INVESTIGATION OF THE INFLUENCE OF NYLON-6 VS. NYLON-66 ON THE MECHANICAL PERFORMANCE OF COMPOSITE BONE TISSUE SCAFFOLDS

Despite recent advances in bone tissue engineering, patient-specific treatment of bone pathology using porous osteoconductive scaffolds has faced clinical challenges, which to a great extent stem from a lack of mechanical strength as well as bioactivity (which are critical for osteogenesis, bone bridging, and ultimately bone healing). There is a need for synthesis of not only biocompatible, but also mechanically strong materials with low immunogenicity for bone regeneration. The goal of this industry-academia research work is to fabricate porous, biologically active, and mechanically robust bone tissue scaffolds for treatment of bone fractures, defects, and diseases. In pursuit of this goal, the overall objective of the work is to systematically investigate the effects of Nylon-6 as well as Nylon-66 on the mechanical properties of bone tissue scaffolds, fabricated using fused deposition modeling (FDM), which is a high-resolution additive manufacturing method. In this study, the fabricated bone scaffolds were composed of cellulose fibers, polyamide (nylon), as well as polyolefin (referred to as PAPC hereafter), having complex internal microstructures, designed based on triply periodic minimal surfaces (including Schwarz Gyroid, Schwarz Primitive, Schwarz Diamond, and Neovius microstructures). Three types of scaffolding composite materials, i.e., PAPC-I (Nylon-6-based), PAPC-II (Nylon-6-based), and PAPC-V (Nylon-66-based) were utilized in this study. The FDM fabrication of the bone scaffolds was based on a microcapillary nozzle (heated at 215 degrees C for PAPC-II as well as 235 degrees C for PAPC-I and PAPC-V) with a diameter of 400 mu m, a print speed of 10 mm/s, and a material flow of 120%. Material deposition was on a heated surface, kept at 80 degrees C for PAPC-II as well as 95 degrees C for PAPC-I and PAPC-V. A layer height and line width of 200 mu m and 300 mu m, respectively, were set for the 3D-fabrication process. To avoid filament breakage during the FDM material deposition process, retraction distance as well as retraction speed were reduced to 5 mm and 10 mm/s, respectively. In addition, due to the brittle nature of PAPC-V (having a high Nylon-66 content), it was preheated prior to feeding. The mechanical properties (such as elasticity modulus) of the FDM-fabricated bone scaffolds were characterized using compression testing. Overall, the outcomes of this study will pave the way for patient- specific fabrication of mechanically robust and bioactive bone tissue scaffolds with optimal medical properties for the treatment of bone pathology.