Non-covalently crosslinked hydrogels displaying a unique combination of water-absorbing, elastic and adhesive properties

Background: Stringent requirements must be satisfied by biomedical adhesives, including biocompatibility, adhesion, cohesiveness and processability. The ability to change mechanical properties in response to environmental changes may also be desirable. In the present work the water-absorbing, adhesive and mechanical properties of blends based on hydrogen bonding complexes between poly(N-vinyl pyrrolidone), poly(ethylene glycol) (PEG) and poly[(methacrylic acid)-co-(ethyl acrylate)] were investigated. These blends, consisting of pharmaceutical-grade components, exhibit pH-sensitive swelling and dissolution, along with rubber-like elasticity and bioadhesion. Results: Polymer blend films remained intact at pH = 5.6 but underwent dissolution at pH = 7.4, the difference being attributed to deprotonation of acidic side-chains, with loss of hydrogen bonding and development of charge repulsion. Sol release was primarily due to PEG. Films swelled at low pH instead of dissolving, in a manner that was pH-dependent but PEG-independent. Films displayed elastic properties comparable to cured elastomers when mildly swollen, with modulus and ultimate strength decreasing with increasing PEG content. Dry films were nearly tack-free, but became more adhesive with increasing water content, up to a point where the film dissolved. Conclusion: Due to their biocompatibility and dissolution/mechanical properties, the bioadhesive polymer blends investigated may be suitable for numerous biomedical applications.