Green synthesis of silver nanoparticles using transgenic <i>Nicotiana tabacum</i> callus culture expressing silicatein gene from marine sponge <i>Latrunculia oparinae</i>

In the present investigation, transgenic tobacco callus cultures and plants overexpressing the silicatein gene <i>LoSilA1</i> from marine sponge <i>Latrunculia oparinae</i> were obtained and their bioreduction behaviour for the synthesis of silver nanoparticles (AgNPs) was studied. Synthesized nanoparticles were characterized using UV–visible spectroscopy, Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic flame electron microscopy (AFM) and nanoparticle tracking analysis (NTA). Our measurements showed that the reduction of silver nitrate produced spherical AgNPs with diameters in the range of 12–80 nm. The results of XRD analysis proved the crystal nature of the obtained AgNPs. FTIR analysis indicated that particles are reduced and stabilized in solution by the capping agent, which is likely to be proteins present in the callus extract. Interestingly, the reduction potential of <i>LoSiLA1</i>-transgenic callus line was increased three-fold compared with the empty vector-transformed calli. The synthesized AgNPs were found to exhibit strong antibacterial activity against <i>Escherichia coli</i> and <i>Agrobacterium rhizogenes</i>. The present study reports the first evidence for using genetic engineering for activation of the reduction potential of plant cells for synthesis of biocidal AgNPs.本研究中，我们获得了过表达海洋海绵<i>Latrunculia oparinae</i>来源的硅蛋白基因<i>LoSilA1</i>的转基因烟草愈伤组织培养物与转基因植株，并探究了其在银纳米颗粒（silver nanoparticles, AgNPs）合成中的生物还原行为。所合成的纳米颗粒采用紫外-可见分光光度法、傅里叶变换红外光谱（Fourier transformed infrared spectroscopy, FTIR）、X射线衍射（X-ray diffraction, XRD）、扫描电子显微镜（scanning electron microscopy, SEM）、能量色散X射线光谱（energy-dispersive X-ray spectroscopy, EDX）、原子力显微镜（atomic force microscopy, AFM）以及纳米颗粒追踪分析（nanoparticle tracking analysis, NTA）进行表征。检测结果表明，硝酸银还原所得的AgNPs呈球形，粒径范围为12~80 nm。XRD分析结果证实了所获AgNPs的晶体特性。FTIR分析显示，溶液中的颗粒通过包覆剂实现还原与稳定，该包覆剂大概率为愈伤组织提取物中的蛋白质。值得注意的是，与空载载体转化的愈伤组织相比，<i>LoSilA1</i>转基因愈伤组织株系的还原潜能提升了三倍。研究发现，所合成的AgNPs对大肠杆菌（Escherichia coli）和发根农杆菌（Agrobacterium rhizogenes）均具有较强的抗菌活性。本研究首次报道了利用基因工程技术激活植物细胞还原潜能以合成杀菌型AgNPs的相关证据。