Functionalized Dendrimers And Their Nanocomposites Used As Nonviral Vectors For Gene Delivery Applications

Gene therapy is a novel technique that introduce a piece of genetic materials into target cells for curing different of inherited and acquired diseases. Nowadays, various studies have been done to get vectors with high efficiency, low cytotoxicity and targeting delivery abilities via conjugating small molecules or grafting specific ligands to these vectors.In this study, we report two types of new gene delivery vectors based on generation5poly(amidoamine) dendrimers (PAMAM)(G5.NH2):alkylated PAMAM dendrimer (G5.NH2-Cn, n denoted the number of the carbon atoms of the alkylated chain) and folic acid (FA)-modified dendrimer-entrapped gold nanoparticles (Au DENPs-FA).First, two types of novel dendrimer-based gene delivery vectors were fabricated. G5.NH2-Cn (n=6or12) was synthesized using G5.NH2to conjugate cyclohexane oxide or cyclododecane epoxide, while Au DENPs-FA was formed by using FA-premodified G5.NH2as templates to entrap AuNPs via reducing Au salt at Au salt/dendrimer molar ratio of25:1. Then, the vector/pDNA polyplexes were prepared under several N/P ratios (where N=number of primary amines of the dendrimer; P=number of phosphate groups of the pDNA backbone). The vectors are characterized in respect to their cytotoxicity using MTT assay and the ability to bind and compact pDNA via gel retardation assay. The polyplexes formed between vectors and pDNA were analyzed concerning their size, zeta potential. Last, the synthesized polymers were used as non-viral vectors for delivery of plasmid DNA (pDNA) into cancer cells. The N/P ratio was optimized using model cancer cell line (Hela cells) based on the capacity of being internalized by cells and transfection efficiency.G5.NH2-Cn/pDNA polyplex shows an appropriate size and zeta potential for cellular uptake with a acceptable cytotoxicity. The transfection efficiency of G5.NH2-Cn has been improved to some extent under a specific N/P ratio. Likewise, the Au DENPs-FA vector was able to completely compact the pDNA at an N/P ratio of0.5. MTT assay of Hela cells demonstrated that the Au DENPs-FA/pDNA polyplex was less cytotoxic than the Au DENPs/pDNA. Transfection results showed that the Au DENPs-FA vector exhibited much higher EGFP and luciferase gene expression in Hela cells overexpressing folate acid receptors (FAR) than the Au DENPs without FA especially at the N/P of2.5. Findings from our study indicate that the FA-modified Au DENPs may serve as low cytotoxic non-viral vectors for highly efficient targeting gene transfection applications.