98 SUN CARE
ingredients, fungal chitosan contributes to prolonged and more consistent sun protection, meeting key performance expectations of modern consumers. The adhesive nature of chitosan is primarily
due to its cationic charge and its ability to form hydrogen bonds. When applied to the skin, the positively charged amino groups of chitosan interact with negatively charged components of the skin surface, creating electrostatic attractions. Additionally, the numerous hydroxyl groups
in chitosan’s structure can form hydrogen bonds with skin proteins and lipids, further enhancing adhesion. The water-resistant properties of chitosan
films are attributed to their ability to form a hydrophobic barrier on the skin surface. While chitosan itself is hydrophilic, the films it forms can exhibit hydrophobic characteristics due to the orientation of its polymer chains. When exposed to water, the hydrophobic
portions of the chitosan molecules align towards the surface, creating a water-repellent layer that helps maintain the integrity of the sunscreen formulation.
Emulsification and stabilisation The film-forming capabilities of fungal chitosan are complemented by its role as a natural emulsifier, making it a versatile ingredient in cosmetic formulations. Its unique chemical structure enables effective stabilization of oil-in-water emulsions, preventing separation during storage and supporting the even distribution of both organic and inorganic UV filters. This natural stabilizing effect can reduce or eliminate the need for synthetic emulsifiers, further advancing the goal of more sustainable formulations. Chitosan’s emulsifying properties stem from its amphiphilic nature. The hydrophilic amino groups along its backbone can interact with the water phase of an emulsion, while the more hydrophobic acetyl groups can associate with the oil phase. This dual affinity allows chitosan to position itself at the oil-water interface, reducing interfacial tension and stabilizing the emulsion droplets.1,2 The molecular weight of chitosan also plays
a role in its emulsification capabilities. Lower molecular weight chitosan, typical of fungal sources, can more easily arrange itself at the oil-water interface, providing better emulsion stability. Additionally, the flexibility of the chitosan
chains allows them to form a protective layer around emulsion droplets, preventing coalescence and maintaining the stability of the formulation over time.
Additional skin benefits Beyond these functional properties, fungal chitosan provides additional skin benefits that enhance its value in sun care applications. Its natural moisturizing effects help maintain skin hydration during sun exposure, while its inherent antimicrobial and anti-inflammatory properties offer additional protection. The antioxidant characteristics of chitosan also contribute to overall skin defence against
PERSONAL CARE October 2025 Chitosan solubility in 1% acetic acid 100 80 60 40 20 0 3 4 5
Figure 1: Solubility of fungal-derived chitosan environmental stressors.2,3,4
The intention is to
develop fungal chitosan for integration into sunscreen products to improve the sunscreen’s localization effect on the skin.
Moisturizing effects Chitosan’s ability to retain moisture is due to its hydrophilic nature and its capacity to form a breathable film on the skin. This film helps to reduce transepidermal water loss, keeping the skin hydrated. Moreover, chitosan can attract and bind water molecules, further enhancing its moisturizing properties.
Antimicrobial properties The antimicrobial activity of chitosan is well- documented and is attributed to its positive charge.1,2
6 pH 6.5 7 8
oxidative stress.4 This antioxidant activity can help protect
the skin from UV-induced oxidative damage, complementing the primary UV-filtering action of sunscreen ingredients. Maicelium suggests fungal chitosan as a highly active antioxidant that can repair damaged skin and increase anti- aging effects.
This cationic nature allows chitosan
to interact with negatively charged microbial cell membranes, disrupting their integrity and leading to cell death. In sun care formulations, this property can help protect the skin from potential microbial growth, especially in humid conditions or after water exposure.
Anti-inflammatory effects Chitosan has been shown to possess anti- inflammatory properties, which can be particularly beneficial in sun care applications. UV exposure can lead to skin inflammation, and chitosan’s ability to modulate inflammatory responses can help mitigate these effects. The mechanism involves the inhibition of pro- inflammatory cytokines and the promotion of anti-inflammatory mediators.2,4
Antioxidant activity The antioxidant properties of chitosan contribute to its skin-protective effects. Chitosan can scavenge free radicals and chelate metal ions, both of which are involved in
Synergy with beta-glucan Working in synergy with chitosan, fungal beta-glucan brings its own set of beneficial properties to sun care formulations. Its exceptional moisture-retention capabilities help prevent dehydration during sun exposure, while its biological activities support natural skin defence mechanisms. The unique molecular structure of fungal
beta-glucan, featuring (1→3) and (1→6) linkages, enables superior interaction with skin cells compared to plant-derived alternatives. This translates to enhanced protection against UV-induced inflammation and improved support for skin repair processes. Beta-glucans are polysaccharides composed
of D-glucose monomers linked by beta- glycosidic bonds. The specific structure of fungal beta-glucans, with their (1→3) and (1→6) linkages, allows them to interact with specific receptors on skin cells, particularly immune cells. This interaction can stimulate the skin’s natural defence mechanisms, potentially enhancing its ability to cope with UV-induced stress.6 The moisture-retention properties of
beta-glucans are due to their ability to form a protective film on the skin surface, similar to chitosan. This film helps to reduce water loss from the skin, maintaining hydration levels even in dry or sunny conditions. Additionally, beta- glucans can penetrate the upper layers of the skin, providing hydration from within.
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Solubility (%)
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