Biosynthesis of gold nanoparticles by the living freshwater diatom Eolimna minima, a species developed in river biofilms

Abstract

Testing biotransformation capacities of living aquatic microalgae diatoms to naturally synthetize gold nanoparticles (AuNP) from gold salts and assessing aftereffects on their viability by microscope observations is a great challenge. In this work, a laboratory experiment was conducted, which aimed to observe (i) directly by transmission electronic and light microscopy and (ii) through indirect measurements (UV-visible spectroscopy) the periphytic freshwater diatom Eolimna minima exposed to gold salts. This work revealed the capacity of E. minima to intracellularly biosynthetize AuNP and to tolerate it. AuNP synthesis appears as a mechanism of detoxification to protect diatom from gold salt contamination. We also pointed out the risks associated with the spread of diatoms full of AuNP, through the trophic web of freshwater ecosystems. The preponderant part of the diatoms in natural biofilms associated with their position at the basis of the trophic webs in rivers could then make them responsible for the contamination of their consumers (grazer animals) and consequently for the potential release of AuNP through the entire food web.

Metal Nanoparticle–Microbe Interactions: Synthesis and Antimicrobial Effects

“…[ 173 ] Extracellular biosynthesis of AuNPs in diatoms biofilms has been reported as a metal detoxification mechanism. [ 174 ] Similar observations were reported for two other diatom biofilms, Navicula atomus and Diadesmis gallica , where AuNPs were formed in the extracellular polymeric substance. [ 175 ]…”

Effect of Metals, Metalloids and Metallic Nanoparticles on Microalgae Growth and Industrial Product Biosynthesis: A Review

“…Synthesis of nanoparticles by microorganisms (bacteria, yeast, fungi and microalgae) can constitute a green and environmentally friendly method for nanoparticles production [ 168 , 169 ]. Formation of nanoparticles: Au, Ag or Pd ( Table 4 ) from metal ions solutions takes place inside microalgae cells (intracellularly) or in the media (extracellularly) via interactions with molecules of microalgal cell metabolism (NADH, pigments, peptides, proteins and polysaccharides) [ 170 , 171 , 172 , 173 , 174 , 175 , 176 ]. The size of synthetized nanoparticles depends on microalgal strain and metal type used, but place of synthesis, initial metal loading, light and temperature are also crucial factors influencing formation of nanoparticles.…”

Reducing Efficiency of Fucoxanthin in Diatom Mediated Biofabrication of Gold Nanoparticles

“…showed DNA binding affinity and fluorescent property, respectively. The marine diatom Stephanopyxis turris [ 26 ] and freshwater diatom Eolimna minima [ 27 ] were reported as potential strains to synthesize GNPs at the intracellular level. Biosilica obtained from diatoms have already been decorated by different nanoparticles containing silver [ 28 ], germanium [ 29 ], titanium dioxide [ 30 ] and iron oxide [ 31 ] to fabricate hybrid microparticles, which are considered more stable and are also very useful in photothermal therapy and multimodal imaging for cancer detection [ 24 ].…”