Permeability polymersome membranes

The ability to encapsulate large aqueous volumes and consequently whatever is dissolved in it is one prerogative of polymersomes and represents their most promising ability. Nevertheless, while for hydrophobic and amphiphilic molecules the encapsulation process is more or less straightforward, the complex kinetics of polymersomes formations hampers the encapsulation of hydrophilic molecules. Clearly the most important parameter to consider in encapsulating water-soluble molecules is the polymersome membrane permeability. Early work carried out by Discher and co-workers [6] showed that the water permeability of PEO-PEE polymersomes was established by measuring the reduction in polymersome swelling as a function... 

The permeability of polymersome membranes for a given solute has been reported to be at least 10 times smaller compared to common phosphohpid membranes (8). Retention of encapsulants (eg dextrans, sucrose, physiological saline) over periods of months has been observed for small 100 nm polymersomes prepared by liposome-type extrusion techniques (49) as well as with 10 p.m giant vesicles. Permeability and membrane hydration have been shown to be inversely related to the bending modulus (165). It is suggested that membrane permeability and membrane hydration are related to the ability of the membrane to locally bend so as to create holes for solute permeation. 

Gaitzsch J, Appelhans D, Wang L, Battaglia G, Voit B. Synthetic bio-nanoreactor mechanical and chemical control of polymersome membrane permeability. Angew Chem Int Ed 2012 51(18) 4448-51. 

One of the first reported examples of a pore-solid support was the insertion of Aquaporin Z (AqpZ) into PMOXA-Z>-PDMS-Z>-PMOXA membranes to produce a membrane highly permeable to water, but not to other solutes. This work was based on a previous report by Meier and coworkers that showed the insertion of AqpZ into polymersome membranes. In similar studies, AqpZ was incorporated into polymer membranes on various supports, such as porous alumina and cellulose acetate, to produce biomimetic water channels. ... 

Polymeric vesicles, or polymersomes, are of interest for the encapsulation and delivery of active ingredients. They offer enhanced stability and lower permeability compared to lipid vesicles, and the versatility of synthetic polymer chemistry provides the ability to tune properties such as membrane thickness, surface... 

Some copolymers, such as PS-I -PIAT, self-assemble into polymersomes with an intrinsically porous membrane [78], whereas others require membrane permeabilization in order to form nanoreactors. For example, PMOXA- -PDMS- -PMOXA or PMOXA-fc-PDMS membranes are permeable to oxygen and reactive oxygen species [9], but not to small molecules [90-92], In the case of impermeable membranes, the following procedures can be used to provide accessibility (1) permeabilization by addition of organic solvents. 

Lomora M, Itel F, Dinu lA, Palivan CG. Selective ion-permeable membranes by insertion of biopores into polymersomes. Phys Chem Chem Phys 2015 17(24) 15538-46. 

Another bio-inspired approach is to design polymersomes as enclosed reaction compartments for the development of nanoreactors, nanodevices, or artificial organelles, in which active compounds are not only protected from the environment, but also allowed to act in situ. For such function, membrane permeability is of crucial importance, since it allows the exchange of substrates/products with the environment of the pol)maersomes. Various methods have been reported to generate polymersomes with permeable membranes (i) polymers forming intrinsically porous membranes, (ii) polymer membranes that are permeable to ions as e.g. specific oxygen species, (iii) pore formation in pH responsive polymer membranes by chemical treatment, (iv) polymer membrane permeabilization by UV-irradiation, and (v) biopores or membrane proteins inserted into polymer membranes. ... 

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