Sustainable and smart keratin hydrogel with pH-sensitive swelling and enhanced mechanical properties

- A novel method for keratin hydrogel obtaining is presented.
- This is a green and low cost method that uses aqueous media and ethanol as reagents.
- This is a sustainable process that reuses agroindustrial waste as keratin source.
- This keratin hydrogel is endowed with pH-responsive reversible swelling.
- Chain reorganization instead of electrostatic repulsion drives the swelling response.

Protein based hydrogels are a very interesting type of biomaterials with many probed strengths related to their source and chemical structure. Biocompatibility and biodegradability are accompanied by affordability when it comes to low cost sources. The main keratin source is agroindustrial waste, such as feathers, horns, hooves, hair and wool. Thus, the main cost of keratin hydrogels derives from their processing. Here is presented a new strategy for the obtaining of a keratin hydrogel with enhanced mechanical properties using low cost reagents. This keratin hydrogel is stiff enough to allow handling without special cares and also presenting a reversible pH-responsive behavior. The minimum swelling is observed at low pH due to a collapsed and disordered protein network with water tightly adsorbed to the hydrophilic sites. The swelling rises significantly above pH 6 and the maximum swelling appears above pH 8 where an expanded network allows water to enter to the pores.

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