Assessment of soy protein addition to develop bio-based inks and biocompatible scaffolds by digital light processing 3D printing.

The development of advanced materials for Digital Light Processing (DLP) based 3D printing has gained increasing interest due to the DLP precision and ability to print complex structures. In this context, an innovative approach was presented by incorporating 25, 40 and 50 % (w/v) soy protein isolate (SPI), a biopolymer derived from soybean industry by-products, into the formulation of a DLP-resin, with the aim of developing biocompatible scaffolds for tissue engineering applications. These formulations showed suitable rheological properties for 3D printing, with viscosity values lower than 10 Pa.s during the whole shear-rate ramp. The samples were successfully printed with well-defined geometries and their physicochemical characterization as well as mechanical testing confirmed the structural integrity of the material. Due to their mechanical performance, the scaffolds with 25 wt% SPI were selected for further analyses; in particular, the effect of glycerol or deep eutectic solvent (DES) addition and their biocompatibility. Biocompatibility assays with human fibroblasts (HS27) revealed high cell viability, increasing the metabolic activity up to 96 % after 3 days. This study underscores the feasibility of biopolymers to develop resins for high-precision additive manufacturing, offering an environmentally friendlier alternative to conventional synthetic materials while addressing the growing demand for biocompatible and customizable scaffolds.