Synthesis and structure-property correlations of polyurethanes for additive manufactured biomedical materials

In recent decades, 3D printing has gained substantial attraction in the field of tissue engineering (TE) scaffold fabrication due to its exceptional precision, convenient manufacturing conditions, and rapid production capabilities. Among the various techniques, stereolithography (SLA) and direct ink writing (DIW) are the most applicable techniques in this field. However, the availability of biodegradable and biocompatible synthesized polymers, particularly from the polyurethane (PU) family, remains limited for the purpose of 3D printing. The primary objective of this research was to develop biodegradable and biocompatible PUs, encompassing both isocyanate-based and non-isocyanate-based (NIPUs) polyurethanes. These polymers were specifically designed for applications in nerve and skin regeneration. A solvent-free approach was utilized to synthesize photo-cross linkable PU resins, effectively applied for the SLA technique. Furthermore, the incorporation of PEGylated graphene oxide nanoparticles into the resin composite was executed to confer conductivity, a crucial attribute for scaffolds intended for nerve regeneration. Then the nerve guidance conduits (NGCs) were printed with very precise geometry by SLA. Additionally, a novel generation of isocyanate-free PUs was successfully synthesized utilizing six distinct diamines. This endeavor aimed to investigate the correlation between polymer structure and resultant properties. Based on the chemical and physical characteristics of the synthesized NIPUs, a specific variant containing cystamine (NIPU-Cys) was identified for further exploration in 3D printing applications. To enhance its properties, the chosen polymer was combined with an antibacterial chitosan derivative, synthesized by a doctoral researcher within the Polymer Technology Research Group at Aalto University (Isabella Lauren). This antibacterial hydrogel composite was effectively 3D printed using the DIW technique, presenting the potential for wound healing applications.