Delivery of a Cancer-Testis Antigen-Derived Peptide Using Conformationally Restricted Dipeptide-Based Self-Assembled Nanotubes.

Use of tumor-associated antigens for cancer immunotherapy is limited due to their poor in vivo stability and low cellular uptake. Delivery of antigenic peptides using synthetic polymer-based nanostructures has been actively pursued but with limited success. Peptide-based nanostructures hold much promise as delivery vehicles due to their easy design and synthesis and inherent biocompatibility. Here, we report self-assembly of a dipeptide containing a non-natural amino acid, α,ß-dehydrophenylalanine (ΔF), into nanotubes, which efficiently entrapped a MAGE-3-derived peptide (M3). M3 entrapped in F-ΔF nanotubes was more stable to a nonspecific protease treatment and both F-ΔF and F-ΔF-M3 showed no cellular toxicity for four cancerous and noncancerous cell lines used. F-ΔF-M3 showed significantly higher cellular uptake in RAW 267.4 macrophage cells compared to M3 alone and also induced in vitro maturation of dendritic cells (DCs). Immunization of mice with F-ΔF-M3 selected a higher number of IFN-γ secreting CD8+ T cells and CD4+ T compared to M3 alone. On day 21, a tumor growth inhibition ratio (TGI, %) of 41% was observed in a murine melanoma model. These results indicate that F-ΔF nanotubes are highly biocompatible, efficiently delivered M3 to generate cytotoxic T lymphocytes responses, and able to protect M3 from degradation under in vivo conditions. The F-ΔF dipeptide-based nanotubes may be considered as a good platform for further development as delivery agents.

Efficacy of Dipeptide-Coated Magnetic Nanoparticles in Lung Cancer Models Under Pulsed Electromagnetic Field.

Lung cancer is the leading cause of cancer deaths and the overall 5-year survival rate is less than 17%. Hyperthermia is an alternative approach for the treatment of lung cancer and is associated with fewer side effects. We employed ironoxide nanoparticles in inducing localized hyperthermia in lung cancer cells using a pulsed electromagnetic field (PEMF). We synthesized, characterized and determined the uptake of dipeptide-coated iron oxide nanoparticles. Further, their ability in inducing localized hyperthermia in PEMF on lung cancer cells was assessed. Results showed nanoparticles are non-cytotoxic and showed enhanced cellular uptake in lung cancer cells. In vivo studies in nude mice lung tumor xenografts confirmed the presence in the tumors. Lung cancer cells pretreated with dipeptide-coated magnetic nanoparticles upon PEMF exposure induced cell death.

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,ß-dehydrophenylalanine (ΔF) and found that an arginine containing dipeptide, arginine-α,ß-dehydrophenylalanine (R-ΔF) condensed pEGFP-N1 plasmid into positively charged spherical nanoparticles of size 250­275 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.