Enhancing the Shape-Memory Performance of Biocompatible Scaffolds Based on Chain-Extended Poly(L-Lactide-co-Glycolide-co-Caprolactone) Terpolymers

Shape-memory polymers have a wide range of uses from biomedical devices and soft robotics to flexible electronics and aerospace engineering. Herein, we report a novel chain-extended poly(L-lactide-co-glycolide-co-caprolactone) terpolymer (PLGC) preparation route using hexamethylene diisocyanate (HDI) as a coupling agent to extend PLGC chains and improve the shape-memory performance of the material with a rapid macroscopic recovery time of only 30 s. The PLGC scaffolds were synthesized and fabricated using a freeze-drying technique to obtain shape-memory scaffolds. Mechanical testing showed that only 0.0075 mol% of HDI was sufficient to improve the stress at break of PLGC from 8.1 to 18.1 MPa and tensile strength from 10.3 to 18.4 MPa. The findings of our study illustrate the efficacy of the HDI coupling agent in enhancing the strength and recovery ratio up to 99.4 % by strain recovery of PLGC terpolymer scaffolds while ensuring a non-toxic environment conducive to cell viability. Cytotoxicity tests (cell viability and proliferation) of the PLGC with and without HDI, performed using the L929 cell line, showed that the shape-memory materials are non-toxic. The proliferation of the human osteosarcoma cell line (MG-63) demonstrates significantly greater relative cell count (157 %), mineral production (8 times of enhancement in absorbance at 570 nm), and viability when cultured on the PLGC-0.0075 mol%HDI scaffold in comparison to the other scaffolds. We anticipate that our research will serve as an initial step towards the broad utilization of PLGC-HDI scaffolds as shape-memory bone scaffolds for addressing diverse bone defects in reparative procedures.