Tyrosinase-catalyzed synthesis of a universal coil-chitosan bioconjugate for protein immobilization

Chitosan has been reported as a promising material for gene and drug delivery as well as for tissue engineering and regenerative medicine. We report here the conjugation of a de novo designed coil peptide (Kcoil) to chitosan (M-n = 200 kDa) to achieve a universal Kcoil-chitosan scaffold for subsequent immobilization of proteins tagged with the Kcoil partner, i.e., the Ecoil peptide. Kcoil-chitosan conjugate was synthesized using a tyrosinase-catalyzed protocol. Extensive UV/vis and IR characterization demonstrated that Kcoil peptide was covalently grafted to amines of chitosan. The ability of Kcoil-chitosan conjugate to recruit Ecoil tagged epidermal growth factor (EGF) was assessed by surface plasmon resonance measurements (SPR). Despite nonspecific interactions between chitosan and EGF, the specific formation of an E/K coiled coil complex was observed at slightly acidic pH and high salt concentration conditions, demonstrating that grafting to chitosan did not negatively impact binding characteristics of Kcoil peptide. Finally, the benefits of such bioconjugates for biomedical applications are discussed.