Supramolecular guest-host composites of adamantane-modified gelatin and β-cyclodextrin polymers, displaying...

Because of their strong complexation behavior, guest-host interactions between adamantane (Ad) and β-cyclodextrin (CD) are often used to create physically crosslinked, reversible supramolecular networks. In this work, scalable syntheses of adamantane-modified gelatin (GelAd) and high molecular weight, water-soluble β-cyclodextrin polymers (CDPs) are presented. Despite confirmed Ad-CD complexation, guest-host combinations of GelAds and CDPs resulted in viscous liquids with viscosities up to tens of Pa.s in all cases at physiological temperature. The resulting viscous composites showed strong shear-thinning and excellent self-healing behavior, but consistently higher loss moduli than storage moduli (G″ > G'), even at high polymer concentrations, high degrees of GelAd modification, and with CDPs near the solubility-limited molecular weight. The addition of laponite enabled true solid hydrogel formation at physiological temperature, but the resulting solid hydrogel was not completely self-healing. The GelAd-CDPs composites exhibited improved resistance to degradation by collagenase. Surprisingly, the composites exhibited no cellular attachment by NIH/3T3 fibroblasts despite the presence of native RGD motifs on gelatin. In addition, the NIH/3T3 fibroblasts remained viable near the gel interface over 12 days, indicating no cytotoxicity and making them highly bioinert. These results reveal that Ad-CD guest-host interactions were in this case not sufficient to form truly solid hydrogels at physiological temperature. Instead, strongly viscous soft composites were formed. The unique combination of shear-thinning, self-healing, improved collagenase resistance, cytocompatibility and bioinertness highlights these GelAd-CDP composites as promising materials for biomedical applications requiring cell-repellent and mechanically adaptive interfaces.