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

Efficient and safe gene transfection in fish spermatogonial stem cells using nanomaterials

Multiwalled carbon nanotubes (MWCNTs), nanographene oxide (NGO), and gold nanorods (NRs) can be functionalized and complexed to DNA to promote efficient gene delivery to Nile tilapia spermatogonial stem cells inducing less cell death than electroporation and the commercial reagents tested. Therefore, nanomaterials can contribute to achieve fish transgenesis. © The Royal Society of Chemistry

Glutatione (GSH) content and glutamate cysteine-ligase (GCL) activity in the hippocampus after the infusion of SWCNT-PEG dispersions.

<p>(A, B) GSH content 1 and 7 days after the infusion. (C, D) GCL activity 1 and 7 days post-injection. Values are expressed as the mean ± SEM, n = 4–6. *<i>p</i> <0.05 vs. the control group.</p

Fluorescence-based <i>in vitro</i> assays.

<p>Values are expressed as the mean ± SEM (n = 4). No significant differences were registered for the different SWCNT-PEG concentrations (<i>p</i>>0.05).</p><p>Fluorescence-based <i>in vitro</i> assays.</p

Effect of SWCNT-PEG dispersions on total antioxidant capacity against peroxyl radicals (ACAP) in the hippocampus (A) 1 and (B) 7 days after infusion.

<p>Values are expressed as the mean ± SEM, n = 4–6. ^#<i>p</i><0.05 vs. 2.1 mg/mL SWCNT-PEG and vs. the control group; *<i>p</i> <0.05 vs. the control group.</p

Effect of SWCNT-PEG dispersions on lipid peroxidation (LPO) in the hippocampus (A) 1 and (B) 7 days after infusion.

<p>Values are expressed as the mean ± SEM, n = 4–6. No significant difference in LPO levels was observed between the groups (<i>p</i>>0.05).</p

Effect of SWCNT-PEG dispersions on (A) acquisition and (B) persistence of contextual fear memory.

<p>Schematics of the procedures used in the experiments are presented above the graphs. Values are expressed as the mean ± SEM, n = 10–12. No significant difference in time spent in freezing was observed between the groups (<i>p</i>>0.05).</p

Levels of reactive oxygen species (ROS) in the hippocampus (A) 1 and (B) 7 days after theinfusion of SWCNT-PEG dispersions.

<p>Values are expressed as the mean ± SEM, n = 4–6. *<i>p</i> <0.05 vs. control group.</p

Raman spectroscopy of rat hippocampal homogenates 1 and 7 days after SWCNT-PEG dispersions infusion.

<p>(A) Raman spectrum acquired from SWCNT-PEG dispersion at 2.1 mg/mL. (B) Detection curve of SWCNT-PEG based on radial breath mode (RBM). Raman spectra in hippocampal homogenates (C) 1 and (D) 7 days after infusion. Dotted squares indicate the RBM region. Ct+: positive control; Ct-: negative control.</p

Effect of SWCNT-PEG on the number of crossings in open field task.

<p>Values expressed as the mean ± SEM (n = 6). Animals tested at 30 min were subjected to another test-session at 1 day. No significant differences were observed between the groups (<i>p</i>>0.05).</p><p>Effect of SWCNT-PEG on the number of crossings in open field task.</p