Ultra-small lipid nanoparticles promote the penetration of coenzyme Q10 in skin cells and counteract oxidative stress

• Uptake of CoQ10 into HaCaTs by ultra-small lipid nanoparticles (usNLC).
• usNLC were distributed within the cytoplasm of HaCaT cells.
• Electron paramagnetic resonance measurements to detect radicals in cells.
• usNLC-CoQ10 demonstrated the strongest reduction of radical formation.
• Antioxidant effectiveness of usNLC-CoQ10 compared to conventional nanocarriers.

UV irradiation leads to the formation of reactive oxygen species (ROS). An imbalance between the antioxidant system and ROS can lead to cell damage, premature skin aging or skin cancer. To counteract these processes, antioxidants such as coenzyme Q10 (CoQ10) are contained in many cosmetics. To improve and optimize cell/tissue penetration properties of the lipophilic CoQ10, ultra-small lipid nanoparticles (usNLC) were developed. The antioxidant effectiveness of CoQ10-loaded usNLC compared to conventional nanocarriers was investigated in the human keratinocyte cell line HaCaT. Using confocal laser scanning microscopy investigations of the carriers additionally loaded with nile red showed a clear uptake into cells and their distribution within the cytoplasm. By use of the XTT cell viability test, CoQ10 concentrations of 10–50 μg/ml were shown to be non-toxic, and the antioxidant potential of 10 μg/ml CoQ10 loaded usNLC in the HaCaT cells was analyzed via electron paramagnetic resonance spectroscopy after cellular exposure to UVA (1 J/cm2) and UVB (18 mJ/cm2) irradiation. In comparison with the CoQ10-loaded conventional carriers, usNLC-CoQ10 demonstrated the strongest reduction of the radical formation; reaching up to 23% compared to control cells without nanocarrier treatment. Therefore, usNLC-CoQ10 are very suitable to increase the antioxidant potential of skin.

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