&lt;title&gt;Significance of threshold doses for photodynamic therapy of melanotic and amelanotic tumors&lt;/title&gt;

Moser, Joerg G.; Suchomski, R.; Danielowski, Till; Wagner, Birgit; Scheer, Hugo; Hartwich, G

doi:10.1117/12.203446

Cited by 4 publications

(4 citation statements)

References 5 publications

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“…This reaction sequence might be utilized for directed photosensitized destruction of tumor tissue. Excellent photodynamic behavior of a [Pd]-BChl derivative has been observed …”

Section: Resultsmentioning

confidence: 96%

“…They are responsible for the absorption of light and the transfer of excitation energy − as well as for the initial steps in transmembrane charge separation − in the reaction center of bacteria and the photosystems in plants. Apart from their key functions in photobiology, this class of pigments meets the requirements for photosensitizers in photodynamic tumor therapy (PDT). − …”

Section: Introductionmentioning

confidence: 99%

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Time-Resolved Spectral Investigation of Bacteriochlorophyll a and Its Transmetalated Derivatives [Zn]-Bacteriochlorophyll a and [Pd]-Bacteriochlorophyll a

et al. 1998

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The lowest excited singlet (S1) and triplet (T1) states of bacteriochlorophyll a (BChl) and its central metal derivatives [Zn]- and [Pd]- BChl were investigated by femtosecond time-resolved absorption and fluorescence spectroscopy. In contrast to previously reported dynamic solvation effects on the picosecond time scale for BChl, no short kinetic components were observed for BChl and [Zn]-BChl provided that photochemical transformations of the pigments caused by multiple excitation are avoided. The S1 lifetimes of 2.6 ns, 2.1 ns, and 65 ps for BChl, [Zn]-BChl and [Pd]-BChl, respectively, are dominated by intersystem crossing (ISC) to the triplet state T1. The respective triplet quantum yields amount to 76%, 85%, and >99%. The data support that [Pd]-BChl is a highly efficient photosensitizer for photodynamic tumor therapy.

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“…This reaction sequence might be utilized for directed photosensitized destruction of tumor tissue. Excellent photodynamic behavior of a [Pd]-BChl derivative has been observed …”

Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Time-Resolved Spectral Investigation of Bacteriochlorophyll a and Its Transmetalated Derivatives [Zn]-Bacteriochlorophyll a and [Pd]-Bacteriochlorophyll a

et al. 1998

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“…They act as light-harvesting or as redox pigments enabling light-induced charge separation within the reaction center . The pigments are also potentially useful photosensitizers, e.g., in photodynamic tumor therapy. − Complexes of cyclic tetrapyrroles with metals other than Mg were studied in the chlorin , (17,18-dihydroporphyrin) and especially in the porphyrin − series to better understand their spectroscopic and redox properties. These complexes show a linear relationship between the electronegativity ( ; Pauling values) of the central metal and the redox potential…”

Section: Introductionmentioning

confidence: 99%

Metal-Substituted Bacteriochlorophylls. 1. Preparation and Influence of Metal and Coordination on Spectra

et al. 1998

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In contrast to porphyrins and chlorins, the direct metalation of bacteriochlorins is difficult. Nevertheless, Cu2+ and Zn2+ can be introduced into bacteriopheophytin in acetic acid, whereas Cd2+ can be inserted in dimethylformamide. The former reactions depend on the substituents of the isocyclic ring: they are facilitated if enolization of the β-ketoester system is inhibited. Starting with [Cd]-bacteriochlorophyll-a or its 132-hydroxy derivative, a series of metallo-bacteriochlorins with central divalent ions Pd2+, Co2+, Ni2+, Cu2+, Zn2+, and Mn2+ have been obtained by transmetalation. Like in the parent Mg complex, the four principal optical transitions are well-separated in these complexes, and their responses to changes in the central metal and its coordination state can be followed in detail. The energies of the Q y and B x transitions are almost independent of the central metal, whereas the Q x and B y transition energies change significantly, depending on the central metal as well as the presence of additional axial ligands. If the complexes are grouped by their coordination number, empirical linear correlations exist between these shifts and the ratio / , where is Pauling's electronegativity value and is the ionic radius of the metal. A similar correlation was found for those 1H NMR signals influenced mainly by the ring current and for the redox potentials. This observation was in contrast with the linear relationships with alone, found for metal-substituted porphyrins. The spectral variations influenced by the central metal and its state of ligation are attributed, within the framework of the four-orbital model, to the electrostatic interaction of the electron densities in the four orbitals with the effective charge of the central metal ions, which is most pronounced for the a2u orbital (HOMO-1). Ligation studies have revealed that addition of the first axial ligand decreases the effective charge of the central metal by approximately 50% and addition of the second axial ligand by another 20% with respect to the absence of axial ligands. The singlet−triplet splitting deduced from fluorescence and phosphorescence measurements is similar for [Pd]-, [Cu]-, [Zn]-, and [Mg]-BChl (4550 ± 100 cm-1).

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“…The knowledge of the electronic properties of bacteriochlorophylls is a basic requirement for the understanding of functional modification of light-harvesting and primary charge separation processes in bacterial photosynthesis − and for their potential application as photosensitizer in PDT. − In this context, metal-substituted derivatives of bacteriochlorophyll a ([M]-BChl) − are of particular relevance. They have been introduced into the photosynthetic reaction center of Rhodobacter sphaeroides replacing the accessory pigments. − Reaction centers containing [Ni]-BChl show a significant loss channel for the ultrafast energy transfer from the excited [Ni]-BChl to the primary donor .…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Photophysics and Photochemistry of [Ni]-Bacteriochlorophyll a

et al. 1999

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The ultrafast photodynamics of bacteriochlorophyll with the central Mg2+-ion replaced by Ni2+ ([Ni]-BChl) in toluene and pyridine have been studied by femtosecond time-resolved fluorescence and absorption spectroscopy with a time resolution of 100 fs in the spectral range of 470−900 nm. Excitation of tetracoordinated [Ni]-BChl in toluene in its red-most absorption band leads to four transient states which decay single-exponentially with lifetimes of 100 fs, 450 fs, 4 ps, 25 ps. Except for the 4 ps component these kinetics arise from an internal conversion cascade conserving the overall multiplicity of the singlet configuration. The spectral characteristics of the intermediates indicate a deactivation process via several π- and metal-centered excited states. The 4 ps kinetic results from a relaxation within the metal d-states caused by a change of size of the central nickel ion upon electronic excitation. A different deactivation pattern is observed for [Ni]-BChl in pyridine, where the central metal is additionally coordinated by two axial solvent molecules. On the basis of their dynamics and their spectral positions, three different intermediates have been identified. The fastest decay with 150 fs reflects an internal conversion process. This is followed by a process that can be approximately described by time constants of 6 and 90 ps. This decay pattern, concomitant with the spectral changes, is attributed to the ejection of the axial solvent ligands accompanied by intersystem crossing. The slowest component has a characteristic time of >2 ns and is attributed to the rebinding of the pyridine ligands.

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<title>Significance of threshold doses for photodynamic therapy of melanotic and amelanotic tumors</title>

Cited by 4 publications

References 5 publications

Time-Resolved Spectral Investigation of Bacteriochlorophyll a and Its Transmetalated Derivatives [Zn]-Bacteriochlorophyll a and [Pd]-Bacteriochlorophyll a

Time-Resolved Spectral Investigation of Bacteriochlorophyll a and Its Transmetalated Derivatives [Zn]-Bacteriochlorophyll a and [Pd]-Bacteriochlorophyll a

Metal-Substituted Bacteriochlorophylls. 1. Preparation and Influence of Metal and Coordination on Spectra

Ultrafast Photophysics and Photochemistry of [Ni]-Bacteriochlorophyll a

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