Comparative Evaluation of the Effect of Permeation Enhancers, Lipid Nanoparticles and Colloidal Silica on in vivo Human Skin Penetration of Quercetin

<b><i>Background/Aim:</i></b> The aim of this study was to evaluate emulsions containing a penetration enhancer, lipid nanoparticles (LNs) or colloidal silica as systems to improve the topical delivery of the flavonoid quercetin. <b><i>Methods:</i></b> The skin penetration of quercetin was investigated in vivo on human volunteers by tape stripping. Quercetin-loaded LNs were prepared using hot high-pressure homogenization and characterized by means of dynamic light scattering and release studies. The location of the silica nanoparticles in the skin was determined by inductively coupled plasma mass spectrometry assay of silicon in the stratum corneum strips. <b><i>Results and Conclusions:</i></b> The penetration enhancer diethylene glycol monoethyl ether did not produce any significant increase in the fraction of the applied quercetin dose permeated in vivo into human stratum corneum (17.1 ± 3.2%) compared to the control emulsion (18.1 ± 2.3%). A greater but statistically nonsignificant accumulation of the flavonoid in the human horny layer (21.2 ± 2.9% of the applied dose) was measured following topical application of quercetin-loaded LNs (mean particle size: 527 nm). On the other hand, the addition of colloidal silica (average particle diameter: 486 nm) to the emulsion (2%, w/w) significantly increased the in vivo uptake of quercetin by the human stratum corneum to 26.7 ± 4.1% of the applied dose, the enhancing effect on permeation being more marked in the deepest horny layer strips. The measured in vivo skin penetration profile of colloidal silica showed that silica particles diffused down to the intermediate region of the human horny layer and hence could act as carrier for quercetin.