3D bioprinting and label-free imaging: Bridging innovations for organoid research

Organoids are three-dimensional (3D) and multicellular structures that more closely mimic the architecture and functions of human organs. These in vitro systems are derived from pluripotent stem cells, tissue-resident stem cells, or organ-specific progenitors. Despite their potential, conventional organoid development methods are limited by inconsistencies in formation and the absence of complete microenvironmental cues, which reduces reproducibility in larger organ models. In contrast, 3D bioprinting techniques offer a precise layer-by-layer construction approach that enables superior spatial control, scalability, and uniformity in organoid formation. This advantage makes organoids with 3D bioprinting invaluable in diversified fields such as cell biology, pathology, drug toxicology, and molecular medicine. To track the dynamic processes of cell growth, differentiation, and organization during organoid development and maturation, advanced imaging technologies are crucial. Traditional optical imaging methods, however, require exogenous labeling agents to enhance contrast, which can damage samples through photobleaching and phototoxicity. Label-free and real-time imaging modalities, by contrast, offer non-invasive and non-destructive monitoring of organoids, preserving sample integrity and enabling longitudinal studies. This review highlights the benefits of bioprinting technologies in overcoming current limitations in organoid development and provides a comprehensive overview of label-free and real-time imaging technologies for organoids. We examine the principles, strengths, applications, and limitations of these imaging methods, offering insights into their potential to drive further innovations in the rapidly evolving field of organoid imaging.