PEGylated and Functionalized Aliphatic Polycarbonate Polyplex Nanoparticles for Intravenous Administration of HDAC5 siRNA in Cancer Therapy

Guanidine and morpholine functionalized aliphatic polycarbonate polymers are able to deliver efficiently histone deacetylase 5 (HDAC5) siRNA into the cytoplasm of cancer cells <i>in vitro</i> leading to a decrease of cell proliferation were previously developed. To allow these biodegradable and biocompatible polyplex nanoparticles to overcome the extracellular barriers and be effective <i>in vivo</i> after an intravenous injection, polyethylene glycol chains (PEG<sub>750</sub> or PEG<sub>2000</sub>) were grafted on the polymer structure. These nanoparticles showed an average size of about 150 nm and a slightly positive ζ-potential with complete siRNA complexation. Behavior of PEGylated and non-PEGylated polyplexes were investigated in the presence of serum, in terms of siRNA complexation (fluorescence correlation spectroscopy), size (dynamic light scattering and single-particle tracking), interaction with proteins (isothermal titration calorimetry) and cellular uptake. Surprisingly, both PEGylated and non-PEGylated formulations presented relatively good behavior in the presence of fetal bovine serum (FBS). Hemocompatibility tests showed no effect of these polyplexes on hemolysis and coagulation. <i>In vivo</i> biodistribution in mice was performed and showed a better siRNA accumulation at the tumor site for PEGylated polyplexes. However, cellular uptake in protein-rich conditions showed that PEGylated polyplex lost their ability to interact with biological membranes and enter into cells, showing the importance to perform <i>in vitro</i> investigations in physiological conditions closed to <i>in vivo</i> situation. <i>In vitro</i>, the efficiency of PEGylated nanoparticles decreases compared to non-PEGylated particles, leading to the loss of the antiproliferative effect on cancer cells.