PEG-conjugated PAMAM Dendrimers Mediate Efficient Intramuscular Gene Expression

Abstract

Abstract. Generations 5 and 6 (G5 and G6) poly(amidoamine) (PAMAM) dendrimers have been shown to be highly efficient nonviral carriers in in vitro gene delivery. However, their high toxicity and unsatisfied in vivo efficacy limit their applications. In this study, to improve their characteristics as gene delivery carriers, polyethylene glycol (PEG, molecular weight 5,000) was conjugated to G5 and G6 PAMAM dendrimers (PEG-PAMAM) at three different molar ratios of 4%, 8%, and 15% (PEG to surface amine per PAMAM dendrimer molecular). Compared with unconjugated PAMAM dendrimers, PEG conjugation significantly decreased the in vitro and in vivo cytotoxicities and hemolysis of G5 and G6 dendrimers, especially at higher PEG molar ratios. Among all of the PEG-PAMAM dendrimers, 8% PEG-conjugated G5 and G6 dendrimers (G5-8% PEG, G6-8% PEG) resulted in the most efficient muscular gene expression when polyplexes were injected intramuscularly to the quadriceps of neonatal mice. Consistent with the in vivo results, these two 8% PEG-conjugated PAMAM dendrimers could also mediate the highest in vitro transfection in 293A cells. Therefore, G5-8% PEG and G6-8% PEG possess a great potential for gene delivery both in vivo and in vitro.

PEGylation of Polypropylenimine Dendrimer with Alkylcarboxylate Chain Linkage to Improve DNA Delivery and Cytotoxicity

“…On the other hand, many studies showed that PEGylation of dendrimers increases their solubility, enhances structural stability, improves biocompatibility, prolongs blood circulation halflife, decreases the immunogenicity, reduces intermolecular aggregation, and finally helps to avoid their rapid clearance by reticulo-endothelial system (RES) [11,12,[16][17][18]. Polyethylene glycol (PEG) has been widely used in the polymeric gene carriers; however, it was shown that PEGylation could improve or decrease transfection activity of polymers [19,20].…”

Targeted delivery of polyamidoamine-paclitaxel conjugate functionalized with anti-human epidermal growth factor receptor 2 trastuzumab

“…The modification of PAMAM with NHS-PEG-MAL can produce an intermediate that is coated with PEG spacers. This intermediate can be used to promote PAMAM hydrophilicity, avoid non-specific interactions, decrease cytotoxicity, 20 and provide thiol-reactive maleimides for coupling thiolated TMAB. NHS-PEG-MAL conjugation to G4 PAMAM was confirmed by the appearance of a signal at 3.6 ppm that corresponded to the methylene protons of PEG (Figure 2).…”

Dendrimers and miktoarm polymers based multivalent nanocarriers for efficient and targeted drug delivery

“…70 For example, cytotoxicity associated with amine terminated dendrimers has been overcome by PEGylation and acetylation. [71][72][73][74][75] PEGylation makes the dendrimers biocompatible, as well as helps meet other objectives including improved biodistribution and pharmacokinetics, solubility, increase in drug loading, sustained and controlled drug release etc. [76][77][78] Sometimes, surface modifications can lead to problems.…”

“…For example, Roth and coworkers were able to decrease toxicity of PAMAM dendrimers to U87 cells, but higher degrees of amine neutralization reduced the gene silencing efficiency of PAMAM/siRNA delivery vectors. 73,75 Thus, there are still opportunities for chemists to develop synthetic methodologies that could achieve surface modifications without compromising their overall properties, and achieve functionalization with chemically reactive groups suitable for attachment of desired moieties at a low cost and minimum purification steps.…”