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.

The functionalization of graphene oxide with organosilanes is an important strategy to yield graphene-silica composites as well as to create nanomaterials for use as reinforcement in polymer nanocomposites and corrosion-inhibiting coatings for metals, among other uses. However, depending on the reaction conditions used, the organosilanes tend to self-condense, encapsulating the graphene oxide in a silica-like layer which can impair its properties by hiding its real surface and two-dimensionality. In this paper we describe a facile route for the functionalization of commercial graphene oxide with (3-aminopropyl) triethoxysilane using low concentrations and mild reaction conditions, and yielding amine and silanol surface-modified graphene nanohybrids while preserving its two-dimensional characteristics. The material obtained was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), potentiometric titration, thermogravimetric analysis and electronic microscopy, evidencing the covalent and superficial nature of the functionalization.

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In this work, we report evidences of the improvement of X-ray attenuation efficiency by the addition of a very small amount of Graphene Oxide (GO) in polymer-based nanocomposite. Poly(vinylidene fluoride) (PVDF) homopolymer and barium sulfate (BaSO4) nanoparticles were mixed. PVDF/BaSO4 nanocomposite was found to attenuate 9.14% of a 20 kV X-ray beam. The addition of only 4.0 wt % of GO nanosheets to the nanocomposite improved this X-Ray attenuation efficiency to 24.56%. The respective linear attenuation coefficients (μ) were 39.9 cm-1 and 54.4 cm-1, respectively. The X-ray attenuation gradually decreases until 6.71% and 17.62%, respectively, for the X-ray beam with higher energy (100 kV). Fourier transform infrared data revealed that, due to the lack of the bending vibration modes of CF2 molecule at 656 cm-1, 688 cm-1, 723 cm-1, 776 cm-1and 796 cm-1, characteristics of the γ-crystalline phase of PVDF, the nanocomposites casted from solution are mostly in the β-ferroelectric phase of PVDF, besides the γ-paraelectric phase. SEM micrographs were used to evaluate the dispersion state of graphene sheets and the BaSO4 nanoparticles into the polymeric matrix. UV-Vis spectrometry and Differential Scanning Calorimetry (DSC) were also performed in order to complement the structural analysis. The results confirm that the addition of graphene sheets in PVDF polymer-based nanocomposites enhances the X-ray shielding efficiency. The phenomenon is discussed in terms of the reported anomalous negative thermal expansion coefficient of graphene sheets