University of Puerto Rico-Mayagüez Campus Department of Chemistry Departmental Seminar By Sandra Pena Tusday Dicember 3, 2013 10:30 am Q123 Enhanced Singlet Oxygen Generation from ZnO Quantum Dot Nanoparticles Derivatives for Photodynamic Therapy (PDT) and Cytotoxic Activity in Chronic Lymphocytic Leukemia (CLL) Tumor Cells The generation of singlet oxygen (SO) in presence of specific photosensitizers (PS) or semiconductor quantum dots and its application in photodynamic therapy is of great interest to develop cancer therapies with no need of surgery, chemotherapy or radiotherapy. The present work is focused on the identification of the main factors leading to the enhancement of SO production using rose bengal (RB), and methylene blue(MB) as PS species in organic and aqueous medium , subsequent the capacity of ZnO, ZnS and ZnO/ZnS core-shell quantum dots (QDs) and manganese-doped ZnO and ZnS nanoparticles (NPs) to generate SO as potential photosensitizers, was determined. The presence of the Mn+2 dopant ion alters the electronic properties of QDs and enhances production of SO, important in PDT. The % of Mn doping for ZnO was 0.5%, 1.0%, 1.5% and 2.0% and for ZnS NPs was 2.0%. ZnO/ZnS water soluble core-shell QDs were obtained by slow decomposition of aqueous Zn+2- MPA complexes at pH 10.3 over a ZnO QDs water suspension under reflux. Colloidal ZnS nanocrystals with Mn+2 ion as dopant were prepared using poly-vinylpyrrolidine (PVP) as capping agent. Mn-doped ZnO were synthesized by a precipitation method using highly pure zinc acetate dihydrate as a precursor with sodium hydroxide solution. As part of the research work, a comparative study was performed with the variable parameters as concentration, type of quencher, light source, excitation wavelength, reaction time, distance from light source, and nature of solvent. In this research four quenchers were studied: 1,3-diphenylisobenzofuran, 2,5-diphenylfuran, the system n,n-dimethyl-4-nitrosoaniline (RNO) coexisting with imidazole or L-histidine. Concentrations of the photosensitizers (PS), NPs and chemical quenchers were optimized for photooxidation reactions. The kinetics of the quenchers degradation by generated SO species and the corresponding quantum yield (QY), was determined by photo-oxidation of the chemical quencher by monitoring the disappearance of the quencher by fluorescence and spectrophotometry and analysis of a fluorescent probe Singlet Oxygen Sensor Green (SOSG) in the presence of NPs. The results on the QY by spectrophotometric analysis were 0.60, 0.32, 0.17, 0.36 and 0.20 for ZnO:Mn+20.5%, ZnO:Mn+21.0%, ZnO:Mn+21.5, ZnS and ZnS:Mn+2 NPs respectively. Also high QY were obtained by fluorometry quantitative analysis of photo-oxidation reactions either using DPBF as quencher or SOSG as a fluorescent probe for singlet oxygen measurement. These results raises the possibility to utilize these NPs as efficient photosensitizers in cancer PDT. In addition, we performed in vitro studies with NPs to treat B-CLL cells, specially when combined with PDT, and also the relative yield of SO generated by NPs was evaluated by fluorescence probes. The best results were obtained with 0.5% Mn-doped ZnO NPs . Resistant to traditional therapies un-mutated B-CLL cells responded strongly to the cytotoxic effect of Mn-doped ZnO NPs after PDT, suggesting that this innovative therapy with modifications could be used in the near future as an alternative effective treatment specially under the occurrence of B-CLL difficult to treat cell phenotypes.
Posted on: Mon, 02 Dec 2013 17:44:29 +0000
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