β-Galactosylated alkyl-oligoamine derivatives of polyethylenimine enhanced pDNA delivery into hepatic cells with reduced toxicity

β-Galactosyl residues were covalently attached to modified 10 kDa polyethylenimine (PEI) derivatives and the conjugates were evaluated for cell type-specific effects on transfection efficiency and cytotoxicity. The PEI derivatives consisted of 10 kDa branched PEI, which has lower molecular weight and less cytotoxicity than the more widely used 25 kDa PEI, which was initially carboxyalkylated with three different alkyl chain lengths (C-6, C-10, C-16) and then the primary amine content that was lost in the alkylation process was replaced by attaching the oligoamines, spermidine or diethylentriamine by an amide linkage. β-Galactosyl residues were attached to PEI derivatives by a reductive amination with lactose. β-Galactosylated alkyl-oligoamine derivatives of PEI were able to condense plasmid DNA optimally at a carrier to plasmid DNA (C/P) weight ratio ≥ 2:1. All β-galactosylated constructs examined yielded complexes significantly larger than those formed with alkyl-oligoamine derivatives of PEI. The measured particle size was in the range of 101-147 nm. β-Galactosylated PEI derivatives containing a C-10 linker and complexed with a luciferase reporter gene (pCMV-luc) gave transfection efficiencies in HepG2 human liver carcinoma cells, which express asialoglycoprotein receptors, up to 2.1 fold higher than for 25 kDa PEI polyplexes prepared in the same manner, whereas in Neuro2A cells there was no significant β-galactosylation-associated differences in transfection efficiencies. β-Galactosylated PEI derivatives exhibited significantly reduced cytotoxicity with both HepG2 and Neuro2A cells at all C/P ratios tested. These results support the use of β-galactosylated derivatives of PEI in any attempt to develop a hepatocytetargeting gene carrier.