OCTOBER 2014 PRACTICAL DERMATOLOGY 49

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Human skin is a complex structure and the largest organ of the body. It is designed to regulate body temperature, expel toxins from the body, and also limit penetration into the body. This poses

a particular challenge for chemists working to formulate efficacious topically applied products—cosmetic or phar-maceutical. A formulation must not only keep the active ingredients stable within the formulation, it must also contain appropriate components that will deliver the par-ticular key ingredients into the skin. Without a system in place to assist ingredients in reaching the desired location within the skin in order to exert their benefits, a product will not be able to provide the desired outcomes.

There are myriad active ingredients available today for the treatment of the skin. In this article, we use the term “active” in regard to the essential or key ingredients within a formula-tion, not in reference to regulatory designation. Regardless of an ingredient’s proven efficacy, its ability to remain stable and to also reach the desired location within the skin is para-mount to actually achieving the desired effects.

Formulating topicals that deliver on an ingredient’s promises requires many important details be taken into consideration. One of the most important is the use of an appropriate delivery system or vehicle to assist the ingredi-ent in its penetration through the skin. This facet of the cosmeceuticals industry has been expanding in recent years with many novel delivery systems now available to the chemist. We will explore several new offerings, and how they support and improve the efficacy of new and time-tested topical ingredients in cosmeceuticals.

PENETRATING THE SKINThere are multiple types of delivery vehicles that have

been used for decades in the skin health industry. Several novel options of particular interest are silicone elastomers, polymer microspheres, and next generation, non-phos-pholipid liposomes. Each system will be reviewed and its benefits discussed.

SILICONE ELASTOMERSIt wasn’t until the early 1990s that any soft-solid sili-

Novel Delivery Systems in

Cosmeceuticals A review of new offerings and insights into how they support and improve the efficacy

of new and time-tested topical ingredients in cosmeceuticals.

BY JENNIFER LINDER, MD

Considering the sheer number of options one has in topi-cal product choice, creating or selecting products that will provide patients with excellent visible results is para-mount. If a product is well-formulated, properly preserved and designed for the targeted delivery of actives to the desired location within the skin, then it will deliver on its promises.

PRACTICAL POINTER

“Regardless of an ingredient’s proven efficacy, its ability to remain

stable and to also reach the desired location within the skin

is paramount to actually achieving the desired effects.”

50 PRACTICAL DERMATOLOGY OCTOBER 2014

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cones were used in cosmetic formulations; essentially all silicones were liquids.1 These newer soft-solid silicones can be made in a variety of textures, making them ideal for delivering a wider range of actives. Polysilicone-11 and dimethicone are particularly good choice for these systems. They not only wrap and protect volatile actives, but also impart a cosmetically elegant texture to a finished product.2

By using these silicone elastomers in an anhydrous product base to deliver water-soluble actives, such as L-ascorbic acid, into the skin, the molecules stay intact until they interact with the skin. This elastomer acts as a “dermal patch” that delivers the L-ascorbic acid to the sweat pores where they interact with water to become active within the skin. This is referred to as transappend-geal delivery, or the delivery of an active through openings in the skin like sweat glands, sebaceaous glands, or hair follicles rather than through the spaces between kerati-nocytes.3 The molecules are released transdermally over a long period of time, providing full saturation and long-lasting interaction with the skin. This is of great impor-tance to the formulation of effective L-ascorbic acid topi-cals specifically, as this molecule is notoriously unstable in formulation.4

POLYMER MICROSPHERESSome beneficial actives for the skin have the unwanted

side effect of causing surface irritation. There are some delivery vehicles that not only increase the stability of the ingredient within the formulation, but also reduce the potential for surface irritation due to application. One such ingredient is retinol; although less irritating than pure

retinoic acid, if properly preserved and delivered, pure retinol can deliver similar results to pure retinoic acid with far less irritation.5

A matrix primarily comprised of allyl methacrylates crosspolymer has shown the ability to not only stabilize retinol and minimize surface irritation, but also to provide microspheres that create a reservoir for retinol, allowing it to be released slowly over time. This slower release from the microspheres, due to both diffusion and the friction caused by rubbing during application, helps increase the overall efficacy of the retinol formulation.6

NEXT GENERATION, NON-PHOSPHOLIPID LIPOSOMES

Traditionally, all liposomes used to enscapsulate actives were formed using phospholipids that have a hydrophilic “head” and a hydrophobic “tail” (See Figure 1). Similar to the structure of a cell membrane, these phospholipids arrange themselves tail-to-tail to create a bilayer. Within this structure any number of hydrophilic or hydrophobic actives can be encapsulated. Once formed, traditional liposomes do require specific conditions in order to

WATCH NOW

Dr. Linder spoke with Practical Dermatology® magazine about advancements in cosmeceuticals and skin care. Watch the interview now on DermTube.com: http://dermtube.com/video/incorporating-skincare-into-practice--ipisenol/

Or visit the Skincare and Photoaging DermTopic center on PracticalDermatology.com.

52 PRACTICAL DERMATOLOGY OCTOBER 2014

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remain stable, including pH. They are also not stable in the presence of surfactants.7

There are new, patented lipids that are being utilized to create liposomes with far greater stability. Primarily comprised of PEG 12 glyceryl dimyristate, these lipo-somes form spontaneously once water is introduced rather than having to employ traditional agitation or other methods of liposome formation.8 They can deliver any number of hydrophilic and hydrophobic actives within the same sphere, simply in different layers of the liposome. These new liposomes increase penetration of actives and reduce topical irritancy, producing excellent outcomes (See Figure 2).

DELIVERING RESULTSConsidering the sheer number of options one has in

topical product choice, creating or selecting products that will provide patients with excellent visible results is para-mount. If a product is well-formulated, properly preserved and designed for the targeted delivery of actives to the desired location within the skin, then it will deliver on its promises.

Whether choosing new ingredients or time-tested actives, these novel delivery systems are taking cosmeceu-ticals to the next level. n

Jennifer Linder, MD is a dermatologist and Mohs micrographic skin surgeon, serving as Chief Scientific Officer for skin care and chemical peel company PCA SKIN, and running a private practice out of Scottsdale, AZ. She holds a clini-cal faculty position in the Department of Dermatology at the University of California San Francisco. Dr. Linder is a

spokesperson for The Skin Cancer Foundation and sits on the Editorial Board of the Cosmetics Journal. She has been fre-quently interviewed by the press and published in trade pub-lications, journals and textbooks, most recently “A Practical Guide to Chemical Peels, Microdermabrasion & Topical Products” by Rebecca Small, Dalano Hoang and Jennifer Linder; and the chapter “Cosmeceutical Treatment of the Aging Face” in “Aesthetic Medicine: Art and Techniques,” edited by Peter M. Prendergast and Melvin A. Shiffman.

1. Rosen, M. Delivery System Handbook for Personal Care and Cosmetic Products: Technology, Application and Formula-tions 2005.2. Grant Industries Technical Data Sheet Gransil OHS5AA20, Elmwood Park, NJ, US.3. Ronert, M. How Delivery Systems Change Skin Care Effectiveness. Skin Inc June 2014.4. Heber, G.K.; Markovic, B.; Hayes, A. An immunohistological study of anhydrous topical ascorbic acid compositions on ex vivo human skin. Journal of Cosmetic Dermatology 2006, 5, 150–156.5. Kang, S.; Duell, E.A.; Fisher, G.J.; Datta, S.C.; Wang, Z.Q.; et al. Application of retinol to human skin in vivo induces epidermal hyperplasia and cellular retinoid binding proteins characteristic of retinoic acid but without measurable retinoic acid levels or irritation. Journal of Investigative Dermatology 1995, 105, 549-556.6. Technical Data Sheet, PP 120 RE, HBS, Hoffman Estates, IL, US.7. Nomura, F.; Nagata, M.; Inaba, T.; Hiramatsu, H.; Hotani, H.; et al. Capabilities of liposomes for topological transforma-tion, Proceedings of the National Academy of Sciences of the United States of America 2001, 98(5), 2340-2345.8. Technical Data Sheet, QuSome, BZL, Pittsburgh, CA, US.

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Figure 1. Tradtionally, all liposomes used to enscapsulate

actives were formed using phospholipids that have a hydro-

philic “head” and a hydrophobic “tail” that arrange themselves

tail-to-tail to create a bilayer.

Figure 2. New, patented lipids for liposomes form spontaneously

once water is introduced. Any number of hydrophilic and hydro-

phobic actives can be delivered within the same sphere.