Tetracationic Porphyrin Research Articles

An Amphiphilic Bisporphyrin and Its YbIII Complex: Development of a Bifunctional Photodynamic Therapeutic and Near‐Infrared Tumor‐Imaging Agent

See and treat: An amphiphilic bisporphyrin and its YbIII complex Yb⋅1 are characterized by an appropriate hydrophobicity/hydrophilicity balance for membrane transport. Their cellular uptake by a rat tumor-cell model is ten times higher than that of the parent tetracationic porphyrin, and their activity as photodynamic therapeutics is correspondingly stronger. The near-IR-luminescence of Yb⋅1 is potentially useful for tumor imaging. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2268/2008/z700767_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Proof of Partial Flattening of Meso Substituents in Tetracationic Porphyrin at a Mica/Solution Interface

Abstract A free base tetracationic porphyrin (TMPyP) was adsorbed at a mica/aqueous solution interface. Atomic force microscopy (AFM) in liquid revealed that the porphyrin rings lie flat on the mica surface with their meso substituents partially rotated toward planarity. Optical waveguide spectroscopy elucidated a bathochromic shift of the Soret band, suggesting extension of π-conjugation by partial inclusion of pyridinium rings.

Interaction and photodynamic activity of cationic porphyrin derivatives bearing different patterns of charge distribution with GMP and DNA

The interaction of amphiphilic cationic porphyrins, containing different patterns of meso-substitution by 4-(3- N, N, N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, with guanosine 5′-monophosphate (GMP) and calf thymus DNA have been studied by optical methods in phosphate buffer solution. The properties of these synthetic porphyrins were compared with those of representative standard of anionic 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS 4 4−) and cationic 5,10,15,20-tetra(4- N, N, N-trimethylammonium phenyl)porphyrin (TMAP 4+). Stable complexes with GMP were found for cationic porphyrins, except for monocationic AB 3 +. The binding constant ( K GMP ∼ 10 4 M −1) follows the order: A 3B 3+ ∼ ABAB 2+ > A 4 4+ ∼ TMAP 4+. Also, interaction with DNA was observed for all evaluated cationic porphyrins. For these related cationic porphyrins, the binding constant ( K DNA ∼ 10 5 M −1) increases with the number of cationic charges. On the other hand, the photodynamic activity of porphyrins was analyzed in solution of GMP and DNA. Monocationic AB 3 + is a less effective sensitizer to oxidize GMP in comparison with the other cationic porphyrins, in agreement with the lack of detected interaction with this nucleotide. The electrophoretic analysis of DNA indicates that photocleavage takes place when the samples are exposed to photoexcited tricationic and tetracationic porphyrins. In the presence of sodium azide the DNA decomposition was diminished. Also, reduction in the DNA photocleavage was observed under anoxic condition, indicating that oxygen is essential for DNA photocleavage sensitized by these cationic porphyrins. In addition, an increase in DNA degradation was not observed in deuteriated water. Therefore, an important contribution of type I photoreaction processes could be occurring in the DNA photodamage sensitized by these cationic porphyrins. These results provide a better understanding of the characteristics needed for sensitizers to produce efficient DNA photocleavage.

Sewage bacteriophage photoinactivation by cationic porphyrins: a study of charge effect

Photodynamic therapy has been used to inactivate microorganisms through the use of targeted photosensitizers. Recently the inactivation of bacteria in residual waters has been reported, but nothing is known about photoinactivation of environmental bacteriophages, which are often used as indicators of human enteric viruses. In this study we tested the effect of six cationic porphyrin derivatives with two to four charges on the photoinactivation of a sewage bacteriophage. A phage suspension of 5 x 10(7) PFU mL(-1) was exposed to white light (40 W m(-2)), during 270 min, at three photosensitizer concentrations (0.5, 1.0 and 5.0 microM). Tetra- and tricationic porphyrins inactivated the T4-like sewage phage to the limits of detection, but dicationic porphyrins did not lead to a significant decrease in phage viability. At the highest photosensitizer concentration (5.0 microM), the phage was completely inactivated (>99.9999% of inactivation, reduction of 7.2 log) after 270 min by the tetracationic porphyrin. Two of the tricationic derivatives also led to phage inactivation to the limit of detection. The rate of bacteriophage photoinactivation and the efficiency of the photosensitizer appeared to vary with the charge and with the substituents in the meso-positions of the porphyrin macrocycle. Tetra- and tricationic porphyrins can, therefore, be used as a new method for inactivating sewage bacteriophages that are frequently used as human enteric virus indicators. The complete inactivation of viruses with low light intensity means that this methodology can be used even on cloudy days and during winter, opening the possibility to develop new technologies for wastewater treatment.

Chiral memory: Induction, amplification, and switching in porphyrin assemblies

The interaction between the tetra-anionic porphyrin H2TPPS and its copper derivative, CuTPPS, with the tetra-cationic porphyrin H2T4 and its copper derivative, CuT4, leads, in aqueous solution, to the formation of remarkably stable and kinetically inert heteroaggregates. The aggregation process is under hierarchic control and, in the presence of a suitable chiral mold, leads to the formation of chiral porphyrin heteroassemblies as stable and inert as the achiral ones. Because of these properties, the chirality of the porphyrin "imprinted" heteroaggregates not only survives the disruption of the template, but also to its complete removal from the solution. Notably, the template-free chiral porphyrin system is an excellent mold for its own self-replication. The relevant characteristics of these chiral heteroaggregates together with the knowledge of the forces that guide the aggregation processes permitted us to design a new but similar system. This system not only is able to store chiral information, but also is capable to release and restore it reversibly, in a cyclic manner. This has been achieved by modulating the charges carried by one of the two coupled porphyrins through protonation under various pH conditions. The role of the central metal ion and the template-free chiral structure of the CuT4-H2TPPS heteroaggregate, determined through EDXD analysis, are also presented.

Dichroic Measurements on Dicationic and Tetracationic Porphyrins on Clay Surfaces with Visible-Light-Attenuated Total Reflectance

Abstract Complexes formed with synthetic clay minerals and dicationic and tetracationic porphyrins were prepared. The Soret bands of the multicationic porphyrins shifted to longer wavelength upon the formation of a complex with clay. The clay sheets themselves and the porphyrin molecules on the clay surface were examined by use of atomic force microscopy (AFM) and polarized visible-light-attenuated total reflectance (ATR) spectroscopy (PV-ATR) with a waveguide system. The flat adsorption of the clay sheets on the glass substrates was confirmed by AFM. A theoretical treatment of the analysis by ATR spectroscopy was derived. The orientations of the multicationic porphyrin molecules on the clay sheets in water turned out to be nearly parallel (<5°) to the clay surface, based on the PV-ATR analysis.

Spectral study on the molecular orientation of a tetracationic porphyrin dye on the surface of layered silicates

Abstract Tetracationic porphyrin dyes TMPyP and ZnPyP were intercalated into hydrophobized layered silicate films of three smectites. The smectites represented the layered silicate specimens of high (Fluorohectorite, Corning; FHT), medium (Kunipia F montmorillonite; KF) and low layer charge (Laponite, Laporte; LAP). The molecular orientations of the dye cations were studied by means of linearly-polarized ultraviolet-visible (UV-VIS) spectroscopy. The spectral analysis and consequent calculations of tilting angles of the transition moments at the wavelengths of Soret band transitions were in the range of 25°-35°. The determined angles indicated molecular orientation of the dye cations being almost parallel to the surface of the silicates. Slightly higher values (above 35°), determined for a FHT film, indicated either a slightly tilted orientation of the dye cations or the change of molecular comformation after the intercalation of the dye.

J-Aggregation of a Water-Soluble Tetracationic Porphyrin in Mixed LB Films with a Calix[8]arene Carboxylic Acid Derivative

The molecular organization of a mixed film, containing a water-soluble tetracationic porphyrin (TMPyP) and a p-tert-butyl calix[8]arene octacarboxylic acid derivative (C8A), at the air-water interface and on a solid support (LB film), has been investigated. Although the TMPyP aggregation was not detected at the air-water interface, TMPyP J-aggregates have been found in the LB films (Y-type). Unlike tetraanionic porphyrins, for example TSPP, the TMPyP J-aggregates are not induced by a zwitterion formation. The TMPyP J-aggregation is a result of a "double comb" configuration, where porphyrins from opposite layers are interwoven in a linear infinite J-aggregate. Our results confirm that TMPyP molecules tend to self-aggregate strongly, provided the electrostatic repulsions of their peripheral groups are cancelled by the anionic groups of the C8A matrix.

Potential of cationic porphyrins for photodynamic treatment of cutaneous Leishmaniasis

Four tetracationic porphyrins have been investigated for their ability to photo-inactivate Leishmania major promastigotes. Parallel photocytotoxicity assays against keratinocytes and macrophages show significant differences in activity between the microorganism and mammalian cells. Results suggest that it may be possible to photodynamically inactivate macrophages infected with Leishmania and the promastigote form of the microorganism, while minimising damage to surrounding tissue.

Antibacterial activity of tetraaryl-porphyrin photosensitizers: An in vitro study on Gram negative and Gram positive bacteria

Background Photodynamic therapy exploits visible light and photosensitizers to inactivate cells and this methodology is currently used for the treatment of several types of malignancy. Although various tumours are successfully treated with PSs and light, the application on microorganisms (photodynamic antimicrobial chemotherapy) has not yet found specific medical applications and still remains an open field of fundamental research. Purpose The assessment of the effect of a panel of seven tetraaryl-porphyrins, two commercial (PS 1 and 2) and five synthetic (PS 3– 7) in in vitro experiments against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Methods Three of the new photosensitizers (PS 3, 4 and 5) are tetracationic porphyrins and were prepared by N-alkylation of 5,10,15,20-tetra-4-pyridylporphyrin with a large excess of different benzyl chlorides; compound 7 is a dicationic porphyrin and was obtained in a similar way using a lower excess of 4-methoxybenzyl chloride. The neutral porphyrin (PS 6) was previously described. Dose–response curves were obtained titrating the survivors of cell suspensions (10 8 cfu/ml) exposed to the PSs and irradiated with visible light (total fluence rate 266 J/cm 2). Results The non ionic porphyrin 6 was the least active PS against all the tested bacteria. Cationic PSs 3, 4, 5 and 7 were more active than the commercial 1 and 2. The Gram positive S. aureus was more sensitive to all the PSs than the Gram negative E. coli and P. aeruginosa, the latter being the more resistant one. Compound 7 was found particularly efficient against P. aeruginosa, causing a 7 log units reduction of survivors at a concentration of 8 μM. Conclusions The reported results confirm that the presence of positively charged groups on porphyrin frame is fundamental for PSs antibacterial activity, however our data suggest that a moderate degree of lipophilicity, achievable by the introduction of aromatic hydrocarbon side chains on the pyridyl moieties, may improve PSs efficiency. Furthermore dicationic porphyrin 7 seems to be more efficient than the corresponding tetracationic derivatives thus emphasizing an interesting feature involved in the PSs activity.

The Orientation Control of Dicationic Porphyrins on Clay Surfaces by Solvent Polarity

Abstract The orientations of cationic porphyrins on a clay surface were found to be successfully controlled by solvent polarity. The orientational change was directly observed with the interface spectrometer equipped with a quartz waveguide system. Tetracationic porphyrins on the clay surface in water are oriented with the plane of the rings parallel to the silicate layer, while in the case of dicationic porphyrins (cis-type), the porphyrin plane stood up against the clay surface on addition of less polar water-miscible solvent.

Clay-Porphyrin Systems: Spectroscopic Evidence of TMPyP Protonation, non-Planar Distortion and Meso Substituent Rotation

AbstractThe interaction of the water-soluble 5,10,15,20-tetrakis(l -methyl-4-pyridyl)-21H,23H-porphine (TMPyP) with different 2:1 phyllosilicates was examined by Raman and UV-visible spectroscopies. The clay samples were saturated with the tetracationic porphyrin and isolated from the aqueous suspension. A red shift of the Soret band was observed for all the clay-TMPyP systems in the order vermiculite < Laponite < mica-smectite (Syn-1) < montmorillonite (SWy-2). Furthermore, three components were observed for the Soret band (at ~425, 455 and 488 nm). Raman spectra of the isolated solids excited at 457.9 nm, 488.0 nm and 514.5 nm suggest the occurrence of porphyrin protonation, nonplanar distortion and rotation of the meso substituent. Based on the vibrational data, an acidity scale was proposed for the clays: vermiculite < Laponite < SWy-2 < Syn-1. The relative contribution of the protonated spectra is larger at 457.9 nm than at 488.0 nm, suggesting that the peak at 455 nm corresponds to the protonated species. In Laponite, the relative intensity of the meso substituent band at ~1635 cm-1 indicates that the dihedral angle formed between the porphyrin and the methyl-pyridyl rings decreased in the non-protonated porphyrin as a consequence of intercalation. Raman data are thus consistent with the presence of at least two porphyrin species in resonance at 457.9 nm: the protonated and a more planar non-protonated porphyrin. At 488.0 nm the number of enhanced modes increases suggesting a decrease in the porphyrin symmetry. This allows assignment of the absorption band centered at 488 nm to a non-planar porphyrin conformation.

Supramolecular design of a porphyrin–[60]fullerene photocurrent generation system on a DNA scaffold fabricated by a conjugate polymer film

DNA which binds monocationic [60]fullerene ( 1 ) and tetracationic porphyrin (TMPyP) was readily fabricated by electrochemical oxidative polymerization of 3.4-ethylenedioxythiophene (EDOT) and the resultant poly(EDOT) composite was deposited on an ITO electrode as a stable thin film. Spectral and CV analyses established that one 1 and one TMPyP are bound per 57 nucleobase units, that is, every three pitches of DNA. Photoirradiation of this 1 /TMPyP/DNA-poly(EDOT) film generated a photocurrent in 3.8% quantum yield, which was much higher than those obtained from 1 /DNA and TMPyP/DNA systems. One can conclude, therefore that the photoexcited energy of TMPyP is transferred to 1 , which is collected by the electron-conducting poly(EDOT) film. The present paper shows that DNA is useful as a scaffold to arrange redox-active couples in a one-dimensional matrix.

Photoinactivation of Escherichia coli using 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 ( ϕ F) of 0.10, 0.06 and 0.08 were calculated for porphyrins 1, 2 and 3, respectively. The singlet molecular oxygen, O 2( 1Δ g), 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 °C for 30 min in dark. In both procedures, a higher photoinactivation of cells (>99.999%) was found for cells treated with 10 μM 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.

Transfer, Memory and Amplification of Chirality in Porphyrin Aggregates

The aggregation process of the tetraanionic H2TPPS and the tetracationic CuT4 porphyrins leads, in aqueous solution and in the presence of a suitable chiral template, to the formation of remarkably stable and kinetically inert chiral porphyrin heteroassemblies. These properties enable the aggregates to survive template chirality disruption and its complete removal from the solution, maintaining unaltered the imprinted chiral structure. The free-template “imprinted” porphyrin aggregate is an excellent mold for the amplification of its own structure.

Assembly of Positively Charged Porphyrins Driven by Metal Ions: A Novel Polymeric Arrangement of Cationic Metalloporphyrin

Crystallization and crystal structure analysis of chlorohydrates of either tri- or tetracationic copper porphyrins, namely copper(5,10,15-tris(N-methyl-pyridinium-4-yl)-20-pyridine-porphyrinato) (1) and copper(5,10,15,20-tetrakis(N-methyl-pyridinium-4-yl)-porphyrinato), respectively, have been performed. Two crystalline forms, 2 and 3, of the latter have been obtained under different preparation conditions. A novel kind of slipped stack chains of these cationic porphyrins has been detected. The pronounced saddle conformation of the porphyrin reveals pi-like interactions between the peripheral pyrrole Cb-Cb- "double bond" and the metal center. DFT calculations on the isolated porphyrins clearly show the HOMO orbitals with the correct topology to yield a bonding interaction among the stacked porphyrin units. To our knowledge, a slipped stack chain of positively charged porphyrins has never been previously reported, if the arrangement of faced units of monocationic metalloporphyrins or phthalocyanins is excluded.

Meso-substituted tetra-cationic porphyrins photosensitize the death of human fibrosarcoma cells via lysosomal targeting

In this paper we present a study on the intracellular localisation and the efficiency of cell photoinactivation of a series of derivatives of 5,10,15,20-tetrakis-(4- N-methylpyridyl)-porphine (C1), whose degree of lipophilicity was varied through replacement of one methyl group with an alkyl chain of various length. Human HT1080 fibrosarcoma cells exposed to the various C1 derivatives (0.25 μM) for 24 h and irradiated with increasing doses of red-light (0.45–27 J/cm 2) were inactivated with different efficiencies. The efficiency of cell photoinactivation increased with the increasing length of the hydrocarbon tail and lipophilicity and correlated with the efficiency of the porphyrin accumulation into the cells. Despite the presence of positive charges, these porphyrins did localise rather selectively in lysosomes while mitochondrial localisation was not evident, as demonstrated by fluorescence microscopy studies. Studies on isolated mitochondria provided evidence that the porphyrin uptake and distribution in these organelles were not modulated by the transmembrane potential but were exclusively controlled by partitioning phenomena which might have prevented mitochondria localization in whole cells. Our findings demonstrated that these porphyrins entered the cells through the endocytotic pathway and were transported to lysosomes whose pH increased rapidly upon irradiation. Lysosomal damage did not cause any intracellular redistribution of the porphyrin and represented the primary event causing cell death, very likely via necrosis.

The ‘size matching rule’ in di-, tri-, and tetra-cationic charged porphyrin/synthetic clay complexes: effect of the inter-charge distance and the number of charged sites

Novel inorganic/organic hybrids formed from cationic porphyrins and synthetic clay were investigated. Di-, tri- and tetra-cationic charged porphyrins with different distances between adjacent cationic sites within the molecules were incorporated into the hybrids with synthetic clay. When tetra-cationic porphyrins were used, in which distances between adjacent cation sites were 1.05 and 1.31 nm, the porphyrin molecules adsorb on the clay surfaces with high density, neutralizing all of the negative charges of the clay surface, i.e. 100% adsorption vs. the cation exchange capacity (CEC), without aggregation, even though it is generally difficult to control or suppress the aggregation of organic molecules on inorganic surfaces. The mean center-to-center distance between porphyrin molecules in the hybrids was estimated to be 2.4 nm. When Δ l (the difference between the inter-cationic charge distance in the porphyrin molecule and the inter-anionic charge distance on the clay surface) was larger than ca. 0.2 nm, the porphyrin molecules adsorbed in amounts smaller than 100% vs. CEC. In the cases of di- and tri-cationic charged porphyrins, similar adsorption behavior was observed. The formation of these unique hybrids was rationalized by a size-matching of distances between the charged sites in the porphyrin molecule and on the clay surface (‘size-matching rule’).

Surfaces designed for charge reversal.

We have created surfaces which switch from cationic at pH < 3 to anionic at pH > 5, by attaching aminodicarboxylic acid units to silica and gold substrates. Charge reversal was demonstrated by monitoring the adsorption of cationic dyes (methylene blue and a tetracationic porphyrin) and an anionic sulfonated porphyrin, at a range of pH using UV-vis absorption and reflection spectroscopy. The cationic dyes bind under neutral conditions (pH 5-7) and are released at pH 1-4, whereas the anionic dye binds under acidic conditions (pH 1-4) and is released at pH 5-7. Gold surfaces were functionalized with two different amphoteric disulfides with short (CH(2))(2) and long (CH(2))(10)CONH(CH(2))(6) linkers; the longer disulfide gave surfaces exhibiting charge reversal in a narrower pH range. Adsorption is much faster on the functionalized gold (t(1/2) = 62 s) than on functionalized silica (t(1/2) = 6900 s), but the final extents of coverage on both surface are similar, for a given dye at a given pH, with maximal coverages of around 2 molecules nm(-)(2). These charge-reversal processes are reversible and can be repeatedly cycled by changing the pH. We have also created surfaces which undergo irreversible proton-triggered charge switching, using a carbamate-linked thiol carboxylic acid which cleaves in acid. These surfaces are versatile new tools for controlling electrostatic self-assembly at surfaces.

Thin Films of a Tetracationic Porphyrin

Langmuir–Blodgett films of the tetracationic porphyrin tetrakis(octadecyl-4-pyridinium)porphinatozinc(II) bromide transferred from subphases containing different salts were studied using X-ray photoelectron spectroscopy (XPS) and X-ray reflectometry. In contrast to previous results at the air/water interface, we found that the porphyrin adopted a fixed conformation at the air/solid interface regardless of composition of the subphase or whether the films were transferred above or below the primary phase transition. This conformation was assigned to the formation of an interdigitated bilayer structure.