This study focused on using carbon-14-labeled fewlayer graphene (FLG) to determine its uptake,d istribution, transformation, and depuration in rice plants.A fter 7d hydroponic exposure to FLG suspension at 250 mgL À1 ,r oots accumulated 694.8 mg kg À1 graphene and shoots had 53.7 mg kg À1 graphene from intra-plant translocation. FLG could likely pass through the cell wall and membrane and enter the chloroplast in the shoots.After 14 days of depuration, only about 15 %o ft he accumulated FLG were eliminated into the depuration solution with about 70 %o fg raphene retained in the plants.A bout 9% of the accumulated FLG was degraded to 14 CO 2 and proposed that reaction with OHC in the leaves may likely contribute to the degradation of FLG,w hichh ad structural defects.T hese findings have an important impact on the long-term environmental fate of graphene-related materials in soil-plant systems.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Understanding the colloidal stability of graphene is essential for predicting its transport and ecological risks in aquatic environments. We investigated the agglomeration of 14C-labeled few-layer graphene (FLG) at concentrations spanning nearly four orders of magnitude (2 μg/L to 10 mg/L) using dynamic light scattering and sedimentation measurements. FLG agglomerates formed rapidly in deionized water at concentrations > 3 mg/L. From 1 mg/L to 3 mg/L, salt-induced agglomeration was decreased with dilution of FLG suspensions; the critical coagulation concentration of the more concentrated suspension (3 mg/L) was significantly lower than the dilute suspension (1 mg/L) in the presence of NaCl (1.6 mmol/L and 10 mmol/L, respectively). In contrast, FLG underwent slow agglomeration and settling at concentrations ≤ 0.1 mg/L in NaCl solutions and ambient waters with low ionic strength (< 10 mmol/L). Although salt-induced agglomeration led to 67 % reduction in number of small FLG (25 nm to 50 nm) according to atomic force microscopy characterization, transition from concentrated to dilute suspension retarded the removal of the small FLG. Additionally, the small FLG exhibited greater bioaccumulation in zebrafish embryo and stronger chorion penetration ability than larger ones. These findings suggest that FLG at more environmentally relevant concentration is relatively stable and may have implications for exposure of small FLG to ecological receptors.

Effective detection of DNA methyltransferase (DNMT) activity is significant for cancer research. Herein, we developed a sensitive electroanalytical method to detect human DNA (cytosine-5)-methyltransferase 1 (DNMT1) from crude lysates of cancer cells. In this assay, capture DNA having a preferred DNMT1 methylation site was immobilized on a gold electrode and then hybridized with gold nanoparticle (Au NP)-DNA complexes. The modified electrodes were equilibrated with the lysate and then incubated with methylation-sensitive restriction enzyme. If the lysate was negative for DNMT1 activity, the Au NP-DNA complexes would be cut by the restriction enzyme and released from the electrode. Conversely, restriction enzyme cleavage would be blocked by the fully methylated duplexes, and the Au NP-DNA complexes would remain on the electrode. Electroactive Ru(NH) was used as the signal reporter, because of its electrostatic attraction to DNA, resulting in an electrochemical signal. Since the electrochemical signal reflects the amount of Ru(III) redox and the amount of Ru(III) redox is correlated with the activity of DNMT1, the activity of DNMT1 is proportional to the electrochemical signal. The signal could be amplified by the numerous DNAs on the Au NPs and further amplified by Ru(III) redox recycling. With this method, a detection limit down to 0.3 U/mL for pure DNMT1 and 8 MCF-7 cells was achieved. DNMT1 activities of different cell lines were also successfully evaluated.