Issue 5, 2016

Molecular design for growth of supramolecular membranes with hierarchical structure

Abstract

Membranes with hierarchical structure exist in biological systems, and bio-inspired building blocks have been used to grow synthetic analogues in the laboratory through self-assembly. The formation of these synthetic membranes is initiated at the interface of two aqueous solutions, one containing cationic peptide amphiphiles (PA) and the other containing the anionic biopolymer hyaluronic acid (HA). The membrane growth process starts within milliseconds of interface formation and continues over much longer timescales to generate robust membranes with supramolecular PA–HA nanofibers oriented orthogonal to the interface. Computer simulation indicates that formation of these hierarchically structured membranes requires strong interactions between molecular components at early time points in order to generate a diffusion barrier between both solutions. Experimental studies using structurally designed PAs confirm simulation results by showing that only PAs with high ζ potential are able to yield hierarchically structured membranes. Furthermore, the chemical structure of such PAs must incorporate residues that form β-sheets, which facilitates self-assembly of long nanofibers. In contrast, PAs that form low aspect ratio nanostructures interact weakly with HA and yield membranes that exhibit non-fibrous fingering protrusions. Furthermore, experimental results show that increasing HA molecular weight decreases the growth rate of orthogonal nanofibers. This result is supported by simulation results suggesting that the thickness of the interfacial contact layer generated immediately after initiation of self-assembly increases with polymer molecular weight.

Graphical abstract: Molecular design for growth of supramolecular membranes with hierarchical structure

Supplementary files

Article information

Article type
Paper
Submitted
22 Sept. 2015
Accepted
30 Nov. 2015
First published
09 Dec. 2015

Soft Matter, 2016,12, 1401-1410

Author version available

Molecular design for growth of supramolecular membranes with hierarchical structure

R. Helen Zha, Y. S. Velichko, R. Bitton and S. I. Stupp, Soft Matter, 2016, 12, 1401 DOI: 10.1039/C5SM02381E

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