Dendrimer-grafted bioreducible polycation/DNA multilayered films with low cytotoxicity and high transfection ability

Controlled release of incorporated foreign DNA from multilayered films plays an important role in surface-mediated gene delivery. Herein, multilayered polyelectrolyte complex thin films, composed of dendrimer-grafted bio-reducible cationic poly(disulfide amine) and plasmid DNA, were fabricated via layer-by-layer (LBL) assembly for in vitro localized gene delivery. The UV absorbance and thickness of the LBL films were found to have linear correlation with the numbers of poly(disulfide amine)/DNA bilayers. Although LBL films were stable in PBS buffer, their degradation could be triggered by reducing agents (i.e. glutathione, GSH). The degradation rate of the films is directly proportional to the GSH concentration, which in turn affected the corresponding gene expression. All poly(disulfide amine)/DNA films exhibited lower cytotoxicity and higher transfection activity in comparison with PEI/DNA multilayered films. Moreover, LBL films showed the highest transfection efficiency in the presence of 2.5 mM GSH when cultured with 293T cells, with ~36% GFP-positive 293T cells after 5-days of co-culture. These DNA-containing reducible films could potentially be useful in gene therapy and tissue engineering by controlling the release of incorporated DNA.

Fluorimetric Detection of G-Quadruplex DNA in Solution and Adsorbed on Surfaces with a Selective Trinuclear Cyanine Dye

Quadruplex DNA, which is a relevant target for anticancer therapies, may alter its conformation because of interactions with interfaces. In pursuit of a versatile methodology to probe adsorption-induced conformational changes, the interaction between a fluorescent [2.2.2]heptamethinecyanine dye and quadruplex DNA (G4-DNA) was studied in solution and on surfaces. In solution, the cyanine dye exhibits a strong light-up effect upon the association with G4-DNA without interference from double-stranded DNA. In addition, a terminal π-stacking as a binding mode between the cyanine dye and G4-DNA is concluded using NMR spectroscopy. To unravel the effects of adsorption on the conformation of quadruplex-DNA, G4-DNA, and double-stranded and single-stranded DNA were adsorbed to positively charged poly(allylamine) hydrochloride (PAH) surfaces, both in planar and in constrained 55 nm diameter aluminum oxide nanopore formats. All DNA forms showed a very strong affinity to the PAH surfaces as shown by surface plasmon resonance and reflectometric interference spectroscopy. The significant increase of the fluorescence emission intensity of the cyanine light-up probe observed exclusively for surface immobilized G4-DNA affords evidence for the adsorption of G4-DNA on PAH with retained quadruplex conformation.