Noninvasive mechanical profiling of breast cancer cells-laden 3D hydrogels using dynamic optical coherence tomography

Dynamic optical coherence tomography (D-OCT) offers a non-contact and non-destructive approach for mechanical characterization of cancer tissues with a high spatial and temporal resolution. Accurate quantification of cancer tissue mechanics is crucial for understanding the progression of tumors. Yet, conventional mechanical characterization methods, including in-contact nanoindentation, atomic force microscopy (AFM), and rheometry, often lack spatial detail and are unsuitable for real-time evaluations. In this study, we aim to establish a quantitative relationship between D-OCT- derived speckle dynamics and stiffness measurements of 3D hydrogels laden with breast cancer cells. Cylindrical phantoms of ~ 6.5 mm radius and ~ 5 mm height were fabricated using low-melting-point (LMP) agarose at two different concentrations (1 % and 5 % w/v), depicting soft and stiff biological tissues, respectively, both with and without encapsulated polystyrene microparticles and breast cancer cells. A spectral domain OCT system captured rapid speckle fluctuations, followed by uniaxial compression using a Mach-1 v500cs testing system. Speckle data were converted into autocorrelation curves, which we fit to exponential decays to extract each phantom’s decorrelation time. Plotting decorrelation time against Young’s modulus revealed an exponential correlation (R2 ≈ 0.81), demonstrating the feasibility of D-OCT for spatially resolved, real-time stiffness mapping. This work provides initial validation of the technique and lays the foundation for future studies incorporating hydrogels with tunable stiffness, multiple cancer cell lines, varied loading conditions, and machine learning models to translate OCT signals into quantitative mechanical property maps.