Effect of PEGylated Graphene Oxide Nanoparticles on the Functions and Metabolism of THP-1 Cells

Graphene oxide (GO) nanoparticles hold biomedical promise due to unique properties, but their immunomodulatory effects on phagocytes require evaluation, particularly regarding size- and coating-dependent interactions. Polyethylene glycol (PEG) coatings reduce cytotoxicity, yet long-term impacts of varied coatings remain critical. This study investigated PEGylated GO nanoparticles (P-GO) of two lateral sizes (≈100-300 nm and ≈1-1.5 μm) with linear or branched PEG coatings on THP-1 monocyte viability, apoptosis, metabolism, and wide-spectrum cytokine production. Only the larger branched PEG-coated GO (25 μg/mL) exhibited cytotoxicity after 72 h. Other variants showed no cytotoxicity but modulated THP-1 activity. Larger linear PEG-coated GO induced apoptosis within 24 h. All particles in a concentration of 25 μg/mL were internalized by/adhered to cells, suppressed ROS production, and altered cytokine profiles: TNF-α, MIP-1β, MIP-1α, and G-CSF increased, while HGF and SCGF-β decreased. Larger branched PEG-coated GO suppressed oxidative phosphorylation and glycolysis after 24 h. While a spectrum of effects of PEGylated graphene oxide on THP-1 cell functions was identified, predominantly observed at a dose of 25 μg/mL over a 24 to 72-h exposure period, no clear dependence of P-GO nanoparticle effects on THP-1 cells was observed with respect to PEG coating type (linear vs. branched) or particle size. At 5 μg/mL, P-GO caused minimal functional modulation. Thus, the study underscores the potential of low-concentration P-GO for therapeutic use while cautioning that even non-cytotoxic nanoparticles can profoundly alter immune cell behavior.