Supramolecular design of biocompatible nanocontainers based on amphiphilic derivatives of a natural compound isosteviol

Abstract

Two diterpenoid surfactants with ammonium head groups and bromide (S1) or tosylate (S2) counterions have been synthesized. Exploration of these biomimetic species made it possible to demonstrate that even minor structural changes beyond their chemical nature may dramatically affect their solution behavior. While their aggregation thresholds differ inconsiderably, morphological behavior and affinity to lipid bilayer are strongly dependent on the counterion nature. Compound S2 demonstrates properties of typical surfactants and forms small micelle-like aggregates above critical micelle concentration. For surfactant S1, two critical concentrations and two types of aggregates occur. Structural transitions have been observed between small micelles and aggregates with higher aggregation numbers and hydrodynamic diameter of ca. 150 nm. Unlike S2, surfactant S1 is shown to integrate with liposomes based on dipalmitoylphosphatidylcholine, resulting in a decrease of the temperature of the main phase transition. Both surfactants demonstrate an effective complexation capacity toward oligonucleotide (ONu), which is supported by recharging the surfactant–ONu complexes and the ethidium bromide exclusion at a low N/P ratio. Meanwhile, a very weak complexation of plasmid DNA with the surfactants has been revealed in the gel electrophoresis experiment. The DNA transfer to bacterial cells mediated by the surfactant S1 is shown to depend on the protocol used. In the case of the electroporation, the inhibition of the cell transformation occurs in the presence of the surfactant, while upon the chemical treatment no surfactant effect has been observed. The variability in the morphology, the biocompatibility, the nanoscale dimension and the high binding capacity toward the DNA decamer make it possible to nominate the designed surfactants as promising carriers for biosubstrates or as a helper surfactant for the mixed liposome–surfactant nanocontainers.