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Shiho Hirohara,
Yuji Kawasaki,
Ryota Funasako,
Nobutaka Yasui,
Masayasu Totani,
Hiroki Alitomo,
Junpei Yuasa,
Tuyoshi Kawai,
Chio Oka,
Masashi Kawaichi, Makoto Obata,
Masao Tanihara
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ABSTRACT: Palladium(II) complexes of glycoconjugated porphyrin and pyrrolidine-fused chlorin were prepared to examine sugar and heavy atom effects on in vitro photocytotoxicity. Cellular uptake into HeLa cells was enhanced by introducing sugar units regardless of other features, such as the central ion (free base or palladium(II) ion) and the ring structure (porphyrin or chlorin). The palladium(II) complex of glycoconjugated pyrrolidine-fused chlorin (PdPC2) exerted an excellent degree of photocytotoxicity not only on HeLa cells, but also on metastatic B16-BL6 cells, weakly metastatic B16F1 cells, and metastatic 4T1 cells. However, free-base glycoconjugated pyrrolidine-fused chlorin (PC2) also exerted similar or much higher photocytotoxicity rather than PdPC2. Therefore, the palladium(II) ion did not improve the in vitro photocytotoxicity of PC2. The enhanced singlet oxygen generation of palladium(II) complexes (i.e., the heavy atom effect) was confirmed at least in O(2)-saturated D(2)O. In addition, the formation of hydrogen peroxide and hydroxyl radical were also detected in O(2)-saturated phosphate buffered saline. However, the reactive oxygen species (ROS) generation efficiency, which is the product of the (relative) quantum yield of each ROS and the light absorbing ability, did not fit the trends of photocytotoxicity seen for the photosensitizers. In our glycoconjugated photosensitizers tested, the best indicator of the photocytotoxicity was found to be the light absorbing ability (namely, the oscillator strength in the wavelength region applied in the photocytotoxicity test). These results indicated that photochemical characteristics of glycoconjugated photosensitizers were notably susceptible to the microenvironment. The biological characteristics, such as the sugar effect, were a much more reliable approach to improving the photocytotoxicity of photosensitizers.
Bioconjugate Chemistry 09/2012; 23(9):1881-90. · 4.93 Impact Factor
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Shigenobu Yano,
Hiromi Ohi,
Mizue Ashizaki, Makoto Obata,
Yuji Mikata,
Rika Tanaka,
Takanori Nishioka,
Isamu Kinoshita,
Yuko Sugai,
Ichiro Okura,
Shun-Ichiro Ogura,
Justyna A Czaplewska,
Michael Gottschaldt,
Ulrich S Schubert,
Takuzo Funabiki,
Keiko Morimoto,
Misaki Nakai
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ABSTRACT: Four platinum(II) and palladium(II) complexes with sugar-conjugated bipyridine-type triazole ligands, [Pt(II) Cl(2) (AcGlc-pyta)] (3), [Pd(II) Cl(2) (AcGlc-pyta)] (4), [Pt(II) Cl(2) (Glc-pyta)] (5), and [Pd(II) Cl(2) (Glc-pyta)] (6), were prepared and characterized by mass spectrometry, elemental analysis, (1) H- and (13) C-NMR, IR as well as UV/VIS spectroscopy, where AcGlc-pyta and Glc-pyta denote 2-[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]ethyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside (1) and 2-[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]ethyl β-D-glucopyranoside (2), respectively. The solid-state structure of complex 6 was determined by single-crystal X-ray-diffraction analysis. These complexes exhibited in vitro cytotoxicity against human cervix tumor cells (HeLa) though weaker than that of cisplatin.
Chemistry & Biodiversity 09/2012; 9(9):1903-15. · 1.80 Impact Factor
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ABSTRACT: a b s t r a c t One of the long-standing goals of both researchers and oncologists is to establish a framework for the complete cure of cancer with less toxic adverse effect and improved quality of life (QOL) for patients. PDT (photodynamic therapy) has much attracted as less invasive method for treating cancer. The therapeu-tic properties of light have been known for thousands of years, but it was only in the last century that PDT was developed. The field on PDT is now so large. Here, we will focus on a few basic aspects such as porphyrinoid photosensitizers, non-porphyrinoid photosensitizers, 5-aminolevulinic acid and its deriva-tives, fullerenes as efficient photosensitizers, and, PDT and photodynamic diagnosis (PDD) for digestive cancer from the point of view of a clinical doctor, and, finally, future trends.
Journal of Photochemistry and Photobiology C Photochemistry Reviews 01/2011; 12:46-67. · 10.36 Impact Factor
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Chunhong Zhang,
Xiande Shen,
Ryosuke Sakai,
Michael Gottschaldt,
Ulrich S. Schubert,
Shiho Hirohara,
Masao Tanihara,
Shigenobu Yano, Makoto Obata,
Nao Xiao,
Toshifumi Satoh,
Toyoji Kakuchi
Journal of Polymer Science Part A Polymer Chemistry 12/2010; 49(3):746 - 753. · 3.92 Impact Factor
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ABSTRACT: Cisplatin analogue complexes with platinum(II) and palladium(II) starting from 3',5'-diamino-3',5'-dideoxy-thymidines were synthesized, both with the D-erythro- and D-threo configurations. Complexes of the general formula [MCl(2)L] were obtained and characterized. NMR spectroscopic measurements and single crystal X-ray structure analysis showed that the metal centers are coordinated to the ligands by the amino groups in 3'- and 5'-positions and not through the thymine moiety. All ligands and complexes showed no significant in vitro activities except thymiplatin (cis-dichloro(3',5'-diamino-3',5'-dideoxy-D-threo-thymidine)platinum(II)). Detailed in vitro studies on the apoptosis pathway in lymphoma (BJAB), leukemia (NALM-6), and melanoma cells (Mel-HO) as well as on transfected or resistant cell lines were carried out. Thymiplatin significantly induced an apoptotic response, which was found to be associated with the loss of mitochondrial membrane potential and with caspase activation. The activity was shown to be independent of Fas-associated protein with death domain (FADD), but dependent on Bcl-2 expression. As a consequence, for thymiplatin a mitochondrial mode of action could be assigned. Moreover, the compound showed activity in cells resistant to common drugs, such as daunorubicin and vincristin, and showed synergistic effects with doxorubicin, vincristin, cytarabin, and daunorubicin.
Chemistry 10/2010; 16(48):14498-505. · 5.93 Impact Factor
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ABSTRACT: In order to explore the effect of substitution patterns on the photocytotoxicity of glycoconjugated porphyrins, we synthesized and characterized a 'complete set' of tetrakis(perfluorophenyl)porphyrins having beta-d-glucopyranosylthio groups on the phenyl ring. Among five possible derivatives, trans-substituted S-glucosylated porphyrin trans-2(OH) exerted outstanding photocytotoxicity (EC(50) value was < 5 nM) in HeLa cells. The excellent photocytotoxicity of trans-2(OH) was found to be attributable to several factors, namely high optical transition probability in aqueous media, efficient type I photoreactions and enhanced cellular uptake.
Bioorganic & medicinal chemistry 02/2010; 18(4):1526-35. · 2.82 Impact Factor
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Journal of Polymer Science Part A Polymer Chemistry 12/2009; 48(3):663 - 670. · 3.92 Impact Factor
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ABSTRACT: Reactions of cis-diamminedichloroplatinum(II) (cisplatin) and 1,1-cyclobutanedicarboxylatodiammineplatinum(II) (carboplatin) with reduced glutathione, a tripeptide that is abundant in cells, were studied by means of X-ray absorption spectroscopy. Back-scattering amplitudes F(i)(k) and phase shifts Phi(i)(k) were theoretically derived, and validated by applying them to calculate extended X-ray absorption fine structure (EXAFS) oscillations of cisplatin and K(2)[Pt(SCN)(4)] in the solid state. EXAFS oscillations of reaction mixtures of cisplatin or carboplatin with reduced glutathione were fitted to the standard EXAFS equation using the F(i)(k) and Phi(i)(k) functions to give the coordination numbers of N or O atoms (N(N/O)) and of Cl or S atoms (N(Cl/S)). For both cisplatin and carboplatin, the N(N/O) value decreased and the N(Cl/S) values increased monotonically as the reaction proceeded. However, the reaction rate for carboplatin was significantly slower than that for cisplatin.
Chemical & pharmaceutical bulletin 10/2009; 57(10):1107-9. · 1.70 Impact Factor
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ABSTRACT: The action of C60 fullerene and its derivatives as a radical-scavenging antioxidant has received much attention, but their reactivity toward free radicals and antioxidant capacity have not been well elucidated yet. In the present study, the reactivity of the two types of water-soluble, sugar-pendant C60 fullerenes, C60-1S and C60-2S, toward peroxyl radical and their effect against human plasma lipid peroxidation were measured. The rate constants for the reaction of C60-1S and C60-2S with peroxyl radicals were obtained from their effect on the bleaching of beta-carotene in lipid-SDS micelle system as 4.6 x 10(3) and 8.0 x 10(3) M(-1) s(-1) at 37 degrees C, respectively. They inhibited the free radical-induced lipid peroxidation in human plasma in a concentration-dependent manner. These results suggest that the sugar-pendant fullerenes C60-1S and C60-2S act as a radical-scavenging antioxidant with the activity similar to the phenolic antioxidants.
Bioorganic & medicinal chemistry letters 09/2009; 19(20):5902-4. · 2.65 Impact Factor
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ABSTRACT: Eight S-glycosylated 5,10,15,20-tetrakis(tetrafluorophenyl)porphyrins (1a', 1b', 1a and 1b (a: S-glucosylated, b: S-galactosylated)) and their 1,3-dipolar cycloadducts, i.e. chlorins 2a', 2b', 2a and 2b were prepared by nucleophilic substitution of the pentafluorophenyl groups with S-glycoside. These photosensitizers were characterized by (1)H, (13)C and (19)F NMR spectroscopies and elemental analysis. The photocytotoxicity of the S-glycosylated photosensitizers and the parent porphyrin (1) and chlorin (2) was examined in HeLa cells. Photosensitizers 1, 2, 1a', 1b', 2a' and 2b' showed no significant photocytotoxicity at the concentration of 0.5microM, while the deprotected photosensitizers 1a, 1b, 2a and 2b were photocytotoxic. The strong inhibition by sodium azide of the photocytotoxicity of these photosensitizers suggested that (1)O(2) is the main mediator. The S-glucosylated photosensitizers 1a and 2a showed higher photocytotoxicity than S-galactosylated 1b and 2b, respectively. The cellular uptake of 1a and 2a increased up to 24h, while that of 1b and 2b was saturated by 12h.
Journal of photochemistry and photobiology. B, Biology 08/2009; 97(1):22-33. · 1.87 Impact Factor
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ABSTRACT: 5,10,15,20-Tetrakis(4-(2,3,4,6-tetra-O-acetyl-beta-d-glucopyranosylthio)-2,3,5,6-tetrafluorophenyl)porphyrin 2a and its Zn(II), Pd(II), and Pt(II) complexes 2b, 2c, and 2d were prepared in excellent yields by nucleophilic substitution of the corresponding free-base porphyrin and metalloporphyrins with acetyl 2,3,4,6-tetra-O-acetyl-1-thio-beta-d-glucopyranoside. Deprotection of 2a, 2b, 2c, and 2d by alkaline hydrolysis afforded the corresponding S-glucosylated porphyrin 3a and its metal complexes 3b, 3c, and 3d. The structures and purity of all new photosensitizers were confirmed by elemental analysis and (1)H, (13)C, and (19)F NMR, UV-vis, and steady-state luminescence spectroscopy. The relative efficiency of singlet oxygen ((1)O(2)) production increased in the order of free-base fluoroporphyrins (2a and 3a) < Zn(II) complexes (2b and 3b) < Pd(II) complexes (2c and 3c), which can be explained in terms of the heavy-atom effect, while the (1)O(2)-producing efficiency of Pt(II) complexes (2d and 3d) were exceptionally low. In vitro photocytotoxicity of these eight S-glucosylated photosensitizers was examined in HeLa cells. Although all protected photosensitizers 2a, 2b, 2c, and 2d showed no photocytotoxicity, the photosensitizers 3a, 3b, and 3c exerted potent photocytotoxicity. These results clearly indicated that the sugar moieties of 3a, 3b, and 3c act as not only water-solubility-enhancing functionalities but also cellular-uptake-enhancing elements. Photocytotoxicity testing of 3a, 3b, and 3c in the presence of reactive oxygen species inhibitors suggested that (1)O(2) is the major mediator of cell death. Hence, the Zn(II) and Pd(II) complexes 3b and 3c are promising photosensitizers having cellular uptake-facilitating units (sugar moieties) and enhanced (1)O(2) generation due to the heavy-atom effect.
Bioconjugate Chemistry 05/2009; 20(5):944-52. · 4.93 Impact Factor
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ABSTRACT: Introduction of a heavy atom into photosensitizers generally facilitates intersystem crossing and improves the quantum yield (Phi(Delta)) of singlet oxygen ((1)O(2)), which is a key species in photodynamic therapy (PDT). However, little information is available about the physiological importance of this heavy-atom effect. The aim of this study is to examine the heavy-atom effect in simple metallochlorins in vitro at the cellular level. 1,3-Dipolar cycloaddition of azomethine ylide to 5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato palladium(II) and platinum(II) afforded metallochlorins 4b and 4c in yields of 17.1 and 12.9%, respectively. The Phi(Delta) values increased in the order of 4a (0.28) < 4b (0.89) < 4c (0.92) in C(6)D(6). The photocytotoxicity of 4a, 4b, and 4c was evaluated in HeLa cells at a light dose of 16 J x cm(-2) with lambda > 500 nm and increased in the order of 4a < 4b < 4c at the concentration of 0.5 microM. The photocytotoxicity of 4b and 4c was significantly inhibited by addition of sodium azide, but not D-mannitol, suggesting that (1)O(2) is the major species causing cell death. Our results clearly indicate that 4b and 4c act as efficient (1)O(2) generators due to the heavy-atom effect in a cellular microenvironment as well as in nonphysiological media.
Journal of Medicinal Chemistry 05/2009; 52(9):2747-53. · 4.80 Impact Factor
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ABSTRACT: The photodynamic effect of the glycoconjugated photosensitizer library containing 16 glycoconjugated 5,10,15,20-tetraphenylporphyrins and 8 glycoconjugated 5,10,15,20-tetraphenylchlorins were examined in HeLa cells, and analyzed by two approaches, namely, physiological properties (cellular uptake and reactive oxygen species (ROS)) and structural features of glycoconjugated photosensitizers. All glycoconjugated photosensitizers showed no cytotoxicity in the dark at a concentration of 5 muM. The photocytotoxicity profiles poorly related to the amount of cellular uptake of the photosensitizers. Photocytotoxicities of the glycoconjugated photosensitizers were inhibited by the ROS inhibitor, sodium azide. The result clearly suggests that singlet oxygen is a dominant species in all cases. The glycoconjugated photosensitizers examined have three structural features, namely, (1) the kind of sugar moieties, (2) the kind of light-absorbing moiety and (3) the substitution position of the sugar moiety. In regard to the sugar moieties, the photosensitizers bearing D-xylose tend to show higher photocytotoxicity than other photosensitizers, while those bearing D-arabinose tend to show lower photocytotoxicity. The photocytotoxicity with respect to the light-absorbing moiety tends to increase in the order of zinc porphyrin<porphyrin<chlorin. The optical density at the Q(I) band fairly explained the results. As an effect of the substitution position of the sugar moieties, the photosensitizers bearing sugar moieties at the meta-position of phenyl group showed remarkably high activity compared with para-substituted ones, and the difference could not be explained by the optical density. Confocal laser scanning microscopy revealed that the meta-substituted photosensitizers are not readily deactivated from the excited state in the cellular microenvironment, and this may explain their potent photocytotoxicity.
Biological & Pharmaceutical Bulletin 01/2009; 31(12):2265-72. · 1.66 Impact Factor
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Makoto Obata,
Asuka Kitamura,
Akemi Mori,
Chiaki Kameyama,
Justyna A Czaplewska,
Rika Tanaka,
Isamu Kinoshita,
Toshiyuki Kusumoto,
Hideki Hashimoto,
Masafumi Harada,
Yuji Mikata,
Takuzo Funabiki,
Shigenobu Yano
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ABSTRACT: Novel chelators, i.e., 4-(2-pyridyl)-1,2,3-triazole derivatives, were synthesized by means of Cu(I)-catalyzed 1,3-dipolar cycloaddition and used to prepare luminescent Re(I) complexes [ReCl(CO)(3)(Bn-pyta)], [ReCl(CO)(3)(AcGlc-pyta)] and [ReCl(CO)(3)(Glc-pyta)] (Bn-pyta = 1-benzyl-4-(2-pyridyl)-1,2,3-triazole, AcGlc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl 2,3,4,6-tetra-O-acetyl-beta-d-glucopyranoside, Glc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl beta-d-glucopyranoside). X-Ray crystallography of Bn-pyta and Glc-pyta indicated an azocompound-like structure while the 1,2,4-triazole isomer has an azine character. [ReCl(CO)(3)(Bn-pyta)] crystallized in the monoclinic system with space group P2(1)/n. Bn-pyta ligand coordinates with the nitrogen atoms of the 2-pyridyl group and the 3-position of 1,2,3-triazole ring, which is a very similar coordinating fashion to that of the 2,2'-bipyridine derivative. The glucoconjugated Re(I) complexes [ReCl(CO)(3)(AcGlc-pyta)] and [ReCl(CO)(3)(Glc-pyta)] hardly crystallized, and were analyzed by applying extended X-ray absorption fine structure (EXAFS) analysis. The EXAFS analyses suggested that the glucoconjugation at the 1-position of the 1,2,3-triazole makes no influence to the coordinating fashion of 4-(2-pyridyl)-1,2,3-triazole. [ReCl(CO)(3)(Bn-pyta)] showed a blue-shifted maximum absorption (333 nm, 3.97 x 10(3) M(-1) cm(-1)) compared with [ReCl(CO)(3)(bpy)] (371 nm, 3.35 x 10(3) M(-1) cm(-1)). These absorptions were clearly assigned to be the mixed metal-ligand-to-ligand charge transfer (MLLCT) on the basis of time-dependent density functional theory calculation. The luminescence spectrum of [ReCl(CO)(3)(Bn-pyta)] also showed this blue-shifted feature when compared with that of [ReCl(CO)(3)(bpy)]. The luminescence lifetime of [ReCl(CO)(3)(Bn-pyta)] was determined to be 8.90 mus in 2-methyltetrahydrofuran at 77 K, which is longer than that of [ReCl(CO)(3)(bpy)] (3.17 micros). The blue-shifted electronic absorption and elongated luminescence lifetime of [ReCl(CO)(3)(Bn-pyta)] suggested that 4-(2-pyridyl)-1,2,3-triazole functions as an electron-rich bidentate chelator.
Dalton Transactions 08/2008; · 3.84 Impact Factor
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ABSTRACT: Practical and convenient preparations of C-glycosyl 1,2- and 1,3-alkanediamines are described. Two 1,2-ethylenediamine derivatives were synthesized from acetylated allyl alpha-C-glycosyl compounds via dibromination, azidation, carbohydrate deprotection, and azide reduction. Four 1,3-propanediamine derivatives were prepared from acetylated sugar halides via C-glycosylation with sodiomalononitrile, followed by the reduction of the nitrile moieties and the deacetylation of the carbohydrate moiety. These 1,3-propanediamine derivatives have the beta-anomeric configurations. The methods reported here serve as general routes to access carbohydrate-diamine conjugates with C-glycosyl linkages.
Carbohydrate Research 05/2008; 343(5):941-50. · 2.33 Impact Factor
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ABSTRACT: The title compound, {[Ag(L)]PF(6))(n) {L is tris-[2-(4-phenyl-1,2,3-triazol-1-yl)eth-yl]amine, C(30)H(30)N(10)}, consists of alternating two-dimensional cationic layers of [Ag(L)](+) and anionic PF(6) (-) layers. Each Ag(I) atom is three coordinated in a T-shaped geometry by three N atoms from three ligands. Each ligand links three Ag(I) atoms, generating a two-dimensional network structure with two different metallacycles, A and B. In A, eight coordination units from four ligands connect four Ag(I) atoms, forming a 48-membered ring. In B, four coordination units from two ligands link two Ag(I) atoms, forming a 24-membered ring. Each B ring is surrounded by four A rings, and each A ring has four A and four B rings as neighbours. This cationic layer thus generates a 4.8(2) topology network, with each Ag(I) centre and ligand acting as a three-connected topological node.
Acta Crystallographica Section E Structure Reports Online 01/2008; 64(Pt 10):m1256-7. · 0.35 Impact Factor
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ABSTRACT: The photocytotoxicity of four glycoconjugated porphyrins, namely 5,10,15,20-tetrakis[4-(beta-D-glucopyranosyloxy)phenyl]porphyrin (p-1a), 5,10,15,20-tetrakis[4-(beta-D-galactopyranosyloxy)phenyl]porphyrin (p-1b), 5,10,15,20-tetrakis[4-(beta-D-xylopyranosyloxy)phenyl]porphyrin (p-1c) and 5,10,15,20-tetrakis[4-(beta-D-arabinopyranosyloxy)phenyl]porphyrin (p-1d), was evaluated in HeLa cells in the concentration range from 1 to 7 microM using a light dose of 16 J x cm(-2) with a wavelength greater than 500 nm. The photocytotoxicity depends on the sugar moieties, and increases in the order of p-1d<p-1a<p-1b<p-1c. The order of the photocytotoxicity is at variance with that of the cellular uptake reported previously. On the other hand, the photophysical properties of the glycoconjugated porphyrins also depends on the sugar moieties in physiological media such as phosphate buffered saline (PBS) containing 10 wt.% bovine serum albumin (BSA). In particular, the oscillator strength in the range above 500 nm increases in the order of p-1d=p-1a<p-1c<p-1b, which is good agreement with the order of the photocytotoxicity in HeLa cells. The interaction between the glycoconjugated porphyrins and BSA was evaluated by means of electronic absorption, fluorometric and circular dichroic (CD) titrations. Fluorometric titration showed no differences in the apparent binding constants, K, between the glycoconjugated porphyrins p-1a, p-1b, p-1c and p-1d. On the other hand, the number of binding sites, n, depends on the sugar moieties of the glycoconjugated porphyrin, and increases in the order of p-1b<p-1a<p-1d<p-1c. CD titration was also characterized by the n value determined by fluorometric titration, suggesting the n value is a good descriptor for the interaction between glycoconjugated porphyrins and BSA. However, it was found that the n value was poorly related to the photophysical properties in physiological media and the photocytotoxicity. Even though the role of the sugar moieties on the photodynamic effect is not fully understood, the photophysical properties of the glycoconjugated porphyrins are strongly modulated by the physiological media resulting in the sugar-dependent photocytotoxicity.
Biochimica et Biophysica Acta 08/2007; 1770(8):1204-11. · 4.66 Impact Factor
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ABSTRACT: An optical oxygen-sensing activity of anchored porphyrin derivatives on ordered porous aluminium oxide plates was studied in relevance to development of new oxygen-sensing systems. Porphyrin derivatives, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy)porphyrin, 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl]porphyrin, 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrin, and their platinum complexes, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy)porphyrinatoplatinum(II), 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl]porphyrinatoplatinum(II), 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrinatoplatinum(II), were synthesized and anchored by an equilibrium adsorption method on aluminium oxide plates, which were prepared by an anodic oxidation. The excitation spectra of the porphyrin-anchored layers showed a broadened and blue-shifted Soret band compared with the corresponding porphyrins in DMSO. The luminescence intensity decreased with increasing oxygen concentrations. The oxygen-sensing ability estimated from I(0)/I(100) (I(0) and I(100) denote the luminescence intensity in 0 and 100% oxygen) was 9.08, 6.78, 8.71, 81.9, 35.5, and 39.1, which are greater than those of corresponding porphyrin derivatives in DMSO under the measured conditions, and indicates the remarkable enhancement effect of platinum(II). Non-linear Stern-Volmer plots were well fitted by the two component system to give the oxygen-sensitive constant (K(SV1)/%(-1)), the oxygen-insensitive constant (K(SV2)/%(-1)), and the former contribution (f(1)): 0.232, 3.32 x 10(-2), and 0.642; 0.141, 2.05 x 10(-2), and 0.687; 0.143, 1.05 x 10(-2), and 0.882; 17.3, 7.04 x 10(-3), and 0.980; 10.2, 1.43 x 10(-2), and 0.935; 16.3, 8.35 x 10(-3), and 0.954. The response time for the change of the atmospheric gas from argon to oxygen was 9.4 s, 12.5 s, 9.6 s, 5.0 s, 8.9 s, and 4.6 s, indicating the shortening effect of platinum. The reverse effect of platinum was observed in the change from oxygen to argon: 15.5 s, 17.0 s, 20.8 s, 667.4 s, 590.1 s, and 580.4 s, indicating the specific interaction of oxygen to the platinum(II) center.
Photochemical and Photobiological Sciences 08/2007; 6(7):794-803. · 2.58 Impact Factor
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Journal of Polymer Science Part A Polymer Chemistry 05/2007; 45(14):2876 - 2885. · 3.92 Impact Factor
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Ryoko Santo,
Riichi Miyamoto,
Rika Tanaka,
Takanori Nishioka,
Kazunobu Sato,
Kazuo Toyota, Makoto Obata,
Shigenobu Yano,
Isamu Kinoshita,
Akio Ichimura,
Takeji Takui
Angewandte Chemie International Edition 12/2006; 45(45):7611-4. · 13.45 Impact Factor
