Welldefined dendrimer

poly(amido-amine) dendrimer (PAMAM)

was surface engineered via biomimetic phosphorylcholine(PC) to achieve a potential biocompatible candidate for gene delivery.PAMAM dendrimer is proven to be an efficient gene carrier itself

but it is associated with certain problems such as low water solubility and considerable cytotoxicity.PC-based polymers were designed with mimicking the biomembrane structure and widely used to improve the biocompatibility of various medical devices.Surface modification of PAMAM via phosphorylcholine is conceived to improve the biocompatibility of PAMAM.Generation 5.0 PAMAM dendrimer (G5) has been synthesized by divergent method with ethylenediamine as core.The surface of PAMAM was conjugated with PC groups via the Michael addition reaction between the 2-acryloyloxyethyl phosphorylcholine (APC) and the primary amines located on G5-After dialysis in distilled water and lyophilization

the PC modified PAMAM G5 (G5-PC) was obtained.The success of the PC modification of PAMAM was followed with FTIR and  1H-NMR characterigzation.The average primary amino group numbers of the G5 and G5-PC were followed through 1H-NMR and potentiometric titration.While there were 106 primary amine groups on the native PAMAM

the surface modification of PAMAM resulted in approximately 50 PC groups on the G5-PC and 56 primary amine groups were remained.Cell viability tests and morphology observation indicated that the cytotoxicity of G5-PC was much lower in ECV304 cell lines in comparison with that of native PAMAM G5.The biomimetic PC modification sufficiently improved the biocompatibility of the native G5.The surface charges of the G5 and G5-PC were measured via zeta potential measurements

and their zeta potentials were +22.4 and +33.4 mV

respectively.The positive surface charges allowed the G5-PC to form complexes with DNA as indicated by particle size analysis.These results suggested that the biomimetic phosphorylcholine surface engineered poly(amido-amine) dendrimers could be an excellent biocompatible candidate for gene delivery systems.