Lidiane Dal Bosco

Biodistribution and toxicological study of PEGylated single-wall carbon nanotubes in the zebrafish (Danio rerio) nervous system

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.

Toxicity of single‐wall carbon nanotubes functionalized with polyethylene glycol in zebrafish (Danio rerio) embryos

Single‐wall carbon nanotubes functionalized with polyethylene glycol (SWCNT‐PEG) are promising materials for biomedical applications such as diagnostic devices and controlled drug‐release systems. However, several questions about their toxicological profile remain unanswered. Thus, the aim of this study was to investigate the action of SWCNT‐PEG in Danio rerio zebrafish embryos at the molecular, physiological and morphological levels. The SWCNT used in this study were synthesized by the high‐pressure carbon monoxide process, purified and then functionalized with distearoyl phosphatidylethanolamine block copolymer‐PEG (molecular weight 2 kDa). The characterization process was carried out with low‐resolution transmission electron microscopy, thermogravimetric analysis and Raman spectroscopy. Individual zebrafish embryos were exposed to the SWCNT‐PEG. Toxic effects occurred only at the highest concentration tested (1 ppm) and included high mortality rates, delayed hatching and decreased total larval length. For all the concentrations tested, the alkaline comet assay revealed no genotoxicity, and Raman spectroscopy measurements on the histological slices revealed no intracellular nanotubes. The results shown here demonstrate that SWCNT‐PEG has low toxicity in zebrafish embryos, but more studies are needed to understand what mechanisms are involved. However, the presence of residual metals is possibly among the primary mechanisms responsible for the toxic effects observed, because the purification process was not able to remove all metal contamination, as demonstrated by the thermogravimetric analysis. More attention must be given to the toxicity of these nanomaterials before they are used in biomedical applications. Copyright

PEGylated Carbon Nanotubes Impair Retrieval of Contextual Fear Memory and Alter Oxidative Stress Parameters in the Rat Hippocampus

Carbon nanotubes (CNT) are promising materials for biomedical applications, especially in the field of neuroscience; therefore, it is essential to evaluate the neurotoxicity of these nanomaterials. The present work assessed the effects of single-walled CNT functionalized with polyethylene glycol (SWCNT-PEG) on the consolidation and retrieval of contextual fear memory in rats and on oxidative stress parameters in the hippocampus. SWCNT-PEG were dispersed in water at concentrations of 0.5, 1.0, and 2.1 mg/mL and infused into the rat hippocampus. The infusion was completed immediately after training and 30 min before testing of a contextual fear conditioning task, resulting in exposure times of 24 h and 30 min, respectively. The results showed that a short exposure to SWCNT-PEG impaired fear memory retrieval and caused lipid peroxidation in the hippocampus. This response was transient and overcome by the mobilization of antioxidant defenses at 24 h. These effects occurred at low and intermediate but not high concentration of SWCNT-PEG, suggesting that the observed biological response may be related to the concentration-dependent increase in particle size in SWCNT-PEG dispersions.

Biopersistence of PEGylated Carbon Nanotubes Promotes a Delayed Antioxidant Response after Infusion into the Rat Hippocampus

Carbon nanotubes are promising nanomaterials for the diagnosis and treatment of brain disorders. However, the ability of these nanomaterials to cross cell membranes and interact with neural cells brings the need for the assessment of their potential adverse effects on the nervous system. This study aimed to investigate the biopersistence of single-walled carbon nanotubes functionalized with polyethylene glycol (SWCNT-PEG) directly infused into the rat hippocampus. Contextual fear conditioning, Y-maze and open field tasks were performed to evaluate the effects of SWCNT-PEG on memory and locomotor activity. The effects of SWCNT-PEG on oxidative stress and morphology of the hippocampus were assessed 1 and 7 days after infusion of the dispersions at 0.5, 1.0 and 2.1 mg/mL. Raman analysis of the hippocampal homogenates indicates the biopersistence of SWCNT-PEG in the hippocampus 7 days post-injection. The infusion of the dispersions had no effect on the acquisition or persistence of the contextual fear memory; likewise, the spatial recognition memory and locomotor activity were not affected by SWCNT-PEG. Histological examination revealed no remarkable morphological alterations after nanomaterial exposure. One day after the infusion, SWCNT-PEG dispersions at 0.5 and 1.0 mg/mL were able to decrease total antioxidant capacity without modifying the levels of reactive oxygen species or lipid hydroperoxides in the hippocampus. Moreover, SWCNT-PEG dispersions at all concentrations induced antioxidant defenses and reduced reactive oxygen species production in the hippocampus at 7 days post-injection. In this work, we found a time-dependent change in antioxidant defenses after the exposure to SWCNT-PEG. We hypothesized that the persistence of the nanomaterial in the tissue can induce an antioxidant response that might have provided resistance to an initial insult. Such antioxidant delayed response may constitute an adaptive response to the biopersistence of SWCNT-PEG in the hippocampus.

Implications of PEGylation of Carbon Nanotubes for Central Nervous System Bioavailability

BACKGROUND AND OBJECTIVE In this mini-review, we have compiled the most recent and comparable information to shed light on the action of PEGylation in the biodistribution of carbon nanotubes (CNT) in the central nervous system (CNS). It is well known that due to the complexity of the CNS and the severity of the outcome following changes in this system, this is one of the areas where there are more investments in research to develop new technologies and approaches for more effective and less invasive treatments. The CNS is highly protected against toxic and invasive microorganisms thanks to the blood brain barrier (BBB), but this protection also prevents the passage of potentially beneficial molecules for the treatment of neurological disorders. Nanotechnology attempts to develop nanocompounds that are biocompatible and non-immunogenic, and that are able to cross the BBB in therapeutic amounts without causing damage and to diffuse through nerve tissue. These compounds should also be cleared and biodistributed properly, being capable of performing drug delivery exclusively for CNS pathologies, such as neurodegenerative diseases (Parkinsons and Alzheimers) and brain tumors. CONCLUSION In this way, this review focuses on CNT PEGylation, aiming to help in the development of viable and effective nanomedicines for neuroscience applications.