Bioactive gelatin-sheets as novel biopapers to support prevascularization organized by Laser-Assisted Bioprinting for bone tissue engineering.

Despite significant advances in the management of patients with oral cancer, maxillofacial reconstruction after ablative surgery remains a clinical challenge. In bone tissue engineering, biofabrication strategies have been proposed as promising alternatives to solve issues associated with current therapies and to produce bone substitutes that mimic both the structure and function of native bone. Among them, Laser-Assisted Bioprinting (LAB) has emerged as a relevant biofabrication method to print living cells and biomaterials with micrometric resolution onto a receiving substrate, also called "biopaper". Recent studies have demonstrated the benefits of prevascularization using LAB to promote vascularization and bone regeneration, but mechanical and biological optimization of the biopaper are needed. The aim of this study was to apply gelatin-sheet fabrication process to the development of a novel biopaper able to support prevascularization organized by LAB for bone tissue engineering applications. Gelatin-based sheets incorporating bioactive glasses (BG) were produced using various freezing methods and crosslinking (CL) parameters. The different formulations were characterized in terms of microstructural, physical, mechanical, and biological properties in monoculture and coculture. Based on multi-criteria analysis, a rank scoring method was used to identify the most relevant formulations. The selected biopaper underwent additional characterization regarding its ability to support mineralization and vasculogenesis, its bioactivity potential and in vivo degradability. The biopaper "Gel5wt% BG1wt% - slow freezing - CL160°C 24h" was selected as the best candidate, due to its suitable properties including high porosity (91,69+/-1,55%), swelling ratio (91,61+/-0,60%), Young modulus (3,97x104 +/- 0,97x104 Pa) but also great cytocompatibility, osteogenesis and bioactivity properties. The preorganization of HUVEC using LAB onto this new biopaper led to the formation of microvascular networks. This biopaper was also shown to be compatible with 3D-moulding and 3D-stacking strategies. This work allowed the development of a novel biopaper adapted to LAB with great potential for vascularized bone biofabrication.