Adhesion kinetics of functionalized nano-particles under high shear conditions

Arterial thrombosis, the formation of blood clot within an artery, is a complex process that consists of multiple steps. These steps are orchestrated by three main factors: high shear flow, prothrombogenic surface (collagen), and blood components mainly von Willebrand factor (vWF) and platelets. One of the essential early events in thrombus initiation under high shear conditions are the interactions between vWF and platelet\u27s receptor GPIbα. Here we study the adhesion kinetics of platelet\u27s GPIbα receptor functionalized-nano particles on different coated-channels under defined hemodynamic conditions. Please click Additional Files below to see the full abstract

Targeted drug delivery in arterial stenosis - role of hemodynamics

Hemodynamics play a central role in cardiovascular targeted drug delivery systems. Sites of abnormal vascular narrowing (stenosis) exhibit unique flow features including an abnormally elevated level of shear stress as well re-circulating flows downstream of the narrowing. Here we study the deposition of particulate drug carries in models of arterial stenosis under defined hemodynamic conditions. First, fluorescently tagged Poly (Lactic-co-Glycolic Acid) (PLGA) nano-particles functionalized with collagen targeting motifs have been fabricated. Then experiments in a microfluidic channels coated with collagen were performed to characterize the adhesion properties of the examined particles as a function of shear. Next, perfusion experiments on collagen coated millimeter sized vascular models of stenotic coronary arteries have been performed using a custom-built perfusion system capable of emulating pulsatile physiological flow. The particle deposition was monitored using time-lapse fluorescence microscopy at defined locations within the model. Our results show that particle size and coating density affect the deposition pattern within the stenosis and that there is correlation between the microfluidic results under defined shear stress and the deposition in the stenosis models. Altogether our results illustrate the key role of hemodynamics in designing cardiovascular nano-medicines. . Please click Additional Files below to see the full abstract

True-scale biomimetic multi-generation airway platforms of the human bronchial epithelium for in vitro cytotoxicity screening

Lung exposure to inhaled particulate matter may injure the epithelial tissue and lead to a loss of function in affected regions via inflammation for example. Screening for the critical contaminate concentrations may provide essential information towards damage assessment and epithelial healing. To date, most approaches have typically relied on traditional in vitro well plate assays or alternatively in vivo animal experiments. Yet, such methods manifest some outstanding disadvantages such as the inability to capture physiological flow and aerosol deposition characteristics as well as significant differences in anatomy, immune system and inflammatory responses compared to humans. The advent of organ-on-chip platforms has shown promising results to reconcile many such drawbacks. In an attempt to provide an attractive in vitro gateway to monitor airway health, we discuss here a novel biomimetic platform which emulates the bronchial epithelium of a human upper airway, allowing to study organ-level characteristics in a homeostatic cellular microenvironment. This device reconstitutes a multi-generation pulmonary epithelial airway environment, capturing realistic respiratory transport phenomena and critical cellular barrier functions at an air-liquid interface (ALI), in analogy to the bronchial lumen. As a proof of concept, we demonstrate its feasibility for in vitro based assays by exposing the device to cytotoxic aerosolized particles under respiratory flow conditions. Subsequently, we investigate the cytotoxic effects of these particles including cellular viability, cytokine and mucus secretion as a function of local particle deposition patterns. Ultimately, our bronchial airway models are intended to provide off-the-shelf in vitro kits geared for the end-user interested in a wide range of broader biological assays that may be attractive for cytotoxicity and drug screening. Please click Additional Files below to see the full abstract

Biophysical targeting of high-risk cerebral aneurysms

Localized delivery of diagnostic/therapeutic agents to cerebral aneurysms, lesions in brain arteries, may offer a new treatment paradigm. Since aneurysm rupture leading to subarachnoid hemorrhage is a devastating medical emergency with high mortality, the ability to noninvasively diagnose high-risk aneurysms is of paramount importance. Moreover, treatment of unruptured aneurysms with invasive surgery or minimally invasive neurointerventional surgery poses relatively high risk and there is presently no medical treatment of aneurysms. Here, leveraging the endogenous biophysical properties of brain aneurysms, we develop particulate carriers designed to localize in aneurysm low-shear flows as well as to adhere to a diseased vessel wall, a known characteristic of high-risk aneurysms. We first show, in an in vitro model, flow guided targeting to aneurysms using micron-sized (2 mum) particles, that exhibited enhanced targeting ( \u3e 7 folds) to the aneurysm cavity while smaller nanoparticles (200 nm) showed no preferable accumulation. We then functionalize the microparticles with glycoprotein VI (GPVI), the main platelet receptor for collagen under low-medium shear, and study their targeting in an in vitro reconstructed patient-specific aneurysm that contained a disrupted endothelium at the cavity. Results in this model showed that GPVI microparticles localize at the injured aneurysm an order of magnitude ( \u3e 9 folds) more than control particles. Finally, effective targeting to aneurysm sites was also demonstrated in an in vivo rabbit aneurysm model with a disrupted endothelium. Altogether, the presented biophysical strategy for targeted delivery may offer new treatment opportunities for cerebral aneurysms

Endothelial Cell Activation in an Embolic Ischemia-Reperfusion Injury Microfluidic Model

Ischemia, lack of blood supply, is associated with a variety of life-threatening cardiovascular diseases, including acute ischemic stroke and myocardial infraction. While blood flow restoration is critical to prevent further damage, paradoxically, rapid reperfusion can increase tissue damage. A variety of animal models have been developed to investigate ischemia/reperfusion injury (IRI), however they do not fully recapitulate human physiology of IRI. Here, we present a microfluidic IRI model utilizing a vascular compartment comprising human endothelial cells, which can be obstructed via a human blood clot and then re-perfused via thrombolytic treatment. Using our model, a significant increase in the expression of the endothelial cell inflammatory surface receptors E-selectin and I-CAM1 was observed in response to embolic occlusion. Following the demonstration of clot lysis and reperfusion via treatment using a thrombolytic agent, a significant decrease in the number of adherent endothelial cells and an increase in I-CAM1 levels compared to embolic occluded models, where reperfusion was not established, was observed. Altogether, the presented model can be applied to allow better understanding of human embolic based IRI and potentially serve as a platform for the development of improved and new therapeutic approaches

The Flow Dependent Adhesion of von Willebrand Factor (VWF)-A1 Functionalized Nanoparticles in an in Vitro Coronary Stenosis Model

In arterial thrombosis, von Willebrand factor (VWF) bridges platelets to sites of vascular injury. The adhesive properties of VWF are controlled by its different domains, which may be engineered into ligands for targeting nanoparticles to vascular injuries. Here, we functionalized 200 nm polystyrene nanoparticles with the VWF-A1 domain and studied their spatial adhesion to collagen or collagen-VWF coated, real-sized coronary stenosis models under physiological flow. When VWF-A1 nano-particles (A1-NPs) were perfused through a 75% stenosis model coated with collagen-VWF, the particles preferentially adhered at the post stenotic region relative to the pre-stenosis region while much less adhesion was detected at the stenosis neck (~ 65-fold less). When infused through collagen-coated models or when the A1 coating density of nanoparticles was reduced by 100-fold, the enhanced adhesion at the post-stenotic site was abolished. In a 60% stenosis model, the adhesion of A1-NPs to collagen-VWF-coated models depended on the location examined within the stenosis. Altogether, our results indicate that VWF-A1 NPs exhibit a flow-structure dependent adhesion to VWF and illustrate the important role of studying cardiovascular nano-medicines in settings that closely model the size, geometry, and hemodynamics of pathological environments

Targeted drug delivery to flow-obstructed blood vessels using mechanically activated nanotherapeutics

Obstruction of normal blood flow, which occurs in a variety of diseases, including thromboembolism in stroke and atherosclerosis, is a leading cause of death and long-term adult disability in the Western world. This review focuses on a novel nanotherapeutic drug-delivery platform that is mechanically activated within blood vessels by high-fluid shear stresses to selectively target drugs to sites of vascular obstruction. In vitro and in vivo studies have shown that this approach can be used to efficiently lyse clots using a significantly lower amount of thrombolytic drug than is required when administered in a soluble formulation. This nanotherapeutic strategy can potentially improve both the efficacy and safety of thrombolytic drugs, particularly in patients who are at high risk for brain hemorrhage, and thus provide a new approach for the treatment of many life-threatening and debilitating vascular disorders

A double‐edged sword: The complex interplay between engineered nanoparticles and platelets

Abstract Nanoparticles (NP) play a crucial role in nanomedicine, serving as carriers for localized therapeutics to allow for precise drug delivery to specific disease sites and conditions. When injected systemically, NP can directly interact with various blood cell types, most critically with circulating platelets. Hence, the potential activation/inhibition of platelets following NP exposure must be evaluated a priori due to possible debilitating outcomes. In recent years, various studies have helped resolve the physicochemical parameters that influence platelet‐NP interactions, and either emphasize nanoparticles' therapeutic role such as to augment hemostasis or to inhibit thrombus formation, or conversely map their potential undesired side effects upon injection. In the present review, we discuss some of the main effects of several key NP types including polymeric, ceramic, silica, dendrimers and metallic NPs on platelets, with a focus on the physicochemical parameters that can dictate these effects and modulate the therapeutic potential of the NP. Despite the scientific and clinical significance of understanding Platelet‐NP interactions, there is a significant knowledge gap in the field and a critical need for further investigation. Moreover, improved guidelines and research methodologies need to be developed and implemented. Our outlook includes the use of biomimetic in vitro models to investigate these complex interactions under both healthy physiological and disease conditions