Effect of Surfactants on the Self-Assembly of a Model Elastin-like Block Corecombinamer: From Micelles to an Aqueous Two-Phase System

Recent advances in genetic engineering now allow the synthesis of protein-based block corecombinamers derived from elastin-like peptide sequences with complete control of chemistry and molecular weight, thereby resulting in unique physical and biological properties. The individual blocks of the elastin-like block corecombinamers (ELbcR's) display different phase behaviors in aqueous solution, which leads to the thermally triggered self-assembly of nano-objects ranging from micelles to vesicles. Herein, the interaction of cationic surfactant dodecyl trimethylammonium bromide (DTAB), anionic surfactant dodecyl sodium sulfate (SDS), and nonionic surfactant octyl-β-glucopyranoside (OG) with an ELbcR has been investigated by dynamic light scattering (DLS), the ζ potential and cryo-transmission electron microscopy (cryo-TEM). At 65 °C and neutral pH in aqueous solution, the ELbcR (E50A40) is associated into micelles with a diameter of 150 nm comprising a hydrophobic (A) core and a hydrophilic (E) anionic (from the glutamic acid residues) corona. The size of these self-assemblies can be controlled by adjusting the cosurfactant concentrations. Although the effects of surfactants on the self-assembly behavior of ELbcR's depend on the hydrocarbon chain length and headgroup of the surfactants, a general tendency to increase in size, which in some cases leads to flocculation and a phase-separated state, is observed. These results support the use of surfactants as a highly interesting means of controlling the self-assembly of ELbcR's in aqueous solution as well as their use in drug delivery and purification processes.