Stabilization of polyamidoamine (PAMAM) dendrimers/sodium dodecyl sulfate complexes via PEGylation

Despite the robust structure of polyamidoamine (PAMAM) dendrimers, they are not stable when complexed with surfactants. Modification of PAMAM dendrimers by grafting PEG chains on the surface of PAMAM substantially improves its colloidal stability in the presence of sodium dodecyl sulfate (SDS). Michael addition reaction was employed to synthesize PEGylated-PAMAM by activating MPEG with 4-nitrophenylchloroformate. 1H NMR spectrum confirmed that 32 PEG chains were successfully grafted on the PAMAM surface, and the hydrodynamic radius of PEGylated-PAMAM was found to be ∼6.8 nm. The PEGylated-PAMAM dendrimers did not aggregate in the presence of up to 100 mM SDS as the complexes were sterically stabilized by PEG chains. ITC and zeta potential measurements revealed that the binding mechanism of SDS and PEGylated-PAMAM was induced by electrostatic interaction and polymer-induced micellization of SDS on PEG chains. The interaction of PEGylated-PAMAM and amphiphilic molecules, such as SDS was elucidated, and this provided a useful basis for the application PEGylated-PAMAM in drug delivery.