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A. Dobos, P. Gruber, J. Van Hoorick, S. Muehleder, W Holnthoner, S. van Vlierberghe, A. Ovsianikov:
"On-Chip Two Photon Polymerization of Vasculatr Structures";
Talk: The International Conference on Biofabrication 2018, Würzburg; 2018-10-28 - 2018-10-31; in: "The International Conference on Biofabrication 2018", Abstract book, (2018), O38.

One of the central challenges in tissue engineering is the lack of vascularization in the created artificial tissue constructs. There are several different approaches which have been examined for the formation of vascular networks, such as three-dimensional (3D) bioprinting, classical UV-photo-polymerization, micropatterning, and decellularization and reseeding of preexisting extracellular matrixes1. However, the directed alignment of endothelial cells and the construction of a stable perfusable system within a microfluidic channel present difficulties with the previously mentioned methods. Two-photon polymerization (2PP) is a powerful technique for the fabrication of high resolution 3D structures using a femtosecond near infrared laser focused into a photo-polymerizable resin2.
The photosensitive material used throughout this study was a combination of thiol and norbornene modified gelatin (i.e. gel-SH3 and gel-NB4). Compared to traditional (meth)acrylate based systems, thiol-ene click chemistry provides advantages such as less swelling/shrinkage of the hydrogel upon polymerization and insensitivity to oxygen inhibition, which is particularly beneficial in a microfluidic application. By using this dual-component system with a biocompatible diazosulfonate two-photon initiator, it was possible to structure a perfusable microchannel system with physiologically relevant diameters within a microfluidic chip (Figure 1).
Direct encapsulation of co-cultures of human umbilical vein endothelial cells (HUVECs) and supporting adipose-derived stem cells (ASC/TERT1) could also be obtained via 2PP. This approach provides high initial cell loading and homogeneous distribution of cells within the printed hydrogel. The fabricated channels within the gel act as a guide for the alignment of cells within the matrix, creating a more directed vascular tube formation.
This platform for the fabrication of microvascular networks-on-chip using 2PP can advance the development of novel drug screening platforms, and more complex tissue and disease models.

https://publik.tuwien.ac.at/files/publik_273814.pdf