International researchers have spent the past 30 years attempting to reproduce human skin for the testing of cosmetics and pharmaceutical products. Now, after five years of development, University of Sydney scientists have produced their synthetic skin, MimSkin.
BLANCH : Now Gavin, you've made a synthetic human skin, something others have been trying to do for 30 years, so how did you beat them to it?
GREENOAK : Well Desley, as you say, a number of people have been trying to achieve this and it's not a straightforward process, because what we really wanted to do was not only produce a surface like human skin, but most importantly, it's got to be durable and, what you need is to be able to test with it in a way that we get reproducible results. In other words, we can test the same product a number of times and get the same results. Now there are other, at least one other material out there which does mimic to some extent human skin and this is used by the industry, but what we wanted to do most particularly was produce something that was durable and reusable. There are two main objectives in producing this imitation skin and the first one which we have achieved is in measuring the long wavelength ultraviolet light from sunlight which is of some concern to many people when they use high SPF sunscreens. And the next step and the more challenging step, which we are approaching, is actually measuring the sun protection factor or the SPF and that is in progress at the moment.
BLANCH : Well, MimSkin's described as a geometrical model of skin on a quartz disc that can be used to test a sunscreen's ability to absorb UVA rays, so why quartz?
GREENOAK : What we need most importantly is a substrate, a material that will transmit the ultraviolet light from sunlight. We need something, in other words, that will let through the lower wavelengths, which are the burning energy of the sun. Many materials which look transparent like window glass, Perspex - these do not allow the low wavelengths that just come through the ozone layer through to any measurement device, so quartz was selected because it is perfectly transparent in that regard.
BLANCH : And what's the skin made of?
GREENOAK : Well, the quartz plate is in fact etched in a secret way to mimic the surface topography of human skin. So what we did was we test normally and the tests we do are incorporated into Australian law and that means that any manufacturer who wants to market a sunscreen in Australia, they have to comply with this testing on human subjects. And we took subjects that we have tested, we know that their responses to sunlight are normal and we've tested sunscreens on them and we took casts of their skin and we used the back skin, we took casts of those skins and then we measured the skin surface and took and extracted from that a 3D image which we were able to apply, then, to the quartz glass plate.
BLANCH : So you've got everybody virtually with the same skin because everyone's skin is different...
GREENOAK : Very different.
BLANCH : And trying to deal with the variations would be extremely difficult, was that one of your biggest challenges, I could imagine it could be?
GREENOAK : It was very interesting to see the variation of skin surface characteristics. Most of the people we use are relatively young, usually less than 30 and we did see a huge variation in the topography of the skin. When you look at the skin under the microscope it's like looking at the alps. It's quite a bumpy landscape and we were quite surprised to see the variation and it was really a question of, well, can we accommodate this variation and, at that point and why one reason the project has taken so long is that we need to test it very, very thoroughly to make sure that the average topography that we derived from those casts was adequate. And we found that it was.
BLANCH : I suppose we should talk about how sunscreens work, shouldn't we?
GREENOAK : We should because there is a great deal of confusion out there about how they work. Sunscreens fundamentally and this is the crucial thing to remember is, that they are filters, so that they are letting sun ultraviolet light through from the moment you apply them. So when you take a sunscreen which has an SPF of 30+ and that may mean anything from 31 to over 60, then what this means is that when you apply that sunscreen, only one sixtieth or one thirtieth, depending upon the actually SPF number, is actually coming through to your skin. But the really important fact about that fraction, one thirtieth, is that it's one thirtieth being allowed through continuously so that you're getting an accumulating dose so that it's rather like a bucket filling up with water and the higher the SPF, the slower your bucket will fill, but once it's full and you've got your sunburning dose, the only thing to do then is to get out of the sun. Many people do seem to treat sunscreens a bit like batteries and you can apply them and it's unfortunate that we use the term "sunblock"- sunscreens do not block the UV, they filter it and the degree of filtering is a function of that sun protection factor.
BLANCH : Well, how will MimSkin be used by pharmaceutical companies?
GREENOAK : Sunscreens, today, are fairly sophisticated technologies and a huge amount of development goes into their development and it's important at many different stages of that development, to understand whether they are performing as expected. If there are novel approaches then they need to be assessed and, if one only had human testing available then this is both a lengthy and costly exercise. And to be able to have what we call an in-vitro method, a method in the laboratory, which is relatively simple to achieve and quickly performed, then this is certainly an advance in assessing whether a product is performing as expected.
BLANCH : So how much money would you expect them to save by using this method?
GREENOAK : Well, potentially we would expect them to use this in-house, so, given that a test on a human subject costs over $200 per subject and this test, which in fact comprises four tests in one, will only cost $250 and that test gives a full profile and characterisation of the product, we would expect a considerable saving.
BLANCH : Is this now commercially available, I mean you've made Australia the only country in the world with a method of evaluating the broad spectrum capability of sunscreens, so where is the project?
GREENOAK : We are producing these now. The quartz glass plate is out there and available for people to purchase, but we're at the same time, working on different substrates, flexible substrates so we're continually improving on this first iteration of MimSkin.
Mr. Gavin Greenoak
Australian Photobiology Testing Facility, Suite 204/205, Ross Street Building A03, University of Sydney, NSW 2006