Liposomal surface coatings of metal stents for efficient non-viral gene delivery to the injured vasculature

Nanomaterial coatings applied on stent surfaces

The advent of percutaneous coronary intervention and intravascular stents has revolutionized the field of interventional cardiology. Nonetheless, in-stent restenosis, inflammation and late-stent thrombosis are the major obstacles with currently available stents. In order to enhance the hemocompatibility of stents, advances in the field of nanotechnology allow novel designs of nanoparticles and biomaterials toward localized drug/gene carriers or stent scaffolds. The current review focuses on promising polymers used in the fabrication of newer generations of stents with a short synopsis on atherosclerosis and current commercialized stents, nanotechnology's impact on stent development and recent advancements in stent biomaterials is discussed in context.

Stent-based delivery of adeno-associated viral vectors with sustained vascular transduction and iNOS-mediated inhibition of in-stent restenosis

In-stent restenosis remains an important clinical problem in the era of drug eluting stents. Development of clinical gene therapy protocols for the prevention and treatment of in-stent restenosis is hampered by the lack of adequate local delivery systems. Herein we describe a novel stent-based gene delivery platform capable of providing local arterial gene transfer with adeno-associated viral (AAV) vectors. This system exploits the natural affinity of protein G (PrG) to bind to the Fc region of mammalian IgG, making PrG a universal adaptor for surface immobilization of vector-capturing antibodies (Ab). Our results: 1) demonstrate the feasibility of reversible immobilization of AAV2 vectors using vector tethering by AAV2-specific Ab appended to the stent surface through covalently attached PrG, 2) show sustained release kinetics of PrG/Ab-immobilized AAV2 vector particles into simulated physiological medium in vitro and site-specific transduction of cultured cells, 3) provide evidence of long-term (12 weeks) arterial expression of luciferase with PrG/Ab-tethered AAV2_Luc, and 4) show anti-proliferative activity and anti-restenotic efficacy of stent-immobilized AAV2_iNOS in the rat carotid artery model of stent angioplasty.

Gene Delivery from Stents for Prevention of In-Stent Restenosis

The increasing sophistication of vascular stent design, especially devices that combine mechanical support with local drug delivery to the vascular wall, has resulted in major progress in the management of coronary and peripheral artery disease. This progress is reflected in expanded anatomical and clinical indications for stent angioplasty, with complementary reduction in bypass surgery rates and decreased need for target-lesion revascularisation. Nevertheless, even with second-generation drug-eluting stents (DES), the most common cause of stent failure, in-stent restenosis, while <10%, generates high numbers of cases due to the large scale of stent use (there are >1 million stent angioplasty procedures yearly in the USA alone). Gene-eluting stents (GES), the next generation of stent devices now in the preclinical phase of development, have evolved over the past two decades around the concept of localised vessel wall delivery of gene vectors attached to the stent struts. GES potentially provide several important advantages over DES, such as prolonged or even permanent anti-restenotic effect, capacity to deliver dissimilar impact on smooth muscle cells and endothelium, and fine-tuning of transgene expression and pharmacological effect with systemically administered therapeutics. Furthermore, GES can be used for treating non-occlusive lesions with the aim of slowing the underlying atherosclerotic process in the vessel wall. GES research at this time is concerned with achieving effective and safe transgene overexpression in the stented arteries, optimal vector choice, and proper techniques for vector immobilisation on the stent struts.

Nitric Oxide Releasing Coronary Stent: A New Approach Using Layer-by-Layer Coating and Liposomal Encapsulation

The sustained or controlled release of nitric oxide (NO) can be the most promising approach for the suppression or prevention of restenosis and thrombosis caused by stent implantation. The aim of this study is to investigate the feasibility in the potential use of layer-by-layer (LBL) coating with a NO donor-containing liposomes to control the release rate of NO from a metallic stent. Microscopic observation and surface characterizations of LBL-modified stents demonstrate successful LBL coating with liposomes on a stent. Release profiles of NO show that the release rate is sustained up to 5 d. In vitro cell study demonstrates that NO release significantly enhances endothelial cell proliferation, whereas it markedly inhibits smooth muscle cell proliferation. Finally, in vivo study conducted with a porcine coronary injury model proves the therapeutic efficacy of the NO-releasing stents coated by liposomal LBL technique, supported by improved results in luminal healing, inflammation, and neointimal thickening except thrombo-resistant effect. As a result, all these results demonstrate that highly optimized release rate and therapeutic dose of NO can be achieved by LBL coating and liposomal encapsulation, followed by significantly efficacious outcome in vivo.

The metamorphosis of vascular stents: passive structures to smart devices

The role of nanotechnology enabled techniques in the evolution of vascular stents.

Endovascular Gene Delivery from a Stent Platform: Gene- Eluting Stents

A synergistic impact of research in the fields of post-angioplasty restenosis, drug-eluting stents and vascular gene therapy over the past 15 years has shaped the concept of gene-eluting stents. Gene-eluting stents hold promise of overcoming some biological and technical problems inherent to drug-eluting stent technology. As the field of gene-eluting stents matures it becomes evident that all three main design modules of a gene-eluting stent: a therapeutic transgene, a vector and a delivery system are equally important for accomplishing sustained inhibition of neointimal formation in arteries treated with gene delivery stents. This review summarizes prior work on stent-based gene delivery and discusses the main optimization strategies required to move the field of gene-eluting stents to clinical translation.