Effects of Lipid Phase Content on the Technological and Sensory Properties of O/W Emulsions Containing Bemotrizinol-Loaded Nanostructured Lipid Carriers

Different lipid phase ratios (12, 14, and 16% w/w) were assessed for their ability to affect the technological and sensory properties of O/W emulsions in which bemotrizinol (BMTZ), a broad-spectrum sunscreen agent, was incorporated free or loaded into nanostructured lipid nanocarriers (NLC) to reduce its release from the vehicle and, hence, its skin permeation. The following technological properties were evaluated in vitro: spreadability, viscosity, pH, occlusion factor, BMTZ release, and sun protection factor (SPF). Sensory attributes were assessed by panelists in three different phases: before/during pick-up, rub-in, and after application. Raising the lipid phase ratio led to an increase in viscosity (from 8017 ± 143 cPs to 16,444 ± 770 cPs) and to a corresponding decrease in spreadability (from 9.35 ± 0.21 cm to 7.50 ± 0.10 cm), while the incorporation of BMTZ-loaded NLC determined a decrease in the occlusion factor (from 47.75 ± 1.16 to 25.91 ± 1.57) and an increase in SPF (from 6% for formulations containing 12% lipid phase to 15% for formulations containing 16% lipid phase). No BMTZ release was observed from all emulsions. Sensory attributes were mainly affected by the lipid phase ratio. These results suggest that the lipid phase ratio and BMTZ incorporation into NLC could contribute to determining the technological and sensory properties of O/W emulsions.