Specific gene delivery mediated by poly(ethylene glycol)-grafted polyamidoamine dendrimer modified with a novel HER2-targeting nanobody

As compared to other nanobiopolymers used in gene delivery applications, polyamidoamine dendrimers possess significantly improved physical and chemical properties such as monodispersity, well-defined size and shape, and biocompatibility, which make them ideal vectors for biomedical purposes. The aim of this study was fine-tuning of an anti–human epidermal growth factor receptor 2 (HER2) nanobody–polyethylene glycol (PEG)–G5 polyamidoamine gene delivery vector for potential in vivo applications. Polyethylene glycol was conjugated to polyamidoamine dendrimers at three different molar ratios of 10, 20, and 30 (polyethylene glycol:polyamidoamine). Anti-HER2 nanobody was chosen as our targeting agents and attached to polyethylene glycol–polyamidoamine conjugates. Cytotoxicity assays and transfection studies were carried out to find the most efficient conjugate in terms of both low cytotoxicity and high transfection rate. Our data indicated that PEGylation decreased the cytotoxicity of dendrimers alone and when complexed with DNA (dendriplexes). Among all of the polyethylene glycol–polyamidoamine dendrimers, polyethylene glycol(10)–polyamidoamine resulted in the most efficient gene transfection vector in both BT-474 and MCF-10A cell lines. Incorporation of anti-HER2 nanobodies could further increase their cellular uptake up to 1.7-fold compared to native dendrimers in HER2-overexpressing BT-474 cells but not in HER2-negative MCF-10A cells. It can be concluded from our results that nanobody–polyethylene glycol–polyamidoamine conjugates might be a promising new bioconjugate for the targeted gene delivery to HER2-positive tumor cells in vivo.