Imaging and Characterization of 3D-Bioprinted Stem Cell Constructs: From Nanoscale Analysis to Functional Assessment

Clinical translation of 3D-bioprinted stem cell constructs requires standardized characterization across length scales and biological domains. This review critically evaluates imaging and analytical methods along the construct lifecycle: bioink rheology and printability, structural imaging by micro-computed tomography and optical coherence tomography, cellular analysis by confocal, light-sheet, and multiphoton microscopy, chemical mapping by vibrational spectroscopy and mass spectrometry imaging, and bulk and nanoscale mechanical testing. Beyond cataloging techniques, we propose a decision-oriented framework that maps critical quality attributes to workflow stages, distinguishes essential from optional measurements, defines a nondestructive-to-destructive testing sequence, delineates the operational limits of each method in opaque, thick, and cell-dense constructs, and separates established tools from emerging approaches such as machine learning-based quality prediction and digital twins. Finally, we outline the remaining needs for reference materials, standardized protocols, and recently updated regulatory pathways.