Preparation of silica particles encapsulating retinol using O/W/O multipleemulsions

Retinol, a cosmetic ingredient, was entrapped within inorganic microspheres obtained from sol-gel reaction of TEOS in o/w/o multiple emulsions as micr oreactors. In o/w/o multiple emulsions, the retinol was emulsified as an in ternal oil phase in a aqueous solution of 3.0 wt% Tween 20 prior to emulsif ication into an externa oil phase. The multiple emulsions appeared to be st able enough in the presence of HPC polymer in the external oil phase. In so l-gel reaction, the hydrolysis and condensation rate of TEOS were greatly d ependent upon the catalyst and the molar ratio of H2O to TEOS (R-w). In thi s study, sphere-like microspheres entrapping retinol were best formed with the addition of NH4OH as a catalyst when the concentration of TEOS was at t he 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.