One of the key challenges in formulating skincare products is to ensure that the active ingredient/s used in the formula serve their purpose on the skin. There are many considerations that need to be taken which are not limited to just the choice of active ingredient/s but their compatibility with the base formula and other excipients used as well.¹

Formulation roadblocks

It is important to note that the human skin has high complexity and it limits the penetration of substances into the body, as part of its purpose of protection.² The skin penetration of actives is affected by their molecular weight, hydrophobicity, and charge.³ In line with this, formulators need to ensure that the ingredients they use can reach the target site, without causing irritation at the same time. Sometimes, the strategy is to use a higher dose of the active ingredient to ensure that the amount that becomes bioavailable is sufficient to be effective. However, this is not practical to do so every time.²

Aside from this, many active substances have stability issues and formulators need to be extra cautious when working with them. For instance, Vitamin C is a well-known active ingredient in skincare. It serves as an antioxidant and is used to counter the symptoms of photoaging. However, working with this substance is quite difficult because of several reasons. Firstly, it is hydrophilic in nature, so it has difficulty penetrating the hydrophobic layers of the skin. In addition, the pH of the formulation must be taken into consideration because the active form of ascorbic acid is limited to a pH below 4.2. It is also easily oxidizable in aqueous solutions and emulsions, making it useless in the final product.⁴ Ideally, a skincare formulation must contain active ingredients that are stable within the proposed shelf life and at the same time serves its purpose in the skin.¹

Delivery system, in a nutshell

One of the formulation technologies used in cosmetics to protect and stabilize active ingredients is the use of delivery systems. Delivery systems are achieved through encapsulation techniques wherein they act as a vehicle for the active ingredients for these to remain stable until they successfully reach the target site.^5,6 This technology is being used in pharmaceutical products as well. There are various forms of delivery systems being used nowadays. These include liposomes, niosomes, microemulsions, nanoemulsions, micro and nanoparticles, polymeric micelles, and cyclodextrin complexes. ⁶ We will discuss some of them here.

Liposomes are the most widely known and used cosmetic delivery system. The vesicles of liposomes are composed of amphiphilic molecules which enables them to carry water-soluble active ingredients and penetrate the skin successfully. Image 2 shows the basic structure of a liposome. They are artificial phospholipid membranes that aid the passage of substances into the stratum corneum.⁶

Microemulsions are an emulsion type of delivery system that is composed of dispersions of oil and water stabilized by an interfacial film of surfactant molecules. One of the main differences between this to regular emulsion is the droplet size of <100 nm which makes it appear transparent or translucent. In microemulsions, the active ingredient is available for immediate absorption.⁶ The structure of microemulsions is similar to that of emulsions having lipophilic and hydrophilic phases with the surfactant in the interface.

Some available raw materials in the market

BASF has a Skin Delivery Portfolio aiming to provide formulators with easy-to-use actives. As an example, they have Cylasphere® Retinol which is an agar microsphere that encapsulates retinol. The mechanism of action of this active ingredient is through the reaction of the microsphere with skin enzymes leading to the gradual release of retinol. They claim better bioavailability, better efficacy, and more gentle use.⁷

Another company that offers a range of encapsulated active ingredients is Salvona Technologies, Inc. They offer a wide range of ingredients with varied applications. Some of these products such as the MultiSal® range offer a unique structure. It has sub-micron spheres that provide extra protection to the actives and enables controlled release of the active substance in the skin. What’s interesting is that they also offer custom-encapsulation services.⁸

Aside from these two companies, there are a lot of others offering similar products that formulators can choose from. Of course, the selection will be based on your formulation concept and goals. Some are applicable in the O/W or W/O emulsion format while some are for anhydrous formulas.

What’s in it for you?

Using delivery systems has several advantages for active ingredients:

1. Enhanced stability – make the formulation of hard-to-use actives easy
2. Increased efficacy – ensure that your final product works

It is interesting to note that the industry is continuously and quickly innovating so we need to watch out for new technologies from time to time.

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