Abstract
Since recombinant viral vectors have been associated with serious side effects, such as immunogenicity and oncogenicity, synthetic delivery systems represent a realistic alternative for achieving efficacy in gene therapy. A major challenge for non-viral nanocarriers is the optimization of transgene expression in the targeted cells. This goal can be achieved by fine-tuning the chemical carriers and the adding specific motifs to promote cellular penetration. Our study focuses on the development of novel folate-based complexes that contain varying quantities of folate motifs. After controlling for their physical properties, neutral folate-modified lipid formulations were compared in vitro to lipoplexes leading to comparable expression levels. In addition, no cytotoxicity was detected, unlike what was observed in the cationic controls. Mechanistically, the delivery of the transgene appeared to be, in part, due to endocytosis mediated by folate receptor targeting. This mechanism was further validated by the observation that adding free folate into the medium decreased luciferase expression by 50%. In vivo transfection with the folate-modified MM18 lipid, containing the highest amount of FA-PEG570-diether co-lipid (w:w; 90:10), at a neutral charge ratio, gave luciferase transgene expression. These studies indicate that modification of lipids with folate residues could enhance non-toxic, cell-specific gene delivery.
Highlights
Many diseases caused by genetic anomalies are currently not treatable by conventional therapies
It has previously been shown that co-incubation of folate-targeted liposomes with large amounts (~50 nM) of folic acid was required to significantly reduce folate receptor (FR)-specific cellular liposome uptake, suggesting that folate liposomes may have an unusually high affinity for FR-positive cells [50]. We demonstrated that this effect was observed for lower amounts of folic acid depending on the formulation and the FR-α wealth
This work was meant to be an extension of encouraging results described in the literature that showed that grafting of folic acid residues to DNA/lipid complexes led to selective expression of foreign genes in folate-expressing cells in vitro [49,55]
Summary
Many diseases caused by genetic anomalies (e.g., mutation, aberrant expression) are currently not treatable by conventional therapies. Recent scientific advances in genomics have enhanced our understanding of the role that genes play in disease and have led to gene therapy, one of the most promising biomedical and pharmacological interventions, which has already seen clinical success [1]. In addition to inherited disorders like CF [4], gene therapy could potentially be used as a standard clinical intervention for the treatment of cancer, infectious diseases [5], cardiovascular disorders [6], and neurological pathologies [7], to name but a few. More than 1400 gene therapy clinical trials have been completed, are ongoing, or have been approved worldwide [9]
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