Microsphere sensors for characterizing stress fields within three-dimensional extracellular matrix

Compressible Hollow Microlasers in Organoids for High-Throughput and Real-Time Mechanical Screening

Mechanical stress within organoids is a pivotal indicator in disease modeling and pharmacokinetics, yet current tools lack the ability to rapidly and dynamically screen these mechanics. Here, we introduce biocompatible and compressible hollow microlasers that realize all-optical assessment of cellular stress within organoids. The laser spectroscopy yields identification of cellular deformation at the nanometer scale, corresponding to tens of pascals stress sensitivity. The compressibility enables the investigation of the isotropic component, which is the fundamental mechanics of multicellular models. By integrating with a microwell array, we demonstrate the high-throughput screening of mechanical cues in tumoroids, establishing a platform for mechano-responsive drug screening. Furthermore, we showcase the monitoring and mapping of dynamic contractile stress within human embryonic stem cell-derived cardiac organoids, revealing the internal mechanical inhomogeneity within a single organoid. This method eliminates time-consuming scanning and sample damage, providing insights into organoid mechanobiology.

Exploration of Curvature and Stiffness Dual-Regulated Breast Cancer Cell Motility by a Motor-Clutch Model and Cell Traction Force Characterization

The migration of breast cancer cells is the main cause of death and significantly regulated by physical factors of the extracellular matrix (ECM). To be specific, the curvature and stiffness of the ECM were discovered to effectively guide cell migration in velocity and direction. However, it is not clear what the extent of effect is when these dual-physical factors regulate cell migration. Moreover, the mechanobiology mechanism of breast cancer cell migration in the molecular level and analysis of cell traction force (CTF) are also important, but there is a lack of systematic investigation. Therefore, we employed a microfluidic platform to construct hydrogel microspheres with an independently adjustable curvature and stiffness as a three-dimensional substrate for breast cancer cell migration. We found that the cell migration velocity was negatively correlated to curvature and positively correlated to stiffness. In addition, curvature was investigated to influence the focal adhesion expression as well as the assignment of F-actin at the molecular level. Further, with the help of a motor-clutch mathematical model and hydrogel microsphere stress sensors, it was concluded that cells perceived physical factors (curvature and stiffness) to cause changes in CTF, which ultimately regulated cell motility. In summary, we employed a theoretical model (motor-clutch) and experimental strategy (stress sensors) to understand the mechanism of curvature and stiffness regulating breast cancer cell motility. These results provide evidence of force driven cancer cell migration by ECM physical factors and explain the mechanism from the perspective of mechanobiology.

Quantitative characterization of tumor cell traction force on extracellular matrix by hydrogel microsphere stress sensor

Cell traction force (CTF) is a kind of active force that is a cell senses external environment and actively applies to the contact matrix which is currently a representative stress in cell-extracellular matrix (ECM) interaction. Studying the distribution and variation of CTF during cell-ECM interaction help to explain the impact of physical factors on cell behaviors from the perspective of mechanobiology. However, most of the strategies of characterizing CTF are still limited by the measurement needs in three-dimensional (3D), quantitative characteristics and in vivo condition. Microsphere stress sensor (MSS) as a new type of technology is capable of realizing the quantitative characterization of CTF in 3D and in vivo. Herein, we employed microfluidic platform to design and fabricate MSS which possesses adjustable fluorescent performances, physical properties, and size ranges for better applicable to different cells (3T3, A549). Focusing on the common tumor cells behaviors (adhesion, spreading, and migration) in the process of metastasis, we chose SH-SY5Y as the representative research object in this work. We calculated CTF with the profile and distribution to demonstrate that the normal and shear stress can determined different cell behaviors. Additionally, CTF can also regulate cell adhesion, spreading, and migration in different cell states. Based on this method, the quantitative characterization of CFT of health and disease cells can be achieved, which further help to study and explore the potential mechanism of cell-ECM interaction.

From cells to form: A roadmap to study shape emergence in vivo

Organogenesis arises from the collective arrangement of cells into progressively 3D-shaped tissue. The acquisition of a correctly shaped organ is then the result of a complex interplay between molecular cues, responsible for differentiation and patterning, and the mechanical properties of the system, which generate the necessary forces that drive correct shape emergence. Nowadays, technological advances in the fields of microscopy, molecular biology, and computer science are making it possible to see and record such complex interactions in incredible, unforeseen detail within the global context of the developing embryo. A quantitative and interdisciplinary perspective of developmental biology becomes then necessary for a comprehensive understanding of morphogenesis. Here, we provide a roadmap to quantify the events that lead to morphogenesis from imaging to image analysis, quantification, and modeling, focusing on the discrete cellular and tissue shape changes, as well as their mechanical properties.