Chitosan as a Representative Example

PEGylated chitosan nanoparticles were shown to enhance insulin absorption to a greater extent compared with non-nanoparticulate forms of chitosan and insulin alone. Chitosan nanoparticles were also found to enhance nasal absorption of insulin in rabbit, regardless of chitosan molecular weight. Recently, Al-Qadi and co-workers reported that intratracheal administration of diy insulin powder microencapsulated in chitosan nanoparticles increased its distribution to the deep lungs, and facilitated release of a biologically active form of insulin to rat blood. Moreover, they observed a more pronounced and prolonged effect compared to non-formulated insulin.  

Uptake via the nasal cavity to the brain, thereby bypassing the blood/brain barrier, can be improved using absorption enhancers and transporters such as chitosan nanoparticles.For example, Vaka and co-workers showed a 14-fold increase in rats in the bioavailability of intranasally administered NGF, a protein for the treatment of neurological diseases such as Alzheimer s, with chitosan compared to the formulation without chitosan. 

Also chitosan-6-mercaptonicotinic acid was used to encapsulate insulin into nanoparticles. After oral administration to rats, glucose tolerance in the body improved fourfold compared to unmodified chitosan nanoparticles. 

While chitosan represents one of most frequently employed polymers to form mucoadhesive drug delivery carriers, alternatives have also been developed, of which the class of poly(amidoamine)s is a representative example. 

Poly(amidoamine)s (PAAs) can be easily synthesized by Michael-type polyaddition of primary or bis-secondary amines to give bis(aciylamide)s. These polymers are water soluble, biodegradable and biocompatible, and show significantly lower cytotoxicity than other usual polycationic vectors ( 100-fold less toxic than PAAs have the advantage of degrading to 

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