Type Of Photosensitizer Research Articles

Extended model of the photoinitiation mechanisms in photopolymer materials

In order to further improve photopolymer materials for applications such as data storage, a deeper understanding of the photochemical mechanisms which are present during the formation of holographic gratings has become ever more crucial. This is especially true of the photoinitiation processes, since holographic data storage requires multiple sequential short exposures. Previously, models describing the temporal variation in the photosensitizer (dye) concentration as a function of exposure have been presented and applied to two different types of photosensitizer, i.e., Methylene Blue and Erythrosine B, in a polyvinyl alcohol/acrylamide based photopolymer. These models include the effects of photosensitizer recovery and bleaching under certain limiting conditions. In this paper, based on a detailed study of the photochemical reactions, the previous models are further developed to more physically represent these effects. This enables a more accurate description of the time varying dye absorption, recovery, and bleaching, and therefore of the generation of primary radicals in photopolymers containing such dyes.

Synthesis and Photolithographic Property of Conjugated Polymers with Polyazomethine Structure

Two different polyazomethine-type conjugated polymers, poly(phenoxiazine-3,3′-dihydroxybensidine)(PZ-DHB) and poly(phenoxiazine-2,4-diamino-6-hydroxypyrimidine)(PZ-DHP) containing phenothiazine moiety and azomethine linkage in the main chain were synthesized by Schiff-base polycondensation reactions. The polymer poly(PZ-DHB) was converted to the photosensitive type, through Mitsunobu reaction by incorporation of a photocrosslinkable group, hydroxyhexyloxystyryl-2-pyridine(2-HHSP) into the polymer side chains. The photosensitive conjugated polymer, poly(PZ-DHB)-PS, exhibited both strong fluorescence emission at 555 nm and good patterning property in the standard photolithographic processes.

A comparative study of the photoinactivation of bacteria by meso-substituted cationic porphyrin, rose Bengal and methylene blue

Advances in wastewater treatment technology have led many to predict that planned wastewater reuse in agriculture will soon become more common in some regions of the world which face acute problems of water quality and quantity. The use of ecologically friendly wastewater disinfection techniques could be one of the most exciting advances in this field. The combined action of a photosensitizer (meso-substituted cationic porphyrin, TMPyP; rose Bengal, RB; methylene blue, MB) and visible light, particularly sunlight, seem to be a promising approach to microbial inactivation, potentially applicable for disinfection of domestic effluents. In the present work, photosensitization was either performed on Gram-positive and Gram-negative bacteria in pure culture (Enterococcus hirae and Escherichia coli), or carried out with wild strains in secondary wastewater effluent (enterococci and E. coli). The results described in this paper show that TMPyP is the most effective for photoinactivation of the bacterial models studied here. The relative effectiveness of RB and MB was found to be tightly linked to bacteria Gram type. Whatever the sensitizer used, Gram-negative bacteria were more resistant to photosensitization than Gram-positive strains. The order of increasing effectiveness of the photosensitizers for photoinactivation of Gram-positive bacteria (TMPyP ≥ RB > MB) and Gram-negative bacteria (TMPyP > MB > RB) remains unchanged for either pure culture or wild strains (bacterial communities in wastewater). The effectiveness of the photochemical process depends primarily on the type of microorganisms as well as the type of photosensitizers (concentration, singlet oxygen quantum yield, ionic charge), and the reaction medium.

Highly efficient in vitro photodynamic inactivation of Mycobacterium smegmatis

Efforts to control tuberculosis (TB) have been hampered by the emergence of multiple-drug resistant strains, necessitating pursuit of alternative approaches to the current antibiotic-based treatments. Herein, we explore the feasibility of photodynamic inactivation (PDI) of mycobacteria. In vitro PDI studies employing Mycobacterium smegmatis as a surrogate for Mycobacterium tuberculosis were performed examining photosensitizer (PS) type, concentration and light dose. M. smegmatis was grown to a concentration of 10(8) colony forming units (cfu) per mL, resuspended in PBS-0.5% Tween-80-containing buffer, incubated with the PS for 5 min and subsequently illuminated with white light (400-700 nm) at a fluence rate of 60 mW/cm(2) for 1, 5, 15 or 30 min (equivalent to 3.4, 18, 54 or 108 J/cm(2)). The percentage survival was determined by the ratio of the colony count from illuminated and non-illuminated control cell suspensions. The PSs examined were 5,10,15,20-tetrakis(1-methyl-4-pyridinyl)porphyrin tetratosylate (TMPyP), 5,10,15,20-tetrakis(4-N,N,N-trimethylanilinium)porphyrin tetrachloride (TNMAP), methylene blue (MB), 5,10,15,20-tetrakis(4-sulphonatophenyl)porphyrin (TSPP), 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin-Pd(II) (TCPP-Pd) and phthalocyanine tetrasulphonic acid (PhCS). Our best results demonstrate that PDI of M. smegmatis can achieve a noteworthy 5-6 log unit reduction in cfu (99.999% + viable cell eradication) when cationic PSs are employed in the nanomolar concentration range. Anionic PSs did not effectively mediate PDI of mycobacteria due to their inability to associate with the negatively charged mycobacterial cell membrane. PDI of M. smegmatis was found to be highly efficient in reducing the number of viable cells in vitro when cationic PSs were employed.

Breast cancer resistant protein (BCRP) is a molecular determinant of the outcome of photodynamic therapy (PDT) for centrally located early lung cancer

The ATP-binding cassette (ABC) transporter protein, BCRP (breast cancer resistance protein)/ABCG2 pumps out some types of photosensitizers used in photodynamic therapy (PDT) and causes resistance to the antitumor effect of PDT. The purpose of this study was to investigate the association between the expression of BCRP and the efficacy of PDT using Photofrin, or the second-generation photosensitizer, NPe6, for centrally located early lung cancers.Using human epidermoid carcinoma cells, A431 cells and the BCRP-overexpressing A431/BCRP cells, we examined the effects of BCRP expression on the effect of PDT by cell viability assay in vitro, and investigated the expression of BCRP by immunohistochemical analysis in 81 tumor samples obtained from patients with centrally located early lung cancers.The A431/BCRP cells were more resistant to Photofrin-PDT than A431 cells in vitro, and Fumitremorgin C, a specific inhibitor of BCRP, reversed the resistance.However, there was no significant difference in the antitumor effect of NPe6-PDT between these cells. All of the 81 centrally located early lung cancer lesions were BCRP-positive (2+, 45 lesions; 1+, 30 lesions) and all the patients were male and heavy smokers (>30 pack-years). The expression of BCRP significantly affected the efficacy of Photofrin-PDT in cancer lesions ≥10mm in diameter (P=0.04). On the other hand, NPe6-PDT exhibited a strong antitumor effect, regardless of the expression status of BCRP.Photofrin may be a substrate of BCRP and be pumped out from the cells, therefore, BCRP may be a molecular determinant of the outcome of Photofrin-PDT.

Solid-phase photosensitizers based on fullerene C_60 for photodynamic inactivation of viruses in biological liquids

A new type of solid-phase photosensitizer has been proposed and created on the basis of aggregated fullerene C60 for the photodynamic inactivation of pathogens in biological liquids. This paper demonstrates the chief advantage of such solid-phase systems, which is that efficient inactivation of pathogens (using influenza viruses as an example) by active forms of oxygen formed when a photosensitizer is irradiated in aqueous and biological media is combined with high photostability of the fullerene coatings and the possibility of completely extracting the photosensitizer from the biological medium after photodynamic activation.

Analysis of the photoabsorptive behavior of two different photosensitizers in a photopolymer material

Photopolymer materials are practical materials for use as holographic recording media. To further develop such materials, a deeper understanding of the photochemical mechanisms present during the formation of holographic gratings in these materials has become ever more crucial. This is especially true of the photoinitiation process, which has already received much attention in the literature. Typically the absorption mechanism varies with exposure time. This has been previously investigated in association with several effects taking place during recording. Since holographic data storage requires multiple sequential short exposures, it is necessary to verify the temporal change in photosensitizer concentration. Postexposure effects have also been discussed in the literature, however, such studies do not include effects such as photosensitizer recovery and bleaching. We report on experimental results and theoretical analysis of the recovery and bleaching mechanisms, which arise during exposure and postexposure for two different types of photosensitizers, methylene blue and erythrosine B in a polyvinylalcohol-acrylamide based photopolymer material.

Photophysics and photochemistry of zinc phthalocyanine/bovine serum albumin adducts

Zinc phthalocyanine (ZnPc) is a well known Type II (singlet oxygen mediated) hydrophobic photosensitizer with potential use in PDT. We have found that the presence of bovine serum albumin diminishes the aggregation degree of ZnPc in aqueous solution, indicating that albumins could be potentially useful carriers for this type of photosensitizer in PDT. In order to explore the photochemical and photophysical behavior of ZnPc associated to the protein, we have evaluated triplet excited state lifetime and yield, dye bleaching, oxygen consumption, formation of carbonyls and peroxides, and the spontaneous chemiluminescence emitted after photolysis. The results show that dye association to BSA modifies the photophysics and photochemistry of ZnPC. In particular the decreased yield of long lived triplets suggests singlet state and/or static triplet quenching of the bound dye by the host protein.

Band gap effect on the photocatalytic activity of supramolecular structures obtained by entrapping photosensitizers in different inorganic supports

Different metallophthalocyanines and 2,4,6-triphenylpyrylium (TP+) ions were entrapped in different inorganic supports such as Y zeolite, mesoporous MCM-41, TiO2-SiO2 and SiO2 following a specific protocol. The resulting supramolecular structures were characterized by chemical analysis and diffuse reflectance UV-vis measurements. The determination of the band gap on the basis of UV-vis measurements showed that the host is not a spectator in this process and an electronic interaction occurs that lowers the band gap of the support. The XPS measurements were performed with an in situ X-ray photoelectron spectrometer, which can be operated at pressures of up to 1 mbar at the sample. They indicated that the formation of the supramolecular structure generates a stable environment, in which the oxidation state of the metal can still be influenced by reaction of the metal center with gas molecules. The photocatalytic tests carried out in photodecomposition of dipropyl sulfide showed a good correlation between the band gap values and the photocatalytic activity for metallophthalocyanine complexes. It is remarkable that the triphenylpyrylium ion follows the same trend observed for metallophthalocyanines, although it is a different type of photosensitizer.

Visible‐Light‐Sensitized Dechlorination of Perchloroethylene

An aqueous reaction mixture containing perchloroethylene (PCE), a photosensitizer, and an electron donor was irradiated by visible lamps to facilitate a sunlight-sensitized dechlorination reaction. Various types of lamps, electron donors, and photosensitizers were examined, to compare the rates of dechlorination. Of the six photosensitizers evaluated, methylene blue was the most effective. Electron donors varied in effectiveness, as follows: trimethylamine > triethylamine > tributylamine. The intermediates and reaction products were identified by a purge-and-trap gas chromatography mass spectrometer system. The photosensitized dechlorination method degraded PCE via an electron-transfer-relay mechanism. Degradation products identified were trichloroethylene, dichloroethylenes, and chloroethylene. It seems a sequential dechlorination pathway was followed. The PCE dechlorination in a natural sunlight irradiation test was shown to be more effective than any of the simulated visible light sources. The result supports the feasibility of future development of solar-powered dechlorination remediation systems with the use of sunlight, nontoxic dyes, and electron donors.

Newly synthesized water soluble cholinium-purpurin photosensitizers and their stabilized gold nanoparticles as promising anticancer agents.

For possible future use in Photodynamic Therapy (PDT) and/or Photothermal Therapy (PTT) of cancer and screening of cancer cells a new type of ionic liquid photosensitizer –Cholinium-Purpurin-18 (Chol-Pu-18) – was synthesized and small gold (Au) nanoparticles, stabilized by this photosensitizer were prepared without adding any particular reducing agents and CTAB. UV-Vis spectroscopy and Transmission Electron Microscopy (TEM) were used for characterization of the nanoparticles and FAB-MS and NMR of the ionic liquid choline hydroxide, purpurin carboxylate and their ionic liquid type of photosensitizer were obtained.

The EEG Photoparoxysmal Response

Types of photosensitivity, prevalence and other characteristics of the photoparoxysmal response (PPR), associated seizures, effect of video games, and drug therapy are reviewed by the director of electroencephalography at the University of Illinois, Chicago.

Dying cells program their expedient disposal: serum amyloid P component upregulation in vivo and in vitro induced by photodynamic therapy of cancer

Serum amyloid P component (SAP) is known as a prototypic acute phase reactant in the mouse and the protein that binds to dying cells securing their swift disposal by phagocytes. Treatment of solid tumors by photodynamic therapy (PDT) triggers SAP production in the liver of host mice, its release in the circulation and accumulation in PDT-targeted lesions. In the present study, mouse Lewis lung carcinoma (LLC) cells treated in vitro by PDT are shown to upregulate their gene encoding SAP. This effect was manifested following PDT treatment mediated by various types of photosensitizers (Photofrin, BPD, mTHPC, ALA). Generated SAP protein was not detected in tissue supernatants but remained localized to producing PDT-treated cells. The upregulation of SAP gene was observed also in untreated IC-21 macrophages after they were co-incubated for 4 h with PDT-treated LLC cells. Based on these findings, SAP that accumulates in PDT-treated tumors may originate from both systemic sources (released from the liver as acute phase reactant) and local sources; the latter could include tumor cells directly sustaining PDT injury and macrophages invading the tumor that become stimulated by signals from these affected tumor cells. Since SAP gene upregulation in LLC cells increased with the lethality of PDT dose used for their treatment, we propose that cells sensing they are inflicted with mortal injury can turn on molecular programs insuring not only that they die an innocuous form of death (apoptosis) but also that once they are dead their elimination is (facilitated by SAP) swift and efficient.

Squaraine Dyes for Photodynamic Therapy: Study of Their Cytotoxicity and Genotoxicity in Bacteria and Mammalian Cells¶‡

Halogenated squaraine dyes are characterized by long wavelength absorption (>600 nm) and high triplet yields and therefore represent new types of photosensitizers that could be useful for photodynamic therapy. We have analyzed the cytotoxicity and genotoxicity of the bromo derivative 1, the iodo derivative 2 and the corresponding nonhalogenated dye 3 in the absence and presence of visible light. At concentrations of 1–2 μM, 1 and 2 reduced the cloning efficiency of AS52 Chinese hamster ovary cells to less than 1% under conditions that were well tolerated in the dark. Similarly, the proliferation of L5178Y mouse lymphoma cells was inhibited by photoexcited 1 and 2 with high selectivity. The squaraine 3 was much less efficient. Both 1 and 2 induced only few mutations in the gpt locus of the AS52 cells in the presence of light and were not mutagenic in the dark. No mutagenicity with and without irradiation was observed in Salmonella typhimurium TA100 and TA2638. However, both 1 and 2 plus light increased the frequency of micronuclei in AS52 cells. The results indicate that halogenated squaraines exhibit photobiological properties in vitro that are favorable for photodynamic therapeutical applications.

Phototesting in Lupus Erythematosus Tumidus-Review of 60 Patients¶

Photosensitivity is an important characteristic feature of several forms of lupus erythematosus (LE), and induction of skin lesions by UV-A and UV-B irradiation has been proved to be an optimal model for evaluating light sensitivity in patients with this disease. Because lupus erythematosus tumidus (LET) has rarely been documented in the literature and is often difficult to differentiate from other photodermatoses such as polymorphous light eruption, we performed photoprovocation tests in 60 patients with LET according to a standardized protocol. Areas of uninvolved skin on the upper back were irradiated with single doses of UV-A (100 J/cm2) and/or UV-B (1.5 minimal erythema dose) daily for three consecutive days. Interestingly, patients with LET are more photosensitive than those with subacute cutaneous lupus erythematosus, and in our study experimental phototesting revealed characteristic skin lesions in 43 patients (72%). Because of the latency period in developing positive phototest reactions, it might be difficult for these patients to link sun exposure with their skin lesions. Furthermore, our data revealed a positive correlation of antinuclear antibodies and positive provocative phototest reactions in these patients as seen for other forms of LE. In conclusion, the high incidence of positive phototest reactions in correlation with the clinical findings, history of photosensitivity and antinuclear antibodies enable the classification of LET as the most photosensitive type of LE.

Versatile photosensitizers for photodynamic therapy at infrared excitation.

A new type of photosensitizers used in photodynamic therapy, which is based on photon upconverting nanoparticles, is reported. These photosensitizers are excitable with infrared irradiation, which has several times larger tissue penetration depth than the currently available ones. They are brought close to the target cancer cells through antigen-antibody interaction with good specificity and versatility. The design is also flexible in that various photosensitive molecules can be potentially adopted into the design. Results from in vitro experiments demonstrate their promise of becoming the next generation photodynamic therapy drugs.

Photodynamic laser therapy and diagnostics of tumor localization on the basis of new types of photosensitizers

Characteristics of photophysical and photochemical processes in molecules of new symmetric indotricarbocyanine dyes in solutions and biostructures are studied. Correlations between the efficiency of these processes and the specific features of the dye molecule structure, as well as the influence of the physical and chemical parameters of the medium and exciting radiation on these processes are established.

Supramolecular nanocarriers integrated with dendrimers encapsulating photosensitizers for effective photodynamic therapy and photochemical gene delivery

Recently, biomedical applications of dendrimers, three-dimensional tree-like macromolecules, have received much attention. In this paper, we introduce new biomedical applications of functional dendrimers: dendrimers encapsulating photosensitizers composed of a center dye molecule surrounded by poly(benzyl ether) dendrons with ionic peripheral groups as a new type of photosensitizer (PS) for photodynamic therapy (PDT). Dendrimers encapsulating porphyrin and with ionic peripheral groups (DPs) spontaneously formed polyion complex (PIC) micelles through electrostatic interactions with oppositely-charged block copolymers, and showed no self-quenching of the center dye molecule inside the micellar core due to a unique DP structure, leading to remarkable in vitro photocytotoxicity. The DP-incorporated micelles showed successful treatment of choroidal neovascularization (CNV) in rats without any sign of side effects. Thus, the DP-incorporated micelles are expected to be an innovative PS formulation for successful PDT against ophthalmic diseases. In this paper, we also review polymeric micelles incorporating phthalocyanine core dendrimers (DPc) for cancer PDT and novel light-responsive supramolecular gene carriers integrated with DPc for site-directed transfection in vivo.

Quantum study on photophysical and photochemical process of a new photosensitizer: hypomycin B

Ab initio and CIS theories were employed to study a new type of perylenequinonoid photosensitizer (PQP)—hypomycin B (HMB), which has only one pair of adjacent hydroxyl group and carbonyl group in its peri-region. Geometries, Mulliken charge population, energy, and photophysical and photochemical process in excited state were discussed in detail. The results indicate that HMB exhibits quite similar intramolecular proton transfer (IPT) to perylenequinone, which offers an indirect understanding that the IPT process in perylenequinonoid derivatives (PQD) is a single proton transfer process. There exists the crossing of the potential energy surface of the singlet and triplet so that the intersystem crossing (ISC) can occur. The ISC will increase triplet quantum efficiency, which is the basis for photosensitization of PQP.

General principles of photodynamic therapy (PDT) and gastrointestinal applications.

The purpose of this review article is to describe the history of photodynamic therapy (PDT), its current medical applications, the mechanism of action, contraindications of the method, and different types of photosensitizers used. The second part of the article deals with applications for gastrointestinal diseases. The treatment of obstructing oesophageal cancer, early-stage oesophageal cancer, Barrett's esophagus, hilar cholangiocarcinoma, stomach-, colon- and pancreatic cancer are discussed. The final part focuses on future directions of PDT like certain innovative ideas, which are currently under investigation.