(262e) Graduate Student Award Session: Supramolecular Reinforcement of Polymer–Nanoparticle Hydrogels for Modular Material Design

Moldable hydrogel biomaterials are often able to flow under applied stress (shear-thin) and reform a stable network (self-heal) upon cessation of stress. In polymer–nanoparticle (PNP) hydrogels, these viscoelastic properties arise from non-covalent reversible interactions between polymer chains and nanoparticles.¹ While PNP hydrogels are increasingly used as injectable or extrudable materials in biomedical and industrial applications, their mechanical properties are limited and network formation is restricted to interactions between specific combinations of polymer chains and nanoparticles.^2–4 Here, we present a facile approach to reinforce PNP hydrogels through a supramolecular binding motif by including α-cyclodextrin (αCD) in the formulation.⁵ Rheological measurements demonstrated that the addition of αCD reinforced the mechanical properties of PNP (CD–PNP) hydrogels in a concentration-dependent manner achieving storage moduli, G′, up to G′ ≈ 10⁴ Pa (ω = 1 rad s^-1). All hydrogels retained the ability to shear-thin and self-heal. We hypothesized that the enhancement of mechanical properties resulted from reinforced interactions between PEGylated nanoparticles caused by the threading of αCD onto nanoparticles leading to polypseudorotoxane formation.^6,7 CD-reinforcement allowed us to decouple mechanical properties from material functionality. We were able to exchange the structural polymers (hydroxypropylmethylcellulose, collagen, alginate, and methacrylated hyaluronic acid), and nanoparticles (block copolymer nanoparticles, gold nanoparticles, and iron nanoparticles), forming stable networks (tan δ < 1, ω = 1 rad s^-1) in all cases. CD–PNP formulations showed improved properties and tunability for 3D bioprinting and drug delivery applications. Additionally, the application spectrum of this class of materials was broadened by using CD–PNP hydrogels for electroconductive and magnetic applications. Overall, supramolecular reinforcement of PNP hydrogels simplified (bio)material design and broadened the application spectrum without the need to re-engineer the network interactions.

References:

[1] Appel, E. A., Tibbitt, M. W. et al. Nat. Commun. 6, 6295, (2015)
[2] Fenton, O. S. et al. Biomacromolecules 20, 4430–4436, (2019)
[3] Stapleton, L. M. et al. Nat. Biomed. Eng. 3, 611–620, (2019)
[4] Guzzi, E. A. et al. Small 15, 1905421, (2019)
[5] Bovone, G., Guzzi, E. A., Bernhard, S. et al. Adv. Mater. 2106941, (2022)
[6] Harada, A. et al. Nature 370, 126–128, (1994)
[7] Liu, K. L. et al. Soft Matter 7, 11290–11297, (2011)