Brillouin Microscopy of Breast tumor Spheroids On‐a‐Chip: Mechanical and Transcriptional Responses to Microfluidic‐Induced Rapid Deformations

Abstract Pioneering a novel integrated photonic platform, Brillouin–Raman Microspectroscopy on‐a‐Chip is presented, which enables real‐time, high resolution analysis of mechano‐chemical dynamics in complex 3D biological systems under controlled deformation. This contact‐free, all‐optical method seamlessly combines Brillouin and Raman microscopy within microfluidic devices, providing a unique correlative approach to overcome current limitations in probing cellular mechanics and biochemical responses in live multicellular models. This innovative platform, when applied to breast tumor spheroids, revealed that rapid, cyclical mechanical deformations, mimicking in vivo stresses, profoundly impacts tumor physiology. These findings demonstrate that controlled deformations trigger rapid nuclear shape changes and robust transcriptional reprogramming, marked by a significant (48‐fold) upregulation of the early stress response regulator ATF3. These responses are accompanied by global spheroid stiffening, as precisely quantified by Brillouin spectroscopy. Remarkably, repeated deformation imprints a form of mechanical memory in these collective systems, which culminates in enhanced collagen invasion over 24 h. The label‐free methodology sets a new benchmark in biophotonics, unlocking a new class of experiments to probe and modulate physiological and pathological processes with transformative potential for cancer research, broader mechanobiology, and the study of mechanical memory in organoids and other complex 3D models.