Search

Skin is the largest organ of every mammal and protects against sources of danger like hypothermia or dehydration. Skin defects are often caused by soft tissue trauma, burns, or surgical resections. Consequently, treatment efforts are aimed at restoring skin integrity on the one hand. Nevertheless, reconstruction of the underlying connective tissue is important for a full functionality of the tissue as well, on the other hand. Therefore, new technologies are under investigation, allowing for the de novo engineering of connective tissue and skin within the patient’s body. The arterio-venous (AV) loop technique represents one such promising approach. To this end, a vascular loop is generated microsurgically, placed inside a Teflon chamber, accompanied by a decellularized matrix, and subsequently implanted under the patient’s skin for three to four weeks. In the present study, we investigated new stereolithographic strategies to print patient tailored chambers. These newly designed chambers can help address several new properties: their geometry is tailored to the individual implantation site of the patient and their material is more elastic allowing for more comfort during the cultivation phase. We investigated new classes of photopolymers, which are more elastic than Teflon and can be photo crosslinked. We tested them for their biocompatibility using 3T3-fibroblast cell culture and optimized the crosslinking protocols of the polymer using FTIR-analysis and improved the respective washing protocols. Furthermore, their mechanical properties and sewability are important for fixation of the chamber during the time of cultivation. Therefore, simple mechanical tests have been carried out.

Das Ziel von HyAdd3D ist es, mit neuer Anlagentechnik komplexe Bauteile additiv zu fertigen und gleichzeitig den Anforderungen einer Multimaterialfertigung gerecht zu werden. Das Projekt umfasst die Entwicklung einer hybriden Verfahrenslösung, welche in der Lage ist, neue Materialien mit funktionalen Zusatzstoffen zu verarbeiten. Der Beitrag beschreibt den HyAdd3D-Ansatz und beleuchtet den aktuellen Projektstand. Abschließend werden die aktuellen Ergebnisse zusammengefasst und ein Ausblick auf die folgenden Entwicklungsschritte gegeben.

The future vision of implants comprises individually tailored prostheses and the generation of artificial tissue and organs generated from the patient's own cells. In order to develop artificial, biomimetic structures which perform as well as natural ones, we need fabrication processes that do not set any limits to the generation of shapes, and materials that allow for tailoring of their physical, chemical, and biological properties. We introduce new biocompatible materials for the manufacturing of flexible structures by freeform fabrication.

Introduction: To date only single in vitro engineered tissues are transferred to clinical approaches due to todays inability to fabricate suitable, artifical vascular systems. Combining inkjet printing with high-resolution multiphoton polymerization (MPP) enables us to generate branched, tubular systems with diameters << 1 mm. New synthetic polymers were tailored to match the needs of the technical building process and the elastic properties of blood vessels. The polymers were biofunctionalized to achieve a close coating with endothelial cells (ECs). Experimental Methods: Based on numerical simulations, branched tubular scaffolds were fabricated by combining inkjet printing and MPP. Precursor polymers, cross linking agent, photo initiators and solvent additives were optimized to yield photo reactive inks with customizd E-moduli. Crosslinked polymers were modified with derivatized heparin and RGD and analyzed by XPS and colorimetric methods. Viability, proliferation, functionality of primary human microvascular ECs on the substrates was determined, using several assays and immunocytological stainings. Results: A set-up for integrating inkjet printing and MPP has been designed with which branched vessel scaffolds have been fabricated. The diameter of the tubes can range between 20 µm and several millimeters. Material compositions have been developed to achieve E-Moduli of 2-2000 MPa after crosslinking, the lower are similar to natural blood vessels. Suitable aftertreatment ensured biocompatibility of the processed polymers, thereafter thio-heparin and RGD have been covalently bound on the surface. On these biofunctionalized substrates an increased adhesion, viability and proliferation of ECs has been determined in comparison with unmodified substrates. EC-typical antigene expression has been observed by immunocytological stainings on all substrates. Conclusion: The presented combination of rapid prototyping techniques makes it possible to generate small diameter vessel-like systems that can be applied for supplying in vitro engineered tissues in a larger scale.