Yazhou Zhang

Publications (30) View all

• Source

  Available from: Wenbing Li

  Article: Enhanced photodynamic selectivity of nano-silica-attached porphyrins against breast cancer cells

  Wenbing Li, Wentong Lu, Zhen Fan, Xianchun Zhu, Aisha Reed, Brandon Newton, Yazhou Zhang, Shavelle Courtney, Papireddy T Tiyyagura, Roslyn R Ratcliff, Shufang Li, Ebonie Butler, Hongtao Yu, Paresh C Ray, Ruomei Gao
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  ABSTRACT: The synthesis and characterization of bare silica (4 nm in diameter) nanoparticle-attached meso-tetra(N-methyl-4-pyridyl)porphine (SiO 2 –TMPyP, 6 nm in diameter) are described for pH-controllable photosensitization. Distinguished from organosilanes, SiO 2 nanoparticles were functionalized as a potential quencher of triplet TMPyP and/or singlet oxygen (1 O 2) at alkaline pH, thereby turning off sensitizer photoactivity. In weak acidic solutions, TMPyP was released from the SiO 2 surface for efficient production of 1 O 2 . By monitoring 1 O 2 luminescence at 1270 nm, quantum yields of 1 O 2 production were found to be pH-dependent, dropping from $0.45 in the pH range of 3–6 to 0.08 at pH 8–9, which is consistent with the pH-dependent adsorption behavior of TMPyP on the SiO 2 surface. These features make bare SiO 2 -attached cationic porphyrin a promising candidate for use in PDT for cancer treatment in which efficient 1 O 2 production at acidic pH and sensitizer deactivation at physiological pH are desirable. The enhanced therapeutic selectivity was confirmed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) tests and trypan blue exclusion tests of cell viability in breast cancer cell lines. Bimolecular quenching rate constants of 1 O 2 by free TMPyP, SiO 2 and SiO 2 –TMPyP nanoparticles were also determined.
  Journal of Materials Chemistry 04/2012; · 5.97 Impact Factor
• Article: Photoprocesses of merocyanine 540 bound to serum albumin and lysozyme

  Yazhou Zhang, Helmut Görner
  Journal of Molecular Structure 01/2012; · 1.63 Impact Factor
• Article: 6-Methylthiopurine: a potential sensitizer via excitation- oxidation-reduction cycles

  Yazhou Zhang, Ashley N. Barnes, Naomi F. Campbell, Ruomei Gao
  Journal of the American Chemical Society 01/2012; · 9.91 Impact Factor
• Article: Synthesis and photophysics of an octathioglycosylated zinc(II) phthalocyanine.

  Amit Aggarwal, Sunaina Singh, Yazhou Zhang, Mariah Anthes, Diana Samaroo, Ruomei Gao, Charles Michael Drain
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  ABSTRACT: A water soluble zinc(II) phthalocyanine symmetrically appended with eight thioglucose units was synthesized from commercially available hexadecafluorophthalocyaninatozinc(II) by controlled nucleophilic substitution of the peripheral fluoro groups. The photophysical properties and cancer cell uptake studies of this nonhydrolyzable thioglycosylated phthalocyanine are reported. The new compound has amphiphilic character, is chemically stable, and can potentially be used as a photosensitizer in photodynamic therapy.
  Tetrahedron Letters 10/2011; 52(42):5456-5459. · 2.68 Impact Factor
• Article: Quantification of Thiopurine/UVA-Induced Singlet Oxygen Production.

  Yazhou Zhang, Ashley N Barnes, Xianchun Zhu, Naomi F Campbell, Ruomei Gao
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  ABSTRACT: Thiopurines were examined for their ability to produce singlet oxygen ((1)O(2)) with UVA light. The target compounds were three thiopurine prodrugs, azathioprine (Aza), 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG), and their S-methylated derivatives of 6-methylmercaptopurine (me6-MP) and 6-methylthioguanine (me6-TG). Our results showed that these thiopurines were efficient (1)O(2) sensitizers under UVA irradiation but rapidly lost their photoactivities for (1)O(2) production over time by a self-sensitized photooxidation of sulfur atoms in the presence of oxygen and UVA light. The initial quantum yields of (1)O(2) production were determined to be in the range of 0.30-0.6 in aqueous solutions. Substitution of a hydrogen atom with a nitroimidazole or methyl group at S decreased the efficacy of photosensitized (1)O(2) production as found for Aza, me6-MP and me6-TG. (1)O(2)-induced formation of 8-oxo-7,8-dihydro-2'-dexyguanosine (8-oxodGuo) was assessed by incubation of 6-methylthiopurine/UVA-treated calf thymus DNA with human repair enzyme 8-oxodGuo DNA glycosylase (hOGG1), followed by apurinic (AP) site determination. Because more 8-oxodGuo was formed in Tris D(2)O than in Tris H(2)O, (1)O(2) is implicated as a key species in the reaction. These findings provided quantitative information on the photosensitization efficacy of thiopurines and to some extent revealed the correlations between photoactivity and phototoxicity.
  Journal of Photochemistry and Photobiology A Chemistry 10/2011; 224(1):16-24. · 2.42 Impact Factor