Targeted Delivery of Nucleic Acid Therapeutics via Nonviral Vectors

Advances in Targeted Gene Delivery

Gene therapy has the potential to treat both acquired and inherited genetic diseases. Generally, two types of gene delivery vectors are used - viral vectors and non-viral vectors. Non-viral gene delivery systems have attracted significant interest (e.g. 115 gene therapies approved for clinical trials in 2018; clinicaltrials.gov) due to their lower toxicity, lack of immunogenicity and ease of production compared to viral vectors. To achieve the goal of maximal therapeutic efficacy with minimal adverse effects, the cell-specific targeting of non-viral gene delivery systems has attracted research interest. Targeting through cell surface receptors; the enhanced permeability and retention effect, or pH differences are potential means to target genes to specific organs, tissues, or cells. As for targeting moieties, receptorspecific ligand peptides, antibodies, aptamers and affibodies have been incorporated into synthetic nonviral gene delivery vectors to fulfill the requirement of active targeting. This review provides an overview of different potential targets and targeting moieties to target specific gene delivery systems.

Effective and safe in vivo gene delivery based on polyglutamic acid complexes with heterocyclic amine modified-polyethylenimine

Polyethylenimine (PEI) has been extensively used for non-viral gene delivery. Increasing the molecular weight of PEI often improves transfection efficiency, but enhances cytotoxicity and non-specific interaction with plasma proteins, limiting its use in clinical applications. In this study, poly-l-glutamic acid (L-PGA) as an anionic polymer, was introduced to piperazine-modified PEI to improve its in vivo properties. The physicochemical properties, cytotoxicity, in vitro and in vivo tranfection efficiency of these carriers were evaluated. Conjugation of 50% of primary amines of PEI 25 kDa with piperazine in the presence of PGA_1% (PEI₂₅Pip_50%/PGA_1%) could significantly increase transfection efficiency even in the presence of serum compared to PEI 25 kDa. Increasing the PGA content led to lower cytotoxicity of DNA/PEI₂₅Pip_50%/PGA_1% triplexes. Systemic administration of triplexes in Balb/c mice resulted in significant enhancement of luciferase gene expression in brain, spleen, and liver compared to PEI 25 kDa. In a 30-day survival study, no significant changes were observed in mice body weights in DNA/PEI₂₅Pip_50%/PGA_1% group. Moreover, this group exhibited a survival rate of 100% compared to 0% in mice receiving PEI 25 kDa. This novel PEI₂₅Pip_50%/PGA_1% carrier could be used to overcome the serum inhibitory effects on gene expression in vivo, providing a promising gene delivery system for tissue-specific targeting.