[L’industrie c’est fou] Silk-based particles to replace microplastics

Various cosmetic products are used today to make the skin feel silky smooth, but the industry obviously never thought of using it directly in their products. This is what a team of researchers from the Massachusetts Institute of Technology (MIT) and the German giant BASF did, developing “biodegradable” silk-based microplastics, which they tested in a study published in the Small magazine. These so-called “voluntarily added” microplastics are mainly used in the pesticide and cosmetics sectors.

A pollution factor

To produce these “microcapsules”, the technique of micro-encapsulation is used. It consists of wrapping active ingredients of microscopic size (such as vitamins, fragrances or herbicides) in a matrix, a bit like silkworms in their cocoon. This protects them from various external factors, such as heat or oxidation. The main materials used for these matrices are polymers derived from petrochemicals, such as polyethylene or polypropylene.

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For the authors of this study, there is an “urgent need across several industries to develop biodegradable substitutes for added microplastics”. Because if the majority of microplastics that end up in the oceans come from the degradation of larger plastic waste, between 15 and 31% of these particles come from microplastics voluntarily added, according to the International Union for the Conservation of Nature. This study led the European Commission to propose a ban on synthetic microplastics. A decision on this measure should be taken at the end of 2022.

A “polymorphic” protein

As an alternative, the researchers chose fibroin, a structural protein from silk. A material that ticks all the boxes for potential industrial application: high availability, food grade safety, easy regeneration and its “polymorphism”, which allows the protein to easily transition from a hydrophobic to a hydrophilic structure . This property makes it possible to integrate active principles that are both hydrophilic, such as certain vitamins, and hydrophobic, such as herbicides.

The results of this study are encouraging: tested on corn plants for six days, a spray based on silk microcapsules is less aggressive than traditional products. There is currently no planned industrialization of this solution by BASF.

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