Size-Selective Permeation of Water-Soluble Polymers through the Bilayer Membrane of Cyclodextrin Vesicles Investigated by PFG-NMR

Abstract

Cyclodextrin vesicles (CDVs) consist of a bilayer of amphiphilic cyclodextrins (CDs). CDVs exhibit CD cavities at their surface that are able to recognize and bind hydrophobic guest molecules via size-selective inclusion. In this study, the permeability of α- and β-CDVs is investigated by pulsed field gradient-stimulated echo (PFG-STE) nuclear magnetic resonance. Diffusion experiments with water and two types of water-soluble polymers, polyethylene glycol (PEG) and polypropylene glycol (PPG), revealed three main factors that influence the exchange rate and permeability of CDVs. First, the length of the hydrophobic chain of the CD amphiphile plays a crucial role. Reasonably, vesicles consisting of amphiphiles with a longer aliphatic chain are less permeable since both membrane thickness and melting temperature T(m) increase. Second, the exchange rate through the bilayer membrane depends on the molecular weight of the polymer and decreases with increasing weight of the polymer. Most interestingly, a size-selective distinction of permeation due to the embedded CDs in the bilayer membrane was found. The mechanism of permeation is shown to occur through the CD cavity, such that depending on the size of the cavity, permeation of polymers with different cross-sectional diameters takes place. Whereas PPG permeates through the membrane of β-CD vesicles, it does not permeate α-CD vesicles.

WITHDRAWN: Ionic liquid mixtures with tunable physicochemical properties

“…The effect of the mole composition on the ion mobility of the pyrrolidinium binary mixtures is more evident in Figure 3 and also reported in can show bi-exponential behavior and, therefore, leading to two different diffusion coefficients [40][41][42]. Otherwise, for the PYR 14 -PYR 18 mixtures, attenuation for the signals 3 and 6 can be better described as mono-exponential ( Figure 5).…”

Reversible Stabilization of Vesicles: Redox‐Responsive Polymer Nanocontainers for Intracellular Delivery

“…This observation is supported by TEM (Figure 2c,d, S8) and AFM (Figure 2e,f,S9) images.In all cases,PSV SS appear as circular objects commonly observed for polymer stabilized vesicular structures [29,30] and this shape was fully preserved after treatment with TCEP.AFM images also reveal that the PSV SS collapse into flattened objects after deposition on Mica substrates,w hich is consistent with their hollow morphology. [31] Hence,t he accelerated, TCEP-triggered release likely results from an enhanced permeability of the highly dynamic cyclodextrin amphiphile bilayer [23,32] caused by the lack of stabilization from the cleaved polymer shell. An intact crosslinked polymer shell, on the other hand, significantly restricts dynamics in the cyclodextrin bilayer and thereby decreases permeability of the supramolecular assembly.…”

“…In line with this trend, ar eduction by 50 %p roduced insufficient stabilized PSV SS releasing almost all dye during gel filtration (CF/amphiphile < 0.1 mol mol À1 ;F igure S6). [31] Hence,t he accelerated, TCEP-triggered release likely results from an enhanced permeability of the highly dynamic cyclodextrin amphiphile bilayer [23,32] caused by the lack of stabilization from the cleaved polymer shell. The hydrodynamic diameter of PSV SS did not change upon TCEP treatment ( Figure S7), indicating that the supramolecular structure maintains the original morphology of avesicle core with at hin polymer shell.…”

Cyclodextrin-based switchable DNA condenser

“…In this system, the polycationic structure of 1 or 2 facilitates their good DNA condensation ability. In the presence of base or enzyme, carboxylate anions resulting from the cleavage of esters can 35 neutralize the imidazolium cations on β-CD to form zwitterions that show lower toxicity towards biotic tissue [16] . Possessing a cationic β-CD head and seven hydrophobic tails, 40 1 or 2 may have the tendency to self-aggregate in water [17] .…”

“…Significantly, these β-CD derivates present good DNA 35 condensation abilities, and their DNA condensation abilities can be switched by base, enzyme and physiological condition. In addition, the length of hydrophobic tethers is found able to affect not only the DNA condensation ability but also the stability of β-CD-based DNA condensers.…”