The study of polymer–surfactant interaction in catanionic surfactant mixtures

Kinetic stability of the oil-in-water emulsions and dynamic interfacial properties of mixtures of sucrose esters and polysaccharides

This article presents a study of the interfacial properties of oil-in-water emulsions containing sugar esters and polysaccharides. Sucrose fatty acid esters were synthesized using immobilized Candida antarctica lipase B. A yield of 53.4% was obtained using 2-methyl-2-butanol and 1:3 M ratio of sucrose:stearic acid. Equilibrium surface tension was 45 mN/m and low critical micellar concentration (CMC) value was obtained (ca. 10 mg/mL), characteristic of non-ionic surfactant. The interfacial properties of mixtures of sucrose esters and polysaccharides, at the oil-water interface were determined using a pendant drop tensiometer. Addition of polysaccharides increased the interfacial tension. Studies of interfacial viscoelasticity showed that the films were predominantly elastic. The presence of polysaccharides in emulsions resulted in flocculated droplets. All the emulsions presented great stability along 28 days with no creaming formation.

Electrophoretic NMR Characterization of Charged Side Chain Cationic Polyelectrolytes and Their Interaction with the Anionic Surfactant, Sodium Dodecyl Sulfate

Oppositely charged polymers and surfactants show a complex phase behavior with large regions of solubility and insolubility dependent on the concentrations of the species present. Here, a series of quaternized hydroxyethyl cellulose (cationic) polymers have been characterized by pulsed-gradient spin-echo NMR (PGSE-NMR) and electrophoretic NMR (eNMR) in simple aqueous (D₂O) solutions and in combination with the oppositely charged (anionic) surfactant, sodium dodecyl sulfate (SDS). Analysis of the effective charge on the polymer derived from both the eNMR and PGSE-NMR results yields a readily interpretable insight into the polymer behavior; the effective charge on the polymer at infinite dilution shows a linear relationship with the degree of modification. On addition of low concentrations of SDS, typically C_surf < 5 mM, the surfactant interacts with the charged polymers, leading to substantial changes in the dynamics of the system (polymer diffusion, viscosity). At these levels of surfactant addition, there is no macroscopic phase separation. Further, with the absence of an interaction with the parent, the uncharged polymer strongly suggests that the SDS only interacts with the charged moieties present on the functionalized side groups and not the polymer backbone. Ultimately, the charge on the soluble polymer/surfactant complex was found to depend linearly on the level of surfactant binding across a series of polymers with differing levels of modification with the charge becoming effectively zero at the macroscopic phase separation boundary.

Amphiphilic lipopeptide significantly enhances uptake of charge-neutral splice switching morpholino oligonucleotide in spinal muscular atrophy patient-derived fibroblasts

Splice-switching antisense oligonucleotides (SSOs) are emerging therapeutics with two SSOs recently approved by the FDA for Duchenne muscular dystrophy and spinal muscular atrophy. SSOs are administered without any delivery vector and require large doses to achieve the therapeutic benefit, primarily due to their poor cellular uptake. Although cell-penetrating peptides (CPP) have shown great potential in delivering SSOs into cells, their capacity as delivery vector is limited. Here we have studied the effect of lipid conjugation on the cell permeability of a known CPP (ApoE). Myristic acid was coupled at the N-terminus of ApoE to a C-terminal cysteine residue. The myristoylated ApoE (Myr-ApoE) was conjugated to a maleimide functionalised phosphorodiamidate morpholino oligonucleotide (PMO). The Myr-ApoE-PMO conjugate showed no cytoxicity and had significantly higher efficiency in cell permeability with 30% higher splice-switching activity compared to ApoE-PMO. The self-assembly properties of this amphiphilic lipopeptide-PMO conjugate was assessed. Transmission electron microscopy showed formation of nanoparticles with amphiphile behaviour and spherical structure. The self-assembly of Myr-ApoE-PMO into nanoparticles enabled it to better bind to cell membranes and to be more efficiently taken up by fibroblast cells. These results showed that modification of physico-chemical properties of peptides to produce peptide amphiphiles enhances cellular uptake and can be used as an efficient delivery vector for therapeutic SSOs.

Preparation of a new lignin-based anionic/cationic surfactant and its solution behaviour

The lignin-based cationic/anionic surfactant CA-SLs have a stronger ability to lower the surface tension at the air/water interface compared with SL–PEG, but a weaker one than CTAB.

The nature of fatty acid interaction with a polyelectrolyte-surfactant pair revealed by NMR spectroscopy

The interaction mechanisms of an oppositely charged polyelectrolyte-surfactant pair and dodecanoic (lauric) acid (LA) were experimentally investigated using a combination of nuclear magnetic resonance (NMR) techniques. It is observed that LA significantly affects the interaction between the anionic surfactant sodium dodecylethersulfate (SDES) and the cationic polymer guar modified with grafted hydroxypropyl trimethylammonium chloride (Jaguar C13 BF). Typically, oppositely charged polymers and surfactants interact electrostatically at a certain surfactant concentration known as the critical aggregation concentration (CAC). Once the polymer is neutralized by the surfactant, an insoluble complex (precipitate) is observed (phase separation), and, at concentrations beyond the surfactant critical micellar concentration (CMC'), the system returns to a one phase entity. In a system in which a mixture of SDES-LA is added to the polymer, NMR data show that below the neutralization onset, some of the polymer interacts with SDES, while some of the polymer is adsorbed at the surface of LA solid aggregates present in the system. Furthermore, SDES is found to aggregate in a lamellar-like structure at the polymer side chain prior to the SDES CMC'. Above the SDES (CMC'), LA is solubilized and incorporated at the palisade region of SDES micelles. Analysis of (1)H resonances provided estimated concentrations of all species in the system phases at all stages of interaction.