Anionic polymer-coated lipoplex for safe gene delivery into tumor by systemic injection

In this study, we developed an anionic lipoplex by coating cationic lipoplex with anionic polymers such as hyaluronan (HA), chondroitin sulfate C (CS) and poly-l-glutamic acid (PLE) to deliver the plasmid DNA efficiently into the tumor by avoiding interaction with erythrocytes. The sizes of HA-, CS- and PLE-coated lipoplexes were ∼200 nm and the ζ-potentials were negative. CS- and PLE-coated lipoplexes did not induce agglutination after mixing with erythrocytes, but cationic and HA-coated lipoplexes exhibited agglutination. In terms of biodistribution and gene expression after intravenous administration, cationic and HA-coated lipoplexes largely accumulated and induced gene expression in the lung. In contrast, CS- and PLE-coated lipoplexes did not exhibit high gene expression in the lung and mainly accumulated in the liver. However, in tumor, differences in lipoplex accumulation and gene expression were not observed among the lipoplexes. In terms of toxicity after intravenous injection, CS- and PLE-coated lipoplexes did not increase tumor necrosis factor-α, aspartate aminotransferase and alanine aminotransferase concentrations in blood. From these findings, CS and PLE coatings for cationic lipoplex might produce safe systemic vectors, although they did not increase gene expression in tumor.