Uniform Composite Nanoparticles for the Protection of Ultraviolet Sensitive Molecules

The damaging effects of the ultraviolet (UV) rays in sunlight have recently been a popular topic in the media. While most of the current focus is the effect of UV light on the skin, many other materials are negatively affected as well, such as medications, plastics and paints. In particular, biomolecules and natural pigments such as beta-carotene are known to exhibit sensitivity to photo-oxidation.

In this work, uniform nanoparticles made with a polymer [poly(methyl methacrylate)] and containing both a UV sensitive (beta-carotene) and UV absorbing (oxybenzone, octyl-4-methoxycinnamate, avobenzone) material are studied, where the type and concentration of UV absorber are varied. These particles are synthesized using the solvent evaporation method and then are exposed to UV light for predetermined amounts of time. The maximum beta-carotene absorbance peak was found using an ultraviolet visible spectrophotometer (UV/Vis), and normalized using particles that were not exposed to UV light (0 minutes exposure). Beta-carotene degrades over time when exposed to UV light, and the concentration sensitive UV/Vis allows quantification of how much beta-carotene remains unaffected.

Decay profiles of beta-carotene showed that all absorbers provided some UV protection at each concentration level compared to plain polymer and beta-carotene particles. However, avobenzone provided the most protection (smallest slope of beta-carotene decay curve) at the highest two concentrations. These results indicate that the uniform particles show potential for UV light protection, and may provide a template for multiscale particle studies.