3D-printed microfluidic chip for modeling retinal organoid–endothelial co-culture

Pathological angiogenesis, such as that observed in wet age-related macular degeneration (AMD), is challenging to reproduce in vitro. While previous organ-on-chip approaches have incorporated retinal pigment epithelium (RPE) and endothelial barriers, models integrating human retinal organoids with vascular networks remain limited. Here, we report the development of a fully 3D-printed microfluidic device for co-culture of human induced pluripotent stem cell (hiPSC)-derived retinal organoids containing RPE regions with endothelial cells. The device, fabricated from flexible thermoplastic polyurethane (TPU) on a transparent polyvinyl chloride (PVC) substrate, enables direct organoid–endothelial interaction within a fibrin–Matrigel matrix without physical barriers. In this system, endothelial cells formed choroid-like networks that integrated with retinal organoids. Vascular network density and invasion into RPE regions were enhanced by VEGF stimulation, recapitulating features of wet AMD. Furthermore, fluorescent liposomes distributed along endothelial structures and accumulated at the organoid interface, supporting the application of this model for nanoparticle delivery studies. This 3D-printed retinal organoid-on-chip provides a simple, reproducible, and physiologically relevant platform that complements existing retinal models for investigating angiogenesis and evaluating therapeutic strategies.