In Situ Gelation of Stimuli-Responsive Elastin and Suckerin-Based Tri-Block Copolypeptides with Adhesive Properties

Recombinant protein-based bioadhesives have been of great importance for biomedical applications because their amino acid sequences, molecular weights, and physicochemical properties are precisely controlled at gene level while they have biocompatibility and biodegradability. There have been some studies on mussel foot protein-, suckerin- and elastin-based bioadhesives based on the l-3,4-dihydroxylphenylalanine (DOPA)-mediated cross-linking as well as the cross beta sheet. In this work, we rationally designed, bio-synthesized, and non-chromatographically purified a series of ABA type tri-block copolypeptides composed of sticky elastin-based polypeptides (EBPs) and beta sheet-forming suckerin-based polypeptides (SBPs) at different block length ratios for injectable hydrogels with controlled surface adhesion properties. Especially, in order to introduce the adhesive properties of stimuli-responsive EBPs, sticky EBPs with varied ratio of Lys and Tyr residues were prepared for pi-cation interactions and DOPA-mediated surface adhesion by enzymatic hydroxylation. We hypothesized that SBPs would form the stable cross beta sheets while sticky EBPs having DOPA-induced adhesive- and cohesive interactions. The modified ESE (mESE) triblock copolypeptides showed controlled lower critical solution temperature (LCST) behavior depending on the length of SBP under the identical EBP block. Moreover, the mESE triblock copolypeptides under dilute conditions exhibited self-assembled nanostructures mediated via molecular interactions between SBP blocks below LCST. The concentrated mESE triblock copolypeptides with sodium periodate rapidly formed hydrogels via formation of the cross beta sheets of the SBP block and periodate-mediated crosslinking of DOPAs. The physically and chemically cross-linked mESE triblock copolypeptide hydrogels with controlled mechanical properties showed finely tuned adhesive strength in the range of 0.5 – 5.5 MPa depending on the concentration of sodium periodate and SBP block length. In conclusion, the injectable triblock copolypeptide hydrogels with controlled adhesive strength under wet conditions make them ideal candidates for biomedical applications such as sealants after anastomosis and tissue adhesives.