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Recent Advances in Nanomedicine for Ischemic and Hemorrhagic Stroke

2019; Lippincott Williams & Wilkins; Volume: 50; Issue: 5 Linguagem: Inglês

10.1161/strokeaha.118.022744

1524-4628

Thomas Bonnard, Maxime Gauberti, Sara Martínez de Lizarrondo, Francisco Campos, Denis Vivien,

Acute Ischemic Stroke Management

HomeStrokeVol. 50, No. 5Recent Advances in Nanomedicine for Ischemic and Hemorrhagic Stroke Free AccessReview ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissionsDownload Articles + Supplements ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toSupplemental MaterialFree AccessReview ArticlePDF/EPUBRecent Advances in Nanomedicine for Ischemic and Hemorrhagic Stroke Thomas Bonnard, PhD, Maxime Gauberti, PhD, Sara Martinez de Lizarrondo, PhD, Francisco Campos, PhD and Denis Vivien, PhD Thomas BonnardThomas Bonnard From the Normandie University, UNICAEN, INSERM, INSERM UMR-S U1237, Physiopathology and Imaging of Neurological Disorders PhIND, Caen, France (T.B., M.G., S.M.d.L., D.V.) , Maxime GaubertiMaxime Gauberti From the Normandie University, UNICAEN, INSERM, INSERM UMR-S U1237, Physiopathology and Imaging of Neurological Disorders PhIND, Caen, France (T.B., M.G., S.M.d.L., D.V.) , Sara Martinez de LizarrondoSara Martinez de Lizarrondo From the Normandie University, UNICAEN, INSERM, INSERM UMR-S U1237, Physiopathology and Imaging of Neurological Disorders PhIND, Caen, France (T.B., M.G., S.M.d.L., D.V.) , Francisco CamposFrancisco Campos Clinical Neurosciences Research Laboratory, Department of Neurology, Clinical University Hospital, Health Research Institute of Santiago de Compostela, Santiago de Compostela, Spain (F.C.) and Denis VivienDenis Vivien Correspondence to Denis Vivien, PhD, INSERM U1237 Physiopathology and Imaging for Neurological Disorders (PhIND), GIP Cyceron, Bd Henri Becquerel, 14074 Caen, France. Email E-mail Address: [email protected] From the Normandie University, UNICAEN, INSERM, INSERM UMR-S U1237, Physiopathology and Imaging of Neurological Disorders PhIND, Caen, France (T.B., M.G., S.M.d.L., D.V.) CHU Caen, Department of Clinical Research, CHU Caen Côte de Nacre, Caen, France (D.V.). Originally published1 Apr 2019https://doi.org/10.1161/STROKEAHA.118.022744Stroke. 2019;50:1318–1324Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: April 1, 2019: Ahead of Print The emergence of advanced nanotechnologies is having a significant impact on medicine. These past 10 years, a massive research effort in the field has provided to the scientific community a plethora of information around the generation and the use of nanomaterials. Some tools enable vectorization of a molecule of interest to the core of the pathology with minimal systemic delivery, thereby reducing unwanted off-target effects. Engineered nanomaterials may also present specific advantages such as long circulation time, crossing biological barriers, and enhanced targeting properties thanks to the multi-ligand valency enabled.1,2 Yet, those attractive features are highly dependent on the format of nanotools used which vary broadly in terms of shape, size (from 5 to 1000 nm), composition, surface charge, hydrophilicity, conductivity, and rigidity.In regard to stroke treatment, nanomedicine is proving to be a powerful tool.3 In this review, we will analyze the various recent and promising developments according to their purpose of action, whether they show potential (1) to enhance thrombolysis in ischemic stroke, (2) to limit bleeding in hemorrhagic stroke, (3) to reduce neuronal death, and (4) to help for diagnosis-prognosis of stroke.Enhancing Thrombolysis in Ischemic StrokeThrombolysis therapy with intravenous administration of tPA (tissue-type plasminogen activator) is the gold standard treatment for acute ischemic stroke.4 It converts the endogenous plasminogen into plasmin, which in turns lyses the fibrin mesh of the thrombi, thereby promoting recanalization. Yet, the efficacy of tPA is limited to a low rate of early arterial recanalization (≈30%).5 Moreover, beyond the 3 to 4.5 hours therapeutic window, the detrimental side effects outweigh the benefits. tPA is indeed associated with an increased risk of hemorrhagic transformation.6 Recent developments in nanomedicine propose diverse promising approaches to improve thrombolysis therapy (Table I in the online-only Data Supplement).Different types of nanocarriers were used to vectorize plasminogen activators (PAs) to the thrombus site, mostly targeting fibrin or platelets, the 2 main components of blood clots.7 For instance, the encapsulation of PA into platelet targeted liposomes provided similar efficacy to free PA with substantial reduction of bleeding side effects.8 With different systems, where the PA is functionalized on the surface rather than incorporated within the vehicle, the fibrinolytic effect may be potentiated. Thus, nanoparticles coated with tPA and fucoidan—a ligand of P-selectin expressed by activated endothelial cells and platelets—were able to lyse platelet-rich thrombi that are resistant to tPA treatment.9To further increase the specificity of the treatment, smart delivery nanodevices have been developed with the idea of using the thrombosis itself as the trigger for the release of the PA. Several systems exploits the specific proteolytic activity found in thrombosis such as thrombin sensitive capsules10 or phospholipase A2 degradable liposomes.11 The elevated oxidative stress induced by thrombus formation may also be used as a trigger.12 Thrombosis also causes extremely high shear values at the stenotic vessels, and some nanocarriers were developed to be responsive to those high shear conditions such as mechanosensitive liposomes13,14 or shear-sensitive microaggregates.15 The main advantage of these thrombosis responsive approaches is that the amount of fibrinolytic drug released can self-adjust to the severity of thrombosis.Another strategy to control the delivery of PA is to use external stimuli. The application of a magnetic field may be used in coordination with superparamagnetic iron oxide nanoparticles to reach various effects of interest. It may trigger the burst of liposomes to control the release of tPA.16 It can help for the preferential localization to the blood clot via magnetic guidance.17 When excited with an alternating magnetic field, iron oxide nanocubes create a local hyperthermia which accelerates thrombolysis.18 Most recently, much attention is being paid to new magnetic injectable systems developed with the objective to drill the blood clots by means of a magnetically powered helical movement.19–21 Although more in vivo confirmation of the thrombolytic potential is awaited, this cutting-edge technology is exciting and has the advantage of adding localized biomechanical forces to the pharmacological thrombolysis classically limited to the biochemical action on the fibrin fibers.22Ultrasound waves have also been widely explored to enhance thrombolysis. Application of focused ultrasounds can induce the formation and the collapse of gas bubbles within the blood that causes the fragmentation of blood clots. The effect is termed acoustic cavitation and the technique called sonothrombolysis has been tested in a range of clinical trials with mitigated successes.23 This cavitation effect may be potentiated by the injection of preformed gas microbubbles or perfluorocarbon droplets but, to date, clinical trials have not confirmed this benefit for patients. There are promising signs from engineered nanotechnologies which have the potential to further improve the efficacy of this approach with thrombus-targeted bubbles or liposomes which release a cargo of fibrinolytic drug in synergy with the cavitation effect.24 However, it should be noted that for its implementation as ischemic stroke treatment, this strategy carries several challenges such as the strong attenuation of ultrasound by the skull and the increased risk of hemorrhagic transformation.Unfortunately, at this stage, none of these nanothrombolytic approaches has been translated for patient benefit. However, in the precise field of thrombolytic therapy for acute ischemic stroke, the problem may not be solely inherent to the use of nanocarriers, as not any single new pharmacological treatment has been beneficial in clinical trials since tPA in 1995.25 Indeed, the clinical evaluation of a new thrombolytic agent encounters massive obstacles for translation such as the need for large and expensive clinical trials compared with other fields, the requirement to test the novel treatment in combination with standard treatment of tPA (if tested within the 4.5-hour therapeutic window), or however, the difficulty to provide any benefit considering the irreversibility of damage to face when tested after the 4.5-hour time window.Considering the capital importance of reducing the time between stroke onset and thrombolytic administration, the obvious option to save precious time would be to start thrombolysis in prehospital emergency care services. Unfortunately, current approved thrombolytic drugs (ie, tPA) require the differentiation between ischemic and hemorrhagic stroke because of the deleterious effect of tPA if administered to patients presenting with hemorrhage signs. In this context, smart nanomedicines might be of particular interest. Indeed, with a nanosystem ensuring tPA delivery specifically to thrombosis, the unwanted effects of tPA distant from thrombosis should be cut off. As such, this nanosystem could be administered to a stroke patient by ambulance personnel. If the stroke is ischemic, the tPA will be delivered to mediate thrombosis much earlier than usual. If the stroke is hemorrhagic, no tPA will be delivered at the ruptured vessel and thus not worsening the current hemorrhage.Limiting Bleeding in Hemorrhagic StrokeDisruption of vessel wall integrity promotes intracranial bleeding with potentially severe consequences. One of the most important predictors of functional outcome in hemorrhagic stroke patients is the volume of extravasated blood. Boosting the endogenous hemostatic system can stop intracranial bleeding, but the results of clinical trial of hemostatic agents in hemorrhagic stroke patients have been disappointing. For instance, intravenous administration of an activated recombinant form of the coagulation factor VII reduces growth of the hematoma but does not improve functional outcome after intracerebral hemorrhage.26 Moreover, platelet transfusion is deleterious in people taking antiplatelet therapy before intracerebral hemorrhage.27 In the last few years, progress in nanotechnology has led to the development of better targeted and more efficient hemostatic treatments that have the potential to improve our management of hemorrhagic stroke.28A first approach is the use of topical nanomedicines. This consists in the in situ application of biologically active nanomaterials that can promote blood clotting. Ellis-Behnke et al29 demonstrated that a self-assembling peptide nanomaterial could dramatically accelerate hemostasis when applied directly to a wound in the brain or spinal cord. Numerous other topical hemostatic nanomedicines have been developed but, to date, only a few have been tested in brain hemorrhage. Moreover, they are limited to surgical use (for instance by in situ application or injection of the hemostatic material in the cavity of the hematoma), which is of limited interest in the context of most acute hemorrhagic strokes.More promisingly, intravenously administrable nanoparticles have been reported. They consist of polymeric nanoparticles (PNPs) that are targeted to components of naturally occurring clots such as platelets or fibrin, to stabilize their structure and reduce bleeding time. This has been achieved for instance using synthetic platelets made of a poly(lactic-co-glycolic acid)-poly-L-lysine block copolymer core with polyethylene glycol arms terminated with Arg-Gly-Asp (RGD) functionalities.30 These synthetic platelets bind to activated platelets, favoring platelet aggregation, and reducing bleeding time in models of arterial injury. Further refinements of this strategy led to the development of optimized nanoparticles with deformability characteristics closer to endogenous platelets.31 In vivo studies in a mouse model demonstrated that these synthetic platelets better accumulate at the wound site and improve the hemostatic functions of natural platelets. A similar approach targeting fibrin has been developed: it is made of a hemostatic polymer (PolySTAT) that displays a multiple binding site for fibrin, thereby enhancing fibrin crosslinking and preventing clot degradation.32 Intravenous administration of PolySTAT in a rat model of trauma improved survival by reducing blood loss. Although successful in treating peripheral bleeding, the efficacy of these treatments for intracranial bleeding remains to be demonstrated. An important advantage of this approach is that it may only crosslink preformed fibrin mesh. The PolySTAT does not induce thrombogenic effects as long as no fibrin has been generated. This is a major improvement compared with the previous strategies with coagulant factors causing systemic thrombosis.Reducing Neuronal DeathNeuroprotection still represents a major therapeutic objective to prevent the progression of the stroke-triggered damage in the cerebral parenchyma.33 Unfortunately, all protective therapeutic approaches developed so far failed when they were translated into clinical settings, mainly because of the side effects of the drugs, low blood-brain barrier permeability or narrow therapeutic window.In recent years, nanomedicine has attracted much more attention as a safe and effective strategy for transporting neurotherapeutic agents to the brain and solving the main obstacles that have prevented the implementation of experimental neuroprotective therapeutics in humans.34Multiple types of nanoparticles have been tested for drug delivery (Table II in the online-only Data Supplement).34,35 Biodegradable PNPs have been developed as potential carriers for drug delivery to the central nervous system because of their high biocompatibility, nontoxic byproducts inside the body and good sustained-release profiles.36 PNPs have been widely used to be the delivery systems for oligonucleotides, proteins, and small molecules for the treatment of ischemic stroke. PNP materials can mainly be divided into (1) synthetic polymers—that is, poly(lactic acid), poly(glycolic acid), poly(D, L-lactide-co-glycolide acid), polycaprolactone, and its polyethylene glycol derivatives: poly(lactic acid)-polyethylene glycol (PEG), poly(D, L-lactide-co-glycolide acid)-PEG, polycaprolactone-PEG—and (2) natural macromolecular polymers, as chitosan, gelatin, starch, for instance.37 These PNPs have been tested as an effective nanodelivery system for protective drugs (ie, thyroid hormones, retinoic acid, osteopontin, PEGylated epidermal growth factor, and erythropoietin) in animal models of stroke, observing that the neuroprotective effect of the drugs was significantly higher as compared to the administration of the free drug.37Liposomes are by far the most used drug delivery system and already tested in nonstroke clinical trials36 because of their good biocompatibility, biodegradability, blood-brain barrier permeability, and low toxicity. Liposomes are able to encapsulate both hydrophilic and lipophilic drugs, increase their circulation life by changing the lipid composition, size, and charge of the vesicle and to actively target a specific cell or tissue.34 Liposomes coated with PEG have demonstrated their ability to improve in vivo the neuroprotective activity of several drugs, such as minocycline,38 FK506,39 citicoline,40 hemoglobin,41 or xenon.42These nanosystems can be also customized with specific molecular surface modifications to achieve active targeting to brain ischemic region for drug delivery (Figure I in the online-only Data Supplement). For example, HSP72 (heat shock protein 72) was used as a target protein that is specifically expressed in the peri-infarct ischemic region. PEGylated liposomes loaded with citicoline and conjugated with an HSP72 antibody have been shown to selectively accumulate in the brain ischemic region and to increase the beneficial effect of the drug in ischemic middle cerebral artery occlusion animal models.40 Same promising results have also been observed when other neuroprotective drugs, that is, ZL006 or VEGF (vascular endothelial growth factor), were loaded in liposomes and immune-targeted to the ischemic region. The liposomes could effectively reach the area of cerebral injury and significantly ameliorate the infarct volume and the neurological deficit in middle cerebral artery occlusion–induced cerebral ischemia/reperfusion injury.43Mesoporous silica nanoparticles have recently attracted intense attention for drug delivery because of their well-defined and controllable microstructure and excellent biocompatibility. With the exceptionally large surface area and pore volume, these mesoporous particles provide greater capacity for drug loading and surface functionalization. Furthermore, they may be coated with a biodegradable polymer as a gatekeeping layer, enabling controlled drug release. Last but not least, these nanoparticles are able to cross the blood-brain barrier via adsorptive transcytosis.44 Although not too many studies so far have validated the application of mesoporous nanoparticles as a successful drug delivery tool in stroke, a recent study has reported that mesoporous silica nanoparticles loaded with scavenging of reactive oxygen species agents exhibited strong antioxidative and anti-inflammatory activity in rodent models of cerebral hemorrhage, which seems to confirm the potential utility of these nanoparticles for neuroprotective purposes.45In brief, despite the great advantages in nanotechnology to improve the neuroprotection, mainly with the use of liposomes, currently there is no nanomedicine available in the clinic for the management of stroke, mainly conditioned by the lack of a clinical effective neuroprotectant to be tested. One limitation of the neuroprotection approach in clinical setting is that all patients receive the same dose, whatever the stroke severity and timing they present. In this context, a clearer diagnosis including precise measurement of the degree of inflammation could advise a refinement of neuroprotective drug dose on a case-by-case basis. Molecular imaging techniques carry the potential to move towards this personalized medicine approach.Improving Diagnosis With Molecular ImagingComputed tomography and magnetic resonance imaging (MRI) have revolutionized ischemic stroke diagnosis and management. Initially restricted to structural imaging to exclude bleeding, these imaging modalities can now detect intracranial vessel occlusion, evaluate the ischemic penumbra to select candidates for thrombectomy and play a key role in identifying stroke cause. Molecular imaging has the potential to further expand the information provided by computed tomography and MRI by revealing biological processes that constitute potential diagnostic or therapeutic targets.46 To this aim, the use of nanotechnology to design contrast agents has led to significant advances in the field.47About molecular MRI, the recent development of a new family of contrast agents based on microsized particles of iron oxide (MPIO) has allowed a large increase in sensitivity and specificity of this imaging modality (Figure), paving the road for clinical application.48 The use of larger particles with a diameter of at least 1 μm has several advantages compared with the more classically used ultrasmall superparamagnetic iron oxide particles (20–50 nm). Indeed, it prevents the passive leakage of particles in the brain parenchyma and increases the payload of contrast material per particle.49 Using MPIO coupled to monoclonal antibodies, noninvasive detection of specific proteins expressed by the cerebrovasculature has been demonstrated in neurovascular disorders in the last few years.50Download figureDownload PowerPointFigure. Molecular magnetic resonance imaging of endothelial activation in an experimental model of stroke using microsized particles of iron oxide (MPIO). ICAM-1 indicates intercellular adhesion molecule-1; and VCAM-1, vascular cell adhesion molecule-1.Most molecular MRI studies focused on poststroke inflammation, which is one of the main pathogenic processes occurring in the acute and subacute phases of stroke.51 Monitoring the temporospatial regulation of the inflammatory reaction in the affected brain parenchyma could have significant clinical applications such as identifying patient subsets who could benefit from immunomodulatory treatments. The endothelial cells of the blood-brain barrier are key players in poststroke inflammation by mediating the diapedesis of leucocytes from the blood to the brain, through the expression of adhesion molecules. Because these adhesion molecules are easily accessible by large contrast carrying particles, they constitute interesting targets for molecular imaging.Using MPIO coupled to monoclonal antibodies targeted against VCAM-1 (vascular cell adhesion molecule-1), molecular MRI has provided evidence for the existence of an inflammatory penumbra in ischemic stroke.52 Besides VCAM-1, other adhesion molecules are involved in the diapedesis of leukocytes from the blood to the brain. For instance, Deddens and coworkers performed molecular MRI of ICAM-1 (intercellular adhesion molecule-1) in an experimental model of ischemic stroke in mice. They used MPIO targeted to ICAM-1 to reveal the overexpression of ICAM-1 by activated endothelial cells at different time points after ischemic onset.53 They found that ICAM-1 expression was maximal at 48 hours and extended in the peri-infarct area, in line with the inflammatory penumbra concept. Whether VCAM-1 and ICAM-1 imaging provide differential information on stroke pathophysiology remains to be explored. Moreover, Quenault et al54 demonstrated that molecular MRI of P-selectin using MPIO could be used to diagnose a transient ischemic attack. In a transient ischemic attack, the duration of ischemia is too short to induce changes on unenhanced MRI. Interestingly, experimental studies revealed that P-selectin is overexpressed during at least 24 hours in the affected vascular territory. Using molecular MRI of P-selectin, it is, therefore, possible to detect the endothelial activation triggered by the transient ischemic attack and, therefore, to distinguish transient ischemic attack from stroke mimics, such as epilepsy or migraine.Molecular MRI can also help in the etiologic assessment of ischemic stroke. Indeed, it has been previously demonstrated that ruptured atherosclerotic plaques overexpress endothelial activation markers. Using MPIO targeted to P-selectin and VCAM-1, McAteer et al55 demonstrated that it is possible to detect the activated endothelium inside atherosclerotic plaques with MRI. In patients, molecular MRI of endothelial activation could thus be used to find the culprit vascular lesion and, therefore, better characterize stroke cause.Given the demonstration of the high sensitivity and specificity of molecular imaging of inflammation offered by MPIO-enhanced molecular MRI in experimental models, efforts are ongoing to translate this method to clinical imaging. Indeed, the MPIOs used in preclinical studies are not biodegradable because of both their coating and inner structure. In this context, the development of biocompatible MPIOs is mandatory. Recently, Perez-Balderas et al56 reported the production of multimeric magnetite particles forming large MPIO-like particles that are biodegradable. In an experimental model of neuroinflammation, they demonstrated that this method allowed noninvasive imaging of activated endothelial cells.Even if its sensitivity to detect contrast-material is lower than MRI, computed tomography can also be used for molecular imaging using nanoparticles. This has been demonstrated for instance in experimental models of carotid artery thrombosis and embolic ischemic stroke.57 Kim et al57 showed that fibrin targeted gold nanoparticles can reveal cerebral thrombus as high-density endovascular material on computed tomography images. In the acute stroke settings, this would allow assessment of thrombus burden and monitoring of thrombolytic therapy in a noninvasive manner.Conclusions and PerspectivesDespite the successful improvement of stroke therapy with various nanomedicines in preclinical research, none of these systems has yet been translated for patients benefit. In addition to the difficulty inherent to the development of new stroke treatments as previously explained, the use of nanomaterials comes along with substantial risk of toxicity. Because of their bulky format approaching the size of cellular structures, injected particles are more easily recognized as pathogens by the host than soluble molecules, which results in rapid clearance and complementary system activation.58 Nanomaterials may also induce activation of platelets or other factors involved in blood coagulation such as the kallikrein-kinin system or the contact activation pathway, which is of particular concern, especially for a pathology characterized by the presence of thrombosis.59 Besides these potential immune and thrombotic responses on contact to blood components, the nanomedicines may become toxic when entering tissues. The vast majority of intravenously injected nanoparticles are rapidly sequestrated in the tissues by the mononuclear phagocytes system. Within macrophages, the nanoparticles might disrupt organelles such as mitochondria, endoplasmic reticulum, or lysosomes and cause the production of excess reactive oxygen species and the release of proinflammatory mediators.60 Genotoxicity needs to be also closely monitored as the nucleus is also exposed and the DNA may be damaged. For these reasons, the Food Drug Administration and the European Union have adopted specific schemes for the approval and legislation of nanopharmaceuticals requiring an evaluation of these different levels of toxicity.Nonetheless, the field of nanomedicine is appropriately appreciating the toxicity issue of nanomaterials and is proposing an increasing number of solutions. Several reliable techniques such as the decoration with low fouling materials or the use of blood cell membrane camouflage permit a reduction of complement system activation and thrombogenicity while substantially prolongating the circulation time.61 Priority has also been set on the clearance of the injected materials and most nanomedicines developed for intravenous injection are now designed for renal clearance (possible for hydrodynamic diameters below 6 nm) or full biodegradability and recyclability by the mononuclear phagocyte system.62,63 This significant progress towards biocompatibility will support efficient clinical translation. The current challenge consists predominantly in achieving a combination of biocompatible features with the different systems described here, which in preclinical studies have demonstrated their capacity to improve stroke therapy.Sources of FundingThis work was supported by the Institut National de la Santé Et de la Recherche Médicale (INSERM). Dr Bonnard has received funding from Université Caen Normandy (UCN).DisclosuresDr Gauberti and Vivien are coauthors of a patent on molecular imaging of P-selectin: Imaging method for predicting the onset of multiple sclerosis (PCT/WO2017134178 A1). Dr Vivien is coauthor of a patent on non-neurotoxic Optimized tPA (tissue-type plasminogen activator; licensed US9249406 B2) and on an antibody preventing tPA-NMDA interaction, Glunomab (issued PCT/WO2014187879). The other authors report no conflicts.FootnotesThe online-only Data Supplement is available with this article at https://www.ahajournals.org/doi/suppl/10.1161/STROKEAHA.118.022744.Correspondence to Denis Vivien, PhD, INSERM U1237 Physiopathology and Imaging for Neurological Disorders (PhIND), GIP Cyceron, Bd Henri Becquerel, 14074 Caen, France. Email [email protected]frReferences1. Weissleder R, Kelly K, Sun EY, Shtatland T, Josephson L. 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