Synthesis of Photopolymerizable Hydrophilic Macromers and Evaluation of Their Applicability as Reactive Resin Components for the Fabrication of Three-Dimensionally Structured Hydrogel Matrices by 2-Photon-Polymerization

Two-photon polymerization (2-PP) is a promising new photolithographic technique to fabricate three-dimensional (3D), micro-and nano-structured tissue engineering scaffolds from photopolymerizable monomers. Although various photo resins are known for the use in 2-PP, there is currently a need for photo-curable monomers processable by 2-PP to generate biocompatible 3D-structured hydrogel materials for soft or cartilage tissue regeneration. In the present work hydrophilic methacrylate monomers and macromers based on synthetic poly(glycerine) and poly(ethylene glycol) urethanes as well as on the biopolymers dextran and hyaluronan is prepared. The photopolymerization behavior of these substances are investigated and formed hydrogel networks are studied with regard to their mechanical properties, cytocompatibility, and hydrolytic degradation. Based on these examinations simple 3D model structures are fabricated from these photo-curable monomers and macromers by 2-PP. It is shown that both the synthetic monomers and the dextran methacrylate macromer are efficient 2-PP starting materials whereas the hyaluronan methacrylate can be used for 2-PP only in combination with suitable water-soluble co-monomers. No cytotoxic effects are found in preliminary chondrocyte cultivation experiments on 2-PP-fabricated scaffolds but initial cell adhesion on the hydrophilic scaffold surfaces is rather low and has to be further improved to apply these structures in tissue engineering.