Chitosan

Chitosan in powdered form (source)

Chitosan

Due to logistical difficulties during the pandemic, we have not yet been able to prototype the chitosan layer of the mask. However, the research we have done gives us a solid base for when the opportunity to prototype arrives. We made a mock-up of the chitosan layer using soy protein for our prototype.

Chitosan fibers. We intend to electrospin chitosan to create a similar fabric. (source)

What is chitosan?

Chitosan is a derivative of chitin, which is a common polysaccharide found in arthropods and fungi. It can be extracted from sources such as seafood waste and certain mushrooms. Chitosan is not harmful to the environment and is completely biodegradable. A comparison of chitin and chitosan can be seen in Figure 1.

Why chitosan?

As shown in the figure, chitosan possesses a primary amino group, which is useful because it gives chitosan its antibacterial properties, as it can harm bacterial cell walls. Treatment of chitosan under dilute acid conditions and low temperature can protonate the amino group, creating a positively charged layer useful for the electrostatic attraction mechanism. This may seem to contradict the previous statement; if NH2 is antibacterial, why would we want to change it? Ideally we could create a mixture of both protonated and unprotonated amino groups, to both kill bacteria and collect charged groups. Knowing that chitosan has a pKa of 6.5, we could treat it with very little acid and at a pH of 6.5, have a mixture of both protonated and deprotonated groups. When this charged chitosan is electrospun, we can create chitosan nanofibers, and collect them for use in our chitosan layer.

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