Recent toxicological studies on carbon nanomaterials, including fullerenes, have led to concerns about their safety. Functionalized fullerenes, such as polyhydroxy fullerenes (PHF, fullerols, or fullerenols), have attracted particular attention due to their water solubility and toxicity. Here, we report surprisingly beneficial and/or specific effects of PHF on model organisms representing four kingdoms, including the green algae Pseudokirchneriella subcapitata, the plant Arabidopsis thaliana, the fungus Aspergillus niger, and the invertebrate Ceriodaphnia dubia. The results showed that PHF had no acute or chronic negative effects on the freshwater organisms. Conversely, PHF could surprisingly increase the algal culture density over controls at higher concentrations (i.e., 72% increase by 1 and 5 mg/L of PHF) and extend the lifespan and stimulate the reproduction of Daphnia (e.g. about 38% by 20 mg/L of PHF). We also show that at certain PHF concentrations fungal growth can be enhanced and Arabidopsis thaliana seedlings exhibit longer hypocotyls, while other complex physiological processes remain unaffected. These findings may open new research fields in the potential applications of PHF, e.g., in biofuel production and aquaculture. These results will form the basis of further research into the mechanisms of growth stimulation and life extension by PHF.

Nanoparticles (NPs) have been attracting much attention for biomedical and pharmaceutical applications. In most of the applications, NPs are required to translocate across the cell membrane and to reach the cell cytosol. Experimental studies have reported that by applying an electric field NPs can directly permeate across the cell membrane without the confinement of NPs by endocytic vesicles. However, damage to the cell can often be a concern. Understanding of the mechanism underlying the direct permeation of NPs under an external electric field can greatly contribute to the realization of a technology for the direct delivery of NPs. Here we investigated the permeation of a cationic gold NP across a phospholipid bilayer under an external electric field using a coarse-grained molecular dynamics simulation. When an external electric field that is equal to the membrane breakdown intensity was applied, a typical NP delivery by electroporation was shown: the cationic gold NP directly permeated across a lipid bilayer without membrane wrapping of the NP, while a persistent transmembrane pore was formed. However, when a specific range of the electric field that is lower than the membrane breakdown intensity was applied, a unique permeation pathway was exhibited: the generated transmembrane pore immediately resealed after the direct permeation of NP. Furthermore, we found that the affinity of the NP for the membrane surface is a key for the self-resealing of the pore. Our finding suggests that by applying an electric field in a suitable range NPs can be directly delivered into the cell with less cellular damage.

Nanoparticles have attracted much attention as a key material for new biomedical and pharmaceutical applications. For success in these applications, the nanoparticles are required to translocate across the cell membrane and to reach to inside of the cell. Among several translocation pathways of nanoparticles, the direct permeation pathway has a great advantage due to its high delivery efficacy. However, despite many research efforts, key properties and factors for driving the direct permeation of nanoparticle and its underlying mechanisms are far from being understood. In this article, experimental and computational studies regarding the direct permeation of nanoparticles across a cell membrane will be reviewed. Firstly, experimental studies on the nanoparticle-cell interactions, where spontaneous direct permeation of nanoparticles was observed, are reviewed. From the experimental studies, potential key physico-chemical properties of nanoparticles for their direct permeation are discussed. Secondly, physical methods such as electroporation and sonoporation for delivering nanoparticles into cells are reviewed. Current status of technologies for facilitating the direct permeation of nanoparticle is presented. Finally, we review molecular dynamics simulation studies and present the latest findings on the underlying molecular mechanisms of the direct permeation of nanoparticle.

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