3D-printing of Urethane-based Photoelastomers for Vascular Tissue Regeneration

Abstract

The mechanical properties of materials designated for vascular tissue replacement are of crucial importance. The elastic modulus, the tensile strength as well as the suture tear resistance have to be adjusted. Our approach is to use photopolymers for artificial vascular grafts. Via the layer-by-layer photopolymerization of suitable resin formulations as performed in additive manufacturing (AM) very complex structures are realizable. Hence AM offer the possibility to create cellular structures within the artificial grafts that might favor the ingrowth of new tissue. Commercially available urethane acrylates (UA) were chosen as base monomers since urethane groups are known to have good cell-adhesion behavior and poly-UAs show adequate mechanical performance. The mechanical properties of the photoelastomers can be tailored by addition of reactive diluents (e.g. 2-hydroxyethyl acrylate, HEA) and thiols (e.g. 3,6 dioxa-1,8-octane-dithiol) as chain transfer agents to comply with the mechanical properties of natural blood vessels. To examine the suture tear resistance a new testing method has been developed. Finally, a formulation containing 30 wt% UA and 70 wt% HEA complies with the mechanical properties of natural blood vessels, shows good biocompatibility in in-vitro tests and was successfully 3D-printed with digital light processing AM.

Inkjet Printing of Soft, Stretchable Optical Waveguides through the Photopolymerization of High-Profile Linear Patterns

“…Liska et al 17 used hydroxyethyl acrylate (HEA) as a reactive diluent for polyurethane acrylate resins. In spite of its excellent polymerization properties, HEA is toxic and irritant.…”

“…An inkjet-printing strategy toward optical waveguides was previously proposed in the literature but resulted in relatively flat patterns, unsuitable for efficient light transport. 15,16 Liska et al 17 previously utilized commercially available acrylates and tailored photoelastomers from the Genomer series (Rahn AG) to successfully 3D-print biocompatible structures with mechanical properties matching those of natural blood vessels, i.e., high strength and stretchability. Adding to that the good optical transparency of polyurethane acrylate inks, Genomer-based inks were considered good candidates for printing stretchable optical waveguides.…”

Bioprinting of Blood Vessels

“…One group demonstrated the successful development and tuning of a urethane-based photoelastomer suitable for vascular tissue regeneration [59]. Fabrication with such materials is limited in stereolithography due to the photopolymerization requirements.…”