Srivastava Pallavee, Kowshik Meenal
Department of Biological Sciences, Birla Institute of Technology and Sciences, Pilani, K K Birla Goa Campus, Zuarinagar, Goa, India.
Department of Biological Sciences, Birla Institute of Technology and Sciences, Pilani, K K Birla Goa Campus, Zuarinagar, Goa, India
Appl Environ Microbiol. 2017 Mar 17;83(7). doi: 10.1128/AEM.03091-16. Print 2017 Apr 1.
The fabrication of nanoparticles by microorganisms presents a "green" method for generating biocompatible nanomaterials. We discovered the intracellular biosynthesis of fluorescent lead(IV) sulfide nanoparticles by the moderate halophile, sp. strain PR58-8. The bacterium tolerated up to 8 mM Pb(NO) during growth. Non-protein thiols dose-dependently increased in response to metal exposure, which suggests they are involved in the growth of PbS crystals and lead detoxification. Using X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, and energy dispersive analysis of X-rays, the nanoparticles were characterized as spherical β-PbS nanoparticles (PbSNPs) with a tetragonal crystal lattice, a crystallite domain size of 2.38 nm, and an interplanar distance of 0.318 nm. A narrow symmetric emission spectrum with a Gaussian distribution and an emission maximum at 386 nm was obtained when the particles were excited at 570 nm. The PbSNPs exhibited a large Stokes' shift (8,362 cm) and a relatively high quantum yield (67%). These properties, along with fluorescence that was maintained in various microenvironments and their biocompatibility, make these nanoparticles excellent candidates for bioimaging. The particles were internalized by HeLa cells and evenly distributed within the cytoplasm, exhibiting their potential for bioimaging applications. The "as-synthesized" lead(IV) sulfide nanoparticles may provide expanded opportunities for targeted bioimaging via modifying the surface of the particles. This article reports the intracellular synthesis of fluorescent lead(IV) sulfide nanoparticles (PbSNPs) by a microorganism. All previous reports on the microbial synthesis of lead-based nanoparticles are on lead(II) sulfide that exhibits near-infrared fluorescence, requiring expensive instrumentation for bioimaging. Bioimaging using PbSNPs can be achieved using routine epifluorescence microscopes, as it fluoresces in the visible range. The research on PbS nanoparticles to date is on their chemical synthesis employing toxic precursors, extreme pH, pressure, and temperature, resulting in cytotoxic products. In this context, the synthesis of PbS nanoparticles by sp. strain PR58-8, described in this work, occurs at ambient temperature and pressure and results in the generation of biocompatible nanoparticles with no hazardous by-products. The excellent fluorescence properties that these particles exhibit, as well as their abilities to easily penetrate the cells and evenly distribute within the cytoplasm, make them exceptional candidates for bioimaging applications. This study demonstrated the synthesis and fluorescence bioimaging application of microbially synthesized PbS nanoparticles.
利用微生物制备纳米颗粒为生成生物相容性纳米材料提供了一种“绿色”方法。我们发现中度嗜盐菌sp. 菌株PR58 - 8可在细胞内生物合成荧光硫化铅（IV）纳米颗粒。该细菌在生长过程中能耐受高达8 mM的Pb(NO₃)₂。非蛋白质硫醇的含量随金属暴露量呈剂量依赖性增加，这表明它们参与了硫化铅晶体的生长和铅解毒过程。通过X射线衍射、透射电子显微镜（TEM）、高分辨率TEM以及X射线能量色散分析，这些纳米颗粒被表征为具有四方晶格、微晶域尺寸为2.38 nm、晶面间距为0.318 nm的球形β - PbS纳米颗粒（PbSNPs）。当在570 nm激发这些颗粒时，可获得具有高斯分布且发射最大值在386 nm的窄对称发射光谱。PbSNPs表现出较大的斯托克斯位移（8362 cm⁻¹）和相对较高的量子产率（67%）。这些特性，连同在各种微环境中都能保持的荧光以及它们的生物相容性，使这些纳米颗粒成为生物成像的极佳候选者。这些颗粒被HeLa细胞内化并均匀分布在细胞质中，展现出它们在生物成像应用中的潜力。“合成态”的硫化铅（IV）纳米颗粒通过修饰颗粒表面可能为靶向生物成像提供更多机会。本文报道了一种微生物在细胞内合成荧光硫化铅（IV）纳米颗粒（PbSNPs）的方法。此前所有关于微生物合成铅基纳米颗粒的报道都是关于具有近红外荧光的硫化铅（II），其生物成像需要昂贵的仪器设备。使用PbSNPs进行生物成像可通过常规落射荧光显微镜实现，因为它在可见光范围内发光。迄今为止，对PbS纳米颗粒的研究是关于使用有毒前驱体、极端pH值、压力和温度进行化学合成，会产生细胞毒性产物。在此背景下，本研究中描述的sp. 菌株PR58 - 8合成PbS纳米颗粒是在常温常压下进行的，并且产生了无有害副产物的生物相容性纳米颗粒。这些颗粒所表现出的优异荧光特性，以及它们易于穿透细胞并均匀分布在细胞质中的能力，使它们成为生物成像应用的杰出候选者。本研究展示了微生物合成的PbS纳米颗粒的合成及其荧光生物成像应用。
