Characterization and Optimization for PPF/NVP Scaffolds

Objectives: Tissue engineering offers a promising way to regenerate bone in large defects. Biomaterial scaffolds are a key component of tissue engineering. Fabrication of scaffolds with optimal porosity and structural durability poses a challenge for bone regeneration. This study investigates weight % and pore size of poly(propylene fumarate) (PPF) scaffolds. Current PPF scaffolds use 70 weight % porogen content with 300-500 um pore size. The purpose of this study is to determine the ideal pore size and porosity for PPF scaffolds (8mm diameter) to allow for maximal in-growth of cells and nutrients within the biomaterial implant while maintaining structural integrity during processing and post-implantation. Methods: PPF of Mn 1922 was synthesized and cross-linked with N-vinylpyrrolidone (NVP) yielding a ratio of PPF/NVP 1:1. Scaffolds (N=84) were fabricated using 80, 82, 84, 86, 88, and 90 weight % salt content with salt sizes of 300-500 um and 500-700 um. Scaffolds were thermally cross-linked and then leached in de-ionized water. Results: Data was quantitatively analyzed using Skyscan 1172 micro-computed tomography (Micro-CT). Qualitative analysis was conducted using scanning electron microscopy (SEM) to assess the pore interconnectivity. Micro-CT analysis determined the porosity of the scaffolds. The 86% weight scaffolds maintained a porosity of 79% while remaining feasible for in vivo use. Although the higher porogen content scaffolds yielded higher porosity levels, the scaffolds were far too weak to use for implantation. Conclusions: The higher porogen content scaffolds (88, 90 weight %) shrunk in size and collapsed upon themselves. They were very fragile and difficult to work with. 80-86 weight % scaffolds maintained their cylindrical shapes. 86 weight % scaffolds allow for maximal optimization of scaffold properties for tissue engineering applications.