Search

How graphene oxide (GO) derivatives might affect the cell cycle has been rarely studied. Herein, a GO derivative was fabricated by functionalization of GO with polyethylene glycol (PEG) and polyethylenimine (PEI), and its cytotoxic mechanism was investigated in-depth. It was found that our obtained GO-PEG-PEI nanosheets, not the cytotoxic coating polymer PEI, could induce defect in S phase of the mammalian cell cycle, resulting in decreased DNA synthesis, S phase arrest, and abnormal cytoskeleton structure. Further analysis demonstrated that this damaging effect on S phase could be detected in all five tested mammalian cell lines. Even at seemingly safe concentration (∼90% cells viable), GO-PEG-PEI could still induce S phase defect. Detailed investigations revealed that GO-PEG-PEI could cause genomic DNA damage, activating the intra-S-phase checkpoint control via both the ATM and the ATR signaling pathways. Our work unveils the signaling pathways involved in the interaction of GO-PEG-PEI with mammalian cells, and highlights the necessity and importance of comprehensive investigations of the effects of nanomaterials on cellular pathways, such as the cell cycle in this case, even for those with seemingly little/low cytotoxicity during preliminary evaluations. Our work also highlights the critical roles of surface chemistry in biological effects of nanomaterials. [ABSTRACT FROM AUTHOR]

Whether graphene and graphene oxide (GO) would affect the activities of bacteria has been under debate. Nevertheless, how graphene derivatives with biocompatible coatings interact with microorganisms and the underlying mechanisms are important issues for nanobiotechnology, and remain to be further explored. Herein, three new types of nano-GOs functionalized with polyethylene glycol (nGO-PEGs) were synthesized by varying the PEGylation degree, and their effects on Escherichia coli ( E. coli ) were carefully investigated. Interestingly, nGO-PEG (1:1), the one with relatively lower PEGylation degree, could significantly stimulate bacterial growth, whereas as-made GO and the other two nGO-PEGs showed no effect. Further analysis revealed that nGO-PEG (1:1) treatment significantly accelerated FtsZ-ring assembly, shortening Phase 1 in the bacterial cell cycle. Both DNA synthesis and extracellular polymeric substance (EPS) secretion were also dramatically increased. This unique phenomenon suggests promising potentials in microbial engineering as well as in clinical detection of bacterial pathogens. As a proof-of-concept, nGO-PEG (1:1) treatment could remarkably enhance (up to 6-fold) recombinant protein production in engineered bacteria cells. To our best knowledge, this is the first demonstration of functionalized GO as a novel, positive regulator in microbial engineering. Moreover, our work highlights the critical role of surface chemistry in modulating the interactions between nanomaterials and microorganisms. [ABSTRACT FROM AUTHOR]