Abstract
This report describes the two component self-assembly of π-capped amino acid hydrogelators (serine (S), aspartic acid (D), glutamic acid (E) or lysine (K)) prepared from pyrene (Py) based donor and naphthalenediimide (NDI) based acceptor molecules. The co-assembly can be triggered to form hydrogels by varying the pH conditions and the major driving forces behind the hydrogelation were found to be the formation of a strong charge-transfer (CT) complex and hydrogen bonding interactions at suitable pH conditions. The NDI–Py blends with matched donor/acceptor amino acid pairs undergo self-assembly under acidic pH conditions, whereas the blend (NDI–S + Py–K) with a mismatched amino acid pair forms a stable hydrogel under physiological pH conditions. UV-Vis, FTIR and rheological studies clearly indicate the formation and the stability of these CT-induced hydrogels. These hydrogels are of nanofibrous morphology with an average diameter of about 6–9 nm as evidenced by TEM analysis. In addition, this novel NDI–Py mixed component system exhibited good biocompatibility towards PC3 cells. Overall, since hydrogels based on CT-mediated two-component assemblies are very rare, our newly discovered NDI–Py hydrogels provide chemical insights into the design of a CT-induced hydrogelator and might facilitate various applications in biomedical engineering.
Highlights
Supramolecular assemblies, prepared from p-conjugated building blocks have attracted great attention owing to their diverse range of material applications.[1,2,3,4] Among them, aromatic peptide/amino acid based supramolecular nanomaterials have received signi cant interest in recent years due to their potential applications in tissue engineering, drug delivery, enzyme assay and protein separations.[5,6,7,8,9] hydrogels prepared from such organic materials possess signi cant bio-functionality and biodegradability
Since hydrogels based on CT-mediated two-component assemblies are very rare, our newly discovered NDI–Py hydrogels provide chemical insights into the design of a CT-induced hydrogelator and might facilitate various applications in biomedical engineering
To develop CT-based supramolecular hydrogels, we have synthesized a small library of NDI (1a, 1b, 1c, and 1d) and Py (2a, 2b, 2c and 2d) capped amino acid conjugates (Scheme 1) based on the method described by our previous report.[30]
Summary
Supramolecular assemblies, prepared from p-conjugated building blocks have attracted great attention owing to their diverse range of material applications.[1,2,3,4] Among them, aromatic peptide/amino acid based supramolecular nanomaterials have received signi cant interest in recent years due to their potential applications in tissue engineering, drug delivery, enzyme assay and protein separations.[5,6,7,8,9] hydrogels prepared from such organic materials possess signi cant bio-functionality and biodegradability Such molecules aggregate in aqueous conditions through various weak non-covalent interactions through hydrogen bonding, hydrophobic interactions and p–p interactions to generate onedimensional (1D) nano bers. Temperature Tgel–sol was measured using circulating water bath (digital temperature control) by increasing the temperature of the hydrogel at the rate of 1 C minÀ1
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