ColMA/PEGDA Bioink for Digital Light Processing 3D Printing in Biomedical Engineering

Introduction Digital light processing (DLP) represents a rapid approach to constructing 3D structures with superior resolution. However, it imposes demanding requirements on the properties of bioink. Gelatine methacryloyl has long been the major option but results in limited mechanical properties. The development of collagen-based bioink provides a wider stiffness adjustment range, native bioactivities, and versatility in biomedical engineering applications. Method Collagen solution was obtained via enzymolysis and ultrafiltration and then subjected to methacrylation. The photocrosslinkable bioink comprises collagen methacryloyl (ColMA), poly(ethylene glycol) diacrylate (PEGDA), acetic acid, yellow food dye, and photoinitiator LAP. The 3D structures were fabricated utilising a commercial DLP printer with 405 nm visible light. Results Purified type I collagen can be rapidly obtained via the developed process, and methacrylation is optimised for collagen with much less addition of methacrylic anhydride (MAA) and a high degree of substitution. The ColMA/PEGDA bioink is translucent and low viscosity and is suitable for DLP 3D printing. The printed scaffolds reached a compressive modulus over 100 kPa with 0.6 wt% collagen. Sharp-edged and fine structures (∼500 μm) were obtained by printing. The hydrogels show tunable mechanical properties by adjusting the concentration of the ColMA component. A series of models were fabricated to test the printability, including ear, cube with channels, and scaffolds, which display porous structures with pore sizes of 50 – 150 μm. Conclusions An optimised collagen-based bioink fabrication protocol was proposed for the DLP technique, covering steps from collagen extraction to ColMA/PEGDA bioink formulation and printing. Bioink with tunable mechanical properties is suitable for DLP printing. High-resolution structures can potentially be utilised for various biomedical engineering applications.