Article

Bisphosphonate-mediated gene vector delivery from the metal surfaces of stents. Proc Natl Acad Sci USA

Division of Cardiology, The Children's Hospital of Philadelphia, Department of Chemical, Philadelphia, PA 19104, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 02/2006; 103(1):159-64. DOI: 10.1073/pnas.0502945102
Source: PubMed

ABSTRACT The clinical use of metallic expandable intravascular stents has resulted in improved therapeutic outcomes for coronary artery disease. However, arterial reobstruction after stenting, in-stent restenosis, remains an important problem. Gene therapy to treat in-stent restenosis by using gene vector delivery from the metallic stent surfaces has never been demonstrated. The present studies investigated the hypothesis that metal-bisphosphonate binding can enable site-specific gene vector delivery from metal surfaces. Polyallylamine bisphosphonate (PAA-BP) was synthesized by using Michael addition methodology. Exposure to aqueous solutions of PAA-BP resulted in the formation of a monomolecular bisphosphonate layer on metal alloy surfaces (steel, nitinol, and cobalt-chromium), as demonstrated by x-ray photoelectron spectroscopy. Surface-bound PAA-BP enabled adenoviral (Ad) tethering due to covalent thiol-binding of either anti-Ad antibody or a recombinant Ad-receptor protein, D1. In arterial smooth muscle cell cultures, alloy samples configured with surface-tethered Ad were demonstrated to achieve site-specific transduction with a reporter gene, (GFP). Rat carotid stent angioplasties using metal stents exposed to aqueous PAA-BP and derivatized with anti-knob antibody or D1 resulted in extensive localized Ad-GFP expression in the arterial wall. In a separate study with a model therapeutic vector, Ad-inducible nitric oxide synthase (iNOS) attached to the bisphosphonate-treated metal stent surface via D1, significant inhibition of restenosis was demonstrated (neointimal/media ratio 1.68 +/- 0.27 and 3.4 +/- 0.35; Ad-iNOS vs. control, P < 0.01). It is concluded that effective gene vector delivery from metallic stent surfaces can be achieved by using this approach.

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    • "This " coatless " method of vector immobilization distinguishes our approach from other studies employing multi-micron polymer coatings of the stent struts to incorporate gene vectors in the bulk of the polymer. Both, our affinity binding [26] and HC tethering [27] Ad immobilization strategies have demonstrated effective local transduction of vascular tissue and inhibition of restenosis in stented arterial segments using stents configured with Ad vectors encoding inducible nitric oxide synthase (Ad-iNOS). Since the immobilization scheme realized using cleavable (hydrolyzable) cross-linkers[27] allowed for better control of vector loading and release, it was chosen for further development of stent-based gene delivery. "
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    ABSTRACT: The use of arterial stents and other medical implants as a delivery platform for surface immobilized gene vectors allows for safe and efficient localized expression of therapeutic transgenes. In this study we investigate the use of hydrolyzable cross-linkers with distinct kinetics of hydrolysis for delivery of gene vectors from polyallylamine bisphosphonate-modified metal surfaces. Three cross-linkers with the estimated t1/2 of ester bonds hydrolysis of 5, 12 and 50 days demonstrated a cumulative 20%, 39% and 45% vector release, respectively, after 30 days exposure to physiological buffer at 37 °C. Transgene expression in endothelial and smooth muscles cells transduced with substrate immobilized adenovirus resulted in significantly different expression profiles for each individual cross-linker. Furthermore, immobilization of adenoviral vectors effectively extended their transduction effectiveness beyond the initial phase of release. Transgene expression driven by adenovirus-tethered stents in rat carotid arteries demonstrated that a faster rate of cross-linker hydrolysis resulted in higher expression levels at day 1, which declined by day 8 after stent implantation, while inversely, slower hydrolysis was associated with increased arterial expression at day 8 in comparison with day 1. In conclusion, adjustable release of transduction-competent adenoviral vectors from metallic surfaces can be achieved, both in vitro and in vivo, through surface immobilization of adenoviral vectors using hydrolyzable cross-linkers with structure-specific release kinetics.
    Biomaterials 06/2013; 34(28). DOI:10.1016/j.biomaterials.2013.05.047 · 8.31 Impact Factor
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    • "These limitations prompted us to develop new protocols and designs for the formulation of the vector system and for testing the stability of the coatings and the release kinetics of the large pharmacological agents. Early pioneering work on the release of genes from coated stents by R.J. Levy's group [31] [32] [33] [34] [35] demonstrated feasibility for plasmid DNA-or adenoviral-mediated gene delivery. At present, strategies for delivering therapeutic genes via non-viral and viral gene transfers to the vessel wall include introducing them directly through catheters at the time of angioplasty [36] [37] [38] [39] or via gel-coated surfaces of the balloon [40] [41]. "
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    ABSTRACT: Despite the widespread use of drug eluting stents (DES), in-stent restenosis (ISR), delayed arterial healing and thrombosis remain important clinical complications. Gene-eluting stents (GES) represent a potential strategy for the prevention of ISR by delivering a therapeutic gene via a vector from the stent surface to the vessel wall. To this end, a model in vitro system was established to examine whether cationic liposomes could be used for gene delivery to human artery cells. Three different formulations were compared (DOTMA/DOPE, DDAB/DOPE or DDAB/POPC/Chol) to examine the effects of different cationic and neutral lipids on the transfection efficiency of lipoplex-coatings of metal surfaces. Upon completion of the characterization and optimization of the materials for gene delivery in vitro, these coatings were examined on a range of stents and deployed in a rabbit iliac artery injury model in vivo. Maximal transfection efficiencies for all coatings were observed on day 28, followed by declining, but persisting gene expression 42days after stent placement, thereby, presenting liposomal coatings for gene eluting stents as treatment options for clinical complications associated with stenting procedures.
    Journal of Controlled Release 02/2013; 167(2):109-119. DOI:10.1016/j.jconrel.2013.01.036 · 7.26 Impact Factor
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    • "The immobilization of ASNs over the HA-coated stent surface was efficient and their release was controlled from the surface. Animal and clinical studies have consistently shown that mural thrombosis and arterial VSMC proliferation occur predominantly near stent struts, and hence, a relatively small amount of stent-immobilized gene vectors strategically placed at the interface between the tissue and implant might be sufficient to produce a clinically significant therapeutic transduction of regional cells [20]. The spread of the vector to the non-target can be eliminated by attaching the complex on the surface of the stent, thereby protecting it from the shearing effect of the blood flow. "
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    ABSTRACT: Restenosis is the formation of blockages occurring at the site of angioplasty or stent placement. In order to avoid such blockages, the suppression of smooth muscle cells near the implanted stent is required. The Akt1 protein is known to be responsible for cellular proliferation, and specific inhibition of Akt1 gene expression results in the retardation of cell growth. To take advantage of these benefits, we developed a new delivery technique for Akt1 siRNA nanoparticles from a hyaluronic acid (HA)-coated stent surface. For this purpose, the disulfide cross-linked low molecular polyethyleneimine (PEI) (ssPEI) was used as a gene delivery carrier because disulfide bonds are stable in an oxidative extracellular environment but degrade rapidly in reductive intracellular environments. In this study, Akt1 siRNA showed efficient ionic interaction with the ssPEI carrier, which was confirmed by polyacrylamide gel electrophoresis. Akt1 siRNA/ssPEI nanoparticles (ASNs) were immobilized on the HA-coated stent surface and exhibited stable binding and localization, followed by time-dependent sustained release for intracellular uptake. Cellular viability on the nanoparticle-immobilized surface was assessed using A10 vascular smooth muscle cells, and the results revealed that immobilized ASNs exhibited negligible cytotoxicity against the adhering A10 cells. Transfection efficiency was quantified using a luciferase assay; the transgene expression of Akt1 suppression through the delivered Akt1 siRNA was measured using RT-PCR and western blot, demonstrating higher gene silencing efficiency when compared to other carriers. ASN coated on HA stents were deployed in the balloon-injured external iliac artery in rabbits in vivo. It was shown that the Akt1 released from the stent suppressed the growth of the smooth muscle at the peri-stent implantation area, resulting in the prevention of restenosis in the post-implantation phase.
    Biomaterials 08/2012; 33(33):8548-56. DOI:10.1016/j.biomaterials.2012.07.045 · 8.31 Impact Factor
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