Target shape dependence in a simple model of receptor-mediated endocytosis and phagocytosis

Rod and spherical selenium nanoparticles: Physicochemical properties and effects on red blood cells and neutrophils

The influence of selenium (Se) nanoparticles in the form of rods (SeNrs) and spheres (SeSps), synthesized by laser ablation, on the structural and functional properties of human blood erythrocytes and neutrophils was studied for anticancer activity in vitro. SeNrs and SeSps do not have cytotoxicity towards neutrophils and do not cause hemolysis. The elastic modulus and resistance of erythrocytes to HOCl-induced hemolysis increased after binding of Se nanoparticles to the plasma membrane. The interaction of Se nanoparticles with neutrophils is accompanied by their actin-dependent macropinocytosis, triggering intracellular signaling processes leading to the assembly and activation of NADPH oxidase. Comparative analysis of the effects of SeNrs and SeSps on cells showed that they have similar effects. This may be due to the fact that SeNrs interact with the cell surface with their end faces, and, therefore, have the same initial contact with the plasma membrane as SeSps. However, SeSps and SeNrs showed chronic cytotoxicity after 48 h incubation, indicating the need to find ways to reduce their toxicity further. Further use of Se nanoparticles in anisotropic form in biomedical research for the development of therapeutic agents seems promising.

Highly variable aggregation and glycosylation profiles and their roles in immunogenicity to protein-based therapeutics

Production of antibodies against protein-based therapeutics (e.g., monoclonal antibodies (mAbs)) by a recipient's immune system can vary from benign symptoms to chronic neutralization of the compound, and in rare cases, a lethal cytokine storm. One critical factor that can induce or contribute to an anti-drug antibody (ADA) response is believed to be the presence of aggregated proteins in protein-based therapeutics. There is a high level of variability in the aggregation of different proteins, which adds to the complexity in understanding the immune response to these drugs. Furthermore, the level of glycosylation of proteins, which increases drug stability, functionality, and serum half-life, is highly variable and may influence their immunogenicity. Considering the abundance of literature on the effect of aggregation and glycosylation on the immunogenicity of protein-based therapeutics, this review aims to summarize the current knowledge and clarify the immunogenic effects of different protein-based therapeutics such as mAbs. This review focuses on the properties of aggregated proteins and elucidates their relationship with immunogenicity. The contribution of different immune cell subsets and the mechanisms in aggregation-induced immunogenicity are also reviewed. Finally, the potential effects of each glycan, such as sialic acid, mannose, and fucose, on protein-based therapeutics' immunogenicity and stability is discussed.

Why does a cell function? New arguments in favor of quantum effects

In this study, the complexities of intracellular processes have been analyzed, including DNA folding, alternative splicing, mitochondrial function, and enzyme transport in lysosomes. Based on a previously proposed hypothesis (Levinthal's generalized paradox), a conclusion is made that all abovementioned processes cannot be realized with sufficient accuracy and in a realistic timeframe within the framework of classical physics. It is unclear why the cell functions at all. For the cell to function, its internal environment must be highly structured. In this regard, the cell shares similarities with computational devices (computers). In this study, quantum models of interactions between biologically important molecules were constructed, taking into account the long-range effects. One significant aspect of these models is the special role of the phase of the wavefunction, which serves as a controlling parameter. Experiments have been proposed that may confirm or refute these models.

Biomechanics of phagocytosis of red blood cells by macrophages in the human spleen

The clearance of senescent and altered red blood cells (RBCs) in the red pulp of the human spleen involves sequential processes of prefiltration, filtration, and postfiltration. While prior work has elucidated the mechanisms underlying the first two processes, biomechanical processes driving the postfiltration phagocytosis of RBCs retained at interendothelial slits (IES) are still poorly understood. We present here a unique computational model of macrophages to study the role of cell biomechanics in modulating the kinetics of phagocytosis of aged and diseased RBCs retained in the spleen. After validating the macrophage model using in vitro phagocytosis experiments, we employ it to probe the mechanisms underlying the kinetics of phagocytosis of mechanically altered RBCs, such as heated RBCs and abnormal RBCs in hereditary spherocytosis (HS) and sickle cell disease (SCD). Our simulations show pronounced deformation of the flexible and healthy RBCs in contrast to minimal shape changes in altered RBCs. Simulations also show that less deformable RBCs are engulfed faster and at lower adhesive strength than flexible RBCs, consistent with our experimental measurements. This efficient sensing and engulfment by macrophages of stiff RBCs retained at IES are expected to temper splenic congestion, a common pathogenic process in malaria, HS, and SCD. Altogether, our combined computational and in vitro experimental studies suggest that mechanical alterations of retained RBCs may suffice to enhance their phagocytosis, thereby adapting the kinetics of their elimination to the kinetics of their mechanical retention, an equilibrium essential for adequately cleaning the splenic filter to preserve its function.

Intestinal lymphatic transport of Smilax china L. pectic polysaccharide via Peyer's patches and its uptake and transport mechanisms in mononuclear phagocytes

Recently, the intestinal lymphatic transport based on Peyer's patches (PPs) is emerging as a promising absorption pathway for natural polysaccharides. Herein, the aim of this study is to investigate the PP-based oral absorption of a pectic polysaccharide from Smilax china L. (SCLP), as well as its uptake and transport mechanisms in related immune cells. Taking advantages of the traceability of fluorescently labeled SCLP, we confirmed that SCLP could be absorbed into PPs and captured by their mononuclear phagocytes (dendritic cells and macrophages) following oral administration. Subsequently, the systematic in vitro study suggested that the endocytic mechanisms of SCLP by model mononuclear phagocytes (BMDCs and RAW264.7 cells) mainly involved caveolae-mediated endocytosis, macropinocytosis and phagocytosis. More importantly, SCLP directly binds and interacts with toll-like receptor 2 (TLR2) and galectin 3 (Gal-3) receptor, and was taken up by mononuclear phagocytes in receptor-mediated manner. After internalization, SCLP was intracellularly transported primarily through endolysosomal pathway and ultimately localized in lysosomes. In summary, this work reveals novel information and perspectives about the in vivo fate of SCLP, which will contribute to further research and utilization of SCLP and other pectic polysaccharides.

Manipulation of Macrophage Uptake by Controlling the Aspect Ratio of Graft Copolymer Micelles

Nanostructures of drug carriers play a crucial role in nanomedicine due to their ability to influence drug delivery. There is yet no clear consensus regarding the optimal size and shape (e.g., aspect ratio) of nanoparticles for minimizing macrophage uptake, given the difficulties in controlling the shape and size of nanoparticles while maintaining identical surface properties. Here, we employed graft copolymer self-assembly to prepare polymer micelles with aspect ratios ranging from 1.0 (spherical) to 10.8 (cylindrical) and closely matched interfacial properties. Notably, our findings emphasize that cylindrical micelles with an aspect ratio of 2.4 are the least susceptible to macrophage uptake compared with both their longer counterparts and spherical micelles. This reduced uptake of the short cylindrical micelles results in a 3.3-fold increase in blood circulation time compared with their spherical counterparts. Controlling the aspect ratio of nanoparticles is crucial for improving drug delivery efficacy through better nanoparticle design.

Two-component macrophage model for active phagocytosis with pseudopod formation

Macrophage phagocytosis is critical for the immune response, homeostasis regulation, and tissue repair. This intricate process involves complex changes in cell morphology, cytoskeletal reorganization, and various receptor-ligand interactions controlled by mechanical constraints. However, there is a lack of comprehensive theoretical and computational models that investigate the mechanical process of phagocytosis in the context of cytoskeletal rearrangement. To address this issue, we propose a novel coarse-grained mesoscopic model that integrates a fluid-like cell membrane and a cytoskeletal network to study the dynamic phagocytosis process. The growth of actin filaments results in the formation of long and thin pseudopods, and the initial cytoskeleton can be disassembled upon target entry and reconstructed after phagocytosis. Through dynamic changes in the cytoskeleton, our macrophage model achieves active phagocytosis by forming a phagocytic cup utilizing pseudopods in two distinct ways. We have developed a new algorithm for modifying membrane area to prevent membrane rupture and ensure sufficient surface area during phagocytosis. In addition, the bending modulus, shear stiffness, and cortical tension of the macrophage model are investigated through computation of the axial force for the tubular structure and micropipette aspiration. With this model, we simulate active phagocytosis at the cytoskeletal level and investigate the mechanical process during the dynamic interplay between macrophage and target particles.

Allosteric inhibitor of SHP2 enhances macrophage endocytosis and bacteria elimination by increasing caveolae activation and protects against bacterial sepsis

The uncontrolled bacterial infection-induced cytokine storm and sequential immunosuppression are commonly observed in septic patients, which indicates that the activation of phagocytic cells and the efficient and timely elimination of bacteria are crucial for combating bacterial infections. However, the role of dysregulated immune cells and their disrupted function in sepsis remains unclear. Here, we found that macrophages exhibited the impaired endocytosis capabilities in sepsis by Single-cell RNA sequencing and bulk RNA sequencing. Caveolae protein Caveolin-1 (Cav-1) of macrophages was inactivated by SHP2 rapidly during Escherichia coli (E.coli) infection. Allosteric inhibitor of SHP2 effectively maintains Cav-1 phosphorylation to enhance macrophage to endocytose and eliminate bacteria. Additionally, TLR4 endocytosis of macrophage was also enhanced upon E.coli infection by SHP099, inducing an increased and rapidly resolved inflammatory response. In vivo, pretreatment or posttreatment with inhibitor of SHP2 significantly reduced the bacterial burden in organs and mortality of mice subjected E.coli infection or CLP-induced sepsis. The cotreatment of inhibitor of SHP2 with an antibiotic conferred complete protection against mortality in mice. Our findings suggest that Cav-1-mediated endocytosis and bacterial elimination may play a critical role in the pathogenesis of sepsis, highlighting inhibitor of SHP2 as a potential therapeutic agent for sepsis.

Biaxial Structures of Localized Deformations and Line-like Distortions in Effectively 2D Nematic Films

We numerically studied localized elastic distortions in curved, effectively two-dimensional nematic shells. We used a mesoscopic Landau-de Gennes-type approach, in which the orientational order is theoretically considered by introducing the appropriate tensor nematic order parameter, while the three-dimensional shell shape is described by the curvature tensor. We limited our theoretical consideration to axially symmetric shapes of nematic shells. It was shown that in the surface regions of stomatocyte-class nematic shell shapes with large enough magnitudes of extrinsic (deviatoric) curvature, the direction of the in-plane orientational ordering can be mutually perpendicular above and below the narrow neck region. We demonstrate that such line-like nematic distortion configurations may run along the parallels (i.e., along the circular lines of constant latitude) located in the narrow neck regions of stomatocyte-like nematic shells. It was shown that nematic distortions are enabled by the order reconstruction mechanism. We propose that the regions of nematic shells that are strongly elastically deformed, i.e., topological defects and line-like distortions, may attract appropriately surface-decorated nanoparticles (NPs), which could potentially be useful for the controlled assembly of NPs.

Nose-to-brain drug delivery for the treatment of glioblastoma multiforme: nanotechnological interventions

Glioblastoma multiforme (GBM) is the most aggressive malignant brain tumor with a short survival rate. Extensive research is underway for the last two decades to find an effective treatment for GBM but the tortuous pathophysiology, development of chemoresistance, and presence of BBB are the major challenges, prompting scientists to look for alternative targets and delivery strategies. Therefore, the nose to brain delivery emerged as an unorthodox and non-invasive route, which delivers the drug directly to the brain via the olfactory and trigeminal pathways and also bypasses the BBB and hepatic metabolism of the drug. However, mucociliary clearance, low administration volume, and less permeability of nasal mucosa are the obstacles retrenching the brain drug concentration. Thus, nanocarrier delivery through this route may conquer these limitations because of their unique surface characteristics and smaller size. In this review, we have emphasized the advantages and limitations of nanocarrier technologies such as polymeric, lipidic, inorganic, and miscellaneous nanoparticles used for nose-to-brain drug delivery against GBM in the past 10 years. Furthermore, recent advances, patents, and clinical trials are highlighted. However, most of these studies are in the early stages, so translating their outcomes into a marketed formulation would be a milestone in the better progression and survival of glioma patients.

Effects of receptor properties on particle internalization through receptor-mediated endocytosis

Receptor-mediated endocytosis (RME) is a highly complex process carried out by bioparticles, such as viruses and drug carriers, to enter cells. The discovery of both clathrin-dependent and clathrin-free pathways makes the RME process even more intriguing. Numerical models have been developed to facilitate the exploration of the process. However, the impacts of the receptor properties on RME have been less studied partially due to the oversimplifications of the receptor models. In this paper, we implement a stochastic model to systematically investigate the effects of mechanical (receptor flexure), geometrical (receptor length) and biochemical (ligand-receptor cutoff) properties of receptors, on RME with and without the existence of clathrin. Our simulation results show that the receptor's flexural rigidity plays an important role in RME with clathrin. There is a threshold beyond which particle internalization will not occur. Without clathrin, it is very difficult to achieve complete endocytosis with ligand-receptor interactions alone. A shorter receptor length and longer ligand-receptor reaction cutoff promote the formation of ligand-receptor bonds and facilitate particle internalization. Complete internalization can only be obtained with an extremely short receptor length and long reaction cutoff. Therefore, there are most likely some additional mechanisms to drive the membrane deformation in clathrin-free RME. Our results yield important fundamental insights into RME and provide crucial guidance when correlating the simulation results with experimental observations.

Wrapping Pathways of Anisotropic Dumbbell Particles by Giant Unilamellar Vesicles

Endocytosis is a key cellular process involved in the uptake of nutrients, pathogens, or the therapy of diseases. Most studies have focused on spherical objects, whereas biologically relevant shapes can be highly anisotropic. In this letter, we use an experimental model system based on Giant Unilamellar Vesicles (GUVs) and dumbbell-shaped colloidal particles to mimic and investigate the first stage of the passive endocytic process: engulfment of an anisotropic object by the membrane. Our model has specific ligand-receptor interactions realized by mobile receptors on the vesicles and immobile ligands on the particles. Through a series of experiments, theory, and molecular dynamics simulations, we quantify the wrapping process of anisotropic dumbbells by GUVs and identify distinct stages of the wrapping pathway. We find that the strong curvature variation in the neck of the dumbbell as well as membrane tension are crucial in determining both the speed of wrapping and the final states.

The spatial resolution limit of phagocytosis

Antibody-opsonized bacteria interact with Fc receptors in macrophages and trigger signaling cascades, which induce phagocytosis. The signaling pathways ultimately lead to actin polymerization that induces the protrusion of the membrane around the bacterium until it is completely engulfed. Although many proteins involved in the phagocytic cup formation have already been identified, it is still unclear how far the initial stimulus created by the bacterium-cell contact propagates in the cell. We hypothesize that this spreading distance is closely related to the spatial resolution limit of phagocytosis, the smallest distance in which two stimuli can be differentiated. Here, we probe this resolution limit by using holographic optical tweezers to attach pairs of immunoglobulin G-coated polystyrene microparticles (as models for opsonized bacteria) to murine macrophages in distances ranging from zero to several micrometers. By using 2-μm-sized particles, we found that the particles can be internalized jointly into one phagosome if they are attached to the cell very close together, but that they are taken up separately if they are attached far from each other. To explain this, we developed a model of the signaling process, which predicts the probabilities for separate uptake for different particle sizes and distances using cellular parameters including the average receptor distance. We tested the model by measuring the separate uptake probabilities for particles with a diameter of 1 to 3 μm and for cells with reduced numbers of Fcγ receptors and found very good agreement. Our model shows that the phagocytic uptake behavior can be explained by assuming an effective phagocytic signaling range of about 500 nm. Interestingly, this value corresponds to the lower size limit of phagocytosis. Our work provides quantitative access to spatial parameters of cellular signaling during phagocytosis and thereby contributes to a more quantitative understanding of cellular information processing.

Microfluidic study of retention and elimination of abnormal red blood cells by human spleen with implications for sickle cell disease

The spleen clears altered red blood cells (RBCs) from circulation, contributing to the balance between RBC formation (erythropoiesis) and removal. The splenic RBC retention and elimination occur predominantly in open circulation where RBCs flow through macrophages and inter-endothelial slits (IESs). The mechanisms underlying and interconnecting these processes significantly impact clinical outcomes. In sickle cell disease (SCD), blockage of intrasplenic sickled RBCs is observed in infants splenectomized due to acute splenic sequestration crisis (ASSC). This life-threatening RBC pooling and organ swelling event is plausibly triggered or enhanced by intra-tissular hypoxia. We present an oxygen-mediated spleen-on-a-chip platform for in vitro investigations of the homeostatic balance in the spleen. To demonstrate and validate the benefits of this general microfluidic platform, we focus on SCD and study the effects of hypoxia on splenic RBC retention and elimination. We observe that RBC retention by IESs and RBC-macrophage adhesion are faster in blood samples from SCD patients than those from healthy subjects. This difference is markedly exacerbated under hypoxia. Moreover, the sickled RBCs under hypoxia show distinctly different phagocytosis processes from those non-sickled RBCs under hypoxia or normoxia. We find that reoxygenation significantly alleviates RBC retention at IESs, and leads to rapid unsickling and fragmentation of the ingested sickled RBCs inside macrophages. These results provide unique mechanistic insights into how the spleen maintains its homeostatic balance between splenic RBC retention and elimination, and shed light on how disruptions in this balance could lead to anemia, splenomegaly, and ASSC in SCD and possible clinical manifestations in other hematologic diseases.

A theoretical model of efficient phagocytosis driven by curved membrane proteins and active cytoskeleton forces

Phagocytosis is the process of engulfment and internalization of comparatively large particles by cells, and plays a central role in the functioning of our immune system. We study the process of phagocytosis by considering a simplified coarse grained model of a three-dimensional vesicle, having a uniform adhesion interaction with a rigid particle, and containing curved membrane-bound protein complexes or curved membrane nano-domains, which in turn recruit active cytoskeletal forces. Complete engulfment is achieved when the bending energy cost of the vesicle is balanced by the gain in the adhesion energy. The presence of curved (convex) proteins reduces the bending energy cost by self-organizing with a higher density at the highly curved leading edge of the engulfing membrane, which forms the circular rim of the phagocytic cup that wraps around the particle. This allows the engulfment to occur at much smaller adhesion strength. When the curved membrane-bound protein complexes locally recruit actin polymerization machinery, which leads to outward forces being exerted on the membrane, we found that engulfment is achieved more quickly and at a lower protein density. We consider spherical and non-spherical particles and found that non-spherical particles are more difficult to engulf in comparison to the spherical particles of the same surface area. For non-spherical particles, the engulfment time crucially depends on the initial orientation of the particles with respect to the vesicle. Our model offers a mechanism for the spontaneous self-organization of the actin cytoskeleton at the phagocytic cup, in good agreement with recent high-resolution experimental observations.

Role of particle local curvature in cellular wrapping

Cellular uptake through membranes plays an important role in adsorbing nutrients and fighting infection and can be used for nanomedicine developments. Endocytosis is one of the pathways of cellular uptake which associate with elastic deformation of the membrane wrapping around the foreign particle. The deformability of the membrane is strongly regulated by the presence of a cortical cytoskeleton placed underneath the membrane. It is shown that shape and orientation of the particles influence on their internalization. Here, we study the role of particle local curvature in cellular uptake by investigating the wrapping of an elastic membrane around a long cylindrical object with an elliptical cross-section. The membrane itself is adhered to a substrate mimicking the cytoskeleton. Membrane wrapping proceeds differently whether the initial contact occurs at the target's highly curved part (vertical) or along its long side (horizontal). We obtain a wrapping phase diagram as a function of the membrane-cytoskeleton and the membrane-target adhesion energy, which includes three distinct regimes (unwrapped, partially wrapped and fully wrapped), separated by two phase transitions. We also provide analytical expressions for the boundaries between the different regimes which confirm that the transitions strongly depend on the orientation and aspect ratio of the nanowire.

Integrative experimental/computational approach establishes active cellular protrusion as the primary driving force of phagocytic spreading by immune cells

The dynamic interplay between cell adhesion and protrusion is a critical determinant of many forms of cell motility. When modeling cell spreading on adhesive surfaces, traditional mathematical treatments often consider passive cell adhesion as the primary, if not exclusive, mechanistic driving force of this cellular motion. To better assess the contribution of active cytoskeletal protrusion to immune-cell spreading during phagocytosis, we here develop a computational framework that allows us to optionally investigate both purely adhesive spreading ("Brownian zipper hypothesis") as well as protrusion-dominated spreading ("protrusive zipper hypothesis"). We model the cell as an axisymmetric body of highly viscous fluid surrounded by a cortex with uniform surface tension and incorporate as potential driving forces of cell spreading an attractive stress due to receptor-ligand binding and an outward normal stress representing cytoskeletal protrusion, both acting on the cell boundary. We leverage various model predictions against the results of a directly related experimental companion study of human neutrophil phagocytic spreading on substrates coated with different densities of antibodies. We find that the concept of adhesion-driven spreading is incompatible with experimental results such as the independence of the cell-spreading speed on the density of immobilized antibodies. In contrast, the protrusive zipper model agrees well with experimental findings and, when adapted to simulate cell spreading on discrete adhesion sites, it also reproduces the observed positive correlation between antibody density and maximum cell-substrate contact area. Together, our integrative experimental/computational approach shows that phagocytic spreading is driven by cellular protrusion, and that the extent of spreading is limited by the density of adhesion sites.

Study of tribological properties of human buccal epithelium cell membranes using probe microscopy

In this work demostrates a unique method for determining the absolute value of the friction force of a nanoobject on the surface of a cell membrane using atomic force microscopy. The tribological properties of membranes of adult human buccal epithelium cells in the presence of a protective adsorption buffer layer of ~ 100 nm on their surface were studied using atomic force microscopy in the contact scanning mode. Local mapping of the tribological characteristics of the surface was carried out, viz. friction F_L = F_L(x, y) and adhesion F_adh = F_adh(x, y) forces were measured. Studies of the friction force F_fr on the membrane surface at the nanolevel showed that its value varies discretely with an interval equal to l_LF ≈ 100 nm. It was shown that such discreteness is determined by the interval l_LF of the action of adhesive forces F_adh and indicates the fractal nature of the functional dependence of the friction force on the coordinate F_fr = F_fr(x). Thus, for nano-objects with dimensions ≤ l_LF, the absolute value of F_fr decreases according to a power law with an increase in the size of the object, which contradicts the similar dependence of the friction force for macro-objects in the global approximation.

Understanding the Phagocytosis of Particles: the Key for Rational Design of Vaccines and Therapeutics

A robust comprehension of phagocytosis is crucial for understanding its importance in innate immunity. A detailed description of the molecular mechanisms that lead to the uptake and clearance of endogenous and exogenous particles has helped elucidate the role of phagocytosis in health and infectious or autoimmune diseases. Furthermore, knowledge about this cellular process is important for the rational design and development of particulate systems for the administration of vaccines or therapeutics. Depending on these specific applications and the required biological responses, particles must be designed to encourage or avoid their phagocytosis and prolong their circulation time. Functionalization with specific polymers or ligands and changes in the size, shape, or surface of particles have important effects on their recognition and internalization by professional and nonprofessional phagocytes and have a major influence on their fate and safety. Here, we review the phagocytosis of particles intended to be used as carrier or delivery systems for vaccines or therapeutics, the cells involved in this process depending on the route of administration, and the strategies employed to obtain the most desirable particles for each application through the manipulation of their physicochemical characteristics. We also offer a view of the challenges and potential opportunities in the field and give some recommendations that we expect will enable the development of improved approaches for the rational design of these systems.

A near-infrared plasma membrane-specific AIE probe for fluorescence lifetime imaging of phagocytosis

Phagocytosis is a biological process that plays a key role in host defense and tissue homeostasis. Efficient approaches for realtime imaging of phagocytosis are highly desired but limited. Herein, an AIE-active near-infrared fluorescent probe, named TBTCP, was developed for fluorescence lifetime imaging of phagocytosis. TBTCP could selectively label the cell plasma membrane with fast staining, wash-free process, high signal-to-background ratio, and excellent photostability. Cellular membrane statuses under different osmolarities as well as macrophage phagocytosis of bacteria or large silica particles in early stages could be reported by the fluorescence lifetime changes of TBTCP. Compared with current fluorescence imaging methods, which target the bioenvironmental changes in the late phagocytosis stage, this approach detects the changes in the cell membrane, thus giving a faster response to phagocytosis. This article provides a functional tool to report the phagocytic dynamics of macrophages which may greatly contribute to the studies of phagocytic function-related diseases.

Enantiomer-dependent immunological response to chiral nanoparticles

Chirality is a unifying structural metric of biological and abiological forms of matter. Over the past decade, considerable clarity has been achieved in understanding the chemistry and physics of chiral inorganic nanoparticles^1-4; however, little is known about their effects on complex biochemical networks^5,6. Intermolecular interactions of biological molecules and inorganic nanoparticles show some commonalities^7-9, but these structures differ in scale, in geometry and in the dynamics of chiral shapes, which can both impede and strengthen their mirror-asymmetric complexes. Here we show that achiral and left- and right-handed gold biomimetic nanoparticles show different in vitro and in vivo immune responses. We use irradiation with circularly polarized light (CPL) to synthesize nanoparticles with controllable nanometre-scale chirality and optical anisotropy factors (g-factors) of up to 0.4. We find that binding of nanoparticles to two proteins from the family of adhesion G-protein-coupled receptors (AGPCRs)-namely cluster-of-differentiation 97 (CD97) and epidermal-growth-factor-like-module receptor 1 (EMR1)-results in the opening of mechanosensitive potassium-efflux channels, the production of immune signalling complexes known as inflammasomes, and the maturation of mouse bone-marrow-derived dendritic cells. Both in vivo and in vitro immune responses depend monotonically on the g-factors of the nanoparticles, indicating that nanoscale chirality can be used to regulate the maturation of immune cells. Finally, left-handed nanoparticles show substantially higher (1,258-fold) efficiency compared with their right-handed counterparts as adjuvants for vaccination against the H9N2 influenza virus, opening a path to the use of nanoscale chirality in immunology.

Peter L, Chan C, Mikhailova T, Bexheti V, Kapadia A, Carbery WP, Ng K, Maity P. Microfluidic-Supported Synthesis of Anisotropic Polyvinyl Methacrylate Nanoparticles via Interfacial Agents

For polymer particles, recent studies emphasized that the particle shape—not size—plays the dominant role in novel applications in fields ranging from nanotechnology, biomedicine, to photonics, which has intensified the quest...

Tuning cellular uptake of nanoparticles via ligand density: Contribution of configurational entropy

The bioactivity of nanoparticles (NPs) crucially depends on their ability to cross biological membranes. A fundamental understanding of cell-NP interaction is hence essential to improve the performance of the NP-based biomedical applications. Although extensive studies of cellular uptake have converged upon the idea that the uptake process is mainly regulated by the elastic deformation of the cell membrane or NP, recent experimental observations indicate the ligand density as another critical factor in modulating NP uptake into cells. In this study, we propose a theoretical model of the wrapping of an elastic vesicle NP by a finite lipid membrane to depict the relevant energetic and morphological evolutions during the wrapping process driven by forming receptor-ligand bonds. In this model, the deformations of the membrane and the vesicle NP are assumed to follow the continuum Canham-Helfrich framework, whereas the change of configurational entropy of receptors is described from statistical thermodynamics. Results show that the ligand density strongly affects the binding energy and configurational entropy of free receptors, thereby altering the morphology of the vesicle-membrane system in the steady wrapping state. For the wrapping process by the finite lipid membrane, we also find that there exists optimal ligand density for the maximum wrapping degree. These predictions are consistent with relevant experimental observations reported in the literature. We have further observed that there are transitions of various wrapping phases (no wrapping, partial wrapping, and full wrapping) in terms of ligand density, membrane tension, and molecular binding energy. In particular, the ligand and receptor shortage regimes for the small and high ligand density are, respectively, identified. These results may provide guidelines for the rational design of nanocarriers for drug delivery.

Crystal-chemical and morphological interpretation of the biocompatibility of compounds in a Ca-Na-Bi-fluorapatite system

This work is devoted to the study of the features of isomorphism in compounds of a Ca-Na-Bi-P-O-F system with a crystalline structure of the mineral apatite, as well as its effect on the biocompatibility of substances in relation to human cells in an in vitro model. A Ca_10-2xBi_xNa_x(PO₄)₆F₂ system (x = 0, 1, 2, 3, 4, and 5) is characterized by continuous isomorphism, which follows from the minimum deviations of the unit cell parameters from the Vegard and Rötgers rules. The refinement of the crystal structure showed that the cations are unevenly distributed between the 4f and 6h positions of the crystal structure of apatite: the bismuth ions are predominantly localized in the 6h position, while the sodium ions are concentrated in the 4f position. A standard MTT test of the biocompatibility of compounds with x = 1, 2, 3, and 4, and at x = 1 showed an anomaly in the form of an increased relative cell growth rate. This paper discusses the possible crystal-chemical and morphological reasons for this phenomenon.

Role of Ligand Distribution in the Cytoskeleton-Associated Endocytosis of Ellipsoidal Nanoparticles

Nanoparticle (NP)–cell interaction mediated by receptor–ligand bonds is a crucial phenomenon in pathology, cellular immunity, and drug delivery systems, and relies strongly on the shape of NPs and the stiffness of the cell. Given this significance, a fundamental question is raised on how the ligand distribution may affect the membrane wrapping of non-spherical NPs under the influence of cytoskeleton deformation. To address this issue, in this work we use a coupled elasticity–diffusion model to systematically investigate the role of ligand distribution in the cytoskeleton-associated endocytosis of ellipsoidal NPs for different NP shapes, sizes, cytoskeleton stiffness, and the initial receptor densities. In this model, we have taken into account the effects of receptor diffusion, receptor–ligand binding, cytoskeleton and membrane deformations, and changes in the configuration entropy of receptors. By solving this model, we find that the uptake process can be significantly influenced by the ligand distribution. Additionally, there exists an optimal state of such a distribution, which corresponds to the fastest uptake efficiency and depends on the NP aspect ratio and cytoskeleton stiffness. We also find that the optimal distribution usually needs local ligand density to be sufficiently high at the large curvature region. Furthermore, the optimal state of NP entry into cells can tolerate slight changes to the corresponding optimal distribution of the ligands. The tolerance to such a change is enhanced as the average receptor density and NP size increase. These results may provide guidelines to control NP–cell interactions and improve the efficiency of target drug delivery systems.

Mechanotransduction as a major driver of cell behaviour: mechanisms, and relevance to cell organization and future research

How do cells process environmental cues to make decisions? This simple question is still generating much experimental and theoretical work, at the border of physics, chemistry and biology, with strong implications in medicine. The purpose of mechanobiology is to understand how biochemical and physical cues are turned into signals through mechanotransduction. Here, we review recent evidence showing that (i) mechanotransduction plays a major role in triggering signalling cascades following cell-neighbourhood interaction; (ii) the cell capacity to continually generate forces, and biomolecule properties to undergo conformational changes in response to piconewton forces, provide a molecular basis for understanding mechanotransduction; and (iii) mechanotransduction shapes the guidance cues retrieved by living cells and the information flow they generate. This includes the temporal and spatial properties of intracellular signalling cascades. In conclusion, it is suggested that the described concepts may provide guidelines to define experimentally accessible parameters to describe cell structure and dynamics, as a prerequisite to take advantage of recent progress in high-throughput data gathering, computer simulation and artificial intelligence, in order to build a workable, hopefully predictive, account of cell signalling networks.

Role of proteins in the biosynthesis and functioning of metallic nanoparticles

Proteins are known to play important roles in the biosynthesis of metallic nanoparticles (NPs), which are biological substitutes for conventionally used chemical capping and stabilizing agents. When a pristine nanoparticle comes in contact with a biological media or system, a bimolecular layer is formed on the surface of the nanoparticle and is primarily composed of proteins. The role of proteins in the biosynthesis and further uptake, translocation, and bio-recognition of nanoparticles is documented in the literature. But, a complete understanding has not been achieved concerning the mechanism for protein-mediated nanoparticle biosynthesis and the role proteins play in the interaction and recognition of nanoparticles, aiding its uptake and assimilation into the biological system. This review critically evaluates the knowledge and gaps in the protein-mediated biosynthesis of nanoparticles. In particular, we review the role of proteins in multiple facets of metallic nanoparticle biosynthesis, the interaction of proteins with metallic nanoparticles for recognition and interaction with cells, and the toxic potential of protein-nanoparticle complexes when presented to the cell.

Nanocellulose Length Determines the Differential Cytotoxic Effects and Inflammatory Responses in Macrophages and Hepatocytes

Nanocellulose including cellulose nanocrystal (CNC) and cellulose nanofiber (CNF) has attracted much attention due to its exceptional mechanical, chemical, and rheological properties. Although considered biocompatible, recent reports have demonstrated nanocellulose can be hazardous, including serving as drug carriers that accumulate in the liver. However, the nanocellulose effects on liver cells, including Kupffer cells (KCs) and hepatocytes are unclear. Here, the toxicity of nanocellulose with different lengths is compared, including the shorter CNCs (CNC-1, CNC-2, and CNC-3) and longer CNF (CNF-1 and CNF-2), to liver cells. While all CNCs triggered significant cytotoxicity in KCs and only CNC-2 induced toxicity to hepatocytes, CNFs failed to induce significant cytotoxicity due to their minimal cellular uptake. The phagocytosis of CNCs by KCs induced mitochondria ROS generation, caspase-3/7 activation, and apoptotic cell death as well as lysosomal damage, cathepsin B release, NLRP3 inflammasome and caspase-1 activation, and IL-1β production. The cellular uptake of CNC-2 by hepatocytes is through clathrin-mediated endocytosis, and it induced the caspase-3/7-mediated apoptosis. CNC-2 shows the highest levels of uptake and cytotoxicity among CNCs. These results demonstrate the length-dependent mechanisms of toxicity on liver cells in a cell type-dependent fashion, providing information to safely use nanocellulose for biomedical applications.

Apoptotic cell signals and heterogeneity in macrophage function: Fine-tuning for a healthy liver

Functional heterogeneity in tissue macrophage populations has often been traced to developmental and spatial cues. Upon tissue damage, macrophages are exposed to soluble mediators secreted by activated cells, which shape their polarisation. Interestingly, macrophages are concomitantly exposed to a variety of different dying cells, which carry miscellaneous signals and that need to be recognised and promptly up-taken by professional phagocytes. This review discusses how differences in the nature of the dying cells, like their morphological and biochemical features as well as the specificity of phagocytic receptor usage on macrophages, might contribute to the transcriptional and functional heterogeneity observed in phagocytic cells in the tissue.

DNA-Based Microparticle Tension Sensors (μTS) for Measuring Cell Mechanics in Non-planar Geometries and for High-Throughput Quantification

Mechanotransduction, the interplay between physical and chemical signaling, plays vital roles in many biological processes. The state-of-the-art techniques to quantify cell forces employ deformable polymer films or molecular probes tethered to glass substrates. However, the applications of these assays in fundamental and clinical research are restricted by the planar geometry and low throughput of microscopy readout. Herein, we develop a DNA-based microparticle tension sensor, which features a spherical surface and thus allows for investigation of mechanotransduction at curved interfaces. The micron-scale of μTS enables flow cytometry readout, which is rapid and high throughput. We applied the method to map and measure T-cell receptor forces and platelet integrin forces at 12 and 56 pN thresholds. Furthermore, we quantified the inhibition efficiency of two anti-platelet drugs providing a proof-of-concept demonstration of μTS to screen drugs that modulate cellular mechanics.

Understanding nano-engineered particle-cell interactions: biological insights from mathematical models

Understanding the interactions between nano-engineered particles and cells is necessary for the rational design of particles for therapeutic, diagnostic and imaging purposes. In particular, the informed design of particles relies on the quantification of the relationship between the physicochemical properties of the particles and the rate at which cells interact with, and subsequently internalise, particles. Quantitative models, both mathematical and computational, provide a powerful tool for elucidating this relationship, as well as for understanding the mechanisms governing the intertwined processes of interaction and internalisation. Here we review the different types of mathematical and computational models that have been used to examine particle-cell interactions and particle internalisation. We detail the mathematical methodology for each type of model, the benefits and limitations associated with the different types of models, and highlight the advances in understanding gleaned from the application of these models to experimental observations of particle internalisation. We discuss the recent proposal and ongoing community adoption of standardised experimental reporting, and how this adoption is an important step toward unlocking the full potential of modelling approaches. Finally, we consider future directions in quantitative models of particle-cell interactions and highlight the need for hybrid experimental and theoretical investigations to address hitherto unanswered questions.

More than just a barrier: using physical models to couple membrane shape to cell function

The correct execution of many cellular processes, such as division and motility, requires the cell to adopt a specific shape. Physically, these shapes are determined by the interplay of the plasma membrane and internal cellular driving factors. While the plasma membrane defines the boundary of the cell, processes inside the cell can result in the generation of forces that deform the membrane. These processes include protein binding, the assembly of protein superstructures, and the growth and contraction of cytoskeletal networks. Due to the complexity of the cell, relating observed membrane deformations back to internal processes is a challenging problem. Here, we review cell shape changes in endocytosis, cell adhesion, cell migration and cell division and discuss how by modeling membrane deformations we can investigate the inner working principles of the cell.

Modulation of Immune Responses by Particle Size and Shape

The immune system has to cope with a wide range of irregularly shaped pathogens that can actively move (e.g., by flagella) and also dynamically remodel their shape (e.g., transition from yeast-shaped to hyphal fungi). The goal of this review is to draw general conclusions of how the size and geometry of a pathogen affect its uptake and processing by phagocytes of the immune system. We compared both theoretical and experimental studies with different cells, model particles, and pathogenic microbes (particularly fungi) showing that particle size, shape, rigidity, and surface roughness are important parameters for cellular uptake and subsequent immune responses, particularly inflammasome activation and T cell activation. Understanding how the physical properties of particles affect immune responses can aid the design of better vaccines.

Emerging Structural and Interfacial Features of Particulate Polymers at the Nanoscale

Particulate polymers at the nanoscale are exceedingly promising for diversified functional applications ranging from biomedical and energy to sensing, labeling, and catalysis. Tailored structural features (i.e., size, shape, morphology, internal softness, interior cross-linking, etc.) determine polymer nanoparticles' impact on the cargo loading capacity and controlled/sustained release, possibility of endocytosis, degradability, and photostability. The designed interfacial features, however (i.e., stimuli-responsive surfaces, wrinkling, surface porosity, shell-layer swellability, layer-by-layer surface functionalization, surface charge, etc.), regulate nanoparticles' interfacial interactions, controlled assembly, movement and collision, and compatibility with the surroundings (e.g., solvent and biological environments). These features define nanoparticles' overall properties/functions on the basis of homogeneity, stability, interfacial tension, and minimization of the surface energy barrier. Lowering of the resultant outcomes is directly influenced by inhomogeneity in the structural and interfacial design through the structure-function relationship. Therefore, a key requirement is to produce well-defined polymer nanoparticles with controlled characteristics. Polymers are amorphous, flexible, and soft, and hence controlling their structural/interfacial features through the single-step process is a challenge. The microfluidics reaction strategy is very promising because of its wide range of advantages such as efficient reactant mixing and fast phase transfer. Overall, this feature article highlights the state-of-the-art synthetic features of polymer nanoparticles with perspectives on their advanced applications.

Receptor Models of Phagocytosis: The Effect of Target Shape

Phagocytosis is a remarkably complex process, requiring simultaneous organisation of the cell membrane, the cytoskeleton, receptors and various signalling molecules. As can often be the case, mathematical modelling is able to penetrate some of this complexity, identifying the key biophysical components and generating understanding that would take far longer with a purely experimental approach. This chapter will review a particularly important class of phagocytosis model, championed in recent years, that primarily focuses on the role of receptors during the engulfment process. These models are pertinent to a host of unsolved questions in the subject, including the rate of cup growth during uptake, the role of both intra- and extracellular noise, and the precise differences between phagocytosis and other forms of endocytosis. In particular, this chapter will focus on the effect of target shape and orientation, including how these influence the rate and final outcome of phagocytic engulfment.

Engulfment of ellipsoidal nanoparticles by membranes: full description of orientational changes

We study the engulfment of ellipsoidal nanoparticles by membranes. It has been previously predicted that wrapping by the membrane can induce reorientation of the particle, however, previous studies only considered the wrapping process constrained to either side-oriented or tip-oriented particles. In contrast, we consider here the full two-dimensional energy landscape for engulfment, where the two degrees of freedom represent (i) the amount of wrapping and (ii) the particle orientation. In this way, we obtain access to the stability limits of the differently-oriented states, as well as to the energy barriers between them. We find that prolate and oblate particles undergo qualitatively different engulfment transitions, and show that the initial orientation of the particle at first contact with the membrane influences its fate.

Physical Constraints and Forces Involved in Phagocytosis

Phagocytosis is a specialized process that enables cellular ingestion and clearance of microbes, dead cells and tissue debris that are too large for other endocytic routes. As such, it is an essential component of tissue homeostasis and the innate immune response, and also provides a link to the adaptive immune response. However, ingestion of large particulate materials represents a monumental task for phagocytic cells. It requires profound reorganization of the cell morphology around the target in a controlled manner, which is limited by biophysical constraints. Experimental and theoretical studies have identified critical aspects associated with the interconnected biophysical properties of the receptors, the membrane, and the actin cytoskeleton that can determine the success of large particle internalization. In this review, we will discuss the major physical constraints involved in the formation of a phagosome. Focusing on two of the most-studied types of phagocytic receptors, the Fcγ receptors and the complement receptor 3 (αMβ2 integrin), we will describe the complex molecular mechanisms employed by phagocytes to overcome these physical constraints.

Isolating the sources of heterogeneity in nano-engineered particle-cell interactions

Nano-engineered particles have the potential to enhance therapeutic success and reduce toxicity-based treatment side effects via the targeted delivery of drugs to cells. This delivery relies on complex interactions between numerous biological, chemical and physical processes. The intertwined nature of these processes has thus far hindered attempts to understand their individual impact. Variation in experimental data, such as the number of particles inside each cell, further inhibits understanding. Here, we present a mathematical framework that is capable of examining the impact of individual processes during particle delivery. We demonstrate that variation in experimental particle uptake data can be explained by three factors: random particle motion; variation in particle-cell interactions; and variation in the maximum particle uptake per cell. Without all three factors, the experimental data cannot be explained. This work provides insight into biological mechanisms that cause heterogeneous responses to treatment, and enables precise identification of treatment-resistant cell subpopulations.

Nanomaterials and Innate Immunity: A Perspective of the Current Status in Nanosafety

Human exposure to engineered nanomaterials (ENMs) is inevitable due to the plethora of applications for which they are being manufactured and integrated within. ENMs demonstrate plentiful advantages in terms of industrial approaches as well as from a consumer perspective. However, despite such positives, doubts remain over the human health implications of ENM exposure. In light of the increased research focus upon the potential effects of ENM exposure to human health in recent decades, questions still remain regarding the safety of these highly advanced, precision-tuned physical entities. The risk of short-term, high-dose exposure to humans is considered relatively low, although this has formed the direction of the hazard-assessment community since the turn of the 21st century. However, the possibility of humans being exposed repeatedly over a long period of time to a low-dose of ENMs of varying physicochemical characteristics is of significant concern, and thus, industry, government, academic, and consumer agencies are only now beginning to consider this. Notably, when considering the human health implications of such low-dose, long-term, repeated exposure scenarios, the impact of ENMs upon the human immune system is of primary importance. However, there remains a real need to understand the impact of ENMs upon the human immune system, especially the innate immune system, at all stages of life, given exposure to nanosized particles begins before birth, that is, of the fetus. Therefore, the purpose of this perspective is to summarize what is currently known regarding ENM exposure of different components of the innate immune system and identify knowledge gaps that should be addressed if we are to fully deduce the impact of ENM exposure on innate immune function.

Nanoparticle Drug Delivery System for Glioma and Its Efficacy Improvement Strategies: A Comprehensive Review

Gliomas are the most common tumor of the central nervous system. However, the presence of the brain barrier blocks the effective delivery of drugs and leads to the treatment failure of various drugs. The development of a nanoparticle drug delivery system (NDDS) can solve this problem. In this review, we summarized the brain barrier (including blood-brain barrier (BBB), blood-brain tumor barriers (BBTB), brain-cerebrospinal fluid barrier (BCB), and nose-to-brain barrier), NDDS of glioma (such as passive targeting systems, active targeting systems, and environmental responsive targeting systems), and NDDS efficacy improvement strategies and deficiencies. The research prospect of drug-targeted delivery systems for glioma is also discussed.

Protein corona impact on nanoparticle-cell interactions: toward an energy-based model of endocytosis

Upon incubation of nanoparticles in biological fluids, a new layer called the protein corona is formed on their surface affecting the interactions between nanoparticles and targeted cells during the endocytosis process. In the present study, a mathematical model based on the diffusion of membrane mobile receptors is proposed. Opposing the endocytosis proceeding, membrane bending and tension energies are named as resistant energy. Also, the binding energy and free-energy associated with the configurational entropy are collectively termed promoter energy. Utilizing this model, endocytosis of gold nanoparticle (GNP) is simulated to explore the biological media effect. The results reveal that there exists a nanoparticle size of 60 nm at which, the endocytosis time is at a minimum. It has been illustrated that, although for sufficiently small particles of diameter 30nm, membrane tension has a negligible contribution (<10%) in the resistant energy, it noticeably increases the endocytosis processing time for large particles. Therefore, we report several parametric studies to provide a better insight into the effects of biological media on the ingestion of nanoparticles. Through a detailed analysis of the engulfment of the nanoparticles, it is shown that the nanoparticle radius corresponding to the quickest possible ingestion time is affected in the presence of corona. Moreover, it is found that the formation of this layer does not only affect the endocytosis time but also can lead to incomplete engulfment by decreasing the ligand density on the nanoparticle surface. Use of the proposed model can play a significant role in advancing the design of nanoparticles in targeted drug delivery applications.

Physical Constraints and Forces Involved in Phagocytosis

Phagocytosis is a specialized process that enables cellular ingestion and clearance of microbes, dead cells and tissue debris that are too large for other endocytic routes. As such, it is an essential component of tissue homeostasis and the innate immune response, and also provides a link to the adaptive immune response. However, ingestion of large particulate materials represents a monumental task for phagocytic cells. It requires profound reorganization of the cell morphology around the target in a controlled manner, which is limited by biophysical constraints. Experimental and theoretical studies have identified critical aspects associated with the interconnected biophysical properties of the receptors, the membrane, and the actin cytoskeleton that can determine the success of large particle internalization. In this review, we will discuss the major physical constraints involved in the formation of a phagosome. Focusing on two of the most-studied types of phagocytic receptors, the Fcγ receptors and the complement receptor 3 (αMβ2 integrin), we will describe the complex molecular mechanisms employed by phagocytes to overcome these physical constraints.

Efficient nanocarriers of siRNA therapeutics for cancer treatment

Nanocarriers as drug delivery systems are promising and becoming popular, especially for cancer treatment. In addition to improving the pharmacokinetics of poorly soluble hydrophobic drugs by solubilizing them in a hydrophobic core, nanocarriers allow cancer-specific combination drug deliveries by inherent passive targeting phenomena and adoption of active targeting strategies. Nanoparticle-drug formulations can enhance the safety, pharmacokinetic profiles, and bioavailability of locally or systemically administered drugs, leading to improved therapeutic efficacy. Gene silencing by RNA interference (RNAi) is rapidly developing as a personalized field of cancer treatment. Small interfering RNAs (siRNAs) can be used to switch off specific cancer genes, in effect, "silence the gene, silence the cancer." siRNA can be used to silence specific genes that produce harmful or abnormal proteins. The activity of siRNA can be used to harness cellular machinery to destroy a corresponding sequence of mRNA that encodes a disease-causing protein. At present, the main barrier to implementing siRNA therapies in clinical practice is the lack of an effective delivery system that protects the siRNA from nuclease degradation, delivers to it to cancer cells, and releases it into the cytoplasm of targeted cancer cells, without creating adverse effects. This review provides an overview of various nanocarrier formulations in both research and clinical applications with a focus on combinations of siRNA and chemotherapeutic drug delivery systems for the treatment of multidrug resistant cancer. The use of various nanoparticles for siRNA-drug delivery, including liposomes, polymeric nanoparticles, dendrimers, inorganic nanoparticles, exosomes, and red blood cells for targeted drug delivery in cancer is discussed.

Intra- and intercellular transport of substances: Models and mechanisms

Non-equilibrium-statistical models of intracellular transport are built. The most significant features of these models are microscopic reversibility and the explicit considerations of the driving forces of the process - the ATP-ADP chemical potential difference. In this paper, water transport using contractile vacuoles, the transport and assembly of microtubules and microfilaments, the protein distribution within a cell, the transport of neurotransmitters from the synaptic cleft and the transport of substances between cells using plasmodesmata are discussed. Endocytosis and phagocytosis models are considered, and transport tasks and information transfer mechanisms inside the cell are explored. Based on an analysis of chloroplast movement, it was concluded that they have a complicated method of influencing each other in the course of their movements. The role of quantum effects in sorting and control transport mechanisms is also discussed. It is likely that quantum effects play a large role in these processes, otherwise reliable molecular recognition would be impossible, which would lead to very low intracellular transport efficiency.

Carbohydrate-based nanocarriers and their application to target macrophages and deliver antimicrobial agents

Many deadly infections are produced by microorganisms capable of sustained survival in macrophages. This reduces exposure to chemadrotherapy, prevents immune detection, and is akin to criminals hiding in police stations. Therefore, the use of glyco-nanoparticles (GNPs) as carriers of therapeutic agents is a burgeoning field. Such an approach can enhance the penetration of drugs into macrophages with specific carbohydrate targeting molecules on the nanocarrier to interact with macrophage lectins. Carbohydrates are natural biological molecules and the key constituents in a large variety of biological events such as cellular communication, infection, inflammation, enzyme trafficking, cellular migration, cancer metastasis and immune functions. The prominent characteristics of carbohydrates including biodegradability, biocompatibility, hydrophilicity and the highly specific interaction of targeting cell-surface receptors support their potential application to drug delivery systems (DDS). This review presents the 21^st century development of carbohydrate-based nanocarriers for drug targeting of therapeutic agents for diseases localized in macrophages. The significance of natural carbohydrate-derived nanoparticles (GNPs) as anti-microbial drug carriers is highlighted in several areas of treatment including tuberculosis, salmonellosis, leishmaniasis, candidiasis, and HIV/AIDS.

The Crystallinity and Aspect Ratio of Cellulose Nanomaterials Determine Their Pro-Inflammatory and Immune Adjuvant Effects In Vitro and In Vivo

Nanocellulose is increasingly considered for applications; however, the fibrillar nature, crystalline phase, and surface reactivity of these high aspect ratio nanomaterials need to be considered for safe biomedical use. Here a comprehensive analysis of the impact of cellulose nanofibrils (CNF) and nanocrystals (CNC) is performed using materials provided by the Nanomaterial Health Implications Research Consortium of the National Institute of Environmental Health Sciences. An intermediary length of nanocrystals is also derived by acid hydrolysis. While all CNFs and CNCs are devoid of cytotoxicity, 210 and 280 nm fluorescein isothiocyanate (FITC)-labeled CNCs show higher cellular uptake than longer and shorter CNCs or CNFs. Moreover, CNCs in the 200-300 nm length scale are more likely to induce lysosomal damage, NLRP3 inflammasome activation, and IL-1β production than CNFs. The pro-inflammatory effects of CNCs are correlated with higher crystallinity index, surface hydroxyl density, and reactive oxygen species generation. In addition, CNFs and CNCs can induce maturation of bone marrow-derived dendritic cells and CNCs (and to a lesser extent CNFs) are found to exert adjuvant effects in ovalbumin (OVA)-injected mice, particularly for 210 and 280 nm CNCs. All considered, the data demonstrate the importance of length scale, crystallinity, and surface reactivity in shaping the innate immune response to nanocellulose.

Entry modes of ellipsoidal nanoparticles on a membrane during clathrin-mediated endocytosis

The membrane wrapping and internalization of nanoparticles, such as viruses and drug nanocarriers, through clathrin-mediated endocytosis (CME) are vitally important for intracellular transport. During CME, the shape of the particle plays crucial roles in the determination of particle-membrane interactions, but much of the previous work has been focused on spherical particles. In this work, we develop a stochastic model to study the CME of ellipsoidal particles. In our model, the deformation of the membrane and wrapping of the nanoparticles are driven by the accumulation of clathrin lattices, which is stimulated by the ligand-receptor interactions. Using our model, we systematically investigate the effect of particle shape (ellipsoids with different aspect ratios) on the CME. Our results show three entry modes: tip-first, tilted, and laying-down modes, used by ellipsoidal nanoparticles for internalization depending on the aspect ratio. Certain ellipsoids are able to take multiple entry modes for internalization. Interestingly, the prolate ellipsoid with an aspect ratio of 0.42 can be internalized with a significantly reduced number of ligand-receptor bonds. Particles which can be internalized with fewer bonds are excellent candidates for transcellular drug delivery. Moreover, our results demonstrate that internalization of ellipsoids with intermediate aspect ratios is easier than that of particles with low and high aspect ratios. Our model and simulations provide critical mechanistic insights into CME of ellipsoidal particles, and represent a viable platform for optimal design of nanoparticles for targeted drug delivery applications.

Antibody-Dependent Cellular Phagocytosis in Antiviral Immune Responses

Antiviral activities of antibodies may either be dependent only on interactions between the antibody and cognate antigen, as in binding and neutralization of an infectious virion, or instead may require interactions between antibody-antigen immune complexes and immunoproteins or Fc receptor expressing immune effector cells. These Fc receptor-dependent antibody functions provide a direct link between the innate and adaptive immune systems by combining the potent antiviral activity of innate effector cells with the diversity and specificity of the adaptive humoral response. The Fc receptor-dependent function of antibody-dependent cellular phagocytosis (ADCP) provides mechanisms for clearance of virus and virus-infected cells, as well as for stimulation of downstream adaptive immune responses by facilitating antigen presentation, or by stimulating the secretion of inflammatory mediators. In this review, we discuss the properties of Fc receptors, antibodies, and effector cells that influence ADCP. We also provide and interpret evidence from studies that support a potential role for ADCP in either inhibiting or enhancing viral infection. Finally, we describe current approaches used to measure antiviral ADCP and discuss considerations for the translation of studies performed in animal models. We propose that additional investigation into the role of ADCP in protective viral responses, the specific virus epitopes targeted by ADCP antibodies, and the types of phagocytes and Fc receptors involved in ADCP at sites of virus infection will provide insight into strategies to successfully leverage this important immune response for improved antiviral immunity through rational vaccine design.