Redox‐enzymes, cells and micro‐organisms acting on carbon nanostructures transformation: A mini‐review

Abstract

Carbon nanotubes, graphene and fullerenes are actual nanomaterials with many applications in different industrial areas, with increasing potentialities in the field of nanomedicine. Recently, different proactive approaches on toxicology and safety management have become the focus of intense interest once the industrial production of these materials had a significant growth in the last years, even though their short- and long-term behaviors are not yet fully understood. The most important concerns involving these carbon-based nanomaterials are their stability and potential effects of their life cycles on animals, humans, and environment. In this context, this mini review discuss the biodegradability of these materials, particularly through redox-enzymes, micro-organisms and cells, to contribute toward the design of biocompatible and biodegradable functionalized carbon nanostructures, in order to use these materials safely and with minimum impact on the environment.

Nanotoxicity of Graphene and Graphene Oxide

“…Toxicological studies should consider the purity (quality) of the sample, especially the presence of oxidative debris formed during the early stages of synthesis and/or during the functionalizing process, which largely alters the surface microchemical environment of graphene and GO . In addition, the nonmolecular behavior of graphenes must be considered in nanotoxicological models and protocols because of the intrinsic variation of the graphene characteristics, such as size, morphology, and chemical structure related to the nature of this material, in addition to oxidative methods used o prepared GO …”

Mechanisms of Colloidal Stabilization of Oxidized Nanocarbons in the Presence of Polymers: Obtaining Highly Stable Colloids in Physiological Media

“…As a result, challenges are presented in terms of these aspects impact on the biophysicochemical behavior, biological effects and toxicity of nanocarbons 11, 16,28,29 .…”

“…Although highly promising in nanomedicine applications, the intrinsic characteristics of nanocarbons, such as CNTs and GO, currently present great challenges to nanomedicine, mainly in regard to their purity and the standardization of their surface chemical structure and morphology. As a result, challenges presented in terms of these aspects impact the biophysicochemical behavior, biological effects, and toxicity of nanocarbons. ,,, However, prior to their biological/medical application, manipulation and processing of nanocarbons are still very deficient. Basic methods for providing water dispersibility and increasing the chemical processability of carbon-based nanomaterials involve mainly chemical oxidation with inorganic acids, such as nitric and sulfuric acid, gaseous-based physical functionalizations, surface modification through well-established synthetic routes from organic chemistry, and also a myriad of noncovalent functionalizations. ,,,,,,, …”

Aspectos ambientais relacionados à síntese, utilização e descarte do grafeno

“…No entanto, os autores apontam que modificações nessas nanoestruturas, como ativações químicas ou impurezas, podem propiciar reações bioquímicas indesejáveis. Nesse sentido, Seabra et al (2013) explanaram o uso de ácido sulfúrico e peróxido de hidrogênio (H2SO4/H2O2) para purificação de nanotubos de carbono, viabilizando a remoção de catalisadores residuais, objetivando a degradação do nanomaterial. Assim, os autores relataram que em 8 semanas a nanoestrutura de carbono se reduziu a menos da metade do tamanho original, com degradação total após 16 semanas com esse tratamento.…”

“…No entanto, Ferreira et al (2019) realizaram um estudo cuja conclusão foi oposta à descrita por Zarbin e Oliveira (2013) e estudada por Seabra et al (2013). Ferreira et al (2019) estudaram a toxicidade de OG, com e sem a ativação funcional de grupos amina e óxido de ferro, OG NH2/Fe e OG, respectivamente, frente a sementes de Lactuca sativa L. Os autores alegam estudar a toxicidade do OG NH2/Fe e OG sob a possibilidade de utilizar o OG para tratamento de efluentes têxteis como adsorvente, o que pode gerar o OG NH2/Fe , isto é, OG contaminado.…”