(571t) Eco-Friendly Dual-Shell Fungal Chitosan-Silica Microcapsules with Enhanced Mechanical and Barrier Properties for Potential Consumer Applications

Nowadays, heightened self-awareness has swept across the world, resulting in a surging demand for wellbeing, personal care, and cosmeceutical products that positively impact consumers’ self-esteem [1]. To this end, a plethora of clean beauty products (CBP) has emerged, with particular emphasis on leave-on/rinse-off formulations enriched with microparticles for skin exfoliation and fragrance delivery properties [2]. Indeed, many CBP have incorporated synthetic microparticles intentionally to maximise the benefits on consumers’ skin for a smoother texture, scented touch, and defence against wrinkles and blemishes. Although highly effective, these CBP microparticles, which may fall under the category of microplastics, have posed a severe threat to the ecosystems when rinsed off into wastewater [3]. Following the proactive stance by the European Union (EU) towards banning microplastics from cosmetic products in favour of greener materials, the search for high-performance cosmetic alternatives for skin scrubbing and fragrance delivery is still ongoing.

In this study, we propose a facile method to fabricate fungal chitosan-silica microcapsules with a core of floral scented hexyl salicylate (HS) as a model cosmetic oil. Specifically, emulsified HS droplets were stabilised electrostatically and sterically using sodium dodecyl sulphate (SDS) and SiO₂ nanoparticles (NPs) with their surface modified by É›-polylysine, respectively. Fungal chitosan was used to form an organic coating (primary shell) around the oil droplets at pH 2, which was then reinforced by a secondary inorganic coating of SiO₂ via external alkaline (pH 11) mineralisation of sodium silicate. The microcapsules were assayed for their morphological, barrier, and mechanical properties by bright field optical/fluorescence microscopy, scanning electron microscopy, UV-Vis spectrophotometry, and a micromanipulation technique, respectively.

The findings showed that single-shell fungal chitosan microcapsules were spherical with a core-shell configuration and a Sauter diameter of 42.3±0.4 μm, whereas dual-shell microcapsules had a mineralised crown made of SiO₂ (on top of the chitosan shell) leading to a greater Sauter diameter averagely (51.4±0.4 μm). After 15 days in neutral pH water, only 2.5% was released from dual-shell microcapsules, while single-shell microcapsules released ~10% cumulatively. Under compression, dual shell microcapsules yielded a mean nominal rupture stress of 3.0±0.2 MPa, which is statistically much higher than that of single shell ones (1.7±0.1 MPa). This demonstrated that the additional SiO₂ coating enhanced the mechanical properties of the microcapsules significantly, which may be appealing for commercial skincare applications.

The results suggest that green perfume delivery microcapsules with a dual-shell organic-inorganic shell can be effectively fabricated, leading to enhanced mechanical properties and better barrier properties, with potential applications in multiple daily cosmetic products. Future works will focus on assessing the mechanical resistance and fragrance delivery of these microcapsules on soft skin-mimicking substrates. The details of the study shall be presented.

References

[1]. Baiocco, D., J.A. Preece, and Z. Zhang, Microcapsules with a Fungal Chitosan-gum Arabic-maltodextrin Shell to Encapsulate Health-Beneficial Peppermint Oil. Food Hydrocolloids for Health, 2021: p. 100016.

[2]. Anagnosti, L., A. Varvaresou, P. Pavlou, E. Protopapa, and V. Carayanni, Worldwide actions against plastic pollution from microbeads and microplastics in cosmetics focusing on European policies. Has the issue been handled effectively? Marine Pollution Bulletin, 2021. 162: p. 111883.

[3]. Tagg, A.S. and M. Labrenz, Closing Microplastic Pathways Before They Open: A Model Approach. Environmental Science & Technology, 2018. 52(6): p. 3340-3341.