Immersion bioprinting of hyaluronan and collagen bioink-supported 3D patient-derived brain tumor organoids

Organoids, and in particular patient-derived organoids, have emerged as crucial tools for cancer research. Our organoid platform, which has supported patient-derived tumor organoids (PTOs) from a variety of tumor types, has been based on the use of hyaluronic acid (HA) and collagen, or gelatin, hydrogel bioinks. One hurdle to high throughput PTO biofabrication is that as high-throughput multi-well plates, bioprinted volumes have increased risk of contacting the sides of wells. When this happens, surface tension causes bioinks to fall flat, resulting in 2D cultures. To address this problem, we developed an organoid immersion bioprinting method-inspired by the FRESH printing method-in which organoids are bioprinted into support baths in well plates. The bath-in this case an HA solution-shields organoids from the well walls, preventing deformation. Here we describe an improvement to our approach, based on rheological assessment of previous gelatin baths versus newer HA support baths, combined with morphological assessment of immersion bioprinted organoids. HA print baths enabled more consistent organoid volumes and geometries. We optimized the printing parameters of this approach using a cell line. Finally, we deployed our optimized immersion bioprinting approach into a drug screening application, using PTOs derived from glioma biospecimens, and a lung adenocarcinoma brain metastasis. In these studies, we showed a general dose dependent response to an experimental p53 activator compound and temozolomide (TMZ), the drug most commonly given to brain tumor patients. Responses to the p53 activator compound were effective across all PTO sets, while TMZ responses were observed, but less pronounced, potentially explained by genetic and epigenetic states of the originating tumors. The studies presented herein showcase a bioprinting methodology that we hope can be used in increased throughput settings to help automate biofabrication of PTOs for drug development-based screening studies and precision medicine applications.