Anchoring of self-assembled plasmid DNA/anti-DNA antibody/cationic lipid micelles on bisphosphonate-modified stent for cardiovascular gene delivery

PURPOSE To investigate the anchoring of plasmid DNA/anti-DNA antibody/cationic lipid tri-complex (DAC micelles) onto bisphosphonate-modified 316 L coronary stents for cardiovascular site-specific gene delivery. METHODS Stents were first modified with polyallylamine bisphosphonate (PAA-BP), thereby enabling the retention of a PAA-BP molecular monolayer that permits the anchoring (via vector-binding molecules) of DAC micelles. DAC micelles were then chemically linked onto the PAA-BP-modified stents by using N-succinimidyl-3-(2-pyridyldithiol)-propionate (SPDP) as a crosslinker. Rhodamine-labeled DNA was used to assess the anchoring of DAC micelles, and radioactive-labeled antibody was used to evaluate binding capacity and stability. DAC micelles (encoding green fluorescent protein) were tethered onto the PAA-BP-modified stents, which were assessed in cell culture. The presence of a PAA-BP molecular monolayer on the steel surface was confirmed by X-ray photoelectron spectroscopy and atomic force microscope analysis. RESULTS The anchoring of DAC micelles was generally uniform and devoid of large-scale patches of defects. Isotopic quantification confirmed that the amount of antibody chemically linked on the stents was 17-fold higher than that of the physical adsorbed control stents and its retention time was also significantly longer. In cell culture, numerous green fluorescent protein-positive cells were found on the PAA-BP modified stents, which demonstrated high localization and efficiency of gene delivery. CONCLUSION The DAC micelle-immobilized PAA-BP-modified stents were successful as a gene delivery system. Gene delivery using DAC micelle-tethered stent-based PAA-BP functionalization should be suitable for a wide array of single or multiple therapeutic gene strategies, and could be used on cardiovascular metallic implants for achieving efficient gene therapy.