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Antibacterial activity and cytotoxicity in vitro of green-synthesized silver nanoparticles using Brassica rapa var. japonica leaf
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| Title: | Antibacterial activity and cytotoxicity in vitro of green-synthesized silver nanoparticles using Brassica rapa var. japonica leaf |
| Other Titles: | ミズナの葉を用いてグリーン合成された銀ナノ粒子の抗菌活性および試験管内細胞毒性 |
| Authors: | Akter, Mahmuda Browse this author |
| Issue Date: | 25-Mar-2019 |
| Publisher: | Hokkaido University |
| Abstract: | In recent era versatile applications of silver nanoparticles (Ag-NPs) have been elevated by various requirements from the consumers and researchers. According to these requirements, tremendous amounts of Ag-NPs have been synthesized using conventional method. Unfortunately, conventional method for synthesis of Ag-NP has been pointed out a matter of concern in respect of environmental toxicity and human health. Already cytotoxic effects of Ag-NPs have been reported in several cell lines. Therefore, the green synthesis of Ag-NPs is considered to be a safer synthesis method, even though it is an alternative to the conventional synthesis method. On the other hand, Ag-NPs are reported to have potential antitumor and anticancer properties in both in vitro and in vivo experiments. From above viewpoints, the present study aimed to be green synthesis of Ag-NPs and evaluation their biomedical applications with underlying mechanisms. To achieve the purpose actual objectives were set. First, Ag-NPs were successfully synthesized from the reduction of Ag+ using AgNO3 solution as a precursor and Brassica rapa var. nipposinica/japonica leaf extract as a reducing and capping agents. In the synthesis procedure no additional chemical reductant and stabilizing agents were used. The characterization of Ag-NPs was carried out using UV-vis spectrometry, energy dispersive X-ray (EDX) spectrometry, fourier transform infrared (FT-IR) spectrometry, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic absorption spectrometry (AAS), and transmission electron microscopy (TEM). The analyses data revealed the successful synthesis of nano-crystalline Ag possessing more stability than commercial Ag-NPs. To confirm synthesis of Ag-NPs exhibiting less toxicity with high antibacterial activity, following experiments have been done. The cytotoxicity of Brassica Ag-NPs was compared with commercial Ag-NPs using PC12 cell system. Three ppm of commercial Ag-NPs reduced cell viability to 23% (control 97%) and increased lactate dehydrogenase activity, whereas, Brassica Ag-NPs did not show any cytotoxicity on both parameters up to a concentration level of 10 ppm in PC12 cells. Moreover, Brassica Ag-NPs exhibited inhibition zone of against growth of Escherichia coli (11.1 ± 0.5 mm) and Enterobacter sp. (15 ± 0.5 mm) which was higher than other green-synthesized Ag-NPs reported previously. The less cytotoxicity and high antibacterial activity of green synthesized Ag-NPs will be great benefits for the safe use of Ag-NPs in consumer products. On the basis of results in this study it could be concluded that cytotoxicity of Ag-NPs is depended on the stability of the particles and the stability depends on the encapsulation or coating of the surface of the particles. Therefore, it was considered that reaction temperature during synthesis could play a vital role in coating of the particles. From the results, it was tried to synthesize optimal Ag-NPs using Brassica rapa var. nipposinika/japonica leaf extract with various temperatures. The synthesis of Ag-NPs was done at four different temperatures such as 25°C (room temperature), 60°C, 80°C and 100°C in order to evaluate the extent of encapsulation of Ag-NPs. The synthesized Ag-NPs were again characterized using UV-vis. spectrophotometer, EDX spectrometer, XRD spectrometer, TEM, and dynamic light scattering techniques. The adopted characterization techniques clearly demonstrate that at 100°C almost all particles were found to be encapsulated which was the primary objective of the present study. Furthermore, in this study, the behavior of various concentrations of green synthesized Ag-NPs in cancer cells was clarified. Brassica Ag-NPs exposed to Caco-2 cells showed significant decrease of the cell viability, increase of the LDH activity in the medium, and decrease of intracellular GSH amounts. Subsequent western blotting analyses revealed that Brassica Ag-NPs induced Beclin 1 mediated autophagic cell death in Caco-2 cells where LC3-II plays a key role. This autophagic process was further accelerated via upregulation of p53. Hence, downregulation of Akt suppressed mTOR activation. Moreover, upregulation of IkB and downregulation of NFkB inhibit DNA transcription which might also promote autophagy and subsequent cell death. Involvement of apoptosis or necrosis behind cell death mechanism in Caco-2 cells was not detected from any of the results in current study. Thus, these results indicated the possibility of anticancer ability of Brassica Ag-NPs to Colorectal cancer cells, Caco-2. In conclusion, this study clearly reveals the potentiality of Brassica leaf extract for the environment friendly green synthesis of Ag-NPs which can be encapsulated with optimal temperature. In addition, Brassica Ag-NPs are less toxic in comparison of commercial Ag-NPs with high antibacterial activity, and also have a possibility of anticancer ability. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第13541号 |
| Degree Level: | 博士 |
| Degree Discipline: | 環境科学 |
| Examination Committee Members: | (主査) 准教授 藏﨑 正明, 教授 沖野 龍文, 教授 野呂 真一郎, 教授 齋藤 健（大学院保健科学研究院）, 教授 倉光 英樹（富山大学大学院理工学研究部） |
| Degree Affiliation: | 環境科学院（環境起学専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/84538 |
| Appears in Collections: | 課程博士 (Doctorate by way of Advanced Course) > 環境科学院(Graduate School of Environmental Science)
学位論文 (Theses) > 博士 （環境科学）
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