Sensitizers For Photodynamic Therapy Research Articles

Assessing of integration of ionizing radiation with Radachlorin-PDT on MCF-7 breast cancer cell treatment.

This study was undertaken to examine the effects of Radachlorin as a sensitizer in both photodynamic and radiation therapy on MCF-7 human breast cancer cell line. Another purpose was to assess the effectiveness of radiotherapy in combination with photodynamic therapy. The cells were incubated with Radachlorin and then exposed, in the independent treatment groups, to red visible light (660 nm), at two energy densities (6 and 12 j/cm(^)2) and 2-Gy X-ray ionizing radiation. In addition, combination effects of these modalities were evaluated. The percentage of the cell survival was investigated using the MTT assay and also survival fraction was evaluated by colony assay. The results demonstrated Radachlorin had no significant cytotoxic effects alone. However, it had a strong cytotoxic effect in the presence of light on MCF-7 cells. Light and Radachlorin reduced the percent of cell survival to 47 %. Despite Radachlorin could not act as a radiosensitizer, using integration of Radachlorin with radiotherapy and photodynamic therapy resulted in a significant cell death in comparison to the control group. Colony assay revealed the synergistic effect of this combined therapy with reduction of survival fraction to 0.03. MTT showed that the viability of breast cancer cells was reduced to 28 % by this integration therapy. Combination of radiation and photodynamic therapy could be a worthwhile approach for breast cancer treatment. It appears that we can reduce the adverse effects of treatments without reducing the efficacy of therapy.

β-Functionalized Push–Pull opp-Dibenzoporphyrins

The synthesis of a series of β-functionalized push-pull dibenzoporphyrins was realized. These porphyrins display subtle push-pull effects, demonstrating the exceptional tunability of their electronic and electrochemical properties. The UV-vis spectra of these porphyrins show unique absorption patterns with shouldered Soret bands and extra absorptions in the Q-band region. Stronger electron-withdrawing groups display more significant bathochromic shifts of the Soret bands. The fluorescence spectra of these porphyrins show strong near-IR emission bands (600-850 nm). In particular, fluorescence quenching effect was observed for pyridyl carrying push-pull porphyrin 4c in the presence of an acid. TFA titration study of 4c using UV-vis and fluorescence spectroscopy reveals that the fluorescence quenching can be mainly attributed to the protonation of the pyridyl groups of 4c. The versatile synthetic methods developed in this work may open a door to access a large number of functionalized organic materials that are currently unavailable. The structure-property studies provided in this work may provide useful guidelines for the design of new generations of materials in dye-sensitized solar cells, in nonlinear optical applications, as fluorescence probes, as well as sensitizers for photodynamic therapy.

WITHDRAWN: Over-expression 5-aminolevulinic acid synthase 2 in nonerythroid cell may causes protoporphyrin IX accumulation

Protoporphyrin IX (PpIX) has been used as an efficient sensitizer in photodynamic diagnose, photodynamic therapy, and sonodynamic therapy. The level of PpIX is very important for diagnose or therapy effects. 5-aminolevulinic acid synthase 2 (ALAS2) is the key enzyme upstream of PpIX synthesis. To increase PpIXaccumulation, ALAS2 overexppression transgenic mice were generated. Plasmid containing alas2 gene was transfected in colonic carcinoma cell lines. Both in tissues of transgenic mice and in colonic carcinoma cells, the amount of PpIXaccumulation did increased. At the meanwhile, level of heme, which down stream of PpIX had not been changed. Overexpression ALAS2 in nonerythriod cells may become a novel approach to cause PpIX accumulation.

Synthesis and photophysicochemical studies of poly(ethylene glycol) conjugated symmetrical and asymmetrical zinc phthalocyanines

Synthesis and characterization of poly(ethylene glycol) conjugated symmetrical and asymmetrical zinc phthalocyanines (ZnPcs) is described. Copper (I) catalyzed azide-alkyne cycloaddition (CuAAC) click reaction between azide functional methoxypoly(ethylene glycol) (mPEG-N3) and tetra terminal alkynyl substituted ZnPc yields star polymer with ZnPc core. Furthermore, CuAAC click reaction between asymmetrically terminal alkynyl substituted zinc phthalocyanine (aZnPc) and mPEG-N3 yields aZnPc end functionalized PEG. Spectral, photophysical (fluorescence quantum yield), photochemical (singlet oxygen (ΦΔ), and photodegradation quantum yield (Φd) properties of the symmetrically, and asymmetrically PEGylated ZnPcs are investigated to be used as sensitizers in photodynamic therapy (PDT). The quantum yield values of fluorescence (ΦF) and singlet oxygen generation (ΦΔ) for water soluble symmetrically PEGylated ZnPc in aqueous solution are calculated as 0.01 and 0.14 respectively, suggesting its potential as photosensitizer in PDT treatment.

Developments in PDT Sensitizers for Increased Selectivity and Singlet Oxygen Production.

Photodynamic therapy (PDT) is a minimally-invasive procedure that has been clinically approved for treating certain types of cancers. This procedure takes advantage of the cytotoxic activity of singlet oxygen (1O2) and other reactive oxygen species (ROS) produced by visible and NIR light irradiation of dye sensitizers following their accumulation in malignant cells. The main two concerns associated with certain clinically-used PDT sensitizers that have been influencing research in this arena are low selectivity toward malignant cells and low levels of 1O2 production in aqueous media. Solving the selectivity issue would compensate for photosensitizer concerns such as dark toxicity and aggregation in aqueous media. One main approach to enhancing dye selectivity involves taking advantage of key methods used in pharmaceutical drug delivery. This approach lies at the heart of the recent developments in PDT research and is a point of emphasis in the present review. Of particular interest has been the development of polymeric micelles as nanoparticles for delivering hydrophobic (lipophilic) and amphiphilic photosensitizers to the target cells. This review also covers methods employed to increase 1O2 production efficiency, including the design of two-photon absorbing sensitizers and triplet forming cyclometalated Ir(III) complexes.

Tetrakis(p-Carboranylthio-Tetrafluorophenyl)Chlorin (TPFC): Application for Photodynamic Therapy and Boron Neutron Capture Therapy

Carboranyl-containing chlorins 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 their strong absorptions in the red region of the optical spectrum. Tetrakis(p-carboranylthio-tetrafluorophenyl)chlorin (TPFC) is a new synthetic carboranyl-containing chlorin of high boron content (24% by weight). To evaluate TPFC's applicability as sensitizer for both PDT and BNCT, we performed an in vitro and in vivo study using F98 rat glioma cells and F98 rat glioma-bearing brain tumor models. For the in vivo BNCT study, we used boronophenylalanine (BPA), which is currently used in clinical BNCT studies, via intravenous administration (i.v.) and/or used TPFC via convection-enhanced delivery (CED), a method for local drug infusion directly into the brain. In the in vitro PDT study, the cell surviving fraction following laser irradiation (9 J/cm(2) ) was 0.035 whereas in the in vitro BNCT study, the cell surviving fraction following neutron irradiation (thermal neutron = 1.73 × 10(12) n/cm(2) ) was 0.04. In the in vivo BNCT study, the median survival time following concomitant administration of BPA (i.v.) and TPFC (CED) was 42 days (95% confidence interval; 37-43 days).

A luminescent poly(amidoamine)-iridium complex as a new singlet-oxygen sensitizer for photodynamic therapy.

A polymer complex (1P) was synthesized by binding bis(cyclometalated) Ir(ppy)2(+) fragments (ppy = 2-phenylpyridyl) to phenanthroline (phen) pendants of a poly(amidoamine) copolymer (PhenISA, in which the phen pendants involved ∼6% of the repeating units). The corresponding molecular complex [Ir(ppy)2(bap)](+) (1M, bap = 4-(butyl-4-amino)-1,10-phenanthroline) was also prepared for comparison. In water solution 1P gives nanoaggregates with a hydrodynamic diameter of 30 nm in which the lipophilic metal centers are presumed to be segregated within polymer tasks to reduce their interaction with water. Such confinement, combined with the dilution of triplet emitters along the polymer chains, led to 1P having a photoluminescence quantum yield greater than that of 1M (0.061 vs 0.034, respectively, in an aerated water solution) with a longer lifetime of the (3)MLCT excited states and a blue-shifted emission (595 nm vs 604 nm, respectively). NMR data supported segregation of the metal centers. Photoreaction of O2 with 1,5-dihydroxynaphthalene showed that 1P is able to sensitize (1)O2 generation but with half the quantum yield of 1M. Cellular uptake experiments showed that both 1M and 1P are efficient cell staining agents endowed with two-photon excitation (TPE) imaging capability. TPE microscopy at 840 nm indicated that both complexes penetrate the cellular membrane of HeLa cells, localizing in the perinuclear region. Cellular photodynamic therapy tests showed that both 1M and 1P are able to induce cell apoptosis upon exposure to Xe lamp irradiation. The fraction of apoptotic cells for 1M was higher than that for 1P (74 and 38%, respectively) 6 h after being irradiated for 5 min, but cells incubated with 1P showed much lower levels of necrosis as well as lower toxicity in the absence of irradiation. More generally, the results indicate that cell damage induced by 1M was avoided by binding the iridium sensitizers to the poly(amidoamine).

Diketopyrrolopyrrole-porphyrin conjugates with high two-photon absorption and singlet oxygen generation for two-photon photodynamic therapy.

Two-photon photodynamic therapy is a promising therapeutic method which requires the development of sensitizers with efficient two-photon absorption and singlet-oxygen generation. Reported here are two new diketopyrrolopyrrole-porphyrin conjugates as robust two-photon absorbing dyes with high two-photon absorption cross-sections within the therapeutic window. Furthermore, for the first time the singlet-oxygen generation efficiency of diketopyrrolopyrrole-containing systems is investigated. A preliminary study on cell culture showed efficient two-photon induced phototoxicity.

Novel axially carborane-cage substituted silicon phthalocyanine photosensitizer; synthesis, characterization and photophysicochemical properties

The novel axially dicarborane substituted silicon (IV) (SiPc-DC) phthalocyanine was synthesized by treating silicon phthalocyanine dichloride SiPc(Cl)2 (SiPc) with o-Carborane monool. The compound was characterized by mass spectrometry, UV–Vis, FT-IR, 1H and 11B Nuclear Magnetic Resonance Spectroscopy (NMR). Spectral, photophysical (fluorescence quantum yield) and photochemical (singlet oxygen (ΦΔ) and photodegradation quantum yield (Φd)) properties of the complex were reported in different solutions (Dimethyl sulfoxide (DMSO), Dimethylformamide (DMF) and Toluene). The results of spectral measurements showed that both SiPc and carborane cage can have potential to be used as sensitizers in photodynamic therapy (PDT) and boron neutron capture therapy (BNCT) by their singlet oxygen efficiencies (ΦΔ=0.41, 0.39).

Binding of [Cr(phen)3]3+ to transferrin at extracellular and endosomal pHs: Potential application in photodynamic therapy

BackgroundTransferrin is an iron-binding blood plasma glycoprotein that controls the level of free iron in biological fluids. This protein has been deeply studied in the past few years because of its potential use as a strategy of drug targeting to tumor tissues. Chromium complex, [Cr(phen)3]3+ (phen=1,10-phenanthroline), has been proposed as photosensitizers for photodynamic therapy (PDT). Thus, we analyzed the binding of chromium complex, [Cr(phen)3]3+, to transferrin for a potential delivery of this diimine complex to tumor cells for PDT. MethodsThe interaction between [Cr(phen)3]3+ and holotransferrin (holoTf) was studied by fluorescence quenching technique, circular dichroism (CD) and ultraviolet (UV)–visible spectroscopy. Results[Cr(phen)3]3+ binds strongly to holoTf with a binding constant around 105M−1, that depends on the pH. The thermodynamic parameters indicated that hydrophobic interactions played a major role in the binding processes. The CD studies showed that there are no conformational changes in the secondary and tertiary structures of the protein. ConclusionsThese results suggest that the binding process would occur in a site different from the specific iron binding sites of the protein and would be the same in both protein states. As secondary and tertiary structures of transferrin do not show remarkable changes, we propose that the TfR could recognize the holoTf despite having a chromium complex associated. General significanceUnderstanding the interaction between [Cr(phen)3]3+ with transferrin is relevant because this protein could be a delivery agent of Cr(III) complex to tumor cells. This can allow us to understand further the role of Cr(III) complex as sensitizer in PDT.

Mechanisms of large red-shift and intensity enhancement of absorption bands by π-bond breaking in a benzoporphyrin sensitizer for photodynamic therapy

A free-base monobenzoporphyrin photosensitizer called verteporfin for photodynamic therapy (PDT) has a benzopyrrole ring with a partial π-bond breaking. The π-bond breaking significantly red-shifts the absorption band (so-called Qy-band) to 688 nm and enhances the absorption intensity. In this paper, we theoretically study the mechanisms of the red-shift and intensity enhancement in verteporfin. Density functional analysis at the B3LYP-6-31G(d,p) level of theory reveals that the π-bond breaking increases the energies of the highest occupied molecular orbital (HOMO) and second lowest unoccupied molecular orbital (LUMO+1) by 0.28 and 0.11 eV, respectively, and decreases the energy of the lowest unoccupied molecular orbital (LUMO) by 0.08 eV, in contrast to the unmoving second lowest occupied molecular orbital (HOMO-1). In the consequence of the higher energy shift of the HOMO and lower energy shift of the LUMO, the HOMO–LUMO gap is significantly narrowed. Therefore, the absorption red-shift in verteporfin is attributed to the HOMO–LUMO gap narrowing. On the other hand, the molecular-orbital shifts split the four electronically excited states, (HOMO, LUMO), (HOMO, LUMO+1), (HOMO-1, LUMO), and (HOMO-1, LUMO+1). The splitting weakens the configuration interactions between the excited states, which enhances the transition probability of the Qy-band.

Autophagy promotes resistance to photodynamic therapy-induced apoptosis selectively in colorectal cancer stem-like cells

Recent studies have indicated that cancer stem-like cells (CSCs) exhibit a high resistance to current therapeutic strategies, including photodynamic therapy (PDT), leading to the recurrence and progression of colorectal cancer (CRC). In cancer, autophagy acts as both a tumor suppressor and a tumor promoter. However, the role of autophagy in the resistance of CSCs to PDT has not been reported. In this study, CSCs were isolated from colorectal cancer cells using PROM1/CD133 (prominin 1) expression, which is a surface marker commonly found on stem cells of various tissues. We demonstrated that PpIX-mediated PDT induced the formation of autophagosomes in PROM1/CD133+ cells, accompanied by the upregulation of autophagy-related proteins ATG3, ATG5, ATG7, and ATG12. The inhibition of PDT-induced autophagy by pharmacological inhibitors and silencing of the ATG5 gene substantially triggered apoptosis of PROM1/CD133+ cells and decreased the ability of colonosphere formation in vitro and tumorigenicity in vivo. In conclusion, our results revealed a protective role played by autophagy against PDT in CSCs and indicated that targeting autophagy could be used to elevate the PDT sensitivity of CSCs. These findings would aid in the development of novel therapeutic approaches for CSC treatment.

ChemInform Abstract: Spectroscopic Analysis of the Interaction of Human Serum Albumin with Tricationic Phosphorus Porphyrins Bearing Axial Pyridinio Groups

AbstractReview: 37 refs.

Photodynamic effect of functionalized single-walled carbon nanotubes: a potential sensitizer for photodynamic therapy

Single-walled carbon nanotubes (SWNTs) possess unique physical and chemical properties, which make them very attractive for a wide range of applications. In particular, SWNTs and their composites have shown a great potential for photodynamic therapy (PDT). SWNTs have usually been used for photothermal therapy; herein, the photodynamic effect of two functionalized SWNTs are detected under visible light illumination in vitro and in vivo. The results indicated that the photodynamic effect is not entirely dependent on illumination time, but also on the modification method of the SWNTs. The ability of SWNTs complexes to combine with photodynamic therapy significantly improved the therapeutic efficacy of cancer treatment, and the combined treatment demonstrated a synergistic effect. These findings suggest that the SWNTs composite has great potential as sensitizer for PDT.

Composite Conjugated Polymer/Fullerene Nanoparticles as Sensitizers in Photodynamic Therapy for Cancer

The fabrication and study of composite conjugated polymer nanoparticles doped with fullerene for application in photodynamic therapy (PDT) is reported. The nanoparticles are not intrinsically cytotoxic and show specificity towards cancer cells without surface modification. The high absorption cross-section and efficient charge transfer from conjugated polymer to fullerene in the composite nanoparticles results in only moderate light levels being necessary for PDT. The PDT scheme was tested in vitro for MDA-MB-231 (human breast cancer), A549 (human lung cancer), and OVCAR3 (human ovarian cancer) cell lines. While the treatment was observed to be only marginally effective for the MDA-MB-231 cell line, 60 % and complete cell death was observed for the A549 and OVCAR3 cell lines, respectively. Differences in PDT efficiency are attributed to the difference in nanoparticle uptake between these cell lines, and is potentially related to differences in metabolic rate. Through live/dead cell staining apoptotic cell death was observed for OVCAR3. This is a promising finding for potential development of treatment for ovarian cancer by the PDT scheme discussed herein.

Optimization of Triplet Excited State and Singlet Oxygen Quantum Yields of Picolylamine–Porphyrin Conjugates through Zinc Insertion

We synthesized a new class of picolylamine-porphyrin conjugates 1-3 and have investigated the effect of heavy atom insertion on their intersystem crossing efficiency through spin-orbit perturbations. By incorporating zinc ions in the core as well as periphery positions of the porphyrin ring, we have successfully optimized their triplet excited state quantum yields and their efficiency to generate singlet oxygen. Uniquely, the picolylamine-porphyrin conjugate 3 having five zinc ions exhibited a triplet excited state quantum yield of ca. 0.97 and a sensitized singlet oxygen generation yield of ca. 0.92. In contrast, the free base porphyrin derivative 1 exhibited ca. 0.64 and 0.5 of the triplet excited state and singlet oxygen quantum yields, respectively. Our results demonstrate that the insertion of zinc metal ions in the picolylamine-porphyrin conjugates not only quantitatively enhances the triplet excited state and singlet oxygen yields but also imparts hydrophilicity, thereby their potential use as sensitizers in photodynamic therapy and green photooxygenation reactions.

Spectroscopic Analysis of the Interaction of Human Serum Albumin with Tricationic Phosphorus Porphyrins Bearing Axial Pyridinio Groups

Abstract Much attention has been paid to water-soluble porphyrins and metalloporphyrins as potential sensitizers for photodynamic therapy (PDT). Thus, water-soluble tricationic phosphorus porphyrin complexes were prepared via the introduction of an N-alkylpyridinio group on the axial ligands of phosphorus porphyrins. The resulting tricationic phosphorus porphyrins readily dissolve in aqueous solutions without the formation of aggregates, even at high concentration. Moreover, the affinity of the porphyrins to human serum albumin (HSA) is a key factor in their application to PDT since HSA plays an important role in the transport of drug molecules to a target cell. Interactions between the tricationic phosphorus porphyrins and HSA were examined on the basis of changes in the Soret bands of the absorption and fluorescence spectra of phosphorus porphyrin solutions in the presence of HSA and the fluorescence quenching of HSA by the tricationic phosphorus porphyrins. Tricationic phosphorus porphyrins with moderately long alkyl chains on the pyridinio group were strongly adsorbed on the HSA at a position near the tryptophan residue of HSA. This result suggests that tricationic phosphorus porphyrins containing alkyl groups are good candidates as PDT reagents because of their high water solubility and high affinity for HSA.

Differentiation of tumor sensitivity to photodynamic therapy and early evaluation of treatment effect by nuclear medicine techniques

Our final goal is to develop an appropriate method using nuclear medicine technique for monitoring the effect and prediction of Photodynamic Therapy (PDT) on tumors. The aim of this study is to evaluate the effect of PDT on tumor cells in vitro using (18)F-FDG and (99m)Tc-MIBI as tracers. Five tumor cell lines (A431, DU145, H1650, LS180, SHIN3) with varied characteristics were irradiated after incubating for 24h with several doses of Photofrin (PF). Singlet oxygen was monitored by the near-IR emission detection system during irradiation and generated (1)O2 was calculated. PDT effects were rapidly evaluated by nuclear medicine techniques (uptake of (18)F-FDG and (99m)Tc-MIBI) and traditional methods for cell viability (MTT and trypan blue assays) at 3h after PDT. Intracellular PF concentration was measured by absorption spectrometer and cell protein content was measured by the Lowry method. (18)F-FDG uptake, (99m)Tc-MIBI uptake, singlet oxygen, and intracellular PF concentration were standardized by protein content. Decrease % of (18)F-FDG and (99m)Tc-MIBI, MTT, and trypan blue was normalized to the control group. Decrease % of (18)F-FDG was exponentially related to decrease % of MTT (R (2)=0.650, P<0.01) while decrease % of (99m)Tc-MIBI was linearly related to that of MTT (R (2)=0.719, P<0.01). The decrease % of MTT was more sensitive than that of trypan blue. However, neither (1)O2 nor PF uptake was correlated with sensitivity to PDT. In addition, (18)F-FDG uptake before PDT was linearly related to decrease % of MTT (R (2)=0.800, P<0.05). Our findings in in vitro studies suggest that (99m)Tc-MIBI is better than (18)F-FDG for early evaluation of PDT effect, but (18)F-FDG uptake may be used to predict PDT sensitivity before therapy.

Dye Sensitizers for Photodynamic Therapy.

Photofrin® was first approved in the 1990s as a sensitizer for use in treating cancer via photodynamic therapy (PDT). Since then a wide variety of dye sensitizers have been developed and a few have been approved for PDT treatment of skin and organ cancers and skin diseases such as acne vulgaris. Porphyrinoid derivatives and precursors have been the most successful in producing requisite singlet oxygen, with Photofrin® still remaining the most efficient sensitizer (quantum yield = 0.89) and having broad food and drug administration (FDA) approval for treatment of multiple cancer types. Other porphyrinoid compounds that have received approval from US FDA and regulatory authorities in other countries include benzoporphyrin derivative monoacid ring A (BPD-MA), meta-tetra(hydroxyphenyl)chlorin (m-THPC), N-aspartyl chlorin e6 (NPe6), and precursors to endogenous protoporphyrin IX (PpIX): 1,5-aminolevulinic acid (ALA), methyl aminolevulinate (MAL), hexaminolevulinate (HAL). Although no non-porphyrin sensitizer has been approved for PDT applications, a small number of anthraquinone, phenothiazine, xanthene, cyanine, and curcuminoid sensitizers are under consideration and some are being evaluated in clinical trials. This review focuses on the nature of PDT, dye sensitizers that have been approved for use in PDT, and compounds that have entered or completed clinical trials as PDT sensitizers.

Boron‐Fluorine Photosensitizers for Photodynamic Therapy

Photodynamic therapy (PDT) has been recognized as a promising treatment for cancers and tumors, in which photosensitizer is one of the most important issues. As a class of excellent fluorescent dyes, boron‐fluorine derivatives (typically 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene, BODIPY) have preferable ability of generating singlet oxygen and have been under extensive study for PDT sensitizers. In this review, we summarize the recent progress of design and applications of boron‐fluorine‐based photosensitizers for PDT.