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.