Tetrasulfonated Zinc Phthalocyanine Research Articles

The Efficacy of Zinc Phthalocyanine Nanoconjugate on Melanoma Cells Grown as Three-Dimensional Multicellular Tumour Spheroids.

Melanoma remains a major public health concern that is highly resistant to standard therapeutic approaches. Photodynamic therapy (PDT) is an underutilised cancer therapy with an increased potency and negligible side effects, and it is non-invasive compared to traditional treatment modalities. Three-dimensional multicellular tumour spheroids (MCTS) closely resemble in vivo avascular tumour features, allowing for the more efficient and precise screening of novel anticancer agents with various treatment combinations. In this study, we utilised A375 human melanoma spheroids to screen the phototoxic effect of zinc phthalocyanine tetrasulfonate (ZnPcS4) conjugated to gold nanoparticles (AuNP). The nanoconjugate was synthesised and characterised using ultraviolet-visible spectroscopy, a high-resolution transmission electron microscope (TEM), dynamic light scattering (DLS), and zeta potential (ZP). The phototoxicity of the nanoconjugate was tested on the A375 MCTS using PDT at a fluency of 10 J/cm2. After 24 h, the cellular responses were evaluated via microscopy, an MTT viability assay, an ATP luminescence assay, and cell death induction using annexin propidium iodide. The MTT viability assay demonstrated that the photoactivated ZnPcS4, at a concentration of 12.73 µM, caused an approximately 50% reduction in the cell viability of the spheroids. When conjugated to AuNPs, the latter significantly increased the cellular uptake and cytotoxicity in the melanoma spheroids via the induction of apoptosis. This novel Zinc Phthalocyanine Nanoconjugate shows promise as a more effective PDT treatment modality.

Innentitelbild: Photo‐RAFT Polymerization for Hydrogel Synthesis through Barriers and Development of Light‐Regulated Healable Hydrogels under NIR Irradiation (Angew. Chem. 25/2023)

Hydrogel preparation under NIR light via a photoinduced RAFT polymerization catalyzed by tetrasulfonated zinc phthalocyanine is reported by Cyrille Boyer et al. in their Research Article (e202302451). Exploiting enhanced penetration of NIR light, photoinduced gelation is effectively performed through barriers. Thiocarbonylthio groups embedded in hydrogel networks facilitate the reactivation of polymer chains under NIR wavelengths, enabling the photoinduced healing of hydrogels through non-transparent barriers.

Photo‐RAFT Polymerization for Hydrogel Synthesis through Barriers and Development of Light‐Regulated Healable Hydrogels under NIR Irradiation

AbstractWe report an aqueous and near‐infrared (NIR) light mediated photoinduced reversible addition–fragmentation chain transfer (photo‐RAFT) polymerization system catalyzed by tetrasulfonated zinc phthalocyanine (ZnPcS4−) in the presence of peroxides. Taking advantage of its fast polymerization rates and high oxygen tolerance, this system is successfully applied for the preparation of hydrogels. Exploiting the enhanced penetration of NIR light, photoinduced gelation is effectively performed through non‐transparent biological barriers. Notably, the RAFT agents embedded in these hydrogel networks can be reactivated on‐demand, enabling the hydrogel healing under NIR light irradiation. In contrast to the minimal healing capability (<15 %) of hydrogels prepared by free radical polymerization (FRP), RAFT‐mediated networks display more than 80 % recovery of tensile strength. Although healable polymer networks under UV and blue lights have already been established, this work is the first photochemistry system using NIR light, facilitating photoinduced healing of hydrogels through thick non‐transparent barriers.

Photo-RAFT Polymerization for Hydrogel Synthesis through Barriers and Development of Light-Regulated Healable Hydrogels under NIR Irradiation.

We report an aqueous and near-infrared (NIR) light mediated photoinduced reversible addition-fragmentation chain transfer (photo-RAFT) polymerization system catalyzed by tetrasulfonated zinc phthalocyanine (ZnPcS4-) in the presence of peroxides. Taking advantage of its fast polymerization rates and high oxygen tolerance, this system is successfully applied for the preparation of hydrogels. Exploiting the enhanced penetration of NIR light, photoinduced gelation is effectively performed through non-transparent biological barriers. Notably, the RAFT agents embedded in these hydrogel networks can be reactivated on-demand, enabling the hydrogel healing under NIR light irradiation. In contrast to the minimal healing capability (< 15%) of hydrogels prepared by free radical polymerization (FRP), RAFT-mediated networks display more than 80% recovery of tensile strength. Although healable polymer networks under UV and blue lights have already been established, this work is the first photochemistry system using NIR light, facilitating photoinduced healing of hydrogels through thick non-transparent barriers.

Active targeted photodynamic therapeutic effect of silver-based nanohybrids on melanoma cancer cells

Malignant melanoma is aggressive cancer that metastasizes along with the heterogeneity at the molecular and cellular levels, thereby reducing overall therapeutic efficacy. In the present research, the concept of photodynamic therapy (PDT) was investigated on silver-based nanohybrids for the treatment of A375 melanoma cancer cells. Hence, two different nanoparticles (NPs) namely Ag-PEG NPs and core/shell Ag@mSiO2 NPs were fabricated and conjugated to zinc phthalocyanine tetrasulfonate (ZnPcS4) photosensitizer (PS). Folic acid (FA) as a targeting moiety was also decorated onto the surface of nanohybrids to selectively target the folate receptors that are overexpressed on the A375 cells. Ultimately, the PDT efficacy of both ZnPcS4/Ag-PEG-FA and ZnPcS4/Ag@mSiO2-FA nanohybrids were compared via ATP viability, flow cytometry, and reactive oxygen species (ROS) assays. The obtained near-spherical shaped nanohybrids had zeta potential of -4.03 ± 0.3 mV for ZnPcS4/Ag-PEG-FA, and -14.4 ± 0.6 mV for the ZnPcS4/Ag@mSiO2-FA. A significant PDT effect was observed for the cells exposed to 674 nm laser irradiation after incubation with ZnPcS4/Ag@mSiO2-FA with ∼92%* ± 1.1 cell death compared to ∼70%* ± 2.9 cell death for ZnPcS4/Ag-PEG-FA nanohybrids owing to the higher generation of ROS for the former nanohybrids. The majority of the cell death was induced via apoptosis rather than necrosis as the nanohybrids successfully localized in mitochondria. The overall finding of this study concluded that an active targeting strategy significantly enhanced the cellular uptake of the nanohybrids compared to passive targeting. Moreover, strong surface plasmon-PS resonance coupling in ZnPcS4/Ag@mSiO2-FA nanohybrids enhanced singlet oxygen generation in comparison to the PS alone or ZnPcS4/Ag-PEG-FA nanohybrids.

An aqueous photo-controlled polymerization under NIR wavelengths: synthesis of polymeric nanoparticles through thick barriers.

We report an aqueous and near-infrared (NIR) light mediated photoinduced reversible addition-fragmentation chain transfer (photo-RAFT) polymerization system using tetrasulfonated zinc phthalocyanine (ZnPcS4 -) as a photocatalyst. Owing to the high catalytic efficiency and excellent oxygen tolerance of this system, well-controlled polyacrylamides, polyacrylates, and polymethacrylates were synthesized at fast rates without requiring deoxygenation. Notably, NIR wavelengths possess enhanced light penetration through non-transparent barriers compared to UV and visible light, allowing high polymerization rates through barriers. Using 6.0 mm pig skin as a barrier, the polymerization rate was only reduced from 0.36 to 0.21 h-1, indicating potential for biomedical applications. Furthermore, longer wavelengths (higher λ) can be considered an ideal light source for dispersion photopolymerization, especially for the synthesis of large diameter (d) nanoparticles, as light scattering is proportional to d 6/λ 4. Therefore, this aqueous photo-RAFT system was applied to photoinduced polymerization-induced self-assembly (photo-PISA), enabling the synthesis of polymeric nanoparticles with various morphologies, including spheres, worms, and vesicles. Taking advantage of high penetration and reduced light scattering of NIR wavelengths, we demonstrate the first syntheses of polymeric nanoparticles with consistent morphologies through thick barriers.

Photoacoustic molecular imaging-escorted adipose photodynamic-browning synergy for fighting obesity with virus-like complexes.

Photodynamic therapy and adipose browning induction are two promising approaches to reverse obesity. The former strategy acts rapidly and locally, whereas the latter has a more gradual and widespread effect. Despite their complementarity, they have rarely been combined and imaged non-invasively in vivo. Here we introduce an adipose-targeting hepatitis B core protein complex that contains a traceable photosensitizer (ZnPcS4 (zinc phthalocyanine tetrasulfonate)) and a browning agent (rosiglitazone) that allows simultaneous photodynamic and browning treatments, with photoacoustic molecular imaging. After intravenous injection in obese mice, the complex binds specifically to white adipose tissues, especially those rich in blood supply, and drives adipose reduction thanks to the synergy of ZnPcS4 photodynamics and rosiglitazone browning. Using photoacoustic molecular imaging, we could monitor the changes induced by the treatment, which included complex activity, lipid catabolism and angiogenesis. Our findings demonstrate the anti-obesity potential of our feedback-based synergic regimen orchestrated by the targeted hepatitis B core complex.

Enhanced fluorescence of tetrasulfonated zinc phthalocyanine by graphene quantum dots and its application in molecular sensing/imaging.

When excited at 435nm, tetra-sulfonate zinc phthalocyanine (ZnPcS4 ) emitted dual fluorescence at 495 and 702nm. The abnormal fluorescence at 495nm was experimentally studied and analyzed in detail for the first time. The abnormal fluorescence at 495nm was deduced to originate from triplet-triplet (T-T) energy transfer of excited phthalocyanine (3 *ZnPcS4 ). Furthermore, graphene quantum dots (GQDs) enhanced the 495nm fluorescence quantum yield (Q) of ZnPcS4 . The fluorescence properties of ZnPcS4 -GQDs conjugate were retained in a cellular environment. Based on the fluorescence of ZnPcS4 -GQDs conjugate, we designed and prepared an Apt29/thrombin/Apt15 sandwich thrombin sensor with high specificity and affinity. This cost-saving, simple operational sensing strategy can be extended to use in sensing/imaging of other biomolecules.

Iontophoresis Improved Growth Reduction of Invasive Squamous Cell Carcinoma in Topical Photodynamic Therapy.

This study examined the potential of iontophoresis in topical photodynamic therapy (PDT) of human invasive squamous cells carcinomas (SCC). SCC was induced in nude BALB/c mice by subcutaneous injection of A431 cells. Tumor penetration and distribution of the photosensitizer tetrasulfonated zinc phthalocyanine (ZnPcS4) was investigated after 10 and 30 min of in vivo iontophoresis of a gel containing ZnPcS4. PDT was performed immediately after iontophoresis using laser at 660 nm with a dose of irradiation of 100 J/cm2 and irradiance of 48 mW/cm2 while tumor growth was measured for 30 days. Iontophoresis increased ZnPcS4 penetration into tumors by 6-fold after 30 min when compared with passive delivery. Confocal microscopy analysis showed that ZnPcS4 was homogeneous distributed within deep regions of the tumor after iontophoresis. Irradiation of the tumors immediately after iontophoresis showed reduction in tumor size by more than 2-fold when compared to non-treated tumors. Iontophoretic-PDT treated tumors presented large areas of necrosis. The study concluded that iontophoretic delivery of photosensitizers could be a valuable strategy for topical PDT of invasive SCC.

Spectroscopic insights on selfassembly and excited state interactions between rhodamine and phthalocyanine molecules

The absorption and fluorescence spectra as well as fluorescence lifetimes of tetrasulfonated zinc phthalocyanine ZnPc(SO3Na)4 were measured in the absence and presence of four rhodamine dyes, Rhodamine B (RB), Ethyl rhodamine B (ERB), Rhodamine 6G (R6G), Rhodamine 110 (R110), and Pyronine B (PYB). The ground state complexes of phthalocyanine–(Rhodamine)2 were observed which exhibit new absorption bands. The binding constants are all very large (0.86×105–0.22×108M−1), suggesting rhodamine–phthalocyanine pairs are very good combinations for efficient selfassembly. Both the fluorescence intensity and the lifetime values of ZnPc(SO3Na)4 were decreased by the presence of rhodamines. The structural effect of rhodamines on selfassembly is significant. The ground state binding and dynamic quenching capability is PYB>R6G>ERB>RB>R110. The dynamic fluorescence quenching is due to the photoinduced electron transfer (PET). The PET rate constant is very large and in the order of 1013M−1s−1, much greater than kf and kic (in the order of 108M−1s−1), which means that the PET efficiency is almost 100%. Therefore the non-covalent Pc–rhodamine is a very good pair of donor/acceptor for potential efficient solar energy conversion.

Antitumor activity of photodynamic therapy performed with nanospheres containing zinc-phthalocyanine

BackgroundThe increasing incidence of cancer and the search for more effective therapies with minimal collateral effects have prompted studies to find alternative new treatments. Among these, photodynamic therapy (PDT) has been proposed as a very promising new modality in cancer treatment with the lowest rates of side effects, revealing itself to be particularly successful when the photosensitizer is associated with nanoscaled carriers. This study aimed to design and develop a new formulation based on albumin nanospheres containing zinc-phthalocyanine tetrasulfonate (ZnPcS4-AN) for use in the PDT protocol and to investigate its antitumor activity in Swiss albino mice using the Ehrlich solid tumor as an experimental model for breast cancer.MethodsEhrlich tumor’s volume, histopathology and morphometry were used to assess the efficacy of intratumoral injection of ZnPcS4-AN in containing tumor aggressiveness and promoting its regression, while the toxicity of possible treatments was assessed by animal weight, morphological analysis of the liver and kidneys, hemogram, and serum levels of total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (GGT), alkaline phosphatase, creatinine and urea. In order to evaluate the efficacy of PDT, groups of animals treated with intratumoral injection of doxorubicin (Dox) were also investigated.ResultsIntratumoral injection of ZnPcS4-AN was found to be efficient in mediating PDT to refrain tumor aggressiveness and to induce its regression. Although tumor volume reduction was not significant, PDT induced a remarkable increase in the necrosis area seen in the tumor’s central region, as in other experimental groups, including tumor and Dox treated groups, but also in the tumor’s peripheral region. Further, PDT showed minimal adverse effects. Indeed, the use of ZnPcS4-AN in mediating PDT revealed anti-neoplastic activity similar to that obtained while using intratumoral Dox therapy.ConclusionsPDT mediated by the new formulation ZnPcS4-AN enhanced the inhibition of tumor growth while producing practically no adverse effects and thus emerges as a very promising nanotechnology-based strategy for solid cancer treatment.

Liquid Crystal Nanodispersions Enable the Cutaneous Delivery of Photosensitizer for Topical PDT: Fluorescence Microscopy Study of Skin Penetration

Topical photodynamic therapy (PDT) has been applied to almost all types of nonmelanoma skin cancer and numerous superficial benign skin disorders. Strategies to improve the accumulation of photosensitizer in the skin have been studied in recent years. Although the hydrophilic phthalocyanine zinc compound, zinc phthalocyanine tetrasulfonate (ZnPcSO4) has shown high photodynamic efficiency and reduced phototoxic side effects in the treatment of brain tumors and eye conditions, its use in topical skin treatment is currently limited by its poor skin penetration. In this study, nanodispersions of monoolein (MO)-based liquid crystalline phases were studied for their ability to increase ZnPcSO4 uptake by the skin. Lamellar, hexagonal and cubic crystalline phases were prepared and identified by polarizing light microscopy, and the nanodispersions were analyzed by dynamic light scattering. In vitro skin penetration studies were performed using a Franz's cell apparatus, and the skin uptake was evaluated in vivo in hairless mice. Aqueous dispersions of cubic and hexagonal phases showed particles of nanometer size, approximately 224 ±10 nm and 188 ± 10 nm, respectively. In vitro skin retention experiments revealed higher fluorescence from the ZnPcSO4 in deeper skin layers when this photosensitizer was loaded in the hexagonal nanodispersion system when compared to both the cubic phase nanoparticles and the bulk crystalline phases (lamellar, cubic and hexagonal). The hexagonal nanodispersion showed a similar penetration behavior in animal tests. These results are important findings, suggesting the development of MO liquid crystal nanodispersions as potential delivery systems to enhance the efficacy of topical PDT. Keywords: Liquid crystalline phases, nanodispersion, skin cancer, skin penetration, photodynamic therapy, zinc phthalocyanine

Photophysical and photochemical studies of sulfur containing phthalocyanine derivatives in the presence of folic acid

The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320μs).

A delivery system to avoid self-aggregation and to improve in vitro and in vivo skin delivery of a phthalocyanine derivative used in the photodynamic therapy

The hydrophilic character and aggregation phenomena exhibited by the photosensitizer zinc phthalocyanine tetrasulfonate (ZnPcSO 4) make it difficult for this compound to penetrate the skin, and reduce the compound's photodynamic efficacy. A microemulsion (ME) was developed to increase the skin penetration of ZnPcSO 4 while avoiding its aggregation. Ternary phase diagrams composed of surfactants (Span® 80/Tween® 80), canola oil and a propylene glycol (PG)/water mixture (3:1) were constructed as a basis for choosing an adequate ME preparation. Rheological, electrical conductivity, dynamic light scattering and zeta potential studies were carried out to characterize the ME formulations. Monomerization of ZnPcSO 4 in the ME was determined photometrically and fluorometrically. In vitro skin penetration and retention of the compound in the skin were measured using porcine ear skin mounted on a diffusion cell apparatus. The in vivo accumulation 6 h after ZnPcSO 4 application was determined fluorometrically in hairless mice skin. Confocal laser scanning microscopy was used to visualize ZnPcSO 4 distribution in the skin. A ME composed of canola oil:surfactant:PG-water at 38:47:15 (w/w/w) was chosen for ZnPcSO 4. This was oil-in-water with internal phase diameter of 15.7 ± 0.15 nm. Spectroscopic techniques confirmed that the ME was able to keep ZnPcSO 4 in its monomeric form. In the in vitro penetration of ZnPcSO 4 in the stratum corneum (SC) and in epidermis (without stratum corneum) with dermis ([E + D]) was 33.0- and 28.0-fold higher, respectively compared to the control solution of the drug. In vivo studies, confirmed that when the ME was used as carrier, ZnPcSO 4 concentrations in the SC and [E + D] were about 1.6- and 5.6-fold higher, respectively, than controls. Visualization of ZnPcSO 4 skin penetration by confocal laser scanning microscopy confirmed that the ME increased both penetration and biodistribution of this photosensitizer in the skin.

A graphene sheet as an efficient electron acceptor and conductor for photoinduced charge separation

Tetrasulfonated zinc phthalocyanine (Pc) was bound to graphene (G) sheets by the π–π stacking supermolecular method. The few-layer graphene sheets were obtained by chemically reducing graphite oxide and characterized by AFM, IR and UV–vis absorption methods. Photoinduced electron transfer (PET) within the nano assembly is revealed by laser flash photolysis, time resolved and steady state fluorescence, as well as UV–vis absorption techniques. A graphene sheet can be attached by up to 52,000 Pc molecules to form a super molecule G(Pc) 52,000, in which many Pc molecules can be simultaneously photoexcited to the S 1 state. One graphene sheet can simultaneously quench thousands of excited Pcs with a large rate constant of the order of 10 16 M −1 s −1 by PET. A graphene sheet not only accepts electrons from the excited Pcs on it but also delivers the captured electrons to its unexcited Pcs to form (Pc +) n G(Pc −) n , so that a large electron charge (i.e. n >> 1) is separated between unlinked Pc molecules with a small energy loss. These novel features of PET are explained by the following unique properties of graphene: (i) its excellent electron-transport and multi-electron-accepting ability, (ii) its multi-chromophore binding and concurrent multi-photon absorbing ability.

REMOVAL OF SELECTED PHARMACEUTICALS USING OCTOLIG®, A SUPPORTED CHELATING AGENT

The possibility of removing certain pharmaceuticals from wastewater was tested using Octolig ,a commercially available material with polyethyldiamine moieties covalently attached to high-surface area silica gel. Selected drugs and drug models were subjected to column chromatography for removal by means of ion encapsulation, the effectiveness of which would depend upon having appropriate anionic functional groups. Removal of methylene blue with quaternary ammonium groups was (statistically) unsuccessful. In contrast, complete success was attained for removal of each of three xanthenylbenzenes (rose bengal, eosin Y, erythrosine) that have both phenolic and carboxylic acid groups, as is the case with two of the top five prescribed drugs in the US. Moreover, quantitative removal was obtained for zinc phthalocyaninetetrasulfonate (ZPS) and lissamine green B, which have sulfonate groups. Finally, quantitative removal was obtained for amoxicillin, one of the top five most prescribed drugs in the US (in 2008).

Pd -catalyzed Heck reaction for the synthesis of isomeric metallo tetravinylsulfo phthalocyanines and their photosensitizing properties

Tetrasulfonated zinc phthalocyanine (ZnPcS(4)) is a potent sensitizer for photodynamic therapy of various medical conditions. Depending on its mode of preparation the material consists of mixtures of ortho and meta sulfonated derivatives as well as regioisomers with different photodynamic potency. To study the effect of the site of substitution on biological parameters that contribute to overall photodynamic efficacy, a series of pure ortho- and meta-tetravinylsulfonated metallo phthalocyanines MPc-o/m-(VS)(4) were prepared from the corresponding tetraiodo phthalocyanines using the palladium-catalyzed cross-coupling reaction (Heck reaction). Compared to the tetrasulfonated phthalocyanines, the tetravinylsulfonated derivatives are more hydrophobic and their Q-band absorption maxima are red-shifted. While their in vitro phototoxicity is in the same range as the mixed isomeric sulfonated derivatives, ortho-substituted MPc-o-(VS)(4) are more photocytotoxic as compared to their corresponding meta analogs. Although the central metal ion and site of substitution affect aggregation, the tendency to aggregate did not correlate with photodynamic potency nor did overall cell uptake. Instead, intracellular localization at both mitochondrial and lysosomal membranes appears to be the major factor explaining the augmented activity of the ortho substituted derivatives.

Effects of zinc phthalocyanine tetrasulfonate-based photodynamic therapy on rat brain isolated mitochondria

PDT has been used in the treatment of malignant brain tumors for the last 2 decades. It is based on the interaction of a photosensitizer (PS) and light of an appropriate wavelength, with generation of oxygen species, mainly singlet oxygen. Brain is particularly susceptible to oxidative stress; therefore the study of PDT effects on cerebral mitochondria might provide mechanistic insights into the action of the therapy, contributing to its optimization. In the present study, we addressed the mitochondrial toxicity of the second generation PS, zinc phthalocyanine tetrasulfonate (ZnPcS 4), on rat brain isolated mitochondria, by investigating both intrinsic toxicity and photodynamic action. At higher concentrations (15 and 25 μM/mg protein) ZnPcS 4 caused (a) inhibition of state-3 respiration and (b) decrease of RCR and ADP/O. Electrochemical potential, state-4 respiration and Ca 2+ retention capacity were not affected. Cytochrome c release was not observed. Coupled with 600 or 1800 mJ/cm 2 laser irradiation, ZnPcS 4 (5 μM/mg protein) caused more intense effects on state 3, RCR and ADP/O; moreover state-4 respiration and membrane potential were affected. Besides that, Ca 2+ and cytochrome c release were induced. Cyclosporine A (CsA) decreased Ca 2+ release and ameliorated the electrochemical potential, suggesting that membrane permeability transition (MPT) might be involved in the photodynamic effect. The low intrinsic toxicity and the high photodynamic effect on rat brain mitochondria induced by ZnPcS 4, allied to its improved photophysical properties, might indicate its potential for the treatment of malignant brain tumors.

Oxygen Dependence of Two‐photon Activation of Zinc and Copper Phthalocyanine Tetrasulfonate in Jurkat Cells

Photodynamic therapy (PDT), the use of light-activated drugs, is a promising treatment of cancer as well as several nonmalignant conditions. However, the efficacy of one-photon (1-gamma) PDT is limited by hypoxia, which can prevent the production of the cytotoxic singlet oxygen ((1)O(2)) species, leading to tumor resistance to PDT. To solve this problem, we propose an irradiation protocol based on a simultaneous, two-photon (2-gamma) excitation of the photosensitizer (Ps). Excitation of the Ps triplet state leads to an upper excited triplet state T(n) with distinct photochemical properties, which could inflict biologic damage independent of the presence of molecular oxygen. To determine the potential of a 2-gamma excitation process, Jurkat cells were incubated with zinc or copper phthalocyanine tetrasulfonate (ZnPcS(4) or CuPcS(4)). ZnPcS(4) is a potent (1)O(2) generator in 1-gamma PDT, while CuPcS(4) is inactive under these conditions. Jurkat cells incubated with either ZnPcS(4) or CuPcS(4) were exposed to a 670 nm continuous laser (1-gamma PDT), 532 nm pulsed-laser light (2-gamma PDT), or a combination of 532 and 670 nm (2-gamma PDT). The efficacy of ZnPcS(4) to photoinactivate the Jurkat cells decreased as the concentration of oxygen decreased for both the 1-gamma and 2-gamma protocols. In the case of CuPcS(4), cell phototoxicity was measured only following 2-gamma irradiation, and its efficacy also decreased at a lower oxygen concentration. Our results suggest that for CuPcS(4) the T(n) excited state can be populated after 2-gamma irradiation at 532 nm or the combination of 532 and 670 nm light. Dependency of phototoxicity upon aerobic conditions for both 1-gamma and 2-gamma PDT suggests that reactive oxygen species play an important role in 1-gamma and 2-gamma PDT.

Zinc Phthalocyanine Tetrasulfonate (ZnPcS4): A New Photosensitizer for Photodynamic Therapy in Choroidal Neovascularization

The aim of this sutdy was to demonstrate the selective localization of a new photosensitizer, zinc phthalocyanine tetrasulfonate (ZnPcS(4)), in rat eyes and investigate the ability of ZnPcS(4) to produce a photochemical closure of experimental choroidal neovascularization (CNV) upon irradiation with a 670-nm laser light. To determine the biodistribution of ZnPcS(4) and the optimal timing of laser irradiation after photosensitizer administration, fluorescence microscopy with ZnPcS(4) was performed. CNV was created in the fundi of Brown-Norway rats using the argon laser model and documented by fluorescein angiography (FFA) and optical coherence tomography (OCT). Photodynamic therapy (PDT) was performed at the dose of 2.0 mg/m(2) and laser fluences of 600 mW/cm(2) on the CNV and on normal retina and choroid. Treatment outcomes were assessed by FFA and OCT and confirmed by light and electron microscopy. Fluorescence microscopy demonstrated intense ZnPcS(4) fluorescence from the CNV, choriocapillaris, and retinal pigment epithelial cells. Peak ZnPcS(4) intensities in the choriocapillaris and CNV were detected at 10-20 min after an intravenous injection. FFA and OCT indicated that irradiation with 670 nm of laser light 20 min after a ZnPcS(4) injection produced a complete closure of CNV with minimal damage to the overlying retina. Histologic studies, using light and electron microscopy, demonstrated CNV endothelial cell necrosis with minimal damage to the surrounding tissues. ZnPcS(4) selectively localizes to the choriocapillaris and CNV in rats, resulting in the occlusion of laser-induced CNV with minimal damage to the retina tissues. ZnPcS(4) -PDT is a potential new strategy for the treatment of macular degeneration and other human diseases manifesting as CNV.