Liquid Crystal Nanoparticle Conjugates for Scavenging Reactive Oxygen Species in Live Cells

The elevated intracellular production of or extracellular exposure to reactive oxygen species (ROS) causes oxidative stress to cells, resulting in deleterious irreversible biomolecular reactions (e.g., lipid peroxidation) and disease progression. The use of low-molecular weight antioxidants, such as 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), as ROS scavengers fails to achieve the desired efficacy because of their poor or uncontrolled cellular uptake and off-target effects, such as dysfunction of essential redox homeostasis. In this study, we fabricated a liquid crystal nanoparticle (LCNP) conjugate system with the fluorescent dye perylene (PY) loaded in the interior and poly (ethylene glycol) (PEG) decorated on the surface along with multiple molecules of TEMPO (PY-LCNP-PEG/TEMPO). PY-LCNP-PEG/TEMPO exhibit enhanced cellular uptake, and efficient ROS-scavenging activity in live cells. On average, the 120 nm diameter PY-LCNPs were conjugated with >1800 molecules of TEMPO moieties on their surface. PY-LCNP-PEG/TEMPO showed significantly greater reduction in ROS activity and lipid peroxidation compared to free TEMPO when the cells were challenged with ROS generating agents, such as hydrogen peroxide (H2O2). We suggest that this is due to the increased local concentration of TEMPO molecules on the surface of the PY-LCNP-PEG/TEMPO NPs, which efficiently bind to the plasma membrane and enter cells. Overall, these results demonstrate the enhanced capability of TEMPO-conjugated LCNPs to protect live cells from oxidative stress by effectively scavenging ROS and reducing lipid peroxidation.