Polymeric Micelles, Polymersomes, and Nanocapsules

Bio- and Multifunctional Polymer Architectures Preparation, Analytical Methods, and Applications, First Edition. Brigitte Voit, Rainer Haag, Dietmar Appelhans, and Petra B. Welzel. 

Active agent (e.g., drug, fluorescent dye) Targeting group (e.g., oligosaccharide) 

FIGURE 6.1 Formation and architecture of block copolymer micelles, which spontaneously form by self-assembly in water. The characteristic features are a pronounced core-shell architecture, which can be controlled by the individual polymer blocks. Typical examples for block copolymers are PEO-fc-PPO, PEO- -PCL, and PEO-fc-PAsp. Source Kataoka et al. [1], figure 1. Reproduced with permission of Elsevier. (See insert for color representation of the figure.) 

An important class of polymeric nanocarriers is based on nanocapsules with a polymeric membrane. As outlined earlier, in aqueous solutions, for example, of specific amphiphilic block copolymers above the CMC, self-assembly to spherical micelles takes place in the simplest case. However, depending on the polymer structure and architecture, block length, and hydrophilic/hydrophobic balance, the formation of more complex vesicular structures can also take place (see Section 5.1 Figs. 5.5a and 5.9). 

Besides cells, cell organelles and cellular vesicles are also surrounded by membranes, which are composed of a double layer formed by amphiphilic molecules. These amphiphiles are mostly phospholipids and therefore the resulting vesicles are called liposomes. Similarly, amphiphilic polymers can form a lipid-like double layer that forms the membrane of a polymeric vesicle, the so-called polymersome [4]. In contrast to micelles, the inner and outer parts of the membrane of polymersomes are in contact with water. 

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