A 3D-Bioprinted Artificial Coral Platform for Investigating Structural Effects on Microalgal Photophysiology

Coral skeletal morphology and optical properties play critical roles in regulating light distribution to symbiotic dinoflagellates and shaping their growth and photosynthetic performance. However, existing experimental approaches lack precise control over skeletal microgeometry and optical scattering, limiting comprehensive studies of coral photophysiology. Here, we present a 3D bioprinted artificial coral platform integrating engineered hydrogel-based tissue with tunable skeletal structures to investigate coral-algal light interactions. Diffusion-optimized hyaluronic acid glycidyl methacrylate (HAGM) hydrogels supported robust growth and photosynthesis of encapsulated dinoflagellates. Using natural coral skeletons from shallow and mesophotic environments, we demonstrate that algal growth within the HAGM tissue layer is regulated by the underlying skeletal morphology. We further fabricated artificial coral skeletons with fine-scale corallite geometries by incorporating cellulose nanocrystals to enhance light scattering. Evaluation under varying light intensities revealed photosynthetic performance trends consistent with those observed under natural conditions. This platform provides a controllable in vitro model for studying coral-algal photophysiology.