Experimental procedure for preparation, vectorization and delivery of DNA-streptavidin nanogels (NGs) is schematically shown in Figure . The scaffold of the NGs constituted of multibiotinylated 3480 base pairs (bp) DNA (bt-DNA) was prepared by PCR as previously described. Crosslinking of the resulting bt-DNA was performed by adding streptavidin labeled with AlexaFluor633 fluorophore to give fluorescent NGs (NG-633) enabling their tracking and analysis by fluorescence. The resulting NGs had 114 ± 36 nm apparent diameter, as measured by Atomic Force Microscopy (Figure ). For vectorization of the NGs, cationic liposomes constituted of equimolar amounts of zwitterionic lipid DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and the cationic lipid DMAPAP (2-3-[bis-(3-amino-propyl)-amino]-propylamino-N-ditetradecyl carbamoyl methylacetamide) were used. In analogy with the formation of DNA-lipid complexes (lipoplexes), in our case the complexation of DNA-protein nanogel with lipids would give complexes containing DNA, lipids and proteins, which we named lipoproplexes (LPX). We thus investigated the interaction between NG-633 and DMAPAP/DOPE liposomes containing 5% of fluorescent DOPE labeled with fluorescein (FITC). First, the colloidal stability was assessed for the LPX-633 obtained at different charge ratios (R+/-) by fluorescence microscopy (Figure ). We considered the charge of the nanogels to be dependent only on the DNA component, as streptavidin was shown not to affect the zeta-potential of bt-DNA upon its folding into nanogels, and the charge concentration of the liposomes was calculated by considering the DMAPAP to have 3 positive groups at physiological pH. It was found that aggregation of the LPX occurred at R+/-higher than 1.5. We thus fixed the ratio R+/-= 1.5 and analyzed the resulting LPX by flow cytometry, a method which enables co-detection of different fluorophores within individual particles of nanometric size. The resulting dot-plots for NGs-633 only, FITC-labeled liposomes only and LPX-633 are given in the Figure . For NGs and liposomes, the dot plots demonstrate a higher fluorescence signal for AlexaFluor633 (71.96%) and FITC (75.99%) signals respectively. However, when NGs and liposomes were mixed together, a large population of particles demonstrating the signal from both fluorophores (86.34%) was detected, indicating successful complexation. The observation that the mean FITC fluorescence in the LPX decreased, while the mean AlexaFluor633 fluorescence increased can be explained either by FRET energy transfer between the fluorophores, or by change of their fluorescent properties in lipidic microenvironment, both further confirming binding between DNA-protein nanogels and cationic lipids leading to the efficient formation of the lipoproplexes.