Methods for modeled bioprinting of hard and soft tissues

Abstract

This study presents new methods to utilize bioprinting technology to recreate hard and soft tissue based on medical imaging. Using the proposed methods, medical DICOM files are converted into STL files and bioprinted into PCL:HA scaffolds. The high model precision provides potential for their use as image-based, implantable biological scaffolds for musculoskeletal applications.Initially, femur segments were recreated for the hard tissue model and spinal discs for the soft tissue model. All models were bioprinted utilizing PCL:HA ratios of 80:20 for ease of manufacturing. Printing methodology circumvents the need for solvents in PCL printing, allowing for scaffolds to be created in a safer, faster, and more cost-effective manner.For the hard tissue models, DICOM files are converted directly into STL files utilizing the software 3D Slicer. The software directly segments the imaging to print a specified section of hard tissue. For soft tissue models, a protocol called negative imaging was created to generate soft tissue models based on hard tissue imaging. This method is employed due to the difficulty of isolating soft tissue, such as spinal discs, in DICOM files. The protocol utilizes CAD to generate a mold of the soft tissue from the surrounding hard tissue. The mold is then cleaned in Meshmixer to fix imperfections.To gauge the strength of various PCL:HA ratios for future tissue models, PCL:HA ratios from 90:10 to 65:35 were printed into standardized cubes and compression tested to determine stiffness. Various infill geometries were also tested to see their effect on the scaffold stiffness.