Effects of Three Carbonaceous Nanomaterials on the Developmental Toxicity, Oxidative Stress, and Metabolic Profile in Zebrafish

Comparative evaluation of the mechanisms of toxicity of graphene oxide and graphene oxide quantum dots to blue-green algae Microcystis aeruginosa in the aquatic environment

The geometry-dependent regulation of hepatic stellate cells by graphene oxide nanomaterials

Graphene oxide (GO) has been demonstrated to be an effective hydrophilic nanofiller to modify the polymeric membranes when forming a mixed matrix structure. GO quantum dots (QDs) are promising candidates to fully exert the rich oxygen containing functional groups due to their unique size induced edge effects. In this work, GO QDs modified polysulfone (PSF) ultrafiltration (UF) membranes were prepared by phase inversion method with various GO QDs loadings (0.1–0.5 wt.%). A proper amount of GO QDs addition led to a more porous and hydrophilic membrane structure. With 0.3 wt.% GO QDs, the membranes showed a 60% increase in permeability (130.54 vs . 82.52 LMH bar–1 ). The pristine PSF membranes had a complete cutoff of bovine serum albumin molecules and it was well maintained with GO QDs incorporated. The membranes with 0.5 wt.% GO QDs exhibited the highest flux recovery ratio of 89.7% and the lowest irreversible fouling of 10.3% (54.5% and 33.3% for the pristine PSF membranes). Our results proved that GO QDs can function as effective nanofillers to enhance the hydrophilicity, permeability and antifouling performance of PSF UF membranes.

A comparative study on the effects of ultrathin luminescent graphene oxide quantum dot (GOQD) and graphene oxide (GO) nanosheets on the interfacial interactions and mechanical properties of an epoxy composite

Graphene and its derivatives, graphene oxide (GO) and graphene oxide quantum dots (GOQDs), have recently attracted much attention as bioactive factors in differentiating stem cells towards osteoblastic lineage. The stem cells from human exfoliated deciduous teeth (SHEDs) possess the properties of self-renewal, extensive proliferation, and multiple differentiation potential, and have gradually become one of the most promising mesenchymal stem cells (MSCs) in bone tissue engineering. The purpose of this study was to explore the effects of GO and GOQDs on the osteogenic differentiation of SHEDs. In this study, GO and GOQDs facilitated SHED proliferation up to 7 days in vitro at the concentration of 1 μg/ml. Because of their excellent fluorescent properties, GOQD uptake by SHEDs was confirmed and distributed in the SHED cytoplasm. Calcium nodules formation, alkaline phosphatase (ALP) activity, and RNA and protein expression increased significantly in SHEDs treated with osteogenic induction medium containing GOQDs but decreased with osteogenic induction medium containing GO. Interestingly, the Wnt/β-catenin signaling pathway appeared to be involved in osteogenic differentiation of SHEDs induced with GOQDs. In summary, GO and GOQDs at the concentration of 1 μg/ml promoted SHED proliferation. GOQDs induced the osteogenic differentiation of SHEDs, whilst GO slightly inhibited it.

Nanotoxicology is argued and considered one of the emerging topics. In this study, polyaniline (PANI)/2-acrylamido-2-methylpropanesulfonic acid (AMPSA) capped silver nanoparticles (NPs)/graphene oxide (GO) quantum dots (QDs) nanocomposite (PANI/Ag (AMPSA)/GO QDs NC) as a nanoadsorbent has a potential for removal of toxic hexavalent chromium (Cr(VI)) ions from water. The acute toxicity of this NC was evaluated on Artemia salina and freshwater Ostracods (Cypridopsis vidua) larvae for 48 h. The measurements were made at 24 and 48 h with 3 repetitions. The 50% effective concentration (EC50) values of the NC were determined after the exposure of these organisms. According to the results of the optical microscope, it was found that both experimental organisms intake the NC. In the toxicity results of Ostracods, the NC had a highly toxic effect only at 250 mg/L after 48 h and the EC50 value was 157.6 ± 6.4 mg/L. For Artemia salina individuals, it was noted that they were less sensitive than the Ostracods and EC50 value was 476 ± 25.1 mg/L after 48 h. These results indicated that PANI/Ag (AMPSA)/GO QDs NC has low toxicity towards both investigated organisms.

Selective determination of toxic hexavalent chromium (Cr(VI)) is a stringent important due to its huge negative impact on the health and environment. Recently, the high sensitivity, rapidness, and cost-effectiveness of the fluorescent sensors for Cr(VI) have been developed. A fluorescent nanocomposite (NC) has been synthesized based on doped polyaniline (PANI), 2-acrylamido-2-methylpropanesulfonic acid (AMPSA) capped Ag nanoparticles (NPs) and graphene oxide (GO) quantum dots (QDs) via in situ reaction for highly selective sensing of Cr(VI) ions based on the luminescent quenching in the range from 0.01 to 7.5 mg/L. This NC showed an emission peak at 348 nm with a linear range from 0.01 to 0.05 mg/L and the low limit of detection (LOD) was 0.0065 mg/L (~ 6 µg/L). PANI/Ag (AMPSA) GO QDs NC displayed high selectivity for Cr(VI) over other common metal ions. Notably, the PANI/Ag (AMPSA) GO QDs NC can be used for distinguishing Cr(VI) and Cr(III) in solutions. The sensitive determination of Cr(VI) in real surface water samples was also confirmed and demonstrated recoveries in the range 95.3–99.2%. This NC will emerge as a new class of fluorescence materials that could be suitable for practical applications.

Both oxidative stress and neurotoxicity are huge challenges to human health, and effective methods and agents for resisting these adverse effects are limited, especially in vivo. It is shown here that, compared to large graphene oxide (GO) nanosheets, GO quantum dots (GOQDs), as nanozymes, efficiently reduce reactive oxygen species (ROS) and H2O2 in 1‐methyl‐4‐phenyl‐pyridinium ion (MPP+)‐induced PC12 cells. In addition, GOQDs exert neuroprotective effects in a neuronal cell model by decreasing apoptosis and α‐synuclein. GOQDs also efficiently diminish ROS, apoptosis, and mitochondrial damage in zebrafish treated with MPP+. Furthermore, GOQDs‐pretreated zebrafish shows increased locomotive activity and Nissl bodies in the brain, confirming that GOQDs ameliorate MPP+‐induced neurotoxicity, in contrast to GO nanosheets. GOQDs contribute to neurotoxic amelioration by increasing amino acid metabolism, decreasing tricarboxylic acid cycle activity, and reducing steroid biosynthesis, fatty acid biosynthesis, and galactose metabolic pathway activity, which are related to antioxidation and neurotransmission. Meanwhile, H2O2 decomposition and Fenton reactions suggest the catalase‐like activity of GOQDs. GOQDs can translocate into zebrafish brains and exert catalase‐mimicking activity to resist oxidation in the intracellular environment. Unlike general nanomaterials, biocompatible GOQDs demonstrate their high potential for human health by reducing oxidative stress and inhibiting neurotoxicity.

Graphene quantum dots (GQDs) have garnered significant attention across numerous fields due to their ultrasmall size and exceptional properties. However, their extensive applications may lead to environmental exposure and subsequent uptake by humans. Yet, conflicting reports exist regarding the potential toxicity of GQDs based on experimental investigations. Therefore, a comprehensive understanding of GQD biosafety requires further microscopic and molecular-level investigations. In this study, we employed molecular dynamics (MD) simulations to explore the interactions between GQDs and graphene oxide quantum dots (GOQDs) with a protein model, the human intestinal fatty acid binding protein (HIFABP), that plays a crucial role in mediating the carrier of fatty acids in the intestine. Our MD simulation results reveal that GQDs can be adsorbed on the opening of HIFABP, which serves as an entrance for the fatty acid molecules into the protein’s interior cavity. This adsorption has the potential to obstruct the opening of HIFABP, leading to the loss of its normal biological function and ultimately resulting in toxicity. The adsorption of GQDs is driven by a combination of van der Waals (vdW), π-π stacking, cation-π, and hydrophobic interactions. Similarly, GOQDs also exhibit the ability to block the opening of HIFABP, thereby potentially causing toxicity. The blockage of GOQDs to HIFABP is guided by a combination of vdW, Coulomb, π-π stacking, and hydrophobic interactions. These findings not only highlight the potential harmful effects of GQDs on HIFABP but also elucidate the underlying molecular mechanism, which provides crucial insights into GQD toxicology.

Evaluation of crystal size present in graphene oxide quantum dots using optical and Raman spectroscopy

Effect of graphene oxide on the uptake, translocation and toxicity of metal mixture to Lepidium sativum L. plants: Mitigation of metal phytotoxicity due to nanosorption

Short-term developmental effects and potential mechanisms of azoxystrobin in larval and adult zebrafish (Danio rerio)

Graphene oxide (GO) is a semiconductor that can absorb light to generate electron-hole pairs for photocatalytic reactions. GO is a suitable medium for photocatalytic reactions in an aqueous solution because it is highly dispersed in water. Our study tuned the electronic properties of GO by varying its size and the embedded functionalities. As-received GO was a p-type semiconductor. We doped nitrogen into the GO sample by ammonia treatment and converted the conductivity type. We also reduced the size of the GO sample to increase the surface area. Size modulation along with chemical modification represent a means to tune the photocatalytic activity of GO. We obtained GO quantum dots (GOQDs) that exhibited size-dependent photoluminescence emissions. Presence of nitrogen functionalities in GOQDs eliminated vacancy defect states to suppress charge recombination and resulted in the conjugation of nitrogen lone-pair electrons with the aromatic p orbitals. The Pt-deposited nitrogen-doped GOQDs effectively catalyzed H2 evolution from a triethanolamine aqueous solution. The quantum yield for H2 evolution reached 20 % under monochromatic irradiation at 420 nm.

A one-pot synthesis of graphene oxide (GO) sheets and GO quantum dots using graphite nanofibers (GNF) as starting material is reported. Two types of GNF starting materials, namely herringbone and platelet structures, were used. HRTEM revealed that platelet GNF produces quantum dots typically less than 10 nm in size while herringbone GNF produces relatively larger GO sheets. SAED patterns indicate that the produced GO sheets have a hexagonal crystal structure. UV–Vis, PL, XPS, and Raman show salient differences between the produced GO nanostructures which correlate well with the morphological analysis. Unlike the GO sheets, the GO quantum dots are photoluminescent. The difference in PL properties was attributed to the higher oxygen content in GO quantum dots which were shown by XPS. The results offer a new insight to the importance of starting material in the synthesis of graphene nanostructures.

A facile chemical method of acid treatment has been followed for the cutting of graphene oxides sheet to extract graphene oxide quantum dots (GOQDs) in aqueous medium at different pH. Strong blue emission and excitation dependent photoluminescence (PL) spectrum are observed in GOQDs. Relative PL quantum yield is measured as high as ∼30% for the GOQDs synthesized at pH11. Presence of defect related states and oxygen containing functional groups in GOQDs are confirmed through Raman and Fourier transform infrared analysis, respectively. High resolution transmission electron microscopy analysis suggests that the sizes of GOQDs are distributed in the range ∼2.0–8.0 nm with d-spacing of 0.245 nm. AFM measurement confirms the topography height of GOQDs in the range ∼6.0–9.0 nm. Synthesized GOQDs at different pH are dispersed in poly (vinyl alcohol) (PVA) matrix and spin coated to fabricate polymer nanocomposites (PNCs) devices. Electrical studies have been performed which display write-once-read-many characteristics and the set voltage () increases with the increase in pH of the GOQDs. Very low ∼−0.9 V and ∼104 have been obtained for the device containing GOQDs synthesized at pH1. Retention tests up to 104 s are performed for the PNCs devices in order to confirm the stability. A suitable energy band diagram is proposed to discuss the carrier transport through the composites devices.