Photoprotection by tocopherol submicron emulsion against UV-mediated damage in HaCaT cells.

alpha-Tocopherol is a lipophilic vitamin E that shows antioxidative, antiaging and antiphotodamage activity. Nanometer biotechnology is more widely used in the entrainment system of drug carriers and the development for new pharmaceutical preparations. Ultraviolet irradiation to human skin in the long term can result in photoaging and photocarcinogenesis. The purpose of this study was to observe the biological features of tocopherol submicron emulsion (vitE SME) and to clarify the roles of vitE SME on UVB-induced photodamage in HaCaT keratinocytes (KC). VitE SME was prepared by high-pressure homogenization and microemulsion technique. HaCaT KC was incubated in the culture medium supplied with 1/200 and 1/400 of VitE SME prior to different dosages of UVB irradiation. The vitamin E amount in the culture medium was measured by high-performance liquid chromatography (HPLC). Cell growth and cellular viability was detected by MTT assay. The amount of vitamin E remaining in the culture medium significantly decreased during the first 8 h, and less than 10% can be detected by the terminal experiment (24 h). No cytotoxicity effect of tocopherol NM on HaCat KC was observed. In contrast to the control group, the cellular viability of VitE SME-treated group increased 44.22% by 24 h. Compared with irradiated groups without VitE SME, cell proliferation decreased by 17.77% and 40.42% when the HaCaT KC was irradiated with 30 mJ/cm(2) and 90 mJ/cm(2) UVB irradiation, respectively. VitE SME has no toxicity to cell culture system and is characterized by stable release and penetration. Pre-incubation with VitE SME can partly reduce UV-induced cell damage, and the photoprotective efficiency to UVB irradiation also shows time dependence.