We then checked if ALP enzyme kept its catalytic activity within the lipoproplexes in vitro. For the assay, 9H-(1,3dichloro-9,9-dimethylacridin-2-one-7-yl) phosphate, diammonium salt (DDAO-P) fluorogenic substrate was used to follow the hydrolysis of its phosphate moieties by alkaline phosphatase via appearance of far-red fluorescence emission of the resulting DDAO. We found that incorporation of the ALP into the nanogels only slightly decreased the catalytic activity of the enzyme to 88% (Figure ). Adding liposomes to the ALP alone did not affect its activity, whereas within ALP-loaded lipoproplexes the enzyme conserved 79% of its initial catalytic activity, as compared to the activity of the native ALP-streptavidin conjugate. The ALP enzyme thus stayed available to the DDAO-P substrate and catalytically active even after loading into the DNA nanogels and their complexation with cationic lipids.