Photophysical and photosensitizing properties of selected cyanines

The present work has been carried out to obtain detailed information about the photophysical and photobiological properties of selected cyanines, in view of their possible use as photosensitizing agents. All the cyanines studied by us except CY-IV (3,3'-diethyl-4,4'-oxacarbocyanine), expressed an accelerated photobleaching in aqueous medium, a poor generation of singlet oxygen, and a relative weak photosensitizing activity towards albumin. On the cellular level, all cyanines exhibited a significant phototoxicity towards Balb/c 3T3 cells, upon irradiation with a total fluence of 30 J/cm(2). CY-III (3,3'-diethylcarbothiocayanine iodide) and CY-II (1,1'-diethyl-4,4'-carbocyanine iodide) appear to be promising photosensitizers, in spite of previous reports on the inefficiency of the former cyanine, and the rapid photobleaching of the latter compound.     

Photophysical and photosensitizing properties of brominated porphycenes

A heavy atom, bromine, was directly substituted into the porphycene macrocycle to promote intersystem crossing by way of spin-orbit coupling. The singlet oxygen production ability of the porphycene is dramatically enhanced, and the highest value of 0.95 for the quantum yield of singlet oxygen generation (PhiDelta) was obtained for the dibrominated porphycene by visible light excitation.     

A carbohydrate-linked hypericinic photosensitizing agent

With respect to an enhanced solubility under physiological conditions, a carbohydrate-containing hypericin-based second-generation photosensitizer was prepared. Its photochemical properties were tested by means of the light-sensitized destruction of bilirubin IXα to be even better than those of the parent compound hypericin. Investigations on binding-interactions with DNA showed promising results as well.     

Structure and properties of a photosensitive polyimide: Effect of photosensitive group

The photosensitive poly(p-phenylene biphenylteracarboximide) (BPDA-PDA) precursor was synthesized by attaching photocross-linkable 2-(dimethylamino)ethyl methacrylate (DMAEM) monomer to its poly(amic acid) through acid/base complexation. The polyimide thin films were prepared by a conventional cast/softbake/thermal imidization process from the photosensitive precursors with various concentrations of DMAEM. The structure and properties of the polyimide films were investigated by small-angle and wide-angle x-ray scattering, refractive indices and birefringence analysis, residual stress and relaxation analysis, stress-strain analysis, and dynamic mechanical thermal analysis. In comparison with the polyimide film from the poly(amic acid), the films, which were imidized from the photosensitive precursors, exhibited a better molecular order and microstructure; however, they exhibited less molecular orientation in the film plane. Despite the enhancement in both the molecular order and microstructure, the film properties (i.e., mechanical properties, thermal expansion, residual stress, optical properties, dielectric constant, and water sorption) degraded overall due to both the decrease in molecular in-plane orientation and the formation of microvoids caused by the bulky photosensitive group during thermal imidization. That is, on one hand, the PSPI precursor formation provides an advantageous, direct patternability to the BPDA-PDA precursor, and on the other hand, it results in degraded properties to the resulting polyimide film. © 1995 John Wiley & Sons, Inc.     

Photoprocesses of photosensitizing drugs within cyclodextrin cavities

Recently some interest has been focused on the photobehavior of CD-drug inclusion complexes in relation to the problem of the biological photosensitization by drugs. This review is dedicated to the illustration of the mechanistic aspects of the photoprocesses occurring in some non-steroidal anti-inflammatory drugs (NSAIDs), with photosensitising side effects, within CD cavities. It is shown how the photobehavior of the CD-drug associates can help to model the photoreactivity of the drugs in biological sites. The limitations for the use of CDs as protective systems for the clinical administration of photosensitising drugs is also evidenced.     

Synthesis and photosensitizing properties of fluoroalkoxyl phthalocyanine metal complexes

Nine fluoroalkoxyl phthalocyanine metal complexes (Zn, AlCl, Mg, Co, Cu, FeCl) were synthesized from 4-(polyfluoroalkoxyl) phthalic anhydride. The fat-soluble phthalocyanines were characterized by elemental analysis, IR, ¹H NMR and fast-atom-bombardment mass spectroscopy. Zinc and aluminum chloride complexes show higher photooxidation ability in solution containing 20% perfluorocarbons than in hydrocarbon solvents.     

Synthesis and characterization of photosensitive polyimides

All aromatic polyimides bearing diarylsulfide linkages in the main chain were prepared either by condensation of a sulfur containing dianhydride with an aromatic diamine or the condensation of a sulfur containing aromatic diamine with a dianhydride. Phenylation with diphenyl iodonium salts was then used to convert the diarylsulfide groups to triarylsulfonium salts. The resulting photosensitive polyimides were shown to undergo main chain cleavage during photolysis using UV irradiation. These new polyimides are candidates for positive working, high temperature photoresist materials.     

Semiconductor quantum dots photosensitizing release of anticancer drug

A new photo-controlled anticancer drug release system is reported based on the photo-induced electron transfer (PET) between semiconductor quantum dots (QDs) and N-methyl-4-picolinium (NAP) ester 1 under the excitation of visible light.     

Development and commercialization of ionic-type photosensitive polyimides

Toray's ionic-type photosensitive polyimide, “Photoneece”, is widely used as an interdielectric and as a protection layer for microelectronics, because of its properties, such as the removal of photoreactive groups at low temperature, excellent thermal, mechanical and electrical film properties and excellent adhesion to various substrates. Toray has developed a new type of “Photoneece”, UR-5100, which is a low-stress photosensitive polyimide. In addition to a low thermal expansion coefficient (25 ppm/°C), “Photoneece” UR-5100 also features high resolution with an aspect ratio of more than 2.0 in 40 μm imaged film, and excellent mechanical properties in the cured film such as high elongation (>20%) and tensile strength (>200 MPa), even after 60 hr heat treatment at 350°C. “Photoneece” UR-5100 can be applied in multichip modules (MCMs), hybrid circuits, ICs and LSIs. In this paper the characterization and processing of this “Photoneece” UR-5100 are described.     

The photosensitizing effect of the photoproduct of protoporphyrin IX

The photodynamic effect of a photoproduct of protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA) was investigated in WiDr cells, a human adenocarcinoma cell line. The fluorescence excitation and emission spectra of PpIX and the photoproduct were measured. After 1, 3 or 5 min exposure of the ALA-incubated cells to 140 mW/cm² light at 635 nm, the photoproduct — the chlorin photoprotoporphyrin (Ppp), had an emission band around 670 nm. The Ppp excitation peak at 670 nm is well separated from the PpIX peak at 635 nm. The outcome of photodynamic therapy (PDT) was determined by measuring intracellular fluorescence intensity of propidium iodide (PI) 2 h following PDT and methylene blue (MB) staining 24 h following PDT. A significant increase in the fluorescence intensity of PI was noted when the ALA-loaded cells were exposed to 670 nm light after exposure to 635 nm, indicating enhanced cell membrane inactivation induced by the photodynamic action of the photoproduct. However, the fraction of the cells that survived following the same treatment as measured by MB staining was not significantly affected based on an analysis of variance. The fluorescence of PpIX decayed significantly during 635 nm light exposure. Exposure to light at 670 nm does not lead to any photodegradation of PpIX. The fluorescence of Ppp was bleached during 670 nm light exposure. Exposure of Ppp at 670 nm gives no PpIX back. Thus, the phototransformation of PpIX to Ppp is probably not a reversible process.     

Stabilization of photosensitizing dyes by complexation with clay

Synthetic saponites containing photosensitizing dyes (1,1'-diethyl-2,2'-cyanine (pseudoisocyanine) or tris(2,2'-bipyridine)ruthenium(II)) in the interlayer space were complexed with nanocrystalline anatase. The photostability of the dyes in the dye-clay-anatase hybrids upon visible light irradiation was improved, possibly because of the separation of the dyes from the anatase surface by the thin clay layer.     

Protease-triggered photosensitizing beacon based on singlet oxygen quenching and activation

We report a new concept for type-II photosensitization, based on incorporating the photosensitizer (PS) and a singlet-oxygen (1O2) quenching/scavenging molecule onto a disease-targeting linker, such that the PS becomes activatable by light only when targeting has occurred. In this first proof-of-concept report, a model photosensitizing beacon was synthesized containing a pyropheophorbide as the PS and a carotenoid as the 1O2 quencher. These were kept in close proximity by the self-folding of a caspase-3-specific peptide sequence. Upon caspase-3-induced cleavage, the 1O2 production increased markedly, as measured directly by 1O2 near-infrared luminescence and lifetime measurements.     

Study of photopolymer. XVII. Synthesis of novel photosensitive polymers with pendant photosensitive group and photosensitizer groups

Novel photosensitive polymers with pendant photosensitive group, such as cinnamic ester, and photosensitizer groups, such as N-carbamoyl-p-nitroaniline and N-carbamoly-4-nitro-1-naphthylamine, were synthesized from radical copolymerizations of (2-cinnamoyloxy)ethylmethacrylate with photosensitizer monomers, such as p-nitrophenylmethacrylamide and 4-nitro-1-na-phthylmethacrylamide, by using asobisisobutyronitrile (AIBN) in benzene and from the copolymerizations of (2-hydroxy)ethylmethacrylate or (2-hydroxy)ethylacrylate with photosensitizer monomers by using AIBN in DMF. This procedure was followed by condensation reactions of the copolymers with cinnamoyl chloride with pyridine as HCL acceptor in the same reaction flask. The photoreactivities of the polymers obtained were influenced by the concentration of photosensitive group and photosensitizer groups and their ratio in the polymer matrix. In addition, the photosensitivity of cinnamic ester groups attached to a soft polymer segment was higher than that of cinnamic ester group attached to a hard polymer segment when these polymers had the same pendant N-carbamoyl-p-nitroaniline group as photosensitizer. Furthermore, the spacer length between the polymer chain and photosensitizer group was important for increasing the photoreactivity of the photosensitive group in the polymers with pendant cinnamic ester and N-carbamoyl-p-nitroaniline groups.     

Energy and electron transfers in photosensitive chitosan

Novel photosensitive chitosan was synthesized. The modified chitosan contains photoactive anthracene chromophore moieties. Because of the presence of anthracene chromophores, the polymer absorbs light in the UV-vis spectral region. Electronically excited polymeric chromophores could participate in energy and electron transfer processes to the suitable acceptor molecules. The photosensitive chitosan developed herein could could act as an efficient photosensitizer and lead to the application of the environmentally friendly photocatalytic system for an efficient degradation of a wide range of pollutants.