Multilayer vesicles, tubes, various porous structures and organo gels through the solvent-assisted self-assembly of two modified tripeptides and their different applications

Abstract

A set of two modified tripeptides containing conformationally rigid m-aminobenzoic acid (m-ABA) as a template at the C-terminal self-assemble to form diverse micro- and nanostructure materials such as nanovesicles, nanotubes, giant microvesicles, macroporous vesicular structures including macroporous films, macro- and mesoporous materials, and organo gels—depending upon the solvent polarity. A balanced participation of the hydrogen bonding and the π–π interactions mainly between aromatic rings of m-ABA is crucial for this morphological diversity. Insertion of an aromatic amino acid instead of an aliphatic one in the peptide sequence drastically changes the morphology of the nanostructures formed from a particular solvent system. Interestingly these short hydrophobic peptides form salt-responsive multilayer vesicular structures from methanolic solutions, where the diameter of the vesicles increases with an increase of concentration. The most important property of these multilayer vesicular structures is the encapsulation of a potent natural hydrophobic drug curcumin and of a fluorescent dye rhodamine B, which can be effectively released in presence of biocompatible metal ions. Moreover, the encapsulation efficiency and release profile of drug and other biologically important guest molecules have been successfully quantified. We have developed a simple modified peptide based organogelator from chloroform, where the xerogel shows the striking property of adsorbing dye rhodamine B from water, which can be utilized in water purification by removing the toxic dye from waste water. Short peptide based macroporous vesicular structures including macroporous films have been successfully fabricated through controlled self-assembly employing solvents with different chloroform–petroleum ether ratios. Furthermore, the mesoporous structures prepared from toluene can efficiently absorb I₂.