SANS and Cryo-TEM Study of Self-Assembled Diblock Copolypeptide Hydrogels with Rich Nano- through Microscale Morphology

Polypeptide hydrogels via a unique assembly mechanism

There is a long history of man's use of materials derived from peptides and proteins. These natural materials possess sophisticated mechanisms of nanoscale self assembly, which have inspired the design of many synthetic and biosynthetic amino-acid based materials. These materials are attractive since they can have exceptional properties, environmental responsive behavior, biological activity, and can be metabolized. With all of their complexity, peptides and proteins rely primarily on two fundamental modes of self assembly: association of β-strands and the coiling of helices. In this context, a class of recently synthesized and characterized polypeptide materials are reviewed here, which were found to self-assemble by a fundamentally different process. This new mode of assembly was found to give rise to polypeptide hydrogels with a unique combination of properties ( heat stability and injectability) making them attractive for applications in foods, personal care products, and medicine.

Solution Self-Assembly of Hybrid Block Copolymers Containing Poly(ethylene glycol) and Amphiphilic β-Strand Peptide Sequences

The self-assembly in aqueous solution of hybrid block copolymers consisting of amphiphilic beta-strand peptide sequences flanked by one or two PEG chains was investigated by means of circular dichroism spectroscopy, small-angle X-ray scattering, and transmission electron microscopy. In comparison with the native peptide sequence, it was found that the peptide secondary structure was stabilized against pH variation in the di- and tri-block copolymers with PEG. Small-angle X-ray scattering indicated the presence of fibrillar structures, the dimensions of which are comparable to the estimated width of a beta-strand (with terminal PEG chains in the case of the copolymers). Transmission electron microscopy on selectively stained and dried specimens shows directly the presence of fibrils. It is proposed that these fibrils result from the hierarchical self-assembly of peptide beta-strands into helical tapes, which then stack into fibrils.