Green and Sustainable Technology for High-Efficiency and Low-Damage Manipulation of Densely Crosslinked Proteins

Abstract

A two-step technology using nontoxic and eco-friendly chemicals is developed for the durable setting of densely/highly crosslinked proteins, such as wool and hair. Currently, most technologies for morphological modification are effective only for materials from non-highly-crosslinked proteins and cellulose. Before their morphological change, only water is needed to interrupt hydrogen bonds and ionic linkages, which stabilize the relative positions of molecules in non-highly-crosslinked proteins and cellulose. However, highly crosslinked proteins contain disulfide crosslinks, which are insusceptible to water. Thus, the controlled cleavage of disulfide bonds is required for creating new morphologies of highly crosslinked protein materials, such as hair and wool. Herein, cysteine and citric acid (CA) were used for the two-step setting of highly crosslinked proteins. This recipe showed better morphological change and less mechanical loss than commercial hair styling products. A reaction between CA and keratin was proposed, and verified via NMR and Raman spectra and titration. This technology could be a prospective alternative to achieve durable hair setting, anticrease finishing of wool textiles, and other durable morphological changes needed for highly crosslinked proteins.

Enhancing Strength of Wool Fiber Using a Soy Flour Sugar-Based “Green” Cross-linker

“…7 In most cross-linking cases involving proteins, bifunctional cross-linkers, such as glyoxal, glutaraldehyde, diisocyanates, and carbodiimides have been used. 8−10 Some formaldehyde-based cross-linkers have also been reported. 11 These cross-linkers are skin irritant and toxic, not only to cells and biological systems but also to the environment.…”

“…Glycine, leucine, proline, valine, alanine, isoleucine, and phenylalanine amino acids without reactive groups on their side chains account for about 30% of amino acids . In most cross-linking cases involving proteins, bifunctional cross-linkers, such as glyoxal, glutaraldehyde, diisocyanates, and carbodiimides have been used. − Some formaldehyde-based cross-linkers have also been reported . These cross-linkers are skin irritant and toxic, not only to cells and biological systems but also to the environment. , As a result, they pose a great danger to the health of the users.…”

Natural ‘Green’ Sugar-Based Treatment for Hair Styling

“…There have been some attempts to use non-toxic reducing agents to break the disulfide bond in keratin and re-form them to attain straightness. The use of cysteine as a 'green' reducing agent and the use of polycarboxylic acids, such as citric acid, butane tetracarboxylic acid (BTCA), malic acid, and others, to crosslink hair have been studied [2,[13][14][15]. However, all these are two-step processes that still involve the reduction step (breaking the disulfide bonds), which permanently affects the strength of hair.…”

Polymeric Hydrogel Coating for Modulating the Shape of Keratin Fiber

“…From here, can occur the removal of the hair cuticle hydrophobic top-layer, and consequent reduction of surface hydrophobicity (Cruz et al, 2017). The development of processes with non-toxic chemicals to manipulate the shape of the hair (Xu et al, 2017) and maintaining it integrity still remains an open challenge.…”