Investigation of tunable viscoelastic hydrogels for mechanotransduction studies.
Hydrogel substrates with tunable dissipation properties has various potential applications in orthopedic load bearing applications and as scaffolds for cell culture. Tuning of stiffness and toughness by using double network gels consisting of two polymer networks has been explored for such applications. However, the mechanical properties of such hydrogels are often hindered by swelling. Moreover, development of hydrogels with stable mechanical properties and tuning of dissipation in such hydrogels using simple approaches remains a challenge. Recently, there has been a considerable research interest in using hydrogels with tunable loss modulus or dissipation properties as substrates in studies of cellular mechanotransduction. In our research, we explored the influence of polymerizing monomers inside a cross-linked polymer network. The second networks are formed through in-situ polymerization and are designed to hydrogen bond with the first cross-linked polymer network. Specifically, we used acrylic acid and tannic acid as monomers, which can polymerize inside a cross-linked gel to form linear poly(acrylic acid) chains and oligomeric poly(tannic acid) respectively. We investigated the mechanical properties using a suite of mechanical characterization including compression and tensile testing. The tuning of loss modulus was achieved through UV polymerization under a photomask and subsequent characterization was performed using rheology. Furthermore, the structure-property relationships in tannic acid incorporated gels (unpolymerized and polymerized) were investigated using small angle neutron scattering (SANS) and rheology. SANS and rheology revealed the structural and mechanistic changes in the gels with temperature. Finally, we optimized the gels for cell culture studies and the effect of mechanical properties on cellular mechanotransduction was investigated. Overall, a simple approach to produce hydrogels with tunable dissipation properties was achieved and the spreading of cells in these gels were investigated. The results achieved has potential in further expanding the fundamental knowledge of rational design of hydrogels for specific applications and cellular mechanotransduction.
Hosted by Professor Zheng Shi
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