Synthesis and biological evaluation of methoxyphenyl porphyrin derivatives as potential photodynamic agents

Quantitative Structure-Property Relationship Modelling for the Prediction of Singlet Oxygen Generation by Heavy-Atom-Free BODIPY Photosensitizers*

Heavy-atom-free sensitizers forming long-living triplet excited states via the spin-orbit charge transfer intersystem crossing (SOCT-ISC) process have recently attracted attention due to their potential to replace costly transition metal complexes in photonic applications. The efficiency of SOCT-ISC in BODIPY donor-acceptor dyads, so far the most thoroughly investigated class of such sensitizers, can be finely tuned by structural modification. However, predicting the triplet state yields and reactive oxygen species (ROS) generation quantum yields for such compounds in a particular solvent is still very challenging due to a lack of established quantitative structure-property relationship (QSPR) models. In this work, the available data on singlet oxygen generation quantum yields (ΦΔ ) for a dataset containing >70 heavy-atom-free BODIPY in three different solvents (toluene, acetonitrile, and tetrahydrofuran) were analyzed. In order to build reliable QSPR model, a series of new BODIPYs were synthesized that bear different electron donating aryl groups in the meso position, their optical and structural properties were studied along with the solvent dependence of singlet oxygen generation, which confirmed the formation of triplet states via the SOCT-ISC mechanism. For the combined dataset of BODIPY structures, a total of more than 5000 quantum-chemical descriptors was calculated including quantum-chemical descriptors using density functional theory (DFT), namely M06-2X functional. QSPR models predicting ΦΔ values were developed using multiple linear regression (MLR), which perform significantly better than other machine learning methods and show sufficient statistical parameters (R=0.88-0.91 and q2 =0.62-0.69) for all three solvents. A small root mean squared error of 8.2 % was obtained for ΦΔ values predicted using MLR model in toluene. As a result, we proved that QSPR and machine learning techniques can be useful for predicting ΦΔ values in different media and virtual screening of new heavy-atom-free BODIPYs with improved photosensitizing ability.

Antitumor effects evaluation of a novel porphyrin derivative in photodynamic therapy

In this paper, the antitumor activity of a novel porphyrin-based photosensitizer 5,10,15,20-tetrakis[(5-diethylamino)pentyl] porphyrin (TDPP) was reported in vitro and in vivo. The photophysical and cellular properties of TDPP were investigated. The singlet oxygen generation quantum yield of TDPP was detected; it showed a high singlet oxygen quantum yield of 0.52. The intracellular distribution of photosensitizer was detected with laser scanning confocal microscopy. The efficiency of TDPP-photodynamic therapy (PDT) in vitro was analyzed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and in situ trypan blue exclusion test. Treated with a 630-nm laser, TDPP can kill cultured human esophageal cancer cell line (Eca-109) cells and reduce the growth of Eca-109 xenograft tumors significantly in BABL/c nude mice. And histopathological study was also used to confirm the antitumor effect. It has the perspective to be developed as a new antitumor drug in photodynamic therapy and deserves further investigation.

Synthesis of three novel imidazolyl-appended porphyrins and their cytostatic and phototoxic activity on A431 cells

Three imidazolyl-appended porphyrins were synthesized and characterized by 1 H NMR, elemental analyses, MS and UV-vis spectra. Anticancer activities of porphyrins have been evaluated against cutaneous squamous cell carcinoma (A431 cells) in vitro. The results indicate that the porphyrins have high selective cytotoxicity towards A431 cells in the absence of light and improved phototoxic activity upon exposure to UV light. The yield of singlet oxygen generated by porphyrins were also evaluated by measuring the absorption decay of 1,3-diphenylisobenzofuran (DPBF) in DMF. The phototoxicities of porphyrins against A431 cells were enhanced along with the increase of singlet oxygen.

Photosensitizing and radiosensitizing effects of mitoxantrone: combined chemo-, photo-, and radiotherapy of DFW human melanoma cells

This study evaluated the effects of mitoxantrone (MX), an antitumor agent, as a sensitizer to both photodynamic and radiation therapy in DFW human melanoma cells. Cells were incubated with MX at different concentrations for 90 min and then exposed to non-coherent light at different fluence rates and/or X-ray ionizing radiation at different dose rates. Combinatorial effects of this chemo-, photo-, and radiotherapy were also evaluated. MX had no significant effects on viability at moderate doses but had a strong cytotoxic effect on cancer cells when used as a photosensitizer. MX also acted as a potent radiosensitizer. We observed a dose-dependent effect on cell viability in cells exposed to MX in combination with phototherapy and radiotherapy. Strong synergistic effects were observed for combinations of two or more treatment methods, which, in some cases, induced complete cell death. Thus, a combination of ionizing radiation with MX-mediated photodynamic therapy could serve as a new method for cancer therapy with fewer adverse side effects.

Photodynamic therapy-induced killing is enhanced in depigmented metastatic melanoma cells

The resistance of pigmented human melanomas over their unpigmented counterparts to a number of therapies has suggested that the presence of intracellular melanin plays a role in rendering these cells less susceptible to cell death, probably through the ability of this pigment to act as an intracellular antioxidant, thus neutralizing chemotherapeutic-induced ROS (reactive oxygen species). PDT (photodynamic therapy) was recently suggested as an attractive, adjunctive therapy owing to its cellular specificity and limited side effects. In the present study, we propose that first depigmenting melanomas with a reversible TYR (tyrosinase) inhibitor such as PTU (phenylthiourea) increases their susceptibility to HYP-PDT (hypericin-mediated PDT). Pigmented [UCT Mel-1 (University of Cape Town melanoma cell line 1)] and unpigmented (A375) melanomas were first characterized with respect to their TYR activities and melanin quantities and then treated with a TYR inhibitor for 48 h. Cell viability assays after treatment with 3 μM HYP-PDT showed a significant increase in cell death in depigmented melanomas compared with untreated melanomas that returned to the level of untreated melanoma cells on removing the TYR inhibitor. The present study supports the hypothesis that combining the inhibition of melanogenesis with PDT should be explored as a valid therapeutic target for the management of advanced melanoma.

Synthesis of asymmetricallymeso-substituted porphyrins bearing amino groups as potential cationic photodynamic agents

Novel asymmetrically meso-substituted porphyrins bearing amino groups have been synthesized as precursors of cationic photodynamic agents. The amphiphilic character of these porphyrins was increased by the presence of a high lipophilic trifluoromethyl group. Different patterns of porphyrin structures were obtained from meso-4-[(3- N , N -dimethylaminopropoxy)phenyl] dipyrromethane 1, which was formed by the condensation of 4-(3- N , N -dimethylaminopropoxy) benzaldehyde with a large excess of pyrrole. This reaction takes place at high temperature with a yield of 59%. This reaction was also attempted under acid-catalyzed condensation at room temperature. However, under these conditions, the amino group reduces the catalyst and the reaction does not take place. To obtain porphyrins, dipyrromethane 1 was condensed with aldehydes in the presence of trifluoroacetic acid ( TFA ) under different conditions. First, 1 reacted with 4-(3- N , N -dimethylaminopropoxy)benzaldehyde in dichloromethane catalyzed by TFA (∼4 times TFA /1 molar ratio) to obtain 6.2% of 5,10,15,20-tetrakis(4-[3- N , N -dimethylaminopropoxy]phenyl)porphyrin ( A4-porphyrin). Under similar conditions, reaction of 1 with 4-(trifluoromethyl)benzaldehyde produces 5,15-di(4-[3- N , N -dimethylaminopropoxy]phenyl)-10,20-di(4-trifluoromethylphenyl)porphyrin ( A2B2- porphyrin ) with a 4.8% yield. This procedure also yields a mixture of porphyrins, which were formed due to acidolysis of 1. When a minor amount of TFA was used in acetonitrile, the yield of A2B2-porphyrin was very poor (∼0.4%). On the other hand, condensation of 1 with 4-trifluoromethylbenzaldehyde and 4-(3- N , N -dimethylaminopropoxy)benzaldehyde catalyzed by TFA (∼2 times TFA /1 molar ratio) in acetonitrile yields 9.3% of 5-(4-trifluoromethylphenyl)-10,15,20-tris(4-[3- N , N -dimethylaminopropoxy]phenyl)porphyrin ( A3B-porphyrin ). A2B2and A4porphyrins were also isolated with 6.0 and 2.0%, respectively. Finally, exhaustive methylation of amino porphyrins produces cationic sensitizers (>94% yield). Absorption and fluorescence spectroscopic studies of these sensitizers were compared in N , N -dimethylformamide. In these porphyrins, the cationic centers are isolated from the porphyrin ring by a propoxy bridge. Thus, the cationic charges have minimal influence on the photophysical properties of the sensitizers. In addition, this chain provides a higher mobility of the charge, which could facilitate interaction with the outer membrane of the Gram-negative bacteria. These amphiphilic cationic porphyrins are promising photosensitizers with potential applications in bacterial inactivation by photodynamic therapy.

Far-red absorbing azodipyrrin dyes — Synthesis, X-ray crystallographic, and spectral characterization of 1,9-diazodipyrrins and their metal complexes

A series of novel 1,9-diazodipyrrins (4) were readily synthesized by reacting aryldiazonium salts with 5-aryldipyrromethanes under both acidic and basic conditions. The zinc complex of 1,9-diphenylazodipyrrin (5aZn) was confirmed by X-ray crystallographic analysis, and 1,9-diazodipyrrins and their zinc and nickel complexes (5M) were characterized by 1H and 13C NMR, IR, UV–vis, and MS. All of the metal complexes absorb almost all colours of the rainbow; the absorption maximums are >650 nm and the half-band widths are over 100 nm. The fluorescence of the zinc complexes of 1,9-diphenylazodipyrrin (5aZn) and 1,9-di(2-iodophenylazo)dipyrrin (5cZn) were also explored.

Possible in vivo mechanisms involved in photodynamic therapy using tetrapyrrolic macrocycles

Photodynamic therapy (PDT) mediated by oxidative stress causes direct tumor cell damage as well as microvascular injury. To improve this treatment new photosensitizers are being synthesized and tested. We evaluated the effects of PDT with 5,10,15,20-tetrakis(4-methoxyphenyl)-porphyrin (TMPP) and its zinc complex (ZnTMPP) on tumor levels of malondialdehyde (MDA), reduced glutathione (GSH) and cytokines, and on the activity of caspase-3 and metalloproteases (MMP-2 and -9) and attempted to correlate them with the histological alterations of tumors in 3-month-old male Wistar rats, 180 ± 20 g, bearing Walker 256 carcinosarcoma. Rats were randomly divided into five groups: group 1, ZnTMPP+irradiation (IR) 10 mg/kg body weight; group 2, TMPP+IR 10 mg/kg body weight; group 3, 5-aminolevulinic acid (5-ALA+IR) 250 mg/kg body weight; group 4, control, no treatment; group 5, only IR. The tumors were irradiated for 15 min with red light (100 J/cm², 10 kHz, 685 nm) 24 h after drug administration. Tumor tissue levels of MDA (1.1 ± 0.7 in ZnTMPP vs 0.1 ± 0.04 nmol/mg protein in control) and TNF-α (43.5 ± 31.2 in ZnTMPP vs 17.3 ± 1.2 pg/mg protein in control) were significantly higher in treated tumors than in controls. Higher caspase-3 activity (1.9 ± 0.9 in TMPP vs 1.1 ± 0.6 OD/mg protein in control) as well as the activation of MMP-2 (P < 0.05) were also observed in tumors. These parameters were correlated (Spearman correlation, P < 0.05) with the histological alterations. These results suggest that PDT activates the innate immune system and that the effects of PDT with TMPP and ZnTMPP are mediated by reactive oxygen species, which induce cell membrane damage and apoptosis.

Hypericin phototoxicity induces different modes of cell death in melanoma and human skin cells

Hypericin, the major component of St. John's Wort, absorbs light in the UV and visible ranges whereupon it becomes phototoxic through the production of reactive oxygen species. Although photodynamic mechanisms (i.e. through endogenous photosensitizers) play a role in UVA phototherapy for the treatment of skin disorders such as eczema and psoriasis, photodynamic therapy employing exogenous photosensitizers are currently being used only for the treatment of certain forms of non-melanoma skin cancers and actinic keratoses. There are few reports however on its use in treating melanomas. This in vitro study analyses the phototoxic effect of UVA (400-315 nm) - activated hypericin in human pigmented and unpigmented melanomas and immortalised keratinocytes and melanocytes. We show that neither hypericin exposure nor UV irradiation alone reduces cell viability. We show that an exposure to 1 microM UVA-activated hypericin does not bring about cell death, while 3 microM activated hypericin induces a necrotic mode of cell death in pigmented melanoma cells and melanocytes and an apoptotic mode of cell death in non-pigmented melanoma cells and keratinocytes. We hypothesis that the necrotic mode of cell death in the pigmented cells is possibly related to the presence of melanin-containing melanosomes in these cells and that the hypericin-induced increase in reactive oxygen species leads to an increase in permeability of melanosomes. This would result in toxic melanin precursors (of an indolic and phenolic nature) leaking into the cytoplasm which in turn leads to cell death. Hypericin localisation in the endoplasmic reticulum in these cells shown by fluorescent microscopy, further support a disruption in cellular processing and induction of cell death. In contrast, this study shows that cells that do not contain melanosomes (non-pigmented melanoma cells and keratinocytes) die by apoptosis. Further, using a mitochondrial-specific fluorescent dye, we show that intracellular accumulation of hypericin induces a mitochondrial-associated caspase-dependent apoptotic mode of cell death. This work suggests that UVA is effective in activating hypericin and that this phototoxicity may be considered as treatment option in some cases of lentigo maligna or lentigo maligna melanoma that are too large for surgical resection.

Spectroscopic properties and photodynamic effects of new lipophilic porphyrin derivatives: efficacy, localisation and cell death pathways

Photodynamic therapy (PDT) and photodynamic diagnostics (PDD) of cancer are based on the use of non-toxic dyes (photosensitisers) in combination with harmless visible light. This paper reports physicochemical properties, cell uptake, localisation as well as photodynamic efficiency of two novel lipophilic porphyrin derivatives, suitable for use as PDT sensitisers. Both compounds are characterised by high quantum yield of singlet oxygen generation which was measured by time-resolved phosphorescence. Photodynamic in vitro studies were conducted on three cancer cell lines. Results of cell survival tests showed negligible dark cytotoxicity but high phototoxicity. The results also indicate that cell death is dependent on energy dose and time following light exposure. Using confocal laser scanning microscopy both compounds were found to localise in the cytoplasm around the nucleus of the tumour cells. The mode of cell death was evaluated based on the morphological changes after differential staining. In summary, good photostability, high quantum yield of singlet oxygen and biological effectiveness indicate that the examined lipophilic porphyrin derivatives offer quite interesting prospects of photodynamic therapy application.

Photodynamic damages induced by a monocationic porphyrin derivative in a human carcinoma cell line

The photokilling activity of 5-(4-trimethylammoniumphenyl)-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin (CP) was evaluated on a Hep-2 human larynx-carcinoma cell line. Cell treatment was carried out with 5 microM CP incorporated into liposomal vesicles. Under violet-blue exciting light, the red fluorescence of CP was mainly detected as a filamentous pattern characteristic of mitochondrial localization. Similar pattern was also observed using rhodamine 123 in Hep-2 cells. No dark cytotoxicity was observed using 5 microM CP concentration and long incubation time (24 h). Using Hoechst-33258 and caspase-3 immunostaining methods, cell cultures treated for 24 h with CP and exposed to light for 7.5 min (27 J/cm2) showed a great amount of apoptotic cells (40%). In contrast, necrotic cells (58%) were observed using the same drug concentration but irradiated for 15 min (54 J/cm2). The results show that CP can induce different mechanisms of cell death depending on irradiation doses in the photodynamic treatments, which makes this agent an interesting sensitizer with potential application in photodynamic tumor therapy.

Photodynamic inactivation of Escherichia coli by novel meso-substituted porphyrins by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl and 4-(trifluoromethyl)phenyl groups

The photodynamic effect of novel cationic porphyrins, with different pattern of meso-substitution by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, have been studied in both solution bearing photooxidizable substrates and in vitro on a typical Gram-negative bacterium Escherichia coli. In these sensitizers, the cationic groups are separated from the macrocycle ring by a propoxy spacer. Thus, the charges have a high mobility and a minimal influence on photophysical properties of the porphyrin. These compounds produce singlet molecular oxygen, O2(1Delta(g)), with quantum yields of approximately 0.41-0.53 in N,N-dimethylformamide. In methanol, the l-tryptophan photodecomposition increases with the number of cationic charges in the sensitizer. In vitro investigations show that cationic porphyrins are rapidly bound to E. coli cells in approximately 5 min. A higher binding was found for A3B3+ porphyrin, which is tightly bound to cells still after three washing steps. Photosensitized inactivation of E. coli cellular suspensions follows the order: A3B3+ > A44+>> ABAB2+ > AB3+. Under these conditions, a negligible effect was found for 5,10,15,20-tetra(4-sulfonatophenyl)porphyrin (TPPS4(4-)) that characterizes an anionic sensitizer. Also, the results obtained for these new cationic porphyrins were compared with those of 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin (TTAP4+), which is a standard active sensitizer established to eradicate E. coli. The photodynamic activity of TTAP4+ is quite similar to that produced by A4(4+). Studies in an anoxic condition indicate that oxygen is necessary for the mechanism of action of photodynamic inactivation of bacteria. The higher photodynamic activity of A3B3+ was confirmed by growth delay experiments. Photodynamic inactivation capacities of these sensitizers were also evaluated in E. coli cells immobilized on agar surfaces. Under these conditions, A3B3+ porphyrin retains a high activity to inactivate localized bacterial cells. Therefore, tricationic porphyrin A3B3+ is an interesting sensitizer with potential applications in photodynamic inactivation of bacteria in liquid suspensions or on surfaces.

Photoinactivation ofEscherichia coliusing porphyrin derivatives with different number of cationic charges

The photodynamic effect of meso-substituted cationic porphyrins, 5-[4-(trimethylammonium)phenyl]-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin iodide 1, 5,10-di(4-methylphenyl)-15,20-di(4-trimethylammoniumphenyl)porphyrin iodide 2 and 5-(4-trifluorophenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin iodide 3, have been investigated in both homogeneous medium bearing photooxidizable substrates and in vitro on a typical gram-negative bacterium Escherichia coli. Absorption and fluorescence spectroscopic studies were compared in N,N-dimethylformamide. Fluorescence quantum yields (varphiF) of 0.10, 0.06 and 0.08 were calculated for porphyrins 1, 2 and 3, respectively. The singlet molecular oxygen, O2(1Deltag), production was evaluated using 9,10-dimethylanthracene yielding values of 0.66, 0.36 and 0.42 for porphyrins 1, 2 and 3, respectively. Guanosine 5'-monophosphate was used as biological substrate model. Similar decomposition of guanosine 5'-monophosphate was obtained using these cationic porphyrins as sensitizer. In biological medium, photosensitized inactivation of E. coli was analyzed using cells without and with one washing step. E. coli cultures were treated with sensitizer at 37 degrees C for 30 min in dark. In both procedures, a higher photoinactivation of cells (>99.999%) was found for cells treated with 10 microM of tricationic porphyrin 3 and irradiated for 5 min with visible light. Porphyrins 1 and 2 only show an important photodamage when the cells are irradiated without washing step. These results indicated that the tetracationic porphyrin 3 could be a promising sensitizer with potential applications in the photoinactivation of bacterial cells by photodynamic therapy.

Synthesis, properties, and photodynamic inactivation of Escherichia coli using a cationic and a noncharged Zn(II) pyridyloxyphthalocyanine derivatives

The photodynamic effect of a cationic Zn(II) N-methylpyridyloxyphthalocyanine (ZnPc 2) and a noncharged Zn(II) pyridyloxyphthalocyanine (ZnPc 1) has been compared in both homogeneous media bearing photooxidizable substrates and in vitro using a typical Gram-negative bacterium Escherichia coli. Absorption and fluorescence spectroscopic studies were analyzed in different media. Fluorescence quantum yields (varphiF) of 0.23 for ZnPc 1 and 0.22 for ZnPc 2 were calculated in N,N-dimethylformamide (DMF). The singlet molecular oxygen, O2(1Deltag), production was evaluated using 9,10-dimethylanthracene (DMA) in DMF yielding values of PhiDelta=0.56 for ZnPc 1 and 0.59 for ZnPc 2. A faster decomposition of L-tryptophan (Trp), which was used as biological substrate model, was obtained using ZnPc 2 as a sensitizer with respect to ZnPc 1. In biological medium, the E. coli cultures were treated with 10 microM of sensitizer for different times at 37 degrees C in the dark. Both ZnPcs 1 and 2 are rapidly bound to E. coli cells in 5 min and the amount of cell-bound sensitizer is not appreciably changed incubating the cultures for longer times. The recovered ZnPc 2 after one washing step is approximately 3 times higher than 1, reaching a value of approximately 3 nmol/10(6) cells. After irradiation with visible light, a higher photoinactivation of cells was found for ZnPc 2. Thus, a approximately 4.5 log (99.997%) decrease of cell survival was obtained after 30 min of irradiation. On the other hand, a very low photodamage was found for cells treated with ZnPc 1 (approximately 0.5 log). Also, these results were established by stopping of growth curves for E. coli. In the structure of ZnPc 2, the cationic centers are isolated from the phthalocyanine ring by an ether bridge, which also provides a higher mobility of the charges facilitating the interaction with the outer membrane of the Gram-negative bacteria. These studies show that cationic ZnPc 2 is an efficient phototherapeutic agent with potential applications in photodynamic inactivation of bacteria.

Synthesis and photodynamic activity of zinc(II) phthalocyanine derivatives bearing methoxy and trifluoromethylbenzyloxy substituents in homogeneous and biological media

Two zinc(II) phthalocyanines bearing either four methoxy (ZnPc 3) or trifluoromethylbenzyloxy (ZnPc 4) substituents have been synthesized by a two-step procedure starting from 4-nitrophthalonitrile. Absorption and fluorescence spectroscopic studies were analyzed in different media. These compounds are essentially non-aggregated in the organic solvent. Fluorescence quantum yields (phi(F)) of 0.26 for ZnPc 3 and 0.25 for ZnPc 4 were calculated in tetrahydrofuran (THF). The photodynamic activity of these compounds was compared in both THF containing photooxidizable substrates and in vitro on Hep-2 human larynx-carcinoma cell line. The production of singlet molecular oxygen, O(2)((1)Delta(g)), was determined using 9,10-dimethylanthracene yielding values of approximately 0.56 for both sensitizers. Under these conditions, the addition of beta-carotene (Car) suppresses the O(2)((1)Delta(g))-mediated photooxidation. In biological medium, no dark cytotoxicity was found for cells incubated with 0.1 microM of phthalocyanines 3 and 4 for 24 h. However, under similar conditions 0.5 microM of ZnPc 4 was toxic (70% cell survival). The uptake into Hep-2 cells was evaluated using 0.1muM of sensitizer, reaching values of approximately 0.05 nmol/10(6) cells after 3h of incubation at 37 degrees C. The cell survival after irradiation of the cultures with visible light was dependent upon both light exposure level and intracellular sensitizer concentration. A higher photocytotoxic effect was found for ZnPc 3 with respect to 4 (32%/70% cell survival after 15 min of irradiation). Also, these studies were performed treating the cells with 0.5 microM of ZnPc 3. In this case, an increase in the uptake (approximately 0.28 nmol/10(6) cells) was observed, which is accompanied by a higher photocytotoxic activity (20% cell survival). These results show that even though both sensitizer present similar photophysical properties in homogeneous medium, the photodynamic behavior in cellular media can significantly be changed.

Photodynamic activity of monocationic and non-charged methoxyphenylporphyrin derivatives in homogeneous and biological media

A novel 5-[4-(trimethylammonium)phenyl]-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin iodide (2) has been synthesized. A positive charge was incorporated at a peripheral position to increase the amphiphilic character of the structure. The photodynamic effect of the cationic porphyrin 2 was compared with that of non-charged 5-(4-aminophenyl)-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin (1), both in a homogeneous medium bearing photooxidizable substrates and in vitro on the Hep-2 human larynx carcinoma cell line. Absorption and fluorescence spectroscopic studies in different media show that 2 is essentially unaggregated in solution, and also in human cells. The singlet molecular oxygen, O2(1delta(g)), production was evaluated using 9,10-dimethylanthracene in N,N-dimethylformamide, yielding phi(delta) values of approximately 0.66 for both porphyrins. The addition of beta-carotene suppresses the O2(1delta(g))-mediated photooxidation. L-Tryptophan and guanosine 5'-monophosphate were used as biological substrate models. Porphyrin 2 sensitizes the decomposition of both compounds faster than does 1. In the biological medium, no dark cytotoxicity was observed, even though a high porphyrin concentration (10 microM) and a long incubation time (24 h) were employed. Cell treatments were performed with 5 microM of porphyrin for 24 h. Under these conditions, the uptake of porphyrin 2 into Hep-2 was about 3 times higher than that of 1. Cell survival after irradiation with visible light was dependent upon both the light exposure level and intracellular sensitizer concentration. Thus, a higher photocytotoxic effect was found for porphyrin 2 in comparison to 1. These results show that the amphiphilic monocationic porphyrin 2 could be a promising model for phototherapeutic agents with potential applications in tumor cell inactivation by photodynamic therapy.

Pharmacokinetic and tumour-photosensitizing properties of methoxyphenyl porphyrin derivative

The photokilling activity of 5-[4-N-(2',6'-dinitro-4'-trifluoromethylphenyl) aminophenyl]-10,15,20-tris(2,4,6-trimethoxy phenyl) porphyrin (CF3) was evaluated on a Hep-2 human larynx-carcinoma cell line. An apoptotic mechanism of cell death was found at low irradiation doses. Pharmacokinetic and tumour-photosensitizing properties were studied in mice. The results show that a different mechanism of cell death can be induced depending on the irradiation doses in the photodynamic treatments with CF3, which makes this agent an interesting sensitizer for potential tumour photosensitizer.