(568h) Highly Permeable Artificial Water Channels in Block Copolymer Membranes

Authors: 
Shen, Y., University of California
Ren, T., Pennsylvania State University
Kumar, M., The Pennsylvania State University

Highly permeable artificial water channels in block copolymer
membranes

 

Yue-xiao
Shen, Tingwei Ren, Manish Kumar*

Department
of Chemical Engineering, Pennsylvania State University, University Park, PA, 16802

*Corresponding
author: 155 Fenske Laboratory, Pennsylvania State University, University Park,
PA, 16802, (814) 865-7519, manish.kumar@psu.edu

 

We have reported that peptide-appended
pillar[5]arene (PAP) artificial water channels (Fig. 1) combine the advantages
of biological water channels Aquaporins (AQPs) and carbon nanotubes (CNTs).1 It can be
synthesized using simple chemistry at gram scale in the lab and provide stable
structure and good solvent compatibility. The water conductance of PAP is in
the range of AQPs. It can also be vertically aligned in lipid membranes, with much
higher packing density than current synthetic CNTs-based membranes.

Although the initial
testing of the PAP channels was conducted in lipid systems, this is not an
ideal format for commercial separation materials. We continue to investigate
the functionality of these channels in block copolymer (BCP) membranes. BCPs,
with lipid-like structures, are most commonly synthesized for biomimetic
applications because of the advantages of BCPs membranes including high
mechanical and chemical stability,2,3 low water and
gas permeability4 and
customizable properties (e.g., a larger range of membrane thickness2 and end
groups5). We are
testing a series of poly(butadiene)-b-poly(ethylene oxide) (PB-PEO) diblock
copolymers with different block length. These BCPs have different hydrophobicities
and thicknesses compared to lipids, and been shown to functionally incorporate
water channel proteins aquaporin 0,6 potassium
channel7 and
¦Á-hemolysin.8

The PAP channels
can be incorporated into PB-PEO BCP membranes using the film rehydration
method. The number of channels per vesicle was measured based on a fluorescence
correlation spectroscopy (FCS) technique.9 We
combined the channel number data and permeability data using stopped-flow light
scattering technique (Fig. 2A and 2B) and obtained the single channel water
permeability in PB23-PEO16 vesicles (1.5¡À0.4´108 H2O
molecules per second). This value is close to that in lipid system (3.7¡À0.6´108 H2O
molecules per second, Fig. 2C).1 In the
future, we will systematically test the PAP channels in different BCPs systems,
visually confirm the incorporation in giant unilamellar vesicles and discuss
the interaction of different BCPs and the PAP channels. We will also plan to
use fluorescence recovery after photobleaching (FRAP) technique to determine
the diffusion coefficient of the PAP channels in lipid and BCPs bilayers and
expect these results can provide insights into to maximizing the channel¡¯s
packing density in BCP membranes.

Reference

1          Shen,
Y.-x. et al. Highly permeable artificial water channels that can
self-assemble into two-dimensional arrays. Proc. Natl. Acad. Sci. U.S.A.
112, 9810-9815, (2015).

2          Discher,
D. E. & Eisenberg, A. Polymer Vesicles. Science 297, 967-973,
(2002).

3          Discher,
B. M. et al. Polymersomes: Tough Vesicles Made from Diblock Copolymers. Science
284, 1143-1146, (1999).

4          Kumar,
M. et al. Highly permeable polymeric membranes based on the incorporation
of the functional water channel protein Aquaporin Z. Proc. Natl. Acad. Sci.
U.S.A.
104, 20719-20724, (2007).

5          Rakhmatullina,
E. & Meier, W. Solid-Supported Block Copolymer Membranes through
Interfacial Adsorption of Charged Block Copolymer Vesicles. Langmuir 24,
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6          Kumar,
M. et al. High-Density Reconstitution of Functional Water Channels into
Vesicular and Planar Block Copolymer Membranes. J. Am. Chem. Soc. 134,
18631-18637, (2012).

7          Kowal,
J. Ł. et al. Functional surface engineering by nucleotide-modulated
potassium channel insertion into polymer membranes attached to solid supports. Biomaterials
35, 7286-7294, (2014).

8          Zhang,
X. et al. Natural channel protein inserts and functions in a completely
artificial, solid-supported bilayer membrane. Sci. Rep. 3,
(2013).

9          Erbakan,
M. et al. Molecular Cloning, Overexpression and Characterization of a
Novel Water Channel Protein from Rhodobacter sphaeroides. PLoS ONE
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