Poly(amidoamine) Dendrimers Modified with 1,2-Epoxyhexane or 1,2-Epoxydodecane for Enhanced Gene Delivery Applications.

We report a new non-viral gene delivery system based on hydrophobically modified poly(amidoamine) (PAMAM) dendrimers. In this study, the periphery of amine-terminated generation 5 (G5) PAMAM dendrimers was partially reacted with 1,2-epoxyhexane and 1,2-epoxydodecane, respectively. The formed hydrophobically modified G5 dendrimers (denoted as G5.NH2-C6 or G5.NH2-C12) were used to complex two different plasmid DNAs (pDNAs) encoding luciferase (Luc) and enhanced green fluorescent protein (EGFP), respectively for gene transfection studies. The polyplexes formed between vectors and pDNA were characterized by gel retardation assay, dynamic light scattering, and zeta potential measurements. We show that the G5.NH2-C6 and G5.NH2-C12 vectors are able to effectively compact the pDNA, allowing for highly efficient gene transfection into a model cell line (HeLa cells) as demonstrated by both Luc assay and confocal microscopic imaging of the EGFP expression. Under the studied N/P ratios (the molar ratio of primary amines of the dendrimers to phosphates in the pDNA backbone) at 2.5 or 5, the transfection efficiency of the dendrimer-based vectors followed the order of G5.NH2-C12 > G5.NH2-C6 > G5.NH2. This enhanced gene transfection capacity is believed to be associated with the enhanced hydrophobic interaction between the vector/pDNA complexes and the relatively hydrophobic cell membranes. The developed hydrophobically modified dendrimers may be used as a promising non-viral vector for enhanced gene delivery applications.

Dendrimer-entrapped gold nanoparticles modified with folic acid for targeted gene delivery applications.

We report a new use of dendrimer-entrapped gold nanoparticles (Au DENPs) modified with folic acid (FA) as a non-viral vector for targeted gene delivery applications. In this study, amine-terminated generation 5 poly(amidoamine) dendrimers modified with FA via covalent conjugation were used as templates to synthesize gold nanoparticles with an Au salt/dendrimer molar ratio of 25 : 1. The synthesized FA-modified Au DENPs (Au DENPs-FA) were used as a non-viral vector for the delivery of plasmid DNA (pDNA) into a model cancer cell line (HeLa cells) overexpressing high-affinity FA receptors (FAR). The DNA compaction ability of the formed Au DENPs-FA was systematically characterized using a gel retardation assay, zeta potential, and dynamic light scattering. We show that similar to the Au DENPs vector without FA, the Au DENPs-FA vector was able to compact the pDNA encoding enhanced green fluorescent protein (EGFP) at an N/P ratio of 0.5. Transfection results show that the Au DENPs-FA vector enables much higher luciferase and EGFP gene expression in HeLa cells overexpressing FAR than the Au DENPs without FA, demonstrating the role played by FA-mediated targeting for enhanced gene transfection in target cells. With a lower cytotoxicity than that of the Au DENPs without FA proven by a cell viability assay, the developed FA-modified Au DENPs may be used as a promising non-viral vector for safe and targeted gene therapy applications.

A highly effective polymerase chain reaction enhancer based on dendrimer-entrapped gold nanoparticles.

In molecular biology, polymerase chain reaction (PCR) has played an important role but suffers a general problem of low efficiency and specificity. Development of suitable PCR additives to improve the specificity and efficiency still remains a great challenge. Here we report the use of dendrimer-entrapped gold nanoparticles (Au DENPs) as a novel class of enhancers to improve the specificity and efficiency of PCR. We show that the Au DENPs prepared using amine-terminated generation 5 poly(amidoamine) dendrimers (G5.NH(2)) as templates are much more effective than the same dendrimers without AuNPs entrapped in improving the specificity and efficiency of an error-prone two-round PCR system. With the increase of the molar ratio between Au atom and G5.NH(2) dendrimer in the Au DENPs, the optimum concentration of Au DENPs used to improve the PCR specificity and efficiency is decreased and can be as low as 0.37 nM when the Au atom/G5.NH(2) dendrimer molar ratio reaches 100:1. Our PCR results along with the dynamic light scattering data suggest that unlike the flexible soft dendrimers without NPs entrapped that may display a non-spherical shape when interacting with the PCR components, the Au DENPs with increasing Au atom/dendrimer molar ratio are able to reserve the spherical shape of dendrimers, enabling much more efficient interaction with the PCR components. Therefore, as a NP-based PCR enhancer, both the surface charge and the shape of the particles should be responsible for effective interaction with the PCR components for improving the PCR specificity and efficiency. Furthermore, the used Au DENPs were proved to be stable after the PCR process, enabling them to be potentially used for enhancing different PCR systems.