Penetration of actives through the skin
Jun 08, 2016
Question for the day
"This is a bit of a broad request...but I'd love to hear your beliefs and thoughts on how we can penetrate active ingredients into and through the bilayers of the epidermis with product only. No tricks. It seems that there is some manipulation of the lipids of the bilayers required. Or do you see the science of cellular communication as the means by which many of these actives work?"
The main barrier to skin penetration is the stratum corneum. There are 3 ways of getting ingredients to penetrate:
1. intercellular
2. transcellular
3. appendageal.
The appendageal route is ideal for permeation of slow diffusing compounds and high molecular weight substances such as nanoparticles. Additionally it can help with the rapid diffusion of compounds before the homeostasis of the skin barrier is achieved. The intercellular pathway is the pathway between the keratinocytes. When the proteolytic enzymes dissolve the corneodesmosomes, the degradation of corneodesmosomes leaves ‘gaps’ or ‘lacunae’ within the multiple lamellar barrier structures, which play an important role in transdermal permeation. This is the second way ingredients can penetrate. The third way is transcellular through the lipid bilayer. To achieve this you need to use penetration enhancers. There are various classes of penetration enhancers. Short chain alcohols,Long chain alcohols, Esters, Amides, Surfactants and Turpenes are some of the them.
The most common ones we would be aware of are alcohol and propylene glycol. Linoleic acid can also be used as a penetration enhancer. My favourite by far is turpenes. Turpenes are found in Aromatherapy oils and also plant extracts. They exhibit excellent permeation-enhancing effects to facilitate transdermal delivery. Terpenes can enhance the permeation of both lipophilic compounds and hydrophilic ones as well. However also consider that the ideal skin penetration enhancer should be pharmacologically inert, non-toxic, non-irritating, non-allergenic and ideally should have a reversible action on the skin.
Linoleic acid is also a penetration enhancer. Jojoba oil also acts as a penetration enhancer. They have found the optimal percentage is 10% for maximum drug penetration. With regards to TEWL it doesn't prevent TEWL. There are other oils that work better with regards to that. It is however anti-inflammatory. Most oils only penetrate into the first layer of epidermis. I would not in a formula just use jojoba oil. I would mix it with out oils and actives that assist in creating a breathable barrier and help minimise TEWL.
Most plant extracts are also extracted with glycerine or alcohol. Both of which are solvents and penetration enhancers. My preference is for the ones with glycerine which also has a synergistic effect on repairing the skin barrier as well as penetrating it.
Another way of penetration is through the use of electrical modalities as well. Of course if you want to be tricky you can also use iontophoresis or sonophoresis :) Love both of them. Ultrasound creates a cavitation process called sonophoresis that permits both polarized and non-polarized ingredients to be diffused into the skin. Penetration occurs by disrupting the lipid-bilayer of the stratum corneum through a process of creating micro channels. Conversely, iontophoresis requires water-soluble, polarizable ingredients whereby charged ingredient molecules are able to transport and penetrate into the skin via a direct current and process of ionization.
About the Author
Jacine Greenwood is an internationally recognised educator who is known within the industry for her up to date knowledge and her ability to deliver training in an easy to understand method.
Jacine holds 6 Diplomas and a Bachelor of Nursing and her knowledge is well respected by her peers. With over 19 years experience in the industry and a background of cosmetic formulation, Jacine has an immense knowledge of current trends in research and new developments in the industry.
Jacine has been continually educating herself in all aspects of skin function and cosmetic chemistry for the past 21 years. Jacine’s knowledge is current and has a vast knowledge of the active ingredients that are being released onto the market.
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