Characterizing the extrusion bioprinting process and microalgal photosynthetic efficiency in bioprinted constructs during parabolic flights

Extrusion-based bioprinting is a promising technology for in-space biofabrication, yet peer-reviewed process data derived in real microgravity remain rare. In the presented study, we used parabolic flights as a platform to characterize extrusion-based bioprinting of an alginate-methylcellulose bioink in short-term microgravity. Layer-by-layer printing was performed successfully at different layer distances (260–610 µm), and unsupported filament bridges of up to 13 cm were successfully printed under microgravity. We performed what is, to our knowledge, the first “green” bioprinting of microalgae-laden hydrogels under microgravity, with the cell viability of the thereby created samples exceeding 99% for Scenedesmus sp. and reaching 97% for Chlorella vulgaris on day 7 post-printing. Real-time pulse-amplitude modulated (PAM) fluorometry showed that the effective quantum yield of photosystem II remained stable across all gravitational phases in both liquid cultures and bioprinted samples while maintaining species-specific differences in non-photochemical quenching between the two species. The results of the study indicate that extrusion-based green bioprinting is functionally achievable under short-term microgravity conditions and that cultivation of the thereby created photosynthetically active structures is possible without loss of photosynthetic performance.