Thiol-Ene Photo-Click Hydrogels with Tunable Mechanical Properties Resulting from the Exposure of Different -Ene Moieties through a Green Chemistry

Abstract

Temperature and light responsiveness are widely exploited stimuli to tune the physico-chemical properties of double network hydrogels. In this work, new amphiphilic poly(ether urethane)s bearing photo-sensitive moieties (i.e., thiol, acrylate and norbornene functionalities) were engineered by exploiting the versatility of poly(urethane) chemistry and carbodiimide-mediated green functionalization procedures. Polymers were synthesized according to optimized protocols maximizing photo-sensitive group grafting while preserving their functionality (approx. 1.0 × 1019, 2.6 × 1019 and 8.1 × 1017 thiol, acrylate and norbornene groups/gpolymer), and exploited to prepare thermo- and Vis-light-responsive thiol-ene photo-click hydrogels (18% w/v, 1:1 thiol:ene molar ratio). Green light-induced photo-curing allowed the achievement of a much more developed gel state with improved resistance to deformation (ca. 60% increase in critical deformation, γL). Triethanolamine addition as co-initiator to thiol-acrylate hydrogels improved the photo-click reaction (i.e., achievement of a better-developed gel state). Differently, L-tyrosine addition to thiol-norbornene solutions slightly hindered cross-linking, resulting in less developed gels with worse mechanical performances (~62% γL decrease). In their optimized composition, thiol-norbornene formulations resulted in prevalent elastic behavior at lower frequency compared to thiol-acrylate gels due to the formation of purely bio-orthogonal instead of heterogeneous gel networks. Our findings highlight that exploiting the same thiol-ene photo-click chemistry, a fine tuning of the gel properties is possible by reacting specific functional groups.

Antibacterial Hydrogel Adhesives Based on Bifunctional Telechelic Dendritic-Linear–Dendritic Block Copolymers

“…TEC offers higher reproducibility through the obtention of uniform and controllable networks with improved mechanical performances due to the higher stability of the thioether bond . The reaction proceeds via a rapid, stepwise reaction rate, is highly efficient under mild aqueous conditions, and can be initiated on demand with high-energy visible (HEV) light. − Additionally, its high monomer conversion before vitrification reduces the likelihood of unreacted monomers leeching out. , As a further step, TEC networks have preclinically been validated in realistic surgical conditions for fracture stabilization …”

Structural and Transport Properties of Norbornene-Functionalized Poly(vinyl alcohol) “Click” Hydrogel: A Molecular Dynamics Study

“…2,10,11 The thiol−ene "click" hydrogels possess unique properties such as high water content, 12 excellent biocompatibility, 13 and tunable mechanical strength. 14 They have found applications in various fields, including tissue engineering, 15 drug delivery, 2 and biosensing. 16 The thiol−ene cross−linked PVA hydrogels offer improved stability and long−term performance compared to other hydrogel systems.…”

“…The chemical cross–link is conveniently achieved by functionalizing the hydroxyl moiety with aminoxy, hydrazide, acrylamide, thiol, and semicarbazide, cysteine moieties with maleimide and 2–halo acetyl . Apart from that, photo-initiated thiol–ene “click” reactions have recently gained attention for control network hydrogel formation. ,, The thiol–ene “click” hydrogels possess unique properties such as high water content, excellent biocompatibility, and tunable mechanical strength . They have found applications in various fields, including tissue engineering, drug delivery, and biosensing .…”