Abstract

Sunburn, pigmentation, hyperplasia, immunosuppression, and vitamin D synthesis represent acute responses of the skin to solar ultraviolet radiation, whereas photoaging and photocarcinogenesis constitute chronic effects. Sunscreens are known to protect against sunlight-induced erythema and sunburn. However, a number of studies demonstrated that UV-irradiated sunscreen components such as PABA and TiO 2 , when in contact with skin cells, cause biological damage ( e.g. , to DNA or enzymes) through facilitating generation of reactive oxygen species (ROS) in cells. Therefore, novel supramolecular sunscreens are under development based on zeolites (porous material) as hosts with sunscreen components as guests. Encapsulation should alleviate adverse side effects by preventing direct contact of the sunscreen guests with skin cells. Supramolecular sunscreens involving the use of supramolecular composites based on zeolite hosts may reduce or even eliminate biomolecular damage by sunscreen components such as titanium dioxide (TiO 2 ). The focus of this research is to examine the penetration, if any, of zeolite particles into cells (rat keratinocytes and human skin fibroblasts). Zeolites modified with fluorophores were used to obtain a distribution profile within cells using confocal microscopy. Fluorescent probes that can be taken up by viable cells were further used to examine the release of guests from the zeolite hosts. The protective effect of zeolites against the production of harmful ROS caused by UV-irradiation was examined by observing H 2 O 2 generation in cells using confocal microscopy. The results revealed that zeolites do not penetrate cells and they reduce the amount of ROS produced by UV-irradiation of cells. The data presented here will help in the design of supramolecular sunscreens.