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.     

BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES—VIII. CELLULAR DISTRIBUTION INV–79 CHINESE HAMSTER CELLS AND PHOTOTOXICITY OF SELECTIVELY SULFONATED ALUMINUM PHTHALOCYANINES

Abstract— Water soluble chloro aluminum phthalocyanines sulfonated to different degrees are studied for phototoxicity and cellular distribution inV–79 Chinese hamster cells. The more hydrophobic disulfonated dyes, with sulfonate substituents on adjacent benzyl groups of the phthalocyanine ring structure, exhibited the best cell penetrating properties and the highest phototoxicity. Fluorescence microscopy revealed that the dye was uniformly distributed in the cytoplasm but absent in the nucleus. The greater cell membrane penetrating properties of the lower as compared to the higher sulfonated dyes are attributed to the amphiphilic nature of the former.     

BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES-IX. PHOTOSENSITIZATION OFV–79 CHINESE HAMSTER CELLS ANDEMT–6 MOUSE MAMMARY TUMOR BY SELECTIVELY SULFONATED ZINC PHTHALOCYANINES

Abstract— Zinc phthalocyanines sulfonated to different degrees are tested for their ability to sensitizeV–79 Chinese hamster cells andEMT–6 mouse mammary tumors to red light. In vitro , the lower sulfonated derivatives were the most active with the exception of the poorly water-soluble monosulfonated dye. An isomeric mixture of tetrasulfonated derivatives obtained via direct sulfonation was ten times more active than the homogeneous tetrasulfo derivative prepared via the condensation of sulfophthalic acid. In vivo , the latter dye was completely inactive, whereas the remainder of the sulfonated preparations exhibited a similar structure-activity pattern as observed with theV–79 cells in vitro . The disulfonated zinc phthalocyanine showed the best tumoricidal activity in the series and also appeared to be a more efficient photosensitizer of cell inactivation and tumor cure than the aluminum or gallium complexes as well as hematoporphyrin derivative preparations. No significant differences in skin phototoxicity were observed among the various dyes.     

Photodynamic properties of naphthosulfobenzoporphyrazines, novel asymmetric, amphiphilic phthalocyanine derivatives.

Metallo naphthosulfobenzoporphyrazines sulfonated to different degrees (M-NSBP) were prepared, and their potential as photosensitizers for the photodynamic therapy (PDT) of cancer was evaluated. M-NSBP can be viewed as hybrid molecules between sulfophthalocyanines and naphthalocyanines resulting in distinct differences in the absorption spectra between the mono-through tetrasulfonated derivatives. This feature greatly facilited their purification. Using V-79 Chinese hamster cells in vitro, the disulfonated derivatives were found slightly more photoactive than the hydrophilic trisulfonated derivatives while the monosulfonated derivative was inactive, in spite of a sixfold higher cell uptake. In the case of the di- and trisulfonated derivatives, differences in phototoxicity correlated well with their relative cell uptake. Substitution of Al for Zn had little effect on the extent of phototoxicity of the M-NSBP. In vitro PDT of the EMT-6 cells after in vivo dye administration, revealed a similar potency for direct cell killing between the di- and trisulfonated AlOH-NSBP, while the monosulfonated analog was inactive. PDT with the amphiphilic disulfonated AlOH-NSBP on the EMT-6 mammary tumor in BALB/c mice induced a significant tumor response, while the monosulfonated derivative was much less active.     

THE PREPARATION OF RADIOLABELED PORPHYRINS and THEIR USE IN STUDIES OF PHOTODYNAMIC THERAPY

Abstract— We tested water-soluble sulfonated phthalocyanine and three metal chelate derivatives for their tumoricidal effect on the EMT-6 mammary tumor in mice exposed to red light. The metal-free sulfophthalocyanine had little effect, whereas the aluminum complex and the lower sulfonated fraction of the gallium complex exhibited tumoricidal activity similar to hematoporphyrin-based photosensitizer (Photofrin II). The higher sulfonated fractions of the gallium complex were less active as compared to the lower sulfonated fraction. The cerium complex was the most active sensitizer in terms of dye and light doses required to induce tumor necrosis and cure but also showed the highest phototoxicity towards healthy skin. These results suggest that sulfonated phthalocyanines will offer a new alternative in photodynamic therapy of light-accessible neoplasms.     

A TEST OF THE SINGLET OXYGEN MECHANISM OF CATIONIC DYE PHOTOSENSITIZATION OF MITOCHONDRIAL DAMAGE

Aromatic cationic dyes have a potential as photo-chemotherapeutic agents because they are selectively concentrated into the mitochondria of cancerous cells. The mechanism of cytophototoxicity has been proposed to be primarily due to dye sensitized photogeneration of highly toxic singlet oxygen (1O2) at the mitochondria. We tested this hypothesis by measuring the relative phototoxicity of a collection of aromatic cationic dyes towards respiring rat-liver mitochondria (RLM), upon addition of 514 nm laser light. Effectiveness of dye photosensitization towards destruction of RLM function was assayed by its effect on the RLM membrane potential. Three physical parameters of dye phototoxicity were independently measured and a relative phototoxicity calculated assuming adherence of mechanism to the 1O2 hypothesis. Quantum yields of dye sensitized 1O2 production were estimated, either from time-resolved luminescence measurements of photosensitized 1O2 formed, or by comparing rates of photobleaching of 1O2 trap; the relative partition of dye into mitochondrial lipid was determined gravimetrically; and the optical density of dye was determined in a lipid like Triton X-100 micellar environment. Under the assumption of the 1O2 hypothesis, these parameters were used to predict a relative phototoxicity which was compared with that observed. For 12 of the 14 dyes investigated, the observed and predicted phototoxicities were linearly correlated (r = 0.85) suggesting support of the 1O2 hypothesis. Carbocyanines DiOC2(3) and DiSC2(3) did not correlate and were found to be 10 and 1000 times more potent than predicted, suggesting an additional factor at play in their phototoxicity.     

CELLULAR UPTAKE AND RELATIVE EFFICIENCY IN CELL INACTIVATION BY PHOTO ACTIVATED 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.     

BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES–VII. PHOTOINACTIVATION OF V-79 CHINESE HAMSTER CELLS BY SELECTIVELY SULFONATED GALLIUM PHTHALOCYANINES

Abstract Gallium chloride phthalocyanines sulfonated to different degrees were tested for their ability to inactivate V-79 Chinese hamster cells in the presence of red light. The mono- and disulfonated compounds were the most active whereas the tri- and tetrasulfonated complexes were completely void of photoactivity. In addition, large variations in photoactivity were observed among the four isomeric disulfonated derivatives with the most hydrophobic isomer exhibiting the highest photoactivity. Prolonged exposure to the disulfonated complex resulted in increased photosensitization. Complexing the dye with Al instead of Ga resulted in a slightly increased photosensitizing effect.     

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

Abstract— Tetrasulfophthalocyanine and a series of its metal chelates were tested for their ability to photoinactivate V-79 Chinese hamster cells. Incubation of cells for 1 h with tetrasulfophthalocyanine at 5 μM effectively sensitized cells towards red light. At the 1% survival level, the dye was 4 x more efficient than hematoporphyrin, efficiency being defined in terms of drug concentration in the medium and incident light fluence rather than on the basis of quanta absorbed. Chelation of the dye with metal ions resulted in most cases in a greatly diminished photosensitizing effect, except for cerium. The cerium complex was about 5 x more effective for cell killing than the metal free tetrasulfophthalocyanine and 20 x more efficient as compared to hematoporphyrin. Hypoxic conditions resulted in total loss of photoactivity indicating the involvement of oxygen in the action mechanism. The inactivation by near-UV light by these drugs was also investigated. The potential of sulfonated phthalocyanines as novel photosensitizers for photodynamic cancer therapy is discussed.     

NOVEL RED ABSORBING BENZO[a]PHENOXAZINIUM and BENZO[a]PHENOTHIAZINIUM PHOTOSENSITIZERS: in vitro EVALUATION

Abstract Taking advantage of the'heavy atom'effect, we have recently prepared a series of nine novel halogenated and sulfur-substituted benzophenoxazines which have enhanced intersystem crossing to the triplet state as measured by singlet oxygen photobleaching of 1,3-diphenylisobenzofuran. The dyes were evaluated for their dark and light-induced toxicities towards several carcinomata and normal primary cell lines. One of these days, 5-amino-6-iodo-9-diethylaminobenzol[a]phenoxazinium chloride, was found to be a potent photosensitizer for a murine sarcoma 180 and four human carcinomata cell lines (larynx Hep2, cervical HeLa, rectal tumor cell HRT, and transitional-cell bladder BTC). Several dyes caused marked light dependent killing of two tumor cell lines (Hep2 and HRT) but were minimally toxic to a normal bovine fetal kidney (BFK) line. Sulfur substitutuion into the benzophenoxazine nucleus results, under the conditions studied, in the largest enhancement of phototoxicity both to normal and cancer cells. Comparisons between appropriate dyes show a correlation between the efficiency of singlet oxygen generation and phototoxicity. These results suggest that the photosensitizing efficacy of certain cationic benzophenoxazinium chromophores, such as Nile Blue A, can be greatly increased by appropriate structural modification. The demonstrated selectivity for carcinoma cells by some of these new photosensitizers may be useful therapeutically.     

A COMPARISON OF DIRECI AND LIPOSOMAL ANTIBODY CONJUGATES OF SULFONATED ALUMINUM PHTHALOCYANINES FOR SELECTIVE PHOTOIMMUNOTHERAPY OF HUMAN BLADDER CARCINOMA

Abstract There is a need to improve the selectivity of photodynamic therapy and for better targeting of tumor cells within specific tumor compartments. Selective in vitro phototoxicity of a human bladder carcinoma cell line 647V has been achieved by targeting sulfonated aluminum phthalocyanines (AlSPc) with monoclonal antibodies. Aluminum tetra-3 sulfonyl chloride phthalocyanine (PC) or rhodamine sulfonyl chloride were directly coupled to antibodies by a sulfonamide linkage and AlSPc or carboxyfluorescein were encapsulated in liposomes of the small unilamellar vesicle type (SUV) bearing antibody. Antibody E7 (IgM subclass), which recognized an antigenic determinant expressed on 647V but was absent on T24 a control human bladder carcinoma cell line, and a control IgM antibody were used. The effects of the two types of conjugate were compared. Immunofluorescence studies on living cells demonstrated specific cell surface localization of conjugates at 4°C and internalization at 37°C. Phototoxicity was measured by 3-(4,5-dimethylthiazol-2–5-diphenyltetrazolium) bromide assay after exposing A1SPc-sensitized cells to red light. Significant AlSPc dose-dependent phototoxicity of the order 4°C < 4°C plus 37°C < 37°C was observed with E7-SUV and E7-PC in the range 1–8 μM AlSPc. At equimolar AlSPc doses absolute toxicity was similar for the two conjugate types, but at equimolar antibody doses, the liposomal conjugate was more effective by up to 13-fold. Addition of urine during illumination decreased toxicity, which was attributed to the presence of protective elements. The results suggest that photosensitizers such as AlSPc could be used for antibody-directed therapy and in particular for selectively damaging tumor cells of the epithelial cell compartment in bladder carcinoma by intrabladder administration. The therapeutic ratio, which takes into account both specific and nonspecific toxicity, was greater for the liposome conjugate than for the direct conjugate indicating their greater suitability for in vivo instillation.     

Structure-Photodynamic Activity Relationships of a Series of 4-Substituted Zinc Phthalocyanines

Abstract— Radioiodinated zinc phthalocyanine including [¹²⁵I]ZnPcI₄ and differently sulfonated [⁶⁵Zn]ZnPcS (ZnPcS₄, ZnPcS₃, ZnPcS₂ and ZnPcS_1.75, a mixture of adjacent di and 25% mono) were prepared in order to study cell uptake and release kinetics in EMT-6 cells. The same compounds were evaluated for their in vitro phototoxicity and the biological parameters were compared to partition coefficients to arrive at quantitative structure-activity relationships (QSAR). At 1 μM in 1% serum, at 37°C, all dyes showed rapid cell uptake during the first hour followed by a slow accumulation phase. After 24 h, the highest cellular concentration was observed with the lipophilic ZnPcI₄, followed by the amphiphilic ZnPcS₂ and ZnPcS_1.75. The hydrophilic ZnPcS₄ and ZnPcS₃ showed lower uptake. Dye release from dyeloaded cells during incubation in dye-free medium could reach up to 60% and was shown to depend mainly on the amount of drug incorporated rather than the type of compound. These results suggest that care should be taken in interpreting dye toxicity data, which involve in vitro cell manipulations in dye-free medium, particularly during in vitro/in vivo protocols. The EMT-6 cell survival after 1 h or 24 h incubation with 1 μM dye in 1% serum followed by exposure to red light was assessed by means of the colorimetric 3-(4,5-dimethylthiazol-2-yl)-diphenyl-tetrazolium bromide (MTT) assay. Photocytotoxicities correlated inversely with the tendencies of the dyes to aggregate. Increased dye uptake by the cells also correlated with their activities, except for the lipophilic ZnPcI₄, which showed the highest cell uptake but little phototoxicity. The QSAR between phototoxicity and the log of the partition coefficients (phosphate-buffered saline and n-octanol) gave a parabola with optimal partition values corresponding to the adjacent sulfonated ZnPcS₂.     

In viva PHOTODYNAMIC EFFECTS OF PHTHALOCYANINES IN A SKIN-FOLD OBSERVATION CHAMBER MODEL: ROLE OF CENTRAL METAL ION AND DEGREE OF SULFONATION

Six sulfonated metallophthalocyanines, chelated with either aluminum or zinc and sulfonated to different degrees, were studied in vivo for their photodynamic activity in a rat skin-fold chamber model. The chamber, located on the back of female WAG/Rij rats, contained a syngeneic mammary carcinoma implanted into a layer of subcutaneous tissue. Twenty-four hours after intravenous administration of 2.5 μmol/kg of one of the dyes, the chambers received a treatment light dose of 600 J/cm² with monochromatic light of 675 nm at a power density of 100 mW/ cm². During light delivery and up to a period of 7 days after treatment, vascular effects of tumor and normal tissue were scored. Tumor cell viability was determined by histology and by reimplantation of the chamber contents into the skin of the same animal, either 2 h after treatment or after the 7 day observation period. Vascular effects of both tumor and subcutaneous tissue were strongest with dyes with the lowest degree of sulfonation and decreased with increasing degree of sulfonation. Tumor regrowth did not occur with aluminum phthalocyanine mono- and disulfonate and with zinc phthalocyanine monosulfonate. With the protocol that was used, complete necrosis without recovery was only observed when reimplantation took place at the end of the 7 day follow-up period. Reimplantation 2 h after treatment always resulted in tumor regrowth. At this interval, the presence of viable tumor cells was confirmed histologically. In general tumor tissue vasculature was more susceptible to photodynamic damage than vasculature of the normal tissue. The effect on the circulation of both tumor and normal tissue increased with decreasing degree of sulfonation. Based on this study, the photodynamic effects using the six sulfonated metallophthalocyanines on the vasculature can be ranked from high to low as: AlPcS₂= ZnPcS₁ > AIPcS₁ > AIPcS₄ > ZnPcS₂ > ZnPcS₄.     

OXYGEN-DEPENDENCE OF NEAR UV (365 NM) LETHALITY AND THE INTERACTION OF NEAR UV AND X-RAYS IN TWO MAMMALIAN CELL LINES

Abstract— The colony-forming ability of Chinese hamster cells (V-79) and HeLa cells has been measured after near-ultraviolet (UV) irradiation, predominantly at 365 nm. To avoid the production of toxic photoproducts, cells were irradiated in an inorganic buffer rather than in tissue culture medium. Under these circumstances near-UV lethality was strongly oxygen-dependent. Both cell lines were approximately 10⁴ times more sensitive to 254 nm irradiation than to 365 nm radiation when irradiated aerobically. Pretreatment with 6 times 10⁵ Jm^-2 365 nm radiation sensitised the HeLa, but not the V-79 cell line to subsequent X-irradiation. Pretreatment of cells with 17 Jm^-2 254 nm radiation, a dose calculated to produce twenty times more pyrimidine dimers than the 365 nm dose, produced only slight sensitisa-tion to X-rays. It is suggested that the sensitisation to X-rays seen in the HeLa cells after 365 nm treatment is not the result of lesions induced in DNA by the near-UV radiation, but may reflect the disruption of DNA-repair systems.     

USE OF CHARGE COUPLED DEVICE CAMERA FOR IMAGING OF INTRACELLULAR PHTHALOCYANINES

A highly sensitive charge-coupled device (CCD) camera, linked to a computerized image processor, has been used to obtain fluorescence images of chloro-aluminum sulfonated phthalocyanine (ClAlSPc), and its mono- to tetra-sulfonated constituents, in cells recovered from the peritoneal cavity of dye-treated mice. Immunofluorescence and cytochemistry showed that cells which preferentially took up ClAlSPc and its sulfonated species were predominantly of the monocyte-macrophage series. While this technique may be of use in determining the nature of those cells capable of taking up light sensitive dyes and, perhaps, the intracellular location of such agents, the possibility that photoinactivation by dye aggregation could reduce the sensitivity of this procedure is discussed.     

A COMPARISON OF THREE PHOTOSENSITIZERS WITH RESPECT TO EFFICIENCY OF CELL IN ACTIVATION, FLUORESCENCE QUANTUM YIELD AND DNA STRAND BREAKS

Intracellular properties of three photosensitizers relevant to photodynamic cancer therapy were compared using cultured human NHIK 3025 cells. When taken up in the cells, the hydrophilic photosensitizer aluminum phthalocyanine tetra sulfonate required about 10 times more quanta of light absorbed per cell to kill 90% of the cells than did the hydrophobic dyes Photofrin II and tetra(3-hydroxyphenyl)porphyrin. In spite of this, the phthalocyanine molecule was the most efficient dye per quantum of excitation light, since the extinction coefficient of the phthalocyanine is more than 10 times higher than that of the two hydrophobic photosensitizers at therapeutic wavelengths. The two hydrophobic dyes had significantly higher fluorescence quantum yields when taken up by cells than when bound to human plasma or human serum albumin, whereas the opposite was true for the hydrophilic phthalocyanine dye--suggesting intracellular aggregation. Finally, the potential genetic toxicities of the drugs in the form of DNA strand breaks were compared. The aluminum phthalocyanine tetra sulfonate photosensitized more DNA strand breaks than did Photofrin II and tetra(3-hydroxyphenyl)porphyrin when compared at the same level of cell survival.     

AN ACTION SPECTRUM FOR CELL KILLING AND PYRIMIDINE DIMER FORMATION IN CHINESE HAMSTER V-79 CELLS

We have determined action spectra for pyrimidine dimer formation and loss of colony-forming ability in Chinese Hamster V-79 cells and have found a very strong correlation between the two. These data are consistent with the notion that damage to DNA is the principle cause of cell death and that the most important type of damage is the pyrimidine dimer. While the shape of the V-79 spectra mimics that of action spectra for bacteria. phage, and purified DNA, V-79 cells are about twice as sensitive to radiation at long wavelengths, relative to the sensitivity at 265 nm. However, if the action spectra are normalized to 297 nm. a wavelength included in the solar spectrum, the two sets of action spectra would coincide at wavelengths relevant to human skin-cancer. Thus an action spectrum based on microorganisms should be adequate for extrapolation to humans in terms of risk due to ozone depleteion.     

ACTION SPECTRA OF PHTHALOCYANINES WITH RESPECT TO PHOTOSENSITIZATION OF CELLS

Human carcinoma cells (NHIK 3025 cells) and Chinese hamster cells (V79 cells) were incubated with AlPcS1, AlPcS2 and AlPcS4, phthalocyanines with different lipophilicity but with similar photochemical properties when in monomeric solutions. The absorption- and fluorescence spectra of the dyes in the cells were recorded as well as their action spectra with respect to sensitizing cells to photoinactivation. These spectra show that under the present conditions AlPcS1 is strongly aggregated in both cell lines; AlPcS2 is aggregated in V79 cells but much less so in NHIK 3025 cells. A main finding is that the shapes of the action spectra are similar to that of the fluorescence excitation spectra, but not to the absorption spectra, indicating that the photosensitizing effects of the dyes are mainly due to their monomeric fraction in the cells. AlPcS2 and AlPcS4 localize intracellularly mainly in lysosomes while AlPcS1 was found to be more diffusely distributed in cells. As measured per quantum of fluorescence emitted, AlPcS1 and AlPcS2 are more efficient sensitizers than AlPcS4. The difference in efficiency between AlPcS2 and AlPcS4 is supposedly due to a different localization pattern on the suborganelle level.     

近红外激光防护染料

以激光防护和隐身材料为需求背景，概述了菁类染料(含多次甲基菁染料、方酸菁和克酮酸菁染料、薁染料)、酞菁类染料(含普通酞菁和萘酞菁)、金属络合物染料、醌型染料、偶氮染料、游离基型染料、芳甲烷型染料、苝类染料等近红外吸? 杖玖系难芯孔纯黾敖埂? $601$ADuetotherequirementofnear-infraredlaserprotectivedyesandlaserstealthmaterials,thisreviewfocusedontheresearchprogressofnear-infraredabsorbingdyes,andsomesuggestionswereputforwardonthefutureresearch.Someofthemostimportanttechnicalrequiremnetsforlaser-protectivedyeswithintheplasticareasfollows:sharpabsorptionbandsatspecificwavelengthscorrespondingtolaseremission,excellentlightfastness,robustthermalandchemicalstability,stabilitytoambientconditions,highopticaldensityandscotopicluminoustransmission,goodsolubilityinplasticandlowtoxicity.Thisreviewpaidattentiontothepropertiessuchasthemaximumabsorptionwavelengthandtheabsorptionintense,attentionhadbeendirectedtowardseighttypesnear-infrareddyes:cyaninedyeswhichincludedpolymethinedyesandsquaryliumorcroconiumdyes,phthalocyaninesandnaphthalocyanines,metalcomplexdyes,quinonedyes,azodyes,radicaldyes,multiphenylmethanedyesandperylenedyes.Otherkindsofnear-infrareddyeswerealsomentioned,suchasaromaticannulenes,planescontainignso-callednonbenzenoidaromaticrings,cycliccross-conjugatedhydrocarbonshavinginsertedp-quiniodring,fluorenyliumdyeswithinorganicanions,donor-acceptorcyclophanes,tetrapyrazinoporphyrazinesandpentaazadentateexpandedporphyrinsetal.Allofthedyesmentionedabovehadsomegoodpropertiesforuseasthenear-infraredlaserprotectivedyesandlaserstealthmaterials,buttherealsoexisteddefectsineverykindofdyes.     

SKIN PHOTOSENSITIVITY AND PHOTODESTRUCTION OF SEVERAL POTENTIAL PHOTODYNAMIC SENSITIZERS

The major side effect associated with porphyrins (Photofrin II) in clinical photodynamic therapy is skin photosensitivity. In order to avoid this deleterious reaction, patients must remain out of the sunlight for approximately 1 month. A possible procedure to reduce the amount of skin photosensitivity is to photodegrade (photobleach) the compound in the skin. In this study, we report a series of experiments describing the photodegradation rates of two photosensitizers currently receiving attention due to their potential for use in PDT (mono L-aspartyl chlorin e6 and chloroaluminum sulfonated phthalocyanine). These compounds are compared to Photofrin II (PfII). Experiments consisted of determining photodegradation rates and efficiencies of the sensitizers in (i) phosphate buffered saline (PBS), (ii) PBS with fetal calf serum (to enhance absorption and simulate cellular binding or deaggregation), (iii) Chinese Hamster Ovary cells, and (iv) Balb/c mice. We performed two standardized skin sensitivity assays using the Hartely albino guinea pig irradiated with a UV blue point lamp and Balb/c mice irradiated with the therapeutic wavelength of each sensitizer. In addition, we performed a cell clonogenicity assay comparing photodegraded and fresh PfII on CHO cells. The photodegraded PfII exhibited significant phototoxicity, although the fluorescence was bleached by more than 70%. The results show that PfII causes major skin photosensitization and that the other compounds produce no substantial skin sensitivity. Our studies suggest that photodegradation of PfII with 630 nm light has little influence on the phototoxicity of the compound. In addition, skin sensitivity was not alleviated with prior photobleaching with 405 nm light.