Intramural delivery of rapamycin with alphavbeta3-targeted paramagnetic nanoparticles inhibits stenosis after balloon injury

Angiogenesis imaging with vascular-constrained particles: the why and how

Angiogenesis is a keystone in the treatment of cancer and potentially many other diseases. In cancer, first-generation antiangiogenic therapeutic approaches have demonstrated survival benefit in subsets of patients, but their high cost and notable adverse side effect risk have fueled alternative development efforts to personalize patient selection and reduce off-target effects. In parallel, rapid advances in cost-effective genomic profiling and sensitive early detection of high-risk biomarkers for cancer, atherosclerosis, and other angiogenesis-related pathologies will challenge the medical imaging community to identify, characterize, and risk stratify patients early in the natural history of these disease processes. Conventional diagnostic imaging techniques were not intended for such sensitive and specific detection, which has led to the emergence of novel noninvasive biomedical imaging approaches. The overall intent of molecular imaging is to achieve greater quantitative characterization of pathologies based on microanatomical, biochemical, or functional assessments; in many approaches, the capacity to deliver effective therapy, e.g., antiangiogenic therapy, can be combined. Agents with both diagnostic and therapy attributes have acquired the moniker "theranostics." This review will explore biomedical imaging options being pursued to better segment and treat patients with angiogenesis-influenced disease using vascular-constrained contrast platform technologies.

Multifunctional agents for concurrent imaging and therapy in cardiovascular disease

The development of agents for the simultaneous detection and treatment of disease has recently gained significant attention. These multifunctional theranostic agents posses a number of advantages over their monofunctional counterparts, as they potentially allow for the concomitant determination of agent localization, release, and efficacy. Whereas the development of these agents for use in cancers has received the majority of the attention, their use in cardiovascular disease is steadily increasing. As such, this review summarized some of the most poignant recent advances in the development of theranostic agents for the treatment of this class of diseases.

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.

Imaging atherosclerosis and vulnerable plaque

Identifying patients at high risk for an acute cardiovascular event such as myocardial infarction or stroke and assessing the total atherosclerotic burden are clinically important. Currently available imaging modalities can delineate vascular wall anatomy and, with novel probes, target biologic processes important in plaque evolution and plaque stability. Expansion of the vessel wall involving remodeling of the extracellular matrix can be imaged, as can angiogenesis of the vasa vasorum, plaque inflammation, and fibrin deposits on early nonocclusive vascular thrombosis. Several imaging platforms are available for targeted vascular imaging to acquire information on both anatomy and pathobiology in the same imaging session using either hybrid technology (nuclear combined with CT) or MRI combined with novel probes targeting processes identified by molecular biology to be of importance. This article will discuss the current state of the art of these modalities and challenges to clinical translation.

Theragnostics for tumor and plaque angiogenesis with perfluorocarbon nanoemulsions

Molecular imaging agents are extending the potential of noninvasive medical diagnosis from basic gross anatomical descriptions to complicated phenotypic characterizations based upon the recognition of unique cell-surface biochemical signatures. Although originally the purview of nuclear medicine, "molecular imaging" is now studied in conjunction with all clinically relevant imaging modalities. Of the myriad of particles that have emerged as prospective candidates for clinical translation, perfluorocarbon nanoparticles offer great potential for combining targeted imaging with drug delivery, much like the "magic bullet" envisioned by Paul Ehrlich 100 years ago. Perfluorocarbon nanoparticles, once studied in Phase III clinical trials as blood substitutes, have found new life for molecular imaging and drug delivery. The particles have been adapted for use with all clinically relevant modalities and for targeted drug delivery. In particular, their intravascular constraint due to particle size provides a distinct advantage for angiogenesis imaging and antiangiogenesis therapy. As perfluorocarbon nanoparticles have recently entered Phase I clinical study, this review provides a timely focus on the development of this platform technology and its application for angiogenesis-related pathologies.

Mechanisms of nucleotide trafficking during siRNA delivery to endothelial cells using perfluorocarbon nanoemulsions

RNA interference (RNAi) is a useful in vitro research tool, but its application as a safe and effective therapeutic agent may benefit from improved understanding of mechanisms of exogenous siRNA delivery, including cell trafficking and sorting patterns. We report the development of a transfection reagent for siRNA delivery which employs a distinctive non-digestive mode of particle-cell membrane interaction through the formation of a hemifusion complex resulting in lipid raft transport of cargo to the cytosol, bypassing the usual endosomal nanoparticle uptake pathway. We further demonstrate markedly enhanced efficacy over conventional transfection agents for suppressing endothelial cell expression of upregulated vascular adhesion molecules.

Nanomedicine strategies for molecular targets with MRI and optical imaging

The science of 'theranostics' plays a crucial role in personalized medicine, which represents the future of patient management. Over the last decade an increasing research effort has focused on the development of nanoparticle-based molecular-imaging and drug-delivery approaches, emerging as a multidisciplinary field that shows promise in understanding the components, processes, dynamics and therapies of a disease at a molecular level. The potential of nanometer-sized agents for early detection, diagnosis and personalized treatment of diseases is extraordinary. They have found applications in almost all clinically relevant biomedical imaging modality. In this review, a number of these approaches will be presented with a particular emphasis on MRI and optical imaging-based techniques. We have discussed both established molecular-imaging approaches and recently developed innovative strategies, highlighting the seminal studies and a number of successful examples of theranostic nanomedicine, especially in the areas of cardiovascular and cancer therapy.

Mammalian target of rapamycin (mTOR) induces proliferation and de-differentiation responses to three coordinate pathophysiologic stimuli (mechanical strain, hypoxia, and extracellular matrix remodeling) in rat bladder smooth muscle

Maladaptive bladder muscle overgrowth and de-differentiation in human bladder obstructive conditions is instigated by coordinate responses to three stimuli: mechanical strain, tissue hypoxia, and extracellular matrix remodeling.( 1,2) Pathway analysis of genes induced by obstructive models of injury in bladder smooth muscle cells (BSMCs) identified a mammalian target of rapamycin (mTOR)-specific inhibitor as a potential pharmacological inhibitor. Strain-induced mTOR-specific S6K activation segregated differently from ERK1/2 activation in intact bladder ex vivo. Though rapamycin's antiproliferative effects in vascular smooth muscle cells are well known, its effects on BSMCs were previously unknown. Rapamycin significantly inhibited proliferation of BSMCs in response to mechanical strain, hypoxia, and denatured collagen. Rapamycin inhibited S6K at mTOR-sensitive phosphorylation sites in response to strain and hypoxia. Rapamycin also supported smooth muscle actin expression in response to strain or hypoxia-induced de-differentiation. Importantly, strain plus hypoxia synergistically augmented mTOR-dependent S6K activation, Mmp7 expression and proliferation. Forced expression of wild-type and constitutively active S6K resulted in loss of smooth muscle actin expression. Decreased smooth muscle actin, increased Mmp7 levels and mTOR pathway activation during in vivo partial bladder obstruction paralleled our in vitro studies. These results point to a coordinate role for mTOR in BSMCs responses to the three stimuli and a potential new therapeutic target for myopathic bladder disease.

Nitric oxide-loaded echogenic liposomes for nitric oxide delivery and inhibition of intimal hyperplasia

OBJECTIVES

We sought to develop a new bioactive gas-delivery method by the use of echogenic liposomes (ELIP) as the gas carrier.

BACKGROUND

Nitric oxide (NO) is a bioactive gas with potent therapeutic effects. The bioavailability of NO by systemic delivery is low with potential systemic effects.

METHODS

Liposomes containing phospholipids and cholesterol were prepared by the use of a new method, freezing under pressure. The encapsulation and release profile of NO from NO-containing ELIP (NO-ELIP) or a mixture of NO/argon (NO/Ar-ELIP) was studied. The uptake of NO from NO-ELIP by cultured vascular smooth muscle cells (VSMCs) both in the absence and presence of hemoglobin was determined. The effect of NO-ELIP delivery to attenuate intimal hyperplasia in a balloon-injured artery was determined.

RESULTS

Coencapsulation of NO with Ar enabled us to adjust the amount of encapsulated NO. A total of 10 microl of gas can be encapsulated into 1 mg of liposomes. The release profile of NO from NO-ELIP demonstrated an initial rapid release followed by a slower release during the course of 8 h. Sixty-eight percent of cells remained viable when incubated with 80 microg/ml of NO/Ar-ELIP for 4 h. The delivery agent of NO to VSMCs by the use of NO/Ar-ELIP was 7-fold greater than unencapsulated NO. We discovered that NO/Ar-ELIP remained an effective delivery agent of NO to VSMCs even in the presence of hemoglobin. Local NO-ELIP administration to balloon-injured carotid arteries attenuated the development of intimal hyperplasia and reduced arterial wall thickening by 41 +/- 9%.

CONCLUSIONS

Liposomes can protect and deliver a bioactive gas to target tissues with the potential for both visualization of gas delivery and controlled therapeutic gas release.

Neurosurgery and quantum dots: part I--state of the art

This article represents the first of a 2-part exploration of quantum dots (Qdots) and their application to neurological surgery. Spanning from materials science to immunology, this initial review traces the marriage of imaging physics to biochemical specificity. Qdot science now stands poised to dramatically advance the diagnosis and therapy of neurosurgical conditions. Qdot research efforts currently involve several disciplines; this comprehensive review therefore considers multiple fields of inquiry. This first installment discusses 1) Qdot physical properties, 2) established biological and in vivo properties, 3) magnetic resonance imaging applications, and (4) existing cardiovascular and oncologic research. Finally, this review establishes the existing bounds of Qdot possibilities. The second concept article details future endovascular diagnostic and therapeutic methods derived from these seminal advances.

Local delivery of modified paclitaxel-loaded poly(epsilon-caprolactone)/pluronic F68 nanoparticles for long-term inhibition of hyperplasia

The purpose of this research is to test the possibility of localized intravascular infusion of didodecyldimethylammonium bromide (DMAB)-modified paclitaxel-loaded poly(epsilon-caprolactone)/Pluronic F68 (PCL/F68) nanoparticles to achieve long-term inhibition of hyperplasia in a balloon-injured rabbit carotid artery model. Paclitaxel-loaded nanoparticles were prepared by modified solvent displacement method using commercial poly(lactide-co-glycolide) (PLGA) and self-synthesized PCL/F68, respectively. DMAB was adsorbed on the nanoparticle surface by electrostatic attraction between positive and negative charges to enhance arterial retention. Nanoparticles were found to be of spherical shape with a mean size of around 300 nm and polydispersity of less than 0.150. The surface charge was changed to positive values after the DMAB modification. The in vitro drug release profile of all nanoparticle formulation showed a biphasic release pattern. Drug release from DMAB-modified PCL/F68 nanoparticles (DPNP) was significantly slower than DMAB-modified PLGA nanoparticles (PGNP). After 90 days, DPNP group showed very significant inhibition of neointimal proliferation (p < 0.01), and PGNP group yielded significant inhibition of neointimal proliferation (p < 0.05), when compared with drug-free nanoparticles group. In conclusion, local delivery of paclitaxel-loaded DMAB-modified PCL/F68 nanoparticles was proven an effective means of long-term inhibition of hyperplasia in the rabbits.

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.

Inhibition of Apoptosis Through Localized Delivery of Rapamycin-Loaded Nanoparticles Prevented Neointimal Hyperplasia and Reendothelialized Injured Artery

Background— A significant fraction of vascular smooth muscle cells (VSMCs) undergo rapid apoptosis after balloon angioplasty. In this study, we tested the hypothesis that protecting VSMCs from undergoing apoptosis prevents the cascade of events that lead to intimal hyperplasia.

Methods and Results— Rapamycin-loaded gel-like nanoparticles (mean diameter, 54�5 nm) were infused locally in a rat carotid artery model of vascular injury. The drug has both antiapoptotic and antiproliferative effects on VSMCs and hence was selected for the current study. Localized delivery of nanoparticles sustained the drug level in the target artery for >2 weeks; demonstrated significant inhibition of hyperplasia (intima/media ratio, 1.5�0.02 versus 2.7�0.6; P <0.01); and most importantly, reendothelialized the injured artery (endothelium coverage: treated 82% versus control 28%). We also demonstrated inhibition of activation of caspase-3/7 enzymes in the treated artery, preventing VSMCs from undergoing apoptosis and subsequent infiltration of macrophages.

Conclusions— It may be postulated that the localized delivery of rapamycin inhibited apoptosis of VSMCs, minimizing the inflammatory response to the injury and, thus, creating conditions conducive to vascular repair (reendothelialization). Unlike stenting, which can lead to thrombosis and increased risk for in-stent restenosis, our approach could eliminate or minimize long-term complications because the injured artery undergoes a natural process of reendothelialization.