Nondegradable polymers surface

Opsonization-induced polyplex disassembly during systemic circulation also represents a barrier to efficient cellular targeting. The instability of electrostatic polyelectrolyte assemblies means polyplexes are susceptible to polyanion displacement after cellular or chemical interaction, such as with erythrocytes or heparin, respectively. Increased levels of free polycations in the blood, and in particular high MW and nondegradable polymers, could induce adverse effects if excreted or broken down. However, there are numerous reports where surface modification of the polyplex with hydrophilic polymers leads to steric stability with reduction in disassembly during systemic circulation. " ... 

Also a new end point attachment of nondegraded glycosaminoglycan type 2 (HE) or regioselective modified heparin derivatives will be described the reducing end is oxidised by electrolysis and the aldonic acid lactone formed reacts with amino groups of the polymer surface. Also coatings by ionic immobilisation (HE, ES-HS) will be described. 

To bring the nanocontainer to a specific place where it should release its pay-load, targeting is a required approach. Hence, much work has been carried out to attach ligands or antibodies to the hydroxyl end-group of PEG-based assemblies [150,181,243], Biotinylated nondegradable block copolymer assemblies have been shown to attach to surfaces coated with the biotin receptor avidin [146,147, 150,244], Coupling chemistry has been applied to conjugate either an antihuman IgG, or antihuman serum to PEG-carbonate- or PEG-polyester-assembled polymer vesicles [149,245], HIV-derived Tat peptide attached to PEG-PBD polymersomes enhanced the cellular delivery of nanoparticles [246] and increased dendritic cell uptake in vitro [181]. 

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