Fabrication of 3D cryo-printed scaffolds using low-temperature deposition manufacturing for cartilage tissue engineering

Osteoarthritis is predicted to become the fourth leading cause of disability by 2020. Engineered scaffolds have shown promise in the field of cartilage tissue engineering. The primary aim of scaffolds is to mimic the architecture and mechanical properties of the native cartilage to promote successful regeneration. This study employs cryo-printing, an adaptation of low-temperature deposition manufacturing (LDM), which integrates 3D printing and directional freezing. A 3D printer was developed to allow direct printing onto a cold plate set at −40 °C. Scaffolds were fabricated using various concentrations of polycaprolactone (PCL) (6%, 8% and 10%), print-head temperatures (35 °C and 45 °C) and needle diameters (0.8, 0.6 and 0.3 mm). Adjusting these parameters influenced scaffold morphology and pore diameter. More specifically, scaffolds exhibited average pore diameters ranging from 3.597 ± 0.077 µm to 5.808 ± 0.213 µm between different polymer concentrations. Additionally, Young's modulus of scaffolds ranged between 0.76 MPa and 2.03 MPa in the 0–10% strain region, which is within the range expressed by the native cartilage. Ultimate tensile properties of scaffolds was found to correlate with polymer concentration and print-head temperature. Incremental Young's modulus was significantly reduced in the 10–20% strains compared to the 0–10% strains with the use of different print-head temperatures and needle diameters. Needle diameter had no influence on the mechanical properties of scaffolds. Overall, this study shows that cryo-printing allows the fabrication of scaffolds with highly reproducible pore diameters and mechanical properties that can be easily tuned by changing polymer concentration and print-head temperature.