The particles come from the aerial roots of the plant and can absorb and scatter light in the UV spectrum, lead researcher Mingjun Zhang at the University of Tennessee Knoxville, US, claimed.
However, unlike the nanoparticles of titanium dioxide and zinc oxide that currently form the basis of many sunscreen products, ivy nanoparticles do not absorb and scatter light in the visible spectrum, meaning they remain almost invisible when applied to the skin.
In addition, Zhang claims that the ivy nanoparticles have a more attractive safety profile that the metal-oxide nanoparticles.
While he concedes that the majority of studies exploring the toxicity of nano titanium dioxide and nano zinc oxide suggest the particles do not penetrate the stratum corneum, Zhang says there are still safety concerns with the metal-based particles.
The majority of the studies have been performed on healthy volunteers and not on broken or damaged skin, as well as only looking at nanoparticles greater than 20nm in size, so investigating alternative filters is crucial, the researchers claim.
Scatters and absorbs UV not visible light
Using a spectrophotometer the team measured the optical extinction spectra and observed that the ivy nanoparticles had significant extinction in the UV region when at a concentration of 4.92 microns/ml.
According to the study, the extinction of the ivy nanoparticles at this concentration was significantly better than the titanium dioxide between 280nm and 400nm wavelengths. Approaching the visible spectrum, the extinction rapidly drops off for the ivy nanoparticles, leading to the invisible nature of the particle.
In addition, the team investigated the degradability of the ivy nanoparticles as well as their potential to cross the skin barrier and their cytotoxicity.
The cytotoxicity was investigated by incubating HeLa cells with 1 micron per millilitre of ivy nanoparticles. According to the team, after 24 hours there was no toxicity seen with the ivy nanoparticles; however, with the same concentration of titanium dioxide nanoparticles, signficant toxicity to HeLa cells was seen.
Degradable by common proteinase
In the event that the nanoparticles do manage to cross the skin barrier, which the researchers deem to be unlikely after looking at computer models, the team wanted to investigate for how long the particles would remain both in the body and in the environment.
Temperatures between 4 and 37 degrees celsuis did not degrade the nanoparticles, nor did the cell culture medium RPMI; however, the enzyme proteinase did, according to the researchers.
After 30 minutes of incubation with the enzyme, the ivy nanoparticles were no longer visible with AFM (atomic force microscopy), which the researchers said further improves its safety profile.
“This enzymatic digestion by a common proteinase could further reduce the risk to the environmental and human tissues and organs,” they said.
Although further research needs to be done, the researchers claim that the naturally occurring nanoparticles have significant potential as a UV filter.
Source: Journal of NanoBiotechnology
Naturally occurring nanoparticles from English ivy: an alternative to metal-based nanoparticles for UV protection
Lijin Xia, Scott C Lenaghan, Mingjun Zhang, Zhili Zhang, Quanshui Li