The Effect of Pristine and Pegylated Graphene Oxide Nanosheets on the Functions of Human Neutrophils

Graphene oxide (GO) is very useful for biomedicine, due to its physicochemical properties; therefore, its interaction with cells of the immune system has beenextensively studied. Many studies have aimed toreduce the undesirable effects of GO through chemical modification, including through polyethylene glycol (PEG) coating. Neutrophils are the first to respond to foreign object invasion in the body. Their main functions are the uptake and destruction of foreign particles, including with the help of reactive oxygen species (ROS).Our study aimed to investigate theengulfment of unmodified graphene oxide (GO) and graphene oxide coated with polyethylene glycol (GO-PEG) by human neutrophils and the effect of nanosheets on the production of ROS.We used sheets of GO (Ossila, Great Britain, average plate size 1-5 μm) and GO-PEG (569 ± 14 nm, PEG coating≈ 20%) at concentrations of 12.5μg/mL, 25μg/mL, and 50 μg/mL. The uptake of nanosheets was assessed by flow cytometry, taking into account the level of background adhesion of nanoparticles. ROS production was evaluated by luminol-dependent chemiluminescence (LCL).It was found that GO (12.5μg/mL, 25μg/mL, and 50 μg/mL) was actively internalized by neutrophils, while the uptake of GO-PEG was not detected. GO and GO-PEG particles (25 μg/mLand 50 μg/mL) reduced the total production of ROS by human leukocytes.Thus, the modifying of GOnanosheets with PEG resulted in the abolishment of their active uptake by neutrophils but did not affect the GO inhibitory effect on their oxidative activity. Keywords: graphene oxide surface modification, pegylated graphene oxide nanosheets, nanoparticle uptake, human neutrophils, of reactive oxygen specie