The following article originally appeared on January 26, 2022 in Biocompare here.
Organoids are complex three-dimensional (3D) cell cultures that mimic structural and functional properties of organs of interest. They are used to investigate organ development, model disease, and develop personalized medicines, making them powerful tools for scientific research. A major challenge when working with organoids is ensuring the extracellular matrix (ECM) material used for culturing them is handled correctly. This article comments on the value of ECM-based hydrogels such as Corning® Matrigel® to organoid culture before explaining how ECM droplet-based assays and scale up can be standardized using a bioprinter.
Organoids are Essential Research Tools
Organoids support a broad range of research activities by acting as model systems that mimic key features of specific organs. They can be generated from adult stem cells present in tissue samples, or via directed differentiation of pluripotent stem cells, with cellular expansion in culture yielding thousands of individual organoids within just a few weeks. Applications of organoids include disease modeling using patient-derived cells such as those extracted from a tumor; evaluating drug efficacy and toxicity; and investigating the effects of different mutations on a disease state using CRISPR for gene editing. To date, organoids have been produced for tissues including intestine, lung, liver, kidney, pancreas, retina, heart, and brain.
Organoid Culture Presents Unique Challenges
Generating organoids begins with stem cell culture in an appropriate ECM material, with Corning Matrigel (a solubilized basement membrane preparation) being the most widely used. Methods vary, but include Matrigel coating the wells of a microplate then seeding the cells (in an appropriate growth medium) on top; mixing Matrigel and cells together before dispensing into plates (then adding growth medium); and dispensing a Matrigel/cell mixture as small dome-shaped droplets on the microplate surface before submersing the domes in growth medium. Of these, the latter approach is often utilized since it ensures each cell receives sufficient oxygen and nutrients to maximize the number of viable organoids produced. However, this method is the most technically challenging, requiring both time and skill.
The main hurdle that must be overcome during the droplet-based approach arises from the fact that Matrigel only exists as a liquid when cold; as soon as Matrigel contacts a warm (room temperature) surface, it begins to polymerize. To produce domes, researchers must therefore ensure that both Matrigel and pipette tips are kept cold while the microplate remains warm to avoid losing precious sample material. Additionally, it takes practice to ensure the domes have an upright structure; because the viscosity of Matrigel requires that pressure be applied for extrusion, researchers must be careful to avoid over-dispensing or allowing Matrigel to contact the well edges since this can lead to domes spreading or blending into one another. The complicated, manual nature of this process restricts throughput and inevitably results in user-to-user variability that can be exacerbated by fluctuating environmental conditions within the lab. Further difficulties arise when different organoids will be combined in the same well (which can necessitate dispensing different-sized droplets), which limits the development of more complex models.
Automated Dispensing Improves Experimental Reproducibility
Automation offers many benefits to scientific research, including improved experimental consistency, less chance of cross-contamination, decreased risk of exposure to potentially harmful material, and higher throughput. It also helps to avoid repetitive strain injury and frees up researchers’ time to be spent on other tasks. Critically, for organoid culture, automation promises to maximize the value gained from patient sample material by providing highly reproducible Matrigel dome formation —equating to more reliable results.
Until now, a bioprinter able to handle Matrigel has not been available. However, with the launch of the Corning Matribot® Bioprinter, it is now possible to perform organoid studies without the need for laborious, largely manual workflows. Notably, the Matribot minimizes the use of ice buckets to prevent gelation of Matrigel. To use the Matribot Bioprinter, researchers simply load the Matrigel/cell mixture into a syringe and place the microplate on a warmed print bed; the system then carries out droplet dispensing (or more advanced printing) according to user-defined parameters, ensuring consistent Matrigel dome formation through tight temperature control and precise dispensing. The small footprint of the Matribot Bioprinter enables placement within a biological safety cabinet—an essential consideration when working with patient-derived sample material.