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 species

Influence of Antimicrobial Nanoparticles on Flexural Strength and Hardness of Polymethylmethacrylate

BACKGROUND: Polymethylmethacrylate (PMMA) is commonly used for dental appliances but has several shortcomings that could benefit from improvement with the use of nanoparticles (NPs). AIM: The purpose of this study was to modify PMMA with three different antimicrobial NPs; Graphene oxide nanosheets (nGO), Titanium dioxide NPs (TiO2 NPs) and curcumin (CUR)-loaded graphene oxide nanosheets alone, and in combination and assess the flexural strength and hardness of the different groups. MATERIALS AND METHODS: The material used in this study was chemically cured PMMA that was modified with nGO, TiO2 NPs and GOCUR alone and in combination to give 6 groups; Group A: PMMA, Group B: PMMA with nGO, Group C: PMMA with TiO2 NPs, Group D: PMMA with TiO2 and GO NPs, Group E: PMMA with GOCUR, and Group F: PMMA with TiO2 NP, and GOCUR. The Six groups were tested for flexural strength and hardness. Statistical analysis was and data were expressed as means and standard deviation. Data was explored for normality using the Kolmogorov-Smirnov test of normality. The ANOVA test was used to compare between groups, followed by Bonferroni’s post hoc test for pairwise comparison. The significance level was set at p ≤ 0.05. RESULTS: The highest flexural strength was recorded in Group C (52.26 ± 5.48 MPa) and the lowest value was in Group A (24.94 ± 5.37 MPa). The highest hardness was recorded in Group F (23.29 ± 0.8 HV) and the lowest value was in Group A (15.88 ± 1.02 HV). CONCLUSION: The modification of PMMA with NPs with proven antimicrobial activity can increase the flexural strength and hardness of the material. GO, TiO2 and, GOCUR NPs were each used alone and in different combinations, and all the groups displayed higher flexural strength and hardness than the unmodified PMMA.