Synthesis and Characterization of a nano‐bead sunscreen & testing its efficacy

Prolonged exposure to sunlight is one of the major causes of skin cancer due to mutations in the DNA. Repetitive or severe ultraviolet induced DNA damage increases the risk of skin cancer and rate of aging for human skin. Sunscreens are used to protect skin from harmful UV radiations and decrease the risk of skin cancers. There are several advantages of using nanobead sunscreens which include retention of effective UV light-absorbing capacity and scattering visible light, rendering them transparent on the skin. In addition, their increased stability reduces reapplication. They are also considered less irritating to skin. A cinnamate sunscreen was synthesized through a functional group transformation of cinnamic acid to cinnamate, an ester. After this, the sunscreen was synthesized into a nano-bead form using flash nanoprecipitation (FNP) technique. Cinnamate sunscreen and sunscreen incorporated nano-bead product were characterized using UV-visible spectroscopy scanning in the range of 250-400 nm. A single peak at 310 nm was observed confirming the high quality of the cinnamate sunscreen. The efficacy of the sunscreen and sunscreen nano-beads for their ability to chemically block ultraviolet radiation for skin protection was quantified using a customized chamber equipped with a UVB light source that emitted 310 nm light. To simulate human skin conditions, the UVB chamber was equipped with a temperature-controlled heat retention box that was constantly monitored and maintained between 33 - 37.5 °C throughout the investigation. A thin, even layer of a sunscreen was applied between two thin clear plastic wraps and exposed to the UVB rays. The ability to block UVB radiation was quantified through comparison between the intensity (in mW/m2 ) of the UVB light going through the plastic wrap before and after the sunscreen applied. It was observed that the sunscreen synthesized had the ability to absorb about 60% of the UVB radiation. Time related decay of the sunscreen after exposure to UVB was investigated. Preliminary results of time decay experiments suggest a possible UV induced hydrolysis of the sunscreen ester product. The results also indicate that sunscreen nano-beads possibly aggregate to super micellar complexes after exposure to UVB radiation after 3 hours leading to decreased efficacy. Future work includes further investigation of observations in-depth to improve the nano-bead sunscreen.