FEATURE COSMETICS
Interference fringe profilometry calculates a phase image from an interference fringe image projection
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Saclay. Tfayli has been developing Raman methods for many years, for example using Raman spectroscopy for in vivo imaging, to study lipid ageing within the stratum corneum. He has also used Raman confocal microscopy to study skin ageing. Bio-EC has also worked with researchers
from the University of Reims Champagne- Ardenne, using Raman spectroscopy and micro-imaging to monitor how different molecular weights of hyaluronic acids penetrate the skin. Topical delivery of molecules into the skin is a huge issue for cosmetics manufacturers, and research has confirmed that, in this case, Raman spectroscopy is an effective method to assess this. ‘With Raman, we can also evaluate
hydration claims from product manufacturers – for the hydrating effect we can differentiate between two different forms of tyrosine [non-essential amino acid] and detect the more open form that is able to capture water,’ Radionov noted. ‘We can also analyse different natural moisturising factors, and the pools of protein and lipids. Raman is a very powerful technique but it is important to ask the right questions.’
Skin models But testing isn’t all about in vivo methods. Ex vivo testing is essential to evaluate raw materials and finished products. Cosmetic testing companies have developed skin models that hold all the cells and characteristics of real human skin, and are designed to mimic the live response of in vivo human skin. ‘Several labs have declared they can
16 Electro Optics July 2021
perform studies based on living skin explants, but from what I can see, we are probably the only lab in the world making a business around this,’ said Radionov. ‘We carry out almost 360 studies a year with our main model, and we know how to keep the skin in a viable state for up to two weeks – this is very important.’ Ex vivo skin models, typically based on explants of human skin donated by volunteers, act as an intermediate stage between cell culture and true in vivo analysis. To cater for different tests, various models exist, containing different layers of the skin. For example, whole skin explant
‘With Raman, we can also evaluate hydration claims from product manufacturers’
models include the epidermis, dermis and hypodermis layers, while other models may just include the hypodermis (adipose tissue). Crucially, these will be held in a culture medium to maintain the model’s viability. ‘We use a special culture medium, which
we believe is unique,’ Radionov noted. ‘This keeps explants in a viable state and guarantees that whatever the donor, we can ensure the skin remains responsive to any external treatment or product applications.’ Bio-EC performs much of its usual test
methods, including histology, transmission electron microscopy and Raman spectroscopy, on its skin models. As part of these tests, the models may be exposed to
atmospheric pollutants and ultraviolet light to induce oxidative stress, inflammation or DNA damage. In addition, the skin may also be subjected to infrared light, bacteria, even small wounds, so that healing processes can be monitored. However, as Radionov points out, the demand to assess the effects of blue light is rising. Some research has indicated that blue light, also known as high energy visible light and emitted from smartphones and other devices, can lead to hyperpigmentation and premature photoageing of the skin, and also disrupt circadian rhythms. ‘Blue light is very trendy right now... and cosmetic producers are beginning to think they can protect skin against blue light, as well as UVA and UVB light,’ he said. To test the effects of pollutants and light on skin models, Bio-EC has developed various exposure chambers. For example, in the project Urbaskin, the company worked with researchers from French universities, as well as the Bio-Europe, Genex and Uriage Dermatological Laboratories to develop Pollubox, a transparent chamber with nebuliser system that sprays clouds of gases that may contain heavy metals or hydrocarbons, onto the skin model. In a second project, custom-made chamber Solarbox has been built to expose skin models to different wavelengths of light and visible light. ‘This is a dark, non- transparent chamber with light emitters and filters so we can control the dose and density of the light,’ said Radionov. ‘Control is always important... we need to know which proteins are modulated by the stress and at what point in time.’ He added: ‘In another idea, we want to add more stress factors, such as pollution and UV light – this combination of different stresses allow us to get much closer to reality.’
Gtting closer to reality is what it’s all about. According to Radionov, research is now underway to also develop more sophisticated skin models that better mimic living skin. For example, skin model Perfex Vivo ‘reproduces’ blood flow via continually circulating culture medium throughout its layers. ‘This model is much closer to reality, and all our measured parameters correlate well with measurements from volunteers,’ said Radionov. In another project, Bio-EC researchers
are developing ‘nerve skin’, in which neural stem cells are added to the skin model, which then differentiate to neurons, so researchers can study reactions to stress and treatments. ‘This really is a very nice and beautiful concept,’ says Radionov. ‘And in each case, the idea is to create a skin model that is closer to the gold standard of clinical tests.’ EO
@electrooptics |
www.electrooptics.com
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