Proton Transport from Dendritic Helical‐Pore‐Incorporated Polymersomes

Abstract

The ability to add synthetic channels to polymersome (polymer vesicle) membranes could lead to novel membrane composites with unique selectivity and permeability. Proton transport through two different synthetic pores, self‐assembled from either a dendritic dipeptide, (6Nf‐3,4‐3,5)12G2‐CH2‐Boc‐L‐Tyr‐L‐Ala‐OMe, or a dendritic ester, (R)‐4Bp‐3,4‐dm8G1‐COOMe, incorporated into polymersome membranes are studied. Polymersomes provide an excellent platform for studying such transport processes due to their robustness and mechanical and chemical stability compared to liposomes. It is found that the incorporated dendritic dipeptide and dendritic ester assemble into stable helical pores in the poly(ethylene oxide)‐polybutadiene (PEO‐PBD) polymersomes but not in the poly(2‐methyloxazoline)‐poly(dimethylsiloxane)‐poly(2‐methyl oxazoline) (PMOX‐PDMS‐PMOX) polymersomes. The incorporation is confirmed by circular dichroism (CD), changes in purely synthetic mechanical strength (e.g., areal expansion modulus) as assessed by micropipette aspiration, and cryo‐TEM. In addition to the structural analyses, a transport measurement shows the incorporated dendritic helical pores allow facile transport of protons across the polymersome membranes after up to one month of storage. This integration of synthetic porous channels with polymersome substrates could provide a valuable tool for studying active transport processes in a composite membrane. These composites will ultimately expand the family of biologically inspired porous‐membrane mimics.

Recent trends in the tuning of polymersomes’ membrane properties

“…The authors proposed an explanation based on the better solubility and stability of dendritic ester in the bilayer compared to the dendritic dipeptides. Another possibility could be proton hopping across the peptide system which could inhibit transport of protons in the dendritic dipeptide pores [97]. It is interesting to note that, unlike all the previous cited works about the incorporation of channel membrane proteins in PMOXA-b-PDMS-b-PMOXA triblock copolymer vesicles, this study on dendritic helical pore incorporated polymersomes has been realized on PBut-b-PEO diblock copolymer (M n = 3800 g/mol).…”

“…As an alternative to natural channel protein, dendritic dipeptides and dendritic esters have been shown to self-assemble into helical pores in polymersomes' membranes made from the self-assembly of poly(butadiene)-block-poly(ethylene oxide). Their function was evaluated by proton transfer experiments [97]. Proton transport was evidenced using a pH-sensitive fluorescent dye (8-hydroxypyrene-1,3,6 trisulfonic acid) (HPTS) loaded in polymersomes and a precise controlled addition in the vesicle's suspension of NaOH or HCl to modulate pH in the extra-vesicular medium.…”

“…It is obvious that the incorporation of different components in a membrane can only be advantageous if these components bring specific properties without modifying other functional or physical properties of the membrane. The first relevant parameter to consider is the mechanical stability of the "modified" membrane, often evaluated by micropipette aspiration techniques on giant vesicles (∼ 20 μm diameter) [97]. The vesicle areal strain was measured and plotted versus the applied membrane tension and compared to the unloaded polymersomes.…”

Synthesis and Self-Assembly of Bundle-Forming α-Helical Peptide–Dendron Hybrids

“…7d Functional supramolecular materials such as organogels, 7a,7b porous channel protein mimetics, 8-9 and switchable channels 7c illustrate the advantages of hybrid materials to address long-standing challenges in supramolecular materials. These abiotic materials can perform biological functions in biologically relevant environments, 8,10 and have inspired curiosity about the origins of homochirality in nature. 9h,13,14 …”

Photo‐controlled Hierarchical Assembly and Fusion of Coumarin‐containing Polydiacetylene Vesicles

“…[ 5 ] Hammer and Ryan et al realized the aggregation of polymersomes through inter-vesicular hydrophobic interactions or avidin-biotin recognitions. [ 6 ] In this communication, the reversible assembly and disassembly of polydiacetylene (PDA) based vesicles has been realized through photo-controlled dimerization and cleavage reactions of the coumarin groups within the surface of adjacent vesicles. Furthermore, compared with the large number of articles on membrane fusion of liposomes and block copolymer vesicles, studies on photo-triggered fusion of polymerized vesicles have seldom been reported.…”