Abstract
Abstract Various technological and biomedical applications rely on the ability of materials to emit light (photoluminescence [PL]), and, among them, metal nanoparticles (NPs) and semi-conductor Quantum Dots (QDs) represent ideal candidates as sensing probes and imaging tools, portraying better PL features than conventional organic dyes. However, the knowledge of PL behavior of semiconductor NPs – i.e., selenium; SeNPs – is still in its infancy, especially for those synthesized by microorganisms. Considering the essential role played by biogenic SeNPs as antimicrobial, anticancer, and antioxidant agents, or food supplements, their PL properties must be explored to take full advantage of them as eco-friendly and versatile tools. Here, PL features of SeNPs produced by the Se-tolerant Stenotrophomonas maltophilia SeITE02 strain, compared with chemogenic ones, are investigated, highlighting the PL dependency on the NP size. Indeed, PL emission shifted from indigo-blue (emission wavelength λ em 400–450 nm) to green-yellow (λ em 480–570 nm) and orange-red (λ em 580–700 nm) for small (ca. 50 nm) and big (ca. 100 nm) SeNPs respectively, revealing the versatility of an environmental bacterial isolate to synthesize diverse PL probes. Besides, biogenic SeNPs show PL lifetime comparable to those of the most used fluorophores, supporting their potential application as markers for (bio)imaging.
Highlights
Microbial nanotechnology is an expanding research field based on the capability of microorganisms to sequester and/or transform non- or micro-essential yet toxic metal ions into their less bioavailable elemental forms, which assemble in either intra- or extra-cellular nanostructures (NSs) [1,2]
PL features of SeNPs produced by the Se-tolerant Stenotrophomonas maltophilia SeITE02 strain, compared with chemogenic ones, are investigated, highlighting the PL dependency on the NP size
SeITE02 cells grown in the presence of sodium selenite (Na2SeO3) – as Se precursor – and different complex media (Luria Bertani [LB] and nutrient broth [Nutrient Broth (NB)]) synthesized spherical SeNPs (Figures 1A, 2A), resembling in morphology those of chemical synthesis (Figures 1B, 2B), which were obtained through the reduction reaction occurring between L-cysteine and Na2SeO3 [48]
Summary
Microbial nanotechnology is an expanding research field based on the capability of microorganisms to sequester and/or transform non- or micro-essential yet toxic metal (loid) ions into their less bioavailable elemental forms, which assemble in either intra- or extra-cellular nanostructures (NSs) [1,2]. Bacteria have been used to remediate environmental matrices contaminated with Se compounds, attenuating their critical concentration and, simultaneously, producing selenium NSs (SeNSs), which can be recovered [3,4,5,6,7] This aspect represents a technological advantage since Se is a scarce and rare element of our Earth’s crust featuring properties (e.g., high photoconductivity, piezoelectricity, thermoelectricity, spectral sensitivity) [8,9] that makes it of utmost importance at an economic level. Piacenza et al.: Tunable photoluminescence properties of SeNPs and innovative nanosensors and imaging markers, avoiding the need for additional fluorescent tags (proteins or dyes), which often leads to observational artifacts [15] On this matter, metal or metal-based NSs have been studied in depth for their optical and PL features, yet this knowledge in the case of SeNSs is still lagging [6, 16,17]. In an attempt to support the application of these biogenic SeNPs as a relevant and valuable PL tool, PL lifetime measurements and Super Resolution-Confocal Laser Scanning Microscopy (SR-CLSM) were performed and duly discussed
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