Abstract
The ability of commercial monolayer graphene oxide (GO) and graphene oxide nanocolloids (GOC) to interact with different unicellular systems and biomolecules was studied by analyzing the response of human alveolar carcinoma epithelial cells, the yeast Saccharomyces cerevisiae and the bacteria Vibrio fischeri to the presence of different nanoparticle concentrations, and by studying the binding affinity of different microbial enzymes, like the α-l-rhamnosidase enzyme RhaB1 from the bacteria Lactobacillus plantarum and the AbG β-d-glucosidase from Agrobacterium sp. (strain ATCC 21400). An analysis of cytotoxicity on human epithelial cell line A549, S. cerevisiae (colony forming units, ROS induction, genotoxicity) and V. fischeri (luminescence inhibition) cells determined the potential of both nanoparticle types to damage the selected unicellular systems. Also, the protein binding affinity of the graphene derivatives at different oxidation levels was analyzed. The reported results highlight the variability that can exist in terms of toxicological potential and binding affinity depending on the target organism or protein and the selected nanomaterial.
Highlights
The interest in the immobilization of microorganisms and microbial enzymes for biotechnological applications has been continuously rising during the last decades because of several factors, including the increased availability of microbial strains and biocatalysts tailored to new applications, the development of new immobilization supports with improved properties, and the need of a shift toward the use of more sustainable processes in different industrial fields [1,2,3,4,5]
Microscopy analyses using AFM and TEM instruments showed that graphene oxide (GO) and graphene oxide nanocolloids (GOC) flakes were mostly in monolayer state and had a different size, while the analysis of their composition revealed a high similarity between both nanomaterials
The results described in these latter works are in concordance with our observations, since, in spite of the fact that both GO and GOC produced oxidative stress in A549 cells, no significant increase in apoptosis was detected at concentrations up to 160 mg L−1
Summary
The interest in the immobilization of microorganisms and microbial enzymes for biotechnological applications has been continuously rising during the last decades because of several factors, including the increased availability of microbial strains and biocatalysts tailored to new applications, the development of new immobilization supports with improved properties, and the need of a shift toward the use of more sustainable processes in different industrial fields [1,2,3,4,5]. Immobilized biocatalysts facilitate the efficient recovery and separation of the reaction product, the reutilization of the biocatalyst, and enhance the safety of the material handling (i.e., preventing the appearance of allergies). The use of solid supports of microbial cells for the production of high-value compounds (chemicals, enzymes, etc.) and transformation processes in multiple fields (e.g., agricultural, environmental, food, medical, etc.) has been explored as well to enhance the microbial biological activity, to facilitate their delivery and to separate them more from the fermentation broth [3,5,6,7,8]. During the last years there has been an emerging interest in biocompatibility studies for interfacing biological systems with artificial materials. Unicellular microorganisms, such as bacteria, fungi, and algae, have been utilized extensively for the encapsulation of whole single cells as well as for the introduction of nanomaterials onto the living cells
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