Stretch-dependent changes in molecular conformation in fibronectin nanofibers

Area of Science:

• Biomaterials Science
• Cell Biology
• Nanotechnology

Background:

• Fibronectin (FN) is a crucial extracellular matrix (ECM) glycoprotein involved in development, healing, and fibrosis.
• FN is mechanosensitive, undergoing conformational changes upon force application, but its nanostructural response to extension is difficult to study.
• Understanding FN matrix mechanobiology and cell-ECM signaling is limited by challenges in observing FN nanostructure dynamics.

Purpose of the Study:

• To develop a method for engineering and stretching FN nanofibers to study force-induced nanostructural changes.
• To analyze the morphological alterations of FN molecules within stretched nanofibers using high-resolution AFM.
• To gain insights into the relationship between FN fiber extension and constituent molecule morphology.

Main Methods:

• Engineered FN nanofibers using a modified surface-initiated assembly (SIA) technique.
• Uniaxially stretched immobilized FN nanofibers to over 7-fold extensions.
• Utilized high-resolution atomic force microscopy (AFM) to image the nanostructure of stretched FN nanofibers.

Main Results:

• Observed distinct nanostructures in FN nanofibers at different extension levels.
• Fully contracted fibers showed large, isotropic nodules; intermediate extension revealed aligned fibrils and smaller nodules.
• Highly extended fibers displayed aligned fibrils with small nodules in a beads-on-a-string arrangement.

Conclusions:

• Established a novel methodology to uniaxially stretch FN fibers and analyze nanostructural changes via AFM.
• Demonstrated that FN fiber extension significantly alters the morphology of individual FN molecules.
• Provided new insights into FN matrix mechanobiology and the structural basis of force-induced FN remodeling.