Tailored Polypeptide Star Copolymers for 3D Printing of Bacterial Composites Via Direct Ink Writing.

Hydrogels hold much promise for 3-D printing of functional living materials, however challenges remain in tailoring mechanical robustness as well as biological performance. In addressing this challenge, we describe the modular synthesis of functional hydrogels from 3-arm diblock copolypeptide stars composed of an inner poly(L-glutamate) domain and outer poly(L-tyrosine) or poly(L-valine) blocks. Physical crosslinking due to ß-sheet assembly of these star block copolymers gives mechanical stability during extrusion printing and the selective incorporation of methacrylate units allows for subsequent photocrosslinking to occur under biocompatible conditions. This permits direct ink write (DIW) printing of bacteria-based mixtures leading to 3D objects with high fidelity and excellent bacterial viability. The tunable stiffness of different copolypeptide networks enables control over proliferation and colony formation for embedded E.coli bacteria as demonstrated via isopropyl ß-D-1-thiogalactopyranoside (IPTG) induction of green fluorescent protein (GFP) expression. This translation of molecular structure to network properties highlights the versatility of these polypeptide hydrogel systems with the combination of writable structures and biological activity illustrating the future potential of these 3D printed biocomposites. This article is protected by copyright. All rights reserved.