Polymersomes responsive

Polymersomes are, like any other vesicular structure, able to encapsulate hydrophilic, hydrophobic and amphiphilic molecules, but unlike other vesicular structure, their macromolecular nature makes them stronger and more stable with the intrinsic responsiveness of polymers. All these properties make polymersomes one of the most interesting supramolecular structures with potential applications in drug... 

Meng, F., Zhong, Z., Feijen, J., 2009. Stimuli-responsive polymersomes for programmed drug delivery. Biomaciomolecules 10, 197—209. 

Onaca, O., Enea, R., Hughes, D.W., Meier, W., 2009. Stimuli-responsive polymersomes as nanocarriers for drug and gene deUvery. Macromolecular Biosdences 9, 129—139. 

F. Meng, Z. Zhong, J. Feijen, Stimuli-responsive polymersomes for programmed drag delivery. Biomacromolecules 10 (2) (2009) 197-209. 

FIGURE 4.13 TEM of polymersomes at pH 3 (a) and 10 (b). Membrane consists of protonable poly(diethylaminoethyl methacrylate) (PDEAEM), which is responsible for the swelling/deswelling properties of pol3mersome. Source Gaitzsch et al. [32]. Reproduced with permission of John Wiley Sons. 

Due to its high stability, the membrane of polymersomes has low fluidity, which leads to a very limited ttansport through the membrane. Thus, in order to allow for transmembrane transport, specific efforts are necessary. One option is the use of responsive polymer blocks, which allow a switching of the block from hydrophilic to hydrophobic, or vice versa. This can be achieved with thermo-responsive poly(Af-isopropylacrylamide) (PNIPAM), pH-sensitive amino-functionalized methacryl derivatives (e.g., poly(diethylaminoethyl methacrylate) (PDEAEM)), or the redox-sensitive poly(propylene sulfide) (PPS). 

Another concept is the preparation of responsive polymersome membranes, which are further cross-linked for stabilization. This concept allows for preservation of the general polymersome capsule structure upon switching polarity but leads to a more leaky membrane structure, resulting in enhanced membrane transport (Fig. 6.5).This can be achieved by incorporating pH-sensitive blocks, for example, in photo-cross-linkable polymersomes. The membrane of the vesicle is then formed spontaneously as double layer at suitable pH from the block copolymer containing the photo-cross-linkable units and is subsequently cross-linked in the collapsed state. Upon acidification, the nonpolar blocks are protonated and transformed into a polar block. Therefore, the polymersome would like to disintegrate but is linked by chemical bonds, and... 

Another type of interaction is confinement. We focus on the confinement of block copolymers and the resulting microphase separation. As one example, the structure of polystyrene-h/oc -poly(methyl methacrylate) (PS-f>-PMMA) in the confinement of droplets in miniemulsions is described. To better understand microphase separation, experimental results are compared to self-consistent field theory simulations. Then, we consider block copolymers bound to a solid surfaces and their response to different environmental conditions (Sect. 5). As a third example of structures and confinement, the incorporation of quantum dots into the hydrophobic region of polymersomes is demonstrated. 

Phagocyte Stability Of particular importance is the assessment of the interaction of vesicles with the cellular components of blood, particularly granulocytes, which are the predominant circulating phagocytes. Neither adhesion nor stimulation of phagocytes are apparent when giant polymersomes are held in direct contact. When placed in contact with a white cell (Fig. 25b), vesicles do not exhibit any adhesion or other cellular response for up to 30 min, despite the presence of 20% plasma. In comparison, 1-2 min of contact between a yeast particle and a white cell (neutrophil leukocyte) leads to strong adhesion (49). 

Pig. 25. Exposure of a yeast cell (a) and a polymersome (b) to a white cell. The yeast cell is rapidly engulfed, whereas there is no response upon contact with the polymersome. From Ref. 49, with permission from John Wiley Sons, Inc. 

Another outstanding example of a stimuli-responsive polymersome was recently reported by van Hest and coworkers. It was demonstrated that polymersomes composed of a mixture of poly(ethylene glycol)-( -polystyrene and poly(ethylene glycol)-Z -poly(styrene boronic acid) become permeable in the presence of o-glucose or D-fructose, which bind to the poly(styrene boronic acid) segments and hence make them hydrophilic instead of hydrophobic (Figure 8). 

Kim KT, Comelissen JJLM, Nolte RJM, van Hest JCM. A polymersome nanoreactor with controllable permeability induced by stimuli-responsive block copolymers. Adv Mater 2009 21(27) 2787-91. 

Lomora M, Garni M, Itel F, Tanner P, Spulber M, PaUvan CG. Polymersomes with engineered ion selective permeability as stimuli-responsive nanocompartments with preserved architecture. Biomaterials 2015 53 406-14. 

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. ... 

Figure 1.8 Polymersomes generated by thermo-responsive polymers having hydrophobic and hydrophilic blocks in their chains.

Agut, W., Brulet, A., Schatz, C., Taton, D., Lecommandoux, S. (2010). pH and temperature responsive polymeric micelles and polymersomes by self-assembly of poly(2-(dimethyl-amino)ethyl methacrylate)-b-poly(glutamic acid) double hydrophilic block copolymers. 

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