Surface-Modified Zinc Oxide Nanoparticles And Their Bioactivity Towards Hela Cell Lines, Escherichia Coli And Shigella Flexneri
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Date
2016-08
Authors
Sirelkhatim, Amna Hassan
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Abstract
The main objective of this thesis is to investigate the structural, morphological, optical and physiochemical properties of zinc oxide nanoaprticles (ZnO-NPs) with their correlation on anti-cancer activity towards human cervical cancer cell lines (HeLa). The antibacterial activity of ZnO-NPs towards E.coli and Shigella Flexneri was studied as well to get considerable indication of the bioactivity of ZnO-NPs. Three ZnO-NPs samples were used, initially a systematical comprehensive characterization for their structural, morphological (FESEM, TEM, ESI, EDS, XRD), optical (UV-Vis absorption and FTIR), and electrical (I-V measurements, zeta potential) properties have been carried out. Surface modification was performed via coating with Pluronic F-127 copolymer obtained stabilized sample, namely ZnO-I. And UVA illumination, the sample recalled, ZnO-UVA, while the third sample, was bare denoted ZnO-II. TEM and FESEM showed major nano/micro- rods structures in ZnO-UVA and ZnO-I and nano/micro plated structures of different dimensions. ZnO-II showed mainly nano/micro plates and some nanorods, few tetrapod and other structures. TEM showed particle sizes around 80 nm, and XRD analysis revealed the crystallinity of the samples whereas ESI displayed the elemental maps of Zn and O atoms of ZnO structures showing the ratios of O: Zn. Higher Zn ratio resulted in higher desorption of oxygen on ZnO-UVA and ZnO-I surfaces, revealed by the increased photoconductivities of 7.51 nS and 5.19 nS, respectively, while ZnO-II showed 1.49 nS. UVA irradiation increased conductivity by desorption of weakly attached surface oxygen species, which enhanced higher ROS creation. By surface coating, a uniform and non-agglomerated ZnO-I suspension treated HeLa cells caused 25 mM IC50, while for ZnO-II and ZnO- UVA were 0.2 mM and 0.35 mM respectively. This was
referred to polymer surface coating which showed differences in FTIR and surface charge. Zeta potential measurements showed 36.3 mV (ZnO-I), 31.3 mV (ZnO-UVA), and 24.3 mV (ZnO-II). While FTIR spectra showed functional groups in ZnO-I surface of C-H stretch at 2873 cm−1 which were absent in ZnO-II, and strong –OH stretching at 2971 cm−1 for carboxylic acids and weaker in ZnO-II. Differences in surface chemistry led to differences in their cytotoxicity, that ZnO-I showed higher ROS yield and apoptosis of 60.9 %, while ZnO-II apoptosis was 44.6 %. Highest ROS generation was possessed by ZnO-UVA with apoptosis of 70.1 %, and all samples arrested cell cycle progression in different phases. Toxicity was further evidenced by DNA fragmentation strands by agarose gel electrophoresis, indicating induction of apoptosis. Moreover, fluorescence and light microscopes images showed apoptotic cell death and cellular morphological changes.
On the other hand, ZnO-II and UVA caused growth inhibition of 51±0.9%, and 76±2% on E.coli, and 81±1% and 95±2%, for Shigella Flexneri respectively, showing excellent effect on Shigella by ZnO-UVA. This was ascribed to smaller size of nanorods in ZnO-UVA compared to plates in ZnO-II, suggested to release zinc ions (Zn2+), and enhanced higher ROS level by UVA. These results were obviously seen in the damaged membrane and cell disruption by FESEM images. Finally, this study emerged with an application denoted as Developed-Coated-UVA-ZnO Formula (CUZF) resembling photodynamic therapy (PDT). It possessed highest ROS yield with cell viability as low as 8% only after 24h. It was suggested as a promising potential approach in cancer therapy by ZnO-NPs against the high global morbidity and mortality of cervical cancer.
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Keywords
The antibacterial activity of ZnO-NPs towards , E.coli and Shigella Flexneri.