We finally investigated whether the lipoproplexes could be used as carriers for an active enzyme, and if the enzyme would keep its catalytic activity after their delivery into the cells. For this purpose, bt-DNA was directly crosslinked in one step with commercially available streptavidin conjugated to alkaline phosphatase (ALP) enzyme (Figure ) to give functionalized nanogels (ALP-NGs). The formation of ALP-NGs was characterized by AFM imaging (Figures S11) and the concentration of streptavidin-ALP conjugate of 15 nM (for 1 μM of bt-DNA in phosphate groups) was selected for further experiments, giving an apparent diameter of 133 ± 41 nm (Figure ). This ratio of streptavidin-ALP to bt-DNA corresponds to up to 100 enzymes per nanogel. The complexation of non-fluorescent ALP-NGs with FITC-labeled liposomes was then confirmed by flow cytometry (Figure ). We observed that complexation with functionalized nanogels led to increase of mean fluorescence signal distribution of liposomes from the charge ratio R+/-= 0.75 (i.e. 0.5 µM liposomes for 2 µM bt-DNA). Such a low R+/-was thus sufficient for the formation of ALP-loaded lipoproplexes (ALP-LPX).