Combined targeting of lentiviral vectors and positioning of transduced cells by magnetic nanoparticles

Nanotechnology: The Future for Diagnostic and Therapeutic Intervention in Cardiovascular Diseases is Here

With advances in technology and medicine over the last 3 decades, cardiovascular medicine has evolved tremendously. Nanotechnology provides a promising future in personalized precision medicine. In this review, we delve into the current and prospective applications of nanotechnology and nanoparticles in cardiology. Nanotechnology has allowed for point-of-care testing such as high-sensitivity troponins, as well as more precise cardiac imaging. This review is focused on 3 diseases within cardiology: coronary artery disease, heart failure, and valvular heart disease. The use of nanoparticles in coronary stents has shown success in preventing in-stent thrombosis, as well as using nanosized drug delivery medications to prevent neointimal proliferation in a way that spares systemic toxicity. In addition, by using nanoparticles as drug delivery systems, nanotechnology can be utilized in the delivery of goal-directed medical therapy in heart failure patients. It has also been shown to improve cell therapy in this patient population by helping in cell retention of grafts. Finally, the use of nanoparticles in the manufacturing of bioprosthetic valves provides a promising future for the longevity and success of cardiac valve repair and replacement.

Nonmyocytes as electrophysiological contributors to cardiac excitation and conduction

Although cardiac action potential (AP) generation and propagation have traditionally been attributed exclusively to cardiomyocytes (CM), other cell types in the heart are also capable of forming electrically conducting junctions. Interactions between CM and nonmyocytes (NM) enable and modulate each other's activity. This review provides an overview of the current understanding of heterocellular electrical communication in the heart. Although cardiac fibroblasts were initially thought to be electrical insulators, recent studies have demonstrated that they form functional electrical connections with CM in situ. Other NM, such as macrophages, have also been recognized as contributing to cardiac electrophysiology and arrhythmogenesis. Novel experimental tools have enabled the investigation of cell-specific activity patterns in native cardiac tissue, which is expected to yield exciting new insights into the development of novel or improved diagnostic and therapeutic strategies.

Combined use of magnetic microbeads for endothelial cell isolation and enhanced cell engraftment in myocardial repair

Background: The regenerative potential of the heart after injury is limited. Therefore, cell replacement strategies have been developed. However, the engraftment of transplanted cells in the myocardium is very inefficient. In addition, the use of heterogeneous cell populations precludes the reproducibility of the outcome. Methods: To address both issues, in this proof of principle study, we applied magnetic microbeads for combined isolation of eGFP⁺ embryonic cardiac endothelial cells (CECs) by antigen-specific magnet-associated cell sorting (MACS) and improved engraftment of these cells in myocardial infarction by magnetic fields. Results: MACS provided CECs of high purity decorated with magnetic microbeads. In vitro experiments revealed that the angiogenic potential of microbead-labeled CECs was preserved and the magnetic moment of the cells was strong enough for site-specific positioning by a magnetic field. After myocardial infarction in mice, intramyocardial CEC injection in the presence of a magnet resulted in a strong improvement of cell engraftment and eGFP⁺ vascular network formation in the hearts. Hemodynamic and morphometric analysis demonstrated augmented heart function and reduced infarct size only when a magnetic field was applied. Conclusion: Thus, the combined use of magnetic microbeads for cell isolation and enhanced cell engraftment in the presence of a magnetic field is a powerful approach to improve cell transplantation strategies in the heart.

Extracellular Vesicles as Drivers of Immunoinflammation in Atherothrombosis

Atherosclerotic cardiovascular disease is the leading cause of morbidity and mortality all over the world. Extracellular vesicles (EVs), small lipid-bilayer membrane vesicles released by most cellular types, exert pivotal and multifaceted roles in physiology and disease. Emerging evidence emphasizes the importance of EVs in intercellular communication processes with key effects on cell survival, endothelial homeostasis, inflammation, neoangiogenesis, and thrombosis. This review focuses on EVs as effective signaling molecules able to both derail vascular homeostasis and induce vascular dysfunction, inflammation, plaque progression, and thrombus formation as well as drive anti-inflammation, vascular repair, and atheroprotection. We provide a comprehensive and updated summary of the role of EVs in the development or regression of atherosclerotic lesions, highlighting the link between thrombosis and inflammation. Importantly, we also critically describe their potential clinical use as disease biomarkers or therapeutic agents in atherothrombosis.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

Targeted delivery of pharmaceuticals is promising for efficient disease treatment and reduction in adverse effects. Nano or microstructured magnetic materials with strong magnetic momentum can be noninvasively controlled via magnetic forces within living beings. These magnetic carriers open perspectives in controlling the delivery of different types of bioagents in humans, including small molecules, nucleic acids, and cells. In the present review, we describe different types of magnetic carriers that can serve as drug delivery platforms, and we show different ways to apply them to magnetic targeted delivery of bioagents. We discuss the magnetic guidance of nano/microsystems or labeled cells upon injection into the systemic circulation or in the tissue; we then highlight emergent applications in tissue engineering, and finally, we show how magnetic targeting can integrate with imaging technologies that serve to assist drug delivery.

Application of magnetic nanoparticles in cell therapy

Fe₃O₄ magnetic nanoparticles (MNPs) are biomedical materials that have been approved by the FDA. To date, MNPs have been developed rapidly in nanomedicine and are of great significance. Stem cells and secretory vesicles can be used for tissue regeneration and repair. In cell therapy, MNPs which interact with external magnetic field are introduced to achieve the purpose of cell directional enrichment, while MRI to monitor cell distribution and drug delivery. This paper reviews the size optimization, response in external magnetic field and biomedical application of MNPs in cell therapy and provides a comprehensive view.

Cx43 Promotes Endothelial Cell Migration and Angiogenesis via the Tyrosine Phosphatase SHP-2

The gap junction protein connexin 43 (Cx43) is associated with increased cell migration and to related changes of the actin cytoskeleton, which is mediated via its C-terminal cytoplasmic tail and is independent of its channel function. Cx43 has been shown to possess an angiogenic potential, however, the role of Cx43 in endothelial cell migration has not yet been investigated. Here, we found that the knock-down of Cx43 by siRNA in human microvascular endothelial cells (HMEC) reduces migration, as assessed by a wound assay in vitro and impaired aortic vessel sprouting ex vivo. Immunoprecipitation of Cx43 revealed an interaction with the tyrosine phosphatase SHP-2, which enhanced its phosphatase activity, as observed in Cx43 expressing HeLa cells compared to cells treated with an empty vector. Interestingly, the expression of a dominant negative substrate trapping mutant SHP-2 (CS) in HMEC, via lentiviral transduction, also impaired endothelial migration to a similar extent as Cx43 siRNA compared to SHP-2 WT. Moreover, the reduction in endothelial migration upon Cx43 siRNA could not be rescued by the introduction of a constitutively active SHP-2 construct (EA). Our data demonstrate that Cx43 and SHP-2 mediate endothelial cell migration, revealing a novel interaction between Cx43 and SHP-2, which is essential for this process.

Role of miR-24 in Multiple Endocrine Neoplasia Type 1: A Potential Target for Molecular Therapy

Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant inherited multiple cancer syndrome of neuroendocrine tissues. Tumors are caused by an inherited germinal heterozygote inactivating mutation of the MEN1 tumor suppressor gene, followed by a somatic loss of heterozygosity (LOH) of the MEN1 gene in target neuroendocrine cells, mainly at parathyroids, pancreas islets, and anterior pituitary. Over 1500 different germline and somatic mutations of the MEN1 gene have been identified, but the syndrome is completely missing a direct genotype-phenotype correlation, thus supporting the hypothesis that exogenous and endogenous factors, other than MEN1 specific mutation, are involved in MEN1 tumorigenesis and definition of individual clinical phenotype. Epigenetic factors, such as microRNAs (miRNAs), are strongly suspected to have a role in MEN1 tumor initiation and development. Recently, a direct autoregulatory network between miR-24, MEN1 mRNA, and menin was demonstrated in parathyroids and endocrine pancreas, showing a miR-24-induced silencing of menin expression that could have a key role in initiation of tumors in MEN1-target neuroendocrine cells. Here, we review the current knowledge on the post-transcriptional regulation of MEN1 and menin expression by miR-24, and its possible direct role in MEN1 syndrome, describing the possibility and the potential approaches to target and silence this miRNA, to permit the correct expression of the wild type menin, and thereby prevent the development of cancers in the target tissues.

Magnetic nanocomplexes for gene delivery applications

Gene delivery is an indispensable technique for various biomedical applications such as gene therapy, stem cell engineering and gene editing. Recently, magnetic nanoparticles (MNPs) have received increasing attention for their use in promoting gene delivery efficiency. Under magnetic attraction, gene delivery efficiency using viral or nonviral gene carriers could be universally enhanced. Besides, magnetic nanoparticles could be utilized in magnetic resonance imaging or magnetic hyperthermia therapy, providing extra theranostic opportunities. In this review, recent research integrating MNPs with a viral or nonviral gene vector is summarized from both technical and application perspectives. Applications of MNPs in cutting-edge research technologies, such as biomimetic cell membrane nano-gene carriers, exosome-based gene delivery, cell-based drug delivery systems or CRISPR/Cas9 gene editing, are also discussed.

Magnetic Iron Oxide Nanoparticles for Disease Detection and Therapy

Magnetic iron oxide nanoparticles (MIONs) are among the first generation of nanomaterials that have advanced to clinic use. A broad range of biomedical techniques has been developed by combining the versatile nanomagnetism of MIONs with various forms of applied magnetic fields. MIONs can generate imaging contrast and provide mechanical/thermal energy in vivo in response to an external magnetic field, a special feature that distinguishes MIONs from other nanomaterials. These properties offer unique opportunities for nanomaterials engineering in biomedical research and clinical interventions. The past few decades have witnessed the evolution of the applications of MIONs from conventional drug delivery and hyperthermia to the regulation of molecular and cellular processes in the body. Here we review the most recent development in this field, including clinical studies of MIONs and the emerging techniques that may contribute to future innovation in medicine.

Nanoscale Technologies for Prevention and Treatment of Heart Failure: Challenges and Opportunities

The adult myocardium has a limited regenerative capacity following heart injury, and the lost cells are primarily replaced by fibrotic scar tissue. Suboptimal efficiency of current clinical therapies to resurrect the infarcted heart results in injured heart enlargement and remodeling to maintain its physiological functions. These remodeling processes ultimately leads to ischemic cardiomyopathy and heart failure (HF). Recent therapeutic approaches (e.g., regenerative and nanomedicine) have shown promise to prevent HF postmyocardial infarction in animal models. However, these preclinical, clinical, and technological advancements have yet to yield substantial enhancements in the survival rate and quality of life of patients with severe ischemic injuries. This could be attributed largely to the considerable gap in knowledge between clinicians and nanobioengineers. Development of highly effective cardiac regenerative therapies requires connecting and coordinating multiple fields, including cardiology, cellular and molecular biology, biochemistry and chemistry, and mechanical and materials sciences, among others. This review is particularly intended to bridge the knowledge gap between cardiologists and regenerative nanomedicine experts. Establishing this multidisciplinary knowledge base may help pave the way for developing novel, safer, and more effective approaches that will enable the medical community to reduce morbidity and mortality in HF patients.

The Phosphatase SHP-2 Activates HIF-1α in Wounds In Vivo by Inhibition of 26S Proteasome Activity

Vascular remodeling and angiogenesis are required to improve the perfusion of ischemic tissues. The hypoxic environment, induced by ischemia, is a potent stimulus for hypoxia inducible factor 1α (HIF-1α) upregulation and activation, which induce pro-angiogenic gene expression. We previously showed that the tyrosine phosphatase SHP-2 drives hypoxia mediated HIF-1α upregulation via inhibition of the proteasomal pathway, resulting in revascularization of wounds in vivo. However, it is still unknown if SHP-2 mediates HIF-1α upregulation by affecting 26S proteasome activity and how the proteasome is regulated upon hypoxia. Using a reporter construct containing the oxygen-dependent degradation (ODD) domain of HIF-1α and a fluorogenic proteasome substrate in combination with SHP-2 mutant constructs, we show that SHP-2 inhibits the 26S proteasome activity in endothelial cells under hypoxic conditions in vitro via Src kinase/p38 mitogen-activated protein kinase (MAPK) signalling. Moreover, the simultaneous expression of constitutively active SHP-2 (E76A) and inactive SHP-2 (CS) in separate hypoxic wounds in the mice dorsal skin fold chamber by localized magnetic nanoparticle-assisted lentiviral transduction showed specific regulation of proteasome activity in vivo. Thus, we identified a new additional mechanism of SHP-2 mediated HIF-1α upregulation and proteasome activity, being functionally important for revascularization of wounds in vivo. SHP-2 may therefore constitute a potential novel therapeutic target for the induction of angiogenesis in ischemic vascular disease.

Biopolymers augment viral vectors based gene delivery

The success of viral vectors mediated gene therapy is still hampered by immunogenicity and insufficient transgene expression. Alternatively, non-viral vectors mediated gene delivery has the advantage of low immunogenicity despite showing low transgene expression. By carefully considering the advantages of each approach, hybrid vectors are currently being developed by modifying the viral vectors using non-viral biopolymers. This review provides an overview of the hybrid vectors currently being developed.

Local anti-angiogenic therapy by magnet-assisted downregulation of SHP2 phosphatase

Anti-angiogenic therapies are promising options for diseases with enhanced vessel formation such as tumors or retinopathies. In most cases, a site-specific local effect on vessel growth is required, while the current focus on systemic distribution of angiogenesis inhibitors may cause severe unwanted side-effects. Therefore, in the current study we have developed an approach for the local inhibition of vascularization, using complexes of lentivirus and magnetic nanoparticles in combination with magnetic fields. Using this strategy in the murine embryonic stem cell (ESC) system, we were able to site-specifically downregulate the protein tyrosine phosphatase SHP2 by RNAi technology in areas with active vessel formation. This resulted in a reduction of vessel development, as shown by reduced vascular tube length, branching points and vascular loops. The anti-angiogenic effect could also be recapitulated in the dorsal skinfold chamber of mice in vivo. Here, site-specific downregulation of SHP2 reduced re-vascularization after wound induction. Thus, we have developed a magnet-assisted, RNAi-based strategy for the efficient local inhibition of angiogenesis in ESCs in vitro and also in vivo.

Inactivation of the tyrosine phosphatase SHP-2 drives vascular dysfunction in Sepsis

Background

Sepsis, the most severe form of infection, involves endothelial dysfunction which contributes to organ failure. To improve therapeutic prospects, elucidation of molecular mechanisms underlying endothelial vascular failure is of essence.

Methods

Polymicrobial contamination induced sepsis mouse model and primary endothelial cells incubated with sepsis serum were used to study SHP-2 in sepsis-induced endothelial inflammation. SHP-2 activity was assessed by dephosphorylation of pNPP, ROS production was measured by DCF oxidation and protein interactions were assessed by proximity ligation assay. Vascular inflammation was studied in the mouse cremaster model and in an in vitro flow assay.

Findings

We identified ROS-dependent inactivation of the tyrosine phosphatase SHP-2 to be decisive for endothelial activation in sepsis. Using in vivo and in vitro sepsis models, we observed a significant reduction of endothelial SHP-2 activity, accompanied by enhanced adhesion molecule expression. The impaired SHP-2 activity was restored by ROS inhibitors and an IL-1 receptor antagonist. SHP-2 activity inversely correlated with the adhesive phenotype of endothelial cells exposed to IL-1β as well as sepsis serum via p38 MAPK and NF-κB. In vivo, SHP-2 inhibition accelerated IL-1β-induced leukocyte adhesion, extravasation and vascular permeability. Mechanistically, SHP-2 directly interacts with the IL-1R1 adaptor protein MyD88 via its tyrosine 257, resulting in reduced binding of p85/PI3-K to MyD88.

Interpretation

Our data show that SHP-2 inactivation by ROS in sepsis releases a protective break, resulting in endothelial activation.

Fund

German Research Foundation, LMU Mentoring excellence and FöFoLe Programme, Verein zur Förderung von Wissenschaft und Forschung, German Ministry of Education and Research.

Overexpression of Cx43 in cells of the myocardial scar: Correction of post-infarct arrhythmias through heterotypic cell-cell coupling

Ventricular tachycardia (VT) is the most common and potentially lethal complication following myocardial infarction (MI). Biological correction of the conduction inhomogeneity that underlies re-entry could be a major advance in infarction therapy. As minimal increases in conduction of infarcted tissue markedly influence VT susceptibility, we reasoned that enhanced propagation of the electrical signal between non-excitable cells within a resolving infarct might comprise a simple means to decrease post-infarction arrhythmia risk. We therefore tested lentivirus-mediated delivery of the gap-junction protein Connexin 43 (Cx43) into acute myocardial lesions. Cx43 was expressed in (myo)fibroblasts and CD45⁺ cells within the scar and provided prominent and long lasting arrhythmia protection in vivo. Optical mapping of Cx43 injected hearts revealed enhanced conduction velocity within the scar, indicating Cx43-mediated electrical coupling between myocytes and (myo)fibroblasts. Thus, Cx43 gene therapy, by direct in vivo transduction of non-cardiomyocytes, comprises a simple and clinically applicable biological therapy that markedly reduces post-infarction VT.

Synchronization of excitable cardiac cultures of different origin

In the present work, we investigated the synchronization of electrical activity in cultured cardiac cells of different origin put in direct contact. In the first set of experiments synchronization was studied in the primary culture cells of neonatal rats taken at different developmental ages, and in the second - in the neonatal rat cardiomyocytes and HL-1 cells. The electrical excitation of cells was recorded using the calcium transient marker Fluor-4. In the confluent cell layers created with the aid of a specially devised mask, the excitation waves and their propagation between areas occupied by cells of different origin were observed. On the level of individual cells, their contact and synchronization was monitored with the aid of scanning fluorescence microscopy. It was found that populations of cultured cells of different origin are able to synchronize, suggesting the formation of electrical coupling between them. The results obtained may be considered as a proof of concept that implanted alien grafted cells are able to create electrical coupling with the host cardiac tissue.

Endothelial- and Immune Cell-Derived Extracellular Vesicles in the Regulation of Cardiovascular Health and Disease

Intercellular signaling by extracellular vesicles (EVs) is a route of cell-cell crosstalk that allows cells to deliver biological messages to specific recipient cells. EVs convey these messages through their distinct cargoes consisting of cytokines, proteins, nucleic acids, and lipids, which they transport from the donor cell to the recipient cell. In cardiovascular disease (CVD), endothelial- and immune cell-derived EVs are emerging as key players in different stages of disease development. EVs can contribute to atherosclerosis development and progression by promoting endothelial dysfunction, intravascular calcification, unstable plaque progression, and thrombus formation after rupture. In contrast, an increasing body of evidence highlights the beneficial effects of certain EVs on vascular function and endothelial regeneration. However, the effects of EVs in CVD are extremely complex and depend on the cellular origin, the functional state of the releasing cells, the biological content, and the diverse recipient cells. This paper summarizes recent progress in our understanding of EV signaling in cardiovascular health and disease and its emerging potential as a therapeutic agent.

Tumor targeting by lentiviral vectors combined with magnetic nanoparticles in mice

Nanomaterials conjugated or complexed with biological moieties such as antibodies, polymers or peptides appear to be suitable not only for drug delivery but also for specific cancer treatment. Here, biocompatible iron oxide magnetic nanoparticles (MNPs) with or without a silica shell coupled with lentiviral vectors (LVs) are proposed as a combined therapeutic approach to specifically target gene expression in a cancer mouse model. Initially, four different MNPs were synthesized and their physical properties were characterized to establish and discriminate their behaviors. MNPs and LVs strictly interacted and transduced cells in vitro as well as in vivo, with no toxicity or inflammatory responses. By injecting LV-MNPs complexes intravenously, green fluorescent protein (GFP) resulted in a sustained long-term expression. Furthermore, by applying a magnetic field on the abdomen of intravenous injected mice, GFP positive cells increased in livers and spleens. In liver, LV-MNPs were able to target both hepatocytes and non-parenchymal cells, while in a mouse model with a grafted tumor, intra-tumor LV-MNPs injection and magnetic plaque application next to the tumor demonstrated the efficient uptake of LV-MNPs complexes with high number of transduced cells and iron accumulation in the tumor site. More important, LV-MNPs with the application of the magnetic plaque spread in all the tumor parenchyma and dissemination through the body was prevented confirming the efficient uptake of LV-MNPs complexes in the tumor. Thus, these LV-MNPs complexes could be used as multifunctional and efficient tools to selectively induce transgene expression in solid tumor for therapeutic purposes.

STATEMENT OF SIGNIFICANCE

Our study describes a novel approach of combining magnetic properties of nanomaterials with gene therapy. Magnetic nanoparticles (MNPs) coated with or without a silica shell coupled with lentiviral vectors (LVs) were used as vehicle to target biological active molecules in a mouse cancer model. After in situ injection, the presence of MNP under the magnetic field improve the vector distribution in the tumor mass and after systemic administration, the application of the magnetic field favor targeting of specific organs for LV transduction and specifically can direct LV in specific cells (or avoiding them). Thus, our findings suggest that LV-MNPs complexes could be used as multifunctional and efficient tools to selectively induce transgene expression in solid tumor for therapeutic purposes.

Optimizing endothelial cell functionalization for cell therapy of vascular proliferative disease using a direct contact co-culture system

Increased susceptibility to thrombosis, neoatherosclerosis, and restenosis due to incomplete regrowth of the protective endothelial layer remains a critical limitation of the interventional strategies currently used clinically to relieve atherosclerotic obstruction. Rapid recovery of endothelium holds promise for both preventing the thrombotic events and reducing post-angioplasty restenosis, providing the rationale for developing cell delivery strategies for accelerating arterial reendothelialization. The successful translation of experimental cell therapies into clinically viable treatment modalities for restoring vascular endothelium critically depends on identifying strategies for enhancing the functionality of endothelial cells (EC) derived from high cardiovascular risk patients, the target group for the majority of angioplasty procedures. Enhancing EC-associated nitric oxide (NO) synthesis by inducing overexpression of NO synthase (NOS) has shown promise as a way of increasing paracrine activity and restoring function of EC. In the present study, we developed a direct contact co-culture approach compatible with highly labile effectors, such as NO, and applied it for determining the effect of EC functionalization via NOS gene transfer on the growth of co-cultured arterial smooth muscle cells (A10 cell line) exhibiting the defining characteristics of neointimal cells. Bovine aortic endothelial cells magnetically transduced with inducible NOS-encoding adenovirus (Ad) formulated in zinc oleate-based magnetic nanoparticles (MNP[_iNOSAd]) strongly suppressed growth of proliferating A10 and attenuated the stimulatory effect of a potent mitogen, platelet-derived growth factor (PDGF-BB), whereas EC functionalization with free _iNOSAd or MNP formulated with a different isoform of the enzyme, endothelial NOS, was associated with lower levels of NO synthesis and less pronounced antiproliferative activity toward co-cultured A10 cells. These results show feasibility of applying magnetically facilitated gene transfer to potentiate therapeutically relevant effects of EC for targeted cell therapy of restenosis. The direct contact co-culture methodology provides a sensitive and reliable tool with potential utility for a variety of biomedical applications.

HIF-1α Dependent Wound Healing Angiogenesis In Vivo Can Be Controlled by Site-Specific Lentiviral Magnetic Targeting of SHP-2

Hypoxia promotes vascularization by stabilization and activation of the hypoxia inducible factor 1α (HIF-1α), which constitutes a target for angiogenic gene therapy. However, gene therapy is hampered by low gene delivery efficiency and non-specific side effects. Here, we developed a gene transfer technique based on magnetic targeting of magnetic nanoparticle-lentivirus (MNP-LV) complexes allowing site-directed gene delivery to individual wounds in the dorsal skin of mice. Using this technique, we were able to control HIF-1α dependent wound healing angiogenesis in vivo via site-specific modulation of the tyrosine phosphatase activity of SHP-2. We thus uncover a novel physiological role of SHP-2 in protecting HIF-1α from proteasomal degradation via a Src kinase dependent mechanism, resulting in HIF-1α DNA-binding and transcriptional activity in vitro and in vivo. Excitingly, using targeting of MNP-LV complexes, we achieved simultaneous expression of constitutively active as well as inactive SHP-2 mutant proteins in separate wounds in vivo and hereby specifically and locally controlled HIF-1α activity as well as the angiogenic wound healing response in vivo. Therefore, magnetically targeted lentiviral induced modulation of SHP-2 activity may be an attractive approach for controlling patho-physiological conditions relying on hypoxic vessel growth at specific sites.

Targeting of Magnetic Nanoparticle-coated Microbubbles to the Vascular Wall Empowers Site-specific Lentiviral Gene Delivery in vivo

In the field of vascular gene therapy, targeting systems are promising advancements to improve site-specificity of gene delivery. Here, we studied whether incorporation of magnetic nanoparticles (MNP) with different magnetic properties into ultrasound sensitive microbubbles may represent an efficient way to enable gene targeting in the vascular system after systemic application. Thus, we associated novel silicon oxide-coated magnetic nanoparticle containing microbubbles (SO-Mag MMB) with lentiviral particles carrying therapeutic genes and determined their physico-chemical as well as biological properties compared to MMB coated with polyethylenimine-coated magnetic nanoparticles (PEI-Mag MMB). While there were no differences between both MMB types concerning size and lentivirus binding, SO-Mag MMB exhibited superior characteristics regarding magnetic moment, magnetizability as well as transduction efficiency under static and flow conditions in vitro. Focal disruption of lentiviral SO-Mag MMB by ultrasound within isolated vessels exposed to an external magnetic field decisively improved localized VEGF expression in aortic endothelium ex vivo and enhanced the angiogenic response. Using the same system in vivo, we achieved a highly effective, site-specific lentiviral transgene expression in microvessels of the mouse dorsal skin after arterial injection. Thus, we established a novel lentiviral MMB technique, which has great potential towards site-directed vascular gene therapy.

Magnetofection Enhances Lentiviral-Mediated Transduction of Airway Epithelial Cells through Extracellular and Cellular Barriers

Gene transfer to airway epithelial cells is hampered by extracellular (mainly mucus) and cellular (tight junctions) barriers. Magnetofection has been used to increase retention time of lentiviral vectors (LV) on the cellular surface. In this study, magnetofection was investigated in airway epithelial cell models mimicking extracellular and cellular barriers. Bronchiolar epithelial cells (H441 line) were evaluated for LV-mediated transduction after polarization onto filters and dexamethasone (dex) treatment, which induced hemicyst formation, with or without magnetofection. Sputum from cystic fibrosis (CF) patients was overlaid onto cells, and LV-mediated transduction was evaluated in the absence or presence of magnetofection. Magnetofection of unpolarized H441 cells increased the transduction with 50 MOI (multiplicity of infection, i.e., transducing units/cell) up to the transduction obtained with 500 MOI in the absence of magnetofection. Magnetofection well-enhanced LV-mediated transduction in mucus-layered cells by 20.3-fold. LV-mediated transduction efficiency decreased in dex-induced hemicysts in a time-dependent fashion. In dome-forming cells, zonula occludens-1 (ZO-1) localization at the cell borders was increased by dex treatment. Under these experimental conditions, magnetofection significantly increased LV transduction by 5.3-fold. In conclusion, these results show that magnetofection can enhance LV-mediated gene transfer into airway epithelial cells in the presence of extracellular (sputum) and cellular (tight junctions) barriers, representing CF-like conditions.

Improvement of vascular function by magnetic nanoparticle-assisted circumferential gene transfer into the native endothelium

Gene therapy is a promising approach for chronic disorders that require continuous treatment such as cardiovascular disease. Overexpression of vasoprotective genes has generated encouraging results in animal models, but not in clinical trials. One major problem in humans is the delivery of sufficient amounts of genetic vectors to the endothelium which is impeded by blood flow, whereas prolonged stop-flow conditions impose the risk of ischemia. In the current study we have therefore developed a strategy for the efficient circumferential lentiviral gene transfer in the native endothelium under constant flow conditions. For that purpose we perfused vessels that were exposed to specially designed magnetic fields with complexes of lentivirus and magnetic nanoparticles thereby enabling overexpression of therapeutic genes such as endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF). This treatment enhanced NO and VEGF production in the transduced endothelium and resulted in a reduction of vascular tone and increased angiogenesis. Thus, the combination of MNPs with magnetic fields is an innovative strategy for site-specific and efficient vascular gene therapy.

Homogeneous Biosensing Based on Magnetic Particle Labels

The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation.

Vascular Repair by Circumferential Cell Therapy Using Magnetic Nanoparticles and Tailored Magnets

Cardiovascular disease is often caused by endothelial cell (EC) dysfunction and atherosclerotic plaque formation at predilection sites. Also surgical procedures of plaque removal cause irreversible damage to the EC layer, inducing impairment of vascular function and restenosis. In the current study we have examined a potentially curative approach by radially symmetric re-endothelialization of vessels after their mechanical denudation. For this purpose a combination of nanotechnology with gene and cell therapy was applied to site-specifically re-endothelialize and restore vascular function. We have used complexes of lentiviral vectors and magnetic nanoparticles (MNPs) to overexpress the vasoprotective gene endothelial nitric oxide synthase (eNOS) in ECs. The MNP-loaded and eNOS-overexpressing cells were magnetic, and by magnetic fields they could be positioned at the vascular wall in a radially symmetric fashion even under flow conditions. We demonstrate that the treated vessels displayed enhanced eNOS expression and activity. Moreover, isometric force measurements revealed that EC replacement with eNOS-overexpressing cells restored endothelial function after vascular injury in eNOS(-/-) mice ex and in vivo. Thus, the combination of MNP-based gene and cell therapy with custom-made magnetic fields enables circumferential re-endothelialization of vessels and improvement of vascular function.

Advanced cell therapies: targeting, tracking and actuation of cells with magnetic particles

Regenerative medicine would greatly benefit from a new platform technology that enabled measurable, controllable and targeting of stem cells to a site of disease or injury in the body. Superparamagnetic iron-oxide nanoparticles offer attractive possibilities in biomedicine and can be incorporated into cells, affording a safe and reliable means of tagging. This review describes three current and emerging methods to enhance regenerative medicine using magnetic particles to guide therapeutic cells to a target organ; track the cells using MRI and assess their spatial localization with high precision and influence the behavior of the cell using magnetic actuation. This approach is complementary to the systemic injection of cell therapies, thus expanding the horizon of stem cell therapeutics.

Cell Penetrating Peptide Adsorption on Magnetite and Silica Surfaces: A Computational Investigation

Magnetic nanoparticles (MNPs) represent one of the most promising materials as they can act as a versatile platform in the field of bionanotechnology for enhanced imaging, diagnosis, and treatment of various diseases. Silica is the most common compound for preparing coated iron oxide NPs since it improves colloidal stability and the binding affinity for various organic molecules. Biomolecules such as cell penetrating peptides (CPPs) might be employed to decorate MNPs, combining their promising physicochemical properties with a cell penetrating ability. In this work, a computational investigation on adsorption of Antennapedia homeodomain-derived penetrating peptide (pAntp) on silica and magnetite (MAG) surfaces is presented. By employing umbrella sampling molecular dynamics, we provided a quantitative estimation of the pAntp-surface adsorption free energy to highlight the influence of surface hydroxylation state on the adsorption mechanism. The interaction between peptide and surface has shown to be mainly driven by electrostatics. In case of MAG surface, also an important contribution of van der Waals (VdW) attraction was observed. Our data suggest that a competitive mechanism between MNPs and cell membrane might partially inhibit the CPP to carry out its membrane penetrating function.

Characterization of magnetic viral complexes for targeted delivery in oncology

Oncolytic viruses are promising new agents in cancer therapy. Success of tumor lysis is often hampered by low intra-tumoral titers due to a strong anti-viral host immune response and insufficient tumor targeting. Previous work on the co-assembly of oncolytic virus particles (VPs) with magnetic nanoparticles (MNPs) was shown to provide shielding from inactivating immune response and improve targeting by external field gradients. In addition, MNPs are detected by magnet resonance imaging (MRI) enabling non-invasive therapy monitoring.

In this study two selected core-shell type iron oxide MNPs were assembled with adenovirus (Ad) or vesicular stomatitis virus (VSV). The selected MNPs were characterized by high r₂ and r₂^* relaxivities and thus could be quantified non-invasively by 1.5 and 3.0 tesla MRI with a detection limit below 0.001 mM iron in tissue-mimicking phantoms. Assembly and cell internalization of MNP-VP complexes resulted in 81 - 97 % reduction of r₂ and 35 - 82 % increase of r₂^* compared to free MNPs. The relaxivity changes could be attributed to the clusterization of particles and complexes shown by transmission electron microscopy (TEM). In a proof-of-principle study the non-invasive detection of MNP-VPs by MRI was shown in vivo in an orthotopic rat hepatocellular carcinoma model.

In conclusion, MNP assembly and compartmentalization have a major impact on relaxivities, therefore calibration measurements are required for the correct quantification in biodistribution studies. Furthermore, our study provides first evidence of the in vivo applicability of selected MNP-VPs in cancer therapy.

Prevention of acute liver allograft rejection by IL-10-engineered mesenchymal stem cells

Hepatic allograft rejection remains a challenging problem, with acute rejection episode as the major barrier for long-term survival in liver transplant recipients. To explore a strategy to prevent allograft rejection, we hypothesized that mesenchymal stem cells (MSCs) genetically engineered with interleukin-10 (IL-10) could produce beneficial effects on orthotopic liver transplantation (OLT) in the experimental rat model. Syngeneic MSCs transduced with IL-10 were delivered via the right jugular vein 30 min post-orthotopic transplantation in the rat model. To evaluate liver morphology and measure cytokine concentration, the blood and liver samples from each animal group were collected at different time-points (3, 5 and 7 days) post-transplantation. The mean survival time of the rats treated with MSCs-IL-10 was shown to be much longer than those treated with saline. According to Banff scheme grading, the saline group scores increased significantly compared with those in the MSCs-IL-10 group. Retinoid acid receptor-related orphan receptor gamma t (RORγt) expression was more increased in the saline group compared to those in the MSCs-IL-10 group in a time-dependent manner; forkhead box protein 3 (FoxP3) expression also decreased significantly in the saline group compared with those in the MSCs-IL-10 group in a time-dependent manner. The expression of cytokines [IL-17, IL-23, IL-6, interferon (IFN)-γ and tumour necrosis factor (TNF)-α] in the saline groups increased significantly compared with the time-point-matched MSCs-IL-10 group, whereas cytokine expression of (IL-10, TGF-β1) was deceased markedly compared to that in the MSCs-IL-10 group. These results suggest a potential role for IL-10-engineered MSC therapy to overcome clinical liver transplantation rejection.

Transduction of murine embryonic stem cells by magnetic nanoparticle-assisted lentiviral gene transfer

Genetic modification of embryonic stem (ES) cells is a valuable technique when combined with cell replacement strategies. Obtaining stable transgene expression and low-cytotoxicity lentiviral transduction of ES cells is advantageous. It has been shown that the efficiency of transfection and transduction approaches can be increased by magnetic nanoparticles (MNPs). Here, we present a protocol for MNP-assisted lentiviral transduction of adherent mouse ES cells. The application of MNPs increased transduction efficiency and provided the opportunity of cell positioning by a magnetic field.

Chemically tunable cationic polymer-bonded magnetic nanoparticles for gene magnetofection

This study evaluates the efficiency of novel non-viral vectors consisting of super paramagnetic iron oxide nanoparticles functionalized with the chemically tunable cationic polymer forin vitrogene magnetofection.

TBK1 mediates critical effects of measles virus nucleocapsid protein (MVNP) on pagetic osteoclast formation

Paget's disease of bone (PDB) is characterized by abnormal osteoclasts with unique characteristics that include increased sensitivity of osteoclast progenitors to 1,25(OH)2 D3 , receptor activator of NF-κB ligand (RANKL), and TNF-α; increased osteoclast numbers; and increased expression of IL-6 and several transcription factors. We recently reported that measles virus nucleocapsid protein (MVNP) plays a key role in the development of these abnormal osteoclasts. MVNP can induce the pagetic osteoclast phenotype in vitro and in vivo in TRAP-MVNP transgenic mice. However, the molecular mechanisms by which MVNP generates pagetic osteoclasts have not been determined. TANK-binding kinase 1 (TBK1) and IκB kinase-ϵ (IKKϵ) are IKK family members that complex with MVNP and activate both IRF3 and NF-κB pathways. MVNP increases the amount of TBK1 protein in bone marrow monocytes (BMM). Interestingly, we found that RANKL increased TBK1 and IKKϵ early in osteoclast differentiation, suggesting a possible role in normal osteoclastogenesis. However, only TBK1 is further increased in osteoclasts formed by TRAP-MVNP BMM owing to increased TBK1 protein stability. TBK1 overexpression induced IL6 promoter reporter activity, and elevated endogenous IL6 mRNA and p65 NF-κB, TAF12, and ATF7 proteins in several cell lines. Overexpression of TBK1 was insufficient to induce pagetic osteoclasts from WT BMM but synergized with MVNP to increase pagetic osteoclast formation from TRAP-MVNP BMM. BX795 inhibition of TBK1 impaired MVNP-induced IL-6 expression in both NIH3T3 cells and BMM, and shRNA knockdown of Tbk1 in NIH3T3 cells impaired IL-6 secretion induced by MVNP and decreased TAF12 and ATF7, factors involved in 1,25(OH)2 D3 hypersensitivity of pagetic osteoclasts. Similarly, Tbk1 knockdown in BMM from TRAP-MVNP and WT mice specifically impaired development of the MVNP-induced osteoclast pagetic phenotype. These results demonstrate that TBK1 plays a critical role in mediating the effects of MVNP on osteoclast differentiation and on the expression of IL-6, a key contributor to the pagetic osteoclast phenotype.

Role of ATF7-TAF12 interactions in the vitamin D response hypersensitivity of osteoclast precursors in Paget's disease

Osteoclast (OCL) precursors from many Paget's disease (PD) patients express measles virus nucleocapsid protein (MVNP) and are hypersensitive to 1,25-dihydroxyvitamin D₂ (1,25-(OH)₂D₃; also know as calcitriol). The increased 1,25-(OH)₂D₃ sensitivity is mediated by transcription initiation factor TFIID subunit 12 (TAF12), a coactivator of the vitamin D receptor (VDR), which is present at much higher levels in MVNP-expressing OCL precursors than normals. These results suggest that TAF12 plays an important role in the abnormal OCL activity in PD. However, the molecular mechanisms underlying both 1,25-(OH)₂D₃'s effects on OCL formation and the contribution of TAF12 to these effects in both normals and PD patients are unclear. Inhibition of TAF12 with a specific TAF12 antisense construct decreased OCL formation and OCL precursors' sensitivity to 1,25-(OH)₂D₃ in PD patient bone marrow samples. Further, OCL precursors from transgenic mice in which TAF12 expression was targeted to the OCL lineage (tartrate-resistant acid phosphatase [TRAP]-TAF12 mice), formed OCLs at very low levels of 1,25-(OH)₂D₃, although the OCLs failed to exhibit other hallmarks of PD OCLs, including receptor activator of NF-κB ligand (RANKL) hypersensitivity and hypermultinucleation. Chromatin immunoprecipitation (ChIP) analysis of OCL precursors using an anti-TAF12 antibody demonstrated that TAF12 binds the 24-hydroxylase (CYP24A1) promoter, which contains two functional vitamin D response elements (VDREs), in the presence of 1,25-(OH)₂D₃. Because TAF12 directly interacts with the cyclic adenosine monophosphate-dependent activating transcription factor 7 (ATF7) and potentiates ATF7-induced transcriptional activation of ATF7-driven genes in other cell types, we determined whether TAF12 is a functional partner of ATF7 in OCL precursors. Immunoprecipitation of lysates from either wild-type (WT) or MVNP-expressing OCL with an anti-TAF12 antibody, followed by blotting with an anti-ATF7 antibody, or vice versa, showed that TAF12 and ATF7 physically interact in OCLs. Knockdown of ATF7 in MVNP-expressing cells decreased cytochrome P450, family 24, subfamily A, polypeptide 1 (CYP24A1) induction by1,25-(OH)₂D₃, as well as TAF12 binding to the CYP24A1 promoter. These results show that ATF7 interacts with TAF12 and contributes to the hypersensitivity of OCL precursors to 1,25-(OH)₂D₃ in PD.

Innovative strategy for microRNA delivery in human mesenchymal stem cells via magnetic nanoparticles

Bone marrow derived human mesenchymal stem cells (hMSCs) show promising potential in regeneration of defective tissue. Recently, gene silencing strategies using microRNAs (miR) emerged with the aim to expand the therapeutic potential of hMSCs. However, researchers are still searching for effective miR delivery methods for clinical applications. Therefore, we aimed to develop a technique to efficiently deliver miR into hMSCs with the help of a magnetic non-viral vector based on cationic polymer polyethylenimine (PEI) bound to iron oxide magnetic nanoparticles (MNP). We tested different magnetic complex compositions and determined uptake efficiency and cytotoxicity by flow cytometry. Additionally, we monitored the release, processing and functionality of delivered miR-335 with confocal laser scanning microscopy, real-time PCR and live cell imaging, respectively. On this basis, we established parameters for construction of magnetic non-viral vectors with optimized uptake efficiency (~75%) and moderate cytotoxicity in hMSCs. Furthermore, we observed a better transfection performance of magnetic complexes compared to PEI complexes 72 h after transfection. We conclude that MNP-mediated transfection provides a long term effect beneficial for successful genetic modification of stem cells. Hence, our findings may become of great importance for future in vivo applications.

Multifunctional nanoparticles for drug delivery and molecular imaging

Recent advances in nanotechnology and growing needs in biomedical applications have driven the development of multifunctional nanoparticles. These nanoparticles, through nanocrystalline synthesis, advanced polymer processing, and coating and functionalization strategies, have the potential to integrate various functionalities, simultaneously providing (a) contrast for different imaging modalities, (b) targeted delivery of drug/gene, and (c) thermal therapies. Although still in its infancy, the field of multifunctional nanoparticles has shown great promise in emerging medical fields such as multimodal imaging, theranostics, and image-guided therapies. In this review, we summarize the techniques used in the synthesis of complex nanostructures, review the major forms of multifunctional nanoparticles that have emerged over the past few years, and provide a perceptual vision of this important field of nanomedicine.

[Magnetic nanoparticles as tools for cell therapy]

Labelling living cells with magnetic nanoparticles creates opportunities for numerous biomedical applications such as Magnetic Resonance Imaging (MRI) cell tracking, cell manipulation, cell patterning for tissue engineering and magnetically-assisted cell delivery. The unique advantage of magnetic-based methods is to activate or monitor cell behavior by a remote stimulus, the magnetic field. Cell labelling methods using superparamagnetic nanoparticles have been widely developed, showing no adverse effect on cell proliferation and functionalities while conferring magnetic properties to various cell types. This paper first describes how cells can become responsive to magnetic field by safely internalizing magnetic nanoparticles. We next show how magnetic cells can be detected by MRI, giving the opportunity for non-invasive in vivo monitoring of cell migration. We exemplify the fact that MRI cell tracking has become a method of choice to follow the fate of administrated cells in cell therapy assay, whether the cells are grafted locally or administrated in the circulation. Finally we give different examples of magnetic manipulation of cells and their applications to regenerative medicine. Magnetic cell manipulation are forecasted to be more and more developed, in order to improve tissue engineering technique and assist cell-based therapies. Owing to the clinical approval of iron-oxide nanoparticles as MRI contrast agent, there is no major obstacle in the translation to human clinics of the magnetic methods summarized in this paper.

Magnetic nanoparticle-based approaches to locally target therapy and enhance tissue regeneration in vivo

Magnetic-based systems utilizing superparamagnetic nanoparticles and a magnetic field gradient to exert a force on these particles have been used in a wide range of biomedical applications. This review is focused on drug targeting applications that require penetration of a cellular barrier as well as strategies to improve the efficacy of targeting in these biomedical applications. Another focus of this review is regenerative applications utilizing tissue engineered scaffolds prepared with the aid of magnetic particles, the use of remote actuation for release of bioactive molecules and magneto-mechanical cell stimulation, cell seeding and cell patterning.

Monitoring the endocytosis of magnetic nanoparticles by cells using permanent micro-flux sources

Trapping of cells is essential to perform basic handling operations in cell-based microsystems, such as media exchange, concentration, cell isolation and cell sorting. Cell trapping by magnetophoresis typically requires cell labeling with magnetic nanoparticles. Here we report on endocytotic uptake of 100 nm magnetic nanoparticles by Human Embryonic Kidney 293 cells. The attraction of labeled cells by micro-magnet arrays characterised by very high magnetic field gradients (≤10⁶ T/m) was studied as a function of labeling conditions (nanoparticle concentration in the extracellular medium, incubation time). The threshold incubation conditions for effective magnetophoretic trapping were established. This simple technique may be exploited to minimise the quantity of magnetic nanoparticles needed for efficient cell trapping, thus reducing stress or nanoparticle-mediated toxicity. Nanoparticle internalization into cells was confirmed using both confocal and Transmission Electron Microscopy (TEM).

Superparamagnetic iron oxide nanoparticle targeting of MSCs in vascular injury

Vascular occlusion can result in fatal myocardial infarction, stroke or loss of limb in peripheral arterial disease. Interventional balloon angioplasty is a common first line procedure for vascular disease treatment, but long term success is limited by restenosis and neointimal hyperplasia. Cellular therapies have been proposed to mitigate these issues; however efficacy is low, in part due to poor cell retention. We show that magnetic targeting of mesenchymal stem cells gives rise to a 6-fold increase in cell retention following balloon angioplasty in a rabbit model using a clinically applicable permanent magnet. Cells labelled with superparamagnetic iron oxide nanoparticles exhibit no negative effects on cell viability, differentiation or secretion patterns. The increase in stem cell retention leads to a reduction in restenosis three weeks after cell delivery.

Noninvasive quantification of magnetic nanoparticles by means of magnetorelaxometry

Meaningful applications of magnetic nanoparticles (MNP) in biomedicine require the ability to quantify MNP in a variety of environments and biological materials (cells, tissue, and organs). Here we describe a method for the integral, noninvasive quantification of MNP. Our method is based on magnetorelaxometry (MRX), it relies on the detection of their magnetic stray fields which permeate practically unaltered virtually any biological material. MRX provides a specific signal which is not affected by dia- and paramagnetic signals from the biological matrix. We describe how to conduct the MRX experiments and use MNP-assisted gene transfection as the example. The quantification is based on the comparison of the MRX signal of a sample and an appropriate reference sample.

Targeted delivery of human VEGF gene via complexes of magnetic nanoparticle-adenoviral vectors enhanced cardiac regeneration

This study assessed the concept of whether delivery of magnetic nanobeads (MNBs)/adenoviral vectors (Ad)–encoded hVEGF gene (Ad_hVEGF) could regenerate ischaemically damaged hearts in a rat acute myocardial infarction model under the control of an external magnetic field. Adenoviral vectors were conjugated to MNBs with the Sulfo-NHS-LC-Biotin linker. In vitro transduction efficacy of MNBs/Ad–encoded luciferase gene (Ad_luc) was compared with Ad_luc alone in human umbilical vein endothelial cells (HUVECs) under magnetic field stimulation. In vivo, in a rat acute myocardial infarction (AMI) model, MNBs/Ad_hVEGF complexes were injected intravenously and an epicardial magnet was employed to attract the circulating MNBs/Ad_hVEGF complexes. In vitro, compared with Ad_luc alone, MNBs/Ad_luc complexes had a 50-fold higher transduction efficiency under the magnetic field. In vivo, epicardial magnet effectively attracted MNBs/Ad_hVEGF complexes and resulted in strong therapeutic gene expression in the ischemic zone of the infarcted heart. When compared to other MI-treated groups, the MI-M⁺/Ad_hVEGF group significantly improved left ventricular function (p<0.05) assessed by pressure-volume loops after 4 weeks. Also the MI-M⁺/Ad_hVEGF group exhibited higher capillary and arteriole density and lower collagen deposition than other MI-treated groups (p<0.05). Magnetic targeting enhances transduction efficiency and improves heart function. This novel method to improve gene therapy outcomes in AMI treatment offers the potential into clinical applications.

Hybrid nanoparticles for detection and treatment of cancer

There is currently considerable effort to incorporate both diagnostic and therapeutic functions into a single nanoscale system for the more effective treatment of cancer. Nanoparticles have great potential to achieve such dual functions, particularly if more than one type of nanostructure can be incorporated in a nanoassembly, referred to in this review as a hybrid nanoparticle. Here we review recent developments in the synthesis and evaluation of such hybrid nanoparticles based on two design strategies (barge vs. tanker), in which liposomal, micellar, porous silica, polymeric, viral, noble metal, and nanotube systems are incorporated either within (barge) or at the surface of (tanker) a nanoparticle. We highlight the design factors that should be considered to obtain effective nanodevices for cancer detection and treatment.

Can Magnetic Targeting of Magnetically Labeled Circulating Cells Optimize Intramyocardial Cell Retention?

Therapeutic intracavitary stem cell infusion currently suffers from poor myocardial homing. We examined whether cardiac cell retention could be enhanced by magnetic targeting of endothelial progenitor cells (EPCs) loaded with iron oxide nanoparticles. EPCs were magnetically labeled with citrate-coated iron oxide nanoparticles. Cell proliferation, migration, and CXCR4 chemokine receptor expression were assessed in different labeling conditions and no adverse effects of the magnetic label were observed. The magnetophoretic mobility of labeled EPCs was determined in vitro, with the same magnet as that subsequently used in vivo. Coronary artery occlusion was induced for 30 min in 36 rats (31 survivors), followed by 20 min of reperfusion. The rats were randomized to receive, during brief aortic cross-clamping, direct intraventricular injection of culture medium ( n = 7) or magnetically labeled EPCs ( n = 24), with ( n = 14) or without ( n = 10) subcutaneous insertion of a magnet over the chest cavity ( n = 14). The hearts were explanted 24 h later and engrafted cells were visualized by magnetic resonance imaging (MRI) of the heart at 1.5 T. Their abundance in the myocardium was also analyzed semiquantitatively by immunofluorescence, and quantitatively by real-time polymerase chain reaction (RT-PCR). Although differences in cell retention between groups failed to be statistically significant using RT-PCR quantification, due to the variability of the animal model, immunostaining showed that the average number of engrafted EPCs was significantly ten times higher with than without magnetic targeting. There was thus a consistent trend favoring the magnet-treated hearts, thereby suggesting magnetic targeting as a potentially new mean of enhancing myocardial homing of intravascularly delivered stem cells. Magnetic targeting has the potential to enhance myocardial retention of intravascularly delivered endothelial progenitor cells.