7 glass and replication for microcontact printing

We report etch-rate and probe-beam-deflection studies of N-BK7 glass ablated using a 157-nm F2 laser. It is found that controllable material removal at the nanometre level is possible above an ablation threshold of 250 mJ cm-2. Contact mask printing shows well-defined features can be micromachined in this glass with sub-micron resolution capability. Micro-features produced in this way have been replicated by polydimethylsiloxane (PDMS) moulding and the stamps used to print arrays of fluorescent molecules with sub-micron fidelity.

Infrared Laser Desorption of Hydroquinone from a Water−Ethanol Liquid Beam

We have investigated the 1.9-μm IR desorption of hydroquinone in a water/ethanol liquid beam under relatively high desorption laser fluences (1316 and 2632 mJ cm-2 pulse-1). The appearance of the IR desorption/UV ionization TOF mass spectrum of hydroquinone (HQ) is interpreted in terms of dissociation of solvated HQ clusters during the ionization event. The maximum in the hydroquinone desorption velocity distribution is 300 ms-1, and the translational temperature of the desorbed species is approximately 1500 K. We see no evidence for an acoustic compression−ejection mechanism, suggesting that such a process is operative at desorption laser fluences lower than employed here. Our results suggest a general mechanism for the high-powered IR desorption from a liquid beam whereby desorbed species are ejected into the vacuum possessing considerable translational energy but remain internally cool.

Negative-Working Photosensitive Polybenzoxazoles Based on Hyperbranched Poly(o-hydroxyamide)s

The negative-working photosensitive polybenzoxazole (PSPBO) composed of hyperbranched poly(o-hydroxyamide) (HBPHA), 2,6-bis(hydroxymethyl)-p-cresol (BHMP) as a cross-linker and diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate (DIAS) as a photoacid generator (PAG) was developed and evaluated. The HBPHA as a precursor of PSPBO was prepared by self-polycondensation of an AB2 type monomer. The acid-catalyzed cross-linking of the BHMP in the presence of strong acid such as p-toluenesulfonic acid (p-TsOH) was investigated by using DSC and TGA. The cross-linking of BHMP was accelerated in the presence of p-TsOH, whereas cross-linking was not observed until it reached 140 °C without acid. The photolithographic performance of the resist (XPR-721) formulated with 70 wt% of HBPHA, 20 wt% of BHMP, and 10 wt% of DIAS was evaluated. The resist showed high sensitivity (Eth1/2 = 56 mJ cm-2) and good contrast (γ1/2 = 4.6) with 365 nm light when it was developed in 1.19 wt% tetramethylammonium\-hydroxide (TMAH) aqueous solution at room temperature. The fine negative pattern was obtained at the 200 mJ cm-2 of i-line exposure. The patterned film was successfully converted to polybenzoxazole without any distortion by thermal treatment at 350 °C for 1 h.