English ivy nanoparticles could be used for future sunscreens
Researchers at the University of Tennessee reported that English ivy nanoparticles may protect skin from UV radiation better than other metal-based nanoparticles such as titanium dioxide (TiO2). The team was led by Mingjun Zhang, an associate professor of biomedical engineering at the University of Tennessee, who previously discovered that English ivy owes its amazing clinging power to the nanoparticles it secretes.
The team isolated nanoparticles from Hedera helix (English ivy) and evaluated them for potential use in sunscreens based on their ability to absorb and scatter UV light, safety toward mammalian cells, biodegradability and potential for diffusion through skin. Their work, published in the Journal of Nanobiotechnology, responds to research claiming that metal-based nanoparticles could be linked to environmental and animal toxicity.
To test the ability of the nanoparticles to protect skin from UV radiation, a UV and visible wavelength spectrophotometer was used to measure the optical extinction spectra of the nanoparticles. The nanoparticles exhibited significant extinction in the UV region, while having little extinction at the visible and near infrared regions. This indicated that the ivy nanoparticles could effectively block UV radiation without the opacity observed in other metal-based nanoparticles.
Comparing the UV blockage with TiO2 nanoparticles at the same concentration indicated that the total extinction of the ivy nanoparticles from 280 nm to 400 nm was better than the TiO2 nanoparticles. In addition, extinction of the ivy nanoparticles decreased sharply after the UV region, which makes ivy nanoparticles more effective in the UVA/UVB region and gives them high transmittance in the visible region, making them virtually “invisible”.
To assess the toxicity of the nanoparticles, the team incubated ivy nanoparticles with HeLa cells for 24 hours. By using propidium iodide staining, researchers examined the cells upon incubation with the ivy nanoparticles by flow cytometry (a technique for counting and examining microscopic particles), noting no toxicity in comparison with the control cells.
Another research claims that metal-based nanoparticles could be linked to environmental and animal toxicity, and that TiO2, maghemite and iron nanoparticles (which have less than 15 nm in diameter) are capable of penetrating the stratum corneum, potentially leading to increased aging, pathological effects in the liver, and particle accumulation in the brain. On the other hand, ivy nanoparticles have a diameter of 65.3 ± 8.04 nm (based on measurements of 30 randomly counted nanoparticles that were not dominated by other particles). Since the particles are larger than metal-based sunscreens, they have less potential to penetrate through human skin.
In addition to demonstrating that the ivy nanoparticles can be used as a UV filter in sunscreens, the researchers also emphasized that these nanoparticles demonstrated an adhesive effect, which reportedly enhances the UV protective ability of the nanoparticles. The properties of the nanoparticles in the secretion enable the vine leaves to hold almost 2 million more times than its weight. It also has the ability to soak up and disperse light, which is integral to sunscreens.
Since question and debate remains over the safety of metallic nanoparticles in sunscreens, interesting alternatives such as these pose new opportunities for formulators in this highly debated field. Ivy nanaoparticles could be used in other applications such as military technologies, medical adhesives and drug delivery.