Nanotechnology has been proven to be increasingly compatible with pharmacological and biomedical applications. Therefore, we evaluated the biological interactions of single-wall carbon nanotubes functionalized with polyethylene glycol (SWNT-PEG). For this purpose, we analyzed biochemical, histological, behavioral and biodistribution parameters to understand how this material behaves in vitro and in vivo using the fish Danio rerio (zebrafish) as a biological model. The in vitro results for fish brain homogenates indicated that SWNT-PEG had an effect on lipid peroxidation and GSH (reduced glutathione) content. However, after intraperitoneal exposure, SWNT-PEG proved to be less biocompatible and formed aggregates, suggesting that the PEG used for the nanoparticle functionalization was of an inappropriate size for maintaining product stability in a biological environment. This problem with functionalization may have contributed to the low or practically absent biodistribution of SWNT-PEG in zebrafish tissues, as verified by Raman spectroscopy. There was an accumulation of material in the abdominal cavity that led to inflammation and behavioral disturbances, as evaluated by a histological analysis and an open field test, respectively. These results provide evidence of a lack of biocompatibility of SWNTs modified with short chain PEGs, which leads to the accumulation of the material, tissue damage and behavioral alterations in the tested subjects.
Functionalization of single-walled carbon nanotubes (SWCNT) with polyethylene glycol (PEG) is among the most promising strategies to avoid SWCNT aggregation in aqueous media, improving its interactions with biological systems. However, the best molecular PEG weight and functionalization strategy remain under investigation. In this work we assessed the toxicological effects of SWCNT functionalized with PEG at 600 Da in zebrafish embryos. Embryos were exposed to SWCNT at 0.01, 0.1 and 1 mg/L from 3 to 96 h post-fertilization (hpf). At the highest concentration, SWCNT led to toxic effects at several endpoints, including mortality, delayed hatching, malformations, reduced body length, increased ROS production and DNA damage. Even with these effects, SWCNT could not be detected within the bodily tissues of the larvae. Our results give evidence that the tested PEGylation approach was unsuitable to avoid SWCNT aggregation in aqueous media, and that SWCNT can induce toxicity even without being absorbed by the organism by obstructing the chorion pores.
In this way, this review focuses on CNT PEGylation, aiming to help in the development of viable and effective nanomedicines for neuroscience applications.
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