Lipid-based submicron capsules as a strategy to include high concentrations of a hydrophobic lightening agent in a hydrogel

Objective: This study aimed at increasing the concentration of a hydrophobic lightening agent, Omegalight^® , in a hydrophilic cosmetic product by means of encapsulation in lipid-based submicron capsules. The core of these capsules is entirely made of the commercial lightening agent.

Methods: Lipid-based encapsulation systems (LNC) were prepared by the PIT method. Their physicochemical properties were followed over 6 months by dynamic light scattering and zeta potential measurements, and in parallel, the potential degradation of the active ingredient was monitored by HPLC. The stability of the capsules in a cosmetic gel was studied by spectrofluorimetry and rheology measurements. Sensory analysis was used to determine the influence of the presence of capsules in the gel on the consumer's experience.

Results: LNC encapsulating Omegalight^® were prepared on a laboratory scale and then on a semi-pilot scale. Their hydrodynamic diameters are around 230 nm. The concentration of Omegalight^® in the capsules reaches about 84% w/w, which corresponds to 42% of active ingredient. LNC can be dispersed without degradation at concentrations of up to 20% w/w in a hydrogel without modification of the physicochemical or sensory properties of the gel.

Conclusion: Lipid-based capsules (LNC), an encapsulation system useful for the epidermal delivery of hydrophobic compounds, were adapted to the encapsulation of a commercial lightening agent. The encapsulation permits the dispersion in a stable manner of a very high concentration of a hydrophobic active molecule in a hydrogel while maintaining the physicochemical and sensory properties of the gel.