Sunscreen Technology – Nanoparticles on Trial

It was nearly one year ago since I took on the guise of my alter-ego  ‘lab rat’ to participate in a human study on the potential of the zinc oxide found in sunscreens to penetrate the skin.  The trial interested me on a number of levels. I have heard many a scary story about our skin and chemicals including those from camp 70% absorption to camp ‘only 10% get’s through if you REALLY try’.  I must admit that logic would lead me to the conclusion that our largest organ who’s main job is to keep what’s out out and what’s in in ‘could do better’ if it does indeed let 70% of stuff through (maybe we should just rub chocolate on our arms and give our mouths a break) but being a cosmetic chemist it seems too much of a ‘convenient truth’ to just blindly sit myself in the 10% camp. 

In addition to the skin penetration stuff I was also interested in the neat method that was proposed to track zinc through REAL people in REAL life situations using a stable isotope. That’s genius. Oh, and  last of all I just had to learn more about these nanoparticles.

So what does one do in such a situation? Well one finds some smart scientists with a laboratory,  a solar measuring machine and some rather sensible ideas and then follow them around, asking to be experimented on. That is what I did!

Lapping up the sun

And now the preliminary results are published :  ICONN2010 Abstract Gulson[1].

The trial looked at two sunscreen formulations which were identical except one that formulation contained nanoparticles of zinc oxide and the other contained the good old fashioned white stuff – big and chunky (sunscreen grade) zinc oxide.   Nano sized zinc oxide and titanium dioxide have been used in sunscreen formulations for a number of years now as they give all of the coverage of traditional physical sunscreens without the whiteness and heavy skin feel. However questions have been raised as to the general safety of nanoparticles which is not surprising for such a new and fast-developing area of technology. The questions are based on observations showing that when you blast a chemical down to such a small size (nano) you sometimes change not only its physical but also its chemical properties.   While safety tests have been carried out on nano zinc and titanium in order to pass them as cosmetic ingredients no compelling information has been found to doubt their safety. You can read more about my life on trial here.

So it is with great enthusiasm that I wish to share with you some preliminary conclusions (these results still stand but further analysis is being carried out in order to get a deeper understanding of the readings).

 The trial showed there to be no statistically significant difference in dermal absorption for the volunteers in the nanoparticle and the non-nano group.  Both groups absorbed some of the zinc showing that some of the Zinc Oxide found in sunscreens does penetrate healthy skin to a degree – a mean increase of 0.4% was recorded.  Urine and blood samples taken 6 days after the end of the trial showed a slight increase in the levels of  ⁶⁸ Zinc  (the rare isotope tracer) which is probably due to the way the zinc had been metabolised.

So what does that mean?

The most important conclusion that we can draw from this study is that the method of using a rare, stable isotope for tracking the fate of zinc oxide through the human body is scientifically sound.  That may not seem a very sexy conclusion but believe me, that is groundbreaking!

We can say much about the fact that the study only ran for a short time, only contained 20 people, wasn’t completely blinded and so on and that would all be right. However, the study did show that the method worked. We can apply a sunscreen onto the skin and quantitatively measure the passage of the key active through the body.  This trial wasn’t cheap and it wasn’t easy to carry out. The testing protocol was uncomfortable, time-consuming and costly.  Analysing the results has proven to be complex and we still don’t know if the Zinc present was particulate or soluble. 

Yes, this is real science and more often than not, real science created some really interesting questions. Sometimes you end up with more questions than answers.

So what’s next?

 
Well, there are a number of key questions that need answering and to do that we need to keep the research pedal to the metal. That will take time, money and vision.

Of key importance are the questions surrounding the passage of zinc through the skin and subsequently though the rest of our body.  We know that some zinc get’s through but we don’t know if that is physiologically significant and THAT is important.  After all, don’t many of us choose to ingest Zinc in the form of supplements every day?   Before we can jump to sensational conclusions and dire predictions we need to collect more evidence and be sure of our perspective.

There is no doubt that the fact that this study poses more questions than it offers up answers will irritate and sit uncomfortably with some people but all I can see is opportunity. Not the opportunity for making a quick buck, quite the opposite. The opportunity to engage the global cosmetics industry, the best academic minds and the brightest human guinea pigs to take skincare to a brave new level.   The only thing missing is the dollars – anyone got a few to spare?

Amanda Foxon-Hill

Response to the ICONN abstract published by Professor Brian Gulson et al in conversation with Gavin Greenoak.

Thanks  to Brian Gulson for his time in discussing these preliminary  findings.

Brian is presenting his findings at the International Conference on Nanoscience and Nanotechnology in Sydney later today.