Topical 915–3985 MHz Microwave Sweep-Assisted Retention of Nanoemulsified α-Tocopherol for Dermatitis Treatment

Being more lipophilic than tocotrienol, tocopherol is anticipated to diffuse into/through skin more than tocotrienol. Microwave sweep treatment of skin may porosify the anatomy and render indifferent permeability regardless of vitamin E lipophilicity. This study explores the microwave sweep (915 to 3985 MHz) impact on skin transport behaviour of nanoemulsified α-tocopherol against nanoemulsified γ-tocotrienol. Physicochemical properties of nanoemulsions and their skin delivery and anti-dermatitis activities were evaluated. Pre-treating skin with 915-3985 MHz microwave sweep formed cavities along epidermal-dermal gradient to retain nanoemulsified α-tocopherol at the expense of skin permeation. In comparison to nanoemulsified γ-tocotrienol, the nanoemulsified α-tocopherol was characterized by higher skin permeation and lower skin retention profiles. The high permeation profile of α-tocopherol was ascribed to facilitated transport by the nanoemulsified structure, higher lipidic character and lower negative zeta potential magnitude undergoing lower skin-nanoemulsion electrostatic repulsion. A higher skin permeation capacity of nanoemulsified α-tocopherol was translated to reduced skin retention and dermatitis healing capacity with reference to transepidermal water loss, skin thickness, suppressive rate, morphology and histological profiles. A high nanoemulsified vitamin E retention in skin, as a function of therapeutic chemistry and microwave sweep, was partly essential to promote the recovery of skin from dermatitis-like inflammation.