Lipid bilayers with sheet-like dynamic assemblages of amphiphilic molecules are among the basic biological components. A bilayer functions like a barrier between ions and molecules. The layer also acts like a soft membrane for organelles and cells in the body. However, various membrane proteins may be used to add to the bilayers molecular transport functionality. The obtained lipid layer would allow the membrane to experience biological modification such as cell division.
Motivated by the functionality of the lipid bilayers, most researchers have proposed a number of artificial materials with synthetic and biological lipid bilayers. Most of these functional materials are helpful for drug-delivery, bio sensing, and gel composite applications.
Researchers led by Professor Jian Ping Gong from the Hokkaido University in Japan analyzed the induced swelling and contraction as well as the quasi one-dimensional diffusion of poly (dodecyl glyceryl itaconate) gel forming into string-like shapes. The gels were synthesized using a gel precursor solution through suction into a polyethylene tube. Their work is published in Polymer.
The authors prepared the gels from a precursor solution by sucking the solution into a polyethylene tube using a plastic syringe. They tried to keep the flow rate as high as possible in a bid to induce bilayer orientation. This was followed by a co-current polymerization of the dodecyl glyceryl itaconate and acrylamide using UV light irradiation. The authors then removed the gels from the tube.
The gels were swollen in water for about one week after which they were cut into 1cm long pieces. The authors measured the length and diameter of the samples before and after swelling for one week. From the obtained values, they were able to compute volume swelling ratios and radial and axial expansions of the specimens.
Methylene blue was used in the experiments as the main reagent to analyze the diffusion behavior of the gels swollen in water. The authors determined the radius of the methylene blue molecule in pure water. This was approximately 0.3nm.
They also observed that when the supramolecular, anisotropic hydrogel was immersed in water, there was a unique expansion and contraction along its axes. The behavior was mainly due to its absorption attributes. Moreover, they noticed that the diameter as well as the volume of the gel expanded 2.0 and 1.6 times respectively. After swelling, the length of the gel contracted to approximately 0.77 times of its length before swelling.
The authors proposed that the swelling of the gels was mainly due to competition of isotropic elasticity of the hydrogels and the osmotic pressure differences between the bath solutions and the gels. When aqueous solution was added to the bath solution, there was an increase in the osmotic pressure, which then suppressed the swelling of the gels.
The research team managed to fabricate supramolecular, anisotropic hydrogels with ring-like lamellar bilayers which were embedded into polyacrylamide matrix. The observed swelling-induced contraction behavior will be helpful for the design of future actuators.
Kei Mito1, Md. Anamul Haque2,3, Tasuku Nakajima2,4, Maki Uchiumi5, Takayuki Kurokawa2,4Takayuki Nonoyama2,4, and Jian Ping Gong2,4. Supramolecular hydrogels with multi-cylindrical lamellar bilayers: Swelling-induced contraction and anisotropic molecular diffusion. Polymer (2017), https://doi.org/10.1016/j.polymer.2017.01.038.Show Affiliations
- Graduate School of Life Science, Hokkaido University, N10W8, Kita-ku, Sapporo, 060-0810, Japan
- Faculty of Advanced Life Science, Hokkaido University, N21W11, Kita-ku, Sapporo, 001-0021, Japan
- Department of Chemistry, University of Dhaka, Dhaka, 1000, Bangladesh
- Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan
- School of Science, Hokkaido University, N10W8, Kita-ku, Sapporo, 060-0810, Japan
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