Biological activities of phthalocyanines--III. Photoinactivation of V-79 Chinese hamster cells by tetrasulfophthalocyanines

Phthalocyanine and Its Formulations: A Promising Photosensitizer for Cervical Cancer Phototherapy

Cervical cancer is one of the most common causes of cancer-related deaths in women worldwide. Despite advances in current therapies, women with advanced or recurrent disease present poor prognosis. Photodynamic therapy (PDT) has emerged as an effective therapeutic alternative to treat oncological diseases such as cervical cancer. Phthalocyanines (Pcs) are considered good photosensitizers (PS) for PDT, although most of them present high levels of aggregation and are lipophilic. Despite many investigations and encouraging results, Pcs have not been approved as PS for PDT of invasive cervical cancer yet. This review presents an overview on the pathophysiology of cervical cancer and summarizes the most recent developments on the physicochemical properties of Pcs and biological results obtained both in vitro in tumor-bearing mice and in clinical tests reported in the last five years. Current evidence indicates that Pcs have potential as pharmaceutical agents for anti-cervical cancer therapy. The authors firmly believe that Pc-based formulations could emerge as a privileged scaffold for the establishment of lead compounds for PDT against different types of cervical cancer.

Advanced photodynamic agent from chondroitin sulfate/zinc phthalocyanine conjugate

In order to improve the therapeutic effect of zinc phthalocyanines (ZnPc), a photoactive nanodrug was prepared with acetylated chondroitin sulfate (AcCS), utilizing a simple chemical method. AcCS/ZnPc nanodrugs have a unimodal size distribution below 200 nm and a negative surface charge due to AcCS located on the nanodrug surface. In organic solvent such as DMSO or DMF, it has strong fluorescence intensity and generates abundant singlet oxygen. However, in aqueous solvent, AcCS/ZnPc nanodrugs developed a self-organized form which induced reducing fluorescence intensity and singlet oxygen generation. The cellular uptake of the nanodrug was determined using a cell lysis test and confocal microscopy observation. The results indicated that cellular internalization efficiency of the nanodrug was 1.7–2.1 times higher than that of free ZnPc . Also, the phototoxicity of the nanodrug was detected via MTT assay with or without light. Although free ZnPc did not exhibit cytotoxicity in both light and dark condition, the nanodrug exhibited increasing cytotoxicity after irradiation. We therefore suggest that AcCS/ZnPc nanodrugs may have promising applications as new photodynamic agents for the clinical treatment of various tumors.

Crossed and linked histories of tetrapyrrolic macrocycles and their use for engineering pores within sol-gel matrices

The crossed and linked histories of tetrapyrrolic macrocycles, interwoven with new research discoveries, suggest that Nature has found in these structures a way to ensure the continuity of life. For diverse applications porphyrins or phthalocyanines must be trapped inside solid networks, but due to their nature, these compounds cannot be introduced by thermal diffusion; the sol-gel method makes possible this insertion through a soft chemical process. The methodologies for trapping or bonding macrocycles inside pristine or organo-modified silica or inside ZrO₂ xerogels were developed by using phthalocyanines and porphyrins as molecular probes. The sizes of the pores formed depend on the structure, the cation nature, and the identities and positions of peripheral substituents of the macrocycle. The interactions of the macrocyclic molecule and surface Si-OH groups inhibit the efficient displaying of the macrocycle properties and to avoid this undesirable event, strategies such as situating the macrocycle far from the pore walls or to exchange the Si-OH species by alkyl or aryl groups have been proposed. Spectroscopic properties are better preserved when long unions are established between the macrocycle and the pore walls, or when oligomeric macrocyclic species are trapped inside each pore. When macrocycles are trapped inside organo-modified silica, their properties result similar to those displayed in solution and their intensities depend on the length of the alkyl chain attached to the matrix. These results support the prospect of tuning up the pore size, surface area, and polarity inside the pore cavities in order to prepare efficient catalytic, optical, sensoring, and medical systems. The most important feature is that research would confirm again that tetrapyrrolic macrocycles can help in the development of the authentic pore engineering in materials science.

Role of Metal Phthalocyanine in Redox Complex Conductivity of Polyaniline and Aniline Black

Polyaniline (PA) and aniline black (AB) were prepared in powder form by the chemical method of oxidative polymerization, from which free-standing thin films were obtained by solvent evaporation using N-methyl pyrrolidinone ( NMP ). The thin films contained 2, 4, 6 or 8 wt% AB. Electrical measurements showed that the samples containing 4% AB exhibited the highest photoconductivity of the four concentrations. Thus there appears to be a critical ratio of PA to AB for maximum photoconductivity. Annealing up to 570 K has little effect on the conductivity. Upon adding a small quantity of copper phthalocyanine ( CuPc ) to the PA + AB, the electrical conductivity increased considerably and the optical absorption was extended from the UV to the near IR. The electrical conductivity mechanism is a consequence of a redox process, since AB is the oxidized state of PA and, upon illumination, there is an exchange of charge carriers. The extension of the range of optical absorption upon addition of CuPc is interpreted to suggest that CuPc photosensitizes the material and enhances the carrier transport process in the redox couple. The activation energy from the temperature-dependent conductivity and the band gap from the electrolyte electroreflectance method were determined. The activation energy for 0.4% CuPc is lowest (0.52 eV) and the corresponding band gap is determined to be 3.0 eV. This organic compound could be a good candidate for inexpensive, reliable and efficient solar energy-converting devices.

Like a bolt from the blue: phthalocyanines in biomedical optics

The purpose of this review is to compile preclinical and clinical results on phthalocyanines (Pcs) as photosensitizers (PS) for Photodynamic Therapy (PDT) and contrast agents for fluorescence imaging. Indeed, Pcs are excellent candidates in these fields due to their strong absorbance in the NIR region and high chemical and photo-stability. In particular, this is mostly relevant for their in vivo activation in deeper tissular regions. However, most Pcs present two major limitations, i.e., a strong tendency to aggregate and a low water-solubility. In order to overcome these issues, both chemical tuning and pharmaceutical formulation combined with tumor targeting strategies were applied. These aspects will be developed in this review for the most extensively studied Pcs during the last 25 years, i.e., aluminium-, zinc- and silicon-based Pcs.

Synthesis and photophysical properties of silicon phthalocyanines with axial siloxy ligands bearing alkylamine termini

Eleven silicon phthalocyanines which can be grouped into two homologous series [SiPc[OSi(CH3)2(CH2)(n)N(CH3)2]2, n = 1-6 (series 1), and SiPc[OSi(CH3)2(CH2)3N((CH2)(n)H)2]2, n = 1-6 (series 2)] as well as an analogous phthalocyanine, SiPc[OSi(CH3)2(CH2)3NH2]2, were synthesized. The ground state absorption spectra, the triplet state dynamics, and singlet oxygen quantum yields of 10 of these phthalocyanines were measured. All compounds displayed similar ground state absorption spectral properties in dimethylformamide solution with single Q band maxima at 668 +/- 2 nm and B band maxima at 352 +/- 1 nm. Photoexcitation of all compounds in the B bands generated the optical absorptions of the triplet states which decayed with lifetimes in the hundreds of microseconds region. Oxygen quenching bimolecular rate constants near 2 x 10(9) M(-1) s(-1) were measured, indicating that energy transfer to oxygen was exergonic. Singlet oxygen quantum yields, phi(delta), were measured, and those phthalocyanines in which the axial ligands are terminated by dimethylamine residues at the end of alkyl chains having four or more methylene links exhibited yields near > or = 0.35. Others gave singlet oxygen quantum yields near 0.2, and still others showed singlet oxygen yields of <0.1. The reduced singlet oxygen yields are probably caused by a charge transfer quenching of the 1pi,pi* state of the phthalocyanine by interaction with the lone pair electrons on the nitrogen atoms of the amine termini. In some cases, these can approach and interact with the electronically excited pi-framework, owing to diffusive motions of the flexible oligo-methylene tether.

Distribution of metal-free sulfonated phthalocyanine in subcutaneously transplanted murine tumors

Metal-free sulfonated phthalocyanine with the average number of sulfonate groups per molecule 2.4 (H(2)PcS(2.4)) was recently proved to be an efficient photosensitizer for the photodynamic therapy. Fluorescence spectral imaging microscopy was applied here to study localization and relative concentration of H(2)PcS(2.4) with micron-scale resolution in subcutaneously transplanted murine tumors: Ehrlich mammary gland carcinoma (EC), Lewis lung carcinoma (LLC), P388 lymphoid leukemia (P388) and B16 melanoma (B16). The study of cryogenic tissue sections prepared 24 h after H(2)PcS(2.4) intravenous injection revealed that H(2)PcS(2.4) was present in all tissue structures in the monomeric photoactive state. The preferential accumulation of H(2)PcS(2.4) was documented in tumor cells and adjacent non-tumor tissues (skin structures, fatty tissue, connective tissue enriched in fibrous component and infiltrated with fibroblasts and macrophages) for all the studied tumor models. P388 and B16 were stained with H(2)PcS(2.4) less than adjacent skin structures, whereas EC and LLC accumulated H(2)PcS(2.4) alike or higher than particular skin structures. Staining of EC and LLC was similar and ca. 1.4 and 2 times higher than that of B16 and P388, respectively, thus revealing the differences in ability of particular tumor strains to H(2)PcS(2.4) accumulation. The H(2)PcS(2.4) concentration in remote healthy tissues (skin, muscles and connective tissue) was 2-3 times lower as compared with the analogous tissue structures from the tumor area, whereas subcutaneous fatty tissue staining did not depend on the tissue-to-tumor distance. The tissue distribution of H(2)PcS(2.4) predefines the combined action of two photodynamic damage mechanisms: eradication of tumor due to the direct tumor cell destruction and suppression of tumor growth due to the injury of growth supporting system.

Chelation with metal is not essential for antitumor photodynamic activity of sulfonated phthalocyanines

It is generally assumed that a central metal is essential for the efficiency of phthalocyanines in photodynamic therapy (PDT) of cancer. Contrary to the set opinion, the results of the present study indicate that the metal-free sulfonated phthalocyanines (H2PcSn, where n is the number of sulfonate groups per molecule) possess a considerable photoactivity. The relative phototoxicities of H2PcS1.5, H2PcS2.4, H2PcS3.1 and H2PcS3.8 on HEp2 human epidermoid carcinoma cells were 3.3, 20, 3.3 and 1, respectively, thus demonstrating dependence of the activity on the sulfonation degree, known for metallo-PcSn. A significant delay in tumor growth and a decrease in tumor regrowth rate were observed in mice after PDT with H2PcS2.4. The antitumor effect declined in the order H2PcS2.4 > H2PcS3.1 > H2PcS1.5 and vanished for H2PcS3.8. We demonstrate here that the high photodynamic activity of H2PcS2.4 can be explained by its physicochemical properties in living cells and tissues. Thus, H2PcSn (n is about 2) can be considered as a new alternative in PDT of light-accessible neoplasms and further clinic-oriented studies are warranted.

Chloroaluminum phthalocyanine tetrasulfonate delivered via acid-labile diplasmenylcholine-folate liposomes: intracellular localization and synergistic phototoxicity

Folate-diplasmenylcholine (1,2-di-O-(Z-1'-hexadecenyl)-sn-glycero-3-phosphocholine; DPPlsC) liposomes have been shown to greatly enhance the potency of water-soluble antitumor agents via a selective folate-mediated uptake and acid-catalyzed endosomal escape mechanism (Rui et al. J. Am. Chem. Soc., 1998; 120:11213--18). This study describes an adaptation of this strategy for the delivery of chloroaluminum phthalocyanine tetrasulfonate ([AlPcS(4)](4-)), a water-soluble sensitizer used in photodynamic therapy, in a binary targeting scheme designed to enhance both its tumor selectivity and phototoxicity. [AlPcS(4)](4-)/DPPlsC:folate liposomes (9.8 microM bulk concentration, 2.5 mM intraliposomal concentration) were substantially more phototoxic to folate-deficient KB cells than 12.5 microM free [AlPcS(4)](4-) after a 30 min irradiation (630-910 nm). Considerable differences in phototoxicity were observed, however, between the commercially-available AlPcS(4)(4-) and an HPLC purified sample of [AlPcS(4)](4-) due to an increased tendency for the latter to aggregate. Experiments with [AlPcS(4)](4-)/DPPC:folate and folate-free [AlPcS(4)](4-)/DPPlsC liposomes (acid-insensitive and non-targeted controls, respectively) showed significantly reduced phototoxicities under the same illumination conditions. Our results imply that higher concentrations of water-soluble sensitizers can be delivered to target cells using the folate receptor-mediated pathway, which can change both the biodistribution and intracellular localization of the sensitizer when acid-labile DPPlsC liposomes are used as the delivery vehicle. Potential advantages of this approach include the use of lower bulk [AlPcS(4)](4-) concentrations, rapid plasma clearance of free [AlPcS(4)](4-), and better phototoxic responses, due to higher intracellular [AlPcS(4)](4-) concentrations combined with reduced collateral photodamage arising from misguided sensitizer accumulation, thereby enhancing the selective phototoxicity of PDT treatments.

Eradication of multiple myeloma and breast cancer cells by TH9402-mediated photodynamic therapy: implication for clinical ex vivo purging of autologous stem cell transplants

High-dose chemotherapy combined with autologous transplantation using bone marrow or peripheral blood-derived stem cells (PBSC) is now widely used in the treatment of hematologic malignancies as well as some solid tumors like breast cancer (BC). However, some controversial results were recently obtained in the latter case. The presence of malignant cells in the autograft has been associated with the recurrence of the disease, and purging procedures are needed to eliminate this risk. The aim of this study was to evaluate the potential of the photosensitizer 4,5-dibromorhodamine methyl ester (TH9402), a dibrominated rhodamine derivative, to eradicate multiple myeloma (MM) and BC cell lines, while sparing more than 50% of normal pluripotential blood stem cells from healthy volunteers. The human BC MCF-7 and T-47D and MM RPMI 8226 and NCI-H929 cell lines were used to optimize the photodynamic purging process. Cell concentration and the cell suspension thickness as well as the dye and light doses were varied in order to eventually treat 1-2 L of apheresis. The light source consisted of two fluorescent scanning tubes emitting green light centered about 515 nm. The cellular uptake of TH9402 was measured during the incubation and washout periods and after photodynamic treatment (PDT) using spectrofluorometric analysis. The limiting dilution assay showed that an eradication rate of more than 5 logs is obtained when using a 40 min incubation with 5-10 microM dye followed by a 90 min washout period and a light dose of 5-10 J/cm2 (2.8 mW/cm2) in all cell lines. Agitating the 2 cm thick cell suspension containing 20 x 10(6) cells/mL during PDT was essential for maximal photoinactivation. Experiments on mobilized PBSC obtained from healthy volunteers showed that even more drastic purging conditions than those found optimal for maximal eradication of the malignant cell lines were compatible with a good recovery of hematopoietic progenitors cells. The absence of significant toxicity towards normal hematopoietic stem cells, combined with the 5 logs eradication of cancer cell lines induced by this procedure suggests that TH9402 offers an excellent potential as an ex vivo photodynamic purging agent for autologous transplantation in MM and BC treatment.

Role of oxygen in the phototoxicity of phthalocyanines

The presence of molecular oxygen is a determinant in the phototoxicity of phthalocyanines, and photosensitized oxidation is the accepted chemical mechanism for photo-dynamic action. However, it is difficult to establish whether the process is initiated by a type I electron transfer, or by a type II energy transfer reaction to form singlet oxygen. Usually, the involvement of singlet oxygen in photodamage has been indicated by the inhibition of the biological effect by a competitive physical or chemical singlet oxygen quencher, or by a rate increase in D2O, in which singlet oxygen has a longer lifetime than in H2O. Unfortunately, these techniques are not completely specific for singlet oxygen. Moreover, thermodynamic considerations suggest that photoinduced electron abstraction from appropriate biomaterials could compete with singlet oxygen production under in vivo conditions. This likely source of one electron-oxidized primary radicals, which can provide the precursors of the oxidative damage in phthalocyanine photosensitization, suggests the possibility of modulated toxicity by interaction with chemical additives. Examples of such additives recently studied are ascorbate, tocopherol and quercetin, all of which are natural antioxidants.

Photodynamic effects of new silicon phthalocyanines: in vitro studies utilizing rat hepatic microsomes and human erythrocyte ghosts as model membrane sources

Photodynamic therapy (PDT) of cancer is a modality that relies upon the irradiation of tumors with visible light following selective uptake of a photosensitizer by the tumor tissue. There is considerable emphasis to define new photosensitizers suitable for PDT of cancer. In this study we evaluated six phthalocyanines (Pc) for their photodynamic effects utilizing rat hepatic microsomes and human erythrocyte ghosts as model membrane sources. Of the newly synthesized Pc, two showed significant destruction of cytochrome P-450 and monooxygenase activities, and enhancement of lipid peroxidation, when added to microsomal suspension followed by irradiation with approximately 675 nm light. These two Pc named SiPc IV (HOSiPcOSi[CH3]2[CH2]3N[CH3]2) and SiPc V (HOSiPc-OSi[CH3]2[CH2]3N[CH3]3+I-) showed dose-dependent photodestruction of cytochrome P-450 and monooxygenase activities in liver microsomes, and photoenhancement of lipid peroxidation, lipid hydroperoxide formation and lipid fluorescence in microsomes and erythrocyte ghosts. Compared to chloroaluminum phthalocyanine tetrasulfonate, SiPc IV and SiPc V produced far more pronounced photodynamic effects. Sodium azide, histidine, and 2,5-dimethylfuran, the quenchers of singlet oxygen, afforded highly significant protection against SiPc IV- and SiPc V-mediated photodynamic effects. However, to a lesser extent, the quenchers of superoxide anion, hydrogen peroxide and hydroxyl radical also showed some protective effects. These results suggest that SiPc IV and SiPc V may be promising photosensitizers for the PDT of cancer.

Biological activities of phthalocyanines--XVI. Tetrahydroxy- and tetraalkylhydroxy zinc phthalocyanines. Effect of alkyl chain length on in vitro and in vivo photodynamic activities

Zinc phthalocyanine substituted with four hydroxyl groups attached to the macrocycle, either directly or via spacer chains of three or six carbon atoms, were tested for their photodynamic ability to inactivate Chinese hamster lung fibroblasts (line V-79) in vitro, and to induce regression of EMT-6 tumours grown subcutaneously in Balb/c mice. Their potential to inflict direct cell killing during photodynamic therapy was investigated by examining vascular stasis immediately following photoirradiation using fluorescein as a marker, and also by an in vivo/in vitro EMT-6 cell survival assay. Both of the tetraalkylhydroxy substituted zinc phthalocyanines are effective photodynamic sensitisers in vivo with the tetrapropylhydroxy compound exhibiting about twice the activity of the tetrahexylhydroxy analogue. The differences in activities were accentuated in vitro, the tetrapropylhydroxy compound was two orders of magnitude more potent than the tetrahexylhydroxy analogue in photoinactivating V-79 cells. The tetrahydroxy compound lacking spacer chains failed to exhibit photodynamic activity in either system. Tumour response with the active compounds was preceded by vascular stasis immediate following irradiation which suggests, together with the absence of activity in the in vivo/in vitro assay, that tumour regression involves an indirect response to the photodynamic action rather than direct cell killing. These data demonstrate the importance of the spatial orientation of functional groups around the macrocycle of photosensitisers for their efficacy in the photodynamic therapy of cancer.

Biological activities of phthalocyanines. XIII. The effects of human serum components on the in vitro uptake and photodynamic activity of zinc phthalocyanine

The effect of human serum components on the photodynamic activity of zinc phthalocyanine (ZnPc) toward Chinese hamster fibroblasts (line V-79) was studied. Photodynamic activities were correlated with cellular uptake of radiolabeled [65Zn]ZnPc, which allowed corrections to be made for the amount of sensitizer present in the cells at the time of irradiation and to express photodynamic efficiencies on a cellular dye concentration basis. All serum components, with the exception of high-density lipoproteins, inhibit uptake of ZnPc by V-79 cells, when compared to incubation of ZnPc with the same cells in serum-free medium. High-density lipoproteins increased ZnPc uptake by 23%, but the photodynamic efficiency corrected for the cellular ZnPc concentration was unaffected. Very low-density lipoprotein and globulins decreased ZnPc cell uptake but likewise did not affect the cellular photodynamic efficiency of the dye. In contrast low-density lipoprotein and albumin, while inhibiting ZnPc cell uptake, increased the cellular photodynamic efficiency of ZnPc, suggesting that these proteins facilitate localization of the dye at cellular targets sensitive to photodynamic damage and vital to cell survival. We conclude from these results that association of ZnPc with serum components can have important, and widely differing, effects on both degree of uptake and cellular distribution of the photosensitizer.

Photobleaching of 1,3-diphenylisobenzofuran by novel phthalocyanine dye derivatives

As part of a wider programme to identify novel photosensitizers for photodynamic therapy, the ability of a number of phthalocyanine dyes, including some novel copper phthalocyanine derivatives with a range of water solubilities, to produce potentially cytotoxic species in solution was examined. The experiments were performed in dimethylformamide using 1,3-diphenylisobenzofuran (DPIBF) as the scavenger. The study revealed that all the dyes tested produced DPIBF photobleaching on illumination in vitro, but with widely different (greater than 12x) rates. The possible correlation of DPIBF photobleaching rates with a number of the dyes' properties is discussed.

Photodynamic inactivation of retroviruses by phthalocyanines: the effects of sulphonation, metal ligand and fluoride

The photodynamic inactivation of retroviruses was investigated using aluminium and zinc phthalocyanine (Pc) derivatives. The N2 retrovirus packaged in either of the two murine cell lines, Psi2 and PA317, was used as a model for enveloped viruses. AlPc derivatives were found to be more effective photodynamically for inactivation of the viruses than the corresponding ZnPc derivatives. Sulphonation of the Pc macrocycle reduced its photodynamic activity progressively for both AlPc and ZnPc. Fluoride at 5 mM during light exposure completely protected viruses against inactivation by AlPc. In the presence of F-, inactivation by the sulphonated derivatives AlPcS1 and AlPcS4 was reduced 2.5- and twofold respectively. In a biological membrane (erythrocyte ghosts), F- had no significant effect on AlPcS4-sensitized lipid peroxidation. Under similar conditions, cross-linking of spectrin monomers in ghosts is drastically inhibited (E. Ben-Hur and A. Orenstein, Int. J. Radiat. Biol., 60 (1991) 293-301). Since Pc derivatives do not inactivate non-enveloped viruses, it is hypothesized that inactivation occurs by photodynamic damage to envelope protein(s). Substitution of sulphonic acid residues reduces the binding of Pc derivatives to the envelope protein(s), thereby diminishing their photodynamic efficacy and the ability of F- to modify it.

Photodynamic effects of chloroaluminum phthalocyanine tetrasulfonate are mediated by singlet oxygen: in vivo and in vitro studies utilizing hepatic microsomes as a model membrane source

Chloroaluminum phthalocyanine tetrasulfonate (AlPcTS) is a promising photosensitizer for the photodynamic therapy (PDT) of cancer. In this study, we investigated the in vivo and in vitro photodestruction of hepatic microsomal membranes by AlPcTS and studied the role of reactive oxygen species in this process. Irradiation of hepatic microsomes prepared from AlPcTS-pretreated SENCAR mice to approximately 675 nm light resulted in rapid destruction of cytochrome P450 and associated monooxygenase activities, and enhancement of lipid peroxidation in a light-dose-dependent manner. The specificity of AlPcTS and light dependency on photodestruction of microsomal membranes was confirmed by Western blot analysis. Similar results were obtained when AlPcTS was added in vitro to a suspension of hepatic microsomes prepared from control animals followed by irradiation to approximately 675 nm light. Among the quenchers of singlet oxygen, superoxide anion, hydrogen peroxide, and hydroxyl radical, only the quenchers of singlet oxygen such as sodium azide, histidine, and 2,5-dimethyl furan afforded substantial protection in a dose-dependent manner against AlPcTS-mediated photodestruction of cytochrome P450 and associated monooxygenase activities, and photoenhancement of lipid peroxidation under both in vivo and in vitro conditions. These results suggest that lipid-rich microsomal membranes may be the potential targets of cell injury by AlPcTS-based PDT and that this process is mediated by singlet oxygen.

Protection by the fluoride ion against phthalocyanine-induced photodynamic killing of Chinese hamster cells

When a dilute F- solution was added to a culture of Chinese hamster cells that had been preincubated with an aluminium phthalocyanine sensitizer derived from AlPcCl, the photosensitivity of the cells was markedly reduced compared to control cells not treated with F-. Under the same treatment conditions, the reduction in [3H]thymidine incorporation into cellular DNA caused by light and this sensitizer and the production of DNA-protein crosslinks caused by light and this sensitizer were also inhibited by F-. In contrast, the killing of Chinese hamster cells, the reduction of thymidine incorporation by the cells, and the production of DNA-protein crosslinks in the cells caused by the combination of light and either Photofrin II or the silicon phthalocyanine HOSiPcOSi(CH3)2(CH2)3-N(CH3)2 were not inhibited by F-. We conclude that the aluminium phthalocyanine sensitizer used is largely or completely AlPc(OH)(H2O), that it is converted to a fluoro complex by F-, and that this compound probably is a less efficient generator of photochemical damage at a critical cellular target(s) than is AlPc(OH)(H2O). The inhibition of thymidine incorporation and DNA-protein crosslink formation indicates that the effects of F- can be expressed at intracellular sites. It is further concluded that the silicon phthalocyanine sensitizer and Photofrin II do not interact significantly with F-.

Distribution and photodynamic effect of disulphonated aluminium phthalocyanine in the pancreas and adjacent tissues in the Syrian golden hamster

Necrosis of small volumes of tumour tissue with photodynamic therapy (PDT) can be achieved relatively easily. For this to be clinically relevant, it is essential to know what the same treatment parameters do to adjacent normal tissues into which the tumour has spread. For pancreatic cancers, local spread to vital structures is common. We have studied chemical extraction, microscopic fluorescence kinetics and photodynamic effects of disulphonated aluminum phthalocyanine (AlS2Pc) in normal pancreas and adjacent tissues in hamsters. Chemical extraction exhibited a peak duodenal concentration of AlS2Pc 48 h after sensitisation, with levels much higher than in stomach and pancreas. With microscopic fluorescence photometry highest levels were seen in duodenal submucosa and bile duct walls 48 h after photosensitisation. Pancreatic ducts, duodenal mucosa and gastric mucosa and submucosa exhibited intermediate fluorescence with relatively weak fluorescence in pancreatic acinar tissue and the muscle layer of the stomach. As expected, on the basis of fluorescence intensity and chemical extraction studies, the duodenal and bile duct wall were the most vulnerable tissues to photodynamic therapy. When the dose of 5 mumol kg-1 of sensitiser was used, duodenal perforations, gastric ulcers and transudation of bile from the bile duct occurred. However, the lesions in the stomach and bile duct healed without perforation or obstruction, so only the duodenum was at risk of serious, irreversible damage. Using a lower dose of photosensitiser markedly reduced damage.

Photocytotoxic efficacy of sulphonated species of aluminium phthalocyanine against cell monolayers, multicellular spheroids and in vivo tumours

The problem of relying solely on in vitro data to predict photosensitiser efficacy was demonstrated by examining the uptake and the ability to mediate photocytotoxicity of mono-, di-, tri- and tetra-sulphonated species of chloroaluminium phthalocyanine (AlS1-4Pc) in monolayer cultures of murine Colo 26 cells and in both monolayer and spheroid cultures of human WiDr cells. Cells treated in vitro, whether in monolayer or as spheroids, with the less sulphonated derivatives, AlS1Pc and AlS2Pc, were more susceptible to photocytotoxicity than those treated with AlS3Pc, cells treated with AlS4Pc were even less susceptibile to the cytotoxic effects of light irradiation. Generally these results mirrored the cellular uptake in vitro. When WiDr spheroids were increased in size from 250 microns to 500 microns there was a reduction in uptake of AlS1Pc and AlS2Pc which was reflected by the decreased sensitivity of the larger spheroids to the effects of light irradiation. AlS1Pc had no effect against Colo 26 cells growing as s.c. tumours in syngeneic BALB/c mice; whereas AlS3Pc, AlS2Pc and AlS4Pc produced significant reductions in tumour weights 5 days post laser light irradiation. Of these, AlS2Pc had the most dramatic effect on the colony forming efficiency of tumour cells recovered 24 h after PDT. While, despite their effects on tumour size, AlS3Pc and AlS4Pc scarcely affected the subsequent viability of cells from dissociated tumours. Thus the in vitro efficacy of the sulphonated species of phthalocyanines is not necessarily predictive of their in vivo effectiveness.

Phthalocyanine-induced photodynamic changes of cytoplasmic free calcium in Chinese hamster cells

Exposure to light of Chinese hamster cells preloaded with chloroaluminum phthalocyanine causes an immediate increase of cytoplasmic free calcium, [Ca2+], from about 0.2 microM to 1 microM within 5 min after illumination. This increase was dose-dependent within the biological dose range, reaching a plateau at a dose that kills 99.5% of the cells. Fluoride addition prior to light exposure protected against cell killing and reduced the increase of [Ca2+]i. These findings raise the possibility that changes in [Ca2+]i after photodynamic treatment may be relevant to cell killing and/or other biological responses of the cells, e.g. release of eicosanoids.

Sensitizer for photodynamic therapy of cancer: a comparison of the tissue distribution of Photofrin II and aluminum phthalocyanine tetrasulfonate in nude mice bearing a human malignant tumor

The distribution of Photofrin II (P-II) and aluminum phthalocyanine tetrasulfonate (AIPCS4) in tissues of BALB/c nu/nu nude mice bearing the LOX human melanoma was measured fluorimetrically at different times after intraperitoneal injection of the drugs, 20 mg/kg body weight. The plasma levels of the drugs as well as the excretion in feces and urine were also determined. The plasma concentrations of both drugs were found to build up in a similar manner during the first 30 min after injection. Thereafter, the plasma level of AIPCS4 decreased exponentially with an elimination half-life of 1.5 hr. The kinetics of elimination of P-II from the plasma were consistent with a 2-compartment model, with 90% of sensitizer lost with a half-life of about 5 hr, and the remaining fraction with a half-life of 30 hr. About 80% of the injected dose of P-II was excreted in the feces during the 7-days following injection, while 77% of AIPCS4 was excreted in the urine during the same period. After injection of a dose of 20 mg/kg, the concentrations of P-II in the LOX tumor as well as in the skin, muscle, brain, heart, lung, kidney and liver increased for about 24 hr, then remained constant or decreased slowly for the next 48 hr, after which they decreased slightly faster. On the other hand, the concentrations of APICS4 in most tissues as well as in the tumor peaked at about 30 min, then decreased with a half-life of between 1.5 and 3 hr. The tumor/skin concentration ratio was about 1 for both drugs (1-24 hr after injection). The tumor/muscle concentration ratio was about 2 for P-II at all sampling times, and maximally 10 (at 18 hr after injection) for AIPCS4. In the present tumor model, the tumor/tissue concentration ratio for all tissues at 1 hr and at 24 hr after the injection was equal for the 2 drugs or higher for AIPCS4.

Sulfonated phthalimidomethyl aluminum phthalocyanine: the effect of hydrophobic substituents on the in vitro phototoxicity of phthalocyanines

The photocytotoxicity of sulfonated phthalimidomethyl aluminum phthalocyanine, a more hydrophobic photosensitizer as compared to phthalocyanine substituted with sulfonate groups only, was investigated. Inclusion of 1-2 phthalimidomethyl groups into disulfonated aluminum phthalocyanine, resulted in increased partition coefficients between n-octanol and water, and a six-fold increase in both cellular uptake and photocytotoxicity towards Chinese hamster lung fibroblast cells (line V-79). Reducing the number of phthalimidomethyl groups, or increasing the degree of sulfonation, lead to a decrease in the partition coefficient, cellular uptake, and phototoxicity. The quantum yield of singlet oxygen was comparable for all dyes tested in this series, indicating that no significant change in this photophysical parameter resulted from phthalimidomethylation. These results suggest that the addition of 1-2 phthalimidomethyl groups to disulfonated aluminum phthalocyanine improves cellular uptake, but, as the relative efficiency of cell killing was not effected, the intracellular distribution on photosensitive molecules may not be modified.

Chlorin and porphyrin derivatives as potential photosensitizers in photodynamic therapy

In order to find a photosensitizer with better optical properties and pharmacokinetics than Photofrin II, a series of new photosensitizers related to methyl pheophorbide-a and chlorin-e6 were synthesized. These compounds absorb at substantially longer wavelengths (lambda max 660 nm) than does Photofrin II (630 nm) and show promise for use in photodynamic therapy. Among the porphyrins, we observed that long carbon chain ether derivatives are better photosensitizers than their ester analogs. These sensitizers were tested for in vivo photosensitizing activity vis-a-vis Photofrin II, using the standard screening system of DBA/2 mice bearing transplanted SMT/F tumors. Most of these photosensitizers were found to have better tumoricidal photosensitizing activity than Photofrin II and demonstrated more rapid attenuation of normal tissue photosensitivity with time after administration vis-a-vis Photofrin II.

Aluminum phthalocyanines with asymmetrical lower sulfonation and with symmetrical higher sulfonation: a comparison of localizing and photosensitizing mechanism in human tumor LOX xenografts

A comparison of time-dependent localization patterns between lower, asymmetrical (AIPCS2a) and higher, symmetrical (AIPCS4) sulfonates of aluminum phthalocyanines in human malignant melanoma LOX transplanted to athymic nude mice from 1 to 120 hr after i.v. administration was made by means of laser scanning fluorescence microscopy. The lipophilic AIPCS2a was distributed mainly in tumor cells, while the hydrophilic AIPCS4 localized only in the vascular stroma of the tumor tissue. Concomitantly, comparative observations on the killing mechanism of photodynamic effects after treatment with a much lower i.v. dose of AIPCS2a and AIPCS4 plus laser light on the human tumor LOX were also made by morphological studies. Light and electron microscopy showed that there was a direct, extensive, photo-damaging action on all organelles and nuclear structure in the tumor cells after PDT with AIPCS2a; whereas the photo-induced injury to the tumor tissue after treatment with AIPCS4 and light was largely the consequence of initial functional vasogenic response and ultimate damage to vascular structure. These findings correlate well with the different localization patterns of the 2 dyes observed in human tumor tissues.

Localization of fluorescent Photofrin II and aluminum phthalocyanine tetrasulfonate in transplanted human malignant tumor LOX and normal tissues of nude mice using highly light-sensitive video intensification microscopy

A comparative kinetic observation of the in vivo biolocalization of Photofrin II (P-II) and aluminum phthalocyanine tetrasulfonate (AIPCS4) in a transplanted human malignant tumor LOX and in normal tissues of nude mice has been made by means of highly light-sensitive video intensification microscopy at various intervals after i.p. administration. In the human tumor LOX, transplanted to athymic nude mice, fluorescence of P-II was observed on the membrane and in the cytoplasm of tumor cells, and in the stroma 4-48 hr post-injection. From 72 hr post-injection almost all fluorescing P-II had disappeared from the membrane of the tumor cells while strong fluorescence was still found in the stroma. AIPCS4 fluorescence was seen mainly in tumorous stroma with none detected in the tumor cells. Almost no fluorescence was found in the tumorous stroma 24 hr after injection. In most normal tissues observed, P-II was eliminated at a much slower rate than AIPCS4, but the in vivo biolocalization of the 2 drugs was similar. They were observed primarily where collagenous proteins are normally found, i.e. basal lamina, collagenous connective tissue, and in keratinized epithelium, renal epithelium, mononuclear phagocyte system and on the membrane of muscular cells. In addition, AIPCS4 had a strong affinity for the bronchiogenic epithelium. In the skin, P-II was distributed in keratinized epithelium, hair, hair follicles and their accessory, collagenous connective tissue of dermis, whereas AIPCS4 was present only in hair and collagenous connective tissue of dermis. No fluorescence of P-II or of AIPCS4 was found in the skin epidermis, nor in the transitional epithelium of the bladder mucosa.

Mixed acenannellated metallotetraazaporphins: a new class of amphiphilic photosensitizers for the photodynamic therapy of cancer

The first synthesis of amphiphilic mixed acenannellated metallotetraazaporphins compounds, designed with the aim of improving cell membrane penetration, is described and the preliminary results on their photocytotoxicity are presented.

Biological activities of phthalocyanines--XI. Phototoxicity of sulfonated aluminum naphthalocyanines towards V-79 Chinese hamster cells

The phototoxicity of sulfonated aluminum naphthalocyanines towards V-79 Chinese hamster cells is investigated. The disulfonated naphthalocyanine exhibits similar photostability, but better cell penetrating properties than the tetrasulfonated dyes. The capacity of the naphthalocyanines to generate singlet oxygen is comparable to that of the corresponding phthalocyanines. However, in contrast to the phthalocyanine dyes, the sulfonated aluminum naphthalocyanines show very little phototoxicity towards the V-79 cells, suggesting close association with non-vital cell constituents or extensive formation of photoinactive adducts and aggregates.

Effect of photodynamic therapy on anti-tumor immune defenses: comparison of the photosensitizers hematoporphyrin derivative and chloro-aluminum sulfonated phthalocyanine

The effects of the two photosensitizers chloroaluminum sulfonated phthalocyanine (ClAlSPc) and hematoporphyrin derivative (HpD) on the functional activities of macrophages and natural killer (NK) cells, two immunocyte populations implicated in the control of tumor development and spread, have been investigated. Murine peritoneal macrophages treated in vivo with ClAlSPc or HpD at 10 mg/kg body weight showed no impairment of Fc-mediated phagocytic capacity and only minor disturbances of in vitro tumoricidal/tumoristatic function. The NK cell activity of splenocytes obtained from photosensitizer-treated mice, assayed 24 or 48 h after i.v. injection of ClAlSPc or HpD at 10 mg/kg was unaffected compared to controls. However significant inhibition of NK activity was observed when splenocytes obtained from mice with or without subcutaneous Colo 26 tumors, treated with ClAlSPc plus laser therapy (675 nm) were used as effector cells. The results show that impairment of some anti-tumor activity can be observed in phthalocyanine treated or phthalocyanine + laser-treated animals but this relatively minor impairment may augur well for the use of systemic phthalocyanine administration in photodynamic therapy.

Specific targeting and toxicity of sulphonated aluminium phthalocyanine photosensitised liposomes directed to cells by monoclonal antibody in vitro

A partially purified fraction of the water soluble photosensitive dye sulphonated aluminium phthalocyanine (AlSPc) was encapsulated in liposomes which were then linked to a targeting monoclonal antibody 791T/36 using a heterobifunctional linking agent. The photocytotoxic effects of the liposomes were determined on two cell lines bearing an antigen with which the targeting antibody binds: 791T, an osteosarcoma and C170, a colorectal carcinoma; and a control cell line not bearing the antigen; DW-BCL, an Epstein-Barr virus immortalised B-cell line. Antibody dependent cytotoxicity was observed in 791T and C170 cells and was proportional to the number of antigens on the cells, the AlSPc concentration and the time of exposure to activating red light. No significant toxicity was seen using untargeted liposomes, control cells or free AlSPc fraction under similar conditions. Targeted cells and controls kept in the dark also showed no significant toxicity. A possible mechanism of action is postulated and simple adaptations which demonstrate the versatility of the model are discussed. Some suggestions as to the clinical situations to which this system might be applied in the form of photodynamic therapy (PDT) are made.

Effect of tumour location on selective uptake and retention of phthalocyanines

The effect of anatomical site of tumour growth on selective uptake and retention of chloro-aluminium sulphonated phthalocyanine (ClAlSPc) was determined using the murine colorectal carcinoma (Colo 26). Tumours were established in the liver, spleen, kidney, lung, thoracic cavity and s.c. flank region of syngeneic BALB/c mice and animals received 10 mg/kg ClAlSPc by i.v. injection. Colo 26 growths at s.c., intra-pulmonary, intra-thoracic or intra-renal sites took up and retained greater amounts of ClAlSPc than did adjacent normal tissues. Such selective retention of ClAlSPc by neoplastic tissue was not observed when Colo 26 was grown in the spleen, where tumour and normal tissue took up about the same amounts, or the liver, where normal tissue took up more ClAlSPc than either directly implanted or metastatic tumours. ClAlSPc ratios found in tumour/adjacent tissue may vary for a single tumour growing at different anatomical sites and such variability could have a distinct effect on the efficacy of photodynamic therapy of cancer.

Evaluation of sulfonated aluminum phthalocyanines for use in photochemotherapy. Cellular uptake studies

Cellular uptake of aluminum phthalocyanine sulfonated to different degree was studied by means of fluorescence measurements and HPLC chromatography. These results were correlated to the lipophilic property of each drug measured as the distribution of the drug between a lipophilic phase (Triton X-114) and an aqueous phase. All the sulfonated aluminum phthalocyanines were taken up into cells to a higher extent than porphyrins of a similar lipophilicity. The cellular uptake of monosulfonated aluminum phthalocyanine was 10-fold higher than the cellular uptake of tetrasulfonated aluminum phthalocyanine and at least 50% higher than tetra(3-hydroxy-phenyl)porphin which is so far the porphyrin shown to be taken up into cells to the highest extent.

Recovery of Chinese hamster cells following photosensitization by zinc tetrahydroxyphthalocyanine

The phthalocyanine dyes are attractive sensitizers for photodynamic therapy of cancer. The light fluence response curves for photocytotoxicity of zinc tetrahydroxyphthalocyanine were constructed using the colony-forming ability of Chinese hamster cells as an end-point. The survival curve of cells photosensitized to white light by this dye has a pronounced shoulder followed by an exponential decline. Postillumination hypertonic treatment (0.5 M NaCl for 20 min at 37 degrees C) enhanced log-phase killing, although to a lesser extent than after exposure to ionizing radiation. While such an enhancement usually indicates that the cells are able to repair potentially lethal damage, delayed trypsinization of photosensitized cells in plateau-phase failed to show a significant increase in cell survival. Thus, the repair of such a damage in plateau-phase is apparently absent. Experiments with split light fluence indicated that log-phase cells can repair sublethal damage during a 24 h interval, as evidenced by the reappearance of the shoulder on the split-dose survival curve.

Combined action of phthalocyanine photosensitization and gamma-radiation on mammalian cells

The response of Chinese hamster cells and human lymphocytes to the combined action of photosensitization by chloroaluminium phthalocyanine tetrasulfonate and gamma-radiation was studied using colony-forming ability and [3H]thymidine incorporation following mitogenic stimulation respectively, as endpoints. The action of both treatments was usually additive regardless of the sequence of application. However, in human lymphocytes irradiated at low temperature, the photosensitization interacted synergistically with the subsequent ionizing radiation; in this experiment the initial photosensitization reduced the yield of micronuclei produced by gamma-radiation.