Red blood cells affect the margination of microparticles in synthetic microcapillaries and intravital microcirculation as a function of their size and shape

The interaction between particles and vascular endothelium in blood flow

Particle-based drug delivery systems have shown promising application potential to treat human diseases; however, an incomplete understanding of their interactions with vascular endothelium in blood flow prevents their inclusion into mainstream clinical applications. The flow performance of nano/micro-sized particles in the blood are disturbed by many external/internal factors, including blood constituents, particle properties, and endothelium bioactivities, affecting the fate of particles in vivo and therapeutic effects for diseases. This review highlights how the blood constituents, hemodynamic environment and particle properties influence the interactions and particle activities in vivo. Moreover, we briefly summarized the structure and functions of endothelium and simulated devices for studying particle performance under blood flow conditions. Finally, based on particle-endothelium interactions, we propose future opportunities for novel therapeutic strategies and provide solutions to challenges in particle delivery systems for accelerating their clinical translation. This review helps provoke an increasing in-depth understanding of particle-endothelium interactions and inspires more strategies that may benefit the development of particle medicine.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

The flow of anisotropic nanoparticles in solution and in blood

The alignment of anisotropic nanoparticles in flow has been used for a range of applications such as the preparation of strong fibres and the assembly of in-plane aligned 1D-nanoobjects that are used for electronic devices, sensors, energy and biological application. Important is also the flow behaviour of nanoparticles that were designed for nanomedical applications such as drug delivery. It is widely observed that non-spherical nanoparticles have longer circulation times and a more favourable biodistribution. To be able to understand this behaviour, researchers have turned to analyzing the flow of non-spherical nanoparticles in the blood stream. In this review, an overview of microfluidic techniques that are used to monitor the alignment of anisotropic nanoparticles in solution will be provided, which includes analysis by small angle X-ray scattering (SAXS) and polarized light microscopy. The flow of these nanoparticles in blood is then discussed as the presence of red blood cells causes margination of some nanoparticles. Using fluorescence microscopy, the extent of margination can be identified, which coincides with the ability of nanoparticles to adhere to the cells grown along the wall. While these studies are mainly carried out in vitro using blood, initial investigations in vivo were able to confirm the unusual flow of anisotropic nanoparticles.

Margination of 2D Platelet Microparticles in Blood

Margination describes the movement of particles toward the endothelial wall within blood vessels. While there have been several studies tracking the margination of spherical particles in blood, the behavior of anisotropic particle shapes is not well described. In this study 2D platelet particles which possess many attractive qualities for use as a drug delivery system, with their high surface area allowing for increased surface binding activity, were directly monitored and margination quantified. The margination propensity of 1 and 2 μm 2D platelet particles was contrasted to that of 2 μm spherical particles at apparent wall shear rates (WSRs) of 50, 100, and 200 s^-1 by both directly tracking labeled particles using fluorescent microscopy as well as using small-angle X-ray scattering (SAXS). For fluorescence studies, margination was quantified using the margination parameter M, which describes the number of particles found closest to the walls of a microfluidic device, with an M-value of 0.2 indicating no margination. Increased margination was seen in 2D platelet particles when compared to spherical particles tested at all flow rates, with M-values of 0.39 and 0.31 seen for 1 and 2 μm 2D platelet particles, respectively, while 2 μm spherical particles had an M-value of 0.21. Similarly, margination was observed qualitatively using SAXS, with increased scattering seen for platelet particles near the microfluidic channel wall. For all particles, increased margination was seen at increasing shear rates.

Quantifying Shear-induced Margination and Adhesion of Platelets in Microvascular Blood Flow

Platelet margination and adhesion are two critical and closely related steps in thrombus formation. Using dissipative particle dynamics (DPD) method that seamlessly models blood cells, blood plasma, and vessel walls with functionalized surfaces, we quantify the shear-induced margination and adhesion of platelets in microvascular blood flow. The results show that the occurrence of shear-induced RBC-platelet collisions has a remarkable influence on the degree of platelet margination. We characterize the lateral motion of individual platelets by a mean square displacement analysis of platelet trajectories, and find that the wall-induced lift force and the shear-induced displacement in wall-bounded flow cause the variation in near-wall platelet distribution. We then investigate the platelet adhesive dynamics under different flow conditions, by conducting DPD simulations of blood flow in a microtube with fibrinogen-coated wall surfaces. We find that the platelet adhesion is enhanced with the increase of fibrinogen concentration level but decreased with the increase of shear rate. These results are consistent with available experimental results. In addition, we demonstrate that the adherent platelets have a negative impact on the margination dynamics of the circulating platelets, which is mainly due to the climbing effect induced by the adherent ones. Taken together, these findings provide useful insights into the platelet margination and adhesion dynamics, which may facilitate the understanding of the predominant processes governing the initial stage of thrombus formation.

Shear induced diffusion of platelets revisited

The transport of platelets in blood is commonly assumed to obey an advection-diffusion equation with a diffusion constant given by the so-called Zydney-Colton theory. Here we reconsider this hypothesis based on experimental observations and numerical simulations including a fully resolved suspension of red blood cells and platelets subject to a shear. We observe that the transport of platelets perpendicular to the flow can be characterized by a non-trivial distribution of velocities with and exponential decreasing bulk, followed by a power law tail. We conclude that such distribution of velocities leads to diffusion of platelets about two orders of magnitude higher than predicted by Zydney-Colton theory. We tested this distribution with a minimal stochastic model of platelets deposition to cover space and time scales similar to our experimental results, and confirm that the exponential-powerlaw distribution of velocities results in a coefficient of diffusion significantly larger than predicted by the Zydney-Colton theory.

Micro-particle entrapment dynamics in microfluidic pulmonary capillary networks

The journey of vascular targeted carriers (VTC) in the circulatory system is highly intricate and includes navigation through different vessel structures, such as the vast pulmonary capillary network (PCN) in the lungs where particles can get entrapped and lead to blockage. Here, we leverage microfluidic PCN models to explore, for the first time, micro-particle capillary entrapment, in a well-controlled biophysical environment mimicking human physiological hemodynamics at true scale. This in vitro strategy mimics the challenges of vascular carrier transport during their journey in the smallest capillaries of the body (∼5 µm). Specifically, we explore in the PCN model entrapment dynamics of spherical micro-particles of different diameters (i.e. 3, 4 and 4.5 µm) at different concentrations, comparing their motion in cell-free buffer to that in the presence of red blood cells (RBCs). Notably, while 3 µm particles exhibit undisturbed transport in all of the examined concentrations, both in cell-free buffer and in the presence of RBCs, particles of 4 and 4.5 µm exhibit a concentration-dependent transport where the presence of RBCs leads in fact to reduced entrapment. Our experiments suggest that collisions of micro-particles with RBCs can facilitate their navigability, allowing for carrier transport that would lead otherwise to rapid entrapment in a cell-free environment. Altogether, the proposed preclinical in vitro assays offer rapid screening opportunities for design optimization of VTC transport in capillary networks.

Transport Behavior of Commercial Anticancer Drug Protein-Bound Paclitaxel (Paclicad) in a Micron-Sized Channel

Protein-bound paclitaxel has been developed clinically as one of the most successful chemotherapy drugs for the treatment of a wide variety of cancers. However, these medications, due to their nanoscale properties, may often induce capillary blocking while migrating through minute blood vessels. Considering the detrimental impact of this restriction, we investigated the transport of protein-bound paclitaxel, Paclicad, in a 7 μm microchannel mimicking the identical mechanical confinement of the blood capillaries. The drug was reported to migrate through a constricted microchannel without obstruction at a solution flow rate of 20-50 μL/h. The onset of an agglomeration site was observed at higher flow rates of 70-90 μL/h, while complete capillary obstruction was observed at 100 μL/h. The mobility of the particles was also calculated, and the results suggested that the presence of varying cross-sections affects the mobility of the drug particles. The trajectory of the particle migration was observed to be less tortuous at the higher flow rate, but the tortuous nature appeared to increase with the presence of agglomeration sites in the flow field. The experimental results were also compared with the computational model of the drug particle. The drug particle was modeled both as Newtonian and as an FENE-P viscoelastic drop. The drop interface tracking was done by the VOF method using the open source software Basilisk. The particle displacement was better estimated by both the FENE-P and Newtonian model at a flow rate of 30 μL/h, while deviation was observed at a flow rate of 50 μL/h. The FENE-P model was observed to show higher deformation than the Newtonian model at both flow rates. The experimental results provided better insight into the agglomeration tendency of Paclicad, migrating through a constricted microchannel at higher flow rates. The numerical model could be further employed to understand the more complex intravenous transport of drugs.

The effect of rigid cells on blood viscosity: linking rheology and sickle cell anemia

Sickle cell anemia (SCA) is a disease that affects red blood cells (RBCs). Healthy RBCs are highly deformable objects that under flow can penetrate blood capillaries smaller than their typical size. In SCA there is an impaired deformability of some cells, which are much stiffer and with a different shape than healthy cells, and thereby affect regular blood flow. It is known that blood from patients with SCA has a higher viscosity than normal blood. However, it is unclear how the rigidity of cells is related to the viscosity of blood, in part because SCA patients are often treated with transfusions of variable amounts of normal RBCs and only a fraction of cells will be stiff. Here, we report systematic experimental measurements of the viscosity of a suspension varying the fraction of rigid particles within a suspension of healthy cells. We also perform systematic numerical simulations of a similar mixed suspension of soft RBCs, rigid particles, and their hydrodynamic interactions. Our results show that there is a rheological signature within blood viscosity to clearly identify the fraction of rigidified cells among healthy deformable cells down to a 5% volume fraction of rigidified cells. Although aggregation of RBCs is known to affect blood rheology at low shear rates, and our simulations mimic this effect via an adhesion potential, we show that such adhesion, or aggregation, is unlikely to provide a physical rationalization for the viscosity increase observed in the experiments at moderate shear rates due to rigidified cells. Through numerical simulations, we also highlight that most of the viscosity increase of the suspension is due to the rigidity of the particles rather than their sickled or spherical shape. Our results are relevant to better characterize SCA, provide useful insights relevant to rheological consequences of blood transfusions, and, more generally, extend to the rheology of mixed suspensions having particles with different rigidities, as well as offering possibilities for developments in the field of soft material composites.

Organic electrochemical transistors as novel biosensing platforms to study the electrical response of whole blood and plasma

In this paper, for the first time to the best of our knowledge, organic electrochemical transistors are employed to investigate the electrical response of human blood, plasma and alternative buffer solutions that inhibit red blood cell (RBC) aggregation. Our focus is on selecting a suitable electrolytic platform and the related operating conditions, where the RBC effect on the OECT response can be observed separately from the strong ionic environment of plasma in whole blood. The transient response of whole blood to pulse experiments is characterized by two time constants, which can be related to blood viscosity and to the capacitive coupling between the ionic and electronic components of the overall system. The role of capacitive effects, likely due to enhanced double-layer formation by negatively charged RBCs, is also confirmed by the increase of transconductance which was found in RBC suspensions as compared to the suspending buffer. Overall, the complex behavior found in these experiments provides new insights for the development of innovative blood-based sensing devices for biomedical applications.

Margination of Platelet-Sized Particles in the Red Blood Cell Suspension Flow through Square Microchannels

In the blood flow through microvessels, platelets show high concentrations near the vessel wall. This phenomenon is called margination of platelets and is closely associated with hemostasis and thrombosis. In the present study, we conducted in vitro experiments using platelet-sized fluorescent particles as platelet substitutes to investigate the cross-sectional distribution of these particles in the red blood cell suspension flowing through microchannels with a square cross section. Fluorescence observations were performed to measure the transverse distribution of particles at various heights from the bottom face with the use of a confocal laser scanning microscope system. In downstream cross sections of the channel, particles showed focusing near the four corners rather than uniform margination along the entire circumference of the cross section. The focusing of particles near the corners was more enhanced for higher hematocrits. On the other hand, particles in circular channel flows showed nearly axisymmetric uniform accumulation adjacent to the channel wall. The present result suggests that the segregation of suspended particles in the flow of multicomponent suspensions could have such heterogeneous 2D features of particle distribution in the cross section of channels, especially for rectangular channels often used in microfluidics.

Elucidating the rheological implications of adding particles in blood

In the past few decades, nanotechnology has been employed to provide breakthroughs in the diagnosis and treatment of several diseases using drug-carrying particles (DCPs). In such an endeavor, the optimal design of DCPs is paramount, which necessitates the use of an accurate and trustworthy constitutive model in computational fluid dynamics (CFD) simulators. We herein introduce a continuum model for elaborating on the rheological implications of adding particles in blood. The model is developed using non-equilibrium thermodynamics to guarantee thermodynamic admissibility. Red blood cells are modeled as deformed droplets with a constant volume that are able to aggregate, whereas particles are considered rigid spheroids. The model predictions are compared favorably against rheological data for both spherical and non-spherical particles immersed in non-aggregating blood. It is expected that the use of this model will allow for the testing of DCPs in virtual patients and for their tailor-design in treating various diseases.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00397-021-01289-x.

Cellulose nanocrystals: a multimodal tool to enhance the targeted drug delivery against bone disorders

Aim: We investigated the use of cellulose nanocrystals (CNCs) as drug nanocarriers combining an anti-osteoporotic agent, alendronate (ALN), and an anti-cancer drug, doxorubicin (DOX). Materials & methods: CNC physicochemical characterization, in vivo imaging coupled with histology and in vitro uptake and toxicity assays were carried out. Results: In vivo CNC-ALN did not modify bone tropism and lung penetration, whereas its liver and kidney accumulation was slightly higher compared with CNCs alone. In vitro studies showed that CNC-ALN did not impair ALN's effect on osteoclasts, whereas CNC-DOX confirmed the therapeutic potential against bone metastatic cancer cells. Conclusions: This study provides robust proof of the potential of CNCs as easy, flexible and specific carriers to deliver compounds to the bone.

Factors affecting the morphology of some organic and inorganic nanostructures for drug delivery: characterization, modifications, and toxicological perspectives

Introduction: In this review, we aim to highlight the impact of various processes and formulation variables influencing the characteristics of certain surfactant-based nanoconstructs for drug delivery. Areas covered: The review includes the discussion on processing parameters for the preparation of nanoconstructs, especially those made up of surfactants. Articles published in last 15 years (437) were reviewed, 381 articles were selected for data review and most appropriate articles (215) were included in article. Effect of variables such as surfactant concentration and type, membrane additives, temperature, and pH-dependent transitions on morphology has been highlighted along with effect of shape on nanoparticle uptake by cells. Various characterization techniques explored for these nanostructures with respect to size, morphology, lamellarity, distribution, etc., and a separate section on polymeric vesicles and the influence of block copolymers, type of block copolymer, control of block length, interaction of multiple block copolymers on the structure of polymersomes and chimeric nanostructures have been discussed. Finally, applications, modification, degradation, and toxicological aspects of these drug delivery systems have been highlighted. Expert opinion: Parameters influencing the morphology of micelles and vesicles can directly or indirectly affect the efficacy of small molecule cellular internalization as well as uptake in the case of biologicals.[Figure: see text].

Multiscale modeling of protein membrane interactions for nanoparticle targeting in drug delivery

Nanoparticle (NP)-based imaging and drug delivery systems for systemic (e.g. intravenous) therapeutic and diagnostic applications are inherently a complex integration of biology and engineering. A broad range of length and time scales are essential to hydrodynamic and microscopic molecular interactions mediating NP (drug nanocarriers, imaging agents) motion in blood flow, cell binding/uptake, and tissue accumulation. A computational model of time-dependent tissue delivery, providing in silico prediction of organ-specific accumulation of NPs, can be leveraged in NP design and clinical applications. In this article, we provide the current state-of-the-art and future outlook for the development of predictive models for NP transport, targeting, and distribution through the integration of new computational schemes rooted in statistical mechanics and transport. The resulting multiscale model will comprehensively incorporate: (i) hydrodynamic interactions in the vascular scales relevant to NP margination; (ii) physical and mechanical forces defining cellular and tissue architecture and epitope accessibility mediating NP adhesion; and (iii) subcellular and paracellular interactions including molecular-level targeting impacting NP uptake.

Drug Delivery System Based on pH-Sensitive Biocompatible Poly(2-vinyl pyridine)-b-poly(ethylene oxide) Nanomicelles Loaded with Curcumin and 5-Fluorouracil

Smart polymeric micelles (PMs) are of practical interest as nanocarriers for the encapsulation and controlled release of hydrophobic drugs. Two hydrophobic drugs, naturally-based curcumin (Cur) and synthetic 5-fluorouracil (5-FU), were loaded into the PMs formed by a well-defined pH-sensitive poly(2-vinyl pyridine)-b-poly(ethylene oxide) (P2VP₉₀-b-PEO₃₉₈) block copolymer. The influence of the drug loading on the micellar sizes was investigated by dynamic light scattering (DLS) and it appears that the size of the PMs increases from around 60 to 100 nm when Cur is loaded. On the contrary, the loading of the 5-FU has a smaller effect on the micellar sizes. This difference can be attributed to higher molar mass of Cur with respect to 5-FU but also to higher loading efficiency of Cur, 6.4%, compared to that of 5-FU, 5.8%. In vitro drug release was studied at pH 2, 6.8, and 7.4, and it was observed that the pH controls the release of both drugs. At pH 2, where the P2VP sequences from the “frozen-in” micellar core are protonated, the drug release efficiencies exceed 90%. Moreover, it was demonstrated, by in vitro assays, that these PMs are hemocompatible and biocompatible. Furthermore, the PMs protect the Cur against the photo-degradation, whereas the non-ionic PEO corona limits the adsorption of bovine serum albumin (BSA) protein on the surface. This study demonstrates that these pH-sensitive PMs are suitable for practical utilization as human-safe and smart, injectable drug delivery systems.

Liposome-Embedding Silicon Microparticle for Oxaliplatin Delivery in Tumor Chemotherapy

Mesoporous silicon microparticles (MSMPs) can incorporate drug-carrying nanoparticles (NPs) into their pores. An NP-loaded MSMP is a multistage vector (MSV) that forms a Matryoshka-like structure that protects the therapeutic cargo from degradation and prevents its dilution in the circulation during delivery to tumor cells. We developed an MSV constituted by 1 µm discoidal MSMPs embedded with PEGylated liposomes containing oxaliplatin (oxa) which is a therapeutic agent for colorectal cancer (CRC). To obtain extra-small liposomes able to fit the 60 nm pores of MSMP, we tested several liposomal formulations, and identified two optimal compositions, with a prevalence of the rigid lipid 1,2-distearoyl-sn-glycero-3-phosphocholine and of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000]. To improve the MSV assembly, we optimized the liposome-loading inside the MSMP and achieved a five-fold increase of the payload using an innovative lyophilization approach. This procedure also increased the load and limited dimensional changes of the liposomes released from the MSV in vitro. Lastly, we found that the cytotoxic efficacy of oxa-loaded liposomes and-oxa-liposome-MSV in CRC cell culture was similar to that of free oxa. This study increases knowledge about extra-small liposomes and their loading into porous materials and provides useful hints about alternative strategies for designing drug-encapsulating NPs.

Nanoparticle Platforms for Antigen-Specific Immune Tolerance

Innovative approaches in nanoparticle design have facilitated the creation of new formulations of nanoparticles that are capable of selectively calibrating the immune response. These nanomaterials may be engineered to interact with specific cellular and molecular targets. Recent advancements in nanoparticle synthesis have enabled surface functionalization of particles that mimic the diversity of ligands on the cell surface. Platforms synthesized using these design principles, called "biomimetic" nanoparticles, have achieved increasingly sophisticated targeting specificity and cellular trafficking capabilities. This holds great promise for next generation therapies that seek to achieve immune tolerance. In this review, we discuss the importance of physical design parameters including size, shape, and biomimetic surface functionalization, on the biodistribution, safety and efficacy of biologic nanoparticles. We will also explore potential applications for immune tolerance for organ or stem cell transplantation.

Smeared Multiscale Finite Element Models for Mass Transport and Electrophysiology Coupled to Muscle Mechanics

Mass transport represents the most fundamental process in living organisms. It includes delivery of nutrients, oxygen, drugs, and other substances from the vascular system to tissue and transport of waste and other products from cells back to vascular and lymphatic network and organs. Furthermore, movement is achieved by mechanical forces generated by muscles in coordination with the nervous system. The signals coming from the brain, which have the character of electrical waves, produce activation within muscle cells. Therefore, from a physics perspective, there exist a number of physical fields within the body, such as velocities of transport, pressures, concentrations of substances, and electrical potential, which is directly coupled to biochemical processes of transforming the chemical into mechanical energy and further internal forces for motion. The overall problems of mass transport and electrophysiology coupled to mechanics can be investigated theoretically by developing appropriate computational models. Due to the enormous complexity of the biological system, it would be almost impossible to establish a detailed computational model for the physical fields related to mass transport, electrophysiology, and coupled fields. To make computational models feasible for applications, we here summarize a concept of smeared physical fields, with coupling among them, and muscle mechanics, which includes dependence on the electrical potential. Accuracy of the smeared computational models, also with coupling to muscle mechanics, is illustrated with simple example, while their applicability is demonstrated on a liver model with tumors present. The last example shows that the introduced methodology is applicable to large biological systems.

Strategies for Delivery of siRNAs to Ovarian Cancer Cells

The unmet need for novel therapeutic options for ovarian cancer (OC) deserves further investigation. Among the different novel drugs, small interfering RNAs (siRNAs) are particularly attractive because of their specificity of action and efficacy, as documented in many experimental setups. However, the fragility of these molecules in the biological environment necessitates the use of delivery materials able to protect them and possibly target them to the cancer cells. Among the different delivery materials, those based on polymers and lipids are considered very interesting because of their biocompatibility and ability to carry/deliver siRNAs. Despite these features, polymers and lipids need to be engineered to optimize their delivery properties for OC. In this review, we concentrated on the description of the therapeutic potential of siRNAs and polymer-/lipid-based delivery systems for OC. After a brief description of OC and siRNA features, we summarized the strategies employed to minimize siRNA delivery problems, the targeting strategies to OC, and the preclinical models available. Finally, we discussed the most interesting works published in the last three years about polymer-/lipid-based materials for siRNA delivery.

Antimargination of Microparticles and Platelets in the Vicinity of Branching Vessels

We investigate the margination of microparticles/platelets in blood flow through complex geometries typical for in vivo vessel networks: a vessel confluence and a bifurcation. Using three-dimensional lattice Boltzmann simulations, we confirm that behind the confluence of two vessels, a cell-free layer devoid of red blood cells develops in the channel center. Despite its small size of roughly 1 μm, this central cell-free layer persists for up to 100 μm after the confluence. Most importantly, we show from simulations that this layer also contains a significant amount of microparticles/platelets and validate this result by in vivo microscopy in mouse venules. At bifurcations, however, a similar effect does not appear, and margination is largely unaffected by the geometry. This antimargination toward the vessel center after a confluence may explain earlier in vivo observations, which found that platelet concentrations near the vessel wall are seen to be much higher on the arteriolar side (containing bifurcations) than on the venular side (containing confluences) of the vascular system.

Cell membrane protein functionalization of nanoparticles as a new tumor-targeting strategy

Nanoparticles have seen considerable popularity as effective tools for drug delivery. However, non-specific targeting continues to remain a challenge. Recently, biomimetic nanoparticles have emerged as an innovative solution that exploits biologically-derived components to improve therapeutic potential. Specifically, cell membrane proteins extracted from various cells (i.e., leukocytes, erythrocytes, platelets, mesenchymal stem cells, cancer) have shown considerable promise in bestowing nanoparticles with increased circulation and targeting efficacy. Traditional nanoparticles can be detected and removed by the immune system which significantly hinders their clinical success. Biomimicry has been proposed as a promising approach to overcome these limitations. In this review, we highlight the current trends in biomimetic nanoparticles and describe how they are being used to increase their chemotherapeutic effect in cancer treatment.

Photoluminescent and biodegradable porous silicon nanoparticles for biomedical imaging

A set of unique properties including biodegradability, intrinsic photoluminescence, and mesoporous structure allows porous silicon nanoparticles to address current challenges of translational nanomedicine, especially in biomedical imaging.

Quantifying Platelet Margination in Diabetic Blood Flow

Patients with type 2 diabetes mellitus (T2DM) develop thrombotic abnormalities strongly associated with cardiovascular diseases. In addition to the changes of numerous coagulation factors such as elevated levels of thrombin and fibrinogen, the abnormal rheological effects of red blood cells (RBCs) and platelets flowing in blood are crucial in platelet adhesion and thrombus formation in T2DM. An important process contributing to the latter is the platelet margination. We employ the dissipative particle dynamics method to seamlessly model cells, plasma, and vessel walls. We perform a systematic study on RBC and platelet transport in cylindrical vessels by considering different cell shapes, sizes, and RBC deformabilities in healthy and T2DM blood, as well as variable flowrates and hematocrit. In particular, we use cellular-level RBC and platelet models with parameters derived from patient-specific data and present a sensitivity study. We find T2DM RBCs, which are less deformable compared to normal RBCs, lower the transport of platelets toward the vessel walls, whereas platelets with higher mean volume (often observed in T2DM) lead to enhanced margination. Furthermore, increasing the flowrate or hematocrit enhances platelet margination. We also investigated the effect of platelet shape and observed a nonmonotonic variation with the highest near-wall concentration corresponding to platelets with a moderate aspect ratio of 0.38. We examine the role of white blood cells (WBCs), whose count is increased notably in T2DM patients. We find that WBC rolling or WBC adhesion tends to decrease platelet margination due to hydrodynamic effects. To the best of our knowledge, such simulations of blood including all blood cells have not been performed before, and our quantitative findings can help separate the effects of hydrodynamic interactions from adhesive interactions and potentially shed light on the associated pathological processes in T2DM such as increased inflammatory response, platelet activation and adhesion, and ultimately thrombus formation.

Synergistic Integration of Laboratory and Numerical Approaches in Studies of the Biomechanics of Diseased Red Blood Cells

In red blood cell (RBC) disorders, such as sickle cell disease, hereditary spherocytosis, and diabetes, alterations to the size and shape of RBCs due to either mutations of RBC proteins or changes to the extracellular environment, lead to compromised cell deformability, impaired cell stability, and increased propensity to aggregate. Numerous laboratory approaches have been implemented to elucidate the pathogenesis of RBC disorders. Concurrently, computational RBC models have been developed to simulate the dynamics of RBCs under physiological and pathological conditions. In this work, we review recent laboratory and computational studies of disordered RBCs. Distinguished from previous reviews, we emphasize how experimental techniques and computational modeling can be synergically integrated to improve the understanding of the pathophysiology of hematological disorders.

Vascular-targeted particle binding efficacy in the presence of rigid red blood cells: Implications for performance in diseased blood

The field of drug delivery has taken an interest in combating numerous blood and heart diseases via the use of injectable vascular-targeted carriers (VTCs). However, VTC technology has encountered limited efficacy due to a variety of challenges associated with the immense complexity of the in vivo blood flow environment, including the hemodynamic interactions of blood cells, which impact their margination and adhesion to the vascular wall. Red blood cell (RBC) physiology, i.e., size, shape, and deformability, drive cellular distribution in blood flow and has been shown to impact VTC margination to the vessel wall significantly. The RBC shape and deformability are known to be altered in certain human diseases, yet little experimental work has been conducted towards understanding the effect of these alterations, specifically RBC rigidity, on VTC dynamics in physiological blood flow. In this work, we investigate the impact of RBCs of varying stiffnesses on the adhesion efficacy of particles of various sizes, moduli, and shapes onto an inflamed endothelial layer in a human vasculature-inspired, in vitro blood flow model. The blood rigid RBC compositions and degrees of RBC stiffness evaluated are analogous to conditions in diseases such as sickle cell disease. We find that particles of different sizes, moduli, and shapes yield drastically different adhesion patterns in blood flow in the presence of rigid RBCs when compared to 100% healthy RBCs. Specifically, up to 50% reduction in the localization and adhesion of non-deformable 2 μm particles to the vessel wall was observed in the presence of rigid RBCs. Interestingly, deformable 2 μm particles showed enhanced vessel wall localization and adhesion, by up to 85%, depending on the rigidity of RBCs evaluated. Ultimately, this work experimentally clarifies the importance of considering RBC rigidity in the intelligent design of particle therapeutics and highlights possible implications for a wide range of diseases relating to RBC deformability.

Tailoring Porous Silicon for Biomedical Applications: From Drug Delivery to Cancer Immunotherapy

In the past two decades, porous silicon (PSi) has attracted increasing attention for its potential biomedical applications. With its controllable geometry, tunable nanoporous structure, large pore volume/high specific surface area, and versatile surface chemistry, PSi shows significant advantages over conventional drug carriers. Here, an overview of recent progress in the use of PSi in drug delivery and cancer immunotherapy is presented. First, an overview of the fabrication of PSi with various geometric structures is provided, with particular focus on how the unique geometry of PSi facilitates its biomedical applications, especially for drug delivery. Second, surface chemistry and modification of PSi are discussed in relation to the strengthening of its performance in drug delivery and bioimaging. Emerging technologies for engineering PSi-based composites are then summarized. Emerging PSi advances in the context of cancer immunotherapy are also highlighted. Overall, very promising research results encourage further exploration of PSi for biomedical applications, particularly in drug delivery and cancer immunotherapy, and future translation of PSi into clinical applications.

Multiscale smeared finite element model for mass transport in biological tissue: From blood vessels to cells and cellular organelles

One of the basic and vital processes in living organisms is mass exchange, which occurs on several levels: it goes from blood vessels to cells and organelles within cells. On that path, molecules, as oxygen, metabolic products, drugs, etc. Traverse different macro and micro environments - blood, extracellular/intracellular space, and interior of organelles; and also biological barriers such as walls of blood vessels and membranes of cells and organelles. Many aspects of this mass transport remain unknown, particularly the biophysical mechanisms governing drug delivery. The main research approach relies on laboratory and clinical investigations. In parallel, considerable efforts have been directed to develop computational tools for additional insight into the intricate process of mass exchange and transport. Along these lines, we have recently formulated a composite smeared finite element (CSFE) which is composed of the smeared continuum pressure and concentration fields of the capillary and lymphatic system, and of these fields within tissue. The element offers an elegant and simple procedure which opens up new lines of inquiry and can be applied to large systems such as organs and tumors models. Here, we extend this concept to a multiscale scheme which concurrently couples domains that span from large blood vessels, capillaries and lymph, to cell cytosol and further to organelles of nanometer size. These spatial physical domains are coupled by the appropriate connectivity elements representing biological barriers. The composite finite element has "degrees of freedom" which include pressures and concentrations of all compartments of the vessels-tissue assemblage. The overall model uses the standard, measurable material properties of the continuum biological environments and biological barriers. It can be considered as a framework into which we can incorporate various additional effects (such as electrical or biochemical) for transport through membranes or within cells. This concept and the developed FE software within our package PAK offers a computational tool that can be applied to whole-organ systems, while also including specific domains such as tumors. The solved examples demonstrate the accuracy of this model and its applicability to large biological systems.

Polymer-Mediated Delivery of siRNAs to Hepatocellular Carcinoma: Variables Affecting Specificity and Effectiveness

Despite the advances in anticancer therapies, their effectiveness for many human tumors is still far from being optimal. Significant improvements in treatment efficacy can come from the enhancement of drug specificity. This goal may be achieved by combining the use of therapeutic molecules with tumor specific effects and delivery carriers with tumor targeting ability. In this regard, nucleic acid-based drug (NABD) and particularly small interfering RNAs (siRNAs), are attractive molecules due to the possibility to be engineered to target specific tumor genes. On the other hand, polymeric-based delivery systems are emerging as versatile carriers to generate tumor-targeted delivery systems. Here we will focus on the most recent findings in the selection of siRNA/polymeric targeted delivery systems for hepatocellular carcinoma (HCC), a human tumor for which currently available therapeutic approaches are poorly effective. In addition, we will discuss the most attracting and, in our opinion, promising siRNA-polymer combinations for HCC in relation to the biological features of HCC tissue. Attention will be also put on the mathematical description of the mechanisms ruling siRNA-carrier delivery, this being an important aspect to improve effectiveness reducing the experimental work.

Enhanced separation of aged RBCs by designing channel cross section

Prolonged storage will alter the biophysical properties of red blood cells (RBCs), and it decreases the quality of stored blood for blood transfusion. It has been known that less deformable aged RBCs can be separated by margination, but the recognition of the storage time from the separation efficiency of the stiff RBCs is still a challenge. In this study, we realized enhanced separation of aged RBCs from normal RBCs by controlling the channel cross section and demonstrated that the storage time can be deduced from the percentage of the separated RBCs in the stored RBCs. This separation technology helps to reveal the regulation of time on the RBC aging mechanism and offer a new method to separate stiffened cells with high efficiency.

Computer simulations of drug release from a liposome into the bloodstream

I propose two-dimensional simulations of drug release from a liposome into the bloodstream. I perform the fluid-structure coupling, between the particles deformation (the liposome and the red blood cells) and the plasma flow, using the immersed boundary method. I compute both the flow and the drug mass transport using the lattice Boltzmann method. The simulations allow computing the instantaneous amount of the released drug, its distribution and its accumulation in the blood vessel wall. These quantities are sensitive to multiple factors and parameters. Here, I briefly explore the impact of having surrounding red blood cells, which are found to enhance slightly the drug release at large Schmidt numbers. In the limit of extremely large permeability of the particles, the drug transport is mainly affected by the complex flow induced by the interplay between the applied flow and the collective motion of the particles.

Biomimetic nanoparticles with enhanced affinity towards activated endothelium as versatile tools for theranostic drug delivery

Activation of the vascular endothelium is characterized by increased expression of vascular adhesion molecules and chemokines. This activation occurs early in the progression of several diseases and triggers the recruitment of leukocytes. Inspired by the tropism of leukocytes, we investigated leukocyte-based biomimetic nanoparticles (i.e., leukosomes) as a novel theranostic platform for inflammatory diseases.

Methods: Leukosomes were assembled by combining phospholipids and membrane proteins from leukocytes. For imaging applications, phospholipids modified with rhodamine and gadolinium were used. Leukosomes incubated with antibodies blocking lymphocyte function-associated antigen 1 (LFA-1) and CD45 were administered to explore their roles in targeting inflammation. In addition, relaxometric assessment of NPs was evaluated.

Results: Liposomes and leukosomes were both spherical in shape with sizes ranging from 140-170 nm. Both NPs successfully integrated 8 and 13 µg of rhodamine and gadolinium, respectively, and demonstrated less than 4% variation in physicochemical features. Leukosomes demonstrated a 16-fold increase in breast tumor accumulation relative to liposomes. Furthermore, quantification of leukosomes in tumor vessels demonstrated a 4.5-fold increase in vessel lumens and a 14-fold increase in vessel walls. Investigating the targeting mechanism of action revealed that blockage of LFA-1 on leukosomes resulted in a 95% decrease in tumor accumulation. Whereas blockage of CD45 yielded a 60% decrease in targeting and significant increases in liver and spleen accumulation. In addition, when administered in mice with atherosclerotic plaques, leukosomes exhibited a 4-fold increase in the targeting of inflammatory vascular lesions. Lastly, relaxometric assessment of NPs demonstrated that the incorporation of membrane proteins into leukosomes did not impact the r₁ and r₂ relaxivities of the NPs, demonstrating 6 and 30 mM^-1s^-1, respectively.

Conclusion: Our study demonstrates the ability of leukosomes to target activated vasculature and exhibit superior accumulation in tumors and vascular lesions. The versatility of the phospholipid backbone within leukosomes permits the incorporation of various contrast agents. Furthermore, leukosomes can potentially be loaded with therapeutics possessing diverse physical properties and thus warrant further investigation toward the development of powerful theranostic agents.

Tumour-vessel-on-a-chip models for drug delivery

Nanocarriers for drug delivery have great potential to revolutionize cancer treatment, due to their enhanced selectivity and efficacy. Despite this great promise, researchers have had limited success in the clinical translation of this approach. One of the main causes of these difficulties is that standard in vitro models, typically used to understand nanocarriers' behaviour and screen their efficiency, do not provide the complexity typically encountered in living systems. In contrast, in vivo models, despite being highly physiological, display serious bottlenecks which threaten the relevancy of the obtained data. Microfluidics and nanofabrication can dramatically contribute to solving this issue, providing 3D high-throughput models with improved resemblance to in vivo systems. In particular, microfluidic models of tumour blood vessels can be used to better elucidate how new nanocarriers behave in the microcirculation of healthy and cancerous tissues. Several key steps of the drug delivery process such as extravasation, immune response and endothelial targeting happen under flow in capillaries and can be accurately modelled using microfluidics. In this review, we will present how tumour-vessel-on-a-chip systems can be used to investigate targeted drug delivery and which key factors need to be considered for the rational design of these materials. Future applications of this approach and its role in driving forward the next generation of targeted drug delivery methods will be discussed.

Recent advances in smart biotechnology: Hydrogels and nanocarriers for tailored bioactive molecules depot

Over the past ten years, the global biopharmaceutical market has remarkably grown, with ten over the top twenty worldwide high performance medical treatment sales being biologics. Thus, biotech R&D (research and development) sector is becoming a key leading branch, with expanding revenues. Biotechnology offers considerable advantages compared to traditional therapeutic approaches, such as reducing side effects, specific treatments, higher patient compliance and therefore more effective treatments leading to lower healthcare costs. Within this sector, smart nanotechnology and colloidal self-assembling systems represent pivotal tools able to modulate the delivery of therapeutics. A comprehensive understanding of the processes involved in the self-assembly of the colloidal structures discussed therein is essential for the development of relevant biomedical applications. In this review we report the most promising and best performing platforms for specific classes of bioactive molecules and related target, spanning from siRNAs, gene/plasmids, proteins/growth factors, small synthetic therapeutics and bioimaging probes.

Margination of Fluorescent Polylactic Acid-Polyaspartamide based Nanoparticles in Microcapillaries In Vitro: the Effect of Hematocrit and Pressure

The last decade has seen the emergence of vascular-targeted drug delivery systems as a promising approach for the treatment of many diseases, such as cardiovascular diseases and cancer. In this field, one of the major challenges is carrier margination propensity (i.e., particle migration from blood flow to vessel walls); indeed, binding of these particles to targeted cells and tissues is only possible if there is direct carrier–wall interaction. Here, a microfluidic system mimicking the hydrodynamic conditions of human microcirculation in vitro is used to investigate the effect of red blood cells (RBCs) on a carrier margination in relation to RBC concentration (hematocrit) and pressure drop. As model drug carriers, fluorescent polymeric nanoparticles (FNPs) were chosen, which were obtained by using as starting material a pegylated polylactic acid–polyaspartamide copolymer. The latter was synthesized by derivatization of α,β-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) with Rhodamine (RhB), polylactic acid (PLA) and then poly(ethyleneglycol) (PEG) chains. It was found that the carrier concentration near the wall increases with increasing pressure drop, independently of RBC concentration, and that the tendency for FNP margination decreases with increasing hematocrit. This work highlights the importance of taking into account RBC–drug carrier interactions and physiological conditions in microcirculation when planning a drug delivery strategy based on systemically administered carriers.

A composite smeared finite element for mass transport in capillary systems and biological tissue

One of the key processes in living organisms is mass transport occurring from blood vessels to tissues for supplying tissues with oxygen, nutrients, drugs, immune cells, and - in the reverse direction - transport of waste products of cell metabolism to blood vessels. The mass exchange from blood vessels to tissue and vice versa occurs through blood vessel walls. This vital process has been investigated experimentally over centuries, and also in the last decades by the use of computational methods. Due to geometrical and functional complexity and heterogeneity of capillary systems, it is however not feasible to model in silico individual capillaries (including transport through the walls and coupling to tissue) within whole organ models. Hence, there is a need for simplified and robust computational models that address mass transport in capillary-tissue systems. We here introduce a smeared modeling concept for gradient-driven mass transport and formulate a new composite smeared finite element (CSFE). The transport from capillary system is first smeared to continuous mass sources within tissue, under the assumption of uniform concentration within capillaries. Here, the fundamental relation between capillary surface area and volumetric fraction is derived as the basis for modeling transport through capillary walls. Further, we formulate the CSFE which relies on the transformation of the one-dimensional (1D) constitutive relations (for transport within capillaries) into the continuum form expressed by Darcy's and diffusion tensors. The introduced CSFE is composed of two volumetric parts - capillary and tissue domains, and has four nodal degrees of freedom (DOF): pressure and concentration for each of the two domains. The domains are coupled by connectivity elements at each node. The fictitious connectivity elements take into account the surface area of capillary walls which belongs to each node, as well as the wall material properties (permeability and partitioning). The overall FE model contains geometrical and material characteristics of the entire capillary-tissue system, with physiologically measurable parameters assigned to each FE node within the model. The smeared concept is implemented into our implicit-iterative FE scheme and into FE package PAK. The first three examples illustrate accuracy of the CSFE element, while the liver and pancreas models demonstrate robustness of the introduced methodology and its applicability to real physiological conditions.

Influence of erythrocyte aggregation on radial migration of platelet-sized spherical particles in shear flow

Blood platelets when activated are involved in the mechanisms of hemostasis and thrombosis, and their migration toward injured vascular endothelium necessitates interaction with red blood cells (RBCs). Rheology co-factors such as a high hematocrit and a high shear rate are known to promote platelet mass transport toward the vessel wall. Hemodynamic conditions promoting RBC aggregation may also favor platelet migration, particularly in the venous system at low shear rates. The aim of this study was to confirm experimentally the impact of RBC aggregation on platelet-sized micro particle migration in a Couette flow apparatus. Biotin coated micro particles were mixed with saline or blood with different aggregation tendencies, at two shear rates of 2 and 10s^-1 and three hematocrits ranging from 20 to 60%. Streptavidin membranes were respectively positioned on the Couette static and rotating cylinders upon which the number of adhered fluorescent particles was quantified. The platelet-sized particle adhesion on both walls was progressively enhanced by increasing the hematocrit (p<0.001), reducing the shear rate (p<0.001), and rising the aggregation of RBCs (p<0.001). Particle count was minimum on the stationary cylinder when suspended in saline at 2s^-1 (57±33), and maximum on the rotating cylinder at 60% hematocrit, 2s^-1 and the maximum dextran-induced RBC aggregation (2840±152). This fundamental study is confirming recent hypotheses on the role of RBC aggregation on venous thrombosis, and may guide molecular imaging protocols requiring injecting active labeled micro particles in the venous flow system to probe human diseases.

Direct Tracking of Particles and Quantification of Margination in Blood Flow

Margination refers to the migration of particles toward blood vessel walls during blood flow. Understanding the mechanisms that lead to margination will aid in tailoring the attributes of drug-carrying particles for effective drug delivery. Most previous studies evaluated the margination propensity of these particles via an adhesion mechanism, i.e., by measuring the number of particles that adhered to the channel wall. Although particle adhesion and margination are related, adhesion also depends on other factors. In this study, we quantified the margination propensity of particles of varying diameters (0.53, 0.84, and 2.11 μm) and apparent wall shear rates (30, 61, and 121 s^-1) by directly tracking fluorescent particles flowing through a microfluidic channel. The margination parameter, M, is defined as the total number of particles found within the cell-free layers normalized by the total number of particles that passed through the channel. In this study, an M-value of 0.2 indicated no margination, which was observed for all particle sizes in water. In the case of blood, larger particles were found to have higher M-values and thus marginated more effectively than smaller particles. The corresponding M-values at the device outlet were 0.203, 0.223, and 0.285 for 0.53-, 0.84-, and 2.11-μm particles, respectively. At the inlet, the M-values for all particle sizes in blood were <0.2, suggesting that non-fully-developed flow and constriction may lead to demargination. For particle velocities transverse to the flow direction (v_y), all particle sizes showed a larger standard deviation of v_y as well as a higher effective diffusivity when the particles were suspended in blood relative to water. These higher values are attributed to collisions between the blood cells and particles, further supporting recent simulation results. In terms of flow rates, for a given particle size, the higher the flow rate, the higher the M-value.

A smart gene delivery platform: Cationic oligomer

Low transfection efficiency and high cytotoxicity of polymeric gene carriers have hampered the application of numerous polycations for gene therapy. To overcome this barrier, a cationic glycoconjugate of kanamycin and di(ethylene glycol) diacrylate was prepared via a facile approach. Nuclear magnetic resonance, Fourier transform infrared spectroscopy, and size exclusion chromatography were employed to investigate the resulting materials. Agarose gel electrophoresis, atomic force microscopy, and circular dichroism spectroscopy were used to record the interaction of the cationic oligomer and plasmid DNA. Finally, the cytotoxicity and transfection efficiency were evaluated by using COS-7 cells. The results indicated that cationic oligomers had been obtained and plasmid DNA was condensed into nanocomplexes, with a high transfection efficiency of the oligomer and a low toxicity in COS-7 cell line. It provided a novel perspective to develop gene carrier, with better safety and greater transfection efficiency, compared to traditional high molecular weight polymers.

Imaging the pharmacology of nanomaterials by intravital microscopy: Toward understanding their biological behavior

Therapeutic nanoparticles (NPs) can deliver cytotoxic chemotherapeutics and other drugs more safely and efficiently to patients; furthermore, selective delivery to target tissues can theoretically be accomplished actively through coating NPs with molecular ligands, and passively through exploiting physiological "enhanced permeability and retention" features. However, clinical trial results have been mixed in showing improved efficacy with drug nanoencapsulation, largely due to heterogeneous NP accumulation at target sites across patients. Thus, a clear need exists to better understand why many NP strategies fail in vivo and not result in significantly improved tumor uptake or therapeutic response. Multicolor in vivo confocal fluorescence imaging (intravital microscopy; IVM) enables integrated pharmacokinetic and pharmacodynamic (PK/PD) measurement at the single-cell level, and has helped answer key questions regarding the biological mechanisms of in vivo NP behavior. This review summarizes progress to date and also describes useful technical strategies for successful IVM experimentation.

Engineering approaches in siRNA delivery

siRNAs are very potent drug molecules, able to silence genes involved in pathologies development. siRNAs have virtually an unlimited therapeutic potential, particularly for the treatment of inflammatory diseases. However, their use in clinical practice is limited because of their unfavorable properties to interact and not to degrade in physiological environments. In particular they are large macromolecules, negatively charged, which undergo rapid degradation by plasmatic enzymes, are subject to fast renal clearance/hepatic sequestration, and can hardly cross cellular membranes. These aspects seriously impair siRNAs as therapeutics. As in all the other fields of science, siRNAs management can be advantaged by physical-mathematical descriptions (modeling) in order to clarify the involved phenomena from the preparative step of dosage systems to the description of drug-body interactions, which allows improving the design of delivery systems/processes/therapies. This review analyzes a few mathematical modeling approaches currently adopted to describe the siRNAs delivery, the main procedures in siRNAs vectors' production processes and siRNAs vectors' release from hydrogels, and the modeling of pharmacokinetics of siRNAs vectors. Furthermore, the use of physical models to study the siRNAs vectors' fate in blood stream and in the tissues is presented. The general view depicts a framework maybe not yet usable in therapeutics, but with promising possibilities for forthcoming applications.

Leveraging Physiology for Precision Drug Delivery

Physiological characteristics of diseases bring about both challenges and opportunities for targeted drug delivery. Various drug delivery platforms have been devised ranging from macro- to micro- and further into the nanoscopic scale in the past decades. Recently, the favorable physicochemical properties of nanomaterials, including long circulation, robust tissue and cell penetration attract broad interest, leading to extensive studies for therapeutic benefits. Accumulated knowledge about the physiological barriers that affect the in vivo fate of nanomedicine has led to more rational guidelines for tailoring the nanocarriers, such as size, shape, charge, and surface ligands. Meanwhile, progresses in material chemistry and molecular pharmaceutics generate a panel of physiological stimuli-responsive modules that are equipped into the formulations to prepare “smart” drug delivery systems. The capability of harnessing physiological traits of diseased tissues to control the accumulation of or drug release from nanomedicine has further improved the controlled drug release profiles with a precise manner. Successful clinical translation of a few nano-formulations has excited the collaborative efforts from the research community, pharmaceutical industry, and the public towards a promising future of smart drug delivery.

Red blood cells: Supercarriers for drugs, biologicals, and nanoparticles and inspiration for advanced delivery systems

Red blood cells (RBCs) constitute a unique drug delivery system as a biologic or hybrid carrier capable of greatly enhancing pharmacokinetics, altering pharmacodynamics (for example, by changing margination within the intravascular space), and modulating immune responses to appended cargoes. Strategies for RBC drug delivery systems include internal and surface loading, and the latter can be performed both ex vivo and in vivo. A relatively new avenue for RBC drug delivery is their application as a carrier for nanoparticles. Efforts are also being made to incorporate features of RBCs in nanocarriers to mimic their most useful aspects, such as long circulation and stealth features. RBCs have also recently been explored as carriers for the delivery of antigens for modulation of immune response. Therefore, RBC-based drug delivery systems represent supercarriers for a diverse array of biomedical interventions, and this is reflected by several industrial and academic efforts that are poised to enter the clinical realm.

Biomimetic carriers mimicking leukocyte plasma membrane to increase tumor vasculature permeability

Recent advances in the field of nanomedicine have demonstrated that biomimicry can further improve targeting properties of current nanotechnologies while simultaneously enable carriers with a biological identity to better interact with the biological environment. Immune cells for example employ membrane proteins to target inflamed vasculature, locally increase vascular permeability, and extravasate across inflamed endothelium. Inspired by the physiology of immune cells, we recently developed a procedure to transfer leukocyte membranes onto nanoporous silicon particles (NPS), yielding Leukolike Vectors (LLV). LLV are composed of a surface coating containing multiple receptors that are critical in the cross-talk with the endothelium, mediating cellular accumulation in the tumor microenvironment while decreasing vascular barrier function. We previously demonstrated that lymphocyte function-associated antigen (LFA-1) transferred onto LLV was able to trigger the clustering of intercellular adhesion molecule 1 (ICAM-1) on endothelial cells. Herein, we provide a more comprehensive analysis of the working mechanism of LLV in vitro in activating this pathway and in vivo in enhancing vascular permeability. Our results suggest the biological activity of the leukocyte membrane can be retained upon transplant onto NPS and is critical in providing the particles with complex biological functions towards tumor vasculature.

Self-assembled polymeric vectors mixtures: characterization of the polymorphism and existence of synergistic effects in photodynamic therapy

The objective of this work was to assess the relation between the purity of polymeric self-assemblies vectors solution and their photodynamic therapeutic efficiency. For this, several amphiphilic block copolymers of poly(ethyleneoxide-b-ε-caprolactone) have been used to form self-assemblies with different morphologies (micelles, worm-like micelles or vesicles). In a first step, controlled mixtures of preformed micelles and vesicles have been characterized both by dynamic light scattering and asymmetrical flow field flow fractionation (AsFlFFF). For this, a custom-made program, STORMS, was developed to analyze DLS data in a thorough manner by providing a large set of fitting parameters. This showed that DLS only sensed the larger vesicles when the micelles/vesicles ratio was 80/20 w/w. On the other hand, AsFlFFF allowed clear detection of the presence of micelles when this same ratio was as low as 10/90. Subsequently, the photodynamic therapy efficiency of various controlled mixtures was assessed using multicellular spheroids when a photosensitizer, pheophorbide a, was encapsulated in the polymer self-assemblies. Some mixtures were shown to be as efficient as monomorphous systems. In some cases, mixtures were found to exhibit a higher PDT efficiency compared to the individual nano-objects, revealing a synergistic effect for the efficient delivery of the photosensitizer. Polymorphous vectors can therefore be superior in therapeutic applications.

Crosslinked polymeric self-assemblies as an efficient strategy for photodynamic therapy on a 3D cell culture

Polymeric crosslinked self-assemblies based on poly(ethyleneoxide-b-ε-caprolactone) have been synthesized. They are shown to be more efficient vectors for photodynamic therapy compared to uncrosslinked systems.