Could silk help solve our microplastics problem?

Story at a glance

  • Microplastics have been found in both human and animal blood, along with soil, water, and air samples.

  • Encapsulated active materials in consumer products account for about 10 to 15 percent of all microplastic pollution.

  • New research suggests using discarded silk can serve as a solution to this specific type of pollutant.

A team of researchers at the Massachusetts Institute of Technology may have found a potential, inexpensive solution for some sources of microplastics. 

Using a system based on silk, the investigators were able to develop a biodegradable, easily manufactured substitute that can replace microplastics found in agricultural products, paints, and cosmetics. Their process was published in the journal Small. 

Microplastics are tiny bits of plastic that have been found in air, water, and soil samples around the world — in addition to animal and human bloodstreams — while those added to consumer products add up to an estimated 50,000 tons a year just in the European Union (EU). 

These intentionally added microplastics are thought to account for between 10 and 15 percent of total microplastics existing in the environment. 

In these consumer products, micro-sized active materials such as vitamins, fragrances, and herbicides “are enveloped or embedded in a matrix to protect the core actives from external influences (oxidation, heat, evaporation, etc.), control their release for a targeted period and minimize their possible adverse effects on the surrounding,” researchers explained. This process is called microencapsulation. 

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However, the capsules are made of plastic, and before now, no suitable alternatives existed. 

A nature-based, biodegradable replacement in the form of silk protein offers an already widely available solution. Unlike fine strings needed for silk clothing, non-textile quality cocoons can be used in this new microencapsulation process, and a water-based method can be employed to dissolve the silk fibers.

The material produced with this new process can also work with existing manufacturing equipment. Silk is a non-toxic material and degrades naturally in human bodies, while the process can also be completed with used or discarded silk fabric that would otherwise end up in a landfill.

Researchers tested the material with an existing herbicide product on a corn crop, and found it was superior to an existing commercial product, as it inflicted less damage on plants. 

“There is a strong need to achieve encapsulation of high-content actives to open the door to commercial use,” said study co-author Benedetto Marelli in a press release. “The only way to have an impact is where we can not only replace a synthetic polymer with a biodegradable counterpart, but also achieve performance that is the same, if not better.”

More research is needed to better understand the effects of microcapsule size and wall thickness, along with other characteristics of the material, authors concluded.

Published on Jul. 25, 2022

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