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By: Steve Herman
Posted: February 24, 2014, from the March 2014 issue of GCI Magazine.
“I believe that if you show people the problems and you show them the solutions, they will be moved to act.”
Let’s engage in a hypothetical for this article. The marketing department has identified the latest, greatest botanical active, and it simply must be in the new skin care line. And besides having it be the focus of the advertising campaign, this new botanical active must work as advertised. Also, the formulation must be fragrance free, paraben free and contain no formaldehyde donors. So off it goes to R&D, where the development work begins. Of course, there are a few things that can’t be avoided, and stability, safety, regulatory compliance and correct labeling top the list.
The first step may be to confirm the potential benefit of the active. Because this is a botanical—a berry extract from the foothills of Western Nepal, let’s say—the existing claims are likely to be folkloric or anecdotal. Thus, the regulatory department has requested some scientific data. Fortunately, recent progress in genomics has provided some quick screening tests using microarrays. Gene expression can be used to establish anti-aging actives, and biomarkers can screen formulations and identify optimum concentration levels. These new techniques can also identify the biological mechanisms of action, which can help support specific product claims.
The solubility of the active will have a profound influence on its likelihood for success. Most water-soluble materials do not penetrate the skin, so the best chance of a material being effective is for it to be oil soluble and not too big. A molecular weight under 500 is generally considered necessary for significant skin penetration. Of course, a natural extract, being a complex mixture, is harder to characterize than a specific chemical. Hopefully the actives in this new great berry fit into the range of ideal chemical parameters.
Now, there are lots of emulsion formulas already around the lab, so maybe they can just stir in 0.05% of the new ingredient into an existing base and ship it? Unfortunately, we really can’t avoid the issue of the product bases as delivery systems. There are two key considerations impacting the effectiveness of the formulation: the emulsifiers and the oil phase composition. As work conducted by the late Johann Wiechers (an expert, among other things, in skin penetration and delivery and contributor to GCI sister publication Cosmetics & Toiletries), the actives must be completely soluble in the oil phase but just at the edge of solubility so that, upon application, the actives can readily leave the oil phase and be free to penetrate the skin.1
The emulsifier also must not trap the active. A typical anionic or nonionic base may not optimize delivery. A liquid crystal emulsification system will break down upon application to the skin and be a good carrier for our hypothetical active.2 An emulsion based on steric hindrance, which breaks on contact with salt and can’t re-emulsify, is another good possibility. If the emulsion and the oil phase both release the active, we have a good chance for true efficacy.
Feel and Smell
We also want the product to feel elegant when applied to the skin. Conventional wisdom places most of the sensory effects on the emollient blend. But individual oils have different spreading and rub-in properties, so no one material provides an ideal feel. Three emollients with varied properties can be blended to give optimum performance. Newer work suggests the importance of the emulsifier is on the initial feel, say the first 20 minutes. So we need an emulsifier system that feels good and releases the active and an oil phase that does the same, and all should go well.
The product is stable and feels good, but it is thin. Assuming we have made an oil-in-water emulsion, thickening the external phase should do the trick. Carbomers and natural gums will boost the viscosity. But beware, rheology modifiers can affect the feel, so the choice must be made wisely.
Our newly developed system also must be well preserved. Parabens are out (certainly not because they don’t work, but because they are victims of the bad PR rampant on the Internet). Formaldehyde donors are also out. Phenoxyethanol becomes a good default preservative, perhaps combined with sorbic acid or potassium sorbate. Polylysine, alone or with phenoxyethanol, would be a creative option as well.
The base smells a little... well, not really bad, but slightly fatty. As per our previous constraints, we can’t use fragrance—but we can try to mask it. A common solution is a touch of ethylene brassylate, a musky note that won’t make the product smell “perfumey.” Of course, it is a fragrance ingredient, but if fragrance materials appear separately on the label under their INCI names, the word “perfume” does not show up, and the product is “fragrance free.”
One other option is using a small blend of essential oils that are essentially a simple fragrance compound, and this approach can actually provide ingredients that look good on the label. On the downside, they may contain a brew of EU allergens that would not be appealing.
Once the product is applied to the skin, a complex process begins, starting with the evaporation of the water in the formula. All the nonvolatile materials become more concentrated and phase changes involving the emulsifiers can occur. The dynamic composition of the base in the 10 or 15 minutes after application will determine the success of effectively releasing the active to the skin.
So, after stability, preservative and safety testing is completed, and accurate label information has been provided to the packaging department, the product’s development is almost done. Of course, proof of the final product’s effectiveness is still required for marketing—and dry science alone won’t suffice.