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

Abstract

Hydrogels hold much promise for 3D printing of functional living materials; however, challenges remain in tailoring mechanical robustness as well as biological performance. In addressing this challenge, 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 is described. 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 writing (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 Escherichia 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.

Advanced supramolecular design for direct ink writing of soft materials

“…Very recently, three-arm synthetic polypeptide–polymer conjugates with hydrogen-bonded β-sheets have been introduced for DIW. 177 In this design, hydrophobic polypeptides, poly(tyrosine) or poly(valine), have been introduced to form anti-parallel β-sheets, which serve as supramolecular crosslinkers for the network. The polypeptide–polymer conjugate hydrogels showed good shear-thinning and self-healing rheological properties, which were 3D-printed and photo-crosslinked as bio-compatible scaffolds to house bacteria.…”

Tailoring Writability and Performance of Star Block Copolypeptides Hydrogels through Side‐Chain Design

“…[55] While we have previously shown the ability of analogous hydrogels to print multilayered 3D structures, here the resolution of intricate two-layered patterns were studied. [38] In particular, the differences in filament uniformity is exacerbated when printing a two-layer complex lattice in the x-y plane that can be semi-quantified using printability (P r ) values (Equation (S2), Supporting Information). [14,55] The fast recovering, higher yield-stress 3-CP-PG gives a P r value of 1.03 at 170 kPa, while the slower recovering and weaker 3-CP-T gives a P r value of 1.2 at 40 kPa (Figure 6B and Figure S33, Supporting Information).…”

“…[31][32][33][34][35][36][37] Recently, our group demonstrated the synthetic versatility of block copolypeptides and their applicability to the development of bioinks that can be chemically crosslinked with visible light. [38] This strategy generates well-defined, viable biocomposites with Escherichia coli, controlling the behavior of embedded bacteria by modulating mechanical properties of the host block copolypeptide hydrogel through a functional-group change in associating domains. Further understanding structure-function relationships in these physically crosslinked junctions is critical to extend the generality of this approach and tune performance by varying block chemistry, concentration, and architecture.…”

“…While block copolypeptides containing cationic polylysine inner blocks have been widely studied, anionic polyglutamates are of interest due to the carboxyl groups serving as sites for cation-chelating and post-polymerization modification. [38] Amino acids incorporated into the outer blocks were selected based on their propensity to form hydrophobic and 𝜋-𝜋 interactions in order to correlate chain structure with 𝛽-sheet network strength. Specifically, 3-arm block copolypeptides (3-CP) with the same polyglutamic acid core and outer blocks containing valine (3-CP-V), leucine (3-CP-L), tyrosine (3-CP-T), phenyl glycine (3-CP-PG), and phenylalanine (3-CP-PA) were investigated.…”

Catalytic Materials Enabled by a Programmable Assembly of Synthetic Polymers and Engineered Bacterial Spores

“…Natural materials seamlessly integrate complex catalytic functionalities into a structural scaffold through an autonomous assembly process. The past few decades have seen the emergence of engineered living materials as a new way to capture biological functionalities. − Living cells in these materials were engineered to build biofilm-like structures or embedded into hydrogels to perform genetically-encoded enzymatic functions. − In addition, by combining rationally designed polymer scaffolds with genetically engineered cells, living materials can have tailored mechanical and dynamic properties. We have recently reported a molecular assembly strategy to construct living materials with designed synthetic polymers and living cells. , …”