(624d) Reversible Crosslinking of Engineered Hyaluronic Acid Hydrogels

Extracellular matrix (ECM) mechanics are well known to influence cellular phenotype; however, the effects of dynamic changes in ECM mechanics on cellular behavior are less understood. Recent work in biomaterials has led to many in vitro cell culture substrates with dynamic properties to isolate the effects of changes in mechanics. While these substrates span a range of polymeric chemistries and viscoelastic properties, there are few with the ability to revert to the initial condition. To address this issue, we designed hyaluronic acid-based hydrogels with photoresponsive crosslinkers. Specifically, hyaluronic acid polymers were modified with 4-(4-(1-(acryloyloxy)ethyl)-2-methoxy-5-nitrophenoxy)butanoic acid, which provides acrylate moieties for crosslinking via Michael-type addition reactions with thiols. Upon exposure to 365 nm light (5 mW/cm²), degradation of the hydrogel network occurs via lysis of the nitrobenzyl ether group. Additional crosslinks can be generated using unconsumed acrylate groups by introduction of a photoinitiator such as eosin-Y and visible light. Using this method, the modulus can be switched by at least 2-fold in a biologically relevant range (initial modulus of approximately 1-4 kPa). Importantly, the high density of functional groups along the backbone of linear hyaluronic acid polymer chains allow for this tunability in mechanics, even when using irreversible cleavage reactions. In addition, the plethora of functional groups allows for the incorporation of cell adhesive moieties (such as RGD peptides) independent of the crosslinking sites. Ongoing work will address cellular morphology and markers of mechanotransduction in response to the changes in ECM mechanics.