Water Gelation of an Amino Acid‐Based Amphiphile

Abstract

The water immobilization by a simple amino acid-containing cationic surfactant was investigated. A variety of techniques, such as (1)H NMR spectroscopy, circular dichroism (CD), steady-state fluorescence spectroscopy, and field-emission scanning electron microscopy (FESEM) were applied to determine the formation and architecture of the hydrogel. The new gelator with a minimum gelation concentration (MGC) of 0.3 % w/v shows prolonged stability and a low melting temperature (39 degrees C). (1)H NMR experiments revealed that intermolecular hydrogen bonding between the amide groups and pi-pi stacking of the indole rings are the two regulating parameters for gelation. Furthermore, fluorescence studies with 8-anilino-1-naphthalenesulfonic acid (ANS) as the probe indicate the participation of hydrophobicity during gelation. The luminescence study using both ANS and pyrene, along with FESEM results, indicate a critical concentration, well below the MGC, at which fibres begin to form. These cross-link further to give thicker fibers, leading to the formation of a hydrogel (0.3 % w/v). This new hydrogelator expresses high supramolecular chirality, as evidenced by the CD spectra. In addition, the gelator molecule was found to be nontoxic up to a concentration of 4 mM (0.2 % w/v). The high supramolecular chirality, prolonged stability, low melting point, and biocompatibility of the molecule make it a focus of chemical and biological interest.

Surfactant‐Stabilized Small Hydrogel Particles in Oil: Hosts for Remarkable Activation of Enzymes in Organic Solvents

“…In this work we utilized surfactant hydrogelators 1-4 (Scheme 1) having a wide range of minimum gelation concentrations (MGC) of 0.25-5.0 % (w/v) for entrapment of proteins. [16][17][18] Quaternary ammonium surfactants 1-4 form Scheme 1. Structure of the surfactant gelators.…”

“…Surfactants 1-4 were synthesized by following previously reported protocols. [16][17][18] Immobilization of proteins in the hydrogel matrix: The required amount (3.8-18.8 mg) of surfactants 1-4 was dissolved in Milli-Q water (60 mL) in a 100 mL round-bottom flask. Then, protein (15 mL) from a stock solution prepared with Milli-Q water was added to this solution to achieve the required amount of protein (0.125 to 3.0 mg) in the immobilization matrix.…”

“…[6b] Xu and coworkers subsequently showed improved enzyme activity of heme proteins (up to eightfold when encapsulated in low molecular weight two-component hydrogels) in organic solAbstract: Hydrogels of amino acid based cationic surfactant having C 16 tails were used to immobilize heme proteins and enzyme. These hydrogelentrapped proteins/enzyme showed remarkable activation when dispersed in organic solvent.…”

“…[16][17][18][19][20] The surfactant hydrogels were used to ensure that the entrapped protein enjoys the cumulative advantages of the supramolecular amphiphilic nanofibers compartmentalized in the milieu of water with huge interfacial area for the mass transfer. The hydrogel-immobilized enzymes showed striking activation in organic solvent.…”

Supramolecular Self-organization of Potential Hydrogelators on Attracting Surfaces

“…Van der Waals forces [15], hydrogen bonding [11,16], ionic bonding [17] and combination of these forces [18]. Another important factor for hydrogelling is the delicate hydrophilic/hydrophobic balance of the compounds.…”