Tissue Adhesion-Anisotropic Polyrotaxane Hydrogels Bilayered with Collagen

Hydrogels are promising materials in tissue engineering scaffolds for healing and regenerating damaged biological tissues. Previously, we developed supramolecular hydrogels using polyrotaxane (PRX), consisting of multiple cyclic molecules threaded by an axis polymer for modulating cellular responses. However, since hydrogels generally have a large amount of water, their adhesion to tissues is extremely weak. Herein, we designed a bilayered hydrogel with a PRX layer and a collagen layer (PRX/collagen hydrogel) to achieve rapid and strong adhesion to the target tissue. The PRX/collagen hydrogel was fabricated by polymerizing PRX crosslinkers in water with placement of a collagen sponge. The differences in components between the PRX and collagen layers were analyzed using Fourier transform infrared spectroscopy (FT-IR). After confirming that the fibroblasts adhered to both layers of the PRX/collagen hydrogels, the hydrogels were implanted subcutaneously in mice. The PRX hydrogel without collagen moved out of its placement site 24 h after implantation, whereas the bilayer hydrogel was perfectly adherent at the site. Together, these findings indicate that the bilayer structure generated using PRX and collagen may be a rational design for performing anisotropic adhesion.

Post-synthesis modification of slide-ring gels for thermal and mechanical reconfiguration

Ring-sliding behavior in polyrotaxanes imbues gels, elastomers, and glasses with remarkable stress-dissipation and actuation properties. Since these properties can be modulated and tuned by structural parameters, many efforts have been devoted to developing synthetic protocols that define the structures and properties of slide-ring materials. We introduce post-synthetic modifications of slide-ring gels derived from unmodified α-cyclodextrin and poly(ethylene glycol) polyrotaxanes that enable (i) actuation and control of the thermo-responsive lower critical solution temperature (LCST) behavior of ring-modified slide-ring hydrogels, and (ii) chemically bonding separate gels into hybrid or shape-reconfigured macro-structures with a slide-ring adhesive solution. The mechanical properties of the post-modified gels have been characterized by shear rheology and uniaxial tensile tests, while the corresponding xerogels were characterized by wide-angle X-ray scattering. These demonstrations show that post-synthetic modification offers a practical solution for re-configuring the properties and shapes of slide-ring gels.

Surface-tethering of methylated polyrotaxanes with 4-vinylbenzyl groups onto poly(ether ether ketone) substrates for improving osteoblast compatibility

Poly(ether ether ketone) (PEEK) is a high-performance thermoplastic used for several industrial applications due to its excellent mechanical properties. However, the use of PEEK is limited to dental materials because of its poor implant-bone integration. In the present study, methylated polyrotaxanes (MePRXs) with 4-vinylbenzyl groups, which are supermolecules composed of methylated α-cyclodextrins and poly(ethylene glycol) chains end-capped with 4-vinylbenzyl groups, were covalently tethered onto PEEK surfaces using photo-induced polymerization to improve their osteoblast compatibility. The surface-tethering of MePRXs onto PEEK surfaces was confirmed by analyzing their attenuated total reflectance Fourier transform infrared spectra and contact angles. When mouse preosteoblasts were cultured on the MePRX-PEEK and bare PEEK surfaces, the MePRX-PEEK surfaces showed significantly better proliferation and osteoblast differentiation than the bare PEEK surfaces. These results suggest that surface modification of PEEKs using MePRXs improves their osteoblast compatibility.

Visible light-degradable supramolecular gels comprising cross-linked polyrotaxanes capped with trithiocarbonate groups

Visible light-degradable supramolecular gels were designed using polyrotaxanes (PRXs) containing bulky trithiocarbonate groups as stopper molecules that are cleaved by visible light irradiation.