Biological activities of phthalocyanines--X. Syntheses and analyses of sulfonated phthalocyanines

Dual Cherenkov Radiation-Induced Near-Infrared Luminescence Imaging and Photodynamic Therapy toward Tumor Resection

Cherenkov radiation (CR), the blue light seen in nuclear reactors, is emitted by some radiopharmaceuticals. This study showed that (1) a portion of CR could be transferred in the region of the optical spectrum, where biological tissues are most transparent: as a result, upon radiance amplification in the near-infrared window, the detection of light could occur twice deeper in tissues than during classical Cherenkov luminescence imaging and (2) Cherenkov-photodynamic therapy (CR-PDT) on cells could be achieved under conditions mimicking unlimited depth using the CR-embarked light source, which is unlike standard PDT, where light penetration depth is limited in biological tissues. Both results are of utmost importance for simultaneous applications in tumor resection and post-resection treatment of remaining unresected margins, thanks to a molecular construct designed to raise its light collection efficiency (i.e., CR energy transfer) by conjugation with multiple CR-absorbing (water-soluble) antenna followed by intramolecular-FRET/TBET energy transfers.

The Dimerisation of Phthalocyanines

In this review, we have shown that the dimerisation of phthalocyanine compounds, notably here the sulphonated aluminium phthalocyanines, is dependent upon concentration, on the medium in which the dye is dissolved, and upon pH. Complex equilibria between various monomer and dimer species are observed as a function of pH, and the probable structures of the dimers elucidated by semi-empirical and ab initio calculations. The formation of a red-shifted dimer leads to the quenching of monomer singlet state in concentrated solution, in reverse micelles, and in lipid vesicles, and this behaviour can account for the fluorescence intensity distributions and decay characteristics of phthalocyanine dyes in living cells as a function of irradiation time.

Comparative Investigation of Peripheral and Nonperipheral Zinc Phthalocyanine-Based Polycarbazoles in Terms of Optical, Electrical, and Sensing Properties

In this study, nonperipherally alkyl-linked carbazole conjugated novel zinc(II) phthalocyanine was synthesized by cyclotetramerization reaction of 6-(9 H-carbazol-9-yl)hexane-1-thiol and 3,6-bis(tosyloxy) phthalonitrile in a one-step reaction. Optical, electrical, and sensing properties of this super structured polycarbazole obtained by electropolymerization are compared with peripherally alkyl-linked polycarbazole-based zinc(II) phthalocyanine. It has been found that the attachment of alkyl-linked carbazoles to the phthalocyanine molecule in either peripheral or nonperipheral positions has a great effect on the optical and electrical properties and sensing ability of the resulting polycarbazole derivatives. P(n-ZnPc) has the highest electrochromic contrast (70.5%) among the derivatives of zinc(II) phthalocyanines in the literature. In addition to these, the sensor platform has been successfully established, and analytical optimizations have been carried out. When the sensors prepared with zinc(II) phthalocyanine are examined, it was specified that the n-ZnPc- co-TP/GOx was ranked first in the literature with high sensor response and stability. As a result, by changing of the peripheral and nonperipheral position of phthalocyanines, their physical properties can be tuned to meet the requirements of desired technological application.

Novel carbazole containing zinc phthalocyanine photosensitizers: Synthesis, characterization, photophysicochemical properties and in vitro study

Tetra and octa substituted novel zinc(II) phthalocyanines (3a and 5a) bearing carbazole groups were synthesized by cyclotetramerization of respective phthalonitrile derivatives (3 and 5). The zinc(II) phthalocyanines (3a and 5a) were converted into the water-soluble quaternized derivatives (3b and 5b) by utilizing dimethylsulphate as quaternizing agent. The synthesized novel compounds were confirmed thruogh FT-IR, UV-vis and MALDI-TOF mass spectroscopic data and elemental analysis as well. The photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen generation) properties of new phthalocyanines were determined in dimethylsulfoxide (DMSO). The photophysical and photochemical results were compared according to the number of the carbazole groups on the phthalocyanine core. Additionaly, in vitro photocytotoxicity of the targeted compounds were examined against to hepato cellular carcinoma (HuH-7) cancer cell line for determination of their photosensitizing ability.

Sonodynamic therapy using 5-aminolevulinic acid enhances the efficacy of bleomycin

Sonodynamic therapy (SDT) kills tumor cells through the synergistic effects of ultrasound and a sonosensitizer agent. We examined whether 5-aminolevulinic acid (5-ALA)-based SDT at 1 or 3 MHz could enhance the cytotoxicity of bleomycin (BLM) toward mouse mammary tumor cells both in vitro and in vivo. At 1 MHz, cell viability in the 5-ALA-based SDT group at 1, 2, and 3 W/cm(2) was 34.30%, 50.90%, and 60.16%, respectively. Cell viability in the 5-ALA-based SDT+BLM group at 1, 2, and 3 W/cm(2) was 0.09%, 0.32%, and 0.17%, respectively. In contrast, at 3 MHz, 5-ALA-based SDT+BLM did not show pronounced cytotoxicity. In the in vivo study, 5-ALA-based SDT+BLM was significantly more cytotoxic than 5-ALA-based SDT at 1 MHz and 3 MHz. These findings suggest that the mechanism of tumor shrinkage induced by 5-ALA-based SDT+BLM might involve not only direct cell killing, but also vascular shutdown. Thus, we show here that 5-ALA-based SDT enhances the efficacy of BLM both in vitro and in vivo.

Sulfonated Phthalocyanines: Photophysical Properties, in vitro Cell Uptake and Structure-activity Relationships

Aluminium phthalocyanines sulfonated to a different degree ( AlPcS n) and consisting of various isomeric species were studied by spectroscopic techniques to determine their tendencies to form dimers and aggregates. These characteristics were compared with the cell-penetrating properties of the species, using the Ehrlich ascites mouse tumor cell line, to arrive at structure-activity relationships. AlPcS n preparations consisting of the least number of isomeric species exhibited the highest tendency to form dimers and aggregates, whereas the more complex preparations, consisting of many isomeric products, showed more consistent monomeric features in aqueous environments. Uptake in cells was shown to correlate well with the overall hydrophobicity of the preparation and inversely with its degree of aggregation in the extracellular environment. Among the purified, single isomeric AlPcS n the amphiphilic disulfonated AlPcS 2a , enriched in positional isomers featuring sulfonate groups on adjacent phthalic subunits, showed the best membrane-penetrating properties. Even higher cell uptake was observed for the AlPcS 2mix reflecting a combination of optimal lipophilicity and a low degree of aggregation. Similarly, in the case of AlPcS 4, the pure isomeric compound showed less cell uptake than the mixed isomeric preparation of similar hydrophobicity, reflecting the higher degree of aggregation invoked by its symmetrical structure. Our data indicate that mixed sulfonated phthalocyanine preparations may exert higher photodynamic efficacy in biological applications as compared to the pure isomeric constituents.

Isomeric separation and identification of tetra-, tri-, and di-β-sulphonic phthalocyanine zinc complexes

The synthesis, isomeric separation, and identification of β-sulphonic phthalocyanine zinc complexes were reported. While the sulphonic phthalocyanines have been studied extensively, the development of separation technology may enable deeper insights into their isomeric constitution. An ion-pair reversed-phase high performance liquid chromatography (IP-RP-HPLC) method was developed to separate the sulphonic phthalocyanine isomers. The results showed that the product of the condensation reaction is a mixture of all possible isomers with statistical distribution. Several isomers were obtained and structural determination was undertaken by NMR. Based on the IP-RP-HPLC elution sequence of these well-identified isomers, a relationship between the structure and efficiency was deduced: closely spaced intervals of sulphonic groups lead to higher hydrophobicity and shorter retention times on HPLC. Based on this relationship, each HPLC peak was assigned to the corresponding isomeric structure.

Copper-64 labeled sulfophthalocyanines for positron emission tomography (PET) imaging in tumor-bearing rats

Sulfonated metallophthalocyanines ( PcS ) are second generation photosensitizers for photodynamic therapy (PDT) of cancer. Metal-free H 2 PcS are readily labeled with 64 Cu ++ to yield a mixture of sulfonated [64 Cu ] CuPcS suitable for biodistribution studies in tumor-bearing rats by positron emission tomography (PET). Most of the 64 Cu activity was sequestrated within the kidneys (20%ID/g) and liver (12%ID/g) while tumor uptake values remained low (0.2%ID/g). Dissection and counting of individual tissue samples after the 24 h scan confirmed the uptake values derived from the PET images. The procedure can be applied to series of novel PcS to evaluate structure-tumor selectivity relationships as a parameter to select potential agents for photodynamic therapy.

Quenching of singlet photoexcited state of water soluble phthalocyanines and porphyrins by viologens interacting electrostatically

Quenching of photoexcited anionic and water-soluble phthalocyanines and 5,10,15,20-tetraarylporphyrins by viologens has been investigated. It was confirmed that the quenching of the singlet photoexcited state takes place, and that the mechanism is mostly a static one due to electrostatic interaction between the donor and the acceptor. The static mechanism was analyzed by curve-fitting of the relative emission intensity vs viologen concentration resulting in four kinds of mechanisms composed of static quenching accompanied partly by a dynamic one. The static mechanism was classified into two types: one mechanism is due to 1:n electrostatic interaction of the anionic sensitizer and the cationic acceptor, and other is a Perrin type for which the acceptor is incorporated into the quenching sphere around the sensitizer according to a Poisson distribution. The effect of micelles for the quenching was also studied including the effect of viologen with a long alkyl chain. The ionic micelles either incorporated or repulsed the ionic sensitizer and accepter resulting in either static quenching or prohibition of the quenching. Cationic phthalocyanines and porphyrins were also examined for the reaction with cationic viologens.

Efficient oxidations and photooxidations with molecular oxygen using metal phthalocyanines as catalysts and photocatalysts

Metal phthalocyanines can be very efficient as catalysts and photocatalysts in oxidation reactions using molecular oxygen as oxidant. Different types of soluble low molecular weight or oligomeric and insoluble heterogeneous catalysts and photocatalysts were developed. The heterogeneous metal phthalocyanines exist either impregnated on SiO 2, Al 2 O 3, charcoal and TiO 2 or covalently and coordinatively bound on SiO 2 and organic polymers or ionically bound on an organic ion exchanger. The catalytic oxidations of toxic sulfide and thiol derivative are studied. In addition, toxic phenols were employed as substrates for the photooxidation. Heterogeneous catalysts can exhibit higher activities then low molecular weight phthalocyanines. These systems exhibit a good stability for re-use. Photooxidations are more efficient than oxidations. A Si(IV) phthalocyanine derivative on a polymer ion exchanger is most active and stable. Also some examples for photooxidations in the direction of photochemical synthesis are given.

Predicting efficacy of photodynamic therapy by real-time FDG-PET in a mouse tumour model

Dynamic positron emission tomography (PET) combined with the constant infusion of 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) as a tracer permits real-time monitoring of systemic transient metabolic changes resulting from photodynamic therapy (PDT) in tumour bearing animals. The effect of PDT on tumour FDG uptake rates was evaluated using four different sulfonated phthalocyanine analogs as photosensitizers (PS) in combination with either continuous or fractionated illumination protocols. Mice bearing two EMT-6 tumours were infused with FDG to start PDT 30 min later. Dynamic images were acquired to produce FDG uptake over time for the treated and reference tumours. Practically all PDT protocols induced a reduction in the FDG uptake rates in the treated tumour during PDT, except for the zinc tetrasulfophthalocyanine, when using fractionated light, reflecting the low photodynamic efficacy of this PS. In general, the response to PDT was characterized by a rebound in the FDG uptake rate after illumination. A strong drop in FDG tumour uptake rates during PDT, followed by a strong rebound, together with short delay-to-response times, corresponded to optimal long-term tumour response outcomes. This dynamic FDG-PET protocol provides real-time observations to predict long-term PDT efficacy, while using fewer animals than conventional methods, thus making possible the rapid optimization of treatment parameters.

Synthesis and anchoring of antineoplastic ferrocene and phthalocyanine derivatives on water-soluble polymeric drug carriers derived from lysine and aspartic Acid

The general synthetic strategy towards water-soluble biodegradable drug carriers and the properties that they must have are discussed. The syntheses of water-soluble biodegradable copolymers of lysine and aspartic acid as potential drug-delivering devices, having amine-functionalised side chains are then described. Covalent anchoring of carboxylic acid derivatives of the antineoplastic ferrocene and photodynamically active phthalocyanine moieties to the amine-containing drug carrier copolymers under mild coupling conditions has been achieved utilising the coupling reagent O-benzotriazolyl-N,N,N^′,N^′-tetramethyluronium hexafluorophosphate to promote formation of the biodegradable amide bond. Even though the parent antineoplastic ferrocene and phthalocyanine derivatives are themselves insoluble in water at pH < 7, the new carrier-drug conjugates that were obtained are well water-soluble.

Oxidative degradation of Remazol Turquoise Blue G 133 by soybean peroxidase

Reactive dyes are widely employed in textile industries and their removal from wastewaters is a relevant environmental problem. In addition to chemical and physical methods, several bioremediation approaches, involving intact micro-organisms or isolated enzymes, have been proposed to decolorize dye solutions. In this paper, we report the complete and fast decolourization of a Cu(II)-phthalocyanine based reactive dye (Remazol Turquoise Blue G 133) by means of the soybean peroxidase/H(2)O(2) system. The oxidative degradation of the dye in aqueous solution at 25°C was studied as function of pH, revealing a quantitative decolourization yield at acidic pH values with a maximum of activity at pH 3.3. The reaction products were identified and characterized by HPLC-diode array detector (DAD)-mass spectrometry (MS), ionic chromatography and EPR techniques. This analysis showed that the enzyme catalyses the breaking of the phthalocyanine ring producing sulfophthalimide as the main degradation product, and the release of stoichiometric amount of ammonium and Cu(II) ions.

Synthesis and phototoxicity of polyethylene glycol (PEG) substituted metal-free and metallo-porphyrins: effect of PEG chain length, coordinated metal, and axial ligand

Treatment of 5,10,15,20-tetra(pentafluorophenyl) porphyrins with polyethylene glycol (PEG) halides and sodium sulfide is a mild and efficient route to water-soluble PEG substituted porphyrins. The method has been used to access a series of free-base and metallated PEG porphyrins, which have been investigated for photodynamic activity against Human Caucasian colon adenocarcinoma (Caco2) cells. Toxicity, in the presence and absence of light, is shown to be affected by the length of the PEG chain, nature of coordinated metal and axial ligand.

Photodynamic Therapy: Porphyrins and Phthalocyanines as Photosensitizers

The present work is focussed on the principles of photodynamic therapy (PDT), emphasizing the photochemical mechanisms of reactive oxygen species formation and the consequent biochemical processes generated by the action of reactive oxygen species on various biological macromolecules and organelles. This paper also presents some of the most used photosensitizers, including Photofrin, and the new prototypes of photosensitizers, analysing their physicochemical and spectroscopic properties. At this point, the review discusses the therapeutic window of absorption of specific wavelengths involving first- and second-generation photosensitizers, as well as the principal light sources used in PDT. Additionally, the aggregation process, which consists in a phenomenon common to several photosensitizers, is studied. J-aggregates and H-aggregates are discussed, along with their spectroscopic effects. Most photosensitizers have a significant hydrophobic character; thus, the study of the types of aggregation in aqueous solvent is very relevant. Important aspects of the coordination chemistry of metalloporphyrins and metallophthalocyanines used as photosensitizers are also discussed. The state-of-the-art in PDT is evaluated, discussing recent articles in this area. Furthermore, macrocyclic photosensitizers, such as porphyrins and phthalocyanines, are specifically described. The present review is an important contribution, because PDT is one of the most auspicious advances in the therapy against cancer and other non-malignant diseases.

The chemistry, photophysics and photosensitizing properties of phthalocyanines

Phthalocyanines (Pcs) and naphthalocyanines (Ncs) are being extensively studied as photosensitizers for photodynamic therapy (PDT) of cancer. They strongly absorb clinically useful red light, with maxima around 670 nm and 770 nm respectively. Chelated with appropriate diamagnetic metal ions, they exhibit high triplet yields and long triplet lifetimes. Energy transfer from the triplet dye to ground-state oxygen to yield singlet oxygen appears to be the main photosensitizing pathway in biological systems. Underivatized Pcs and Ncs can be incorporated in liposomes for in vivo administration. Sulphonation renders the dyes water soluble but also enhances dimerization to yield photochemically inactive aggregates. Tumour retention and cell membrane penetration of the dyes are strongly affected by the polarity of the macrocycle as well as the nature of the central metal ion and axial ligands. Among the sulphonated dyes, amphiphilic mono- and disulphonated derivatives exhibit particularly good cell membrane-penetrating properties, although the more highly sulphonated dyes show better tumour retention in vivo. At least in vitro, Pc dyes are more photoactive than the corresponding Nc dyes, which probably reflects the lower photostability of the latter.

Porphyrins as photosensitizers

The porphyrins have two important roles in photobiology: in photosynthesis, which has evolved and is highly organized morphologically; and in the photodynamic effect, which is adventitious. The damage to tissue that results from photodynamic action is regarded as arising from a number of pathways, but singlet oxygen generation is a major route. Even for the latter mechanism, a number of target molecules are possible. Compared with photosynthesis, it is a very disorganized process. Since the mid 1970s there have been increasing efforts to turn the photodynamic effect to good use as the basis of a phototherapy for cancer. The field has been dominated by the photosensitizer haematoporphyrin derivative. This is a complex mixture of molecules, and although we are learning more about it, it seems unlikely that it will be possible to separate out a useful single substance. A second generation of porphyrin sensitizers is emerging, which, unlike haematoporphyrin derivative, is designed for the job in hand. Some of these photosensitizers, especially the hydroporphyrins, look quite promising.

Photodynamic activity of substituted zinc trisulfophthalocyanines: role of plasma membrane damage

We recently reported that variations in cellular phototoxicity among a series of alkynyl-substituted zinc trisulfophthalocyanines (ZnPcS3Cn) correlates with their hydrophobicity, with the most amphiphilic derivatives showing the highest cell uptake and phototoxicity. In this study we address the role of the plasma membrane in the photodynamic response as it relates to the overall hydrophobicity of the photosensitizer. The membrane tracker dye 1-[4(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), which is incorporated into plasma membranes by endocytosis, was used to establish plasma membrane uptake by EMT-6 cells of the ZnPcS3C, by colocalization, and TMA-DPH membrane uptake rates after photodynamic therapy were used to quantify membrane damage. TMA-DPH colocalization patterns show plasma membrane uptake of the photosensitizers after short 1 h incubation periods. TMA-DPH plasma membrane uptake rates after illumination of the photosensitizer-treated cells show a parabolic relationship with photosensitizer hydrophobicity that correlates well with the phototoxicity of the ZnPcS3C,. After a 1 h incubation period, overall phototoxicity correlates closely with the postillumination rate of TMA-DPH incorporation into the cell membrane, suggesting a major role of plasma membrane damage in the overall PDT effect. In contrast, after a 24 h incubation, phototoxicity shows a stronger but imperfect correlation with total cellular photosensitizer uptake rather than TMA-DPH membrane uptake, suggesting a partial shift in the cellular damage responsible for photosensitization from the plasma membrane to intracellular targets. We conclude that plasma membrane localization of the amphiphilic ZnPcS3C6-C9 is a major factor in their overall photodynamic activity.

PET imaging of apoptosis with 64Cu-labeled streptavidin following pretargeting of phosphatidylserine with biotinylated annexin-V

PURPOSE

In vivo detection of apoptosis is a diagnostic tool with potential clinical applications in cardiology and oncology. Radiolabeled annexin-V (anxV) is an ideal probe for in vivo apoptosis detection owing to its strong affinity for phosphatidylserine (PS), the molecular flag on the surface of apoptotic cells. Most clinical studies performed to visualize apoptosis have used (99m)Tc-anxV; however, its poor distribution profile often compromises image quality. In this study, tumor apoptosis after therapy was visualized by positron emission tomography (PET) using (64)Cu-labeled streptavidin (SAv), following pre-targeting of apoptotic cells with biotinylated anxV.

METHODS

Apoptosis was induced in tumor-bearing mice by photodynamic therapy (PDT) using phthalocyanine dyes as photosensitizers, and red light. After PDT, mice were injected i.v. with biotinylated anxV, followed 2 h later by an avidin chase, and after another 2 h with (64)Cu-DOTA-biotin-SAv. PET images were subsequently recorded up to 13 h after PDT.

RESULTS

PET images delineated apoptosis in treated tumors as early as 30 min after (64)Cu-DOTA-biotin-SAv administration, with tumor-to-background ratios reaching a maximum at 3 h post-injection, i.e., 7 h post-PDT. Omitting the administration of biotinylated anxV or the avidin chase failed to provide a clear PET image, confirming that all three steps are essential for adequate visualization of apoptosis. Furthermore, differences in action mechanisms between photosensitizers that target tumor cells directly or via initial vascular stasis were clearly recognized through differences in tracer uptake patterns detecting early or delayed apoptosis.

CONCLUSION

This study demonstrates the efficacy of a three-step (64)Cu pretargeting procedure for PET imaging of apoptosis. Our data also confirm the usefulness of small animal PET to evaluate cancer treatment protocols.

Two-photon absorption of copper tetrasulfophthalocyanine induces phototoxicity towards Jurkat cells in vitro

The feasibility to induce oxygen-independent tumour cell kill by two-photon excitation of copper tetrasulfophthalocyanine (CuPcS4) was studied in Jurkat cells in vitro. Following incubation with CuPcS4 cells were transferred to a closed cuvette and irradiated with 532 nm pulsed-laser or 680 nm continuous-laser light to evaluate the effect of either two- or one-photon excitation, respectively. Cell survival was measured using MTT and Trypan Blue exclusion tests. Cell viability decreased 10-20% following two-photon excitation while one-photon illumination did not affect cell survival. These data confirm that two-photon excitation of CuPcS4 to the upper excited triplet state results in the formation of toxic species suggesting its potential use as a sensitizer for the photodynamic treatment of poorly oxygenated tumours.

A confocal microscopy study of the very early cellular response to oxidative stress induced by zinc phthalocyanine sensitization

Oxidative stress has been involved in several biological and pathological processes. Reactive oxygen species have been shown to play both beneficial and deleterious roles. The present work contributes to the understanding of the very early events of cellular response to oxidative stress. Oxidative stress was produced intracellularly by light activation of zinc phthalocyanine (ZnPc) at a light dose that did not lead to apoptosis or necrosis. Phthalocyanine was photoactivated using the 647-nm laser line of a confocal microscope through the objective lens causing oxidative stress and allowing observation of the evoked phenomena at the single cell level and in real time. Mitochondria membrane potential (DeltaPsi(m)), intracellular pH, calcium concentration, and generation of reactive oxygen species (ROS) were recorded using specific vital fluorescent probes and quantified by image processing and analysis. Subcellular localization of ZnPc was also studied in order to determine the primary and intermediate ROS target.