A novel approach to fabricating interconnected porous PCL-based biodegradable scaffolds for articular cartilage tissue engineering

Tissue engineering has recently attracted great attention in science, engineering, and medicine as a promising strategy to fabricate tissue by combining cells and bioactive agents in a scaffold aimed at replacing diseased and/or damaged tissue. This study presents and investigates a novel fabrication approach aimed at developing interconnected porous scaffolds for cartilage tissue engineering. The main objective was to develop a versatile and simple approach to fabricating interconnected porous scaffolds without the use of potentially harmful solvents. The approach consists of three major steps: cryomilling, compression molding, and porogen leaching for the preparation of interconnected porous scaffolds by selective leaching of porogen(s) from blends and composites created by combining cryomilling with conventional compression molding. It was hypothesized that cryomilling would create homogeneous blends and composites and produce co-continuous binary blend morphologies to fabricate a wide range of interconnected porous scaffolds by selectively leaching one continuous phase from the co-continuous structure. Poly(ε-caprolactone) (PCL) was chosen as the base material with poly(ethylene oxide) (PEO), which is immiscible with PCL, as a water soluble biodegradable porogen. Polyglycolide (PGA) and multi-walled carbon nanotubes (MWCNTs) were also incorporated as potential additives used to manipulate the degradability, hydrophilicity, stiffness, strength, and cell stimulation of the biodegradable PCL scaffold. The ultimate goal was to create scaffolds that could potentially mimic the 25.5 MPa, and compressive strength at 10% strain from ~1.2 MPa to 1.8 MPa. Furthermore, those scaffolds had a remarkably fast degradation compared to the PCL polymer slow degradation rate. Addition of MWCNTs to PCL and PCL/PGA resulted in significant changes to scaffold morphology in spite of the persistent interconnected porosity. Partially continuous structures exhibiting rough textures were observed. Mean pore sizes were estimated in the range of ~3 μm to ~5 μm. MWCNTs were occasionally seen on wall surfaces creating rough and nanotextured surfaces. Other nanocomposite scaffolds properties include: water uptake in the range from ~79% to 81%, compressive modulus from ~29 MPa to 65 MPa, and compressive strength at 10% strain from ~1.6 MPa to 3.2 MPa. The fabricated PCL-based scaffolds properties imply that they could be interesting candidates for cartilage tissue engineering. This research confirmed the preparation of blends possessing highly continuous or co-continuous morphologies using solid-state blending followed by melt molding. The study has demonstrated the potential of this approach as a route to obtain interconnected porosity in PCL scaffolds. Once the co-continuous blend has been prepared, extraction of the porogen yielded an interconnected porous scaffold. The research showed that control of pore size, size distribution, and porosity can be effectively obtained. In summary, the results of this research provide significant insight into an original scaffold fabrication approach for the tissue engineering of articular cartilage that will lead to new composites and blends in scaffold manufacturing.

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