Developing a Biocompatible Photopolymerized Nonisocyanate Polyurethane Resin for Orthopedic Surgical Guide Plates: Synthesis, Characterization, and In Vitro/In Vivo Biocompatibility

Orthopedic surgical guide plates require materials with excellent biocompatibility, mechanical adaptability, and reliable photopolymerization performance. This paper reports a photopolymerizable biocompatible nonisocyanate polyurethane (NIPU) resin designed for orthopedic surgical guide applications, which eliminates the use of toxic isocyanates and enhances clinical safety. Two structurally distinct NIPUs (NIPUA1 and NIPUA2) were synthesized by incorporating aliphatic ring and chain structures, followed by modification with methacrylic anhydride to impart photopolymerizability. Characterization showed that the NIPUA2 resin exhibited a 1.96-fold increase in both elongation at break and impact strength compared to that of NIPUA1, providing better resistance to intraoperative stress. With a viscosity below 600 mPa·s and a glass transition temperature of 134.74 °C, NIPUA2 also demonstrated good printability and sterilizability. Compared to a commercial resin (TRANS), both NIPUA1 and NIPUA2 showed excellent cytocompatibility with C2C12 myoblasts and MC3T3-E1 osteoblasts, as confirmed by CCK-8, live/dead staining, and flow cytometry assays, which indicated low apoptosis rates and normal cell cycles. In vivo experiments further revealed reduced muscle toxicity and inflammatory responses for the NIPUA resins. This study presents the NIPUA2 resin as a promising material, combining biocompatibility and favorable mechanical properties for orthopedic surgical guides.