Locally delivered nanoencapsulated tyrphostin (AGL-2043) reduces neointima formation in balloon-injured rat carotid and stented porcine coronary arteries

Nanoparticles in Drug Delivery: From History to Therapeutic Applications

Current research into the role of engineered nanoparticles in drug delivery systems (DDSs) for medical purposes has developed numerous fascinating nanocarriers. This paper reviews the various conventionally used and current used carriage system to deliver drugs. Due to numerous drawbacks of conventional DDSs, nanocarriers have gained immense interest. Nanocarriers like polymeric nanoparticles, mesoporous nanoparticles, nanomaterials, carbon nanotubes, dendrimers, liposomes, metallic nanoparticles, nanomedicine, and engineered nanomaterials are used as carriage systems for targeted delivery at specific sites of affected areas in the body. Nanomedicine has rapidly grown to treat certain diseases like brain cancer, lung cancer, breast cancer, cardiovascular diseases, and many others. These nanomedicines can improve drug bioavailability and drug absorption time, reduce release time, eliminate drug aggregation, and enhance drug solubility in the blood. Nanomedicine has introduced a new era for drug carriage by refining the therapeutic directories of the energetic pharmaceutical elements engineered within nanoparticles. In this context, the vital information on engineered nanoparticles was reviewed and conferred towards the role in drug carriage systems to treat many ailments. All these nanocarriers were tested in vitro and in vivo. In the coming years, nanomedicines can improve human health more effectively by adding more advanced techniques into the drug delivery system.

Application of the Nano-Drug Delivery System in Treatment of Cardiovascular Diseases

Cardiovascular diseases (CVDs) have become a serious threat to human life and health. Though many drugs acting via different mechanism of action are available in the market as conventional formulations for the treatment of CVDs, they are still far from satisfactory due to poor water solubility, low biological efficacy, non-targeting, and drug resistance. Nano-drug delivery systems (NDDSs) provide a new drug delivery method for the treatment of CVDs with the development of nanotechnology, demonstrating great advantages in solving the above problems. Nevertheless, there are some problems about NDDSs need to be addressed, such as cytotoxicity. In this review, the types and targeting strategies of NDDSs were summarized, and the new research progress in the diagnosis and therapy of CVDs in recent years was reviewed. Future prospective for nano-carriers in drug delivery for CVDs includes gene therapy, in order to provide more ideas for the improvement of cardiovascular drugs. In addition, its safety was also discussed in the review.

Nanoparticle Based Treatment for Cardiovascular Diseases

Nanotechnology has gained increased attention for delivering therapeutic agents effectively to the cardiovascular system. Heart targeted nanocarrier based drug delivery is a new, effective and efficacious approach for treating various cardiac related disorders such as atherosclerosis, hypertension, and myocardial infarction. Nanocarrier based drug delivery system circumvents the problems associated with conventional drug delivery systems, including their nonspecificity, severe side effects and damage to the normal cells. Modification of physicochemical properties of nanocarriers such as size, shape and surface modifications can immensely alter its invivo pharmacokinetic and pharmacodynamic data and will provide better treatment strategy. Several nanocarriers such as lipid, phospholipid nanoparticles have been developed for delivering drugs to the target sites within the heart. This review summarizes and increases the understanding of the advanced nanosized drug delivery systems for treating cardiovascular disorders with the promising use of nanotechnology.

Monocyte-mediated drug delivery systems for the treatment of cardiovascular diseases

Major advances have been achieved in understanding the mechanisms and risk factors leading to cardiovascular disorders and consequently developing new therapies. A strong inflammatory response occurs with a substantial recruitment of innate immunity cells in atherosclerosis, myocardial infarction, and restenosis. Monocytes and macrophages are key players in the healing process that ensues following injury. In the inflamed arterial wall, monocytes, and monocyte-derived macrophages have specific functions in the initiation and resolution of inflammation, principally through phagocytosis, and the release of inflammatory cytokines and reactive oxygen species. In this review, we will focus on delivery systems, mainly nanoparticles, for modulating circulating monocytes/monocyte-derived macrophages. We review the different strategies of depletion or modulation of circulating monocytes and monocyte subtypes, using polymeric nanoparticles and liposomes for the therapy of myocardial infarction and restenosis. We will further discuss the strategies of exploiting circulating monocytes for biological targeting of nanocarrier-based drug delivery systems for therapeutic and diagnostic applications.

Application of Light Scattering Techniques to Nanoparticle Characterization and Development

Over the years, the scientific importance of nanoparticles for biomedical applications has increased. The high stability and biocompatibility, together with the low toxicity of the nanoparticles developed lead to their use as targeted drug delivery systems, bioimaging systems, and biosensors. The wide range of nanoparticles size, from 10 nm to 1 μm, as well as their optical properties, allow them to be studied using microscopy and spectroscopy techniques. In order to be effectively used, the physicochemical properties of nanoparticle formulations need to be taken into account, namely, particle size, surface charge distribution, surface derivatization and/or loading capacity, and related interactions. These properties need to be optimized considering the final nanoparticle intended biodistribution and target. In this review, we cover light scattering based techniques, namely dynamic light scattering and zeta-potential, used for the physicochemical characterization of nanoparticles. Dynamic light scattering is used to measure nanoparticles size, but also to evaluate their stability over time in suspension, at different pH and temperature conditions. Zeta-potential is used to characterize nanoparticles surface charge, obtaining information about their stability and surface interaction with other molecules. In this review, we focus on nanoparticle characterization and application in infection, cancer and cardiovascular diseases.

Physicochemical characteristics of liposomes are decisive for their antirestenosis efficacy following local delivery

AIM

To develop an ameliorated sirolimus (SIR) liposome for intramural delivery, the effects of various carrier physicochemical parameters on the antirestenosis efficacy were evaluated.

MATERIALS & METHODS

Different liposomes were prepared, characterized and administered to balloon injured rats (12 animal groups). Their efficacies were investigated using morphometric, immunohistochemical and in vivo computed tomography imaging analyses.

RESULTS

The antirestenosis efficacy of SIR liposomes decreased in the following order: cationic 100 nm vesicles ≥ cationic 60 nm vesicles > neutral 100 nm vesicles ≥ stealth 100 nm vesicles > anionic 100 nm vesicles. The 100 µg SIR loaded in cationic liposomes showed almost no artery stenosis.

CONCLUSION

Appropriate modulation of physicochemical characteristics makes it possible to optimize the liposomes for local delivery.

Erythropoietin Induces Excessive Neointima Formation: A Study in a Rat Carotid Artery Model of Vascular Injury

A therapeutic strategy that would mitigate the events leading to hyperplasia and facilitate re-endothelialization of an injured artery after balloon angioplasty could be effective for a long-term patency of the artery. It is hypothesized that erythropoietin (EPO), which has both anti-inflammatory and antiapoptotic properties, will prevent hyperplasia, and its ability to proliferate and mobilize endothelial progenitor cells will re-endothelialize the injured artery. To test this hypothesis, EPO (5000 IU/kg) in solution was injected intraperitoneally 6 hours before vascular injury and then on every alternate day for a week or as a single dose (5000 IU/kg) in a sustained release gel formulation 1 week before the vascular injury. Morphometric analysis revealed nearly continuous re-endothelialization of the injured artery in EPO solution-treated animals (90% vs less than 20% in saline control); however, the treatment also caused excessive neointima formation (intima/media ratio, 2.10 ± 0.09 vs 1.60 ± 0.02 saline control, n = 5, P < .001). The EPO gel also induced similar excessive neointima formation. Immunohistochemical analysis of the injured arteries from the animals treated with EPO solution demonstrated a significant angiogenic response in adventitia and media, thus explaining the formation of excessive neointima. Although the results are in contrast to expectation, they explain a greater degree of stenosis seen in hemodialysis access fistulas in patients who are on EPO therapy for anemic condition. The results also caution the use of EPO, particularly in patients who are at a risk of vascular injury or are suffering from an atherosclerotic condition.

Nanotechnology in diagnosis and treatment of coronary artery disease

Nanotechnology could provide a new complementary approach to treat coronary artery disease (CAD) which is now one of the biggest killers in the Western world. The course of events, which leads to atherosclerosis and CAD, involves many biological factors and cellular disease processes which may be mitigated by therapeutic methods enhanced by nanotechnology. Nanoparticles can provide a variety of delivery systems for cargoes such as drugs and genes that can address many problems within the arteries. In order to improve the performance of current stents, nanotechnology provides different nanomaterial coatings, in addition to controlled-release nanocarriers, to prevent in-stent restenosis. Nanotechnology can increase the efficiency of drugs, improve local and systematic delivery to atherosclerotic plaques and reduce the inflammatory or angiogenic response after intravascular intervention. Nanocarriers have potential for delivery of imaging and diagnostic agents to precisely targeted destinations. This review paper will cover the current applications and future outlook of nanotechnology, as well as the main diagnostic methods, in the treatment of CAD.

Bioabsorbable stent quo vadis: a case for nano-theranostics

Percutaneous coronary intervention (PCI) is one of the most commonly performed invasive medical procedures in medicine today. Since the first coronary balloon angioplasty in 1977, interventional cardiology has seen a wide array of developments in PCI. Bare metal stents (BMS) were soon superseded by the revolutionary drug-eluting stents (DES), which aimed to address the issue of restenosis found with BMS. However, evidence began to mount against DES, with late-stent thrombosis (ST) rates being higher than that of BMS. The bioabsorbable stent may be a promising alternative, providing vessel patency and support for the necessary time required and thereafter degrade into safe non-toxic compounds which are reabsorbed by the body. This temporary presence provides no triggers for ST, which is brought about by non-endothelialized stent struts and drug polymers remaining in vivo for extended periods of time. Likewise, nano-theranostics incorporated into a bioabsorbable stent of the future may provide an incredibly valuable single platform offering both therapeutic and diagnostic capabilities. Such a stent may allow delivery of therapeutic particles to specific sites thus keeping potential toxicity to a minimum, improved ease of tracking delivery in vivo by embedding imaging agents, controlled rate of therapy release and protection of the implanted therapy. Indeed, nanocarriers may allow an increased therapeutic index as well as offer novel post-stent implantation imaging and diagnostic methods for atherosclerosis, restenosis and thrombosis. It is envisioned that a nano-theranostic stent may well form the cornerstone of future stent designs in clinical practice.

Regulation of smooth muscle cells in development and vascular disease: current therapeutic strategies

Vascular smooth muscle cells (SMCs) exhibit extensive phenotypic diversity and rapid growth during embryonic development, but maintain a quiescent, differentiated state in adult. The pathogenesis of vascular proliferative diseases involves the proliferation and migration of medial vascular SMCs into the vessel intima, possibly reinstating their embryonic gene expression programs. Multiple mitogenic stimuli induce vascular SMC proliferation through cell cycle progression. Therapeutic strategies targeting cell cycle progression and mitogenic stimuli have been developed and evaluated in animal models of atherosclerosis and vascular injury, and several clinical studies. Recent discoveries on the recruitment of vascular progenitor cells to the sites of vascular injury suggest new therapeutic potentials of progenitor cell-based therapies to accelerate re-endothelialization and prevent engraftment of SMC-lineage progenitor cells. Owing to the complex and multifactorial nature of SMC regulation, combinatorial antiproliferative approaches are likely to be used in the future in order to achieve maximal efficacy and reduce toxicity.

Nanoparticle drug- and gene-eluting stents for the prevention and treatment of coronary restenosis

Percutaneous coronary intervention (PCI) has become the most common revascularization procedure for coronary artery disease. The use of stents has reduced the rate of restenosis by preventing elastic recoil and negative remodeling. However, in-stent restenosis remains one of the major drawbacks of this procedure. Drug-eluting stents (DESs) have proven to be effective in reducing the risk of late restenosis, but the use of currently marketed DESs presents safety concerns, including the non-specificity of therapeutics, incomplete endothelialization leading to late thrombosis, the need for long-term anti-platelet agents, and local hypersensitivity to polymer delivery matrices. In addition, the current DESs lack the capacity for adjustment of the drug dose and release kinetics appropriate to the disease status of the treated vessel. The development of efficacious therapeutic strategies to prevent and inhibit restenosis after PCI is critical for the treatment of coronary artery disease. The administration of drugs using biodegradable polymer nanoparticles as carriers has generated immense interest due to their excellent biocompatibility and ability to facilitate prolonged drug release. Despite the potential benefits of nanoparticles as smart drug delivery and diagnostic systems, much research is still required to evaluate potential toxicity issues related to the chemical properties of nanoparticle materials, as well as to their size and shape. This review describes the molecular mechanism of coronary restenosis, the use of DESs, and progress in nanoparticle drug- or gene-eluting stents for the prevention and treatment of coronary restenosis.

Delivery of Polymeric Nanoparticles to Target Vascular Diseases

Current advances in nanotechnology have paved the way for the early detection, prevention and treatment of various diseases such as vascular disorders and cancer. These advances have provided novel approaches or modalities of incorporating or adsorbing therapeutic, biosensor and targeting agents into/on nanoparticles. With significant progress, nanomedicine for vascular therapy has shown significant advantages over traditional medicine because of its ability to selectively target the disease site and reduce adverse side effects. Targeted delivery of nanoparticles to vascular endothelial cells or the vascular wall provides an effective and more efficient way for early detection and/or treatment of vascular diseases such as atherosclerosis, thrombosis and Cerebrovascular Amyloid Angiopathy (CAA). Clinical applications of biocompatible and biodegradable polymers in areas such as vascular graft, implantable drug delivery, stent devices and tissue engineering scaffolds have advanced the candidature of polymers as potential nano-carriers for vascular-targeted delivery of diagnostic agents and drugs. This review focuses on the basic aspects of the vasculature and its associated diseases and relates them to polymeric nanoparticle-based strategies for targeting therapeutic agents to diseased vascular site.

Role of biomaterials in prevention of in-stent restenosis

Coronary balloon angioplasty and coronary stenting are the procedures used in healing coronary artery disease. However, injury of arteries during angioplasty and stenting causes cell stimulations in tissue. Cell movement and thrombosis lead to re-narrowing of widened vessel called restenosis. Several new types of carriers and technology have been developed to suppress and/or prevent restenosis. Authors review the polymeric materials featured in drug/gene carrier systems, nanovehicles, and stent coating materials against restenosis.

Sirolimus-loaded stealth colloidal systems attenuate neointimal hyperplasia after balloon injury: a comparison of phospholipid micelles and liposomes

Restenosis after angioplasty remains a serious complication in clinical cardiology. This study aims to investigate the stealth colloidal systems for local intra-arterial drug delivery. Micelles from polyethylene glycol conjugated with phosphatidylethanolamine and PEGylated liposomes loaded with sirolimus were prepared and characterized with regard to their loading efficiency, particle size distribution, zeta potential, morphology, nuclear magnetic resonance spectroscopy, drug release profile and stability. The antirestenotic effects of the sirolimus-loaded micelles (14 nm) and liposomes (90 nm) were evaluated and compared in the rat carotid injury model following local intravascular delivery. In comparison to control groups, treatment of balloon injured rats with drug loaded micelles and nanoliposomes significantly reduced vascular stenosis by 42% and 19%, respectively (P<0.05). In addition, the luminal area was significantly enlarged by 39% and 60% following treatment with sirolimus-loaded liposomes and micelles, respectively (P<0.05). Immunohistochemistry revealed that sirolimus-loaded nanocarriers suppressed cell proliferation (Ki67-positive cells) as compared to control groups without affecting the density of smooth muscle actin staining. These results suggest that both colloidal nanocarriers could serve as effective intramural drug delivery systems for the treatment of restenosis; however, phospholipid based micelles provided better antirestenotic effects than PEGylated liposomes.

The changing face of vascular interventional radiology: the future role of pharmacotherapies and molecular imaging

Interventional radiology has had to evolve constantly because there is the ever-present competition and threat from other specialties within medicine, surgery, and research. The development of new technologies, techniques, and therapies is vital to broaden the horizon of interventional radiology and to ensure its continued success in the future. In part, this change will be due to improved chronic disease prevention altering what we treat and in whom. The most important of these strategies are the therapeutic use of statins, Beta-blockers, angiotensin-converting enzyme inhibitors, and substances that interfere with mast cell degeneration. Molecular imaging and therapeutic strategies will move away from conventional techniques and nano and microparticle molecular technology, tissue factor imaging, gene therapy, endothelial progenitor cells, and photodynamic therapy will become an important part of interventional radiology of the future. This review looks at these new and exciting technologies.

Nanomedicine in cardiovascular therapy: recent advancements

Cardiovascular disease (CVD) is comprised of a group of disorders affecting the heart and blood vessels of the human body and is one of the leading causes of death worldwide. Current therapy for CVD is limited to the treatment of already established disease, and it includes pharmacological and/or surgical procedures, such as percutaneous coronary intervention with stenting and coronary artery bypass grafting. However, lots of complications have been raised with these modalities of treatment, including systemic toxicity with medication, stent thrombosis with percutaneous coronary intervention and nonsurgical candidate patients for coronary artery bypass grafting. Nanomedicine has emerged as a potential strategy in dealing with these obstacles. Applications of nanotechnology in medicine are already underway and offer tremendous promise. This review explores the recent developments of nanotechnology in the field of CVD and gives an insight into its potential for diagnostics and therapeutics applications. The authors also explore the characteristics of the widely used biocompatible nanomaterials for this purpose and evaluate their opportunities and challenges for developing novel nanobiotechnological tools with high efficacy for biomedical applications, such as radiological imaging, vascular implants, gene therapy, myocardial infarction and targeted delivery systems.

Recent advances in drug eluting stents

One of the most common medical interventions to reopen an occluded vessel is the implantation of a coronary stent. While this method of treatment is effective initially, restenosis, or the re-narrowing of the artery frequently occurs largely due to neointimal hyperplasia of smooth muscle cells. Drug eluting stents were developed in order to provide local, site-specific, controlled release of drugs that can inhibit neointima formation. By implementing a controlled release delivery system it may be possible to control the time release of the pharmacological factors and thus be able to bypass some of the critical events associated with stent hyperplasia and prevent the need for subsequent intervention. However, since the advent of first-generation drug eluting stents, long-term adverse effects have raised concerns regarding their safety. These limitations in safety and efficacy have triggered considerable research in developing biodegradable stents and more potent drug delivery systems. In this review, we shed light on the current state-of-the-art in drug eluting stents, problems related to them and highlight some of the ongoing research in this area.

Nanoparticle-mediated local delivery of an antisense TGF-β1 construct inhibits intimal hyperplasia in autogenous vein grafts in rats

Background

Intimal hyperplasia is one of the most important causes of vascular graft failure. Numerous studies have correlated transforming growth factor-β1 (TGF-β1) with extracellular matrix (ECM) deposition, a hallmark of intimal thickening.

Principal Findings

In the present study, we performed immunohistochemistry, RT-PCR, and Western blot to examine the dynamic expression of TGF-β1, TGF-β1 receptor type I (TGF-β RI), matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) during intimal hyperplasia in grafted veins of a rat model generated by grafting a portion of the right internal jugular vein to the ipisiliary caroid artery. Additionally, we determined whether nanoparticle-mediated delivery of a TGF-β1 antisense-expressing construct prevented TGF-β1 expression and intimal hyperplasia in grafted veins. In grafted veins, the expression of TGF-β1 significantly increased on day 3 after transplantation, peaked on day 7, slightly decreased on day 14, and returned to baseline levels on day 28. The positive expression of TGF-β RI in grafted veins remarkably increased on day 7, peaked on day 14, and decreased thereafter. MMP-1 expression decreased significantly, while TIMP-1 expression increased, significantly on days 14 and 28. Nanoparticle-mediated delivery of a TGF-β1 antisense-expressing construct down-regulated TGF-β1 expression and inhibited intimal hyperplasia in grafted veins.

Conclusions

Our findings provide further evidence that TGF-β1 plays an integral role in the development of intimal hyperplasia after vascular injury. Nanoparticle-mediated delivery of a TGF-β1 antisense-expressing construct is a feasible strategy to target TGF-β1-induced intimal thickening.

MANUFACTURING AND NEAR-PHYSIOLOGICAL TESTING OF A BIODEGRADABLE METALLIC CORONARY STENT (BMCS)

Permanent metallic stents are frequently used in cardiovascular interventions, due to the many advantages metals possess in bulk and surface properties, design and chemistry, as well as their high modulus and ease of producing thin sections. However, the presence of foreign bodies in humans is associated with many long-term safety concerns; removal of the stent is therefore preferred through a second intervention after recovery. Based primarily on this consideration, biodegradable stents have been of significant interest in the past few years. This paper reports the manufacturing and near-physiological testing of a novel Biodegradable Metallic Coronary Stent (BMCS). To date, very limited literature is available on this aspect of research. Generally, magnesium is reactive and generally difficult to process. However, preliminary results demonstrate strong feasibility of fabricating low-profiled magnesium-based biodegradable coronary stents. Near-physiological tests based on a specially designed accelerated radial stent fatigue system were carried out. Results show that the biodegradable stents retained their arterial scaffolding functions for up to one year (simulated) before totally being resorbed into the biological fluid past its point of functionality. The results obtained so far show great promise for application.

Nanomedicine approaches in vascular disease: a review

Nanomedicine approaches have revolutionized the treatment of cancer and vascular diseases, where the limitations of rapid nonspecific clearance, poor biodistribution and harmful side effects associated with direct systemic drug administration can be overcome by packaging the agents within sterically stabilized, long-circulating nanovehicles that can be further surface-modified with ligands to actively target cellular/molecular components of the disease. With significant advancements in genetics, proteomics, cellular and molecular biology and biomaterials engineering, the nanomedicine strategies have become progressively refined regarding the modulation of surface and bulk chemistry of the nanovehicles, control of drug release kinetics, manipulation of nanoconstruct geometry and integration of multiple functionalities on single nanoplatforms. The current review aims to capture the various nanomedicine approaches directed specifically toward vascular diseases during the past two decades. Analysis of the promises and limitations of these approaches will help identify and optimize vascular nanomedicine systems to enhance their efficacy and clinical translation in the future.

FROM THE CLINICAL EDITOR

Nanomedicine-based approaches have had a major impact on the treatment and diagnosis of malignancies and vascular diseases. This review discusses various nanomedicine approaches directed specifically toward vascular diseases during the past two decades, highlighting their advantages, limitations and offering new perspectives on future applications.

Nanotechnology for the treatment of coronary in stent restenosis: a clinical perspective

Coronary in stent restenosis remains a significant limitation to the long term efficacy of coronary artery stent placement. In this review the authors review the pathophysiology of coronary in stent restenosis, together with an overview of the current treatment modalities. The potential clinical utility of nanotechnology is also reviewed.The first human safety trial of systemic nanoparticle paclitaxel (nab-paclitaxel) for in stent restenosis (SNAPIST-I) is discussed. The results showed no significant adverse advents attributable to the nab-paclitaxel at 10 or 30 mg/m2, although moderate neutropenia, sensory neuropathy and mild to moderate reversible alopecia occurred at higher doses. No major adverse cardiac events were recorded at 2 months, whilst at 6 months, 4 target lesions required revascularisation. The investigators concluded therefore that systemic nab-paclitaxel was well tolerated at a dose of <70 mg/m2. To date however, no formal clinical evaluation has been reported as to the clinical utility of nab-paclitaxel, or any of the nano preparations discussed, for the suppression of coronary in stent restenosis.

Emerging applications of nanomedicine for the diagnosis and treatment of cardiovascular diseases

Nanomedicine is an emerging field that utilizes nanotechnology concepts for advanced therapy and diagnostics. This convergent discipline merges research areas such as chemistry, biology, physics, mathematics and engineering. It therefore bridges the gap between molecular and cellular interactions, and has the potential to revolutionize medicine. This review presents recent developments in nanomedicine research poised to have an important impact on the treatment of cardiovascular disease. This will occur through improvement of the diagnosis and therapy of cardiovascular disorders as atherosclerosis, restenosis and myocardial infarction. Specifically, we discuss the use of nanoparticles for molecular imaging and advanced therapeutics, specially designed drug eluting stents and in vivo/ex vivo early detection techniques.

Biodegradable Sirolimus-loaded Poly(lactide) Nanoparticles as Drug Delivery System for the Prevention of In-Stent Restenosis in Coronary Stent Application

The administration of drugs using biodegradable polymer nanoparticles as carriers has generated immense interest due to their excellent biocompatibility and the prolonged drug release. The scope of this work was to determine the applicability of sirolimus-loaded biodegradable poly(D,L-lactide) (PDLLA) nanoparticles as drug carriers to prevent restenotic processes after stent implantation. The average 250 nm sized 20%(w/w) sirolimus-loaded nanoparticles were extensively characterized with regard to in vitro degradation, biocompatibility and in vitro drug release. The particles show biphasic release kinetics consisting of a short burst release of 50%(w/w) sirolimus payload, followed by a longer, slower release phase, which are desirable for the application as a drug delivery carrier. All presented results exhibit the potential of sirolimus-loaded PDLLA nanoparticles as promising local and sustained drug delivery systems administered intraluminally to reduce in-stent restenosis after stent implantation.

New therapeutic possibilities for vein graft disease in the post-edifoligide era

Vein graft neointimal hyperplasia involves proliferation and migration of vascular smooth muscle cells into the vessel intima, and ultimately engenders accelerated atherosclerosis and vein graft failure. Since a myriad of stimuli provoke smooth muscle cell proliferation, molecular therapies for vein graft disease have targeted mechanisms fundamental to all cell proliferation - the 'cell-cycle' machinery. Preclinically, the most successful of these therapies has been edifoligide (E2F decoy), a double-stranded oligodeoxynucleotide that binds to the transcription factor known as E2F. Recently, PRoject of Ex vivo vein GRaft Engineering via Transfection (PREVENT) III and IV demonstrated that edifoligide failed to benefit human vein grafts employed to treat lower-extremity ischemia and coronary heart disease, respectively. The clinical failure of edifoligide calls into question previous models of vein graft disease and lends credence to recent animal studies demonstrating that vein graft arterialization substantially involves the immigration into the vein graft of a variety of vascular progenitor cells. Future vein graft disease therapies will likely target not only proliferation of graft-intrinsic cells, but also immigration of graft-extrinsic cells.

Stent-based release of a selective PDGF-receptor blocker from the bis-indolylmethanon class inhibits restenosis in the rabbit animal model

Long-term success of modern therapies for myocardial ischemia is limited by restenosis, with proliferation and migration of vascular smooth muscle cells (VSMC) as key events. Since findings in recent years indicate, that the Platelet Derived Growth Factor (PDGF) is an important selective factor in mitogenic and motogenic pathways of VSMC, different concepts for reducing restenosis by inhibiting PDGF signaling have been investigated, with local delivery of small receptor kinase inhibitors looking most promising. We tested the stent-based delivery of the PDGF-receptor inhibitor D-65495, a bis(1H-2-indolyl)methanone, in the rabbit iliac artery model of restenosis. New Zealand white rabbits underwent balloon dilation of iliac arteries for implantation of D-65495-coated or non-coated (solvent, either DMSO or 90%THF / 10% DMSO) coronary stents. After 4 weeks stents were removed and neointima formation in medial and proximal/ distal stent sections was histomorphometrically and immunohistochemically analyzed. Arteries with D-65495 eluting stents showed an up to 50% reduced restenosis compared to control stents. Also, the neointimal area was reduced, but there were no significant differences in injury score. Importantly, endothelialization was similar for control stents as well as for D-65495-coated stents, suggesting absence of a general cytostatic effect of the inhibitor. The impact of D-65495 on PDGF-receptor signaling in the vessel wall was indirectly assessed by immunohistochemical staining for activated protein kinase Akt, and PCNA as a proliferation marker and revealed some reduction for the inhibitor-treated vessels. In conclusion, the application of D-65495 caused a significant decrease in neointima formation, further supporting the concept of using locally released PDGF-receptor kinase inhibitors as anti-restenotic agents.

Production and in vitro characterization of lisinopril-loaded nanoparticles for the treatment of restenosis in stented coronary arteries

Lisinopril, an angiotensin converting enzyme (ACE) inhibitor drug, was encapsulated in poly(lactide-co-glicolide) (PLGA) nanoparticles (NP) for site-specific delivery by catheters in prevention of restenosis. NP were prepared by emulsification-diffusion method. The PLGA type, stabilizing agent type and its concentration were studied as process variables. The z-average particle size varied between 265-412 nm. The highest zeta potential was seen in NP prepared with Pluronic F-68. None of the studied variables or their interactions had a significant effect on the particle size while all had main effect on the zeta potential. The highest entrapment efficiency was 93% and all studied variables and their interactions except PLGA type and its interaction with the stabilizer type had significant effects on the loading. Baker-Lonsdale model was the most appropriate model for release of lisinopril from NP. Five per cent PLGA 75:25 and 5% Pluronic F-68 showed promising results for 21 days release of lisinopril as an anti-restenotic agent.

Development of cardiovascular bypass grafts: endothelialization and applications of nanotechnology

There is a critical clinical need for small-diameter bypass grafts, with applications involved in the coronary artery and lower limb. Commercially available materials give rise to unfavorable responses when in contact with blood and subjected to low-flow hemodynamics and, thus, are nonideal as small-diameter bypass grafts. Optimizing the mechanical properties to match both the native artery and the graft surfaces has received keen attention. Endothelialization of bypass grafts is considered a protective mechanism where the biochemicals produced from endothelial cells exert a range of favorable responses, including antithrombotic, noninflammatory responses and inhibition of intimal hyperplasia. In situ endothelialization is most desirable. Nanotechnology approaches facilitate all aspects of endothelialization, including endothelial progenitor cell mobilization, migration, adhesion, proliferation and differentiation. 'Surface nanoarchitecturing mechanisms', which mimic the natural extracellular matrix to optimize endothelial progenitor cell interaction and controlled delivery of various factors in the form of nanoparticles, which can be combined with gene therapy, are of keen interest. This article discusses the development of bypass grafts, focusing on the optimization of the biological properties of mechanically suitable grafts.

Predicting in vivo efficacy of potential restenosis therapies by cell culture studies: species-dependent susceptibility of vascular smooth muscle cells

Although drug-eluting stents (DES) are successfully utilized for restenosis therapy, the development of local and systemic therapeutic means including nanoparticles (NP) continues. Lack of correlation between in vitro and in vivo studies is one of the major drawbacks in developing new drug delivery systems. The present study was designed to examine the applicability of the arterial explant outgrowth model, and of smooth muscle cells (SMC) cultures for prescreening of possible drugs. Elucidation of different species sensitivity (rat, rabbit, porcine and human) to diverse drugs (tyrphostins, heparin and bisphsophonates) and a delivery system (nanoparticles) could provide a valuable screening tool for further in vivo studies. The anticipated sensitivity ranking from the explant outgrowth model and SMC mitotic rates (porcine>rat>>rabbit>human) do not correlate with the observed relative sensitivity of those animals to antiproliferative therapy in restenosis models (rat≥rabbit>porcine>human). Similarly, the inhibitory profile of the various antirestenotic drugs in SMC cultures (rabbit>porcine>rat>>human) do not correlate with animal studies, the rabbit- and porcine-derived SMC being highly sensitive. The validity of in vitro culture studies for the screening of controlled release delivery systems such as nanoparticles is limited. It is suggested that prescreening studies of possible drug candidates for restenosis therapy should include both SMC cell cultures of rat and human, appropriately designed with a suitable serum.

Delivery of large biopharmaceuticals from cardiovascular stents: a review

This review focuses on new and emerging large-molecule bioactive agents delivered from stent surfaces in drug-eluting stents (DESs) to inhibit vascular restenosis in the context of interventional cardiology. New therapeutic agents representing proteins, nucleic acids (small interfering RNAs and large DNA plasmids), viral delivery vectors, and even engineered cell therapies require specific delivery designs distinct from traditional smaller-molecule approaches on DESs. While small molecules are currently the clinical standard for coronary stenting, extension of the DESs to other lesion types, peripheral vasculature, and nonvasculature therapies will seek to deliver an increasingly sophisticated armada of drug types. This review describes many of the larger-molecule and biopharmaceutical approaches reported recently for stent-based delivery with the challenges associated with formulating and delivering these drug classes compared to the current small-molecule drugs. It also includes perspectives on possible future applications that may improve safety and efficacy and facilitate diversification of the DESs to other clinical applications.

Nanotechnology in the diagnosis and management of heart, lung and blood diseases

Heart, lung and blood diseases exert an enormous toll, accounting for almost half of the deaths in the USA each year. In addition to the morbidity and mortality resulting from these diseases, there is also a high economic burden, estimated at 560 billion US dollars for 2006. Nanotechnology offers a broad range of opportunities to improve diagnosis and therapy for cardiovascular, pulmonary and hematopoietic diseases, thereby decreasing these burdens. This review will focus on four areas of particular promise for the application of nanotechnology: imaging, diagnostics and biosensors, drug delivery and therapy, and tissue engineering and repair. The goal is to summarize the current state of science and technology in these areas and to look at future directions that the field is likely to move in to enhance the diagnosis and treatment of heart, lung and blood diseases.

Vitamin E TPGS-emulsified poly(lactic-co-glycolic acid) nanoparticles for cardiovascular restenosis treatment

AIMS

Paclitaxel is one of the most effective antiproliferative agents and it has been applied in the development of drug-eluting stents. There are difficulties, however, in using paclitaxel in clinical applications owing to its poor solubility and side effects. We have synthesized nanoparticles of biodegradable polymers for the effective and sustainable delivery of paclitaxel and other antiproliferative agents for restenosis treatment.

METHODS & RESULTS

Paclitaxel-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles were prepared by a modified solvent extraction/evaporation method with D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) or polyvinyl alcohol (PVA) as an emulsifier. Drug-loaded nanoparticles were characterized for size and size distribution, surface morphology, surface charge, drug-encapsulation efficiency and in vitro drug-release kinetics. Cellular uptake of fluorescent nanoparticles was investigated in vitro in coronary artery smooth muscle cells and in vivo in the carotid arteries of rabbits. The antiproliferative effects of the nanoparticle formulations were assessed in vitro in close comparison with Taxol((R)). Both the PVA- and TPGS-emulsified nanoparticles have similar size and size distribution, surface morphology and dispersion stability and showed great advantages over paclitaxel in in vitro cellular uptake and cytotoxicity than Taxol. The TPGS-emulsified nanoparticle formulation has higher drug-encapsulation efficiency, cellular uptake and cytotoxicity than the PVA-emulsified nanoparticle formulation. IC(50) in 24-h culture with coronary artery smooth muscle cells is 748 ng/ml for paclitaxel, 708 ng/ml for PVA-emulsified nanoparticles and 474 ng/ml for TPGS-emulsified nanoparticles, respectively.

CONCLUSION

TPGS-emulsified PLGA nanoparticles have great potential for the effective and sustainable delivery of antiproliferative agents and for the development of nanoparticle-coated stents, which may become the third generation of cardiovascular stents.

Nano- and microparticle-based imaging of cardiovascular interventions: overview

The rapid progress of nanoscience and the application of nanotechnology are changing the foundations of diagnosis, treatment, and prevention of cardiovascular diseases. As the core of nanotechnology, nano- and microparticles offer "three-in-one" functions as imaging agents, target probes, and therapeutic carriers. While nano- and microparticle-based imaging of cardiovascular interventions is still in its developing phase, it has already presented the exciting potential to monitor primary interventional procedures for precise therapeutic delivery, enhance the effectiveness of delivered therapeutics, and monitor therapeutic efficiency after interventions performed to treat cardiovascular diseases. This article provides an overview of the current status of the application of nano- and microparticles in the imaging of cardiovascular interventions.

Introduction to Nanotechnology

Nanotechnology is a scientific movement that has the potential to transform the diagnosis and treatment of disease in the 21st century. The area of investigation is defined by the study, design, manipulation, manufacture, and control of materials or devices by physical or chemical means at resolutions on the order of one billionth of a meter. The potential for a wide range of clinical applications makes a basic understanding of nanotechnology important to physiatrists. This review presents an introduction to nanotechnology and discusses key developments in tissue engineering, drug delivery, imaging, diagnostics, surface texturing, and biointerfaces that could impact the practice of physiatry in the future.

Nanosuspensions of alendronate with gallium or gadolinium attenuate neointimal hyperplasia in rats

Monocytes/macrophages play a pivotal role in the formation of neointinal hyperplasia following vascular injury. Transient depletion of circulating monocytes by particulate delivery systems containing bisphosphonates, such as alendronate, results in restenosis inhibition. We hypothesized that a self-suspendable nanoparticulate dosage form, with a minimum amount of expients, could be formulated by complexing the negatively charged alendronate with gallium or gadolinium. We further hypothesized that a synergistic biological effect could be obtained by nanosuspensions of alendronate with these counter ions. Nanosuspensions (150-250 nm) of alendronate-gallium and alendronate-gadolinium were successfully formulated with no additives except for the active agents and HCl for pH adjustment. Both nanosuspensions exhibited macrophage cell line growth inhibition in a dose-response relationship in comparison to the various agents in solution and in liposomes. A synergistic effect of the nanosuspensions was observed in the inhibition of raw264 macrophages, and in reducing IL-1beta and TNF-alpha secretion in cell culture. Single IV administration at the time of injury, of alendronate-gallium or alendronate-gadolinium nanosuspensions resulted in inhibition of neointimal hyperplasia and stenosis in the rat model of vascular injury. The results correlated with the significant reduction of circulating monocytes. The nanosuspensions possess the advantages of no additives for minimal provocation of side effects, and the potential of immunomodulating inflammatory disorders.

The promise of nanotechnology for heart, lung and blood diseases

Nanotechnology offers a broad range of opportunities for improving the diagnosis and therapy for heart, lung and blood diseases, and drug delivery represents an area of particular promise. For cardiovascular disease, the treatment of atherosclerotic plaque and prevention of restenosis following stent placement offer attractive targets for nanotechnology. In lung disease, nanotechnology may provide novel treatments for a broad range of intractable pulmonary diseases, including bacterial biofilms, fungal infections, and tuberculosis. For haematopoietic diseases, targeted delivery of drugs to lymphocytes may represent a strategy for reducing systemic cytotoxicity. This editorial discusses some of the more promising targets for nanotechnology-based treatment of heart, lung and blood diseases.

PDGF receptor kinase inhibitors for the treatment of PDGF driven diseases

PDGF and its receptors are involved in a variety of diseases: cancers, atherosclerosis, balloon injury induced restenosis, pulmonary fibrosis and more. In all cases enhanced signaling of the receptor is the hallmark. In some cases, like chronic monomyelocytic leukemia (CMML), the persistent PDGFR signaling is essential for the survival of the cancer cell. These findings induced the research community as well as the pharmaceutical industry to develop agents that block PDGFR signaling. The possible utilization of PDGFR kinase inhibitors as anti-restenosis agents is likely to move ahead of the utilization of these agents to treat human malignancies.