Characterization of DNA Condensation by Conformationally Restricted Dipeptides and Gene Delivery

A wide variety of non-viral vectors have been developed for gene delivery in past few decades but find limited applications mainly due to lower encapsulation, endosomal entrapment, high toxicity and low transfection efficiency. In this work, we explored plasmid DNA binding ability of several low molecular weight dipeptides containing α,β-dehydrophenylalanine (ΔF) and found that an arginine containing dipeptide, arginine-α,β-dehydrophenylalanine (R-ΔF) condensed pEGFP-N1 plasmid into positively charged spherical nanoparticles of size 250–275 nm. Single molecule techniques showed that R-ΔF interacted with the plasmid DNA in a dose dependent manner which was accompanied by a decrease in diffusion time of the plasmid DNA as well as release of the bound fluorophore. The plasmid DNA in R-ΔF-plasmid complex (R-ΔF-Pl) was stable against DNase action. A pH dependent release of the plasmid DNA from R-ΔF-Pl was observed and the released plasmid DNA retained its natural conformation at endosomal pH, as evidenced from time correlated single photon counting. R-ΔF-Pl was biocompatible and showed ready uptake in HEK 293T cells. Transfection assays using reporter plasmids for green fluorescent protein (GFP), luciferase enzyme and chloramphenicol acetyltransferase (CAT) showed R-ΔF mediated gene delivery both in the presence and absence of serum in the medium. Ease of synthesis, homogenous assembly and biocompatibility balanced with significant expression of gene of interest make R-ΔF a potential vector for development for in vivo application.