PREPARATION AND CHARACTERIZATION OF UREA NIOSOMES - IN-VITRO AND IN-VIVO STUDIES

In this study, several cosmetic urea formulations containing phospholi pids, a charge inducer with or without cholesterol (liposomes) and a n on-ionic surfactant, a charge inducer with cholesterol (niosomes), wer e investigated, We used comparable liposome and niosome formulations f rom various phospholipids and surfactants to investigate whether gel a nd liquid crystalline state vesicles differ in their effect on skin hy dration. Gel state liposomes and niosomes, liquid crystalline state li posomes and niosomes were prepared. The film method was used, followed by sonication and extrusion through a polycarbonate membrane. The par ticle size distribution, entrapment efficiency, content of phospholipi d and bilayer type and composition stability were determined. In vitro release of urea was investigated at 37 degrees C, 35 r/min in 10 mM T ris (pH 7.4) buffer In vitro release was investigated and its fit to k inetic models was evaluated. All vesicles were labelled by Tc-99m and applied topically to the back of guinea pigs. The biodistribution was compared with that of a commercial product. The same formulations were applied to human volunteers. The moisturizing effect was determined b y Sebutest based on the differing dielectric constants of water and ot her substances. In this study, skin humidity could be increased and ac cumulation of urea-loaded vesicles in the stratum corneum could be dem onstrated. No particular affinity of the phospholipids/surfactants for the deeper-lying skin tissues could be demonstrated.