Published online by Cambridge University Press: 11 December 2015
Covalent functionalisation of collagen has been shown to be a promising strategyto adjust the mechanical properties of highly swollen collagen hydrogels. At thesame time, secondary interactions between for example, amino acidic terminationsor introduced functional groups also play an important role and are oftenchallenging to predict and control. To explore this challenge, 4-vinylbenzylchloride (4VBC) and methacrylic anhydride (MA) were reacted with type Icollagen, and the swelling and rheological properties of resultingphoto-activated hydrogel systems investigated. 4VBC-based hydrogels showedsignificantly increased swelling ratio, in light of the lower degree of collagenfunctionalisation, with respect to methacrylated collagen networks, whilstrheological storage moduli were found to be comparable between the two systems.To explore the role of benzyl groups in the mechanical properties of the4VBC-based collagen system, model chemical force microscopy (CFM) was carriedout in aqueous environment with an aromatised probe against an aromatisedgold-coated glass slide. A marked increase in adhesion force(F: 0.11±0.01 nN) was measured between aromatisedsamples, compared to the adhesion force observed between the non-modified probeand a glass substrate (F: 2.64±1.82 nN). These resultssuggest the formation of additional and reversible π-πstacking interactions in aromatic 4VBC-based networks and explain the remarkablerheological properties of this system in comparison to MA-based hydrogels.