Mixed Cationic Surfactant Vesicles in (Dioctadecyldimethylammonium Bromide)/NaCl and (Dioctadecyldimethylammonium Chloride)/NaBr Aqueous Dispersions

Abstract

One of the most challenging characteristics not fully understood yet of the cationic surfactant salt dioctadecyldimethylammonium (DODA+) halide is concerned with the effects of the counterion (usually Br− and Cl−) on the surfactant assembly into vesicle structures in aqueous solution. These counterions play a key role in the self‐organization of DODA+ into bilayer structures. Differential scanning calorimetry (DSC) and dynamic light scattering (DLS) techniques were used here to investigate systematically the effects of the single salts NaCl and NaBr, respectively, on the thermal behavior and structural organization of the cationic dioctadecyldimethylammonium bromide and chloride (DODAB and DODAC) in water. The results undoubtedly indicate that the added Br− or Cl−, respectively, into DODAC and DODAB aqueous dispersions, replaces partially the bound counterions (Cl− and Br−) from the vesicles, yielding formation of DODAB/DODAC mixed vesicles. As a conclusion, single salts may be used to tune the thermal and structural characteristics of cationic vesicles.

Vesicle‐to‐micelle transition in aqueous mixtures of cationic lipids with Pluronic F127

“…According to Figure 4c, the melting enthalpy of 1.0 mM neat DODAC aqueous dispersion is Δ H m ≈ 50 kJ/mol in good agreement with the literature (Feitosa et al, 2000, 2019). The initial steep decrease of enthalpy to about 10 kJ/mol (stage I) at 0.1 mM F127 may indicate that the DODAC‐F127 interaction yields the formation of mixed vesicles with increasing amounts of bound F127, favoring the melting transition.…”

“…The formation of mixed vesicles and/or micelles in the CL‐F127 aqueous mixtures reported next is supported by comparing the profiles of the DSC thermograms for these samples with those for the neat compounds, which are well characterized by the DSC technique (Feitosa et al, 2000, 2019; Feitosa & Winnik, 2010).…”

“…The CLs considered here assemble easily as vesicle structures above their melting temperatures ( T m ) and are fairly stabilized even at temperatures below T m (Cocquyt et al, 2005; Feitosa, 2010; Feitosa et al, 2000; Feitosa, Karlsson, & Edwards, 2006; Saveyn et al, 2009). Up to about 1 mM, DODAC, DODAB, and DDAB assemble as unilamellar vesicles (Feitosa, 2010; Feitosa et al, 2009), whose characteristics may be tuned by the addition of small molecules, referred to as helpers, including single salts (Alves & Feitosa, 2008; Feitosa et al, 2019), surfactants (Feitosa, Bonassi, & Loh, 2006; Karukstis et al, 2003; Silvander et al, 1996), polymers or copolymers (Adati & Feitosa, 2015; Alves & Loh, 2012; Feitosa & Winnik, 2010), among others. As a disadvantage, CLs in general are toxic (Cui et al, 2018; Liang & Chou, 2009; Lv et al, 2006).…”

Reduction-Responsive Cationic Vesicles from Bolaamphiphiles with Ionizable Amino Acid or Dipeptide Polar Heads

“…Alternatively, in many cases, different cationic gemini surfactants have been used to prepare liposomes when mixed with phospholipids. , Another approach involved the synthetic modification of phosphatidylethanolamine with an l -lysine derivative . Monocomponent cationic vesicles can be formed with compounds that are not based in phospholipids such as deaqualinum, a bolaamphiphile with two terminal quinolinium units, , diC14-amidine, dioctadecyldimethylammonium bromide, derivatives of vernonia oil, N-[3-(dimethylamino)­propyl]-octadecanamide, a polypeptide grafted with a polycation, or gemini surfactants. , Also, quaternary ammonium surfactants − and amino acid-derived surfactants − sometimes evolve into vesicles in the presence of different species.…”