Hydrogels resulting from the self-assembly of small peptides are smart nanobiomaterials as their nanostructuring can be readily tuned by environmental stimuli such as pH,ionic strength and temperature,thereby favoring their practical applications.This work reports experimental observations of formation of peptide hydrogels in response to the redox environment.Ac-I 3 K-NH 2 is a short peptide amphiphile that readily self-assembles into long nanofibers and its gel formation occurs at concentrations of about 10 mmol/L.Introduction of a Cys residue into the hydrophilic region leads to a new molecule,Ac-I 3 CGK-NH 2,that enables the formation of disulfide bonds between self-assembled nanofibers,thus favoring cross-linking and promoting hydrogel formation.Under oxidative environment,Ac-I 3 CGK-NH 2 formed hydrogels at much lower concentrations(even at 0.5 mmol/L).Furthermore,the strength of the hydrogels could be easily tuned by switching between oxidative and reductive conditions and time.However,AFM,TEM,and CD measurements revealed little morphological and structural changes at molecular and nano dimensions,showing no apparent influence arising from the disulfide bond formation.
CAO ChangHaiCAO MeiWenFAN HaiMingXIA DaoHongXU HaiLU Jian R
A peptide nucleic acid （PNA）-peptide conjugated molecule, T＇3（AKAE）2, was designed to have both a PNA segment for oligo- nucleotide binding and an ionic self-complementary peptide sequence for self-association. T＇3（AKAE）2 could co-assemble with oligoadenines （d（A）x） to form virus-like supramolecular structures whose morphology showed dependence on the chain length and rigidity of the d（A）x molecules. Smaller nanospheres with diameters of 13.0±2.0 nm were produced in the case of d（A）6. Wormlike aggregates with lengths of 20-50 nm and diameters of 15.0±2.5 nm were found in the cases of d（A）12, d（A）ls, d（A）24 and d（A）30. And larger spherical aggregates with diameters of 18±5 nm came into presence in the cases of d（A）36 and d（A）42＋. These nanostructures were suggested to be formed under a cooperative effect of base pair recognition and peptidic association. The study provides insights into the programmed assembly of a multi-components system as well as control of the size and shade of the co-assembled structures, which is of great significance in develouing gene/drug deliverv systems.
