Semi-Synthetic Biomaterials Enabled by Organisms with an Expanded Genetic Code

The ability of natural biopolymers to shape, support, and orchestrate function inspire our efforts to produce functional biomaterials. Guided by natural protein-based polymers, template directed incorporation of synthetic building blocks can further expand function by endowing new physical and biophysical properties. Here, we present the synthesis and applications of protein-polymers that contain programmable combinations of natural and synthetic amino acids (sAAs). In this study, we utilized genomically recoded organisms and a genome engineering based evolution platform to evolve enzymes of the translation machinery, capable of multi-site incorporation of synthetic amino acids harboring bio-orthogonal chemical groups. We employed these enzymes to produce high yields of intrinsically disordered proteins, elastin-like polypeptides (ELPs), decorated with up to 30 instances of an azide-containing sAA. We then utilized these polymers to demonstrate proof of concept for a new strategy, based on a clinically approved concept, to increase peptide half-life in vivo: using poly fatty acid decorated polymers to mediate and tune albumin binding post injection. We show that fatty-acid alkynes can be efficiently conjugated to the introduced azide group via click chemistry at suitable alkyne:azide ratios. In vitro and in vivo characterization of these novel semi-synthetic biomaterials revealed unique properties including dramatically improved half-life (>10 fold) compared with proteins decorated with a single fatty-acid, the current state-of-the-art. This work provides the basis for a new approach for template directed synthesis of novel proteins and biomaterials containing diverse synthetic chemical groups, with broad potential for applications in the study and treatment of a variety of diseases.