Does Membrane Thickness Affect the Transport of Selective Ions Mediated by Ionophores in Synthetic Membranes?
Biomimetic polymer nanocompartments (polymersomes) with preserved architecture and ion-selective membrane permeability represent cutting-edge mimics of cellular compartmentalization. Here it is studied whether the membrane thickness affects the functionality of ionophores in respect to the transport of Ca2+ions in synthetic membranes of polymersomes, which are up to 2.6 times thicker than lipid membranes (5 nm). Selective permeability toward calcium ions is achieved by proper insertion of ionomycin, and demonstrated by using specific fluorescence markers encapsulated in their inner cavities. Preservation of polymersome architecture is shown by a combination of light scattering, transmission electron microscopy, and fluorescence spectroscopy. By using a combination of stopped-flow and fluorescence spectroscopy, it is shown that ionomycin can function and transport calcium ions across polymer membranes with thicknesses in the range 10.7-13.4 nm (7.1-8.9 times larger than the size of the ionophore). Thicker membranes induce a decrease in transport, but do not block it due to the intrinsic flexibility of these synthetic membranes. The design of ion selective biomimetic nanocompartments represents a new path toward the development of cellular ion nanosensors and nano-reactors, in which calcium sensitive biomacromolecules can be triggered for specific biological functions.
Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
Mihai
M
Lomora
Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
Ionel Adrian
IA
Dinu
Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
Fabian
F
Itel
Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
Serena
S
Rigo
Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
Mariana
M
Spulber
Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056, Basel, Switzerland.
Cornelia G
CG
Palivan
ionomycin; membrane thickness; polymersomes; selective membrane permeability