Study on Keratin/PEGDA Composite Hydrogel with the Addition of Varied Hair Protein Fractions

Synthetic polymers, such as poly(ethylene glycol diacrylate) (PEGDA), may make hydrogels more quickly and efficiently; however, these systems are devoid of cell adhesion ligands. As a result, poly(ethylene glycol)-based polymers are restricted in their application to tissue engineering, whereas keratins, a biopolymer functional to the body, have been added to the PEGDA composite hydrogel to make it further applicable. However, as keratin is a mixture of proteins, a keratin-based material may have inconsistent properties due to the complicated keratin composition. This study investigates the effects of different fractions of keratin on the keratin/PEGDA composite properties. A hair was extracted and purified to identify internal keratin filaments (KIFs) and keratin-associated proteins (KAPs). The KIFs and KAPs were mixed with PEGDA to form a hydrogel by photo-cross-linking. The porosity measured in the gels was between 54% and 83%. We also determined the mechanical behavior of the composite through compression and tension tests. These analyses yielded a range of material strengths from 4.0 to 7.1 kPa and from 2.7 to 2.3 kPa, respectively. The gel properties correlated highly with the KAPs/KIFs content, as the two proteins have distinct beta structures. Modulating this ratio results in a keratin/PEGDA composite with more controllable gel properties.