Ca²⁺ and Ag⁺ orient low-molecular weight amphiphile self-assembly into “nano-fishnet” fibrillar hydrogels with unusual β-sheet-like raft domains

Abstract

Calcium or silver ions drive self-assembly of natural glycolipid low-molecular weight gelators (LMWGs) into a fibrillar network hydrogel with a unique “nano-fishnet” structure, characterized by entanglement and β-sheet-like rafts.

In Situ Stimulation of Self-Assembly Tunes the Elastic Properties of Interpenetrated Biosurfactant–Biopolymer Hydrogels

“…Figure b shows the concomitant SAXS signature [profiles (1) to (3) correlate SAXS and rheology with the rheo-SAXS experiment], identifying the structural features of the gels. SAXS highlights a decrease in the intensity of the peaks at q = 0.25 Å –1 and q = 0.31 Å –1 , both characteristics of the crystalline structure of {F}G-C18:1 fibers, discussed elsewhere, visible at pH 10. The peaks progressively disappear at more acidic pH, suggesting a structural perturbation of the system around pH ≈ 7.…”

“…25 In this work, {F}G-C18:1 refers to a stable, equilibrated fiber hydrogel driven by adding Ca 2+ to the micellar phase of G-C18:1. The fibers, reported and characterized for the first time elsewhere, 28,29 are infinitely long crystalline threads having a cross section of about 10 nm. 29 The fibers promptly form a hydrogel in water at concentrations below 5 wt % (frequency-and strain-dependent small-amplitude oscillatory shear experiments are reported in ref 36) and undergo a gel-to-sol (fiber-tomicelle) transition between 60 and 63 °C.…”

“…26 On the other hand, the fiber phase of G-C18:1 is even more complex, as it requires two additive form factor models (core−shell parallelepiped model, lamellar paracrystal) and a structure factor. 29 The above require a fitting process with no less than 20 independent parameters, of which at least half are critical. To this system, one should add the contribution of the biopolymer in the present work, most likely using a classical flexible cylinder model, 46 which requires seven additional independent parameters.…”

“…(b) Known phase behavior in water at room temperature ( C < ∼5 wt %) of G-C18:1. Micelles form at basic pH (counterions: Na + ) and undergo a wormlike-to-vesicle-to-lamellae transition. , Crystalline fibers form from the micellar phase at pH > 7 by adding Ca 2+ . ,, …”

“…Micelles form at basic pH (counterions: Na + ) and undergo a wormlike-to-vesicle-to-lamellae transition 26,27. Crystalline fibers form from the micellar phase at pH > 7 by adding Ca 2+ 28,29,36.…”