Local densification and fibrillogenesis of collagen
Sound can be leveraged to change the micro- and macromolecular structure of collagen hydrogels
Fibrillogenesis and collagen gelation is not hampered by sound
Collagen fibrils can be visualised with standard immunofluorescent microscopy
Control over cellular and extracellular organisation at high spatial resolution is paramount to investigate cell-material interactions in in vitro models of various diseases such as fibrosis. Acoustic manipulation at low frequency (<100 Hz) can be used to sculpture collagen into substrates that mimic the gradual mapping of fibrillar collagen matrices. Specifically, hydrodynamic pressure, induced by Faraday waves at the air-liquid interface, enables local densification of fibrillar collagen proteins. The technology's appeal is down to its remote, non-destructive nature, that allows for extracellular matrix sculpturing at the micro- and macro scale. Different to ultrasound used to pattern collagen1, acoustic manipulation at low frequency does not induce local heating and does thereby not alter collagen gelation kinetics. Gradients in collagen density and stiffness can be created and will allow investigating the response of various cell types to anisotropic collagen materials.
mimiX labware (small frames) were glued onto glass coverslips, allowing for subsequent microscopy. A solution of Rattail collagen type 1 was casted into the frames and stimulated for 30 minutes until gelation. Collagen hydrogels were stained with anti collagen antibodies and imaged on a confocal microscope.
A) In response to the applied frequency and acceleration, heterogeneous hydrogel structures were formed with areas of aggregated collagen fibrils. B) Without stimulation collagen fibrils were homogeneously distributed. A’) At higher magnification, clusters of individual fibres were observed in patterned samples compared to the control (B’).
Hydrodynamic forces, induced by sound, have an effect on the architectural structure of collagen hydrogels which has yet to be elucidated and understood. In distinct regions, collagen fibrils aligned along a common orientation (white arrow). Images i to iv were acquired on the same sample at different spots, indicating the spatially defined collagen organisation.
Biomaterial: Collagen Type 1, rat tail. Cell Type: N.A.
Labware: mimiX Labware for small petri dishes or glass slides
(1) Norris et al., Acoustic modification of collagen hydrogels facilitates cellular remodeling, Materials Today Bio, 2019.
(2) Garvin et al., Controlling collagen fiber microstructure in three-dimensional hydrogels using ultrasound, J. Acoust. Soc. Am., 2013.