VEGF receptor binding peptide-linked amphiphilic peptide with arginines and valines for endothelial cell-specific gene delivery

Rationally designed cationic amphiphilic peptides for selective gene delivery to cancer cells

Gene therapy has gained increasing attention as an alternative to pharmacotherapy for treatment of various diseases. The extracellular and intracellular barriers to gene delivery necessitate the use of gene vectors which has led to the development of myriads of gene delivery systems. However, many of these gene delivery systems have pitfalls such as low biocompatibility, low loading efficiency, low transfection efficiency, lack of tissue selectivity and high production costs. Herein, we report the development of a new series of short cationic amphiphilic peptides with anticancer activity for selective delivery of small interfering RNA (siRNA) and antisense oligodeoxynucleotides (ODNs) to cancer cells. The peptides consist of alternating dyads of hydrophobic (isoleucine (I) or leucine (L)) and hydrophilic (arginine (R) or lysine (L)) amino acids. The peptides exhibited higher preference for transfection of HCT 116 colorectal cancer cells compared to human dermal fibroblasts (HDFs) and induced higher level of gene silencing in the cancer cells. The nucleic acid complexation and transfection efficiency of the peptides was a function of their secondary structure, their hydrophobicity and their C-terminal amino acid. The peptides containing L in their hydrophobic domain formed stronger complexes with siRNA and successfully delivered it to the cancer cells but were unable to release their cargo inside the cells and therefore could not induce any gene silencing. On the contrary, the peptides containing I in their hydrophobic domain were able to release their associated siRNA and induce considerable gene silencing in cancer cells. The peptides exhibited higher selectivity for colorectal cancer cells and induced less gene silencing in fibroblasts compared to the lipid-based commercial transfection reagent DharmaFECT™ 1. The results from this study can serve as a tool for rational design of new peptide-based gene vectors for high selective gene delivery to cancer cells.

Current state of the art in peptide-based gene delivery

Gene therapy involves introduction of exogenous genetic materials into the cells in order to correct a specific pathological condition. However, efficient delivery of the genetic materials to the target cells is hampered by a number of extracellular and intracellular barriers which necessitates the use of gene vectors. Despite the high transfection efficiencies of the viral vectors, their immunogenicity and complex manufacturing procedures has led to the quest for development of non-viral vectors with lower toxicity and easier fabrication from a variety of materials such as polymers and lipids. More recently, peptides have been introduced as new promising biomaterials for gene delivery owing to their desirable physicochemical properties and their biocompatibility. Various naturally derived, synthetic or hybrid peptides with varying sizes and structural features have been used for gene delivery. In this review, a summary of recent advances in the development of peptide-based gene delivery systems for delivery of different types of genetic materials to different types of cells/tissues has been provided. The focus of this review is on gene delivery systems consisting merely of peptides without incorporation of polymers or lipids. The transfection efficiencies of different groups of peptides and their abilities for targeted gene delivery have been viewed in the context of their chemical structures in order to provide an insight into the structural features required for efficient gene delivery by different classes of peptides and to serve as a guide for rational design of new types of peptide vectors for highly efficient and tissue-specific gene delivery.