Precision Gels from Collagen-Inspired Triblock Copolymers

Abstract

Gelatin hydrogels find broad medical application. The current materials, however, are from animal sources, and their molecular structure and thermal properties cannot be controlled. This study describes recombinant gelatin-like polymers with a general design that inherently offers independent tuning of the cross-link density, melting temperature, and biocompatibility of the gel. The polymers contain small blocks with thermoreversible trimerization capacity and defined melting temperature, separated by hydrophilic nontrimerizing blocks defining the distance between the knot-forming domains. As an example, we report the secreted production in yeast at several g/L of two nonhydroxylated approximately 42 kDa triblock copolymers with terminal trimerizing blocks. Because only the end blocks formed cross-links, the molecular architecture of the gels is much more defined than that of traditional gelatins. The novel hydrogels had a approximately 37 degrees C melting temperature, and the dynamic elasticity was independent of the thermal history. The concept allows to produce custom-made precision gels for biomedical applications.

Physics of engineered protein hydrogels

“…Consistent with the theory of gelation, an association number of >2 is required for gelation of telechelic polymers. 38 Trimeric coiled-coils based on collagen 52,62 and fibrin-inspired 63 triple helices have been used as crosslinking domains, and the linear mechanical behavior of these gels agrees well with the established models [34][35][36] for physical gels. 52 Changing the coiled-coil from tetrameric to pentameric results in an increase in the hydrogel modulus and a slowing of the gel erosion rate, corresponding to an increase in the fraction of elastically effective chains within the network.…”

PEG-Based Hydrogels with Collagen Mimetic Peptide-Mediated and Tunable Physical Cross-Links

“…At high concentrations and below the peptide’s T m , the triple helix formation between different staggered CMP molecules led to the assembly of supramolecular peptide structures that created a self-supporting gel 16. De Wolf and coworkers employed recombinant protein methods to create triblock copolymers featuring collagen mimetic sequences 17. These triblock copolymers also exhibited temperature-sensitive gelling behavior based on the melting of the triple helical crosslinks that hold the gel together.…”

Secreted production of self-assembling peptides in Pichia pastoris by fusion to an artificial highly hydrophilic protein

“…The presence of alternating hydrophobic (Phe, Trp) and hydrophilic (Gln, Arg and Glu) side-chains renders one surface of the ␤-sheet more hydrophilic than the other (Aggeli et al, 1997b). At a peptide concentration of about 0.1 mM, in water, P 11 -2 associates into long, stable semiflexible ␤-sheet ribbons 2005), silk-like proteins (Werten et al, 2008), elastin-like proteins (Schipperus et al, 2009), and self-assembling block copolymers (Martens et al, 2009;Werten et al, 2009), mostly at g l −1 levels. P. pastoris is an attractive host for large-scale production, as it grows in low-cost media, offers good genetic stability, and permits scale-up of the production process without loss of yield (Cregg et al, 1993;Romanos, 1995).…”