Christina Stelzl: Applications of Additive Manufacturing for Advancing Cell Models from 2D to 3D

Abstract

Two-dimensional (2D) cell culture systems are widely used in preclinical research due to their ease of handling and standardisation, but do not adequately reflect key aspects of the complex three-dimensional (3D) physiological microenvironment. This limits the predictive value of in vitro studies for both drug development and biomaterials research. The overall aim of this thesis was to explore how additive manufacturing supports the transition from 2D to more advanced 3D cell culture models.

In Study I, CombiCTx, a cell culture device for combinatorial anti-cancer drug testing, was developed. The system enables the formation of overlapping drug gradients through diffusion in a hydrogel matrix, and an assay and imaging analysis protocol was established. Using breast cancer cells, it was demonstrated that the assay can identify synergistic drug effects and that, for the drugs tested, these effects were spatially confined to specific regions of the assay space, highlighting the importance of diffusion processes not captured in standard 2D assays.

In Study II, an open source extrusion-based bioprinter based on the E3D motion system was established to increase accessibility to bioprinting technologies. The system supports multimaterial printing and FRESH bioprinting. Collagen scaffolds and cell-laden laminin-containing constructs were printed, and high cell viability was maintained, demonstrating the suitability of the platform for generating 3D cell culture environments.

Studies III and IV focused on biomaterials for bone regeneration. In Study III, the biosafety of a phosphoserine (pSER)-modified calcium phosphate bone adhesive was evaluated. Both in vitro and in vivo results indicated good biocompatibility, with no evidence of adverse immune reactions or ectopic bone formation.

In Study IV, 3D bioprinted collagen-silica hybrid scaffolds modified with pSER were investigated. In vitro experiments showed a dose-dependent effect of pSER in combination with calcium phosphate on cell viability. In vivo, mineralised scaffolds promoted bone formation, suggesting an osteogenic potential of these materials.

In conclusion, the studies presented in this thesis demonstrate that additive manufacturing can be used to develop more advanced in vitro models and to investigate biomaterials in controlled 3D environments. These approaches will contribute to improving the translation of preclinical findings into clinical applications.