Sensitizers For Photodynamic Therapy Research Articles

Potential sensitizers for two-photon photodynamic therapy

Potential sensitizers for two-photon photodynamic therapy

Toward targeted photodynamic therapy

The sensitizers in common use for photodynamic therapy (PDT) are summarized, and approaches to the improvement of these outlined. Selectivity in the targeting of sensitizers to tumor cells and tissue is highly desirable, as is water solubility and prevention of aggregation. Some new free sensitizers are described, based upon thepyropheophorbide a(PPa) structure, and their photophysical properties, distribution in cells via confocal fluorescence microscopy, and cell kill properties described. A novel approach to targeting is to covalently attach such sensitizers to monoclonal antibody fragments, and recent work on the attachment ofpyropheophorbide ato such monoclonal antibody fragments is reviewed, with a demonstration of the increased efficiency of cell kill, and the treatment of a solid human tumor in a mouse model described. Finally, an alternative method of achieving selectivity based upon two-photon excitation (TPE) using porphyrin dimer sensitizers is reviewed, and the use of these to kill tumor cells is compared with the use of a commercially available PDT sensitizer (Visudyne). TPE of a porphyrin dimer sensitizer is shown to be capable of sealing blood vessels in a mouse model.

New advances in the study on the interaction of [Cr(phen)2(dppz)]3+ complex with biological models; association to transporting proteins

The present study reports a detailed investigation with the interaction of [Cr(phen)2(dppz)]3+ with serum albumins, the key protein for the transport of drugs in the blood plasma, which allows us to understand further the role of [Cr(phen)2(dppz)]3+ as sensitizer in Photodynamic Therapy (PDT).Chromium(III) complex [Cr(phen)2(dppz)]3+, (dppz = dipyridophenazine and phen=1,10-phenanthroline), where dppz is a planar bidentate ligand with an extended π system, has been found to bind strongly with bovine and human serum albumins (BSA and HSA) with an intrinsic binding constants, Kb, of (1.7±0.3)×105M−1 and (2.2±0.3)×105M−1 at 295K, respectively. The interactions of serum albumins with [Cr(phen)2(dppz)]3+ were assessed employing fluorescence spectroscopy, circular dichroism and UV–vis absorption spectroscopy. The serum albumins-[Cr(phen)2(dppz)]3+ interactions caused conformational changes with the loss of helical stability of the protein and local perturbation in the domain IIA binding pocket. The relative fluorescence intensity of the albumin (BSA or HSA) bound to the Cr(III) complex decreased, suggesting that perturbation around the Trp 214 residue took place. The analysis of the thermodynamic parameters ΔG, ΔH, ΔS indicated that the hydrophobic interactions played a major role in both BSA-Cr(III) and HSA-Cr(III) association processes. The binding distances and transfer efficiencies for BSA-Cr(III) and HSA-Cr(III) binding reactions were calculated according to the Föster theory of non-radiation energy transfer. All these experimental results suggests that [Cr(phen)2(dppz)]3+ binds to serum albumins, by which these proteins could act as carriers of this complex for further applications in PDT.

Application of a novel boronated porphyrin (H2OCP) as a dual sensitizer for both PDT and BNCT

Boronated porphyrins have emerged as promising dual sensitizers for use in both photodynamic therapy (PDT) and boron neutron capture therapy (BNCT), by virtue of their known tumor affinity, low cytotoxicity in dark conditions, and easy synthesis with high boron content. Octa-anionic 5,10,15,20-tetra[3,5-(nido-carboranylmethyl)phenyl] porphyrin (H₂OCP) is a boronated porphyrin having eight boron clusters linked to the porphyrin ring. To evaluate H₂OCP's applicability to both PDT and BNCT, we performed an in vitro and ex vivo study using F98 rat glioma cells. We examined the time-dependent cellular uptake of H₂OCP by measuring the boron concentration over time, and compared the cellular uptake/clearance of boron after exposure to H₂OCP in conjunction with boronophenylalanine (BPA) and sodium borocaptate (BSH), both of which are currently used in clinical BNCT studies. We evaluated the cytotoxicity of H₂OCP-mediated PDT using a colony-forming assay and assessed the tumorigenicity of the implantation of pre-treated cells using Kaplan-Meier survival curves. Fluorescence microscopy was also performed to evaluate the cellular uptake of H₂OCP. H₂OCP accumulated within cells to a greater extent than BPA/BSH, and H₂OCP was retained inside the cells to approximately the same extent as BSH. The cell-surviving fraction following laser irradiation (8 J/cm², 18 hours after exposure to 10 µg B/ml H₂OCP) was <0.05. The median survival times of the pre-treated cell-implanted rats were longer than those of the untreated group (P < 0.05). The fluorescence of H₂OCP was clearly demonstrated within the tumor cells by fluorescence microscopy. H₂OCP has been proven to be a promising photosensitizer for PDT. H₂OCP has also been proposed as a potentially effective replacement of BPA or BSH, or as a replacement of both BPA/BSH. Our study provides more evidence that H₂OCP could be an effective novel dual sensitizing agent for use in both PDT and BNCT.

Imidazole-modified porphyrin as a pH-responsive sensitizer for cancer photodynamic therapy

5,10,15,20-Tetrakis(N-(2-(1H-imidazol-4-yl)ethyl)benzamide)porphyrin produced twice as many singlet oxygen ((1)O(2)) molecules at pH 5.0 (quantum yield 0.53 ± 0.01) than at pH 7.4, whereas the (1)O(2) quenching rate was reduced by a factor of 2.5 for a pH change from 7.4 to 5.0.

Preface

Latest in a long series of successful conferences, the XXIIIrd IUPAC Symposium on Photochemistry was held in Ferrara, Italy on 11-16 July 2010. The conference venues were the Opera Theatre and the Estense Castle, in the historic center of the city. The contrasting mix of modern science and ancient environment was a special trait of the Ferrara symposium.The symposium was attended by over 500 delegates (including some 130 Ph.D. students) from 40 different countries. The scientific program consisted of 8 plenary lectures, 23 invited lectures, 97 selected oral presentations, as well as 354 posters. A highlight of the symposium was the presentation of the Porter Medal to Prof. David Phillips of Imperial College London, UK, in recognition of his outstanding contributions to several fields of photochemistry. The title of his lecture was “Targeted sensitizers for photodynamic therapy”.The wide variety of fields encompassed by modern photochemistry is reflected by the list of sessions held within the symposium: Electron and Energy Transfer, Molecular Switches and Machines, Organic Photochemistry, Inorganic Photochemistry, Photochromic Systems, Solar Energy, Supramolecular Photochemistry, Nanoparticles, Photocatalysis, Ultrafast Spectroscopy, Theoretical Photochemistry, Exciton and Charge Dynamics, Microscopy, Nanoscopic Systems, Singlet Oxygen and Phototherapy, Photobiology, Fluorescent Labels, Photoactive Materials, Applied Photochemistry, and Organized Media. Most of the topics discussed were characterized by a fertile combination of fundamental insight, advanced techniques, and practical application.This issue of Pure and Applied Chemistry collects a number of papers based on plenary and invited lectures delivered at the symposium. I hope that this collection will help illustrate modern photochemistry not only as a lively and exciting research field but also as a powerful resource toward the solution of important practical problems.Franco ScandolaConference Editor

A nonconjugated naphthalene derivative of meso-tetra-(3-hydroxy)-phenyl-porphyrin as a sensitizer for photodynamic therapy

Photodynamic Therapy (PDT) is a clinical procedure that is showing promising results in the treatment of certain types of cancer, including melanomas, oesophageal and retinal cancers [1-4]. The search for molecules suitable for use in PDT is a field of continuing interest. These molecules need to possess certain characteristics, including high affinity for tumour tissues and intense absorption in a region where biological tissues are relatively transparent. Porphyrin derivatives have become prime targets as sensitizers with potential to become good PDT agents, and have already been in use for over a decade in clinical PDT (ex: Foscan®). We report the synthesis and characterization of a meso-tetra-(3-hydroxy)-phenyl-porphyrin (T(OH)PP) derivative to which a naphthyl isocyanate group was attached, giving the meso-tetra-(phenoxy-3-carbonyl-1-amino-naphthyl)-porphyrin (T(NAF)PP (Figure ​(Figure11). Figure 1 The synthesized compound showed considerably enhanced photostability compared with the parent T(OH)PP (photodegradation quantum yield 4.65 × 10-4). The photosensitizer triplet state is normally considered to be essential for PDT, and to lead to the formation of cytotoxic oxygen species [5,6]. The lifetimes and quantum yields of the triplet state of T(NAF)PP were evaluated and presented typical values for this type of compounds. The quenching rate constant by molecular oxygen and singlet oxygen yield were also determined. The photodynamic effect in human carcinoma HT-29 cells was evaluated, and this novel porphyrin showed good properties as a sensitizer in photodynamic therapy with an in vitro cytotoxicity IC50 value of 6.80 μg mL-1 for 24 h incubation.

A New Nonconjugated Naphthalene Derivative ofMeso‐tetra‐(3‐hydroxy)‐phenyl‐porphyrin as a Potential Sensitizer for Photodynamic Therapy

A new 5,10,15,20-tetra-(phenoxy-3-carbonyl-1-amino-naphthyl)-porphyrin was prepared by an isocyanate condensation reaction and its photophysical properties fully evaluated, both in terms of photostability and singlet oxygen production. It shows considerably enhanced photostability when compared with the parent 5,10,15,20-tetra-(3-hydroxy-phenyl)-porphyrin, with the photodegradation quantum yields for T(NAF)PP and T(OH)PP being 4.65×10(-4) and 5.19×10(-3) , respectively. Its photodynamic effect in human carcinoma HT-29 cells was evaluated. The new porphyrin showed good properties as a sensitizer in photodynamic therapy with an in vitro cytotoxicity IC(50) value of 6.80μg mL(-1) for a 24h incubation. In addition to the potential of this compound, the synthetic route used provides possibilities of extension to a wide range of new sensitizers.

Porphyrin (TPP)–Polyvinylpyrrolidone (PVP)–Fullerene (C&lt;SUB&gt;60&lt;/SUB&gt;) Triad as Novel Sensitizer in Photodynamic Therapy

Porphyrin (TPP)–Polyvinylpyrrolidone (PVP)–Fullerene (C&lt;SUB&gt;60&lt;/SUB&gt;) Triad as Novel Sensitizer in Photodynamic Therapy

Study of the stabilization of zinc phthalocyanine in sol-gel TiO 2 for photodynamic therapy applications

Photodynamic therapy (PDT) has emerged as an alternative and promising noninvasive treatment for cancer. It is a two-step procedure that uses a combination of molecular oxygen, visible light, and photosensitizer (PS) agents; phthalocyanine (Pc) was supported over titanium oxide but has not yet been used for cell inactivation. Zinc phthalocyanine (ZnPc) molecules were incorporated into the porous network of titanium dioxide (TiO 2) using the sol-gel method. It was prepared from stock solutions of ZnPc and TiO 2. ZnPc-TiO 2 was tested with four cancer cell lines. The characterization of supported ZnPc showed that phthalocyanine is linked by the N-pyrrole to the support and is stable up to 250°C, leading to testing for PDT. The preferential localization in target organelles such as mitochondria or lysosomes could determine the cell death mechanism after PDT. The results suggest that nanoparticulated TiO 2 sensitized with ZnPc is an excellent candidate as sensitizer in PDT against cancer and infectious diseases. From the Clinical Editor Photodynamic therapy is a two-step procedure that uses a combination of molecular oxygen, visible light and photosensitizer agents as an alternative and promising non-invasive treatment for cancer. The results of this study suggest that nanoparticulated TiO 2 sensitized with ZnPc is an excellent photosensitizer candidate against cancer and infectious diseases.

Effect of disodiumN,N-dialanyl protoporphyrinate, diarginine protoporphyrinate and diarginineN,N-dialanyl protoporphyrinate on respiratory burst of human neutrophilsin vitro

The effect of three amino acid protoporphyrin IX (PPIX) derivatives evaluated as sensitizers in photodynamic therapy — disodium N,N -dialanyl protoporphyrinate ( PP(Ala)2Na2), diarginine protoporphyrinate (PPArg2) and diarginine N,N -dialanyl protoporphyrinate (PP(Ala)2Arg2) – non-irradiated and pre-irradiated with UV-A, on respiratory burst of non-stimulated and opsonized zymosan stimulated neutrophils was studied. A potential synergistic effect of diazepam (7-chloro-1-methyl-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one) was also examined. PP(Ala)2Na2showed strong pro-oxidant effect towards non-stimulated neutrophils, while PPArg2and PP(Ala)2Arg2revealed no significant effect. In the case of stimulated neutrophils all studied porphyrins showed antioxidant effect, although for PP(Ala)2Na2this effect was significantly weaker than that of PPArg2and PP(Ala)2Arg2. After pre-irradiation with UV-A (λ = 365 nm, fluence 2.0 J.cm-2, fluence rate 6.7 mW.cm-2) the antioxidant activity of all studied sensitizers towards non-stimulated granulocytes did not change significantly when compared to effects of non-irradiated porphyrins, while in the case of stimulated cells, only PPArg2caused significant decrease of respiratory burst. Non-irradiated diazepam showed significant antioxidant effect and enhanced antioxidant effect of all studied porphyrins towards stimulated neutrophils, while after UV-A pre-irradiation it revealed no significant antioxidant effect on non-stimulated and stimulated neutrophils, both alone and in combination with porphyrin sensitizers.

Photochemistry of Bacteriochlorophylls in Human Blood Plasma: 2. Reaction Mechanism Investigated by Product Analysis and Deuterium Isotope Effect

Transmetalated (Pd) bacteriochlorophyll derivatives are currently being clinically tested as sensitizers for photodynamic therapy. Protocols using short delay times between injection and irradiation generate interest in the photochemistry of these pigments in the blood. Using near-infrared irradiation where these pigments absorb strongly, we have studied the mechanism of photo-oxidation in two lipoprotein fractions, low- and high-density lipoproteins, derived from human blood plasma that preferentially accumulate these pigments (Dandler et al. [2009] Photochem. Photobiol., 85, in press). Using quenchers of reactive oxygen species, and chemical reporters, in particular peroxides generated from cholesterol as an inherent component of the lipoproteins, a Type II mechanism generating singlet oxygen has been demonstrated for Pd- and Zn-bacteriopheophorbides. In homogeneous systems, accelerated bleaching in D(2)O, compared with H(2)O, supports this mechanism. An unusual deuterium isotope effect was observed, by contrast, in heterogeneous amphiphilic-water systems. In the early phase, and under high oxygen concentrations, again a positive D-isotope effect is observed which later, in a second phase, is reversed to a negative D-isotope effect. The latter cannot be explained by heterogeneous pigment populations in the amphiphilic system; we, therefore, conclude a mechanistic switch, and discuss a possible mechanism.

Photochemistry of Bacteriochlorophylls in Human Blood Plasma: 1. Pigment Stability and Light‐induced Modifications of Lipoproteins

Transmetalated derivatives of bacteriochlorophyll are promising sensitizers in photodynamic therapy. Protocols using short delay times between injection and irradiation cause interest in the photochemistry of these pigments in the blood. Using near-infrared irradiation where these pigments absorb strongly, we have studied the photochemistry of Zn- and Pd-bacteriopheophorbide (WST09), and of the highly polar taurinated Pd-derivative, WST11, in isolated fractions of human blood plasma. The stability of all pigments is increased in blood plasma, compared with monomeric solutions. Pd-bacteriopheophorbide is much more stable than the other two derivatives. It also has a higher capacity for inducing reactive oxygen species, yet the consumption of oxygen is comparable. There is furthermore evidence for photobleaching under anoxic conditions. The generation of hydroperoxides (ROOH) is faster with Pd- than with Zn-complexes; the formation of endoperoxides (ROOR'), measured as thiobarbituric acid reactive substances, is comparable with the two central metals. Formation of both ROOH and ROOR' is increased in low-density lipoproteins (LDL) compared with high-density lipoproteins (HDL), which is probably related to the higher concentration of target molecules in the former. In HDL, extensive cross-linking is induced among the apolipoproteins; judged from the electrophoretic mobility of LDL and HDL particles, there is also a gross structural change. Photosensitized cross-linking is much less pronounced with high-density proteins.

Chiral bis‐Acetal Porphyrazines as Near‐infrared Optical Agents for Detection and Treatment of Cancer

We report the preparation of chiral oxygen atom-appended porphyrazines (pzs) as biomedical optical agents that absorb and emit in the near-IR wavelength range. These pzs take the form M[pz(A(4-n)B(n))], where "A" and "B" represent moieties appended to the pz's pyrrole entities, A = (2R,3R) 2,3-dimethyl-2,3-dimethoxy-1,4-diox-2-ene, B = beta,beta'-di-isopropoxybenzo, M is the incorporated metal ion (M = H(2), Zn), and n = 0, 1, 2 (-cis/-trans) and 3 (Scheme 1). When dissolved in polar media, H(2)[pz(trans-A(2)B(2))] 5a does not fluoresce and has a negligible quantum yield for singlet oxygen generation (capital EF, Cyrillic(Delta) = 0.074 +/- 0.001, methanol), as measured by the photo-oxidation of DMA. However, when sequestered in the nonpolar environment of a liposome, it displays strong NIR emission (lambda(max) = 705 nm, capital EF, Cyrillic(f) = 0.087) and an extremely high singlet oxygen quantum yield (capital EF, Cyrillic(Delta)-->1). Of this series, H(2)[pz(trans-A(2)B(2))] 5a is attractive as a potential optical probe, showing strongly fluorescent uptake by cells in culture, while 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide measurements of cell viability show no evidence of dark toxicity. This agent does show significant photoinduced toxicity suggesting that pzs such as 5a have promise as "theranostic" optical agents that can be visualized with fluorescence imaging while acting as a sensitizer for photodynamic therapy.

Squaraine Compounds: Tailored Design and Synthesis towards a Variety of Material Science Applications

AbstractThe interest in squaraine compounds, a relatively old class of dyes, has been recently renewed due to their potential usefulness in a large number of technologically relevant fields such as two‐photon absorbing materials, field‐effect transistors, solar cells, NIR‐emitting fluorescent probes and sensitizers for photodynamic therapy. Aim of the present review is to summarize the most convenient strategies for squaraines and polysquaraines syntheses and to discuss the design strategies enabling for the preparation of squaraines having properties relevant for a given material application. In particular, in the first section of the review we will describe the various synthetic approaches for the preparation of squaraine and polysquaraine derivatives. The second section will focus on squaraines applications. We will describe in detail the use of squaraines in bioimaging and photodynamic therapy. Within the topic of bio‐related applications we will also discuss the applications of squaraines as histological probes. Within the NLO‐related applications, we will focus on squaraine‐based electro‐optic and two‐photon absorbing materials. Dealing with photoconduction related applications, we will discuss the most recent applications of squaraine compounds in various kinds of devices such as solar cells, hybrid solar cells and NIR‐responsive photodetectors. In all of the cases we will mainly focus on structure–property relationships highlighting the role of the active molecule design in the final device performances.

Evaluation of the oxidative activity of some free base porphyrins by a chemiluminescence method

Due to their spectral characteristics, phototoxicity and high affinity for tumour tissues, porphyrins and their derivatives are widely used in modern medicine as contrast agents for cancer diagnostics and as sensitizers in photodynamic therapy, where they kill tumours via enhancement of tumour oxidative stress. The aim of this work was to simulate in vitro the effects caused by oxidation of two free base porphyrins, 5,10,15,20-tetraphenylporphyrin (TPP) and 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMOPP). The kinetic study was monitored using spectral techniques and chemiluminescence. The effect of both porphyrins on an oxidation process was evidenced using the chemiluminescent system, luminal-hydrogen peroxide, in a phosphate buffer at pH 7. It was found that at low concentration, TPP exerts the anti-oxidative effect in the employed chemiluminescent system, while at higher concentrations, its effect is pro-oxidative. TMOPP exerts a pro-oxidant effect, which was more pronounced than TPP. The results are discussed with respect to oxidative stress.

Greatly enhanced binding of a cationic porphyrin towards bovine serum albumin by cucurbit[8]uril

Binding affinity towards serum albumin and intracellular proteins is of importance for a photodynamic therapy (PDT) sensitizer to selectively localize in tumours and efficiently induce cell death. In this paper, it was found that cucurbit[8]uril (CB8) can greatly improve the binding affinity of 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP), a promising PDT photosensitizer, towards bovine serum albumin (BSA). Absorption, fluorescence emission, (1)H NMR, dynamic light scattering, atomic force microscope, as well as protein photocleavage measurements suggest that the binding enhancement originates from the formation of a ternary complex of CB8·TMPyP·tryptophan residues. This finding opens up a new approach for the development of more efficient PDT agents.

Natural Chlorins Modified with Cholesterol Moiety. Synthesis, Characteristics, Copper Complexes, and Entrapping in Phospholipid Vesicles

The chemical synthesis and characteristics of two natural chlorins modified with cholesterol moieties: 17’’[(cholest5-en)-3β-yloxyethoxycarbamoyl]pyropheophorbide a and 13’[(cholest-5-en)-3b-yloxyethoxycarbamoyl]chlorin are presented, as well as the preparation of the related copper complexes. Both conjugates obtained, as well as their copper complexes, may be simply incorporated in phosphatidylcholine vesicles. Being entrapping in vesicles all these conjugates are considered to be novel potential sensitizers for photodynamic therapy, while copper complexes of conjugates are considered to be spin probes for membrane studies, providing important structural and dynamical information.

In vitro evaluation of Radachlorin® sensitizer for photodynamic therapy

This paper reports the evaluation of a new photosensitizer, Radachlorin in comparison with one of its well known components but used solely, Chlorin e(6). The photodynamic properties and cell uptake and localisation of the two drugs were compared. In vitro studies were conducted on human adenocarcinoma cells (HT29) and lung carcinoma cell line (A549). Both dyes showed an absorption maximum between 640 and 650 nm, but those absorption peaks are enhanced by interactions with serum, with a shifted maximum at 661 and 664 nm, and much higher absorbance. As Radachlorin is constituted of different products and as photoreactivity is dependent on absorbed light energy, we chose to adapt concentrations so that both drugs had the same absorption at the irradiation wavelength (664 nm) for photoreactivity tests, and express concentrations in optical density at 664 nm. The capacity of the two drugs to generate Reactive Oxygen Species was identical, but on HT29 cells, Radachlorin reaches its optimal LD50 sooner than Chlorin e(6). Radachlorin LD50 on HT29 cells was 0.0251 OD(664 nm) after 2 h and 0.0672 OD(664 nm) for Chlorin e(6) for a 20 J cm(-2) irradiation. Radachlorin gave very similar results on A549 cells, LD50 being 0.05 for 5 J irradiation, and 0.026 for 10 and 20 J cm(-2). Pharmacokinetics using fluorescence showed that, even if Radachlorin quickly crossed HT29 (a human colonic cancer line) cell membrane, cellular distribution evolved from a diffuse cytoplasmic repartition 1 hour after Radachlorin addition to a delimited localisation into organelles all around the nucleus. Radachlorin intracellular fluorescence decreased after 4 h, whereas we did not observe a decrease of Chlorin e(6) intracellular fluorescence for times up to 24 h. In both case, a quick decline was observed as soon as the culture medium was replaced with a drug-free one. Radachlorin appears to be an excellent photosensitizer, with similar phototoxicity to Chlorin e(6) on cell cultures, but with quicker kinetics, which could be an improvement if confirmed on further in vivo studies.

Inhibition of Aggregation of [Pd]-Bacteriochlorophyllides in Mesoporous Silica

Aggregation is a major factor affecting the photophysical properties of chlorophylls. For two [Pd]-bacteriochlorophyll derivatives that are currently under clinical testing as sensitizers for photodynamic therapy, aggregation control in aqueous solution has been studied with folded-sheet mesoporous silica (FSM) of different pore sizes (20, 45, 83 A) and with detergent (Triton X-100). With both the moderately polar WST09 and the highly polar WST11, no pigment oligomers were formed in FSM, and the monomer-dimer equilibrium was shifted toward the monomer with decreasing pore diameter.