The cationic
polymer poly(2-(dimethylamino)ethyl methacrylate) (p(
DMAEMA)) is able to efficiently bind and condense
DNA and to mediate transfection of a variety of cell types. In this study, fluorescence activated cell sorting (FACS), confocal
laser fluorescence microscopy (CSLM) and electron microscopy (EM) techniques were used to investigate in vitro the cellular interaction of p(
DMAEMA)-based polyplexes with human ovarian
carcinoma cells (OVCAR-3). Cellular association and subsequent internalization only occurred when the polyplexes exhibited a positive zeta potential. Small-sized polyplexes have an advantage over large-sized complexes regarding cellular entry. The effect of the presence of tertiary
amine groups versus the presence of quatenary
amine groups was evaluated by comparing p(
DMAEMA) with its quaternary
ammonium analogue
poly(2-(trimethylamino)ethyl methacrylate) (
p(TMAEMA)). The combined cellular interaction and transfection results suggest that the latter
polymer does not have an intrinsic endosomal escape property, in contrast to the '
proton sponge' effect proposed for p(
DMAEMA). PEGylation of p(
DMAEMA) effectively shielded the surface charge and yielded a notably lower degree of cellular interaction. Data on the effects of the presence of endocytosis inhibitors and an endosome-disruptive
peptide in the culture medium on the cellular interaction and transfection activity of p(
DMAEMA)-based polyplexes support endocytosis as being the principal pathway for intracellular delivery of plasmid. Both the CLSM and EM studies did not reveal the presence of polyplexes or plasmid outside the endocytic vesicles or within the nucleus, suggesting that intracellular trafficking from the endosomes to the nucleus is a very inefficient process.