Design flexibility influencing the in vitro behavior of cationic SLN as a nonviral gene vector

In this paper SLN were prepared using stearic acid as main lipid component, stearylamine as cationic agent and protamine as transfection promoter and adding phosphatidylcholine (PC), cholesterol (Chol) or both to obtain three different multicomponent SLN (SLN-PC, SLN-Chol and SLN-PC-Chol, respectively). Cytotoxicity and transfection efficiency of the obtained SLN:pDNA complexes were evaluated on three different immortalized cell lines: COS-I (African green monkey kidney cell line), HepG2 (human hepatocellular liver carcinoma cell line) and Na1300 (murine neuroblastoma cell line). Samples were characterized for the exact quantitative composition, particle size, morphology, zeta potential and pDNA binding ability. All the three SLN samples were about 250-300nm in size with a positive zeta potential, whereas SLN:pDNA complexes were about 300-400nm in size with a less positive zeta potential, depending on the SLN composition. Concerning the cell tolerance, the three samples showed a level of cytotoxicity lower than that of the positive control polyethylenimine (PEI), regardless of the cell lines. The best transfection performance was observed for SLN-PC-Chol on COS-I cells while a transfection level lower than PEI was observed on HepG2 cells, regardless the SLN composition. On Na1300 cells, SLN-Chol showed a double efficiency with respect to PEI. Comparing these results to those obtained with the same kind of SLN without PC and/or Chol, it is possible to conclude that the addition of Chol and/or PC to the composition of cationic SLN modify the cell tolerance and the transfection efficiency of the gene vector in a manner strictly dependent on the cell type and the internalization pathways.