Fabrication of precise cylindrical three-dimensional tissue engineering scaffolds for in vitro and in vivo bone...

It is sometimes necessary to form highly porous polymeric tissue engineering scaffolds into various shapes and sizes. Ideally, in these cases, the three-dimensional morphology should be maintained to the outer margins of the scaffold so as to provide optimum function. Many biodegradable polymeric scaffolds are soft and delicate, however, and their poor physical strength presents a challenge when cutting these materials into the required shapes. We describe a simple device that can be used quickly and accurately to cut cylindrical shapes from such delicate polymeric scaffold materials, which maintain their morphological features to the margins of the shapes produced. We demonstrate that the device can be used to create scaffolds with reproducible dimensions having an SD in mass of less then 6%. The in vitro utility of scaffolds cut with the device was established through demonstrating bone marrow-derived cell invasion into fibrin-filled scaffolds that fit precisely into the wells of 24-well plates. We also demonstrate the in vivo utility of precise cylindrically shaped scaffolds by observing rapid bone invasion into 2.4-mm diameter scaffolds that have been placed into drill hole defects in the distal femur of young rats. When scaffolds are filled with fibrin before implantation as part of a bone tissue engineering strategy, less blood fills the defect site and the fibrin is gradually remodeled and replaced by bone. The ability to cut precise cylindrical scaffolds in the millimeter size range has allowed for the creation of a new small animal model that may prove useful for screening tissue engineering scaffolds for further study.