Fabrication and enzymatic dissociation of long-chain alkanoylcholine-based worm-like micelles

Abstract

In order to elucidate the possibility of the formation and enzymatic dissociation of worm-like micelles (WLMs) from long-chain alkanoylcholines (LCACs), strategies of fabrication and butyrylcholine esterase (BChE)-catalyzed dissociation of LCAC-based WLMs have been developed. Three LCACs with different hydrophobic tail lengths, namely dodecanoylcholine bromide (DCB), myristoylcholine bromide (MCB), and palmitoylcholine bromide (PCB), have been used as model cationic surfactants. It was demonstrated that the hydrophobic tail length of an LCAC played an important role in the formation of WLMs. With the assistance of sodium salicylate (NaSal), DCB proved to be incapable of efficiently forming WLMs, whereas MCB and PCB performed well. PCB-based WLMs have also been fabricated with the aid of NaNO3. To fabricate WLMs at a surfactant concentration of 0.1 mol L−1, the optimal molar ratio of the additive (NaSal and NaNO3) to the surfactant (MCB and PCB) was around 0.83 (NaSal/MCB), 0.63 (NaSal/PCB) and 20 (NaNO3/PCB), respectively. The respective average diameters of the WLMs were about 4.11 nm (MCB-NaSal), 4.82 nm (PCB-NaSal), and 4.51 nm (PCB-NaNO3). Meanwhile, the respective zero-shear viscosities of the WLMs were about 5.38 × 102 mPa s (MCB-NaSal), 1.81 × 105 mPa s (PCB-NaSal), and 7.35 × 104 mPa s (PCB-NaNO3). Jelly-like PCB-NaSal and PCB-NaNO3 WLMs underwent efficient dissociation through a BChE-catalyzing strategy under mild conditions of pH 7.4 and 37 °C. Its chemical principle was a hydrolysis reaction of PCB catalyzed by BChE.