Multifunctional moisturisation

Moisturisation is one of the most widely used claims within the cosmetics industry and moisturisers are used in a variety of cosmetic formulations and applications, often supported by marketing claims¹.

Traditionally, moisturisers were thought to inhibit transepidermal water loss (TEWL) through occlusion. A brick-and-mortar model suggested that the stratum corneum (SC) was a dead layer functioning as an active membrane². Overtime, however, the SC has come to be viewed in a more holistic manner, with its architecture, composition, and function dictating  its biomechanics and determining  its overall role^3,4.

This growing understanding of the epidermal barrier’s complexity and its manifold interactions with deeper skin layers and the skin microbiome is fuelling demand for multifunctional product solutions with a well understood mode of action. This trend has been further nourished by Covid-19, with consumers now realising how technology facilitated all levels of society during this crisis. When it comes to selecting moisturising bioactives, formula-tors are therefore looking for proven, multifunctional active ingredients that can be used in various applications.

Proven biological efficacy

Saccharide isomerate is a 100% natural derived, biodegradable moisturiser which binds to the epsilon-amino group of lysine in the keratin of corneocytes, ensuring that it is not easily washed off until removed by desquamation. It supports stratum corneum (SC) hydration and water retention leading to improved moisturisation and desquamation in the mid to long term. Gene expression studies have also demonstrated that it effectively stimulates genes that play a key role in skin barrier improvement, thus strengthening the barrier function of the stratum corneum⁵.

Solubility

Formulators are looking for bioactives that are easy to formulate. Poor solubility can cause precipitation, re-crystallisation, or turbidity in transparent formulations. Such challenges can be overcome by adding the right solubiliser or solvent and/or changing the process. However, a bioactive that shows high solubility in oil or water can be added to an emulsion at any time, removing the need for such adaptations.

Consider the example of ethanolic-based applications, like hand sanitisers. These products must eliminate germs, but can be harsh on skin, leaving it feeling dry and itchy, so adding a moisturiser is recommended to reduce skin dryness. Saccharide isomerate is a clear aqueous solution, soluble in ethanol, making it suitable for transparent ethanolic based sanitisers.

When developing a hand sanitiser gel, amine bases are needed to neutralise the polymer, because it contains a high quantity of ethanol. Adding a primary amine is not recommended when using sugars, due to the risk of Maillard reactions. However, adding 1% saccharide isomerate has been shown to have no impact on a sanitiser’s colour stability while providingdeep moisturisation and longer lasting protection from dehydration⁶.

pH compatibility

In skin care, it is preferable to adjust the pH of formulations closer to the skin’s pH of around 5.5±1. However, some textures and bioactives come with specific pH recommendations for optimal stability and biological efficacy. Soap bars for example, require pH 10 which can be harsh for the skin and some bioactives.

At such an alkaline pH, important skin lipids for the acid mantle can no longer build up and play their role as alkaline neutralisers. The skin loses water, dries out and can no longer provide sufficient protection, making it sensitive to infection. Therefore, moisturisers are often added to soap bars, to limit residual skin dryness after repeated use. 

Saccharide isomerate can be formulated in the pH range of 3.0 to 10.0 and adding it to a soap bar has been shown to boost efficacy of the humectant glycerine, even at 0.20%. It immediately increases skin hydration for 24 hours, helping to reinforce the skin’s barrier while protecting aginst dryness, even with frequent use⁷.

Formulation texture and stability

Limiting the impact on a formulation’s texture and stability is a key challenge. With electrolyte sensitive systems for example, adding a high use level of a bioactive containing electrolytes may impact the formulation’s viscosity. Adapting the composition, or manufacturing process, is usually sufficient to reach the desired texture and stability.

Bioactives, particularly natural ingredients can also have an impact on a formulation’s scent and colour, and this may worsen over time, especially at higher temperatures or in daylight.

3% saccharide isomerate containing citric acid/sodium citrate as a buffer has been used in an acrylate crosspolymer based carrier and in this situation, suitable viscosity and good stability were achieved.

Compatibility

Some ingredients are sensitive to oxidation, heavy metals, specific chemical functions, or a specific pH. If two ingredients have incompatible pH recommendations, combining them increases the risk of respective instability. However, compatibility is not always so simple to assess. If we compare the same reactive function within two different chemical structures, compatibility may be greater if the function is less available due to steric hindrance limiting access to it, or if the function’s strength is weakened by the chemical structure.

Moreover, some interactions may occur within a formulation and impact the bioactive’s stability, without necessarily having a significant impact on the formulation. To ensure the stability and biological efficacy of different ingredients, compatibility should therefore be assessed case by case.

For illustration, consider niacinamide, a water-soluble, physiologically active form of vitamin B3 used in many moisturisers. This ingredient is popular in anti-ageing formulas and has a range of dermatological benefits, including boosting ceramide production, reducing hyperpigmentation, and anti-inflammatory properties². The compatibility in formulation between 3% saccharide isomerate and 5% vitamin B3 (niacinamide) has been shown to deliver a powerful hydrating effect to all facial areas, in the short- and long-term⁹. This is illustrated by the visualisation in figure 1. Some combinations of bioactives can also have synergistic effects, such as saccharide isomerate boosting the efficacy of glycerin in a soap bar, as previously mentioned.

Technical performance

As well as expecting good stability and proven active ingredients in a formulation, consumers expect good technical performance and pleasant sensory properties. The latter are especially important in sun care applications as they can influence a consumer’s willingness to use a product more often or in larger quantities. UV exposure is known to cause skin dryness, which is why the addition of moisturisers is highly recommended in sunscreen formulations. Thanks to its good compatibility, saccharide isomerate can be added for this purpose.

A well-chosen bioactive can also enhance other aspects of technical performance. In rinse-off applications for example, high volumes of dense foam create a better sensorial experience for consumers. Adding 0.2% saccharide isomerate to a soap bar has been shown to increase foam volume by 22% compared to a placebo formulation.

When it comes to make-up remover products, formulations need to combine good removal properties with minimal friction, so mois-turising actives are recommended. Take the example of micellar waters; the choice of bioactive in these aqueous transparent formulations is important to make sure the micelles are formed in the formulation and that when applied to the skin, they capture, and gently lift away dirt, and make-up.

Saccharide isomerate shows good compatibility in such products. In tests, at 1% it provided comparable make-up removal properties to commercially available formulations, as shown in figure 2.

Conclusion

In a fast-changing market, new trends and consumer needs arise constantly. In this landscape, meeting new expectations by adapting formulations, textures, and sensory properties can be a challenge and formulators may well look for new bioactives. Sometimes however, well-known, established ingredients can offer new potential. Saccharide isomerate has a 40-year track record for its moisturising properties, but by enhancing multifunctionality and technical performance in diverse applications it is more than just a moisturiser.

References

1 Lodén, M. The clinical benefit of moisturizers, JEADV (2005) 19, 672–688

2 Sethi, A. Kaur, T. Malhotra, S. K. Gambhir, M. L. Moisturizers: The slippery road. Indian J Dermatol 2016;61:279-87

3 Voegeli, R. Rawlings A.V. Household and Personal Care today, Vol. 8(4) July/August 2013

4 Rawlings, A.V. Recent advances in skin “barrier” research. J Pharm Pharmacol. 62(6):671-7 (2010).

5 Klock, Rosenberger, Saccharide isomerate to deeply hydrate skin and scalp C&T magazine, Vol 127, No. 9, p 636-643

6 Imfeld, Laurent, Rosenberger, Adamietz, Guillemard, Zhang, Moisturizing care and hygiene go hand in hand Personal Care Magazine, Jan. 2021

7 Rosenberger, Sfriso, Laurent, Adamietz, No more dryness after cleansing Personal Care Magazine July 2021

8 Mawazi, S.M. et al. A Review of Moisturizers; History, Preparation, Characterization and Applications, Cosmetics 2022, 9, 61

9 Voegeli R, Gierschendorf J, Summers B, Rawlings AV. 2019. Facial skin mapping: from single point bio-instrumental evaluation to continuous visualization of skin hydration, barrier function, skin surface pH, and sebum in different ethnic skin types. International Journal of Cosmetic Science 41, 411-424