The industrial production of silver nanoparticles (AgNPs) and its commercial applications are being considerably increased in recent times, resulting in the release of AgNPs in the environment and enhanced probability of contaminations and their adverse effects on living systems. Based on this, the present study was conducted to evaluate the in vitro cytotoxicity of actinomycete-synthesized AgNPs on Allium cepa (A. cepa) root tip cells. A green synthesis method was employed for biosynthesis of AgNPs from Streptomyces sp. NS-33. However, morphological, physiological, biochemical, and molecular analysis were carried out to characterize the strain NS-33. Later, the synthesized AgNPs were characterized and antibacterial activity was also carried out against pathogenic bacteria. Finally, cytotoxic activity was evaluated on A. cepa root tip cells. Results showed the synthesis of spherical and polydispersed AgNPs with a characteristic UV-visible (UV-Vis.) spectral peak at 397 nm and average size was 32.40 nm. Energy dispersive spectroscopy (EDS) depicted the presence of silver, whereas Fourier transform infrared (FTIR) studies indicated the presence of various functional groups. The phylogenetic relatedness of Streptomyces sp. NS-33 was found with Streptomyces luteosporeus through gene sequencing. A good antibacterial potential of AgNPs was observed against two pathogenic bacteria. Concerning cytotoxicity, a gradually decreased mitotic index (MI) and increased chromosomal aberrations were observed along with the successive increase of AgNPs concentration. Therefore, the release of AgNPs into the environment must be prevented, so that it cannot harm plants and other beneficial microorganisms.

中文翻译：

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放线菌合成的银纳米粒子对洋葱根尖细胞的细胞毒性的生物合成、表征和体外评估

近年来，银纳米粒子 (AgNPs) 的工业生产及其商业应用大大增加，导致 AgNPs 在环境中的释放，增加了污染的可能性及其对生命系统的不利影响。基于此，本研究旨在评估放线菌合成的 AgNPs 对洋葱 (A. cepa) 根尖细胞的体外细胞毒性。采用绿色合成方法从链霉菌属生物合成 AgNPs。NS-33。然而，进行了形态学、生理学、生化和分子分析来表征菌株 NS-33。后来，对合成的 AgNPs 进行了表征，并对病原菌进行了抗菌活性。最后，评估了洋葱根尖细胞的细胞毒活性。结果表明合成的球形和多分散 AgNPs 在 397 nm 处具有特征性紫外-可见 (UV-Vis.) 光谱峰，平均尺寸为 32.40 nm。能量色散光谱 (EDS) 描述了银的存在，而傅里叶变换红外 (FTIR) 研究表明存在各种官能团。链霉菌属的系统发育相关性。NS-33 通过基因测序与 Streptomyces luteosporeus 一起被发现。观察到 AgNPs 对两种病原菌具有良好的抗菌潜力。关于细胞毒性，随着 AgNPs 浓度的连续增加，观察到有丝分裂指数 (MI) 逐渐降低和染色体畸变增加。因此，必须防止 AgNPs 释放到环境中，使其不会伤害植物和其他有益微生物。