Synthesis of efficient gene delivery systems by grafting pegylated alkylcarboxylate chains to PAMAM dendrimers: Evaluation of transfection efficiency and cytotoxicity in cancerous and mesenchymal stem cells

The applications of polyamidoamine (PAMAM) dendrimers have attracted much attention in biomedicine specially non-viral gene delivery because of thier unique characteristics including hyperbranching, multivalency, and well-defined uniform globular three-dimensional structures. In the current study, in order to enhance the transfection efficiency and reduce the cytotoxicity of PAMAMs, bromoalkylcarboxylates with different chain length (2-bromoacetic, 6-bromohexanoic, 10-bromodecanoic and 16-bromohexadecanoic acids) were covalently conjugated with 10% and 30% of primary amines of generation 4 and 5 (G4 and G5) of PAMAM dendrimers to increase the hydrophobicity of the carrier. At the next stage, the alkylcarboxylate-PAMAMs were pegylaed to further modify the PAMAM structures for biological applications. Obtained results demonstrated that the prepared PAMAM derivatives had particle size around 140 nm with net-positive surface charge. None of the prepared PAMAM-based non-viral vactors exhibited significant hemolytic activity and also cytotoxicity. Meanwhile decahexanoate-PAMAM G4 [ G4(16C-10%)] and decanoate-PAMAM G4 conjugated to polyethylene glycol (PEG) (G4[(10C-30%)(10C-PEG)]) showed highest transfection efficiency in murine neuroblastoma (Neuro-2a) cell line, interestingly only the latter had improved transfection efficiency in mesenchymal stem cells (MSCs). This study proved the potential utility of alkylcarboxylate-grafted PAMAM dendrimers (G4 and G5) with or without PEG modification for efficient gene transfer into cancerous cells as well as MSCs.