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Featured researches published by Ruomei Gao.


Bioconjugate Chemistry | 2010

Synthesis and photophysical properties of thioglycosylated chlorins, isobacteriochlorins, and bacteriochlorins for bioimaging and diagnostics.

Sunaina Singh; Amit Aggarwal; Sebastian Thompson; João P. C. Tomé; Xianchun Zhu; Diana Samaroo; Mikki Vinodu; Ruomei Gao; Charles Michael Drain

The facile synthesis and photophysical properties of three nonhydrolyzable thioglycosylated porphyrinoids are reported. Starting from meso-perfluorophenylporphyrin, the nonhydrolyzable thioglycosylated porphyrin (PGlc₄), chlorin (CGlc₄), isobacteriochlorin (IGlc₄), and bacteriochlorin (BGlc₄) can be made in 2-3 steps. The ability to append a wide range of targeting agents onto the perfluorophenyl moieties, the chemical stability, and the ability to fine-tune the photophysical properties of the chromophores make this a suitable platform for development of biochemical tags, diagnostics, or as photodynamic therapeutic agents. Compared to the porphyrin in phosphate buffered saline, CGlc₄ has a markedly greater absorbance of red light near 650 nm and a 6-fold increase in fluorescence quantum yield, whereas IGlc₄ has broad Q-bands and a 12-fold increase in fluorescence quantum yield. BGlc₄ has a similar fluorescence quantum yield to PGlc₄ (<10%), but the lowest-energy absorption/emission peaks of BGlc₄ are considerably red-shifted to near 730 nm with a nearly 50-fold greater absorbance, which may allow this conjugate to be an effective PDT agent. The uptake of CGlc₄, IGlc₄, and BGlc₄ derivatives into cells such as human breast cancer cells MDA-MB-231 and K:Molv NIH 3T3 mouse fibroblast cells can be observed at nanomolar concentrations. Photobleaching under these conditions is minimal.


Journal of Physical Chemistry B | 2011

Direct observation and quantitative characterization of singlet oxygen in aqueous solution upon UVA excitation of 6-thioguanines.

Yazhou Zhang; Xianchun Zhu; Joshua Smith; Makeisha T. Haygood; Ruomei Gao

The incorporation of 6-thioguanine (6-TG) into DNA increases the risk of (1)O(2)-initiated skin cancer. We herein provide the first report on quantitative characterization of the photoactivity of 6-thioguanines including 6-TG and 6-thioguanosine. Time-resolved singlet oxygen luminescence was observed directly for the first time after UVA irradiation of 6-thioguanines in both CHCN(3) and aqueous solutions. Their photosensitization was characterized by the quantum yield of singlet oxygen production, showing a dramatic decrease over time from the initial 0.49-0.58 to zero. Experiments performed on both 6-TG and 6-thioguanosine did not show any significant difference in the quantum yield of singlet oxygen production, indicating that there was no potential participation of 7H- and 9H-tautomers. Our findings provide a primary basis for a better understanding of molecular events of thiopurine drugs in biological systems.


Journal of Materials Chemistry | 2012

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 Chandra Ray; Ruomei Gao

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 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 a pH range of 3-6 to 0.08 at pH 8-9, which is consistent with pH-dependent adsorption behavior of TMPyP on 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.


ACS Applied Materials & Interfaces | 2009

pH-responsive, TiO2-attached porphyrin for singlet oxygen production in an aqueous solution.

Wenbing Li; Naveen Gandra; Erick D. Ellis; Shavelle Courtney; Shufang Li; Ebonie Butler; Ruomei Gao

A pH-responsive, TiO2-attached sensitizer was prepared based on the adsorption of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) onto TiO2 nanoparticles. This colloidally dispersed TiO2-attached TCPP behaves as a single-phase colloidal sensitizer at pH 1.0-3.3 with quantum yields of singlet oxygen production (Phi(Delta)) between 0.20 and 0.25, as a heterogeneous particle sensitizer at pH 3.5-6.0 with Phi(Delta) between 0.25 and 0.50, and as homogeneous free TCPP molecules in alkaline solutions with Phi(Delta) = 0.53. The changes in Phi(Delta) are fully consistent with pH-dependent adsorption of TCPP onto the TiO2 surface. Recovery yields of 99.8% for TCPP and 98.8% for TiO2 were obtained from 1.4 mM TiO2-attached TCPP. We attribute its photosensitization ability to retaining TCPP solubility on the TiO2 surface and, hence, activity. This novel system shows a potential to bridge the gap between easily recoverable and highly efficient sensitizers.


ChemPhysChem | 2009

Singlet Oxygen Production upon Two‐Photon Excitation of TiO2 in Chloroform

Wenbing Li; Naveen Gandra; Shavelle Courtney; Ruomei Gao

Singlet oxygen ((1)O(2)) signals observed upon illumination at 532 nm are a consequence of TiO(2) excitation in a two-photon process, and at 355 nm in a one-photon pathway. After corrections for light reflectance, the relative quantum yields of (1)O(2) production are 0.23+/-0.01 and 0.22+/-0.02 for 532 and 355 nm excitation, respectively. Total quenching rate constants of (1)O(2) removal by TiO(2) particles are near the diffusion-controlled rate limit. By employing (1)O(2) as a probe, we have established an efficient and simple method to elucidate the nature of TiO(2) photoexcitation.


Journal of Physical Chemistry B | 2008

Singlet Oxygen Chemistry in Water: A Porous Vycor GlassSupported Photosensitizer

David Aebisher; Nikolay S. Azar; Matibur Zamadar; Naveen Gandra; Harry D. Gafney; Ruomei Gao; Alexander Greer

Singlet molecular oxygen [1O2 (1Deltag)] is generated cleanly in aqueous solution upon irradiation of a heterogeneous complex, meso-tetra(N-methyl-4-pyridyl)porphine (1) adsorbed onto porous Vycor glass (PVG). The cationic photosensitizer 1 tightly binds onto PVG and gives a stable material, which does not dissociate 1 into the surrounding aqueous phase. The production of 1O2 was measured by monitoring the time-resolved 1O2 (1Deltag) phosphorescence at 1270 nm. Indirect analysis of 1O2 generation was also carried out with the photooxidation of trans-2-methyl-2-pentenoate anion, which afforded the corresponding hydroperoxide. Sensitizer-1-impregnated PVG gives rise to a new singlet oxygen generator but more importantly provides a heterogeneous system for use in water.


Tetrahedron Letters | 2014

Synthesis and cell phototoxicity of a triply bridged fused diporphyrin appended with six thioglucose units

Sunaina Singh; Amit Aggarwal; N. V. S. Dinesh K. Bhupathiraju; Brandon Newton; Ahmad Nafees; Ruomei Gao; Charles Michael Drain

A triply bridged fused diporphyrin appended with six thioglucose units is reported. This new, chemically and photochemically stable amphiphilic compound is taken up by breast cancer cells and causes cell death upon light exposure. Photophysical studies reveal absorption bands in the near IR region, and photosensitized formation of singlet oxygen in high quantum yields.


Photochemistry and Photobiology | 2014

Effects of Light Energy and Reducing Agents on C60-Mediated Photosensitizing Reactions†

Michael Quinones; Yazhou Zhang; Penelope Riascos; Huey-Min Hwang; Winfred G. Aker; Xiaojia He; Ruomei Gao

Many biomolecules contain photoactive reducing agents, such as reduced nicotinamide adenine dinucleotide (NADH) and 6‐thioguanine (6‐TG) incorporated into DNA through drug metabolism. These reducing agents may produce reactive oxygen species under UVA irradiation or act as electron donors in various media. The interactions of C60 fullerenes with biological reductants and light energy, especially via the Type‐I electron‐transfer mechanism, are not fully understood although these factors are often involved in toxicity assessments. The two reductants employed in this work were NADH for aqueous solutions and 6‐TG for organic solvents. Using steady‐state photolysis and electrochemical techniques, we showed that under visible light irradiation, the presence of reducing agents enhanced C60‐mediated Type‐I reactions that generate superoxide anion (O2.−) at the expense of singlet oxygen (1O2) production. The quantum yield of O2.− production upon visible light irradiation of C60 is estimated below 0.2 in dipolar aprotic media, indicating that the majority of triplet C60 deactivate via Type‐II pathway. Upon UVA irradiation, however, both C60 and NADH undergo photochemical reactions to produce O2.−, which could lead to a possible synergistic toxicity effects. C60 photosensitization via Type‐I pathway is not observed in the absence of reducing agents.


Journal of the American Chemical Society | 2002

Bis-cyclometalated Ir(III) Complexes as Efficient Singlet Oxygen Sensitizers

Ruomei Gao; David G. Ho; Billy Hernandez; Matthias Selke; Drew Murphy; Peter I. Djurovich; Mark E. Thompson


Tetrahedron | 2006

Possible singlet oxygen generation from the photolysis of indigo dyes in methanol, DMSO, water, and ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate

Naveen Gandra; Aaron T. Frank; Onica Le Gendre; Nahed Sawwan; David Aebisher; Joel F. Liebman; K. N. Houk; Alexander Greer; Ruomei Gao

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Matthias Selke

California State University

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Yazhou Zhang

Jackson State University

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David G. Ho

University of California

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Naveen Gandra

Jackson State University

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Xianchun Zhu

Jackson State University

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Wenbing Li

Jackson State University

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Alexander Greer

City University of New York

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Brandon Newton

Jackson State University

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