Abstract text (incl. figure legends and references)
Biofabrication emerged as a promising field for fabricating 3D tissue for in vitro models or replacing damaged tissue. However, biofabrication of viable and functional tissue remained challenging due to the lack of vascular structures in newly developed tissue leading to hypoxia and cell death in the core. Here, we present a new perfusion-adapted bioreactor system that incorporates multiple advantageous properties, simplifying the usage. The bioreactor is 3D printed with a non-cytotoxic and ethanol resistant resin and uses luer-lock adapters to connect to commonly used perfusion systems. The most important feature of the bioreactor is a reliable way to connect microchannels inside a hydrogel to a perfusion system. This is achieved by fixating a melt electrowritten (MEW) sacrificial structure made of thermoresponsive poly-(2-cyclopropyl-oxazoline) (PcPrOx) inside of the bioreactor. After embedding it into a photo cross-linkable hydrogel, the microchannels were fabricated by lowering the temperature which dissolves the printed PcPrOx structures. Furthermore, the bioreactor can be easily adapted to allow multi-fluid and multi-layer perfusions and is sealed by pressing a thin gas permeable PDMS membrane between the bioreactor and a lid. The necessary force is provided by two quartets of embedded magnets, one quartet inside of the lid and the other one inside of the bioreactor. The attraction between them presses the PDMS membrane and seals the inner chamber water- and airtight. The magnetic sealing does not necessitate clamps or similar tools and makes it easy to handle. The channels can be observed in the closed bioreactor through a window under the microscope. Additionally, the inner chamber was specifically shaped, so that the meniscus between the hydrogel and the bioreactor walls won"t interfere with microscopy. Our bioreactor offers a reliable and user-friendly solution for researchers seeking to create artificial tissues with a perfusable microchannel network.