Inorganic layered double hydroxides as a 4-hexyl resorcinol delivery system for topical applications

In this study, the hydrophobic even skin tone active, 4-hexylresorcinol (HR), was intercalated into a zinc aluminium layered double hydroxide (ZnAl-LDH) by a co-precipitation method and used as a controlled release ingredient in skin care formulation. The resulting nanohybrid (LDH-HR) was characterized using different techniques: XRD, FTIR, TEM, SEM, and TGA. The intercalation reaction between HR and LDH was confirmed using XRD, and FTIR. Some extent of aggregation was observed for the LDH-HR nanoparticles from TEM and SEM results. The thermal behaviour of HR drastically improved after intercalation into the LDH host. Strong electrostatic interactions between the HR and ZnAl-LDH galleries in the nanohybrid and the sustained release of HR from the LDH-HR in phosphate buffered saline (PBS) were observed. We also investigated the de-pigmenting efficiency of the LDH-HR nanohybrid containing formulations in randomized controlled experiments, which showed impressive results after 14 days of topical applications. The LDH-HR nanohybrid significantly minimized the melanogenesis in primary human melanocytes, resulting in overall improvements in even skin tone. Based on the above results, we believe that the LDH-HR nanohybrid has high potential for use as an alternative active ingredient in topical applications for uneven skin tone.