Comparative study of keratin extraction from human hair

Keratin has been attracting interest due to its stability against enzymatic degradation thereby allowing more predictable degradation profile for tissue regeneration applications. While the efficacy of keratin has been demonstrated in different tissue models, there has been no systematic study to investigate and compare the different routes of keratin extraction from human hair. Here, we compared the four commonly used extraction methods and highlighted both physical and chemical differences in the extracted keratin. Keratin was extracted from human hair using one of four common agents, namely, sodium sulfide, peracetic acid, urea and thioglycolic acid. Whereas no specific trend was observed, the keratin extracted through peracetic acid method had significantly different properties. It resulted in lowest yield of 52 μg/mL and low crystallinity but the protein formed aggregates with highest hydrodynamic average size of around 283 nm compared to the other three methods. However, despite greater aggregation, keratin extracted from peracetic acid method exhibited secondary structural conformation similar to thioglycolic acid method. All the four extracted keratin promoted cellular proliferation of osteoblasts compared to the uncoated surface. These results provide new insight into the extraction of keratin from human hair with implications for its use as a biomaterial.