by Keyword: Elastic modulu
Munoz-Galan, Helena, Marzoa, Antonio, Bertran, Oscar, Barbera, Francesc, Jimenez-Pique, Emilio, Ahumada, Oscar, Perez-Madrigal, Maria M, Aleman, Carlos, (2024). Optomechanical, Computer Simulation, and Nanoindentation Studies on Tunable Click Hydrogels: Microscopic Insights Acs Applied Polymer Materials 6, 12176-12185
The properties of thiol-yne click polyethylene glycol (PEG)-based hydrogels, which can be tuned by controlling the cis and trans stereochemistry through the gelation conditions, have been investigated at the micro- and nanoscale using optomechanics, atomistic molecular dynamics (MD) simulations, and nanoindentation. Optomechanical measurements on thin films and computer MD simulations have shown that the trans hydrogel is less porous than the cis hydrogel, which is in agreement with both the swelling behavior and the pore size determined for macroscopic 3D hydrogel samples. On the other hand, results from optomechanical measurements using both static and dynamic modes, as well as nanoindentation profiles obtained for thin films adhered to glass substrates, reflect that the trans hydrogel is stiffer than the cis one. Overall, despite the few drawbacks of the techniques employed in this work, from a qualitative point of view, the properties of click PEG-based hydrogels at the micro- and nanoscale follow a behavior similar to that found for 3D macroscopic samples. Considering the wide range of mechanical properties of human tissues (e.g., Young's modulus ranges from 0.1 kPa to many tens of MPa) and the extensive use of hydrogels in applications such as tissue regeneration and tissue-specific drug delivery, the availability of a hydrogel with tunable properties opens the door to targeted biomedicine.
JTD Keywords: Algorithm, Elastic modulu, Ewal, Injectable hydrogels, Molecular dynamics, Molecular-dynamics, Nanoindentation, Optomechanical sensors, Polyethylene glycol hydrogels, Surface stress, Thiol-yneclick hydrogels
Karkali, K, Jorba, I, Navajas, D, Martin-Blanco, E, (2022). Measuring ventral nerve cord stiffness in live flat- dissected Drosophila embryos by atomic force microscopy Star Protocols 3, 101901 
Drosophila is an amenable system for addressing the mechanics of morphogenesis. We describe a workflow for characterizing the mechanical properties of its ventral nerve cord (VNC), at different developmental stages, in live, flat dissected embryos employing atomic force microscopy (AFM). AFM is performed with spherical probes, and stiffness (Young's modulus) is calculated by fitting force curves with Hertz's contact model. For complete details on the use and execution of this protocol, please refer to Karkali et al. (2022).
JTD Keywords: atomic force microscopy (afm), developmental biology, model organisms, Animals, Atomic force microscopy, Atomic force microscopy (afm), Biology, Developmental biology, Drosophila, Elastic modulus, Microscopy, atomic force, Model organisms, Morphogenesis, Neurociencia, Neuroscience
Otero, J., Navajas, D., Alcaraz, J., (2020). Characterization of the elastic properties of extracellular matrix models by atomic force microscopy 
Methods in Cell Biology (ed. Caballero, David, Kundu, Subhas C., Reis, Rui L.), Academic Press (Cambridge, USA) 156, 59-83
Tissue elasticity is a critical regulator of cell behavior in normal and diseased conditions like fibrosis and cancer. Since the extracellular matrix (ECM) is a major regulator of tissue elasticity and function, several ECM-based models have emerged in the last decades, including in vitro endogenous ECM, decellularized tissue ECM and ECM hydrogels. The development of such models has urged the need to quantify their elastic properties particularly at the nanometer scale, which is the relevant length scale for cell-ECM interactions. For this purpose, the versatility of atomic force microscopy (AFM) to quantify the nanomechanical properties of soft biomaterials like ECM models has emerged as a very suitable technique. In this chapter we provide a detailed protocol on how to assess the Young's elastic modulus of ECM models by AFM, discuss some of the critical issues, and provide troubleshooting guidelines as well as illustrative examples of AFM measurements, particularly in the context of cancer.
JTD Keywords: 3D ECM hydrogels, Atomic force microscopy, Decellularized tissue, Elastic modulus, Endogenous ECM, Extracellular matrix
Alcaraz, J., Otero, J., Jorba, I., Navajas, D., (2018). Bidirectional mechanobiology between cells and their local extracellular matrix probed by atomic force microscopy Seminars in Cell and Developmental Biology 73, 71-81
There is growing recognition that the mechanical interactions between cells and their local extracellular matrix (ECM) are central regulators of tissue development, homeostasis, repair and disease progression. The unique ability of atomic force microscopy (AFM) to probe quantitatively mechanical properties and forces at the nanometer or micrometer scales in all kinds of biological samples has been instrumental in the recent advances in cell and tissue mechanics. In this review we illustrate how AFM has provided important insights on our current understanding of the mechanobiology of cells, ECM and cell-ECM bidirectional interactions, particularly in the context of soft acinar tissues like the mammary gland or pulmonary tissue. AFM measurements have revealed that intrinsic cell micromechanics is cell-type specific, and have underscored the prominent role of β1 integrin/FAK(Y397) signaling and the actomyosin cytoskeleton in the mechanoresponses of both parenchymal and stromal cells. Moreover AFM has unveiled that the micromechanics of the ECM obtained by tissue decellularization is unique for each anatomical compartment, which may support both its specific function and cell differentiation. AFM has also enabled identifying critical mechanoregulatory proteins involved in branching morphogenesis (MMP14) and acinar differentiation (α3β1 integrin), and has clarified the role of altered tissue mechanics and architecture in a variety of pathologic conditions. Critical technical issues of AFM mechanical measurements like tip geometry effects are also discussed.
JTD Keywords: Atomic force microscopy, Beta1 integrin, Elastic modulus, Extracellular matrix, Morphogenesis, Tissue decellularization
Giménez, A., Uriarte, J. J., Vieyra, J., Navajas, D., Alcaraz, J., (2017). Elastic properties of hydrogels and decellularized tissue sections used in mechanobiology studies probed by atomic force microscopy Microscopy Research and Technique , 80, (1), 85-96
The increasing recognition that tissue elasticity is an important regulator of cell behavior in normal and pathologic conditions such as fibrosis and cancer has driven the development of cell culture substrata with tunable elasticity. Such development has urged the need to quantify the elastic properties of these cell culture substrata particularly at the nanometer scale, since this is the relevant length scale involved in cell-extracellular matrix (ECM) mechanical interactions. To address this need, we have exploited the versatility of atomic force microscopy to quantify the elastic properties of a variety of cell culture substrata used in mechanobiology studies, including floating collagen gels, ECM-coated polyacrylamide gels, and decellularized tissue sections. In this review we summarize major findings in this field from our group within the context of the state-of-the-art in the field, and provide a critical discussion on the applicability and complementarity of currently available cell culture assays with tunable elasticity. In addition, we briefly describe how the limitations of these assays provide opportunities for future research, which is expected to continue expanding our understanding of the mechanobiological aspects that support both normal and diseased conditions.
JTD Keywords: 3D culture, Atomic force microscopy, Elastic modulus, Extracellular matrix, Polyacrylamide
