Structural characterization and in vivo evaluation of retinyl palmitate in non-ionic lamellar liquid crystalline system

Carrier systems for lipophilic drugs, such as the liquid crystalline systems (LCS) have been extensively studied to improve effect and selectivity. Retinyl palmitate (RP) is widely used in pharmaceutical and cosmetics products to improve the skin elasticity. The aim of this study was the development, characterization and the in vivo effectiveness of RP in non-ionic LCS structures. LCS containing polyether functional siloxane as oil phase, silicon glycol copolymer as surfactant and water in the ratio 30:10:60, with and without RP were studied. The results of the polarized light microscopy, small-angle X-ray scattering and rheology analysis indicated the presence of typical LCS structures with lamellar arrangement. Regardless of the presence of RP, the rheological studies showed the pseudo plastic behavior of the systems. However, highest hysteresis area was verified when comparing the system in the presence and in the absence of RP. Stability study SAXS monitored, carried out up to 30 days in various storage temperature conditions (25 ± 2 °C, 37 ± 2 °C and 5 ± 2 °C) demonstrated the great structural stability of the LCS systems. The in vivo effectiveness analysis suggests that the RP-loaded LCS provided a significant reduction of the orbicular wrinkles in human volunteers (P = 0.048).