Targeting folate receptors (α1) to internalize the bleomycin loaded DNA-nanotubes into prostate cancer xenograft CWR22R cells

Abstract

DNA-nanotechnology based on DNA scaffolding technique is an established approach to formulate water-miscible nano-structural frameworks. We have designed the hydrophilic DNA-nanotubes (D-NTs) as a (water-soluble) vehicle to encapsulate a water-insoluble DNA-intercalating anticancer drug. Bleomycin (BM) is a model hydrophobic anticancer drug used in this study capable to bind with the D-NTs to formulate BM loaded D-NTs. This BM@D-NTs system was evaluated for the improvement of the in vitro anti-cancer effects on the resistant prostate cancer xenograft CWR22R cells, over-expressed with the folate receptors/alpha (FRα). D-NTs were functionalized with the FRα-targeting antibodies to interact with the FRα (receptors) highly expressed on the resistant prostate cancer xenograft CWR22R cells. D-NTs not only increased the aqueous miscibility/dispersibility of BM but also enhanced the therapeutic efficiency as a targeted (site-specific) drug delivery system. D-NTs synthesis was achieved by sticky ends cohesions of DNA triangular tiles. DNA triangles were self-assembled from a freshly circularized short scaffold chain (84-NT) by annealing with the various staple strands. The polymerization of the triangular tiles gave rise to DNA-nanosheet lattices which underwent morphological transition guided by the twists in the DNA duplexes. This DNA double helix curvature caused self-coiling of the DNA 2D nano-sheets to condense into D-NTs morphology. Native-Page gel experiment showed decreased electrophoretic mobility down the gel confirming the successful execution of the polymerized lattices via sticky ends cohesion of the DNA-triangles. The final morphology and self-coiling of 2D DNA nano-sheets were confirmed through atomic force microscopy (AFM) showed the successful synthesis of D-NTs having diameter 3 to 5 μm and length 200 to 600 nm. BM was loaded onto D-NTs via incubation of hydro-alcoholic solution of the BM with the aqueous solution of D-NTs followed by the evaporation of alcohol and intercalation of the BM onto D-NTs. The intercalation of BM onto D-NTs was confirmed by UV-shift analysis. The targeted cytotoxicity of the BM@D-NTs for the CWR22R (resistant prostate cancer xenograft) cells was confirmed through MTT assay and the flow cytometry compared to the highly compatible empty D-NTs. Confocal microscopy revealed the time-dependent transfection of BM@D-NTs into CWR22R cells compared to the control cell line.