3Dprinting of high‐strength, porous, elastomeric structures to promote tissue integration of implants

Abstract

Despite advances in biomaterials research, there is no ideal device for replacing weight-bearing soft tissues like menisci or intervertebral discs due to poor integration with tissues and mechanical property mismatch. Designing an implant with a soft and porous tissue-contacting structure using a material conducive to cell attachment and growth could potentially address these limitations. Polycarbonate urethane (PCU) is a soft and tough biocompatible material that can be 3D printed into porous structures with controlled pore sizes. Porous biomaterials of appropriate chemistries can support cell proliferation and tissue ingrowth, but their optimal design parameters remain unclear. To investigate this, porous PCU structures were 3D-printed in a crosshatch pattern with a range of in-plane pore sizes (0 to 800 μm) forming fully interconnected porous networks. Printed porous structures had ultimate tensile strengths ranging from 1.9 to 11.6 MPa, strains to failure ranging from 300 to 486%, Young's moduli ranging from 0.85 to 12.42 MPa, and porosity ranging from 13 to 71%. These porous networks can be loaded with hydrogels, such as collagen gels, to provide additional biological support for cells. Bare PCU structures and collagenhydrogel-filled porous PCU support robust NIH/3T3 fibroblast cell line proliferation over 14 days for all pore sizes. Results highlight PCU's potential in the development of tissue-integrating medical implants.

Novel three‐dimensional printing of poly(ester urethane) scaffolds for biomedical applications

“…The porosity and pore size of 3D structures have direct implications on their functionality. Open‐pore and interconnected porous networks with tightly controlled pore sizes are essential for tissue vascularization, as well as cell nutrition, migration, and proliferation toward the formation of new tissues 39,61 . AM is nowadays one of the most suitable technologies for the preparation of structures with strictly defined complex three‐dimensional architectures as required for tissue engineering scaffolds.…”

“…Recently, SPU have been explored for FDM processing for biomedical applications. However, most of them were biostable SPU intended for medical devices, 39‐41 and only a few focused in tissue engineering applications 17,20,42‐45 . Among the latter, a segmented poly(ester urethane) (SPEU) with high HS content (77% wt/wt), obtained from the reaction of poly(ε‐caprolactone‐co‐ d,l ‐lactide) diol with a uniform 5‐block chain extender synthesized from butane diisocyanate (BDI) and butanediol (BDO), was filament‐free processed into porous scaffolds with mechanical properties matching those of articular cartilage 42 …”

Meniscal Regenerative Scaffolds Based on Biopolymers and Polymers: Recent Status and Applications

“…Another synthetic polymer that should be addressed is polycarbonate urethane (PCU). PCU is a flexible, biocompatible, biostable and wear-resistant material that can be incorporated in 3D-printed, porous structural scaffolds ( Williams et al, 2015 ; Abar et al, 2020 ). In addition, as a hydrophilic material, PCU can mimic the lubrication mechanism in native synovial joints ( Wan et al, 2020 ).…”

Advantages of Additive Manufacturing for Biomedical Applications of Polyhydroxyalkanoates

“…Due to the possibility of tailoring the Young’s modulus of PHAs, via compounding or synthetic copolymerization, the applicability of this class of biopolymer is potentially much wider and it gives the chance to choose the best grade of copolymer or monomer to mimic the final destination environment [ 71 ]. The mechanical properties of human tissue can considerably vary, for example the Young’s modulus for granulation tissue is ~0.2 MPa, for fibrous tissue is ~2 MPa, for articular cartilage is 1–20 MPa, for intervertebral disc is 6–50 MPa, for tendon is 1–3 GPa and for mature bone is ~6 GPa [ 72 , 73 ]. Similarly, the Young’s modulus for PHA family may range from ~600 MPa for some grade of copolymers such as P(3HB-4HB) to ~3 GPa for PHB.…”

“…Moreover, with AM approach is possible to tune the mechanical properties of the final device in order to modify the stiffness of the implant to match that of the original tissue, and hence mitigating the problem of stress concentrations. In fact, varying the structure and the design of the 3D-printed device, it is possible to increase the porosity and thereby to decrease of one order of magnitude the Young's modulus of the implant [73,101,102]. With the spreading of additive manufacturing (AM) techniques, a new light on the modern research scene has been turned on 3D printing for biomedical applications (e.g., tissue engineering, prosthesis, or drug delivery), due to the possibility of tailoring the final design and the manufacturing of complex structures, eliminating the costs and time needed for the construction of molds [97,98].…”