Poly(amido-amine)s: Biomedical Applications

Abstract

Poly(amido-amine)s (PAAs) are synthetic tert-amino polymers obtained by stepwise polyaddition of primary or secondary aliphatic amines to bis(acrylamide)s. Linear polymers are produced during the polymerisation of both primary mono(amine)s and secondary bis(amine)s. Under non-selective conditions primary bis(amine)s usually give crosslinked products upon reaction with bis(acrylamide)s, i. e., they react as tetrafunctional monomers. Furthermore, end-functionalised PAAs can be used to prepare block or graft copolymers, as well as crosslinked resins. PAAs can therefore be regarded as macromonomers as well. Generally, PAAs are soluble in water, chloroform, lower alcohols, dimethyl sulfoxide and other polar solvents (although amphoteric PAAs can only be dissolved in water). PAAs are degradable in aqueous solution by means of hydrolytic cleavage of the amidic bonds in their main chain that are activated by the tert-amino groups present in ?-position. A vast library of PAA structures has now been reported that are suitable for numerous material and biomedical applications. Here we review the synthesis, characterisation and current biomedical uses of PAAs. Their use as heavy-metal-ion-complexing polymers, and polymers for heparin neutralisation in solution, fabrication of heparin-absorbing resins and heparinisable materials is discussed. As amphoteric PAAs are biocompatible and biodegradable polymers that moreover display intelligent stealth properties, they are currently under development as PAA/anticancer conjugates and non-viral vectors for intracytoplasmic delivery. The potential of this unique chemistry is reviewed.