title: Investigation of Biological and Technical Components for the Development of a 3D-Bioprinting Process for Vascularized Organs-on-a-Chip
Creators: name: Moritz-Fritschen, Anna
Publisher: name: UNSPECIFIED
Year: 2024

description: In today’s pharmaceutical research, conventional cell culture and animal testing are used to quantify the efficacy and safety of new pharmaceutical substances and drugs. The popularity of two-dimensional cell culture systems is based on their low costs in production and maintenance, high scalability, well-established testing and automated analysis methods. Despite these advantages, these methods often misjudge substances, resulting in late failures later on in human studies due to undetected side effects or reduced efficacy. In order to prevent these costly late failures, it is necessary to develop tissue models that more accurately and reliably represent human tissues in research. Such models require the targeted placement of multiple cell types in a matrix material that is similar to the human body, which can best be realized using high-resolution additive manufacturing such as microvalve-based 3D-bioprinting. To ensure nutrient supply and to mimic both the native nutrient and drug uptake, the integration of a blood vessel network into the tissue model is essential. The perfusion of these vascular networks can most reliably be realized on a microfluidic chip, which regulates liquid flow and drug administration. When tissue models are cultured under perfusion on such a microfluidic chip, they are called Organs-on-a-Chip. Despite the advantages of Organs-on-a-Chip over two-dimensional cell cultures, their use in pharmaceutical research remains limited as aspects such as their scaled-up fabrication and automatization in handling remain challenging.
This work addresses the mentioned research aspects required for the automated fabrication of vascularized Organs-on-a-Chip for a translation of these models into preclinical pharmaceutical research. It focuses on the fabrication of a three-dimensional, vascularized and multicellular liver carcinoma Organ-on-a-Chip model via microvalve-based 3D-bioprinting. The objective is to determine if 3D-bioprinting can enhance automation in the fabrication of Organs-on-a-Chip and add a higher level of complexity as well as biomimetic vascular structures. In the first step, approaches to vascularization in Organs-on-a-Chip presented in the literature are reviewed, classified according to their degree of biomimicry and assessed for their suitability regarding the planned multi-cellular Organ-on-a-Chip. Based on this analysis, an approach compatible with the available bioprinting system and suitable for the envisioned tissue model is selected and employed in this work. Since the development of complex tissue models often requires multiple iterative steps concerning the microfluidic chip, conventional 3D-printing could enhance and accelerate the prototyping of these chips. Possible adaptations to the print process and a material selection of a conventional 3D-printer required to obtain transparent and cytocompatible components are therefore studied. This adapted process is then tested to examine if the print resolution as well as the general print process is capable of prototyping various microfluidic chip designs required for the tissue model and bioprint process. Next, a matrix material has to be selected that contains the liver carcinoma cells and that can be placed by the bioprinter with high precision and in small volumes. For this purpose, different hydrogel combinations are studied to identify a material that can retain and stimulate cell viability and growth without compromising the print resolution within the microfluidic chip. In the final step, the bioprinter is combined with a robotic handling unit to replace manual handling in the assembly of the Organ-on-a-Chip. This process is tested and assessed on the multi-cellular and vascularized liver carcinoma Organ-on-a-Chip. The resulting model is evaluated by the print resolution, the morphology of the vascular network and the proliferation of the liver carcinoma cells over a culture time of 14 days.