A test of different photosensitizers for photodynamic treatment of cancer in a murine tumor model

Hyaluronan-decorated polymer nanoparticles targeting the CD44 receptor for the combined photo/chemo-therapy of cancer

In the attempt to develop novel concepts in designing targeted nanoparticles for combination therapy of cancer, we propose here CD44-targeted hyaluronan-decorated double-coated nanoparticles (dcNPs) delivering the lipophilic chemotherapeutic docetaxel (DTX) and an anionic porphyrin (TPPS₄). dcNPs are based on electrostatic interactions between a negative DTX-loaded nanoscaffold of poly(lactide-co-glycolide), a polycationic shell of polyethyleneimine entangling negatively-charged TPPS₄ and finally decorated with hyaluronan (HA) to promote internalization through CD44 receptor-mediated endocytosis. DTX/TPPS₄-dcNPs, prepared through layer-by-layer deposition, showed a hydrodynamic diameter of around 180 nm, negative zeta potential and efficient loading of both DTX and TPPS₄. DTX/TPPS₄-dcNPs were freeze-dried with trehalose giving a powder that could be easily dispersed in different media. Excellent stability of dcNPs in specific salt- and protein-containing media was found. Spectroscopic behavior of DTX/TPPS₄-dcNPs demonstrated a face-to-face arrangement of the TPPS₄ units in non-photoresponsive H-type aggregates accounting for an extensive aggregation of the porphyrin embedded in the shell. Experiments in MDA-MB-231 cells overexpressing the CD44 receptor demonstrated a 9.4-fold increase in the intracellular level of TPPS₄ delivered from dcNPs as compared to free TPPS₄. Light-induced death increased tremendously in cells that had been treated with a combination of TPPS₄ and DTX delivered through dcNPs as compared with free drugs, presumably due to efficient uptake and co-localization inside the cells. In perspective, the strategy proposed here to target synergistic drug combinations through HA-decorated nanoparticles seems very attractive to improve the specificity and efficacy of cancer treatment.

Sonodynamic antitumour effect of chloroaluminum phthalocyanine tetrasulfonate on murine solid tumour

The sonodynamically induced antitumour effect of chloroaluminum phthalocyanine tetrasulfonate (AlPcTS) was evaluated on subcutaneously implanted colon 26 carcinoma. A time of 24h after the administration of AlPcTS was chosen for the ultrasonic exposure, based on the analysis of the AlPcTS concentrations in the tumour, plasma, skin and muscle. The pharmacokinetic analysis showed much faster clearance of AlPcTS than photofrin II from the body, which can be an advantage in view of their potential adverse effects. At an AlPcTS dose not less than 2.5 mg kg−1 and at a free-field ultrasonic intensity not less than 3 W cm−2, the synergistic effect between AlPcTS administration and ultrasonic exposure on the tumour growth inhibition was significant. The ultrasonic intensity showed a relatively sharp threshold for the synergistic antitumour effect, which is typical for an ultrasonic effect mediated by acoustic cavitation. These results suggest that AlPcTS is a potential sonosensitizer for sonodynamic treatment of solid tumours.

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.

Photodynamic activity of lutetium-texaphyrin in a mouse tumor system

BACKGROUND AND OBJECTIVE

New photosensitizers proposed for photodynamic therapy (PDT) treatment of tumors need to be evaluated in animal models to determine the parameters needed for treatment. They also need to be compared with existing photosensitizers for efficacy. We examined the PDT response to lutetium-texaphyrin (PCI-0123) in a mouse mammary adenocarcinoma model and compared it with the PDT response seen when using Photofrin.

STUDY DESIGN/MATERIALS AND METHODS

DBA/2 mice with SMT-F tumors were used to explore PCI-0123 toxicity, laser light dose, and drug dose effects on PDT response and to determine the most effective time for light application. The PDT response of PCI-0123-treated tumors was compared with that of Photofrin-treated tumors.

RESULTS

Treatment of tumors with 150 J/cm2 of 740 nm laser light 5-6 hr after PCI-0123 administration (40 mg/kg) resulted in a 100% response rate and a 55% cure rate. Tumors treated with 150 J/cm2 of 630 nm laser light 24 hr after Photofrin administration (10 mg/kg) resulted in a 67% response rate and a 16% cure rate.

CONCLUSION

PCI-0123 was found to be a more effective photosensitizer than Photofrin.

Photodynamic parameters in the chick chorioallantoic membrane (CAM) bioassay for topically applied photosensitizers

The relative efficacy of Photofrin-based photodynamic therapy (PDT) has been compared with that of the second-generation photosensitizers 5-aminolevulinic acid (ALA), sulfonated chloro-aluminum phthalocyanine (AlPcSn), benzoporphyrin derivative monoacid ring A (BPD-MA), and lutetium texaphyrin (Lutex). PDT-induced vascular damage in the chick chorioallantoic membrane (CAM) is measured following topical application of the photosensitizers. In order to make meaningful comparisons, care is taken to keep treatment variables the same. These include light dose (5 and 10 J/cm2), power density (33 and 100 mW/cm2), and drug uptake time (30 and 90 min). The drug dose ranges from 0.1 microgram/cm2 for BPD to 5000 micrograms/cm2 for ALA. Results are also analyzed statistically according to CAM vessel type (arterioles versus venules), vessel diameter, and vessel development (embryonic age). For each photosensitizer, the order of importance for the various PDT parameters is found to be unique. The differences between the sensitizers are most likely due to variation in biophysical and biochemical characteristics, biodistribution, and uptake kinetics.

Photodynamic efficacy of naturally occurring porphyrins in endothelial cells in vitro and microvasculature in vivo

Photodynamic therapy (PDT) has been described in terms of cellular and vascular effects. The precise mechanisms of cellular and vascular damage are still unknown. In this study, the photodynamic inactivation of endothelial cells in vitro and damage to the microvasculature in vivo by naturally occurring porphyrins (uroporphyrin III (UP), coproporphyrin III (CP) and protoporphyrin IX (PP)) were investigated. The chick chorioallantoic membrane model (CAM model) was used, which is convenient for the study of damage to the microcirculation induced by PDT. The hydrophilic porphyrins UP and CP exhibited low cytotoxicity towards endothelial cells. Only small amounts of UP and CP were taken up, resulting in weak inactivation after irradiation. In contrast, the more lipophilic PP showed a marked cytotoxicity. Considerable amounts of PP were accumulated in the cells, leading to pronounced inactivation after light exposure. For the three porphyrins, damage to the microvasculature was observed. The damage caused by the hydrophilic porphyrins UP and CP was strongly dependent on the drug and light dose. For vascular injury, the efficacy was graded as UP < CP < PP.

In vivo photodynamic therapy with the new near-IR absorbing water soluble photosensitizer lutetium texaphyrin and a high intensity pulsed light delivery system

An in vivo fluorescence monitoring and photodynamic therapy (PDT) study was performed using the new photosensitizer lutetium texaphyrin (Lu-Tex). This photosensitizer is water soluble and has the additional advantage of strong absorption near 730 nm. C26 colon carcinoma was transplanted in the foot of BALB/c mice. In vivo fluorescence spectroscopy was applied to study Lu-Tex tissue distribution kinetics. For this purpose, fluorescence intensity both in the foot with the tumor and in the normal foot was measured in vivo by the laser-induced fluorescence (LIF) system. For PDT, both feet of the mice were irradiated simultaneously with the use of a new high intensity pulsed light delivery system, the Photodyne. The results of the LIF measurements showed that the maximal fluorescence intensity ratio between the normal and tumor bearing foot (FIR) was observed 24-48 h after the agent injection. Photoirradiation with doses from 90 to 240 J cm-2 (0.6 J cm-2 per 2 ms pulse, 1 Hz) 24 h after injection of Lu-Tex at a dose of 10 mg kg-1 caused significant tumor necrosis and delay in the tumor growth rate. The antitumor effect was enhanced with increasing light doses. Normal tissue response to PDT with Lu-Tex was determined as the damage index of the normal foot, which was irradiated simultaneously with the tumor bearing foot. The normal tissue response after PDT with Lu-Tex was compared with 5-aminolevulinic acid (ALA) induced protoporphyrin IX (PP), chlorin e6 (Chl) and Photofrin (PII) at the same values of antitumor effect. The results showed that at 50, 80 and 100% inhibition of tumor growth the orders of the values of normal foot damage indexes were as follows: ALA > Lu-Tex > or = PII > Chl, PII > ALA > Lu-Tex > Chl and PII > Lu-Tex > ALA > Chl respectively.

Enhanced antitumour effect of photodynamic therapy by microtubule inhibitors

The combination of photodynamic therapy (PDT) and the microtubule (MT) inhibitor, vincristine (VCR) or taxol, was studied in the CaD2 mammary tumour model in mice. Meso-tetra(di-adjacent-sulphonatophenyl) porphine (TPPS2a) was used as a photosensitizer. An enhanced antitumour effect was found when VCR, at an almost non-toxic dose (1 mg/kg1, was injected i.p. into the mice 6 h before PDT, while no such enhanced effect was observed when the same dose of VCR was given either 12 or 24 h before PDT or immediately before PDT. Furthermore, it was found that the number of mitotic cells increased 4-5-fold 6 h after the injection of VCR into the mice. VCR did not enhance the sensitivity of normal skin to PDT. Combination of PDT and taxol was also studied. The antitumour activity of PDT could be increased by taxol when the drug (35 mg/kg) was administered i.p. either 6 h prior to PDT or immediately after or before PDT. No significant enhancement in PDT efficiency was found when PDT with photofrin was combined with VCR.

Measurement of tumor vascular damage in mice with 99mTc-MIBI following photodynamic therapy

The clinical perfusion agent 99mTc-MIBI was used to monitor changes in tumor vascular perfusion (TVP) induced by Photofrin (PII)-mediated photodynamic therapy (PDT). BALB/c mice bearing an EMT-6 tumor on each hind thigh were given an intravenous injection of 1, 2 or 5 mg kg-1 PII. Twenty-four hours later, one tumor was illuminated (600-650 nm, 200 mW cm-2, 400 J cm-2) while the other served as a control. At various time intervals after PDT (0, 2 and 24 h) mice received an intravenous injection of 99mTc-hexakismethoxyisobutylisonitrile (MIBI) (0.18 MBq g-1) and were sacrificed 2 min later. The light-treated and the untreated tumors were then dissected, the radioactivity was counted and the percentage of the injected dose per gram of tumor (%ID g-1) was calculated as a measure of TVP. We observed that TVP is drug dose dependent, develops progressively with time post-PDT and is inversely related to PDT efficacy. Our data show that early tumor retention of 99mTc-MIBI is a simple method to assess TVP and vascular damage induced by PDT.

A comparative study of tissue distribution and photodynamic therapy selectivity of chlorin e6, Photofrin II and ALA-induced protoporphyrin IX in a colon carcinoma model

An in vivo study of tissue distribution kinetics and photodynamic therapy (PDT) using 5-aminolaevulinic acid (ALA), chlorin e6 (Chl) and Photofrin (PII) was performed to evaluate the selectivity of porphyrin accumulation and tissue damage effects in a tumour model compared with normal tissue. C26 colon carcinoma of mice transplanted to the foot was used as a model for selectivity assessment. Fluorescence measurements of porphyrin accumulation in the foot bearing the tumour and in the normal foot were performed by the laser-induced fluorescence (LIF) system. A new high-intensity pulsed light delivery system (HIPLS) was used for simultaneous irradiation of both feet by light in the range of 600-800 nm, with light doses from 120 to 300 J cm-2 (0.6 J cm-2 per pulse, 1 Hz). Photoirradiation was carried out 1 h after injection of ALA, 3 h after injection of Chl and 24 h after injection of PII. A ratio of porphyrin accumulation in tumour vs normal tissue was used as an index of accumulation selectivity for each agent. PDT selectivity was determined from the regression analysis of normal and tumour tissue responses to PDT as a function of the applied light dose. A normal tissue damage index was defined at various values (50, 80 and 100%) of antitumour effect. The results of the LIF measurements revealed different patterns of fluorescence intensity in tumour and normal tissues for ALA-induced protoporphyrin IX (ALA-PpIX), Chl and PII. The results of PDT demonstrated the differences in both anti-tumour efficiency and normal tissue damage for the agents used. The selectivity of porphyrin accumulation in the tumour at the time of photoirradiation, as obtained by the LIF measurements, was in the order ALA-PpIX > Chl > PII. PDT selectivity at an equal value of anti-tumour effect was in the order Chl > ALA-PpIX > PII. Histological examination revealed certain differences in structural changes of normal skin after PDT with the agents tested. The results of PDT selectivity assessment with respect to differences in mechanisms of action for ALA, Chl and PII are discussed.

Correlation of distribution of sulphonated aluminium phthalocyanines with their photodynamic effect in tumour and skin of mice bearing CaD2 mammary carcinoma

A chemical extraction assay and fluorescence microscopy incorporating a light-sensitive thermoelectrically cooled charge-coupled device (CCD) camera was used to study the kinetics of uptake, retention and localisation of disulphonated aluminium phthalocyanine (A1PcS2) and tetrasulphonated aluminium phthalocyanine (A1PcS4) at different time intervals after an i.p. injection at a dose of 10 mg kg-1 body weight (b.w.) in tumour and surrounding normal skin and muscle of female C3D2/F1 mice bearing CaD2 mammary carcinoma. Moreover, the photodynamic effect on the tumour and normal skin using sulphonated aluminium phthalocyanines (A1PcS1, A1PcS2, A1pcS4) and Photofrin was compared with respect to dye, dye dose and time interval between dye administration and light exposure. The maximal concentrations of A1PcS2 in the tumour tissue were reached 2-24 h after injection of the dye, while the amounts of A1PcS4 peaked 1-2 h after the dye administration. A1PcS2 was simultaneously localised in the interstitium and in the neoplastic cells of the tumour, whereas A1PcS4 appeared to localise only in the stroma of the tumour. The photodynamic efficiency (light was applied 24 h after dye injection at a dose of 10 mg kg-1 b.w.) of the tumours was found to decrease in the following order: A1PcS2 > A1PcS4 > Photofrin > A1PcS1. Furthermore, photodynamic efficacy was strongly dependent upon dye doses and time intervals between dye administration and light exposure: the higher the dose, the higher the photodynamic efficiency. The most efficient photodynamic therapy (PDT) of the tumour was reached (day 20 tumour-free) when light exposure took place 2 h after injection of A1PcS2 (10 mg kg-1). A dual intratumoral localisation pattern of the dye, as found for A1PcS2, seems desirable to obtain a high photodynamic efficiency. The kinetic patterns of uptake, retention and localisation of A1PcS2 and A1PcS4 are roughly correlated with their photodynamic effect on the tumour and normal skin.

Anti-tumour activity of photodynamic therapy in combination with mitomycin C in nude mice with human colon adenocarcinoma

The interaction of photodynamic therapy (PDT) and a chemotherapeutic drug, mitomycin C (MMC), was investigated using WiDr human colon adenocarcinoma tumours implanted on Balb/c athymic nude mice. The WiDr tumours were treated with PDT alone, MMC alone or with both. It was found that the combined treatment produced a greater retardation in the growth of the WiDr tumour than monotherapy with MMC or PDT. The synergistic effect was especially prominent when PDT was used in combination with a low dose of MMC (1 mg kg-1), since treatment of 1 mg kg-1 MMC alone had no effect on the tumour. The anti-tumour activity of PDT was found to be increased with MMC of 5 mg kg-1. The response of normal skin on mice feet to PDT slightly greater when PDT was combined with 5 mg kg-1 MMC than when PDT was applied alone, while no detectable additional effect on skin photosensitivity was observed when PDT was combined with 1 mg kg-1 MMC. An enhanced uptake of Photofrin in tumours was found 12 h and 24 h after administration of MMC. The effect of MMC on the cell cycle distribution of cell dissociated directly from the tumours was studied. The results suggest that the increased susceptibility to photoinactivation of Photofrin-sensitised tumours may be due to MMC-induced accumulation of the tumour cells in S-phase.

Intracellular fluorescence behaviour of meso-tetra(4-sulphonatophenyl)porphyrin during photodynamic treatment at various growth phases of cultured cells

Meso-tetra(4-sulphonatophenyl)porphyrin (TPPS4) taken up by cells is mainly localized in lysosomes as previously shown by fluorescence microscopical and fluorescence spectroscopical investigations. In the present study the intracellular fluorescence behaviour and the intracellular amount of this dye at various growth periods of cells were examined. For cells irradiated in the growth phase a relocalization of TPPS4 from the lysosomes into the cytoplasm and finally into the nucleus was observed. In contrast, for cells irradiated in the stationary phase no redistribution could be detected and therefore no evidence for severe damage of the lysosomal membranes and subsequently for the release of lytical enzymes is given. In both cases lethal damage of the cells was achieved as examined using the trypan blue exclusion test. This indicates that damage of the lysosomes is less important in the photodynamic inactivation of cells sensitized by TPPS4.

Lasers in ophthalmology

This article reviews the principle uses of ophthalmic lasers, providing historical background with an emphasis on new applications and areas of investigation. Ophthalmic photocoagulation was the first medical laser application and has restored or maintained vision in millions of people. More recently, photodisruption and, increasingly, ablation have gained prominence for treating a wide range of ocular pathology. The unique properties of lasers have also been harnessed for diagnostic purposes, with optical coherence tomography representing a significant improvement over existing imaging methods. Many ophthalmic applications of lasers have been developed, but the field is a dynamic one which continues to evolve along with laser technology itself.

The use of porphyrins and non-ionizing radiation for treatment of cancer

Photodynamic therapy (PDT) is the treatment of malignant lesions with visible light following systemic or local administration of a photosensitizer or its precursor. Initially, hematoporphyrin derivative and a purified component called Photofrin II was used for clinical PDT. Later on interest has focused on new sensitizers with more favourable absorption as regards light transmission in tissues. Twenty years of clinical experience has revealed that PDT is best applied to early stage cancers. The present review discusses the basic components of PDT and its clinical use in treatment of cancer.

On the photodynamic therapy action spectrum of zinc phthalocyanine tetrasulphonic acid in vivo

The photodynamic therapy (PDT) activity of zinc phthalocyanine tetrasulphonic acid in a rodent tumour model was shown to be critically dependent on the wavelength of the excitation laser light over a relatively small wavelength range. Thus the sensitizer showed a doubling of the PDT activity with fibrosarcoma LSBD1 in BDIX rats when the wavelength of the illuminant was displaced from 680 to 692 nm. Under these conditions, the sensitizer is approximately three times more effective than polyhaematoporphyrin, whereas previously it has been considered to be of low PDT activity. This wavelength effect is attributed to a red shift of the absorption spectrum of the sensitizer in cells compared with that in solution. Fluorescence excitation studies with sensitizer absorbed in mouse 3T3 fibroblast cells are consistent with such a red shift.

Pressure against the tumor can reduce the efficiency of photochemotherapy

C3D2/F1 mice with mammary carcinoma tumors growing subcutaneously on their right foot were given 10 mg/kg aluminium phthalocyanine tetrasulfonate (AlPcS4) by intraperitoneal injection. Twenty-four hours later these tumors were exposed to light at 680 nm. The size of the tumors was measured daily. An exposure of 135 J/cm2 (150 mW/cm2) reduced the tumor growth rate so that the time needed for the tumors to reach a volume five times larger than that at the time of exposure increased from 4 days for control tumors to 15 days. However, when a glass plate was gently pressed against the tumor surface during irradiation, the effect of an identical exposure was significantly smaller. In agreement with this, microscopic studies showed that tumors exposed to laser light without any pressure applied during irradiation were more damaged than tumors receiving a slight pressure. Thus, pressure against the tumor can obviously reduce the oxygen concentration in this tumor enough to reduce the efficiency of the treatment.

Phthalocyanine photodynamic therapy: new strategy for closure of choroidal neovascularization

Chloro-aluminum sulfonated phthalocyanine (CASPc) is a photo-chemically active dye employed in photodynamic therapy (PDT). CASPc is a potent generator of singlet oxygen when irradiated with 675 nm light and is also capable of fluorescence, allowing visualization of the dye in tissues. We devised an angiography system using CASPc fluorescence to determine its localization in experimental choroidal neovascularization in monkeys and then investigated the ability of CASPc to produce photochemical closure of neovascularization upon irradiation with 675nm laser light. Fluorescent imaging indicated that CASPc localized angiographically in areas of neovascularization for at least 24 hours. Irradiation with 675 nm laser light 5-30 minutes after CASPc injection produced complete closure of choroidal neovascularization with minimal damage to overlying retina. We conclude that CASPc localizes in neovascular choroidal vessels and that CASPc photodynamic therapy can produce closure of these choroidal vessels.

Retinal and choroidal vessel closure using phthalocyanine photodynamic therapy

Chloro-aluminum sulfonated phthalocyanine (CASPc) is a photoactive dye capable of generating photochemical reactions when excited with 675 nm light. We used CASPc to produce photochemical closure of retinal medullary ray vessels and choroidal vessels in normal rabbits. Irradiation prior to CASPc injection produced no photographic, angiographic, or histologic lesions in any eyes. Identical irradiation of medullary ray and choroidal vessels after CASPc injection produced complete vessel closure in all eyes. Histopathologic examination showed marked thrombosis of medullary ray and choroidal vessels, with minimal damage to contiguous tissues including the neurosensory retina. We conclude that CASPc can produce profound closure of normal retinal and choroidal vessels with minimal deleterious effect on surrounding tissues.

Pharmacokinetic and tumour-photosensitizing properties of the cationic porphyrin meso-tetra(4N-methylpyridyl)porphine

The pharmacokinetic behaviour and the photodynamic properties of the cationic porphyrin meso-tetra(4N-methylpyridyl)porphine (T4MPyP 2.1 mg/kg) were examined in Balb/c mice bearing an MS-2 fibrosarcoma. The porphyrin shows good tumour localizing properties; 24 h after drug administration the tumour concentration of T4MPyP was approximately 1.2 ng/mg, while the concentrations in normal tissues were substantially lower, except for liver and spleen. In the serum, T4MPyP is preferentially transported by albumin and globulins (80.5%), while minor amounts are associated to lipoproteins (19.5%). The phototherapeutic efficiency of T4MPyP was tested by following the growth curves of fibrosarcoma irradiated by 600-680 nm (450 J/cm2) 24 h after the i.v. injection of T4MPyP (2.1 mg/kg). PDT-treated tumours showed a temporary delay in their growth compared with control tumours. The excellent selectivity of T4MPyP and its antitumour activity on photoexcitation encourage further studies for assessing the usefulness of this porphyrin in photodynamic therapy.

Biodistribution of a methylene blue derivative in tumor and normal tissues of rats

By using a chemical extraction procedure and confocal laser scanning fluorescence microscopy we have investigated the kinetic patterns of uptake and biolocalization of a methylene blue derivative (MBD) in tumors and various normal tissues of Wistar rats bearing fibrosarcoma (Leeds ovarian tumor) after intravenous injection of MBD (10 mg kg-1 body weight). Similar kinetics of accumulation and elimination of MBD fluorescence were found in tumor tissue and surrounding normal skin and muscle tissues. However, the tumor:skin and tumor:muscle ratios of the MBD fluorescence intensity were found to be 9 and 4, respectively, 4 h after intravenous injection, indicating selective uptake of MBD by the tumor tissue. MBD was localized on the walls of all the vessels and extensively in the area of neoplastic cellular and tumorigenic fibrous components in the tumor tissue. Interestingly, no MBD fluorescence could be detected in the metastatic neoplastic cells in the remote lymph nodes. In the skin, MBD was mainly distributed in the keratinized epithelium of the epidermis, hair follicles and their accessories, while little was found both in the epidermis and dermis. In most other tissues, the maximal fluorescence intensity of MBD was found 1-4 h after injection, after which it decreased dramatically to almost undetectable levels 120 h postinjection. Strong fluorescence of MBD was seen in the tracheal mucosal epithelium, while little fluorescence was noted in the transitional epithelium of bladder. The kinetics of biolocalization of MBD in some other tissues (liver, spleen, kidney, brain, muscle, lung, heart) were also studied.

Liposomal delivery of a photosensitizer, benzoporphyrin derivative monoacid ring A (BPD), to tumor tissue in a mouse tumor model

Biodistribution studies were carried out on 14C-labeled benzoporphyrin derivative monoacid ring A (BPD), which had been formulated as a unilamellar liposome or taken from a stock solution in dimethyl sulfoxide diluted into phosphate-buffered saline immediately before intravenous injection into DBA/2 mice. By and large the general distribution of BPD to various organs and tissues was comparable for both formulations. It was noted, however, that liposomal material appeared to enter tissues more rapidly and to be cleared more rapidly, as demonstrated by shorter half-lives for a number of tissues including skin, lung and fat, and generally lower levels in most tissues 24 h following administration. Accumulation in tumor tissue was slightly higher with liposomal BPD, and clearance rates for this tissue were equivalent (half-lives 16.1 h for liposomal BPD and 16.9 h for aqueous BPD). When the two preparations were tested in a bioassay in tumor-bearing mice, photodynamic therapy (PDT) with liposomal BPD proved to be superior to the aqueous preparation when PDT was administered 3 h following intravenous administration of BPD. Plasma distribution studies in vitro demonstrated that 91.1 +/- 0.3% of the liposomal BPD distributed to the lipoprotein fraction within the first hour of mixing, whereas only 49.1 +/- 2.6% of nonliposomal BPD was associated with lipoprotein under the same conditions. Furthermore, while lipoprotein-associated liposomal BPD distributed evenly between all three types of lipoprotein (high, low and very low density), a majority of nonliposomal BPD associated with the high-density lipoprotein fraction.

Distribution and photosensitizing efficiency of porphyrins induced by application of exogenous 5-aminolevulinic acid in mice bearing mammary carcinoma

By means of a chemical extraction procedure and confocal laser scanning microscopy, we investigated the kinetic patterns of uptake and biolocalization of 5-aminolevulinic acid (ALA)-induced porphyrins in s.c. transplanted tumors, adjacent normal skin and muscle, and liver of mice bearing mammary carcinoma, after i.p. injection of 250 mg/kg ALA or topical application of ALA (20% in an oil-in-water emulsion). Furthermore, we evaluated the tumor responses after either i.p. injection or topical application of 5-ALA followed by laser irradiation (632 nm, 150 mW/cm2, 25 min) by measuring the treated tumor regression/regrowth time and by light and electron microscopy. Strong fluorescence of ALA-induced porphyrins was detected in the tumor, skin and liver tissues, while little fluorescence was seen in the adjacent muscle tissue. Moreover, the highest amounts of ALA-induced porphyrins in the tumor and skin tissues were found 1 hr after i.p. injection, whereas the amounts of the porphyrins in both tissues increased with increasing time after topical application of ALA. The fluorescence of the porphyrins was localized in several components of the skin tissue (epidermis, hair follicles and their associated sebaceous glands). Furthermore, the fluorescence was diffusely distributed in the s.c. transplanted tumor tissue. Little could be observed under a confocal laser scan microscope (CLSM) in the muscle tissue. The uptake and biolocalization data correlate well with the results of PCT efficiency of the same tumor model with ALA-induced porphyrins. Light and electron microscopy showed that the mitochondria of the tumor cells and of the endothelial cells and the basal lamina of vascular walls beneath the endothelium in the tumor tissue were initially extensively destroyed after PCT with ALA-induced porphyrins. Thereafter, diffuse degeneration followed by local and/or diffuse severe necrosis of the tumor cells was found. This may be due mainly to the initial damage to mitochondria in the cancerous and endothelial cells and also to the destruction of the vascular wall in the tumor tissue.

Retention and phototoxicity of tetra(4-sulfonatophenyl)porphine in cultivated human cells. The effect of fractionation of light

Human cervix carcinoma cells of the line NHIK 3025 were incubated for 18 h with tetra(4-sulfonatophenyl)porphine (TPPS4) and further incubated for 1-29 h in sensitizer free medium before exposure to light. After 1 h in sensitizer free medium only a 20% further loss of TPPS4 was observed within the next 28 h. During the time in sensitizer free medium, each TPPS4 molecule became more efficient in sensitizing single cells to photoinactivation. This enhanced photosensitizing efficiency of TPPS4 correlated well with the enhanced fluorescence yield of TPPS4. In some experiments the cells were exposed to a light dose inactivating 10% of the cells after incubation for 1 h in sensitizer free medium and a second graded light dose given 4-28 h later. Exposure of the cells to the first light dose led to loss of 60% of TPPS4 from the cells. Despite the significant loss of sensitizer from the cells the fluorescence yield of TPPS4 from each cell was found to increase (e.g. by 100% 4 h after light exposure). The enhanced fluorescence yield of cell bound TPPS4 was followed by a 1.6-2.5-fold increase in sensitivity of each cell to second light dose. Thus, a small light dose increased the photosensitivity of TPPS4-loaded NHIK 3025 cells for several hours after the first light exposure. The advantageous effect of light fractionation was reduced by a significantly enhanced loss of sensitizer induced by the first light exposure. The optimal time between the two fractions of light seems to be 30-90 min.

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.

Fractionated treatment of CaD2 tumors in mice sensitized with aluminium phthlocyanine tetrasulfonate

CaD2 mammary carcinomas transplanted into the feet of mice were treated with tetrasulfonated phthalocyanine (AlPcS4) and laser light at 680 nm. A light dose of 135 J/cm2 was either given as continuous radiation (15 min) or fractionated with 15 s exposure, 15 s darkness, 15 s exposure and so on for 30 min. The CaD2 tumors were found to respond better to a fractionated exposure than to the same energy given in one exposure. The reason for this is assumed to be a relocalization of the dye upon illumination, seen as a rapid decrease in fluorescence. When the laser light was turned off, the fluorescence returned to almost the initial value.

Localization of potent photosensitizers in human tumor LOX by means of laser scanning microscopy

By means of laser scanning fluorescence microscopy the intratumoral localization patterns of several photosensitizers in LOX tumors in nude mice were studied. Lipophilic dyes such as TPPS1 (tetraphenylporphine monosulfonate), TPPS2a (tetraphenylporphine disulfonates with the sulfonate groups on adjacent rings), AlPCS1 (aluminium phthalocyanine monosulfonate) and AlPCS2 (aluminium phthalocyanine disulfonates) localized mainly in tumor cells. The fluorescence intensity of these dyes increased from 4 h to 48 h postinjection and the fluorescence was still observable 120 h postinjection. The more hydrophilic dyes such as TPPS3 (tetraphenylporphine trisulfonates), TPPS4 (tetraphenylporphine tetrasulfonates), and AlPCS4 (aluminium phthalocyanine tetrasulfonates) localized mainly extracellularly in the tumorous stroma. The fluorescence intensity of these dyes decreased from 4 h to 48 h postinjection. 120 h postinjection no significant fluorescence of these dyes could be seen in the tumors. P-II (Photofrin II), 3-THPP [tetra(3-hydroxyphenyl)porphine], TPPS2o (tetraphenylporphine disulfonates with the sulfonate groups on opposite rings) and AlPCS3 (aluminum phthalocyanine trisulfonates) had a combined localization pattern, i.e. a strongly cytoplasmic membrane-localizing pattern and a weakly intracellular distribution pattern, although some fluorescence could be seen in the tumorous stroma. The data are discussed in relation to what is known about the in vivo photosensitizing efficiency of some of the dyes.

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.

Light induced relocalization of sulfonated meso-tetraphenylporphines in NHIK 3025 cells and effects of dose fractionation

Human cervix carcinoma cells of the line NHIK 3025 were incubated for 18 h with sulfonated meso-tetraphenylporphines (TPPSn where n = 1, 2a, 2o or 4) followed by 1 h in sensitizer-free medium and then exposed to light. The fluorescing fraction of TPPS4, TPPS2o and TPPS2a has recently been shown to be located intracellularly in extracellular granules which are intracellularly localized in a similar pattern as acridine orange-stained granules, assumed to be endosomes and lysosomes (Berg, K., A. Western, J. Bommer and J. Moan. Photochem. Photobiol. 52, 481-487). Light exposure induced a relocalization of TPPS4 from its granular pattern to mainly the nuclear area while TPPS2o and TPPS2a relocalized mainly to cytoplasmic areas. After the light-induced relocalization TPPS4 became less efficient in sensitizing photoinactivation of cells as measured per fluorescing cellbound TPPS4 molecules while TPPS2a and TPPS2o became more efficient. These changes were independent of the extracellular concentration of TPPSn applied to the cells, except for cells incubated with 75 micrograms/mL TPPS4. These cells became more sensitive to light after a light exposure inactivating 20% of the cells. This increased photosensitivity seems to be related to a 2-2.5 fold increase in the amount of fluorescing cellbound TPPS4 induced by the first light exposure.

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.

Cellular uptake and relative efficiency in cell inactivation by photoactivated sulfonated meso-tetraphenylporphines

The cellular uptake, relative fluorescence quantum yields and photosensitizing efficiencies of meso-tetraphenylporphines sulfonated to different degrees (TPPSn) have been investigated using the human carcinoma cell line NHIK 3025. The efficiencies of these dyes in photoinactivation of cells were highly dependent on the number of sulfonate groups on the derivatives. These differences in phototoxicity were primarily due to different abilities to be taken up by cells, but were also dependent upon the cellular localization of the dyes. TPPS1 and TPPS2a were more efficiently taken up by the cells than TPPS2o and TPPS4. Plasma membrane associated TPPS4 was less efficient in cell inactivation per quantum of fluorescence emitted than intracellularly located dye. This was also to some extent the case for TPPS1 but not for TPPS2a and TPPS2o. The results presented here indicate that TPPS2a and TPPS1 are the most promising of the TPPSns for possible future use in photodynamic therapy.

In vitro evaluation of phototoxic properties of four structurally related benzoporphyrin derivatives

Four structural analogs of benzoporphyrin derivative (BPD) have been studied and compared for photosensitizing activity in vitro. All analogs have an identical reduced tetrapyrrol porphyrin ring, and differ by the position of a cyclohexadiene ring (fused at either ring A or ring B of the porphyrin) and the presence of either two acid groups or one acid and one ester group at rings C and D of the porphyrin. Photosensitizer activity was tested with the M1 tumor cell line using an assay (the MTT assay) which detects mitochondrial hydrogenases as a measure of cell viability. This assay was shown to be equivalent to the standard clonogenicity or [3H]thymidine uptake assay. Comparative studies with the BPD analogs showed that the monoacid derivatives had equivalent cytotoxicity and were about five-fold more active than the diacid forms. This was the case whether the assays were performed in the presence or absence of fetal calf serum.

Intracellular localization of sulfonated meso-tetraphenylporphines in a human carcinoma cell line

The intracellular localization of meso-tetraphenylporphines sulfonated to different degrees (TPPSn), in a human cervix carcinoma cell line (NHIK 3025), was studied by fluorescence microscopy and fluorescence spectroscopy. After an 18 h incubation, TPPS4, TPPS2a and TPPS2o were localized in extranuclear granules. Studies of cells stained with both TPPS4, and acridine orange, which is known to fluoresce red in lysosomes, indicated that these granules were lysosomes. In addition, a fraction of the cellbound TPPS4, TPPS2a and TPPS2o seems to be associated with the plasma membrane. Fluorescence quenching studies of cells doublestained with acridine orange and TPPS4 indicated that TPPS4 is also localized in the nucleus and in the extralysosomal cytoplasm. The intracellular location of TPPS1 differed from that of the other TPPSns studied: In 6 out of 9 experiments fluorescing extranuclear granules were found. A diffuse fluorescence extending from the perinuclear area was also observed.

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.

Phthalocyanine fluorescence in tumors during PDT

Athymic nude mice with human tumors transplanted to one of the hind legs were given aluminium phthalocyanine disulfonate (AlPcS2) intraperitoneally. Twenty-four hours after the injection the mice were placed with the tumor in the sample position in a fluorescence spectrometer with modulated excitation. Exposure of the tumors to laser light at a fluence rate of 50-200 mW/cm2 led to a rapid transient reduction by up to 50% of the phthalocyanine fluorescence of the tumor. After the laser irradiation the fluence rate of the fluorescence increased almost up to the initial value within a few minutes. This finding should be taken into account when optimal fluence rates and dose fractionation schemes are sought for photodynamic therapy.

Hematoporphyrin diethers--V. Plasma protein binding and photosensitizing efficiency

1. Binding of added hematoporphyrin (HP) ethers to human plasma proteins and lipoproteins has been investigated by ultracentrifugation. 2. The binding to low density lipoproteins (LDL) has been discussed in terms of photosensitized tumor growth delay of tumors and HPLC-retention time, i.e. degree of polarity. 3. The LDL-binding data show a uniform relationship to sensitizing efficiency and degree of polarity, the only exception being HP-diamyl ether. No such uniform relationship exists for less related dyes, such as HP, tetraphenylporphyrin tetrasulfonate and HP-dimethyl ether.

Singlet oxygen generation of porphyrins, chlorins, and phthalocyanines

The production of singlet oxygen was measured indirectly for three classes of photosensitizers: porphyrins (Photofrin II, TPPS4), chlorins (MACE, DACE), and a phthalocyanine (CASPc). Buffered solutions of sensitizers and singlet oxygen acceptors were irradiated with a CW dye laser and the oxygen depletion was monitored electrochemically with a Clark-type microelectrode. A comparison of oxygen-depletion rate constants and quantum efficiencies yields the order of efficiency of the sensitizers: TPPS4 greater than MACE greater than PII greater than DACE greater than CASPc. For singlet oxygen acceptors the order was: furfuryl alcohol greater than imidazole greater than tryptophan. CHO cell suspensions were also used as acceptors. Here the order of efficiency (per absorbed photon) was PII greater than MACE approximately CASPc. Expressed in terms of oxygen depletion per cell the order was CASPc approximately PII greater than MACE. When performing cell clonogenicity studies the order of efficiencies, expressed as percentage cell kill per unit weight of sensitizer, was CASPc greater than PII greater than MACE approximately DACE. The discrepancy between the efficiencies of sensitizers to generate singlet oxygen and their cytotoxicity was explained in terms of photodegradation (for the chlorins), intracellular localization (for PII), and contributions from a Type I mechanism (for CASPc).

Photosensitized oxidation of biomaterials and related model compounds

Aluminium trisulfonatophthalocyanine (A1PCS), a dye being widely advocated for use in photodynamic therapy, produces singlet oxygen with a quantum yield of 0.34 in oxygenated water at pH 7. Triplet A1PCS abstracts an electron from a variety of amines and phenols, the rate of electron transfer depending upon the thermodynamic driving force, forming the A1PCS radical anion. This latter species reduces molecular oxygen to superoxide ions with high efficiency. The triplet state also abstracts an electron from biological components, including NADH, vitamin C, cysteine, methionine, tyrosine, tryptophan, uracil, and guanine, but not from DNA. These results suggest that photoinduced electron abstraction from appropriate biomaterials could compete with singlet oxygen production under in vivo conditions.