3D printing of silk particle-reinforced chitosan hydrogel structures and their properties

Hydrogel bioprinting is a major area of focus in the field of tissue engineering. However, 3D printed hydrogel scaffolds often suffer from low printing accuracy and poor mechanical properties because of their soft nature and tendency to shrink. This makes it challenging to process them into structural materials. In this study, natural chitosan hydrogel scaffolds were, for the first time, reinforced with milled silk particles and fabricated by 3D printing. Compared with pure chitosan scaffolds, the addition of silk particles resulted in up to a 5-fold increase in compressive modulus as well as significantly better printing accuracy and improved scaffold stability. The chitosan/silk inks flowed well during printing; loading of up to 300% silk (w/w) resulted in only minor changes in the rheological properties of the ink. Particle loading also enabled tuning of the surface roughness of the scaffolds and improved scaffolds' biodegradability. The printed composite hydrogel scaffolds showed no cytotoxicity and supported adherence and growth of human fibroblast cells.