Mycosynthesis of Zinc Oxide Nanoparticles Exhibits Fungal Species Dependent Morphological Preference

Abstract

Filamentous fungi can synthesize a variety of nanoparticles (NPs), a process referred to as mycosynthesis that requires little energy input, do not require the use of harsh chemicals, occurs at near neutral pH, and do not produce toxic byproducts. While NP synthesis involves reactions between metal ions and exudates produced by the fungi, the chemical and biochemical parameters underlying this process remain poorly understood. Here, the role of fungal species and precursor salt on the mycosynthesis of zinc oxide (ZnO) NPs is investigated. This data demonstrates that all five fungal species tested are able to produce ZnO structures that can be morphologically classified into i) well‐defined NPs, ii) coalesced/dissolving NPs, and iii) micron‐sized square plates. Further, species‐dependent preferences for these morphologies are observed, suggesting potential differences in the profile or concentration of the biochemical constituents in their individual exudates. This data also demonstrates that mycosynthesis of ZnO NPs is independent of the anion species, with nitrate, sulfate, and chloride showing no effect on NP production. These results enhance the understanding of factors controlling the mycosynthesis of ceramic NPs, supporting future studies that can enable control over the physical and chemical properties of NPs formed through this “green” synthesis method.

Identifying biochemical constituents involved in the mycosynthesis of zinc oxide nanoparticles

“…The three fungi that displayed the ability to form well-defined, spheroid ZnO NPs, A. versicolor (7/8 replicates), P. variotii (4/8 replicates), and P. chrysogenum (4/8 replicates), also produced a middle range of protein fragments in this current study with 53, 43, and 20, respectively. 25 These observations suggest that the diversity of the protein profile may possess an optimum range, which in turn influences the nucleation and growth of ZnO NPs. The proteomes of A. niger and A. versicolor show the greatest overlap (Table S6 †), despite producing difference ZnO NP morphologies.…”

“…The other three fungi produced highly mixed morphologies including well-defined NPs, highly coalesced/ dissolving NPs and/or micron-scale plates. 25 With this in mind, we aimed to identify metabolites that were enriched in the A. versicolor exudate compared to the others, with particular attention to C. cladosporioides, as a means of ascertaining constituents that were important in forming well-defined NPs. Fig.…”

“…First, HMTA was ∼130-fold more concentrated in A. versicolor exudate compared to C. cladosporioides, and only slightly enriched compared to the other three fungi, which had been observed to synthesize well-defined ZnO NPs at least a portion of the time. 25 Second, there are numerous reports of HMTA functioning to bind metal cations and form nanomaterials such as metal organic frameworks in a non-biological context. [40][41][42][43][44][45][46][47][48] As previously described, many reports on the biosynthesis of NPs either challenge the bacteria, fungi, yeast, or leaf extract directly with metal salts, or spike the resulting exudates after the organismal component has been removed.…”

“…The washed mycelia were then resuspended in deionized water, treated with the appropriate metal challenge condition to be tested, and incubated at 28 °C with 150 rpm orbital shaking for 72 h. The pH of the resulting media was neutral, ranging from ∼6.4-7.2, as previously described. 25…”

“…Previously, we reported a morphological dependency exhibited by five fungi when producing ZnO NPs. 25 In this former work, Aspergillus versicolor (Vuillemin) Tiraboschi was identified as the most prominent producer of well-defined ZnO NPs, while Cladosporium cladosporioides (Fresen.) de Vries was identified as the primary producer of a square plate morphology.…”