Repair of damaged hair protein fiber by jointly using transglutaminase and keratin

This study focuses on the repair of damaged hair with the joint use of transglutaminase (TG enzyme) and keratin.We first prepared a TG-keratin repair solution with reasonable wool keratin and TG enzyme concentration, and used the soaking process to repair the damaged hair so as to modify protein fibers.We, then, measured the alkali solubility, fracture stress and strain, and swelling rate of the hair samples, before and after the treatment.The results showed that after treatment, samples' alkali solubility reduced from 16.14% to 4.92%, fracture stress increased from 0.832 N to 1.668 N, fracture strain arose from 8.81 mm to 10.17 mm, and swelling rate drops from 38.34% to 2.34%.Both Fourier transform infrared and X-ray diffraction spectroscopies further indicated that combined treatment with keratin and TG enzyme had significant repair effect on the damaged sites, where proteins were exposed with more amide bonds, higher crystallinity, increased percentage of crystalline area over the entire fiber area, and strengthened crosslink activities.Observation under both scanning electron microscope and atomic force microscope revealed smoother surface and fewer warped scales on the surface of hairs after combined treatment with keratin and TG enzyme.To our best knowledge, this is the first application of enzyme technology in damaged hair repair.It opens up a new research direction for green, environmentally friendly, and efficient biological hair care and will play a pivotal role in the application of various protein-based materials.