Enhanced cosmeceutical delivery systems analysed

Cosmeceutical agents need to penetrate the stratum corneum to be effective, so what are the methods used to enhance delivery of key actives, how do they work and what impact is this having on the cosmeceutical industry? This article will take a closer look at the enhanced delivery mechanisms used in cosmeceutical products today: solvent delivery, liposomes, micro- and nanoemulsions, and micro- and nanoencapsulation. It will also consider the safety aspects of enhanced delivery systems, nanoparticles and future trends affecting the industry.

Solvent delivery

Since the skin is largely hydrophobic, water will tend to bead or sit on the surface of the skin with little penetration. This is due to its Polarity Index (PI), and is why it can be very difficult to get effective penetration of water soluble substances into the skin and across cell membranes. Solvent delivery is ideal for water soluble substances that would otherwise be unable to penetrate the external barrier of the skin; and works through one of two key mechanisms: reducing the PI of the skin or utilising osmolytic pathways. The PI of the skin is normally zero, however substances such as dimethyl isosorbide effectively permeate the upper layers of the skin without disrupting the stratum corneum to raise the PI of the skin and make it more compatible with water soluble actives. It effectively increases the penetration of water soluble substances by reducing the PI difference between skin and substance, while also reducing the water solubility of water soluble actives to effectively “force” the active out of the product into the skin on application. Using 5% – 10% dimethyl isosorbide in formulations can as much as double the penetration effectiveness of small water soluble substances into deeper layers of the epidermis that would otherwise struggle to get past the stratum corneum. While dimethyl isosorbide was traditionally used in pharmaceutical products, it is now increasingly being used in the cosmetics industry to enhance delivery of all types of water soluble actives and tanning agents, for faster, and more effective, results. Osmolytes are an ideal delivery system, since they do not interfere with cellular mechanisms or upset the osmotic balance within the cell. Osmolytes can travel as far as the stratum granulosum by following the concentration gradient of water (osmosis). This delivery enables passage of water soluble substances by effectively being “carried” with the osmolyte to deeper layers of the skin. Not only does this enable delivery of actives, but the osmolyte also influences deeper moisturisation, supports the water balance of the skin, and protects against irritation. Betaine (trimethylglycine), an effective and extremely gentle osmolyte, is also known to increase fibroblast growth and collagen production. Other osmolytes include butylene, propylene and pentylene glycol, and some amino acids and their derivatives. Osmolytes are increasingly being used to deliver water soluble actives and tanning agents to deeper layers of the skin.