Determining the optimal transplantation window in hepatic organoids via real-time biosensing of vascularization and metabolic maturation utilizing the integrated organoid-on-a-chip platform.

Hepatic organoid transplantation is hypothesized to achieve maximal therapeutic benefit when vascular integration coincides with peak metabolic function. However, conventional endpoint-based evaluation methods cannot dynamically track these processes in real time, limiting precise determination of the optimal transplantation window. To address this challenge, we developed a biosensor-integrated organoid-on-a-chip. This platform enables simultaneous, real-time monitoring of vascularization through nitric oxide (NO) and hepatic metabolic function through urea. Under controlled flow conditions, the biosensor-integrated organoid-on-a-chip revealed that flow-induced mechanostimulation synchronizes endothelial and hepatocyte maturation. The biosensors integrated chip further identified a critical day-5 inflection point, corresponding to maximal biomarker levels and defining the optimal transplantation window. Transplantation at this window restored approximately 93 % of liver function and lobular architecture in cirrhotic mice, whereas grafts transplanted before or after this window showed 50-70 % lower therapeutic efficacy. These findings validate the transplantation window hypothesis and provide a real-time, quantitative framework for quality control in organoid-based regenerative therapies.