3D printing of keratin hydrogel : optimization

Abstract

The KPE10K, a hydrogel system which is named after its components: reduced Keratin and PEG-Norbornene (Mw: 10,000 g/mol) as prepolymer and Eosin Y as a visible light-crosslinkable photoinitiatior was studied for its potential to be functionalized as a bioink for extrusion-based bioprinting. Protein concentration of the reduced total keratin, the free thiol group concentration of the pristine and reduced total keratin, and the FTIR spectra of the pristine and reduced total keratin were analysed for extraction and reduction process optimization. Droplet printing was performed at different KPE10K concentrations (10%, 15%, and 20% (w/v%)) at varying printing parameters (extrusion pressure, injection time, etc.) and the average diameter of the printed droplets using the investigated parameters were recorded. Mechanical tests and rheological tests for KPE10K prepolymers and hydrogels and FTIR spectra of the hydrogels were conducted and analysed to confirm if the crosslinking process had succeded. It was observed during rheological test for crosslinked hydrogels that the material has solid-like behaviour indicated by larger storage modulus value than its loss modulus although FTIR characterization that was done could not support the presence of chemical group that should be found after crosslinking process. The same bioink concentrations were then used to print 2D models with varying printing parameters (extrusion pressure and injection time). It was found that 20% KPE10K hydrogels were suitable for printing 2D models. Attempts to print 3D models were also performed, although difficulties were encountered when printing multiple layers. In future, this study may provide readers with a better understanding to the printing parameters required to 3D bioprint keratin scaffolds at higher resolutions with the aim of supporting long-term cellular growth for biomedical applications.