The optimization of cell-substrate and cell-cell interactions is of great importance for tissue engineering and biomedical applications such as tissue repair and wound healing. These could be greatly improved using extracellular matrices that accurately mimic the in vivo tissue microenvironment and modulate cell behavior. Biomaterials exhibiting a gradient of mechanical properties can regulate cell activity which is dependent upon the elasticity of the substrate. However, the possibility to fabricate these materials is still limited especially with a control over the mechanical properties at the micron scale. By carefully imposing and controlling temperature gradients across a microfluidic channel and exploiting the phenomenon of thermophoresis, we demonstrated the generation of gradients with tuneable properties in colloidal systems. Particularly, a microfluidic device consisted of the main microchannel and two side channels acting as hot and cold thermal sources, are used to apply the temperature gradient and fabricate biocompatible gellan gum hydrogels exhibiting stiffness gradients. Moreover, we effectively control the stiffness gradient of the biomaterials by regulating the temperature difference across the device and altering the concentration of the gellan gum. Using Atomic Force Microscopy we characterized the biomaterials by evaluating locally Young’s modulus across the 600 μm width of the hydrogels, obtaining values ranging from 20 to 100 kPa. Furthermore, we monitored cell behavior over time by seeding MC3T3 osteoblasts on the surface of the biomaterial. Cell migration and mineralization are observed on the surface of the material at different stiffness areas and time points, using live/dead assays and x-ray fluorescence technique. The results obtained gave us valuable information for the design and improvement of future 3D scaffolds.

Thermophoretic manipulation of the mechanical properties of biomaterials in microfluidics

2019 Fall National Meeting

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