title: Fluorescent Lead(IV) Sulfide Nanoparticles Synthesized by Idiomarina sp. Strain PR58-8 for Bioimaging Applications.
abstract: 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,Idiomarinasp. strain PR58-8. The bacterium tolerated up to 8 mM Pb(NO3)2during growth. Non-protein thiols dose-dependently increased in response to metal exposure, which suggests they are involved in the growth of PbS2crystals 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-PbS2nanoparticles (PbS2NPs) 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 PbS2NPs exhibited a large Stokes' shift (8,362 cm-1) 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 forin situbioimaging applications. The "as-synthesized" lead(IV) sulfide nanoparticles may provide expanded opportunities for targeted bioimaging via modifying the surface of the particles.IMPORTANCEThis article reports the intracellular synthesis of fluorescent lead(IV) sulfide nanoparticles (PbS2NPs) 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 PbS2NPs can be achieved using routine epifluorescence microscopes, as it fluoresces in the visible range. The research on PbS2nanoparticles 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 PbS2nanoparticles byIdiomarinasp. 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 PbS2nanoparticles.
authors.affiliation: Department of Biological Sciences, Birla Institute of Technology and Sciences, Pilani, K K Birla Goa Campus, Zuarinagar, Goa, India.
authors.forename: Pallavee
authors.identifier: http://orcid.org/0000-0002-6974-0715
authors.initials: P
authors.lastname: Srivastava
authors.affiliation: Department of Biological Sciences, Birla Institute of Technology and Sciences, Pilani, K K Birla Goa Campus, Zuarinagar, Goa, India meenal@goa.bits-pilani.ac.in.
authors.forename: Meenal
authors.initials: M
authors.lastname: Kowshik
mesh_terms: D034241:Alteromonadaceae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry / Q000648:ultrastructure; D005453:Fluorescence; D006367:HeLa Cells; D006801:Humans; D007854:Lead / Q000737:chemistry* / Q000494:pharmacology; D008279:Magnetic Resonance Imaging; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D009566:Nitrates / Q000494:pharmacology; D013440:Sulfides / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D009566:Nitrates; D013440:Sulfides; C018391:lead sulfide; D007854:Lead; C017461:lead nitrate
keywords: Idiomarina; bioimaging; fluorescent; halophiles; lead(IV) sulfide; nanoparticles