Zinc tetrasulphophthalocyanine as a photodynamic sensitizer for biomolecules

Monomeric zinc tetrasulphophthalocyanine in aqueous buffer is an effective sensitizer for the photo-oxidation of amino acids and nucleic acid bases and for the photodynamic inactivation of the enzyme, lysozyme; these reactions appear to be mediated by singlet oxygen.     

Tritolylporphyrin dimer as a new potent hydrophobic sensitizer for photodynamic therapy of melanoma.

We report the synthesis, photochemical and photophysical properties and preliminary studies on biological effect of a new tritolylporphyrin dimer (T-D). Absorption and emission properties of T-D suggest its possible use in photodynamic therapy. T-D is capable of singlet oxygen production with 0.8 quantum yield. It also has a high photostability. The photodynamic properties of the dimer were examined following the growth of SKMEL 188 (human melanoma) cells irradiated with red light (cut off < 630 nm). The surviving fraction of the cells decreased about 3-fold (vs. non-irradiated cells) for an 81 J/cm dose. Our results suggest that tritolylporphyrine dimer T-D may be an interesting hydrophobic sensitizer for photodynamic therapy.     

9-Nitroanthracene derivative as a precursor of anthraquinone for photodynamic therapy

Anthraquinones are typical photosensitizers used in photodynamic therapy (PDT). However, systemic toxicity is a major problem for anthraquinones due to their ability not only to bind DNA but also to cause oxidative stress even without photoirradiation. To avoid such disadvantages in cancer therapy, we designed and synthesized a novel 9-nitroanthracene derivative (1) as a precursor of anthraquinone. Under photoirradiation, 1 is converted into anthraquinone via generation of nitric oxide as confirmed by ESR. Strong DNA cleavage specifically at guanine under photoirradiation was also observed, characteristic of DNA-cleaving reactions by photoirradiated anthraquinones. We propose development of 1 as an alternative approach toward PDT that reduces the systemic toxicity of anthraquinone.     

Nanoparticles as vehicles for delivery of photodynamic therapy agents

Photodynamic therapy (PDT) in cancer treatment involves the uptake of a photosensitizer by cancer tissue followed by photoirradiation. The use of nanoparticles as carriers of photosensitizers is a very promising approach because these nanomaterials can satisfy all the requirements for an ideal PDT agent. This review describes and compares the different individual types of nanoparticles that are currently in use for PDT applications. Recent advances in the use of nanoparticles, including inorganic oxide-, metallic-, ceramic-, and biodegradable polymer-based nanomaterials as carriers of photosensitizing agents, are highlighted. We describe the nanoparticles in terms of stability, photocytotoxic efficiency, biodistribution and therapeutic efficiency. Finally, we summarize exciting new results concerning the improvement of the photophysical properties of nanoparticles by means of biphotonic absorption and upconversion.     

Indocyanine green clearance varies as a function of N-acetylcysteine treatment in a murine model of acetaminophen toxicity

Standard assays to assess acetaminophen (APAP) toxicity in animal models include determination of ALT (alanine aminotransferase) levels and examination of histopathology of liver sections. However, these assays do not reflect the functional capacity of the injured liver. To examine a functional marker of liver injury, the pharmacokinetics of indocyanine green (ICG) were examined in mice treated with APAP, saline, or APAP followed by N-acetylcysteine (NAC) treatment.Male B6C3F1 mice were administered APAP (200 mg/kg IP) or saline. Two additional groups of mice received APAP followed by NAC at 1 or 4 h after APAP. At 24 h, mice were injected with ICG (10 mg/kg IV) and serial blood samples (0, 2, 10, 30, 50 and 75 min) were obtained for determination of serum ICG concentrations and ALT. Mouse livers were removed for measurement of APAP protein adducts and examination of histopathology. Toxicity (ALT values and histology) was significantly increased above saline treated mice in the APAP and APAP/NAC 4 h mice. Mice treated with APAP/NAC 1 h had complete protection from toxicity. APAP protein adducts were increased in all APAP treated groups and were highest in the APAP/NAC 1 h group. Pharmacokinetic analysis of ICG demonstrated that the total body clearance (Cl_T) of ICG was significantly decreased and the mean residence time (MRT) was significantly increased in the APAP mice compared to the saline mice. Mice treated with NAC at 1 h had Cl_T and MRT values similar to those of saline treated mice. Conversely, mice that received NAC at 4 h had a similar ICG pharmacokinetic profile to that of the APAP only mice. Prompt treatment with NAC prevented loss of functional activity while late treatment with NAC offered no improvement in ICG clearance at 24 h. ICG clearance in mice with APAP toxicity can be utilized in future studies testing the effects of novel treatments for APAP toxicity.     

Carbaporphyrin ketals as potential agents for a new photodynamic therapy treatment of leishmaniasis

Dimethyl and diethyl carbaporphyrin ketals inhibit the growth of Leishmania tarentolae promastigotes in vitro. The concentration dependency of the inhibitory effect was tested using the MTT assay. The presence of reactive oxygen species, such as singlet oxygen and superoxide, was detected using electron paramagnetic resonance spectroscopy with selected spin traps and confocal microscopy in cultures exposed to these carbaporphyrin ketals. These unique porphyrinoids show promise as potent inhibitors of Leishmania.     

Meso-tetraphenylporphyrin in liposomes as a suitable photosenzitizer for photodynamic therapy of tumors.

The suitability of a liposomal form of hydrophobic nonsulfonated meso-tetraphenyl porphyrin (TPP) for the photodynamic therapy of tumors was investigated. TPP was solubilized in small unilamellar lipid vesicles prepared by extrusion on a LIPOSOFAST apparatus. These samples were studied by laser-excited time resolved luminescence and triplet-triplet absorption spectroscopy. In this lipid environment TPP was still an efficient singlet oxygen producer, as indicated by the characteristic singlet oxygen phosphorescence at 1270 nm in D2O, when excited with a 28 ns laser pulse at 412 nm. Moreover, unlike with sulfonated TPP (TPPS4), liposomal TPP showed the reduced decay rates of TPP triplet-states with the increasing time of pre-illumination by a Xenon lamp. This was shown in an indirect way, based upon the appearance of a second component of the luminescence decay at 1270 nm in D2O; and by direct TPP triplet state monitoring, detecting triplet-triplet absorption at 440 nm in H2O. The deactivation of higher triplet states was delayed upon pre-illumination. This reflects an irreversible interaction of singlet oxygen with membrane lipids, thus demonstrating the potential of the liposomal form of TPP to efficiently disintegrate tumor cell membranes and to be a suitable preparation for the photodynamic therapy.     

Luminol as the light source for in situ photodynamic therapy

Presently, the light sources used in photodynamic therapy are high intensity lasers or light emitting diodes, making it unsuitable for large-volume tumors and those located deep inside the body. To overcome this limitation, we propose an in situ light source to excite the photosensitizer to generate toxic singlet oxygen and kill tumor cells directly. In this research, luminol served as the in situ light source in 5-aminolevulinic acid-mediated photodynamic treatment of Caco-2 cell cultures. 72 h after luminol excitation the viability of the treated cells significantly decreased compared to the control cells in assays including cell viability, cytotoxicity, flow cytometry and fluorescence confocal microscopy. According to the results, we suggested luminol could be used as an in situ light source for 5-aminolevulinic acid-mediated photodynamic therapy. This method would have great potential to extend the application of photodynamic therapy to tumors located deep inside the body.     

Light-harvesting ionic dendrimer porphyrins as new photosensitizers for photodynamic therapy

Photodynamic therapy (PDT) is a promising therapeutic modality for treatment of solid tumors. In this study, third-generation aryl ether dendrimer porphyrins (DPs) with either 32 quaternary ammonium groups (32(+)DPZn) or 32 carboxylic groups (32(-)DPZn) were evaluated as a novel, supramolecular class of photosensitizers for PDT. DPs showed a different cell-association profile depending on the positive or negative charge on the periphery, and both DPs eventually localized in membrane-limited organelles. In contrast, protoporphyrin IX (PIX), which is a hydrophobic and relatively low molecular weight photosensitizer used as a control in this study, diffused through the cytoplasm except the nucleus. Confocal fluorescent imaging using organelle-specific dyes indicated that PIX induced severe photodamage to disrupt membranes and intracellular organelles, including the plasma membrane, mitochondrion, and lysosome. On the other hand, cells treated with DPs kept the characteristic fluorescent pattern of such organelles even after photoirradiation. However, notably 32(+)DPZn achieved remarkably higher (1)O(2)-induced cytotoxicity against LLC cells than PIX. Furthermore, both dendrimer porphyrins had far lower dark toxicity as compared with PIX, demonstrating their highly selective photosensitizing effect in combination with a reduced systemic toxicity.     

Metallobacteriochlorophylls as potential dual agents for photodynamic therapy and chemotherapy

A theoretical analysis of bacteriochlorophyll a containing its non-native divalent metal ions: Co, Ni, Cu, Zn, Ru, Rh, Pd, and Pt, has been carried out by means of density functional theory (DFT) calculations. The main stress was put on the derivatives with metals, which already found applications as coordination compounds in anti-tumor therapy (Ru, Pt, Pd, and Rh). The idea was to combine their cytotoxic properties with the known suitability of bacteriochlorophylls macrocycle for photodynamic therapy. The geometries of the studied systems are compared and reveal a number of similarities. The cores of the modified bacteriochlorophylls are flat, and the introduced metal ions lie in plane of the macrocycle, showing its large ability to accommodate metal ions of different sizes. However, four metal–nitrogen bonds, linking the central ions with the macrocycle ligand, are not equivalent. Metals are the strongest attached to nitrogens, which come from the pyrrole, which is fused with isocyclic ring. Based on the known spectroscopic data, the absorption properties of the proposed systems are predicted. Finally, it is found that all studied metal–macrocycle adducts are stable in aqueous media. The only exceptions are Mg-BChla (the finding is reflected by experimental facts) and Zn-BChla. The predicted high stability of Ru-, Rh-, Pt- and Pd-bacteriochlorophylls might turn out beneficial for therapeutic purposes.     

Tumor microenvironment-activated nanosystems with selenophenol substituted BODIPYs as photosensitizers for photodynamic therapy

NIR-light-absorbing photosensitizers with the capability of selective localization and activation in tumor regions are of great importance for practical photodynamic therapy (PDT). Here, selenophenol substituted BODIPYs were designed and synthesized as new photosensitizers for PDT. One of these obtained BODIPYs, IBSeOV, possesses an intense and low energy absorption with a high singlet oxygen quantum yield (Φ_Δ = 60%). Considering manganese dioxide (MnO₂) nanosheets as versatile nanocarriers in cancer theranostics, nanosystem IBSeOV/MnO₂ was then fabricated to furnish tumor environment selective activation. Such designed nanoplatform allowed for GSH-controllable ¹O₂ production and exhibited low cytotoxicity in dark but good photocytotoxicity to cancer cells. The in vivo antitumor outcome suggested the high treatment efficiency of IBSeOV/MnO₂ for tumor therapy.     

光动力疗法治疗感染性疾病的动物模型

光动力疗法(photodynamic therapy,PDT)是利用特定波长的激发光照射生物靶标上的光敏剂,从而产生活性氧并有效杀伤多种耐药病原体的新型治疗方式,具有作用广、安全可控、不易耐受等优点。大量体外实验已证实了PDT疗效,但目前动物实验数据较少,且治疗参数不一,一定程度上影响了PDT在临床治疗中的广泛应用。本文综述近年来PDT用于体内抗感染治疗的动物模型构建、治疗方案设计等方面的研究进展,为未来PDT抗感染研究及临床应用提供参考。     

Soybean oil as a possible solubilizing and vehicular medium for zinc phthalocyanine in photodynamic therapy.

Soybean oil (SBO) is used as a medium to solubilize zinc phthalocyanine (ZnPc), a known photosensitizer, which has been found to be of potential use in photodynamic therapy. It absorbs red light in this medium at 670 nm with good molar absorptivity comparable to its value in most organic solvents (2.45 x 10(5) M(-1) cm(-1)). The wavelength of the fluorescence emission band peaked at 700 nm when excited at 591 nm, and when excited at 560 nm, the emission band was observed at 680 nm. The characteristic emission band of ZnPc at the near end of the visible spectral region suggests that this compound exists in this medium in a monomeric form, a form most useful in photo therapeutic applications. Moreover, the excitation wavelength, observed in the far-red region, precludes minimal effect, if any, of skin photonecrosis if this medium is used in PDT. A fluorescence spectral analysis of the ZnPc-SBO solution carried out for thirty-eight days indicates that this solution is stable within this time frame. No toxicity was detected when this solution was seeded in human endothelial cells in a culture well for 36 hr and also when injected subcutaneously into the nude and Balb C mice. In both cases the ZnPc was observed to clear from the injected area in a reasonable time. This fact coupled with its good solubilizing property for ZnPc and its virtual nontoxicity may make soybean oil a possible vehicular medium for transporting useful photosensitizers to target cells in photodynamic therapy and related applications.     

Evaluation of human erythrocytes as model cells in photodynamic therapy

The role of erythrocytes as targets in photodynamic therapy is a controversially discussed topic in the literature. Therefore five different, but well known photosensitisers (three zinc phthalocyanines, tetrabenzoporphine and pheophorbide a delivered in liposomes were used for photodynamic treatment of human erythrocytes. The phototoxic effect on these cells showed pronounced differences. It was in the range: zinc phthalocyanine = pheophorbide a > tetrabenzoporphine > zinc octa-n-alkyl phthalocyanines. Data from the zinc octa-n-alkyl phthalocyanines were compared with photodynamic effects within cutaneous cell lines, treated under the same experimental conditions. The results show that erythrocytes are unlikely to make good models for predicting the efficiency of the photosensitiser in general, and the same applies to cells other than erythrocytes and in vivo. Possible reasons could be differences in dye accumulation. However, erythrocytes may well serve as model cells to explore the cellular and molecular mechanisms of photodynamic treatment.     

Novel 3,6-bis(imidazolidine)acridines as effective photosensitizers for photodynamic therapy

The photoeffect of new proflavine derivatives with DNA-binding and antitumour activities, 3,6-bis((1-alkyl-5-oxo-imidazolidin-2-yliden)imino)acridine hydrochlorides (AcrDIMs), was studied to evaluate them as potential photosensitizers for photodynamic antitumor therapy. EPR measurements showed that superoxide radical anion and singlet oxygen were produced upon irradiation of AcrDIMs with UV-A light (>300 nm) in the presence of molecular oxygen. This indicates that AcrDIMs may act as photosensitizers. The most active pentyl-AcrDIM and hexyl-AcrDIM displayed photocytotoxic effect toward the mouse lymphocytic leukemia cell line L1210 and human ovarian cancer cells A2780. Antitumor activity of pentyl-AcrDIM increased as high as about 12 times (72 h incubation) after irradiation of A2780 cells (365 nm, 1.05 J/cm²). The photocytotoxicity seems to be associated with oxidative stress. Concerning the cell cycle, flow cytometry showed an arrest in the S-phase already 4 h after irradiation. In a comet assay, no genotoxicity of AcrDIMs was found. Typical morphologic changes and formation of DNA-ladders indicated induction of apoptotic cell death, though no activation of caspase-3 was observed. Investigation of intracellular localization of pentyl-AcrDIM confirmed its partial accumulation in mitochondria and lysosomes. After irradiation of the A2780 cells, colocalization of pentyl-AcrDIM with monodansylcadaverine, a lysosomal dye, was proven, suggesting that lysosomes in the irradiated cells may be involved in the cell death.     

Evaluation of dipeptide-derivatives of 5-aminolevulinic acid as precursors for photosensitizers in photodynamic therapy

N-terminal-blocked and N-terminal-free pseudotripeptide Gly-Gly and Gly-Pro derivatives of 5-aminolevulinic acid (ALA) esters were synthesized as potential specific substrates for cellular peptidases and precursors for the production of the photosensitizer protoporphyrin IX (PpIX). These precursors were evaluated using human cell lines of either carcinoma or endothelial origin. N-blocked or N-free dipeptides-ALA-ethyl esters, but not tripeptides-ALA-ethyl esters (or dipeptides-ALA-ethyleneglycols,) were substrates for cellular peptidases and were metabolized to ALA. The precursors were hydrolyzed intracellularly involving serine-proteases and metalloproteases. Cell selectivity for human endothelial or carcinoma cells was observed for some of these dipeptides-ALA. Thus drugs coupled to Gly-Gly-/Gly-Pro-derivatives may selectively target defined cells in human cancer, depending on specific cellular activating pathways expressed by the cells.     

Synthesis and biological evaluation of new chlorin derivatives as potential photosensitizers for photodynamic therapy

Three new water-soluble chlorin derivatives 3, 5 and 8 for potential use as photosensitizers in photodynamic therapy (PDT) for cancer were synthesized from photoprotoporphyrin IX dimethyl ester (1). The in vivo biodistribution and clearance of chlorin derivatives 3, 5 and 8 were investigated in tumor-bearing mice. Iminodiacetic acid derivative 8 showed the greatest tumor-selective accumulation among the new chlorin derivatives with maximum accumulation in tumor tissue at 3 h after intravenous injection and rapid clearance from normal tissues within 24 h after injection. The in vivo therapeutic efficacy of PDT using 8 was evaluated by measuring tumor growth rates in tumor-bearing mice with 660 nm light-emitting diode irradiation at 3 h after injection of 8. Tumor growth was significantly inhibited by PDT using 8. These results indicate that iminodiacetic acid derivative 8 is useful as a new photosensitizer to overcome the disadvantages of photosensitizers that are currently in clinical use.