Coiled Coil Affinity-Based Systems for the Controlled Release of Biofunctionalized Gold Nanoparticles from Alginate Hydrogels

Affinity-based systems represent a promising solution to control the delivery of therapeutics using hydrogels. Here, we report a hybrid system that is based on the peptidic E/K coiled coil affinity pair to mediate the release of gold nanoparticles (NPs) from alginate scaffolds. On one hand, the gold NPs were functionalized with the Ecoil-tagged epidermal growth factor (EGF). The bioactivity of the grafted EGF and the bioavailability of the Ecoil moiety were confirmed by EGF receptor phosphorylation assays and by capturing the functionalized NPs on a Kcoil-derivatized surface. On the other hand, alginate chains were modified with azido-homoalanine Kcoil (Aha-Kcoil) by azide-alkyne click chemistry. The hybrid system was formed by dispersing NPs functionalized with the Ecoil-tagged EGF in alginate hydrogels containing either 0, 10, or 20% of Kcoil-modified alginate (Alg-Kcoil). With 20% of Alg-Kcoil, the release of Ecoil-functionalized NPs was reduced by half when compared to the release of NPs without Ecoil, whereas little to no differences were noticed with either 0 or 10% of Alg-Kcoil. Differential dynamic microscopy was used to determine the diffusion coefficient of the NPs, and the results showed a decrease in the diffusion coefficient of Ecoil-functionalized NPs, when compared to bare PEGylated NPs. Altogether, our data demonstrated that the E/K coiled coil system can control the release of NPs in a high Kcoil content alginate gel, opening diverse applications in drug delivery.