Sodium Monododecylphosphate Vesicles Formed in Alcohol/Water Mixtures

Graphical Sodium monododecylphosphate can form vesicles in alcohol/water mixtures. The vesicles show remarkable stability but are metastable in thermodynamics. Sodium monododecylphosphate (SDP), a typical single-chain amphiphile (SCA), exhibits extremely low solubility in water, which limits the investigation on its aggregation behavior. In the current work, we introduced short- and medium-chain alcohols into the SDP-water system to improve its solubility. An isotropic phase was found to be formed in the presence of alcohol with a suitable dielectric constant (11–25) or alkyl chain (2–7 carbons). In addition, vesicular, dendritic, and micellar structures were identified in the isotropic phase, depending on the composition of the SDP/alcohol/H 2 O ternary systems. The structure, stability, permeability, and formation mechanism of the vesicles formed in the SDP/ n -pentanol (NPT)/H 2 O system were investigated. The vesicles have a unilamellar structure, with size-selective permeability. They show remarkable stability upon long-term storage, exposure to high temperature, and freeze-thawing cycles, but are metastable in thermodynamics. The hydrogen bonding between SDP molecules plays an important role in the formation of vesicles. Furthermore, the SDP/NPT/H 2 O vesicles were used to construct three spatially segregated enzyme-loaded compartments to support a cascade enzyme reaction. The chemical signal transduction among the enzyme-loaded vesicles was achieved. This study provides a deeper understanding of the features of SDP vesicles and demonstrates their potential applications such as in biomembrane mimicking and micro-reactors.