Polyplexes relationships

Koping-Hoggard et al. [68] established the relationships between the structure and the properties of chitosan-pDNA polyplexes in vitro and in vivo. They compared polyplexes of ultrapure chitosan (UPC) of preferred molecular structure with those of polyethylenimine (PEI) polyplexes in vitro and after intratracheal administration to mice in vivo. UPC carriers were less cytotoxic than polyethylenimine (PEI) polyplexes and provided a better efficiency compared with that of commonly used cationic lipids. Low-molecular weight chitosan delivery systems were more efficient for cell transfection and less cytotoxic compared with PEL [65]. 

Scheme 15 (a) Stmcture-property-transfection relationships for imidazolium copolymers with controlled charge density and side chain hydroxyl number, (h) Cationic polymers electrostatically bind and condense anionic pDNA, forming a polyplex. Various factors, including hydrogen bonding, impact polyplex stability. Reprinted with permission from [107]. Copyright 2011 American Chemical Society... 

Unfortunately, in all these cases, there are nevertheless problems in defining clear structure-activity relationships and explaining the apparent discrepancies between the behavior of the polyplexes in vitro and their poor performance in vivo. It is highly probable that the actual morphology of the polyplexes deviates from the expected stmcture (core-shell, etc.). 

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