Polymersomes, cross-linked

FIGURE 6,5 Schematic representation of polymersomes, with non-cross-linked and cross-linked membranes. Only in cross-linked polymersome membranes, transport can be reversibly activated upon polarity switch. (See insertfor color representation of the figure.)... 

Self-Beating Artificial Cells Design of Cross-Linked Polymersomes Showing Self-Oscillating Motion... 

Fig. 23. Deflation of a non-cross-linked (left) and a cross-linked polymersome (right). The latter deflates with dents and wrinkles, characteristic of a solid-like membrane. From Ref 168, with permission from the ACS Publications Division.

Grafe D, Gaitzsch J, Appelhans D, Voit B. Cross-linked polymersomes as nanoreactors for controlled and stabilized single and cascade enzymatic reactions. Nanoscale... 

Polymersomes generated from simple AB block copolymers display inter-digitated membrane. The robust entanglement within the hydrophobic layer can be considered as a physical cross-link able to enhance the mechanical properties of those aggregates compared to liposomes [5]. Tri-block (BAB) hydrophobic-hydrophilic-hydrophobic copolymers are similar to diblock copolymers since there... 

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... 

Encapsulation of enzymes in various polymer superstructures (dendrimers, polymersomes, PICsomes, or LbL capsules) provides significant advantages, such as higher stability and preserved catalytic activity over longer periods of time than bulk conditions. The process of encapsulation/entrapment of biomolecules in various 3D supramolecular assemblies should not affect the stability of the final nanoreactor structure (which is driven by the chemical nature of the copolymer used for their formation). If necessary cross-linking procedures can be used to increase the stability. However, it is also necessary to determine if... 

As amphiphilic block copolymers tend easily to form vesicles rather than tubes, Helmerson et al. reported another strategy for the formation of long polymer nanotubes. They started with polymersomes, which are cross-linked vesicles of amphiphilic block copolymers filled with water. Pulling on the membrane of those polymersomes with a micropipette or with optical tweezers led to the formation of water containing nanotubes stretched from the vesicles (Figure 5.46). However, this process required the application of a lot of force. To overcome this problem, they incorporated a detergent-like triblock copolymer in the formation of the polymersomes, with the effect that the membranes were rendered more fluid. 

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