Aminoglycoside-induced hair cell (HC) loss is one of the most important causes of hearing loss. After entering the inner ear, aminoglycosides induce the production of high levels of reactive oxygen species (ROS) that subsequently activate apoptosis in HCs. Citicoline, a nucleoside derivative, plays a therapeutic role in central nervous system injury and in neurodegenerative disease models, including addictive disorders, stroke, head trauma, and cognitive impairment in the elderly, and has been widely used in the clinic as an FDA approved drug. However, its effect on auditory HCs remains unknown. Here, we used HC-like HEI-OC-1 cells and whole organ explant cultured mouse cochleae to explore the effect of citicoline on aminoglycoside-induced HC damage. Consistent with previous reports, both ROS levels and apoptosis were significantly increased in neomycin-induced cochlear HCs and HEI-OC-1 cells compared to undamaged controls. Interestingly, we found that co-treatment with citicoline significantly protected against neomycin-induced HC loss in both HEI-OC-1 cells and whole organ explant cultured cochleae. Furthermore, we demonstrated that citicoline could significantly reduce neomycin-induced mitochondrial dysfunction and inhibit neomycin-induced ROS accumulation and subsequent apoptosis. Thus, we conclude that citicoline can protect against neomycin-induced HC loss by inhibiting ROS aggregation and thus preventing apoptosis in HCs, and this suggests that citicoline might serve as a potential therapeutic drug in the clinic to protect HCs.

Phosphorus (P)-doping in vacancies of graphene sheets can significantly change graphene's physical and chemical properties. Generally, a high level for P-doping is difficult due to the low concentration of vacancy but is needed to synthesize graphene with the perfect properties. Herein, we synthesized the P-superdoped graphene with the very high P content of 6.40 at. % by thermal annealing of fluorographite (FGi) in P vapor. Moreover, we show that the Pdoping level can be adjusted in the wide range from 2.86 to 6.40 at. % by changing the mass ratio of red phosphorus to FGi. The magnetic results show that (i) Pdoping can effectively create localized magnetic moments in graphene; (ii) the higher the doping level of sp 3 -type PO x groups, the higher the magnetization of Psuperdoped graphene is; and (iii) the high P-doping levels can lead to the coexistence of antiferromagnetic and ferromagnetic behavior. It is proposed that the sp 3 -type PO x groups are the major magnetic sources.

Monolayer graphene oxide quantum dots (GOQDs) were obtained by oxidative cutting. The magnetic properties of GOQDs were studied. The results show that most of GOQDs are nonmagnetic, and only few of GOQDs are weakly paramagnetic. The ratio of magnetic GOQDs with the average diameter of 4.13, 3.3, and 1.67 nm is 1/14, 1/15, and 1/70, respectively. It is proposed that the edge states magnetism is suppressed by the edge defects and/or the magnetic correlation induced spins cancellation between magnetic fragments of the boundary, and hydroxyl groups on the basal plane are the major magnetic source of magnetic GOQDs.