Electric Field Controlled Self‐Assembly of Hierarchically Ordered Membranes

Abstract

Self-assembly in the presence of external forces is an adaptive, directed organization of molecular components under nonequilibrium conditions. While forces may be generated as a result of spontaneous interactions among components of a system, intervention with external forces can significantly alter the final outcome of self-assembly. Superimposing these intrinsic and extrinsic forces provides greater degrees of freedom to control the structure and function of self-assembling materials. In this work we investigate the role of electric fields during the dynamic self-assembly of a negatively charged polyelectrolyte and a positively charged peptide amphiphile in water leading to the formation of an ordered membrane. In the absence of electric fields, contact between the two solutions of oppositely charged molecules triggers the growth of closed membranes with vertically oriented fibrils that encapsulate the polyelectrolyte solution. This process of self-assembly is intrinsically driven by excess osmotic pressure of counterions, and the electric field is found to modify the kinetics of membrane formation, and also its morphology and properties. Depending on the strength and orientation of the field we observe a significant increase or decrease of up to nearly 100% in membrane thickness, as well as the controlled rotation of nanofiber growth direction by 90 degrees, resulting in a significant increase in mechanical stiffness. These results suggest the possibility of using electric fields to control structure in self-assembly processes involving diffusion of oppositely charged molecules.

Co-assembly, spatiotemporal control and morphogenesis of a hybrid protein–peptide system

“…In this way, a closed membrane is formed that entraps the PA solution inside it and leaves the ELP solution outside. Self-assembled membranes formed at the interface between a solution of linear polyelectrolytes and a solution of either oppositely charged PAs [18][19][20][21][22] or surfactant molecules 23 have been reported. However, in our system, within the first minute of formation and on contact with any surface, the membrane spontaneously, yet controllably, adheres, focally opens and seals to the surface (Fig.…”

“…Strong electrostatic forces have been shown to drive the assembly of interfacial systems 18,22,23 . Zeta potential (ζ) measurements demonstrated that the ELP5 and PAK3 need to be oppositely charged to co-assemble into the dynamic system (Fig.…”

“…The different membrane structure and properties of ELPs/PAK2 systems are probably a result of a different molecular mechanism 22,27 compared with that of the ELP5/PAK3 system. These results demonstrate that the presence of the distinctive multilayered architecture is required for the controlled dynamic behaviours observed in the ELP5/PAK3 system.…”

Self-assembly of biomolecular soft matter

“…92 Since the membrane self-assembly mechanism is sensitive to osmotic pressure and ion flux, electric fields have been used to control membrane structure and growth rate. 93 …”

Peptide-based microcapsules obtained by self-assembly and microfluidics as controlled environments for cell culture

“…Examples of external inputs include mechanical forces, such as shear effects 5 , magnetic 6 and electric 7 fields, thermal gradients 8 and chemically 9 or topographically 10 patterned substrates. Although the concept of DSA still remains ambiguous, templated self-assembly (TSA) can be considered as a kind of DSA, in which a prefabricated ''template'' orients and directs the assembling components.…”