Visible light-induced crosslinking of unmodified gelatin with PEGDA for DLP-3D printable hydrogels

• A DLP 3D printable hydrogel with chemically incorporated unmodified gelatin is presented. • Cold water fish gelatin acts as camphorquinone co-initiator for the photocuring of PEGDA. • Reactivity and crosslinking density of the hydrogel are increased by increasing gelatin content. • Cell proliferation assay and fluorescence microscopy show good cell viability and proliferation. • 3D digital light processing of this material leads to the creation of precise structures. The possibility to 3D shape hydrogels is attracting an enormous interest in the biomedical field both for their application as scaffold or for the design of new medical hydrogels. Digital light processing (DLP) printing can create layer-by-layer models with high resolution and printing speed. Herein, a hybrid natural-synthetic hydrogel is propsed using cold-water fish gelatin as innovative co-initiating species of a camphorquinone photo-initiator instead of the traditional aliphatic or aromatic amines, for the crosslinking of PEGDA monomer. Such system allows to chemically bound gelatin to the PEGDA monomer without any previous modification and leads to the production of DLP-3D printable hydrogels. The real-time photorheological measurements showed that Gelatin behave as a binder during photopolymerization and ATR-FTIR spectroscopy proved that gelatin segments were chemically incorporated within PEGDA network. Mechanical and biological properties were improved by increasing gelatin content. Furthermore, the 3D digital light processing of this material leads to the creation of precise and rapidly printed structures that are biocompatible and able to support cell viability and proliferation. Considering those features, the proposed hydrogel may be a promising candidate in 3D-printed devices for cell culture.