Robotics-driven manufacturing of cartilaginous microtissues for the bio-assembly of skeletal implants

Automated technologies are attractive for enhancing a robust manufacturing of tissue engineered products for clinical translation. In this work, we present an automation strategy using a robotics platform for media changes of cartilaginous microtissues cultured in static microwell platforms. We use an automated image analysis pipeline to extract microtissue displacements and morphological features, which serve as input for statistical factor analysis. To minimize microtissue displacement and suspension leading to uncontrolled fusion, we performed a mixed factorial DoE on liquid handling parameters for large and small microwell platforms. As a result, 144 images, with 51 471 spheroids could be processed automatically. The automated imaging workflow takes 2 minutes per image, and it can be implemented for on-line monitoring of microtissues, thus allowing informed decision making during manufacturing. We found that time in culture is the main factor for microtissue displacements, explaining 10 % of the displacements. Aspiration and dispension speed were not significant at manual speeds or beyond, with an effect size of 1 %. We defined optimal needle placement and depth for automated media changes and we suggest that robotic plate handling could improve the yield and homogeneity in size of microtissue cultures. After three weeks culture, increased expression of COL2A1 confirmed chondrogenic differentiation and RUNX2 shows no osteogenic specification. Histological analysis showed the secretion of cartilaginous extracellular matrix. Furthermore, microtissue-based implants were capable of forming mineralized tissues and bone after four weeks of ectopic implantation in nude mice. We demonstrate the development of an integrated bioprocess for culturing and manipulation of cartilaginous microtissues. We anticipate the progressive substitution of manual operations with automated solutions for manufacturing of microtissue-based living implants. ### Competing Interest Statement At the time this research was conducted, GNH and AP were affiliated with KU Leuven. They are now affiliated with AstraZeneca and IQVIA Biotech respectively.