Abstract
The stereochemistry of polymers has a profound impact on their mechanical properties. While this has been observed in thermoplastics, studies on how stereochemistry affects the bulk properties of swollen networks, such as hydrogels, are limited. Typically, changing the stiffness of a hydrogel is achieved at the cost of changing another parameter, that in turn affects the physical properties of the material and ultimately influences the cellular response. Herein, we report that by manipulating the stereochemistry of a double bond, formed in situ during gelation, materials with diverse mechanical properties but comparable physical properties can be obtained. Click-hydrogels that possess a high % trans content are stiffer than their high % cis analogues by almost a factor of 3. Human mesenchymal stem cells acted as a substrate stiffness cell reporter demonstrating the potential of these platforms to study mechanotransduction without the influence of other external factors.
Highlights
The 3-dimensional arrangement of bonds, or stereochemistry, dictates the function and behaviour of molecules spanning from biological systems to drugs to synthetic polymers
Click-hydrogel architecture used in the study: alkyne- and thiol-functionalised PEG precursors, 42A and 42S in which the main number relates to the number of arms on the PEG precursor, 4-arm, while the subscript denotes the molecular weight of the polymer and functional group (2 kg molÀ1, alkyne (A) or thiol (S))
To exploit the benefits of using the nucleophilic thiol–yne addition reaction to create stererochemically defined robust click-hydrogels, we chose the PEG-based click-hydrogel 42A42S (in which the main number relates to the number of arms on the alkyne (A) or thiol (S) precursor, while the subscript denotes the molecular weight of the polymer and functional group; Scheme 1, Figure S1) as our model since it had exhibited the highest compressive strength over time with little swelling.[22b] because of the hydrophobic nature of the crosslinked network, no bulk degradation occurred for 15 days after immersing the click-hydrogels in an aqueous environment under physiological conditions
Summary
The 3-dimensional arrangement of bonds, or stereochemistry, dictates the function and behaviour of molecules spanning from biological systems to drugs to synthetic polymers. While it is well known that control over stereochemistry in polymers results in notable changes in thermal and/or mechanical properties,[1] the use of such a concept to significantly influence a highly swollen network has been comparatively less studied. Previous work in our group has utilised this reaction for the synthesis of thermoplastic materials with tuneable mechanical properties defined by the stereochemistry of the alkene moiety.[21] we have synthesised nucleophilic thiol–yne addition click-hydrogels as robust ECM mimics which can encapsulate cells and modulate stiffness and swelling.[22]. We demonstrate how controlling stereochemistry enables discrete changes in mechanical strength and substrate stiffness, without changing other physical properties that influence cell response (i.e. crosslinking density, pore size or toxicity). Can contribute to understanding how cells are influenced by stiffness alone, and, how cells sense different polymer stereochemistry
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call