Development of an optical tweezers-based assay for ECM viscoelastic characterization in decellularized MSC spheroids

Abstract

The extracellular matrix (ECM) plays a central role in tissue structure, mechanics, and cell behavior, yet its mechanical properties are difficult to isolate and quantify in three-dimensional biological systems. In this project, we develop an assay that combines optical tweezers and microfluidics to characterize the viscoelastic properties of ECM in decellularized mesenchymal stromal cell (MSC) derived spheroids. 

MSC spheroids are first grown under controlled conditions and then decellularized to remove cellular components while preserving the ECM architecture. Micron-sized beads are introduced into the spheroids using a custom microfluidic delivery system designed to minimize structural disruption. These beads are subsequently trapped using optical tweezers, allowing precise manipulation and measurement of their motion within the ECM. Trap stiffness is carefully calibrated using established physical methods to ensure reliable force measurements. 

By analyzing the thermal fluctuations and controlled responses of trapped beads, we aim to extract frequency-dependent viscoelastic parameters that describe how the ECM stores and dissipates mechanical energy. This microrheological approach enables mechanical characterization at length scales relevant to cellular processes, which are inaccessible using conventional bulk testing methods. 

This poster will present the assay design, experimental workflow, and validation steps, along with preliminary results demonstrating system performance. Ultimately, this technique provides a platform for mapping ECM mechanical properties in engineered tissues and comparing them to native human tissue, offering valuable insight for regenerative medicine and biomaterial design.