Genetically engineered block copolymers: influence of the length and structure of the coiled-coil blocks on hydrogel self-assembly.
OBJECTIVE
To explore the relationship between the structure of block polypeptides and their self-assembly into hydrogels. To investigate structural parameters that influence hydrogel formation and physical properties.


METHODS
Three ABA triblock and two AB diblock coiled-coil containing polypeptides were designed and biologically synthesized. The triblock polypeptides had two terminal coiled-coil (A) domains and a central random coil (B) segment. The coiled-coil domains were different in their lengths, and tyrosine residues were incorporated at selected solvent-exposed positions in order to increase the overall hydrophobicity of the coiled-coil domains. The secondary structures of these polypeptides were characterized by circular dichroism and analytical ultracentrifugation. The formation of hydrogel structures was evaluated by microrheology and scanning electron microscopy.


RESULTS
Hydrogels self-assembled from the triblock polypeptides, and had interconnected network microstructures. Hydrogel formation was reversible. Denaturation of coiled-coil domains by guanidine hydrochloride (GdnHCl) resulted in disassembly of the hydrogels. Removal of GdnHCl by dialysis caused coiled-coil refolding and hydrogel reassembly.


CONCLUSIONS
Protein ABA triblock polypeptides composed of a central random block flanked by two coiled-coil forming sequences self-assembled into hydrogels. Hydrogel formation and physical properties may be manipulated by choosing the structure and changing the length of the coiled-coil blocks. These self-assembling systems have a potential as in-situ forming depots for protein delivery.
Xu
Chunyu
C
Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, 30 S. 2000 E. Rm. 201, Salt Lake City, Utah 84112, USA.
Kopecek
Jindrich
J
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004337:Drug Carriers; D005818:Genetic Engineering; D019791:Guanidine / Q000737:chemistry; D020100:Hydrogels; D057927:Hydrophobic and Hydrophilic Interactions; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D012212:Rheology; D013678:Technology, Pharmaceutical / Q000379:methods*; D014443:Tyrosine / Q000737:chemistry; D014461:Ultracentrifugation
D004337:Drug Carriers; D020100:Hydrogels; D010455:Peptides; D011108:Polymers; D011994:Recombinant Proteins; D011092:Polyethylene Glycols; D014443:Tyrosine; D019791:Guanidine
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