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Lee MH, Thomas JL, Li JA, Chen JR, Wang TL, Lin HY. Synthesis of Multifunctional Nanoparticles for the Combination of Photodynamic Therapy and Immunotherapy. Pharmaceuticals (Basel) 2021; 14:ph14060508. [PMID: 34073468 PMCID: PMC8228393 DOI: 10.3390/ph14060508] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/20/2021] [Accepted: 05/21/2021] [Indexed: 12/14/2022] Open
Abstract
Programmed death-ligand 1 protein (PD-L1) has been posited to have a major role in suppressing the immune system during pregnancy, tissue allografts, autoimmune disease and other diseases, such as hepatitis. Photodynamic therapy uses light and a photosensitizer to generate singlet oxygen, which causes cell death (phototoxicity). In this work, photosensitizers (such as merocyanine) were immobilized on the surface of magnetic nanoparticles. One peptide sequence from PD-L1 was used as the template and imprinted onto poly(ethylene-co-vinyl alcohol) to generate magnetic composite nanoparticles for the targeting of PD-L1 on tumor cells. These nanoparticles were characterized using dynamic light scattering, high-performance liquid chromatography, Brunauer-Emmett-Teller analysis and superconducting quantum interference magnetometry. Natural killer-92 cells were added to these composite nanoparticles, which were then incubated with human hepatoma (HepG2) cells and illuminated with visible light for various periods. The viability and apoptosis pathway of HepG2 were examined using a cell counting kit-8 and quantitative real-time polymerase chain reaction. Finally, treatment with composite nanoparticles and irradiation of light was performed using an animal xenograft model.
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Affiliation(s)
- Mei-Hwa Lee
- Department of Materials Science and Engineering, I-Shou University, Kaohsiung 84001, Taiwan
- Correspondence: (M.-H.L.); (H.-Y.L.)
| | - James L. Thomas
- Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131, USA;
| | - Jin-An Li
- Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan; (J.-A.L.); (J.-R.C.); (T.-L.W.)
| | - Jyun-Ren Chen
- Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan; (J.-A.L.); (J.-R.C.); (T.-L.W.)
| | - Tzong-Liu Wang
- Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan; (J.-A.L.); (J.-R.C.); (T.-L.W.)
| | - Hung-Yin Lin
- Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan; (J.-A.L.); (J.-R.C.); (T.-L.W.)
- Correspondence: (M.-H.L.); (H.-Y.L.)
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2
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Dubbert J, Höing A, Riek N, Knauer SK, Voskuhl J. Supramolecular subphthalocyanine complexes-cellular uptake and phototoxicity. Chem Commun (Camb) 2020; 56:7653-7656. [PMID: 32520022 DOI: 10.1039/d0cc03065a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
In this communication we report on the synthesis and application of axially functionalized boron-subphthalocyanines (SubPC) which are able to form host-guest complexes with cyclodextrins. Here, a tert-butylphenyl substituted SubPC was investigated concerning its complexation with β-cyclodextrin (β-CD) and a β-cyclodextrin polymer. NMR-titrations showed the formation of a 1 : 1 complex with β-CD. These assemblies were analyzed for their cellular distribution as well as their phototoxicity towards HeLa cells.
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Affiliation(s)
- Justin Dubbert
- Institute of Organic Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117, Essen, Germany.
| | - Alexander Höing
- Department of Molecular Biology II, Center of Medical Biotechnology (ZMB), University of Duisburg-Essen, Universitätsstrasse 5, D-45117 Essen, Germany
| | - Nathalie Riek
- Institute of Organic Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117, Essen, Germany.
| | - Shirley K Knauer
- Department of Molecular Biology II, Center of Medical Biotechnology (ZMB), University of Duisburg-Essen, Universitätsstrasse 5, D-45117 Essen, Germany
| | - Jens Voskuhl
- Institute of Organic Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117, Essen, Germany.
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3
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Pawlak AM, Olchawa M, Koscielniak A, Zadlo A, Broniec A, Oles T, Sarna TJ. Oxidized Lipids Decrease Phagocytic Activity of ARPE‐19 Cells In Vitro. EUR J LIPID SCI TECH 2019. [DOI: 10.1002/ejlt.201800476] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Anna M. Pawlak
- Faculty of BiochemistryDepartment of Biophysics, Biophysics and BiotechnologyJagiellonian University30‐007 KrakowPoland
| | - Magdalena Olchawa
- Faculty of BiochemistryDepartment of Biophysics, Biophysics and BiotechnologyJagiellonian University30‐007 KrakowPoland
| | - Anna Koscielniak
- Faculty of BiochemistryDepartment of Biophysics, Biophysics and BiotechnologyJagiellonian University30‐007 KrakowPoland
- Faculty of Electrical Engineering, Automatics, Computer Science and Biomedical EngineeringAGH‐University of Science and Technology30‐059 KrakówPoland
| | - Andrzej Zadlo
- Faculty of BiochemistryDepartment of Biophysics, Biophysics and BiotechnologyJagiellonian University30‐007 KrakowPoland
| | - Agnieszka Broniec
- Faculty of BiochemistryDepartment of Biophysics, Biophysics and BiotechnologyJagiellonian University30‐007 KrakowPoland
| | - Tomasz Oles
- Faculty of BiochemistryDepartment of Biophysics, Biophysics and BiotechnologyJagiellonian University30‐007 KrakowPoland
| | - Tadeusz J. Sarna
- Faculty of BiochemistryDepartment of Biophysics, Biophysics and BiotechnologyJagiellonian University30‐007 KrakowPoland
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4
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Kabanov V, Ghosh S, Lovell JF, Heyne B. Singlet oxygen partition between the outer-, inner- and membrane-phases of photo/chemotherapeutic liposomes. Phys Chem Chem Phys 2019; 21:25054-25064. [DOI: 10.1039/c9cp05159g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Herein, we developed a strategy to quantify the fraction of singlet oxygen lifetime spent in the three distinct local liposomal environments through the combination of direct and indirect singlet oxygen detection approaches.
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Affiliation(s)
| | - Sanjana Ghosh
- Department of Biomedical Engineering
- University at Buffalo
- Buffalo
- USA
| | | | - Belinda Heyne
- Department of Chemistry
- University of Calgary
- Calgary
- Canada
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5
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Kabanov V, Press DJ, Huynh RPS, Shimizu GKH, Heyne B. Assessment of encapsulated dyes’ distribution in silica nanoparticles and their ability to release useful singlet oxygen. Chem Commun (Camb) 2018; 54:6320-6323. [DOI: 10.1039/c8cc03413c] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Working with silica nanoparticle encapsulated BODIPY and xanthene photosensitizers, we have determined that singlet oxygen spends up to 78% of its lifetime inside the nanocarriers.
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Affiliation(s)
| | - David J. Press
- Department of Chemistry
- University of Calgary
- Calgary
- Canada
| | | | | | - Belinda Heyne
- Department of Chemistry
- University of Calgary
- Calgary
- Canada
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6
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Takemoto K, Matsuda T, Sakai N, Fu D, Noda M, Uchiyama S, Kotera I, Arai Y, Horiuchi M, Fukui K, Ayabe T, Inagaki F, Suzuki H, Nagai T. SuperNova, a monomeric photosensitizing fluorescent protein for chromophore-assisted light inactivation. Sci Rep 2014; 3:2629. [PMID: 24043132 PMCID: PMC3775092 DOI: 10.1038/srep02629] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 08/22/2013] [Indexed: 11/20/2022] Open
Abstract
Chromophore-assisted light inactivation (CALI) is a powerful technique for acute perturbation of biomolecules in a spatio-temporally defined manner in living specimen with reactive oxygen species (ROS). Whereas a chemical photosensitizer including fluorescein must be added to specimens exogenously and cannot be restricted to particular cells or sub-cellular compartments, a genetically-encoded photosensitizer, KillerRed, can be controlled in its expression by tissue specific promoters or subcellular localization tags. Despite of this superiority, KillerRed hasn't yet become a versatile tool because its dimerization tendency prevents fusion with proteins of interest. Here, we report the development of monomeric variant of KillerRed (SuperNova) by direct evolution using random mutagenesis. In contrast to KillerRed, SuperNova in fusion with target proteins shows proper localization. Furthermore, unlike KillerRed, SuperNova expression alone doesn't perturb mitotic cell division. Supernova retains the ability to generate ROS, and hence promote CALI-based functional analysis of target proteins overcoming the major drawbacks of KillerRed.
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Affiliation(s)
- Kiwamu Takemoto
- 1] Research Institute for Electronic Sciences, Hokkaido University, Kita-20 Nishi-10 Kita-ku, Sapporo, Hokkaido 001-0020, Japan [2] [3]
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7
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Chen NT, Tang KC, Chung MF, Cheng SH, Huang CM, Chu CH, Chou PT, Souris JS, Chen CT, Mou CY, Lo LW. Enhanced plasmonic resonance energy transfer in mesoporous silica-encased gold nanorod for two-photon-activated photodynamic therapy. Theranostics 2014; 4:798-807. [PMID: 24955141 PMCID: PMC4063978 DOI: 10.7150/thno.8934] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 04/17/2014] [Indexed: 11/25/2022] Open
Abstract
The unique optical properties of gold nanorods (GNRs) have recently drawn considerable interest from those working in in vivo biomolecular sensing and bioimaging. Especially appealing in these applications is the plasmon-enhanced photoluminescence of GNRs induced by two-photon excitation at infrared wavelengths, owing to the significant penetration depth of infrared light in tissue. Unfortunately, many studies have also shown that often the intensity of pulsed coherent irradiation of GNRs needed results in irreversible deformation of GNRs, greatly reducing their two-photon luminescence (TPL) emission intensity. In this work we report the design, synthesis, and evaluation of mesoporous silica-encased gold nanorods (MS-GNRs) that incorporate photosensitizers (PSs) for two-photon-activated photodynamic therapy (TPA-PDT). The PSs, doped into the nano-channels of the mesoporous silica shell, can be efficiently excited via intra-particle plasmonic resonance energy transfer from the encased two-photon excited gold nanorod and further generates cytotoxic singlet oxygen for cancer eradication. In addition, due to the mechanical support provided by encapsulating mesoporous silica matrix against thermal deformation, the two-photon luminescence stability of GNRs was significantly improved; after 100 seconds of 800 nm repetitive laser pulse with the 30 times higher than average power for imaging acquisition, MS-GNR luminescence intensity exhibited ~260% better resistance to deformation than that of the uncoated gold nanorods. These results strongly suggest that MS-GNRs with embedded PSs might provide a promising photodynamic therapy for the treatment of deeply situated cancers via plasmonic resonance energy transfer.
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Musbat L, Weitman H, Ehrenberg B. Azide quenching of singlet oxygen in suspensions of microenvironments of neutral and surface charged liposomes and micelles. Photochem Photobiol 2012; 89:253-8. [PMID: 22827592 DOI: 10.1111/j.1751-1097.2012.01212.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 07/18/2012] [Indexed: 11/28/2022]
Abstract
The azide anion is often used as a physical quencher of singlet oxygen, the important active intermediate in photosensitized oxidation. An observed effect of azide on the rate of a reaction is considered an indication to the involvement of singlet oxygen. In most biological photosensitizations, the light-absorbing sensitizer is located in a membrane or in an intracellular organelle, whereas azide is water soluble. The quenching it causes relies on a physical encounter with singlet oxygen during the latter's short lifetime. This can happen either if azide penetrates into the membrane's lipid phase or if singlet oxygen is intercepted when diffusing in the aqueous phase. We demonstrate in this article the difference, in liposomes' suspension, between the effect of azide when using a water-soluble and membrane-bound chemical targets of singlet oxygen, whereas this difference does not exist when micelles are used. We explain the difference on the population of sensitizer and target in the liposome vs micelle. We also show the effect that exists on azide quenching of singlet oxygen by electrically charged lipids in liposomes. This is a result of the accumulation or dilution of azide in the debye layer near the membranes' surface, due to the surface Gouy-Chapman potential.
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Affiliation(s)
- Lihi Musbat
- Department of Physics, Institute of Nanotechnology and Advanced Materials Bar Ilan University, Ramat Gan, Israel
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9
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Takemoto K, Matsuda T, McDougall M, Klaubert DH, Hasegawa A, Los GV, Wood KV, Miyawaki A, Nagai T. Chromophore-assisted light inactivation of HaloTag fusion proteins labeled with eosin in living cells. ACS Chem Biol 2011; 6:401-6. [PMID: 21226520 DOI: 10.1021/cb100431e] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chromophore-assisted light inactivation (CALI) is a potentially powerful tool for the acute disruption of a target protein inside living cells with high spatiotemporal resolution. This technology, however, has not been widely utilized, mainly because of the lack of an efficient chromophore as the photosensitizing agent for singlet oxygen ((1)O(2)) generation and the difficulty of covalently labeling the target protein with the chromophore. Here we choose eosin as the photosensitizing chromophore showing 11-fold more production of ((1)O(2)) than fluorescein and about 5-fold efficiency in CALI of β-galactosidase by using an eosin-labeled anti-β-galactosidase antibody compared with the fluorescein-labeled one. To covalently label target protein with eosin, we synthesize a membrane-permeable eosin ligand for HaloTag technology, demonstrating easy labeling and efficient inactivation of HaloTag-fused PKC-γ and aurora B in living cells. These antibody- and HaloTag-based CALI techniques using eosin promise effective biomolecule inactivation that is applicable to many cell biological assays in living cells.
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Affiliation(s)
- Kiwamu Takemoto
- Laboratory for Nanosystems Physiology, Research Institute for Electronic Sciences, Hokkaido University, Kita20, Nishi10, Kita-ku, Sapporo, Hokkaido 001-0020, Japan
| | - Tomoki Matsuda
- Laboratory for Nanosystems Physiology, Research Institute for Electronic Sciences, Hokkaido University, Kita20, Nishi10, Kita-ku, Sapporo, Hokkaido 001-0020, Japan
| | - Mark McDougall
- Promega BioSciences, 277 Granada Drive, San Luis Obispo, California 93401, United States
| | - Dieter H. Klaubert
- Promega BioSciences, 277 Granada Drive, San Luis Obispo, California 93401, United States
| | - Akira Hasegawa
- Promega KK, Matsumoto Building, 14-15 Nihonbashi, Odemacho, Chuo-Ku, Tokyo 103-0011, Japan
| | - Georgyi V. Los
- Promega Corporation, 2800 Woods Hollow Road, Madison, Wisconsin 53711, United States
| | - Keith V. Wood
- Promega Corporation, 2800 Woods Hollow Road, Madison, Wisconsin 53711, United States
| | - Atsushi Miyawaki
- Laboratory for Cell Function and Dynamics, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Takeharu Nagai
- Laboratory for Nanosystems Physiology, Research Institute for Electronic Sciences, Hokkaido University, Kita20, Nishi10, Kita-ku, Sapporo, Hokkaido 001-0020, Japan
- Precursory Research for Embryonic Science, Japan Science and Technology Agency, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan
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10
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Fadel M, Kassab K, Youssef T. Photodynamic efficacy of hypericin targeted by two delivery techniques to hepatocellular carcinoma cells. Lasers Med Sci 2010; 25:675-83. [DOI: 10.1007/s10103-010-0787-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2009] [Indexed: 11/30/2022]
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11
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Membrane transport of singlet oxygen monitored by dipole potential measurements. Biophys J 2010; 96:77-85. [PMID: 18931253 DOI: 10.1529/biophysj.108.135145] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 09/03/2008] [Indexed: 11/18/2022] Open
Abstract
The efficiency of photodynamic reactions depends on 1), the penetration depth of the photosensitizer into the membrane and 2), the sidedness of the target. Molecules which are susceptible to singlet oxygen ((1)O(2)) experience less damage when separated from the photosensitizer by the membrane. Since (1)O(2) lifetime in the membrane environment is orders of magnitude longer than the time required for nonexcited oxygen (O(2)) to cross the membrane, this observation suggests that differences between the permeabilities or membrane partition of (1)O(2) and O(2) exist. We investigated this hypothesis by releasing (1)O(2) at one side of a planar membrane while monitoring the kinetics of target damage at the opposite side of the same membrane. Damage to the target, represented by dipole-modifying molecules (phloretin or phlorizin), was indicated by changes in the interleaflet dipole potential difference Deltaphi(b). A simple analytical model allowed estimation of the (1)O(2) interleaflet concentration difference from the rate at which Deltaphi(b) changed. It confirmed that the lower limit of (1)O(2) permeability is approximately 2 cm/s; i.e., it roughly matches O(2) permeability as predicted by Overton's rule. Consequently, the membrane cannot act as a barrier to (1)O(2) diffusion. Differences in the reaction rates at the cytoplasmic and extracellular membrane leaflets may be attributed only to (1)O(2) quenchers inside the membrane.
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Rapozzi V, Beverina L, Salice P, Pagani GA, Camerin M, Xodo LE. Photooxidation and Phototoxicity of π-Extended Squaraines. J Med Chem 2010; 53:2188-96. [DOI: 10.1021/jm901727j] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Valentina Rapozzi
- Department of Biomedical Science and Technology, University of Udine, P.le Kolbe 4, I-33100 Udine, Italy
| | - Luca Beverina
- Department of Materials Science and INSTM, University of Milano-Bicocca, via Cozzi 53 I-20125 Milano, Italy
| | - Patrizio Salice
- Department of Materials Science and INSTM, University of Milano-Bicocca, via Cozzi 53 I-20125 Milano, Italy
| | - Giorgio A. Pagani
- Department of Materials Science and INSTM, University of Milano-Bicocca, via Cozzi 53 I-20125 Milano, Italy
| | - Monica Camerin
- Department of Biology, Via U. Bassi 58/B, University of Padova, 35131 Padova, Italy
| | - Luigi E. Xodo
- Department of Biomedical Science and Technology, University of Udine, P.le Kolbe 4, I-33100 Udine, Italy
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Alarcón E, Aspée A, González-Béjar M, Edwards AM, Lissi E, Scaiano JC. Photobehavior of merocyanine 540 bound to human serum albumin. Photochem Photobiol Sci 2010; 9:861-9. [DOI: 10.1039/c0pp00079e] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Serra A, Pineiro M, Rocha Gonsalves A, Abrantes M, Laranjo M, Santos A, Botelho M. Halogen atom effect on photophysical and photodynamic characteristics of derivatives of 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2008; 92:59-65. [DOI: 10.1016/j.jphotobiol.2008.04.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Revised: 01/21/2008] [Accepted: 04/23/2008] [Indexed: 10/22/2022]
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15
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Delanaye L, Bahri MA, Tfibel F, Fontaine-Aupart MP, Mouithys-Mickalad A, Heine B, Piette J, Hoebeke M. Physical and chemical properties of pyropheophorbide-a methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-l-α-phosphatidylcholine vesicles. Photochem Photobiol Sci 2006; 5:317-25. [PMID: 16520867 DOI: 10.1039/b513219c] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The aggregation process of pyropheophorbide-a methyl ester (PPME), a second-generation photosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-alpha-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in the presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS).
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Affiliation(s)
- Lisiane Delanaye
- Department of Physics, B5, University of Liège, B-4000, Liège, Belgium.
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16
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Bahri MA, Heyne BJ, Hans P, Seret AE, Mouithys-Mickalad AA, Hoebeke MD. Quantification of lipid bilayer effective microviscosity and fluidity effect induced by propofol. Biophys Chem 2004; 114:53-61. [PMID: 15792861 DOI: 10.1016/j.bpc.2004.11.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2004] [Revised: 11/03/2004] [Accepted: 11/03/2004] [Indexed: 10/26/2022]
Abstract
Electron spin resonance (ESR) spectroscopy with nitroxide spin probes was used as a method to probe the liposome microenvironments. The effective microviscosities have been determined from the calibration of the ESR spectra of the probes in solvent mixtures of known viscosities. In the first time, by measuring ESR order parameter (S) and correlation time (tau(c)) of stearic spin probes, we have been able to quantify the value of effective microviscosity at different depths inside the liposome membrane. At room temperature, local microviscosities measured in dimyristoyl-l-alpha phosphatidylcholine (DMPC) liposome membrane at the different depths of 7.8, 16.95, and 27.7 A were 222.53, 64.09, and 62.56 cP, respectively. In the gel state (10 degrees C), those microviscosity values increased to 472.56, 370.61, and 243.37 cP. In a second time, we have applied this technique to determine the modifications in membrane microviscosity induced by 2,6-diisopropyl phenol (propofol; PPF), an anaesthetic agent extensively used in clinical practice. Propofol is characterized by a unique phenolic structure, absent in the other conventional anaesthetics. Indeed, given its lipophilic property, propofol is presumed to penetrate into and interact with membrane lipids and hence to induce changes in membrane fluidity. Incorporation of propofol into dimyristoyl-l-alpha phosphatidylcholine liposomes above the phase-transition temperature (23.9 degrees C) did not change microviscosity. At 10 degrees C, an increase of propofol concentration from 0 to 1.0 x 10(-2) M for a constant lipid concentration mainly induced a decrease in microviscosity. This fluidity effect of propofol has been qualitatively confirmed using merocyanine 540 (MC540) as lipid packing probe. Above 10(-2) M propofol, no further decrease in microviscosity was observed, and the microviscosity at the studied depths (7.8, 16.95, and 27.7 A) amounted 260.21, 123.87, and 102.27 cP, respectively. The concentration 10(-2) M was identified as the saturation limit of propofol in dimyristoyl-l-alpha phosphatidylcholine liposomes.
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Affiliation(s)
- Mohamed A Bahri
- Laboratory of Experimental Medical Imaging, Liège, Belgium; Department of Physics, Institute of Physics, B5, University of Liege, Sart-Tilman, B-4000, Liège, Belgium
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Wrona M, Rózanowska M, Sarna T. Zeaxanthin in combination with ascorbic acid or alpha-tocopherol protects ARPE-19 cells against photosensitized peroxidation of lipids. Free Radic Biol Med 2004; 36:1094-101. [PMID: 15082063 DOI: 10.1016/j.freeradbiomed.2004.02.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2003] [Revised: 01/08/2004] [Accepted: 02/02/2004] [Indexed: 11/28/2022]
Abstract
The antioxidant action of carotenoids is believed to involve quenching of singlet oxygen and scavenging of reactive oxygen radicals. However, the exact mechanism by which carotenoids protect cells against oxidative damage, particularly in the presence of other antioxidants, remains to be elucidated. This study was carried out to examine the ability of exogenous zeaxanthin alone and in combination with vitamin E or C, to protect cultured human retinal pigment epithelium cells against oxidative stress. The survival of ARPE-19 cells, subjected to merocyanine 540-mediated photodynamic action, was determined by the MTT test and the content of lipid hydroperoxides in photosensitized cells was analyzed by HPLC with electrochemical detection. We found that zeaxanthin-supplemented cells, in the presence of either alpha-tocopherol or ascorbic acid, were significantly more resistant to photoinduced oxidative stress. Cells with added antioxidants exhibited increased viability and accumulated less lipid hydroperoxides than cells without the antioxidant supplementation. Such a synergistic action of zeaxanthin and vitamin E or C indicates the importance of the antioxidant interaction in efficient protection of cell membranes against oxidative damage induced by photosensitized reactions.
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Affiliation(s)
- Marta Wrona
- Department of Biophysics, Faculty of Biotechnology, Jagiellonian University, Kraków, Poland
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18
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Lavi A, Weitman H, Holmes RT, Smith KM, Ehrenberg B. The depth of porphyrin in a membrane and the membrane's physical properties affect the photosensitizing efficiency. Biophys J 2002; 82:2101-10. [PMID: 11916866 PMCID: PMC1302004 DOI: 10.1016/s0006-3495(02)75557-4] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Photosensitized biological processes, as applied in photodynamic therapy, are based on light-triggered generation of molecular singlet oxygen by a membrane-residing sensitizer. Most of the sensitizers currently used are hydrophobic or amphiphilic porphyrins and their analogs. The possible activity of the short-lived singlet oxygen is limited to the time it is diffusing in the membrane, before it emerges into the aqueous environment. In this paper we demonstrate the enhancement of the photosensitization process that is obtained by newly synthesized protoporphyrin derivatives, which insert their tetrapyrrole chromophore deeper into the lipid bilayer of liposomes. The insertion was measured by fluorescence quenching by iodide and the photosensitization efficiency was measured with 9,10-dimethylanthracene, a fluorescent chemical target for singlet oxygen. We also show that when the bilayer undergoes a melting phase transition, or when it is fluidized by benzyl alcohol, the sensitization efficiency decreases because of the enhanced diffusion of singlet oxygen. The addition of cholesterol or of dimyristoyl phosphatydilcholine to the bilayer moves the porphyrin deeper into the bilayer; however, the ensuing effect on the sensitization efficiency is different in these two cases. These results could possibly define an additional criterion for the choice and design of hydrophobic, membrane-bound photosensitizers.
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Affiliation(s)
- Adina Lavi
- Department of Physics, Bar Ilan University, Ramat Gan 52-900, Israel
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Hoebeke M, Damoiseau X. Determination of the singlet oxygen quantum yield of bacteriochlorin a: a comparative study in phosphate buffer and aqueous dispersion of dimiristoyl-L-alpha-phosphatidylcholine liposomes. Photochem Photobiol Sci 2002; 1:283-7. [PMID: 12661969 DOI: 10.1039/b201081j] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The production of singlet oxygen (1O2) by bacteriochlorin a (BCA) was studied in phosphate buffer and in dimyristoyl-L-alpha-phosphatidylcholine (DMPC) unilamellar liposomes. The comparative method used to measure 1O2 production was a quantitative analysis of photooxidation reactions leading to the loss of absorbance of the water-soluble specific probe: anthracene-9,10-dipropionic acid. Rose Bengal, whose 1O2 quantum yield (phi(RB)) is well known in alcohols and phosphate buffer, was used as the standard for the quantification of the BCA singlet oxygen production. Our results confirm quantitatively that solubilization of BCA in liposomes leads to an increase in 1O2 production. Indeed, the quantum yield of 1O2 production by BCA (phi(BCA)) is 0.05 in phosphate buffer and 0.33 in DMPC liposomes. Furthermore, the diffusion characteristics of 1O2 produced by BCA bound to liposome were also examined using the isotopic lifetime enhancement effect of D2O. It was shown that 1O2 spent at least 70% of its lifetime in the vesicular environment.
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Affiliation(s)
- Maryse Hoebeke
- Centre of Oxygen R&D (CORD), Department of Physics, Institute of Physics, B5, University of Liège, 4000 Liège, Belgium.
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Damoiseau X, Schuitmaker HJ, Lagerberg JW, Hoebeke M. Increase of the photosensitizing efficiency of the Bacteriochlorin a by liposome-incorporation. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2001; 60:50-60. [PMID: 11386681 DOI: 10.1016/s1011-1344(01)00118-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To describe the action mechanisms of Bacteriochlorin a (BCA), a second generation photosensitizer, in phosphate buffer (PB) and in dimyristoyl phosphatidylcholine (DMPC) liposomes we carried out oxygen consumption and ESR measurements. In PB, where BCA was in a monomer-dimer equilibrium, our results suggested that the oxygen consumption was related to the BCA monomers concentration in solution. Incorporation of BCA in DMPC liposomes, by promoting the monomerization of BCA, increased 9-fold the oxygen consumption in comparison to the value in PB. The use of specific singlet oxygen quenchers (Azide and 9,10-Anthracenedipropionic acid) in ESR and oxygen consumption experiments allowed us to assert that BCA was mainly a type II sensitizer when it was incorporated in DMPC. Finally, the cell survival of WiDr cells after a PDT treatment was measured for cells incubated with BCA in cell culture medium and cells incubated with BCA in DMPC. Irrespective of the dye concentration, the cell survival was lower when liposomes were used. This effect could be the result of a better BCA monomerization and/or a different BCA uptake in cells.
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Affiliation(s)
- X Damoiseau
- Experimental Physics, Institute of Physics, University of Liège, Belgium.
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Li HR, Wu LZ, Tung CH. Reactions of Singlet Oxygen with Olefins and Sterically Hindered Amine in Mixed Surfactant Vesicles. J Am Chem Soc 2000. [DOI: 10.1021/ja9917161] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hong-Ru Li
- Contribution from the Institute of Photographic Chemistry, the Chinese Academy of Sciences, Beijing 100101, P. R. China, and Center for Molecular Science, Institute of Chemistry, the Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Li-Zhu Wu
- Contribution from the Institute of Photographic Chemistry, the Chinese Academy of Sciences, Beijing 100101, P. R. China, and Center for Molecular Science, Institute of Chemistry, the Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Chen-Ho Tung
- Contribution from the Institute of Photographic Chemistry, the Chinese Academy of Sciences, Beijing 100101, P. R. China, and Center for Molecular Science, Institute of Chemistry, the Chinese Academy of Sciences, Beijing 100080, P. R. China
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22
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Vilensky A, Feitelson J. Reactivity of Singlet Oxygen with Tryptophan Residues and with Melittin in Liposome Systems. Photochem Photobiol 1999. [DOI: 10.1111/j.1751-1097.1999.tb08291.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Redmond RW, Gamlin JN. A Compilation of Singlet Oxygen Yields from Biologically Relevant Molecules. Photochem Photobiol 1999. [DOI: 10.1111/j.1751-1097.1999.tb08240.x] [Citation(s) in RCA: 573] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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24
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Fluorescent Dimers of Merocyanine 540 (MC540) in the Gel Phase of Phosphatidylcholine Liposomes. Photochem Photobiol 1999. [DOI: 10.1111/j.1751-1097.1999.tb01947.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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25
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Bilski P, McDevitt T, Chignell CF. Merocyanine 540 Solubilized as an Ion Pair with Cationic Surfactant in Nonpolar Solvents: Spectral and Photochemical Properties. Photochem Photobiol 1999. [DOI: 10.1111/j.1751-1097.1999.tb03344.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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26
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Ehrenberg B, Anderson JL, Foote CS. Kinetics and Yield of Singlet Oxygen Photosensitized by Hypericin in Organic and Biological Media. Photochem Photobiol 1998. [DOI: 10.1111/j.1751-1097.1998.tb02479.x] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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27
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Fu Y, Sima PD, Kanofsky JR. Singlet-Oxygen Generation from Liposomes: A Comparison of 6β-Cholesterol Hydroperoxide Formation with Predictions from a One-Dimensional Model of Singlet-Oxygen Diffusion and Quenching. Photochem Photobiol 1996. [DOI: 10.1111/j.1751-1097.1996.tb03071.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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28
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Fu Y, Kanofsky JR. SINGLET OXYGEN GENERATION FROM LIPOSOMES: A COMPARISON OF TIME-RESOLVED 1270 NM EMISSION WITH SINGLET-OXYGEN KINETICS CALCULATED FROM A ONE DIMENSIONAL MODEL OF SINGLET-OXYGEN DIFFUSION and QUENCHING. Photochem Photobiol 1995. [DOI: 10.1111/j.1751-1097.1995.tb08718.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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29
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Hoebeke M. The importance of liposomes as models and tools in the understanding of photosensitization mechanisms. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1995; 28:189-96. [PMID: 7623183 DOI: 10.1016/1011-1344(95)07132-l] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The various applications of liposomes in understanding photosensitization are described in this paper, with particular emphasis on the various kinds of information that these models allow to obtain in phototherapy. Liposomes are simple vesicles in which an aqueous phase is enclosed by a phospholipidic membrane. They are suitable models mimicking specific situations occurring in vivo and they allow study of the influence of physicochemical, photobiological and biochemical factors on the uptake of photosensitizers by tissues, their mechanisms of action and the subsequent photoinduced tumor necrosis. Moreover, solubilization of the sensitizer into the bilayer seems to improve its tumoral selectivity and its photodynamic efficiency.
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Affiliation(s)
- M Hoebeke
- Laboratory of Experimental Physics, University of Liège, Belgium
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30
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Hoebeke M, Vorst AVD. RESEARCH NOTE ON THE CHARGE-TRANSFER PATHWAY IN THE MEROCYANINE 540 TRIPLET STATE QUENCHING BY NITROXYL RADICAL. Photochem Photobiol 1995. [DOI: 10.1111/j.1751-1097.1995.tb08620.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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31
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Šikurová L, Čunderlíková B, Turisová J, Waczulíková I. Interaction of merocyanine 540 with cations of physiological solutions. Anal Chim Acta 1995. [DOI: 10.1016/0003-2670(94)00390-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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32
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Onganer Y, Quitevis EL. Dynamics of merocyanine 540 in model biomembranes: photoisomerization studies in small unilamellar vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1192:27-34. [PMID: 8204647 DOI: 10.1016/0005-2736(94)90139-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The fluorescence lifetime, tau f, of merocyanine 540 (MC540) in small unilamellar vesicles was measured as a function of temperature and cholesterol content by using phase modulation fluorometry. These vesicles were formed by probe sonication of aqueous suspensions of egg phosphatidylcholine (PC) and cholesterol. The fluorescence lifetime of MC540 in these vesicles decreased with increasing temperature, but was independent of cholesterol. The decrease in tau f with temperature is attributed to trans-cis photoisomerization. At low temperatures, the inverse of tau f, or the fluorescence rate constant, kf, approaches a constant value of 0.45 +/- 0.02 ns-1, which corresponds to the value of the radiative rate constant, kr, of the dye. The photoisomerization rate constant, kiso, was obtained by subtracting kr from kf. The temperature dependence of kiso is well described by an Arrhenius equation, with an activation energy of 31.5 +/- 0.9 kJ mol-1. This Arrhenius behavior is rationalized in terms of the Smoluchowski limit for the Kramers theory for activated barrier crossing. The electronic spectra and kiso for MC540 in these vesicles are consistent with the dye being located in the polar headgroup region of the lipid bilayer.
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Affiliation(s)
- Y Onganer
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock 79409
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Krieg M, Bilitz JM, Srichai MB, Redmond RW. Effects of structural modifications on the photosensitizing properties of dialkylcarbocyanine dyes in homogeneous and heterogeneous solutions. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1199:149-56. [PMID: 8123664 DOI: 10.1016/0304-4165(94)90110-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The photophysical characterization of structurally modified symmetric dialkylthiacarbocyanine dyes in homogeneous and biomimetic media is reported. The aim of the two specific structural modifications was to increase singlet oxygen production, hence enhancing the photosensitizing properties of these cyanine dyes. Specifically, (1) the sulfur was exchanged with selenium in order to enhance intersystem crossing via an internal heavy atom effect and (2) substituents of differing size were introduced into the meso-position of the polymethine chain to reduce photoisomerization. The result of incorporation of an internal heavy atom (selenium) into the structure of the dye yields the expected effect: this modification results in a 22-fold increase in the rate of intersystem crossing, but does not change the remaining competing deactivation rates of the first excited singlet state. As a consequence, singlet oxygen quantum yields increase from 0.001 to 0.014 in ethanol and from 0.006 to 0.08 in unilamellar liposomes. In the case of the meso-substituted thiacarbocyanine dyes, a significant reduction in photoisomerization is indeed observed. However, this modification drastically enhances internal conversion which then becomes the main deactivation pathway of the first excited singlet state. As a result, very small fluorescence and singlet oxygen quantum yields are obtained, e.g. 0.006 and 0.001, respectively, in ethanol.
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Affiliation(s)
- M Krieg
- Pediatrics Department, MACC Fund Research Center, Medical College of Wisconsin, Milwaukee 53226
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Hoebeke M, Enescu M, Lindqvist L. Quenching of merocyanine 540 triplet state by nitroxyl radicals in liposomal systems: a laser flash photolysis study. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1994; 22:229-33. [PMID: 8014755 DOI: 10.1016/1011-1344(93)06967-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Laser flash photolysis experiments were undertaken to investigate the interaction between stearic acid nitroxide spin probes and photoexcited merocyanine 540 (MC540) in dimyristoyl-L-alpha-phosphatidylcholine liposomes (membrane model). The measurements of the paramagnetic signal decay kinetics of four different spin-labelled stearic acids (n-DSA) show that the direct interaction between the dye and the probe is affected by the position of the nitroxyl group along the carbon chain. Laser flash photolysis results reveal a significant decrease in the MC540 triplet lifetime in the presence of n-DSA, the effect depending on the depth at which the nitroxyl moiety is localized in the bilayer. Previous results on the rate of disappearance of the electron spin resonance (ESR) nitroxide signal on continuous photolysis of the same systems do not show the same dependence on the localization of the nitroxyl moiety in the liposome. Although the MC540 triplet state seems to be implicated in the reaction process, the results suggest that ESR and laser flash experiments demonstrate two different kinds of mechanism.
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Affiliation(s)
- M Hoebeke
- Laboratory of Experimental Physics, University of Liège, Belgium
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35
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Krieg M. Determination of singlet oxygen quantum yields with 1,3-diphenylisobenzofuran in model membrane systems. JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 1993; 27:143-9. [PMID: 8227944 DOI: 10.1016/0165-022x(93)90058-v] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The oxidation of 1,3-diphenylisobenzofuran by singlet oxygen was investigated in methanol and in two different types of liposomes. It was found that at high concentrations of scavenger 1,3-diphenylisobenzofuran, e.g., > 100 microM in methanol, the 1:1 oxidation stoichiometry is lost and more than one scavenger molecule per molecule of singlet oxygen is consumed. In model membrane systems, where local scavenger concentrations are high due to compartmentalization, correct singlet oxygen quantum yields with 1,3-diphenylisobenzofuran are only determined if the increased oxidation is taken into account.
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Affiliation(s)
- M Krieg
- Department of Pediatrics, MACC Fund Research Center, Medical College of Wisconsin, Milwaukee 53226
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36
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Krieg M. Singlet oxygen production and fluorescence yields of merocyanine 540: a comparative study in solution and model membrane systems. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1105:333-5. [PMID: 1586670 DOI: 10.1016/0005-2736(92)90212-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Singlet oxygen and fluorescence quantum yields of merocyanine 540 were measured in solution (methanol, ethanol, n-heptanol) and in model membrane systems (cationic micelles, unilamellar dimyristoyl- and dipalmitoylphosphatidylcholine vesicles). Both singlet oxygen quantum yields and fluorescence quantum yields increase with increasing viscosity/rigidity of the surrounding medium: the yield of singlet oxygen production (24 degrees C) goes from 0.002 in methanol to 0.04 in dipalmitoylphosphatidylcholine vesicles, and fluorescence yields (25 degrees C) change from 0.14 to 0.61 in the same media. The data are consistent with previous findings that photoisomerization is in direct competition with intersystem crossing and radiative relaxation. Therefore, a singlet oxygen yield close to the maximum value of 0.11 can only be achieved after both photoisomerization and internal conversion are prevented by a highly viscous environment.
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Affiliation(s)
- M Krieg
- Department of Pediatrics, MACC Fund Research Center, Medical College of Wisconsin, Milwaukee 53226
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