Particle surface properties direct cellular immune responses in the lung

Nano- and micro-particulate carriers enable the site-specific delivery for controlled biological responses and can harness the intrinsic pathways by which the body responds to natural invaders. These particles are in the size range which naturally associates with many innate immune cells, including antigen presenting cells (APCs). Through controlled design properties, engineered nano- and microparticle drug delivery vehicles have the potential to expand the breadth of many therapeutic approaches, impacting immunological outcomes through cell-specific targeted delivery. However, in many applications, such as mucosal vaccines or controlled-release lung depots, optimal particle properties have not yet been identified. Physical properties such as size, shape, and surface chemistry are known to impact cellular interactions, particle margination, and biodistribution; as such, many particle design considerations have been established for systemic intravenous (IV) administration to create long-circulating drug delivery vehicles [3]. However, much less is known about particle design parameters which are critical to interfacing with and directing the immune system, especially through non-IV administration. Please click Additional Files below to see the full abstract

Computer modeling of aerosol diffusion through lung mucosa

Diseases of the lung are some of the most common and deadly in the world, accounting for 4 of the top 10 global causes of death according to the World Health Organization. Existing treatments, if any exist, tend to be extremely rigorous, invasive, and time-consuming. Further, due to the poor bioavailability of drugs traditionally administered orally or through injection, these treatments are not very effective. Technology is emerging that allows an aerosolized drug dosage to be delivered directly to the diseased area; however, the mucus layer separating the airways from the tissue (and the blood) remains a barrier to this method. In order to combat this, this research has constructed a physics-based computer model of the mucosal interface between the airways and the lung tissues, providing a much-needed insight into how a vaccine, antibiotic, or other drug must behave to effectively reach the target tissue in various lung regions.The lung has a phenomenal system called the mucociliary clearance mechanism in place to clear foreign particles (including cigarette ash, dust, and bacteria), prevent infection, and keep the lungs healthy. A layer of mucus on the surface of the inner lung is constantly pushed upward towards the throat by a bed of cilia, and most particles that impact on the mucus are cleared from the lungs quickly and without incident. However, when it fails to prevent a disease from being contracted, it remains a barrier to drug delivery, as those particles must cross the same thick mucus layer.The model uses COMSOL Multiphysics software to visualize the mucosa as a cross-section. Data from the literature is used to determine details like dimensions, velocity, and viscosity. The mucus layer moves upwards towards the throat in laminar flow, imitating the mucociliary effect, and the underlying periciliary layer has no net movement due to the regular beating of the cilia that move the mucus. The "drug" enters from the airway side and moves through the fluid by convection. Given these inputs, the model outputs an image showing how much, if any, of the administered particle diffuses through the mucosa and reaches the tissue. The model is extremely customizable, easily modified to simulate other drugs or any other particle so long as some properties are known. Variables have been specifically parametrized to find more complex relationships, like effective diffusivity, from an input of more readily available information, like particle radius. Lung conditions can also be quickly altered to meet the needs of the user (for example, the mucus layer is much thinner in the alveolar region, and the mucus of cystic fibrosis patients is much denser than average). Thus, the model can quickly provide greater insight into the efficacy of new lung treatments.Lew Wentz FoundationChemical Engineerin

Computer modeling of aerosol particle transport through lung mucosa

Diseases of the lung are some of the most common and deadly in the world, accounting for 4 of the top 10 global causes of death according to the World Health Organization. Due to the poor bioavailability of drugs traditionally administered orally or through injection, these treatments have limited efficacy for treating lung diseases. Technology is emerging that allows an aerosolized drug dosage to be delivered directly to the diseased area; however, the mucus layer separating the airways from the tissue (and the blood) remains a barrier to this method. In order to address this, we have constructed a physics-based computational fluid dynamics model of the mucosal interface between the airways and the lung tissues, providing insight into how a vaccine, antibiotic, or other drug must behave to effectively reach the target tissue in various lung regions.The lung has a system called the mucociliary clearance mechanism in place to clear foreign particles (e.g., cigarette ash, dust, and bacteria), prevent infection, and keep the lungs healthy. A layer of mucus on the surface of the inner lung is constantly pushed upward towards the throat by a bed of cilia, and most particles that impact on the mucus are cleared from the lungs quickly and without incident. This mechanism for preventing a disease from being contracted or from particulate damage remains a barrier to drug delivery, as those particles must cross the same thick, non-Newtonian mucus layer.We developed a model using COMSOL Multiphysics software to build a rectangular domain, simulating a cross-sectional slice of the radially symmetrical mucus layer. Data from the literature is used to determine details like mucus depth, velocity, and viscosity. The mucus layer moves upwards towards the throat in laminar flow, imitating the mucociliary effect, and the lower periciliary layer has slower net movement due to the regular beating of the cilia that move the mucus. The viscoelastic properties of mucus are accounted for in the model, with its shear-thinning effects parametrized to a Carreau model. The “drug” particles enter from the airway side and move through the fluid by convection. The Stokes-Einstein equation is used in conjunction with a hydrodynamic and steric hindrance model to calculate an effective diffusivity through the network of glycoproteins that comprises the mucus. Given these inputs, the model generates profiles showing particle concentrations at any point in the simulation domain at any particular time. The model is extremely customizable, easily modified to simulate other drugs or any other particle (including pathogens) provided some properties are known. Complex relationships may be calculated using a small number of easily-measured variables, such as particle diameter. Lung conditions can also be quickly altered to meet the needs of the user (for example, the mucus layer is much thinner in the alveolar region, and the mucus of cystic fibrosis patients is much denser than average). Thus, the model can quickly provide greater insight into the efficacy of new lung treatments, biomechanics of pathogens, and capacity of prophylactics. With the simulation results, we locate optimum dosage sites for a range of particle properties, as the advection of the mucus causes a maximized amount of drug to reach the epithelium some distance upstream of where it impacts the mucus. These results tell us how deep in the lungs a dosage must be delivered and how high its concentration must be to be efficacious.Lew Wentz FoundationChemical Engineerin

Experimental evaluation of receptor-ligand interactions of dual-targeted particles to inflamed endothelium

Vascular-targeted carriers (VTCs) are often designed as leukocyte mimics, conjugated with ligands that target leukocyte adhesion molecules (LAMs) to facilitate specific adhesion to diseased endothelium. VTCs must adhere in regions with dynamic blood flow, frequently requiring multiple ligand-receptor (LR) pairs to provide particle adhesion and high disease specificity. To study LR kinetics under flow, multiple research groups have used protein-coated plates to study the adhesion and rolling of dual-targeted particles in vitro.1-4 While important knowledge is contributed by these studies, they lack the complexity of a diseased physiologic endothelium, as spatiotemporal LAM expression varies widely. Despite decades of research with the ambition of mimicking leukocytes, the specificity of multiple LAM-targeted VTCs remains poorly understood, especially in physiological environments. More specifically, there is a lack of mechanistic understanding of how multiple ligands interact with biologically complex endothelial surfaces under dynamic in vivo environments. Please click Additional Files below to see the full abstract

Evaluation of receptorâ ligand mechanisms of dualâ targeted particles to an inflamed endothelium

Vascularâ targeted carriers (VTCs) are designed as leukocyte mimics, decorated with ligands that target leukocyte adhesion molecules (LAMs) and facilitate adhesion to diseased endothelium. VTCs require different design considerations than other targeted particle therapies; adhesion of VTCs in regions with dynamic blood flow requires multiple ligandâ receptor (LR) pairs that provide particle adhesion and disease specificity. Despite the ultimate goal of leukocyte mimicry, the specificity of multiple LAMâ targeted VTCs remains poorly understood, especially in physiological environments. Here, we investigate particle binding to an inflamed mesentery via intravital microscopy using a series of particles with wellâ controlled ligand properties. We find that the total number of sites of a single ligand can drive particle adhesion to the endothelium, however, combining ligands that target multiple LR pairs provides a more effective approach. Combining sites of sialyl Lewis A (sLeA) and antiâ intercellular adhesion moleculeâ 1 (aICAM), two adhesive molecules, resulted in â ¼3â 7â fold increase of adherent particles at the endothelium over singleâ ligand particles. At a constant total ligand density, a particle with a ratio of 75% sLeA: 25% aICAM resulted in more than 3â fold increase over all over other ligand ratios tested in our in vivo model. Combined with in vivo and in silico data, we find the best dualâ ligand design of a particle is heavily dependent on the surface expression of the endothelial cells, producing superior adhesion with more particle ligand for the lesserâ expressed receptor. These results establish the importance of considering LRâ kinetics in intelligent VTC ligand design for future therapeutics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133573/1/btm210008-sup-0007-suppinfo07.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133573/2/btm210008_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133573/3/btm210008.pd

Nanoparticle surface charge impacts distribution, uptake and lymph node trafficking by pulmonary antigen-presenting cells

AbstractEngineered nanoparticles have the potential to expand the breadth of pulmonary therapeutics, especially as respiratory vaccines. Notably, cationic nanoparticles have been demonstrated to produce superior local immune responses following pulmonary delivery; however, the cellular mechanisms of this increased response remain unknown. To this end, we investigated the cellular response of lung APCs following pulmonary instillation of anionic and cationic charged nanoparticles. While nanoparticles of both surface charges were capable of trafficking to the draining lymph node and were readily internalized by alveolar macrophages, both CD11b and CD103 lung dendritic cell (DC) subtypes preferentially associated with cationic nanoparticles. Instillation of cationic nanoparticles resulted in the upregulation of Ccl2 and Cxc10, which likely contributes to the recruitment of CD11b DCs to the lung. In total, these cellular mechanisms explain the increased efficacy of cationic formulations as a pulmonary vaccine carrier and provide critical benchmarks in the design of pulmonary vaccine nanoparticles.From the Clinical EditorAdvance in nanotechnology has allowed the production of precise nanoparticles as vaccines. In this regard, pulmonary delivery has the most potential. In this article, the authors investigated the interaction of nanoparticles with various types of lung antigen presenting cells in an attempt to understand the cellular mechanisms. The findings would further help the future design of much improved vaccines for clinical use

Controlled analysis of nanoparticle charge on mucosal and systemic antibody responses following pulmonary immunization

To our knowledge, no other nano-based vaccine delivery platform has directly assessed the effects of nanoparticle charge on pulmonary vaccination without affecting other physio/chemical particle characteristics and/or antigen loading. The Particle Replication in Non-Wetting Templates nanoparticle fabrication process is unique in that it allows for isolation of charge as the sole variable in these studies while maintaining all other physical and chemical parameters constant. We find that positively charged nanoparticles induce robust mucosal and systemic antibody responses following pulmonary administration, whereas negatively charged nanoparticles fail to do so. Therefore, our studies underscore the importance of considering nanoparticle charge as a critical design parameter when generating pulmonary-based vaccines and may have implications for particulate vaccination through other routes of administration

Distribution and Cellular Uptake of PEGylated Polymeric Particles in the Lung Towards Cell-Specific Targeted Delivery

We evaluated the role of a poly(ethylene glycol) (PEG) surface coating to increase residence times and alter the cellular fate of nano- and microparticles delivered to the lung

Potent Immune Stimulation from Nanoparticle Carriers Relies on the Interplay of Adjuvant Surface Density and Adjuvant Mass Distribution

Development of novel adjuvant delivery approaches which provide safe and effective immune stimulation are critical for prophylactic and therapeutic advances in a wide range of diseases. Toll-like receptor agonists (TLRas) have been identified as potent stimulators of antigen presenting cells (APCs) and are capable of inducing proinflammatory immune responses desirable for vaccine and immunostimulatory applications. Although TLRas have been successfully incorporated into nanoparticle platforms, minimal work has been done to evaluate the direct role of the adjuvant incorporation in these formulations in directing the immune response. Here, we developed a series of nanoparticle carriers with controlled surface densities of two TLRas, lipopolysaccharide (LPS), corresponding to TLR-4, and CpG oligodeoxynucleotide, corresponding to TLR-9. The proinflammatory cytokine production and expression of costimulatory molecules on APCs were evaluated following a 24 h particle incubation period in vitro using bone marrow derived macrophages and in vivo following particle instillation in the airway of mice. Results demonstrate that proinflammatory cytokine production is predominantly driven by the distribution of the adjuvant dose to a maximal number of cells, whereas the upregulation of costimulatory molecules needed to drive APC maturation and promote adaptive responses indicate the requirement of an optimal density of TLRa on the particle surface. These results indicate that adjuvant surface density is an important parameter for tight control of immune stimulation and provide a foundation for pathogen mimicking particle (PMP) vaccines and immunostimulatory therapeutics

Check the gap: Facemask performance and exhaled aerosol distributions around the wearer.

Current facemask research focuses on material characterization and efficiency; however, facemasks are often not tested such that aerosol distributions are evaluated from the gaps in the sides, bottom, and nose areas. Poor evaluation methods could lead to misinformation on optimal facemasks use; a high-throughput, reproducible method which illuminates the issue of fit influencing aerosol transmission is needed. To this end, we have created an in vitro model to quantify particle transmission by mimicking exhalation aerosols in a 3D printed face-nose-mouth replica via a nebulizer and quantifying particle counts using a hand-held particle counter. A sewn, sewn with pipe cleaner nose piece, and sewn with a coffee filter facemask were used to evaluate current common homemade sewn facemask designs, benchmarked against industry standard surgical, N95 respirator tightly fit, and N95 respirator loosely fit facemasks. All facemasks have significantly reduced particle counts in front of the facemask, but the side and top of the facemask showed increases in particle counts over the no facemask condition at that same position, suggesting that some proportion of aerosols are being redirected to these gaps. An altered size distribution of aerosols that escape at the vulnerable positions was observed; escaped particles have larger count median diameters, with a decreased ratio of smaller to larger particles, possibly due to hygroscopic growth or aggregation. Of the homemade sewn facemasks, the facemask with a coffee filter insert performed the best at reducing escaped aerosols, with increased efficiency also observed for sewn masks with a pipe cleaner nose piece. Importantly, there were minimal differences between facemasks at increasing distances, which supports that social distance is a critical element in reducing aerosol transmission. This work brings to light the importance of quantifying particle count in positions other than directly in front of the facemask and identifies areas of research to be explored