Preparation of silica particles encapsulating retinol using O/W/O multiple emulsions

Retinol, a cosmetic ingredient, was entrapped within inorganic microspheres obtained from sol-gel reaction of TEOS in o/w/o multiple emulsions as microreactors. In o/w/o multiple emulsions, the retinol was emulsified as an internal oil phase in a aqueous solution of 3.0 wt% Tween 20 prior to emulsification into an externa oil phase. The multiple emulsions appeared to be stable enough in the presence of HPC polymer in the external oil phase. In sol-gel reaction, the hydrolysis and condensation rate of TEOS were greatly dependent upon the catalyst and the molar ratio of H2O to TEOS (R-w). In this study, sphere-like microspheres entrapping retinol were best formed with the addition of NH4OH as a catalyst when the concentration of TEOS was at the R-w value of 4. Microspheres obtained under these conditions were 15-40 mum with very dense surfaces containing a few globules 1.17-2.35 mum. Also, they showed the slower release of retinol into the external ethanol phase and higher loading and encapsulation efficiency. (C) 2001 Academic Press.