Coenzyme Q10-loaded nanoemulsion hydrophilic gel: Development, characterization, stability evaluation and in vivo effects in skin

Abstract

This study aimed to develop a physically and chemically stable hydrogel, which contains coenzyme Q10 (Q10)-loaded nanoemulsion, able to reduce transepidermal water loss (TEWL) and enhance skin hydration. Q10-loaded nanoemulsion was, after its characterization (particle size, polydispersity index (PDI), oxidation index, pH value, Q10-content, and electron microscopy) incorporated into a carbomer gel. The prepared Q10-loaded nanoemulsion gel was analyzed for its rheological parameters, pH value and Q10-content, after its preparation (48 h), after the stress test (5 cycles; 1 cycle: 24 h at 4 °C, 24 h at 20±2 °C and 24 h at 40 °C) and at predetermined time intervals during its storage at 20±2 °C and at 40 °C for six months. The Q10-loaded nanoemulsion gel, plain Q10-gel, Q10-free nanoemulsion gel and placebo carbomer gel were investigated in vivo for their effects in 15 human volunteers, during their 28 days’ application onto the skin. Skin hydration and TEWL were determined before starting the treatment, during 28 days of treatment, and 4 days after treatment completion. The results showed that the Q10-nanoemulsion was of a sufficiently low particle size (307,4 ± 0,5 nm) and homogeneity (PDI = 0.270 ± 0.002) for skin application, and that its characteristics were not changed by its incorporation into the gel. A shear-thinning plastic flow behavior was seen for the Q10-nanoemulsion gel. The stress test as well as storage at 20±2 °C and 40 °C did not change the rheological parameters of the gel. However, Q10-content decreased in the Q10-loaded nanoemulsion gel, but less compared to the Q10-gel. The developed Q10-nanoemulsion gel was able to significantly decrease TEWL compared to untreated skin (control), while it was not able, without the addition of a moisturizing agent (hyaluronic acid) and emollient (C12-15 alkyl benzoate) to increase skin hydration compared to control. Thus, besides the addition of a Q10-nanoemulsion into a hydrogel, it is necessary to add moisturizers and/or emollients to increase skin hydration.