Surfactant-free microemulsions (SFMEs) exhibited remarkable
advantages
and potential, attributed to their similarity to traditional surfactant-based
microemulsions and the absence of surfactants. Herein, a novel SFME
was developed utilizing cosmetically approved materials, such as short-chain
alcohol as an amphi-solvent, triethyl citrate (TEC) as the nonpolar
phase, and water as the polar phase. 1,2-Pentanediol (PtDO)/TEC/water
combination can form the largest monophasic zone, accounting for ∼74%
of the total phase diagram area, due to an optimal hydrophilic (water)–lipophilic
(TEC) balance. Comparable to surfactant-based microemulsion, PtDO/TEC/water
SFME can also be categorized into three types: water-in-oil, discontinuous,
and oil-in-water. As TEC or water is increased, or PtDO is decreased,
the nanoaggregates in PtDO/TEC/water SFME grow from <5 nm to tens
of nanometers. The addition of α-arbutin (ABN) does not disrupt
PtDO/TEC/water SFME, but rather enhances its formation, resulting
in a larger monophasic area and consistent size (2.8–3.8 nm)
through participating in interface assembly. Furthermore, ABN-loaded
PtDO/TEC/water SFME exhibits remarkable resistance to dilution, exceptional
stability, and minimal irritation. Notably, PtDO/TEC/water SFME significantly
boosts ABN’s solubility in water by 2 times, its percutaneous
penetration rate by 3–4 times, and enables a slow-release DPPH• radical scavenging effect. This SFME serves as a safe
and cosmetically suitable nanoplatform for the delivery of bioactive
substances.