Kinetics of Induced Vesicle Breakdown for Cationic and Catanionic Systems

Abstract

Cationic and catanionic surfactant vesicle systems have been perturbed by addition of a single-chain surfactant to take the system from a vesicle-stable region to a micelle-stable region. The first vesicle system is based on a double-chain cationic surfactant cetyldecyldimethylammonium bromide (C16C10DMABr) and the second vesicle system is based on a mixture of anionic and cationic single-chain surfactants, namely, sodium octyl sulfate (SOS) and cetyltrimethylammonium bromide (CTAB). In both systems, vesicle breakdown will involve the initial incorporation of the single-chain surfactant into the vesicle, followed by subsequent disintegration of the vesicle. The progress of reaction has been observed by monitoring turbidity changes using a stopped-flow or conventional spectrophotometer. The rate of breakdown of vesicles was found to be linearly dependent on the concentration of added single-chain surfactant, which provides the driving force for the breakdown reaction. The breakdown reaction rates could be changed by factors up to 100 by adjusting the concentration of the solutions.

Stabilization of Catanionic Vesicles via Polymerization

“…The breakdown of vesicles upon addition of excess single chain surfactant is quite fast (typical τ break ∼ 0.1 s), as compared with the vesicle formation process (tens or hundreds of seconds). This is in agreement with the results presented by Robinson et al 22 Characterization of Polymerized Catanionic Vesicles. Free radical polymerization was carried out on aqueous mixtures of MOTB and MOBS at molar ratios of MOTB/MOBS ) 7/3 or 4/6 and a total concentration of 27 mM (Figure 3).…”

“…The almost linear increase of the rate constant with increasing MOTB/MOBS molar ratio indicates that the driving force for vesicle breakdown is the addition of excess of MOTB, which transforms the vesicle into mixed micelles. 22 It is quite understandable that the larger the driving force, the faster the transition from vesicles to mixed micelles. The breakdown of vesicles upon addition of excess single chain surfactant is quite fast (typical τ break ∼ 0.1 s), as compared with the vesicle formation process (tens or hundreds of seconds).…”

“…21 Additional work by Robinson et al showed that the breakdown of SOS/CTAB vesicles linearly depended on the concentration of the added single-chain surfactant. 22 The instability of catanionic vesicles and other self-assembled structures upon changes in solution conditions has also prompted our continual studies on the structural fixation of these nanostructures made of surfactants and amphiphilic block copolymers. [29][30][31][32][33][34][35] The covalent fixation of the vesicular bilayer microstructure via polymerization can lead to enhanced stability of the vesicles and also adjusts the bilayer permeability.…”

Fine-tuning of POPC liposomal leakage by the use of β-cyclodextrin and several hydrophobic guests

“…The leakage is a complex process, due to the polydispersity of the liposomes and the necessarily multistep nature of the process. However, the observed kinetic profiles (typical examples are reported in Figure 3) follow a first-order decay and, according to a phenomenological approach (Bucak et al, 2002), Equation 2 can be written as follows:…”

Effects of interactions on the formation of mixed micelles of 1,2-diheptanoyl-sn-glycero-3-phosphocholine with sodium dodecyl sulfate and dodecyltrimethylammonium bromide

“…In the human digestive tract, phospholipids form mixed micelles with bile salts and are hydrolyzed by the phospholipase enzymes [3][4][5]. Although several studies exist on the mixed micelle formation between conventional surfactants and long chain phospholipids upon a breakdown of the vesicular structures [6][7][8][9], little is known about direct mixed micelle formation between phospholipids and detergents. Hence, it is important to elucidate the nature of mixed micellization on the basis of different categories of the surfactants.…”