Micelles and Vesicles Based on Cationic Polypeptides

A distinct characteristic of polypeptide-based micelles, with respect to those based on ordinary flexible polymers, is the intrinsic stiffness of the polypeptide chains, in particular if the chains are able to adopt a secondary structure such as an a-helix. This affects the self-assembly in various ways thus owing to the limited conformational entropy of the chain, the ability to accommodate effective chain packing is reduced. For the same reason, polypeptides are not able to gain significant conformational entropy when molecularly dissolved, which further stabilizes the formed nanostructures. Together with facilitated specific inter-chain interactions, this leads to a rich phase behavior. In particular, because of this rather pronounced stiffness, polypeptides have a natural tendency to self-assemble into vesicular 

The potential of temperature-responsive polymers to improve the endo-somal escape has also been demonstrated. In particular, if a temporary temperature decrease step is introduced in the transfection protocol, it is 

In spite of the interesting properties and exciting potential of polymeric vectors, two-thirds of the clinical trials carried out so far are still based on 

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The aim of this chapter is to give a brief selective overview of typical biomedical areas where cationic polymers can be employed. The use of cationic polymers in tissue engineering is a high priority topic in this chapter and several aspects on this phenomenon are given related to this is the potential of cationic hydrogels for medical and pharmaceutical applications. The importance of cationic polymers and copolymers as non-viral vectors in gene therapy is described, as well as how micelles and vesicles based on cationic polypeptides can form nanostructures by self-assembly. The potential of cationic polymers for drug delivery applications is also elucidated. 

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