The influence of surface modification on the cytotoxicity of PAMAM dendrimers

The influence of surface modification on the cytotoxicity of PAMAM dendrimers was examined using Caco-2 cells. Dendrimers were modified by conjugating either lauroyl chains or polyethylene glycol (PEG) 2000 onto the surface of cationic PAMAM dendrimers (G2, G3, G4). The cytotoxicity of unmodified dendrimers towards Caco-2 cells was appreciably higher for cationic (whole generation) compared with anionic (half generation) dendrimers and for both types increased with increasing size (generation) and concentration. A marked decrease in the cytotoxicity of cationic PAMAM dendrimers was noted when the surface was modified, with the addition of six lauroyl or four PEG chains being particularly effective in decreasing cytotoxicity. This decrease in cytotoxicity is thought to be due to a reduction/shielding of the positive charge on the dendrimer surface by the attached chains. The cytotoxicity of dendrimer-based delivery systems is likely to be very different from the parent dendrimer.