Particulate Drug Carriers Research Articles

Activation of the complement system by nanoparticles and strategies for complement inhibition

The complement system is a multicomponent and multifunctional arm of the innate immune system. Complement contributes to non-specific host defence and maintains homeostasis through multifaceted processes and pathways, including crosstalk with the adaptive immune system, the contact (coagulation) and the kinin systems, and alarmin high-mobility group box 1. Complement is also present intracellularly, orchestrating a wide range of housekeeping and physiological processes in both immune and nonimmune cells, thus showing its more sophisticated roles beyond innate immunity, but its roles are still controversial. Particulate drug carriers and nanopharmaceuticals typically present architectures and surface patterns that trigger complement system in different ways, resulting in both beneficial and adverse responses depending on the extent of complement activation and regulation as well as pathophysiological circumstances. Here we consider the role of complement system and complement regulations in host defence and evaluate the mechanisms by which nanoparticles trigger and modulate complement responses. Effective strategies for the prevention of nanoparticle-mediated complement activation are introduced and discussed.

Cargo-free particles divert neutrophil-platelet aggregates to reduce thromboinflammation

The combination of inflammation and thrombosis is a hallmark of many cardiovascular diseases. Under such conditions, platelets are recruited to an area of inflammation by forming platelet-leukocyte aggregates via interaction of PSGL-1 on leukocytes and P-selectin on activated platelets, which can bind to the endothelium. While particulate drug carriers have been utilized to passively redirect leukocytes from areas of inflammation, the downstream impact of these carriers on platelet accumulation in thromboinflammatory conditions has yet to be studied. Here, we explore the ability of polymeric particles to divert platelets away from inflamed blood vessels both in vitro and in vivo. We find that untargeted and targeted micron-sized polymeric particles can successfully reduce platelet adhesion to an inflamed endothelial monolayer in vitro in blood flow systems and in vivo in a lipopolysaccharide-induced, systemic inflammation murine model. Our data represent initial work in developing cargo-free, anti-platelet therapeutics specifically for conditions of thromboinflammation.

Meeting Challenges of Pediatric Drug Delivery: The Potential of Orally Fast Disintegrating Tablets for Infants and Children.

A majority of therapeutics are not available as suitable dosage forms for administration to pediatric patients. The first part of this review provides an overview of clinical and technological challenges and opportunities in the development of child-friendly dosage forms such as taste masking, tablet size, flexibility of dose administration, excipient safety and acceptability. In this context, developmental pharmacology, rapid onset of action in pediatric emergency situations, regulatory and socioeconomic aspects are also reviewed and illustrated with clinical case studies. The second part of this work discusses the example of Orally Dispersible Tablets (ODTs) as a child-friendly drug delivery strategy. Inorganic particulate drug carriers can thereby be used as multifunctional excipients offering a potential solution to address unique medical needs in infants and children while maintaining a favorable excipient safety and acceptability profile in these vulnerable patient populations.

Nanometer- and angstrom-scale characteristics that modulate complement responses to nanoparticles.

The contribution of the complement system to non-specific host defence and maintenance of homeostasis is well appreciated. Many particulate systems trigger complement activation but the underlying mechanisms are still poorly understood. Activation of the complement cascade could lead to particle opsonisation by the cleavage products of the third complement protein and might promote inflammatory reactions. Antibody binding in a controlled manner and/or sensing of particles by the complement pattern-recognition molecules such as C1q and mannose-binding lectin can trigger complement activation. Particle curvature and spacing arrangement/periodicity of surface functional groups/ligands are two important parameters that modulate complement responses through multivalent engagement with and conformational regulation of surface-bound antibodies and complement pattern-recognition molecules. Thus, a better fundamental understanding of nanometer- and angstrom-scale parameters that modulate particle interaction with antibodies and complement proteins could portend new possibilities for engineering of particulate drug carriers and biomedical platforms with tuneable complement responses and is discussed here.

NANO-BASED THERAPY FOR TREATMENT OF SKIN CARCINOMA

Skin carcinoma is a frequently occurring cancer caused due to ultra violet rays of the Sun. It starts from normal skin cells but later on transforms into cells which undergo uncontrolled mitosis. Skin cancer is not as deadly as other cancers and has no metastasis and is not life threatening. Conventional chemotherapy has in general failed to treat skin cancer due to non specific targeting, which is accompanied by several side effects. Novel therapeutic approach based on nanotechnology have emerged as the best alternative for skin cancer treatment. We presented current scenario of nano based particulate drug carrier approaches for effective therapy for skin carcinoma by reducing side effects. This approach also reduces frequency of administration and improves patient compliance. Nanotechnology has emerged as the best alternative for conventional therapy for the effective treatment of skin cancer. Nanoparticles can specifically target skin carcinoma and are able to sustain drug release and reduce side effects to a greater extent.

Beyond Trial and Error: A Systematic Development of Liposomes Targeting Primary Macrophages

Monocytes/macrophages are phagocytic innate immune cells playing a pivotal role in tissue homeostasis, inflammation, and antitumor immunity in a microenvironment‐dependent manner. By expressing pattern recognition and scavenger receptors on their surface, macrophages selectively take up pathogens, cellular debris, and often—undesirably—drug delivery systems. On the other hand, the propensity of phagocytic cells to internalize particulate drug carriers is used to load them with a cargo of choice, turning the monocytes/macrophages into a diagnostic or therapeutic Trojan horse. Identifying the ideal physicochemical properties of particulate carriers such as liposomes to achieve the most efficient macrophage‐mediated drug delivery has been object of extensive research in the past, but the studies reported so far rely solely on trial‐and‐error approaches. Herein, a design of experiment (DoE) strategy to identify the optimal liposomal formulation is proposed, fully characterized in terms of size, surface charge, and membrane fluidity, to maximize macrophage targeting. The findings are validated using mouse bone marrow‐derived macrophages, a primary preparation modeling in vivo monocyte‐derived macrophages, thus confirming the robustness and versatility of the systematic and iterative approach and suggesting the promising potential of the DoE approach for the design of cell‐targeting delivery systems.

Computational and experimental investigation of particulate matter deposition in cerebral side aneurysms.

Intracranial aneurysms frequently develop blood clots, plaque and inflammations, which are linked to enhanced particulate mass deposition. In this work, we propose a computational model for particulate deposition, that accounts for the influence of field forces, such as gravity and electrostatics, which produce an additional flux of particles perpendicular to the fluid motion and towards the wall. This field-mediated flux can significantly enhance particle deposition in low-shear environments, such as in aneurysm cavities. Experimental investigation of particle deposition patterns in in vitro models of side aneurysms, demonstrated the ability of the model to predict enhanced particle adhesion at these sites. Our results showed a significant influence of gravity and electrostatic forces (greater than 10%), indicating that the additional terms presented in our models may be necessary for modelling a wide range of physiological flow conditions and not only for ultra-low shear regions. Spatial differences between the computational model and the experimental results suggested that additional transport and fluidic mechanisms affect the deposition pattern within aneurysms. Taken together, the presented findings may enhance our understanding of pathological deposition processes at cardiovascular disease sites, and facilitate rational design and optimization of cardiovascular particulate drug carriers.

PCN-223 as a drug carrier for potential treatment of colorectal cancer

Colorectal cancer is the second leading cause of cancer-related deaths worldwide. CRC is often treated with intravenous 5-fluorouracil (5FU). However, 5FU frequently shows low therapeutic efficacy and serious adverse events. Particulate drug carriers able to enhance intracellular delivery could be advantageous, since higher 5FU concentrations would be engulfed by cancer cells during a relatively short residence within the rectal space to improve local anti-cancer efficacy. Therefore, we propose a novel material based on a zirconium-based metal-organic framework (MOF), PCN-223, as a potential carrier of 5FU for rectal delivery of treatment for CRC. PCN-223 nanoparticles, prepared by the solvothermal method, exhibited a highly porous structure, whereby 79.4μg/mg 5FU could be encapsulated and released in a sustained manner over 2h in vitro. PCN-223 was internalized by the human colorectal cancer cell line, HCT-116, within 2h, representing the period that rectally delivered particles reside within the rectum. Consequently, 5FU-loaded PCN-223 (5FU@PCN-223) treatment decreased the viability of HCT-116 cells compared with treatment with a bolus 5FU solution, suggesting improved drug efficacy over a short exposure time. Therefore, PCN-223 may be a promising carrier for rectal delivery of 5FU for treatment of colorectal cancer.

Design, Development, Characterization of Solid Lipid Nanoparticles for Oral Administration

A high potential for drug delivery has been attributed to particulate drug carriers, especially small particles such as micro particles and colloidal system in nanometer range. Controlled and targeted delivery is one the most enviable requirements from a carrier, which involves the multidisciplinary site-specific or targeted approach. Nanoparticles have important potential applications for the administration of therapeutic and diagnostic agents. Nanoparticulate drug delivery system may offer plenty of advantages over conventional dosage forms which include improved, reduced toxicity, enhanced biodistribution and improved patient compliance. Pharmaceutical Nanoparticles are subnano sizes structures, which contain drug or bioactive substances within them and are constituted of several tens or hundreds of atoms or molecules and morphologies (amorphous, crystalline, spherical, needles). Montelukast sodium (MKS) is a potent, orally active, and has high affinity and selectively binds to the cysteinyl leukotriene 1 (CysLT1) receptor as compared to the prostanoid, cholinergic or β-adrenergic airway receptor. The main drawback of conventional montelukast formulation is that it undergoes hepatic first pass metabolism. The Cumulative % drug release with respect to time was found to be 95.38% for the optimized batch. From the oral bioavailability study it became evident that enhancement in the bioavailability of MKS was observed after drug-loaded SLNs have been administered in in vivo.

Model Particulate Drug Carriers Modulate Leukocyte Adhesion in Human Blood Flows.

Drug carriers have been widely explored as a method of improving the efficacy of therapeutic drugs for a variety of diseases, including those involving inflammation. However, few of these formulations have advanced past clinical trials. There are still major gaps in our understanding of how drug carriers impact leukocytes, particularly in inflammatory conditions. In this work, we investigated how targeted and nontargeted drug carriers affect the function of leukocytes in blood flow. We explored three primary mechanisms: (1) collisions in blood flow disrupt leukocyte adhesion, (2) specific binding to the endothelium competes with leukocytes for binding sites, and (3) particle phagocytosis alters leukocyte phenotype, resulting in reduced adhesion. We find that each of these mechanisms contributes to significantly reduced leukocyte adhesion to an inflamed endothelium, and that particle phagocytosis may be the most significant driver of this effect. These results are crucial for understanding the totality of the impact of drug carriers on leukocyte behavior and response to inflammation and should inform the future design of any such drug carriers.

DOX-Conjugated keratin nanoparticles for pH-Sensitive drug delivery

Keratin is a good candidate for drug carrier due to its good biocompatibility, low immunogenicity, redox responsiveness, and abundant renewable sources. Herein, doxorubicin (DOX) was first conjugated with keratin through a pH-sensitive hydrazone linkage, and then prepared into particulate drug carrier via desolvation method. The size, morphology, and surface potential of keratin-DOX nanoparticles (KDNPs) were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The drug release results showed that KDNPs performed an excellent pH-sensitive behavior under acidic tumor microenvironment. Cytotoxicity assay by MTT confirmed that KDNPs exhibited the enhanced cytotoxicity against A549 cells. Furthermore, KDNPs had higher therapeutic efficiency in vivo than free DOX. Hemolysis assay indicated that KDNPs was blood compatible. All the results identified that KDNPs are well suited as an ideal drug carrier.

Phagocytosis of spherical and ellipsoidal micronetwork colloids from crosslinked poly(ε-caprolactone).

The effect of non-spherical particle shapes on cellular uptake has been reported as a general design parameter to control cellular recognition of particulate drug carriers. Beside shape, also size and cell-particle ratio should mutually effect phagocytosis. Here, the capability to control cellular uptake of poly(ɛ-caprolactone) (PCL) based polymer micronetwork colloids (MNC), a carrier system that can be transferred to various shapes, is explored in vitro at test conditions allowing multiple cell-particle contacts. PCL-based MNC were synthesized as spheres with a diameter of ∼6, ∼10, and 13 µm, loaded with a fluorescent dye by a specific technique of swelling, re-dispersion and drying, and transferred into different ellipsoidal shapes by a phantom stretching method. The boundaries of MNC deformability to prolate ellipsoid target shapes were systematically analyzed and found to be at an aspect ratio AR of ∼4 as obtained by a phantom elongation εph of ∼150%. Uptake studies with a murine macrophages cell line showed shape dependency of phagocytosis for selected conditions when varying particle sizes (∼6 and 10 μm),and shapes (εph: 0, 75 or 150%), cell-particle ratios (1:1, 1:2, 1:10, 1:50), and time points (1-24 h). For larger-sized MNC, there was no significant shape effect on phagocytosis as these particles may associate with more than one cell, thus increasing the possibility of phagocytosis by any of these cells. Accordingly, controlling shape effects on phagocytosis for carriers made from degradable polymers relevant for medical applications requires considering further parameters besides shape, such as kinetic aspects of the exposure and uptake by cells.

Loading of Porous Functionalized Calcium Carbonate Microparticles: Distribution Analysis with Focused Ion Beam Electron Microscopy and Mercury Porosimetry.

Accurate analysis of intraparticle distribution of substances within porous drug carriers is important to optimize loading and subsequent processing. Mercury intrusion porosimetry, a common technique used for characterization of porous materials, assumes cylindrical pore geometry, which may lead to misinterpretation. Therefore, imaging techniques such as focused ion beam scanning electron microscopy (FIB-SEM) help to better interpret these results. The purpose of this study was to investigate the differences between mercury intrusion and scanning electron microscopy and to identify the limitations of each method. Porous microparticles, functionalized calcium carbonate, were loaded with bovine serum albumin and dipalmitoylphosphatidylcholine (DPPC) by solvent evaporation and results of the pore size distribution obtained by both methods were compared. The internal structure of the novel pharmaceutical excipient, functionalized calcium carbonate, was revealed for the first time. Our results demonstrated that image analysis provides a closer representation of the material distribution since it was possible to discriminate between blocked and filled pores. The physical nature of the loaded substances is critical for the deposition within the pores of functionalized calcium carbonate. We conclude, that a combination of mercury intrusion porosimetry and focused ion beam scanning electron microscopy allows for a reliable analysis of sub-micron porous structures of particulate drug carriers.

Uptake of silica particulate drug carriers in an intestine-on-a-chip: towards a better in vitro model of nanoparticulate carrier and mucus interactions.

Micro and nano-particulate carriers have potential to increase bioavailability of oral drugs, but must first overcome the mucus barrier of the intestinal epithelium to facilitate absorption and entry to systemic circulation. We report on mucus-silica nanoparticulate carrier interactions in an in vitro intestine-on-a-chip (IOAC) microfluidic model. Caco-2 cells cultured within the IOAC model recapitulate the morphology of the human intestinal epithelium that is currently lacking in traditional static Transwell models. Fine control over the cell culture conditions produced a mucus layer, previously problematic to achieve without employing cell co-culture. The microdevice design also allowed for direct imaging of silica particulate carrier (40-700 nm) uptake through the mucus and cellular monolayer. PEGylated particulate carriers penetrated more readily through the mucus layer compared to non-PEGylated particulate carriers while larger particulate carriers tended to retard particulate carrier penetration through a dense mucus mesh. This was confirmed via imaging flow cytometry and UV-fluorescence spectroscopy. The IOAC also demonstrated the ability to mimic intestinal peristaltic fluidic conditions, which in turn affects the particulate carrier uptake. This in vitro IOAC model has potential to directly elucidate mucus interactions and uptake mechanisms for a range of drug carrier systems.

PEGylation of model drug carriers enhances phagocytosis by primary human neutrophils

Targeted drug carriers are attractive for the delivery of therapeutics directly to the site of a disease, reducing systemic side effects and enhancing the efficacy of therapeutic molecules. However, the use of particulate carriers for drug delivery comes with its own set of challenges and barriers. Among these, a great deal of research effort has focused on protecting carriers from clearance by phagocytes via altering carrier surface chemistry, mostly with the use of polyethylene glycol (PEG) chain coatings. However, few papers have explored the effects of PEGylation on uptake by freshly-obtained primary human phagocytes in physiological conditions. In this work, we investigate the effect of PEGylation on particle uptake by primary human neutrophils in vitro and compare these effects to several cell lines and other model phagocytic cells systems. We find that human neutrophils in whole blood preferentially phagocytose PEGylated particles (e.g., ∼40% particle positive neutrophils for PEGylated versus ∼20% for carboxylated polystyrene microspheres) and that this effect is linked to factors present in human plasma. Model phagocytes internalized PEGylated particles less efficiently or equivalently to carboxylated particles in culture medium but preferentially phagocytosed PEGylated particles in the human plasma (e.g., ∼86% versus ∼63% PEGylated versus carboxylated particle positive cells, respectively). These findings have significant implications for the efficacy of PEGylation in designing long-circulating drug carriers, as well as the need for thorough characterization of drug carrier platforms in a wide array of in vitro and in vivo assays. Statement of SignificanceThe work in this manuscript is highly significant to the field of drug delivery, as it explores in-depth the effects of polyethylene glycol (PEG) coatings, which are frequently used to prevent phagocytic clearance of particulate drug carriers, on the phagocytosis of such carriers by neutrophils, the most abundant leukocyte in blood circulation. Surprisingly, we find that PEGylation enhances uptake by primary human neutrophils, specifically in the presence of human plasma. This result suggests that PEGylation may not confer the benefits in humans once thought, and may help to explain why PEG has not become the “magic bullet” it was once thought to be in the field of particulate drug delivery.

MR-guided transcranial focused ultrasound safely enhances interstitial dispersion of large polymeric nanoparticles in the living brain.

Generating spatially controlled, non-destructive changes in the interstitial spaces of the brain has a host of potential clinical applications, including enhancing the delivery of therapeutics, modulating biological features within the tissue microenvironment, altering fluid and pressure dynamics, and increasing the clearance of toxins, such as plaques found in Alzheimer’s disease. Recently we demonstrated that ultrasound can non-destructively enlarge the interstitial spaces of the brain ex vivo. The goal of the current study was to determine whether these effects could be reproduced in the living brain using non-invasive, transcranial MRI-guided focused ultrasound (MRgFUS). The left striatum of healthy rats was treated using MRgFUS. Computer simulations facilitated treatment planning, and targeting was validated using MRI acoustic radiation force impulse imaging. Following MRgFUS treatments, Evans blue dye or nanoparticle probes were infused to assess changes in the interstitial space. In MRgFUS-treated animals, enhanced dispersion was observed compared to controls for 70 nm (12.8 ± 0.9 mm3 vs. 10.6 ± 1.0 mm3, p = 0.01), 200 nm (10.9 ± 1.4 mm3 vs. 7.4 ± 0.7 mm3, p = 0.01) and 700 nm (7.5 ± 0.4 mm3 vs. 5.4 ± 1.2 mm3, p = 0.02) nanoparticles, indicating enlargement of the interstitial spaces. No evidence of significant histological or electrophysiological injury was identified. These findings suggest that transcranial ultrasound can safely and effectively modulate the brain interstitium and increase the dispersion of large therapeutic entities such as particulate drug carriers or modified viruses. This has the potential to expand the therapeutic uses of MRgFUS.

Neutrophil-Particle Interactions in Blood Circulation Drive Particle Clearance and Alter Neutrophil Responses in Acute Inflammation.

Although nano- and microparticle therapeutics have been studied for a range of drug delivery applications, the presence of these particles in blood flow may have considerable and understudied consequences to circulating leukocytes, especially neutrophils, which are the largest human leukocyte population. The objective of this work was to establish if particulate drug carriers in circulation interfere with normal neutrophil adhesion and migration. Circulating blood neutrophils in vivo were found to be capable of rapidly binding and sequestering injected carboxylate-modified particles of both 2 and 0.5 μm diameter within the bloodstream. These neutrophil-particle associations within the vasculature were found to suppress neutrophil interactions with an inflamed mesentery vascular wall and hindered neutrophil adhesion. Furthermore, in a model of acute lung injury, intravenously administered drug-free particles reduced normal neutrophil accumulation in the airways of C57BL/6 mice between 52% and 60% versus particle-free mice and between 93% and 98% in BALB/c mice. This suppressed neutrophil migration resulted from particle-induced neutrophil diversion to the liver. These data indicate a considerable acute interaction between injected particles and circulating neutrophils that can drive variations in neutrophil function during inflammation and implicate neutrophil involvement in the clearance process of intravenously injected particle therapeutics. Such an understanding will be critical toward both enhancing designs of drug delivery carriers and developing effective therapeutic interventions in diseases where neutrophils have been implicated.

Monoacyl-phospatidylcholine nanostructured lipid carriers: Influence of lipid and surfactant content on in vitro skin permeation of flufenamic acid and fluconazole

Monoacyl-phosphatidylcholine (MAPL) is a skin-friendly phospholipid emulsifier that has successfully been employed for development of microemulsions. Its potential for stabilising particulate lipid drug carriers has not been explored so far. Thus, the aim of the present study was the development of MAPL-based nanostructured lipid carriers (NLC) as dermal drug delivery system with optimised physical stability. To this end, extensive comparative studies were performed and the role of crucial formulation parameters such as total lipid or surfactant content was investigated. Both blank placebo NLC and drug-loaded systems were developed using flufenamic acid and fluconazole as model drugs of different polarity. The resulting systems were characterised using photon correlation spectroscopy, laser Doppler electrophoresis, rheological measurements and cryo transmission electron microscopy. In vitro skin diffusion studies revealed that interestingly, both a low surfactant content and a low total lipid content led to increased skin permeation of flufenamic acid in vitro. According to its different polarity, a different trend was observed for fluconazole where higher surfactant contents in combination with different total lipid contents yielded the highest skin permeation. Satisfying long-term stability of the NLC formulations with optimised physical parameters was observed for a period of 30 weeks.

Particle Targeting in Complex Biological Media

Over the past few decades, nanoengineered particles have gained increasing interest for applications in the biomedical realm, including diagnosis, imaging, and therapy. When functionalized with targeting ligands, these particles have the potential to interact with specific cells and tissues, and accumulate at desired target sites, reducing side effects and improve overall efficacy in applications such as vaccination and drug delivery. However, when targeted particles enter a complex biological environment, the adsorption of biomolecules and the formation of a surface coating (e.g., a protein corona) changes the properties of the carriers and can render their behavior unpredictable. For this reason, it is of importance to consider the potential challenges imposed by the biological environment at the early stages of particle design. This review describes parameters that affect the targeting ability of particulate drug carriers, with an emphasis on the effect of the protein corona. We highlight strategies for exploiting the protein corona to improve the targeting ability of particles. Finally, we provide suggestions for complementing current in vitro assays used for the evaluation of targeting and carrier efficacy with new and emerging techniques (e.g., 3D models and flow-based technologies) to advance fundamental understanding in bio-nano science and to accelerate the development of targeted particles for biomedical applications.

Modelling the bronchial barrier in pulmonary drug delivery: A human bronchial epithelial cell line supplemented with human tracheal mucus

The airway epithelium together with the mucus layer coating it forms a protective system that efficiently filters and removes potentially harmful particles contained in inhaled air. The same mechanism, however, serves to entrap particulate drug carriers, precluding their interaction with their target. The mucus barrier is often neglected in in vitro testing setups employed for the assessment of pulmonary drug delivery strategies. Therefore, our aim was to more accurately model the bronchial barrier, by developing an in vitro system comprising a tight epithelial cell layer which may be optionally supplemented with a layer of human tracheal mucus. To form the epithelium in vitro, we used the cystic fibrosis cell line CFBE41o-, which can be grown as monolayers on Transwell® supports, expressing tight junctions as well as relevant transport proteins. In contrast to the cell line Calu-3, however, CFBE41o- does not produce mucus. Therefore, native human mucus, obtained from tracheal tubes of patients undergoing elective surgery, was used as a supplement. The compatibility of CFBE41o- cells with the human mucus was addressed with the MTT assay, and confirmed by fluorescein diacetate/propidium iodide live/dead staining. Moreover, the CFBE41o- cells retained their epithelial barrier properties after being supplemented with mucus, as evidenced by the high trans-epithelial electrical resistance values (∼1000Ωcm2) together with a continued low level of paracellular transport of sodium fluorescein. Fluorescently-labeled chitosan-coated PLGA nanoparticles (NP, ∼168nm) were used as a model drug delivery system to evaluate the suitability of this in vitro model for studying mucus permeation and cell uptake. Comparing CFBE41o- cell monolayers with and without mucus, resp., showed that the NP uptake was dramatically reduced in the presence of mucus. This model may therefore be used as a tool to study potential mucus interactions of aerosolized drugs, and more specifically NP-based drug delivery systems designed to exert their effect in the bronchial region.