On the near-wall accumulation of injectable particles in the microcirculation: smaller is not better

Mechanisms and Barriers in Nanomedicine: Progress in the Field and Future Directions

In recent years, steady progress has been made in synthesizing and characterizing engineered nanoparticles, resulting in several approved drugs and multiple promising candidates in clinical trials. Regulatory agencies such as the Food and Drug Administration and the European Medicines Agency released important guidance documents facilitating nanoparticle-based drug product development, particularly in the context of liposomes and lipid-based carriers. Even with the progress achieved, it is clear that many barriers must still be overcome to accelerate translation into the clinic. At the recent conference workshop "Mechanisms and Barriers in Nanomedicine" in May 2023 in Colorado, U.S.A., leading experts discussed the formulation, physiological, immunological, regulatory, clinical, and educational barriers. This position paper invites open, unrestricted, nonproprietary discussion among senior faculty, young investigators, and students to trigger ideas and concepts to move the field forward.

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.

Roadmap for Clinical Translation of Mobile Microrobotics

Medical microrobotics is an emerging field to revolutionize clinical applications in diagnostics and therapeutics of various diseases. On the other hand, the mobile microrobotics field has important obstacles to pass before clinical translation. This article focuses on these challenges and provides a roadmap of medical microrobots to enable their clinical use. From the concept of a "magic bullet" to the physicochemical interactions of microrobots in complex biological environments in medical applications, there are several translational steps to consider. Clinical translation of mobile microrobots is only possible with a close collaboration between clinical experts and microrobotics researchers to address the technical challenges in microfabrication, safety, and imaging. The clinical application potential can be materialized by designing microrobots that can solve the current main challenges, such as actuation limitations, material stability, and imaging constraints. The strengths and weaknesses of the current progress in the microrobotics field are discussed and a roadmap for their clinical applications in the near future is outlined.

Polystyrene microplastics induce size-dependent multi-organ damage in mice: Insights into gut microbiota and fecal metabolites

Particle size is one of the most important factors in determining the biological toxicity of microplastics (MPs). In this study, we attempted to examine the systemic toxicity of polystyrene MPs of different sizes (0.5 µm MP1 and 5 µm MP2) in C57BL/6 J mice. After the mice were given oral gavage of MPs for 8 consecutive weeks, histopathology and molecular biology assays, 16 S rRNA sequencing of the gut microbiota, and untargeted metabolomics were performed. The results showed that MPs were distributed in the organs in a size-dependent manner, with smaller particles demonstrating greater biodistribution. Further analysis indicated that exposure to MPs caused multi-organ damage through distinct toxicity pathways. Specifically, exposure to 0.5 µm MP1 led to excessive accumulation and induced more serious inflammation and mechanical damage in the spleen, kidney, heart, lung, and liver. However, 5 µm MP2 led to more severe intestinal barrier dysfunction, as well as gut dysbiosis and metabolic disorder in association with neuroinflammation. These results are helpful in expanding our knowledge of the toxicity of MPs of different sizes in mammalian models.

Using Gaussian process for velocity reconstruction after coronary stenosis applicable in positron emission particle tracking: An in-silico study

Accurate velocity reconstruction is essential for assessing coronary artery disease. We propose a Gaussian process method to reconstruct the velocity profile using the sparse data of the positron emission particle tracking (PEPT) in a biological environment, which allows the measurement of tracer particle velocity to infer fluid velocity fields. We investigated the influence of tracer particle quantity and detection time interval on flow reconstruction accuracy. Three models were used to represent different levels of stenosis and anatomical complexity: a narrowed straight tube, an idealized coronary bifurcation with stenosis, and patient-specific coronary arteries with a stenotic left circumflex artery. Computational fluid dynamics (CFD), particle tracking, and the Gaussian process of kriging were employed to simulate and reconstruct the pulsatile flow field. The study examined the error and uncertainty in velocity profile reconstruction after stenosis by comparing particle-derived flow velocity with the CFD solution. Using 600 particles (15 batches of 40 particles) released in the main coronary artery, the time-averaged error in velocity reconstruction ranged from 13.4% (no occlusion) to 161% (70% occlusion) in patient-specific anatomy. The error in maximum cross-sectional velocity at peak flow was consistently below 10% in all cases. PEPT and kriging tended to overestimate area-averaged velocity in higher occlusion cases but accurately predicted maximum cross-sectional velocity, particularly at peak flow. Kriging was shown to be useful to estimate the maximum velocity after the stenosis in the absence of negative near-wall velocity.

REVIEW: "ISCHEMIC STROKE: From Fibrinolysis to Functional Recovery" Nanomedicine: Emerging Approaches to Treat Ischemic Stroke

Stroke is responsible for 11% of all deaths worldwide, the majority of which are caused by ischemic strokes, thus making the need to urgently find safe and effective therapies. Today, these can be cured either by mechanical thrombectomy when the thrombus is accessible, or by intravenous injection of fibrinolytics. However, the latter present several limitations, such as potential severe side effects, few eligible patients and low rate of partial and full recovery. To design safer and more effective treatments, nanomedicine appeared in this medical field a few decades ago. This review will explain why nanoparticle-based therapies and imaging techniques are relevant for ischemic stroke management. Then, it will present the different nanoparticle types that have been recently developed to treat this pathology. It will also study the various targeting strategies used to bring nanoparticles to the stroke site, thereby limiting side effects and improving the therapeutic efficacy. Finally, this review will present the few clinical studies testing nanomedicine on stroke and discuss potential causes for their scarcity.

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.

Preparation of protein-loaded nanoparticles based on poly(succinimide)-oleylamine for sustained protein release: a two-step nanoprecipitation method

Currently, the treatment for acute disease encompasses the use of various biological drugs (BDs). However, the utilisation of BDs is limited due to their rapid clearance and non-specific accumulation in unwanted sites, resulting in a lack of therapeutic efficacy together with adverse effects. While nanoparticles are considered good candidates to resolve this problem, some available polymeric carriers for BDs were mainly designed for long-term sustained release. Thus, there is a need to explore new polymeric carriers for the acute disease phase that requires sustained release of BDs over a short period, for example for thrombolysis and infection. Poly(succinimide)-oleylamine (PSI-OA), a biocompatible polymer with a tuneable dissolution profile, represents a promising strategy for loading BDs for sustained release within a 48-h period. In this work, we developed a two-step nanoprecipitation method to load the model protein (e.g. bovine serum albumin and lipase) on PSI-OA. The characteristics of the nanoparticles were assessed based on various loading parameters, such as concentration, stirring rate, flow rate, volume ratio, dissolution and release of the protein. The optimised NPs displayed a size within 200 nm that is suitable for vasculature delivery to the target sites. These findings suggest that PSI-OA can be employed as a carrier for BDs for applications that require sustained release over a short period.

Potential applications of using tissue-specific EVs in targeted therapy and vaccinology

Many cell types secrete spherical membrane bodies classified as extracellular vesicles (EVs). EVs participate in intercellular communication and are present in body fluids, including blood, lymph, and cerebrospinal fluid. The time of EVs survival in the body varies depending on the body's localisation. Once the EVs reach cells, they trigger a cellular response. Three main modes of direct interaction of EVs with a target cell were described: receptor-ligand interaction mode, a direct fusion of EVs with the cellular membrane and EVs internalisation. Studies focused on the medical application of EVs. Medical application of EVs may require modification of their surface and interior. EVs surface was modified by affecting the parental cells or by the direct amendment of isolated EVs. The interior modification involved introducing materials into the cells or direct administrating isolated EVs. EVs carry proteins, lipids, fragments of DNA, mRNA, microRNA (miRNA) and long non-coding RNA. Because of EVs availability in liquid biopsy, they are potential diagnostic markers. Modified EVs could enhance the treatment of diseases such as colorectal cancer, Parkinson's disease, leukaemia or liver fibrosis. EVs have specific tissue tropisms, which makes them convenient organ-directed carriers of nucleic acids, drugs and vaccines. In conclusion, recently published works have shown that EVs could become biomarkers and modern vehicles of advanced drug forms.

Assessing Differential Particle Deformability under Microfluidic Flow Conditions

Assessing the mechanical behavior of nano- and micron-scale particles with complex shapes is fundamental in drug delivery. Although different techniques are available to quantify the bulk stiffness in static conditions, there is still uncertainty in assessing particle deformability in dynamic conditions. Here, a microfluidic chip is designed, engineered, and validated as a platform to assess the mechanical behavior of fluid-borne particles. Specifically, potassium hydroxide (KOH) wet etching was used to realize a channel incorporating a series of micropillars (filtering modules) with different geometries and openings, acting as microfilters in the direction of the flow. These filtering modules were designed with progressively decreasing openings, ranging in size from about 5 down to 1 μm. Discoidal polymeric nanoconstructs (DPNs), with a diameter of 5.5 μm and a height of 400 nm, were realized with different poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) ratios (PLGA/PEG), namely, 5:1 and 1:0, resulting in soft and rigid particles, respectively. Given the peculiar geometry of DPNs, the channel height was kept to 5 μm to limit particle tumbling or flipping along the flow. After thorough physicochemical and morphological characterization, DPNs were tested within the microfluidic chip to investigate their behavior under flow. As expected, most rigid DPNs were trapped in the first series of pillars, whereas soft DPNs were observed to cross multiple filtering modules and reach the micropillars with the smallest opening (1 μm). This experimental evidence was also supported by computational tools, where DPNs were modeled as a network of springs and beads immersed in a Newtonian fluid using the smoothed particle hydrodynamics (SPH) method. This preliminary study presents a combined experimental-computational framework to quantify, compare, and analyze the characteristics of particles having complex geometrical and mechanical attributes under flow conditions.

Antioxidant Defense in Primary Murine Lung Cells following Short- and Long-Term Exposure to Plastic Particles

Polystyrene nano- and micro-sized plastic particles (NMP) are one of the common plastic materials produced that dramatically pollute the environment, water, and oceanic habitats worldwide. NMP are continuously absorbed by the body through a number of routes, especially via intestinal ingestion, dermal uptake, and inhalation into the lung. Several studies provided evidence of NMP provoking oxidative stress and affecting cellular responses. Yet, the NMP effects on primary lung cells have not been studied. To this end, we isolated and cultured murine lung cells and exposed them short-term or long-term to polystyrene 0.2-6.0 µm-sized NMP. We studied cellular consequences regarding oxidative stress, morphology, and secretion profiling. Visualization, distribution, and expression analyses confirmed lung cells accumulating NMP and showed several significant correlations with particle size. Moreover, we found substantial evidence of biological consequences of small-scale NMP uptake in lung cells. Besides alterations of cytokine secretion profiles resulting in inflammatory responses, indicators of oxidative stress were identified that were accompanied by Nrf2 and β-catenin signaling changes. Our results serve as an important basis to point out the potential hazards of plastic contaminations and uptake in lung cells.

Tumor vascular heterogeneity and the impact of subtumoral nanoemulsion biodistribution

Aim: Investigate the heterogeneous tumor tissue organization and examine how this condition can interfere with the passive delivery of a lipid nanoemulsion in two breast cancer preclinical models (4T1 and Ehrlich). Materials & methods: The authors used in vivo image techniques to follow the nanoemulsion biodistribution and microtomography, as well as traditional histopathology and electron microscopy to evaluate the tumor structural characteristics. Results & conclusion: Lipid nanoemulsion was delivered to the tumor, vascular organization depends upon the subtumoral localization and this heterogeneous organization promotes a nanoemulsion biodistribution to the highly vascular peripherical region. Also, the results are presented with a comprehensive mathematical model, describing the differential biodistribution in two different breast cancer models, the 4T1 and Ehrlich models.

Targeted thrombolysis by magnetoacoustic particles in photothrombotic stroke model

BACKGROUND

Recombinant tissue plasminogen activator (rtPA) has a short half-life, and additional hemorrhagic transformation (HT) can occur when treatment is delayed. Here, we report the design and thrombolytic performance of 3 [Formula: see text]m discoidal polymeric particles loaded with rtPA and superparamagnetic iron oxide nanoparticles (SPIONs), referred to as rmDPPs, to address the HT issues of rtPA.

METHODS

The rmDPPs consisted of a biodegradable polymeric matrix, rtPA, and SPIONs and were synthesized via a top-down fabrication.

RESULTS

The rmDPPs could be concentrated at the target site with magnetic attraction, and then the rtPA could be released under acoustic stimulus. Therefore, we named that the particles had magnetoacoustic properties. For the in vitro blood clot lysis, the rmDPPs with magnetoacoustic stimuli could not enhance the lytic potential compared to the rmDPPs without stimulation. Furthermore, although the reduction of the infarcts in vivo was observed along with the magnetoacoustic stimuli in the rmDPPs, more enhancement was not achieved in comparison with the rtPA. A notable advantage of rmDPPs was shown in delayed administration of rmDPPs at poststroke. The late treatment of rmDPPs with magnetoacoustic stimuli could reduce the infarcts and lead to no additional HT issues, while rtPA alone could not show any favorable prognosis.

CONCLUSION

The rmDPPs may be advantageous in delayed treatment of thrombotic patients.

Shape-specific microfabricated particles for biomedical applications: a review

The storied history of controlled the release systems has evolved over time; from degradable drug-loaded sutures to monolithic zero-ordered release devices and nano-sized drug delivery formulations. Scientists have tuned the physico-chemical properties of these drug carriers to optimize their performance in biomedical/pharmaceutical applications. In particular, particle drug delivery systems at the micron size regime have been used since the 1980s. Recent advances in micro and nanofabrication techniques have enabled precise control of particle size and geometry-here we review the utility of microplates and discoidal polymeric particles for a range of pharmaceutical applications. Microplates are defined as micrometer scale polymeric local depot devices in cuboid form, while discoidal polymeric nanoconstructs are disk-shaped polymeric particles having a cross-sectional diameter in the micrometer range and a thickness in the hundreds of nanometer range. These versatile particles can be used to treat several pathologies such as cancer, inflammatory diseases and vascular diseases, by leveraging their size, shape, physical properties (e.g., stiffness), and component materials, to tune their functionality. This review highlights design and fabrication strategies for these particles, discusses their applications, and elaborates on emerging trends for their use in formulations.

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.

Targeting vascular inflammation through emerging methods and drug carriers

Acute inflammation is a common dangerous component of pathogenesis of many prevalent conditions with high morbidity and mortality including sepsis, thrombosis, acute respiratory distress syndrome (ARDS), COVID-19, myocardial and cerebral ischemia-reperfusion, infection, and trauma. Inflammatory changes of the vasculature and blood mediate the course and outcome of the pathology in the tissue site of insult, remote organs and systemically. Endothelial cells lining the luminal surface of the vasculature play the key regulatory functions in the body, distinct under normal vs. pathological conditions. In theory, pharmacological interventions in the endothelial cells might enable therapeutic correction of the overzealous damaging pro-inflammatory and pro-thrombotic changes in the vasculature. However, current agents and drug delivery systems (DDS) have inadequate pharmacokinetics and lack the spatiotemporal precision of vascular delivery in the context of acute inflammation. To attain this level of precision, many groups design DDS targeted to specific endothelial surface determinants. These DDS are able to provide specificity for desired tissues, organs, cells, and sub-cellular compartments needed for a particular intervention. We provide a brief overview of endothelial determinants, design of DDS targeted to these molecules, their performance in experimental models with focus on animal studies and appraisal of emerging new approaches. Particular attention is paid to challenges and perspectives of targeted therapeutics and nanomedicine for advanced management of acute inflammation.

The Role of in silico Research in Developing Nanoparticle-Based Therapeutics

Nanoparticles (NPs) hold great potential as therapeutics, particularly in the realm of drug delivery. They are effective at functional cargo delivery and offer a great degree of amenability that can be used to offset toxic side effects or to target drugs to specific regions in the body. However, there are many challenges associated with the development of NP-based drug formulations that hamper their successful clinical translation. Arguably, the most significant barrier in the way of efficacious NP-based drug delivery systems is the tedious and time-consuming nature of NP formulation—a process that needs to account for downstream effects, such as the onset of potential toxicity or immunogenicity, in vivo biodistribution and overall pharmacokinetic profiles, all while maintaining desirable therapeutic outcomes. Computational and AI-based approaches have shown promise in alleviating some of these restrictions. Via predictive modeling and deep learning, in silico approaches have shown the ability to accurately model NP-membrane interactions and cellular uptake based on minimal data, such as the physicochemical characteristics of a given NP. More importantly, machine learning allows computational models to predict how specific changes could be made to the physicochemical characteristics of a NP to improve functional aspects, such as drug retention or endocytosis. On a larger scale, they are also able to predict the in vivo pharmacokinetics of NP-encapsulated drugs, predicting aspects such as circulatory half-life, toxicity, and biodistribution. However, the convergence of nanomedicine and computational approaches is still in its infancy and limited in its applicability. The interactions between NPs, the encapsulated drug and the body form an intricate network of interactions that cannot be modeled with absolute certainty. Despite this, rapid advancements in the area promise to deliver increasingly powerful tools capable of accelerating the development of advanced nanoscale therapeutics. Here, we describe computational approaches that have been utilized in the field of nanomedicine, focusing on approaches for NP design and engineering.

Preparation of anisotropic multiscale micro-hydrogels via two-photon continuous flow lithography

HYPOTHESIS

Polymeric anisotropic soft microparticles show interesting behavior in biological environments and hold promise for drug delivery and biomedical applications. However, self-assembly and substrate-based lithographic techniques are limited by low resolution, batch operation or specific particle geometry and deformability. Two-photon polymerization in microfluidic channels may offer the required resolution to continuously fabricate anisotropic micro-hydrogels in sub-10 µm size-range.

EXPERIMENTS

Here, a pulsed laser source is used to perform two-photon polymerization under microfluidic flow of a poly(ethylene glycol) diacrylate (PEGDA) solution with the objective of realizing anisotropic micro-hydrogels carrying payloads of various nature, including small molecules and nanoparticles. The fabrication process is described via a reactive-convective-diffusion system of equations, whose solution under proper auxiliary conditions is used to corroborate the experimental observations and sample the configuration space.

FINDINGS

By tuning the flow velocity, exposure time and pre-polymer composition, anisotropic PEGDA micro-hydrogels are obtained in the 1-10 μm size-range and exhibit an aspect ratio varying from 1 to 5. Furthermore, 200 nm curcumin-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles and 100 nm ssRNA-encapsulating lipid nanoparticles were entrapped within square PEGDA micro-hydrogels. The proposed approach could support the fabrication of micro-hydrogels of well-defined morphology, stiffness, and surface properties for the sustained release of therapeutic agents.

Towards principled design of cancer nanomedicine to accelerate clinical translation

Nanotechnology in medical applications, especially in oncology as drug delivery systems, has recently shown promising results. However, although these advances have been promising in the pre-clinical stages, the clinical translation of this technology is challenging. To create drug delivery systems with increased treatment efficacy for clinical translation, the physicochemical characteristics of nanoparticles such as size, shape, elasticity (flexibility/rigidity), surface chemistry, and surface charge can be specified to optimize efficiency for a given application. Consequently, interdisciplinary researchers have focused on producing biocompatible materials, production technologies, or new formulations for efficient loading, and high stability. The effects of design parameters can be studied in vitro, in vivo, or using computational models, with the goal of understanding how they affect nanoparticle biophysics and their interactions with cells. The present review summarizes the advances and technologies in the production and design of cancer nanomedicines to achieve clinical translation and commercialization. We also highlight existing challenges and opportunities in the field.

Engineered strategies to enhance tumor penetration of drug-loaded nanoparticles

Nanocarriers have been widely employed in preclinical studies and clinical trials for the delivery of anticancer drugs. The most important causes of failure in clinical translation of nanocarriers is their inefficient accumulation and penetration which arises from special characteristics of tumor microenvironment such as insufficient blood supply, dense extracellular matrix, and elevated interstitial fluid pressure. Various strategies such as engineering extracellular matrix, optimizing the physicochemical properties of nanocarriers have been proposed to increase the depth of tumor penetration; however, these strategies have not been very successful so far. Novel strategies such as transformable nanocarriers, transcellular transport of peptide-modified nanocarriers, and bio-inspired carriers have recently been emerged as an advanced generation of drug carriers. In this study, the latest developments of nanocarrier-based drug delivery to solid tumor are presented with their possible limitations. Then, the prospects of advanced drug delivery systems are discussed in detail.

Study on Deposition Characteristics of Microparticles in Terminal Pulmonary Acini by IB-LBM

As an indicator of health risk, the deposition of microparticles in terminal pulmonary acini is of great significance in the medical field. To control particulate pollution and optimize aerosol delivery, it is necessary to perform an in-depth study of the microparticle deposition in terminal pulmonary acini; however, little research has been done on this topic. This paper proposes a respiratory movement model of terminal pulmonary acini using an immersed boundary–lattice Boltzmann method. In addition, we explored the effect of gravity direction, respiratory rate, microparticle diameter, and other parameters on the microparticles deposition process and distribution, under the airflow in the acinar wall. It was found that the deposition of microparticles is sensitive to gravity direction, and the growth of the respiratory rate increases the rate of microparticle migration and deposition. It was observed that the gravity effect is enhanced by increasing the diameter of microparticles, causing a high deposition and dispersion rate. The study reveals the dynamic correlation between the respiration process and the movement of microparticles, which is of reference value to figure out the pathogenicity mechanism of inhalable particles and to optimize the aerosol delivery.

Strategies for the treatment of breast cancer: from classical drugs to mathematical models

Breast cancer is one of the most common cancers and generally affects women. It is a heterogeneous disease that presents different entities, different biological characteristics, and differentiated clinical behaviors. With this in mind, this literature review had as its main objective to analyze the path taken from the simple use of classical drugs to the application of mathematical models, which through the many ongoing studies, have been considered as one of the reliable strategies, explaining the reasons why chemotherapy is not always successful. Besides, the most commonly mentioned strategies are immunotherapy, which includes techniques and therapies such as the use of antibodies, cytokines, antitumor vaccines, oncolytic and genomic viruses, among others, and nanoparticles, including metallic, magnetic, polymeric, liposome, dendrimer, micelle, and others, as well as drug reuse, which is a process by which new therapeutic indications are found for existing and approved drugs. The most commonly used pharmacological categories are cardiac, antiparasitic, anthelmintic, antiviral, antibiotic, and others. For the efficient development of reused drugs, there must be a process of exchange of purposes, methods, and information already available, and for their better understanding, computational mathematical models are then used, of which the methods of blind search or screening, based on the target, knowledge, signature, pathway or network and the mechanism to which it is directed, stand out. To conclude it should be noted that these different strategies can be applied alone or in combination with each other always to improve breast cancer treatment.

Elongated self-assembled nanocarriers: From molecular organization to therapeutic applications

Self-assembled cylindrical aggregates made of amphiphilic molecules emerged almost 40 years ago. Due to their length up to micrometers, those particles display original physico-chemical properties such as important flexibility and, for concentrated samples, a high viscoelasticity making them suitable for a wide range of industrial applications. However, a quarter of century was needed to successfully take advantage of those improvements towards therapeutic purposes. Since then, a wide diversity of biocompatible materials such as polymers, lipids or peptides, have been developed to design self-assembling elongated drug nanocarriers, suitable for therapeutic or diagnostic applications. More recently, the investigation of the main forces driving the unidirectional growth of these nanodevices allowed a translation toward the formation of pure nanodrugs to avoid the use of unnecessary side materials and the possible toxicity concerns associated.

Deformable microparticles for shuttling nanoparticles to the vascular wall

Vascular-targeted drug carriers must localize to the wall (i.e., marginate) and adhere to a diseased endothelium to achieve clinical utility. The particle size has been reported as a critical physical property prescribing particle margination in vitro and in vivo blood flows. Different transport process steps yield conflicting requirements-microparticles are optimal for margination, but nanoparticles are better for intracellular or tissue delivery. Here, we evaluate deformable hydrogel microparticles as carriers for transporting nanoparticles to a diseased vascular wall. Depending on microparticle modulus, nanoparticle-loaded poly(ethylene glycol)-based hydrogel microparticles delivered significantly more 50-nm nanoparticles to the vessel wall than freely injected nanoparticles alone, resulting in >3000% delivery increase. This work demonstrates the benefit of optimizing microparticles' efficient margination to enhance nanocarriers' transport to the vascular wall.

Vortical flow structures induced by red blood cells in capillaries

OBJECTIVE

Knowledge about the flow field of the plasma around the red blood cells in capillary flow is important for a physical understanding of blood flow and the transport of micro- and nanoparticles and molecules in the flowing plasma. We conducted an experimental study on the flow field around red blood cells in capillary flow that is complemented by simulations of vortical flow between red blood cells.

METHODS

Red blood cells were injected in a 10 × 12 µm rectangular microchannel at a low hematocrit, and the flow field around one or two cells was captured by a high-speed camera that tracked 250 nm nanoparticles in the flow field, acting as tracers.

RESULTS

While the flow field around a steady "croissant" shape is found to be similar to that of a rigid sphere, the flow field around a "slipper" shape exhibits a small vortex at the rear of the red blood cell. Even more pronounced are vortex-like structures observed in the central region between two neighboring croissants.

CONCLUSIONS

The rotation frequency of the vortices is to a good approximation, inversely proportional to the distance between the cells. Our experimental data are complemented by numerical simulations.

Advances on erythrocyte-mimicking nanovehicles to overcome barriers in biological microenvironments

Although nanocarriers offer many advantages as drug delivery systems, their poor stability in circulation, premature drug release and nonspecific uptake in non-target organs have prompted biomimetic approaches using natural cell membranes to camouflage nanovehicles. Among them, erythrocytes, representing the most abundant blood circulating cells, have been extensively investigated for biomimetic coating on artificial nanocarriers due to their upgraded biocompatibility, biodegradability, non-immunogenicity and long-term blood circulation. Due to the cell surface mimetic properties combined with customized core material, erythrocyte-mimicking nanovehicles (EM-NVs) have a wide variety of applications, including drug delivery, imaging, phototherapy, immunomodulation, sensing and detection, that foresee a huge potential for therapeutic and diagnostic applications in several diseases. In this review, we summarize the recent advances in the biomedical applications of EM-NVs in cancer, infection, heart-, autoimmune- and CNS-related disorders and discuss the major challenges and opportunities in this research area.

Development and Characterization of PLGA-Based Multistage Delivery System for Enhanced Payload Delivery to Targeted Vascular Endothelium

Vascular-targeted drug delivery remains an attractive platform for therapeutic and diagnostic interventions in human diseases. This work focuses on the development of a poly-lactic-co-glycolic-acid (PLGA)-based multistage delivery system (MDS). MDS consists of two stages: a micron-sized PLGA outer shell and encapsulated drug-loaded PLGA nanoparticles. Nanoparticles with average diameters of 76, 119, and 193 nm are successfully encapsulated into 3-6 µm MDS. Sustained in vitro release of nanoparticles from MDS is observed for up to 7 days. Both MDS and nanoparticles arebiocompatible with human endothelial cells. Sialyl-Lewis-A (sLe^A ) is successfully immobilized on the MDS and nanoparticle surfaces to enable specific targeting of inflamed endothelium. Functionalized MDS demonstrates a 2.7-fold improvement in endothelial binding compared to PLGA nanoparticles from human blood laminar flow. Overall, the presented results demonstrate successful development and characterization of MDS and suggest that MDS can serve as an effective drug carrier, which can enhance the margination of nanoparticles to the targeted vascular wall.

Effect of cytosol viscosity on the flow behavior of red blood cell suspensions in microvessels

OBJECTIVE

The flow behavior of blood is strongly affected by red blood cell (RBC) properties, such as the viscosity ratio C between cytosol and suspending medium, which can significantly be altered in several pathologies (e.g. sickle-cell disease, malaria). The main objective of this study is to understand the effect of C on macroscopic blood flow properties such as flow resistance in microvessels, and to link it to the deformation and dynamics of single RBCs.

METHODS

We employ mesoscopic hydrodynamic simulations to investigate flow properties of RBC suspensions with different cytosol viscosities for various flow conditions in cylindrical microchannels.

RESULTS

Starting from a dispersed cell configuration which approximates RBC dispersion at vessel bifurcations in the microvasculature, we find that the flow convergence and development of RBC-free layer (RBC-FL) depend only weakly on C, and require a convergence length in the range of 25D-50D, where D is channel diameter. In vessels with D ≤ 20 μ m , the final resistance of developed flow is nearly the same for C = 5 and C = 1, while for D = 40 μ m , the flow resistance for C = 5 is about 10% larger than for C = 1. The similarities and differences in flow resistance can be explained by viscosity-dependent RBC-FL thicknesses, which are associated with the viscosity-dependent dynamics of single RBCs.

CONCLUSIONS

The weak effect on the flow resistance and RBC-FL explains why RBCs can contain a high concentration of hemoglobin for efficient oxygen delivery, without a pronounced increase in the flow resistance. Furthermore, our results suggest that significant alterations in microvascular flow in various pathologies are likely not due to mere changes in cytosolic viscosity.

[Exosomes as immune regulators in head and neck cancer]

Exosomes, virus-sized nanovesicles, are utilized as messenger systems of our body to communicate with other body cells and regulate immune functions. Almost all cells produce exosomes and are able to interact with immune cells in the blood stream and peripheral body areas. Different markers on the surface of exosomes are necessary for immune cell adhesion and interaction. Furthermore, many types of exosome-immune cell interaction, such as surface receptor contact and phagocytosis, are known. As carriers of different cargos, exosomes affect different immune cell types in head and neck cancers: So far, T cells, natural killer cells, macrophages, and dendritic cells have been described in this context. For diagnostic purposes, a combined analysis of different parameters including protein amount, nucleic acid/protein expression, and the immunosuppressive impact of exosomes could empower exosomes as useful tools for evaluation of tumor promotion and progression in the future.

Exosomes released from Shiga toxin 2a-treated human macrophages modulate inflammatory responses and induce cell death in toxin receptor expressing human cells

Shiga toxins (Stxs) produced by Stx-producing Escherichia coli are the primarily virulence factors of hemolytic uremic syndrome and central nervous system (CNS) impairment. Although the precise mechanisms of toxin dissemination remain unclear, Stxs bind to extracellular vesicles (EVs). Exosomes, a subset of EVs, may play a key role in Stx-mediated renal injury. To test this hypothesis, we isolated exosomes from monocyte-derived macrophages in the presence of Stx2a or Stx2 toxoids. Macrophage-like differentiated THP-1 cells treated with Stxs secreted Stx-associated exosomes (Stx-Exo) of 90-130 nm in diameter, which induced cytotoxicity in recipient cells in a toxin receptor globotriaosylceramide (Gb₃ )-dependent manner. Stx2-Exo engulfed by Gb₃ -positive cells were translocated to the endoplasmic reticulum in the human proximal tubule epithelial cell line HK-2. Stx2-Exo contained pro-inflammatory cytokine mRNAs and proteins and induced more severe inflammation than purified Stx2a accompanied by greater death of target cells such as human renal or retinal pigment epithelial cells. Blockade of exosome biogenesis using the pharmacological inhibitor GW4869 reduced Stx2-Exo-mediated human renal cell death. Stx2-Exo isolated from human primary monocyte-derived macrophages activated caspase 3/7 and resulted in significant cell death in primary human renal cortical epithelial cells. Based on these results, we speculate that Stx-containing exosomes derived from macrophages may exacerbate cytotoxicity and inflammation and trigger cell death in toxin-sensitive cells. Therapeutic interventions targeting Stx-containing exosomes may prevent or ameliorate Stx-mediated acute vascular dysfunction.

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].

Immune cells as tumor drug delivery vehicles

This review article describes the use of immune cells as potential candidates to deliver anti-cancer drugs deep within the tumor microenvironment. First, the rationale of using drug carriers to target tumors and potentially decrease drug-related side effects is discussed. We further explain some of the current limitations when using nanoparticles for this purpose. Next, a comprehensive step-by-step description of the migration cascade of immune cells is provided as well as arguments on why immune cells can be used to address some of the limitations associated with nanoparticle-mediated drug delivery. We then describe the benefits and drawbacks of using red blood cells, platelets, granulocytes, monocytes, macrophages, myeloid-derived suppressor cells, T cells and NK cells for tumor-targeted drug delivery. An additional section discusses the versatility of nanoparticles to load anti-cancer drugs into immune cells. Lastly, we propose increasing the circulatory half-life and development of conditional release strategies as the two main future pillars to improve the efficacy of immune cell-mediated drug delivery to tumors.

DNA flowerstructure co-localizes with human pathogens in infected macrophages

Herein, we characterize the cellular uptake of a DNA structure generated by rolling circle DNA amplification. The structure, termed nanoflower, was fluorescently labeled by incorporation of ATTO488-dUTP allowing the intracellular localization to be followed. The nanoflower had a hydrodynamic diameter of approximately 300 nanometer and was non-toxic for all mammalian cell lines tested. It was internalized specifically by mammalian macrophages by phagocytosis within a few hours resulting in specific compartmentalization in phagolysosomes. Maximum uptake was observed after eight hours and the nanoflower remained stable in the phagolysosomes with a half-life of 12 h. Interestingly, the nanoflower co-localized with both Mycobacterium tuberculosis and Leishmania infantum within infected macrophages although these pathogens escape lysosomal degradation by affecting the phagocytotic pathway in very different manners. These results suggest an intriguing and overlooked potential application of DNA structures in targeted treatment of infectious diseases such as tuberculosis and leishmaniasis that are caused by pathogens that escape the human immune system by modifying macrophage biology.

Sequential deconstruction of composite drug transport in metastatic breast cancer

It is challenging to design effective drug delivery systems (DDS) that target metastatic breast cancers (MBC) because of lack of competent imaging and image analysis protocols that suitably capture the interactions between DDS and metastatic lesions. Here, we integrate high temporal resolution of in vivo whole-body PET-CT, ex vivo whole-organ optical imaging, high spatial resolution of confocal microscopy, and mathematical modeling, to systematically deconstruct the trafficking of injectable nanoparticle generators encapsulated with polymeric doxorubicin (iNPG-pDox) in pulmonary MBC. iNPG-pDox accumulated substantially in metastatic lungs, compared to healthy lungs. Intratumoral distribution and retention of iNPG-pDox varied with lesion size, possibly induced by locally remodeled microenvironment. We further used multiscale imaging and mathematical simulations to provide improved drug delivery strategies for MBC. Our work presents a multidisciplinary translational toolbox to evaluate transport and interactions of DDS within metastases. This knowledge can be recursively applied to rationally design advanced therapies for metastatic cancers.

Multi-objective optimization of tumor response to drug release from vasculature-bound nanoparticles

The pharmacokinetics of nanoparticle-borne drugs targeting tumors depends critically on nanoparticle design. Empirical approaches to evaluate such designs in order to maximize treatment efficacy are time- and cost-intensive. We have recently proposed the use of computational modeling of nanoparticle-mediated drug delivery targeting tumor vasculature coupled with numerical optimization to pursue optimal nanoparticle targeting and tumor uptake. Here, we build upon these studies to evaluate the effect of tumor size on optimal nanoparticle design by considering a cohort of heterogeneously-sized tumor lesions, as would be clinically expected. The results indicate that smaller nanoparticles yield higher tumor targeting and lesion regression for larger-sized tumors. We then augment the nanoparticle design optimization problem by considering drug diffusivity, which yields a two-fold tumor size decrease compared to optimizing nanoparticles without this consideration. We quantify the tradeoff between tumor targeting and size decrease using bi-objective optimization, and generate five Pareto-optimal nanoparticle designs. The results provide a spectrum of treatment outcomes - considering tumor targeting vs. antitumor effect - with the goal to enable therapy customization based on clinical need. This approach could be extended to other nanoparticle-based cancer therapies, and support the development of personalized nanomedicine in the longer term.

Image-guided mathematical modeling for pharmacological evaluation of nanomaterials and monoclonal antibodies

While plasma concentration kinetics has traditionally been the predictor of drug pharmacological effects, it can occasionally fail to represent kinetics at the site of action, particularly for solid tumors. This is especially true in the case of delivery of therapeutic macromolecules (drug-loaded nanomaterials or monoclonal antibodies), which can experience challenges to effective delivery due to particle size-dependent diffusion barriers at the target site. As a result, disparity between therapeutic plasma kinetics and kinetics at the site of action may exist, highlighting the importance of target site concentration kinetics in determining the pharmacodynamic effects of macromolecular therapeutic agents. Assessment of concentration kinetics at the target site has been facilitated by non-invasive in vivo imaging modalities. This allows for visualization and quantification of the whole-body disposition behavior of therapeutics that is essential for a comprehensive understanding of their pharmacokinetics and pharmacodynamics. Quantitative non-invasive imaging can also help guide the development and parameterization of mathematical models for descriptive and predictive purposes. Here, we present a review of the application of state-of-the-art imaging modalities for quantitative pharmacological evaluation of therapeutic nanoparticles and monoclonal antibodies, with a focus on their integration with mathematical models, and identify challenges and opportunities. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Diagnostic Tools > in vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

A mathematical model to predict nanomedicine pharmacokinetics and tumor delivery

Towards clinical translation of cancer nanomedicine, it is important to systematically investigate the various parameters related to nanoparticle (NP) physicochemical properties, tumor characteristics, and inter-individual variability that affect the tumor delivery efficiency of therapeutic nanomaterials. Comprehensive investigation of these parameters using traditional experimental approaches is impractical due to the vast parameter space; mathematical models provide a more tractable approach to navigate through such a multidimensional space. To this end, we have developed a predictive mathematical model of whole-body NP pharmacokinetics and their tumor delivery in vivo, and have conducted local and global sensitivity analyses to identify the factors that result in low tumor delivery efficiency and high off-target accumulation of NPs. Our analyses reveal that NP degradation rate, tumor blood viscosity, NP size, tumor vascular fraction, and tumor vascular porosity are the key parameters in governing NP kinetics in the tumor interstitium. The impact of these parameters on tumor delivery efficiency of NPs is discussed, and optimal values for maximizing NP delivery are presented.

Understanding nanoparticle flow with a new in vitro experimental and computational approach using hydrogel channels

Nanoparticles (NPs) are considered as one of the most promising drug delivery vehicles and a next-generation solution for current medical challenges. In this context, variables related to flow of NPs such as the quantity of NPs lost during transport and flow trajectory greatly affect the clinical efficiency of NP drug delivery systems. Currently, there is little knowledge of the physical mechanisms dominating NP flow inside the human body due to the limitations of available experimental tools for mimicking complex physiological environments at the preclinical stage. Here, we report a coupled experimental and computational fluid dynamics (CFD)-based novel in vitro approach to predict the flow velocity and binding of NP drug delivery systems during transport through vasculature. Poly(hydroxyethyl)methacrylate hydrogels were used to form soft cylindrical constructs mimicking vascular sections as flow channels for synthesized iron oxide NPs in these first-of-its-kind transport experiments. Brownian dynamics and material of the flow channels played key roles in NP flow, based on the measurements of NP flow velocity over seven different mass concentrations. A fully developed laminar flow of the NPs under these conditions was simultaneously predicted using CFD. Results from the mass loss of NPs during flow indicated a diffusion-dominated flow at higher particle concentrations but a flow controlled by the surrounding fluid and Brownian dynamics at the lowest NP concentrations. The CFD model predicted a mass loss of 1.341% and 6.253% for the 4.12 g·mL^-1 and 2.008 g·mL^-1 inlet mass concentrations of the NPs, in close confirmation with the experimental results. This further highlights the reliability of our new in vitro technique in providing mechanistic insights of NP flow for potential preclinical stage applications.

A multiscale subvoxel perfusion model to estimate diffusive capillary wall conductivity in multiple sclerosis lesions from perfusion MRI data

We propose a new mathematical model to learn capillary leakage coefficients from dynamic susceptibility contrast MRI data. To this end, we derive an embedded mixed-dimension flow and transport model for brain tissue perfusion on a subvoxel scale. This model is used to obtain the contrast agent concentration distribution in a single MRI voxel during a perfusion MRI sequence. We further present a magnetic resonance signal model for the considered sequence including a model for local susceptibility effects. This allows modeling MR signal-time curves that can be compared with clinical MRI data. The proposed model can be used as a forward model in the inverse modeling problem of inferring model parameters such as the diffusive capillary wall conductivity. Acute multiple sclerosis lesions are associated with a breach in the integrity of the blood-brain barrier. Applying the model to perfusion MR data of a patient with acute multiple sclerosis lesions, we conclude that diffusive capillary wall conductivity is a good indicator for characterizing activity of lesions, even if other patient-specific model parameters are not well-known.

Advances in mathematical models of the active targeting of tumor cells by functional nanoparticles

BACKGROUND AND OBJECTIVE

The process of nanoparticles (NPs) entering blood circulation to actively target tumor cells involves four stages-the transport of NPs in blood vessels, transvascular transport of NPs, transport of NPs in the tumor interstitial matrix and entry of NPs into tumor cells. These four stages are a complex process involving mechanical, physical, biochemical, and biophysical factors, the tumor microenvironment (TME) and properties of NPs play important roles in this process. Because this process involves a large number of factors and is very complex, it is difficult to study with conventional methods.

METHODS

Using mathematical models for simulation is suitable for addressing this complex situation and can describe the complexity well.

RESULTS

This work focuses on the theoretical simulation of NPs that target tumor cells to illustrate the effects of the abnormal microenvironment of tumors and properties of NPs on the transport process. Mathematical models constructed by different methods are enumerated. Through studying these mathematical models, different methods to overcome nanoparticle (NP) transport obstacles are illustrated.

CONCLUSIONS

It is necessary to construct a theoretical model of active targeting nanodrug delivery under the coupling of micro-flow field and specific binding force field, and to simulate and analyze the delivery process at mesoscopic scale using computational fluid dynamics (CFD) method, so as to reveal the law and characteristics of drug delivery and cell uptake in the micro-environment of tumors in vivo. The methods and techniques discussed can serve as the basis for systematic studies of active targeting of functional nanoparticles to tumor cells.

Intravital Vascular Phototheranostics and Real-Time Circulation Dynamics of Micro- and Nanosized Erythrocyte-Derived Carriers

Erythrocyte-based carriers can serve as theranostic platforms for delivery of imaging and therapeutic payloads. Engineering these carriers at micro- or nanoscales makes them potentially useful for broad clinical applications ranging from vascular diseases to tumor theranostics. Longevity of these carriers in circulation is important in delivering a sufficient amount of their payloads to the target. We have investigated the circulation dynamics of micro (∼4.95 μm diameter) and nano (∼91 nm diameter) erythrocyte-derived carriers in real time using near-infrared fluorescence imaging, and evaluated the effectiveness of such carrier systems in mediating photothermolysis of cutaneous vasculature in mice. Fluorescence emission half-lives of micro- and nanosized carriers in response to a single intravenous injection were ∼49 and ∼15 min, respectively. A single injection of microsized carriers resulted in a 3-fold increase in signal-to-noise ratio that remained nearly persistent over 1 h of imaging time. Our results also suggest that a second injection of the carriers 7 days later can induce a transient inflammatory response, as manifested by the apparent leakage of the carriers into the perivascular tissue. The administration of the carriers into the mice vasculature reduced the threshold laser fluence to induce photothermolysis of blood vessels from >65 to 20 J/cm². We discuss the importance of membrane physicochemical and mechanical characteristics in engineering erythrocyte-derived carriers and considerations for their clinical translation.

Improving nanotherapy delivery and action through image-guided systems pharmacology

Despite recent advances in the translation of therapeutic nanoparticles (TNPs) into the clinic, the field continues to face challenges in predictably and selectively delivering nanomaterials for the treatment of solid cancers. The concept of enhanced permeability and retention (EPR) has been coined as a convenient but simplistic descriptor of high TNP accumulation in some tumors. However, in practice EPR represents a number of physiological variables rather than a single one (including dysfunctional vasculature, compromised lymphatics and recruited host cells, among other aspects of the tumor microenvironment) — each of which can be highly heterogenous within a given tumor, patient and across patients. Therefore, a clear need exists to dissect the specific biophysical factors underlying the EPR effect, to formulate better TNP designs, and to identify patients with high-EPR tumors who are likely to respond to TNP. The overall pharmacology of TNP is governed by an interconnected set of spatially defined and dynamic processes that benefit from a systems-level quantitative approach, and insights into the physiology have profited from the marriage between in vivo imaging and quantitative systems pharmacology (QSP) methodologies. In this article, we review recent developments pertinent to image-guided systems pharmacology of nanomedicines in oncology. We first discuss recent developments of quantitative imaging technologies that enable analysis of nanomaterial pharmacology at multiple spatiotemporal scales, and then examine reports that have adopted these imaging technologies to guide QSP approaches. In particular, we focus on studies that have integrated multi-scale imaging with computational modeling to derive insights about the EPR effect, as well as studies that have used modeling to guide the manipulation of the EPR effect and other aspects of the tumor microenvironment for improving TNP action. We anticipate that the synergistic combination of imaging with systems-level computational methods for effective clinical translation of TNPs will only grow in relevance as technologies increase in resolution, multiplexing capability, and in the ability to examine heterogeneous behaviors at the single-cell level.

Anisotropic nanomaterials for shape-dependent physicochemical and biomedical applications

This review contributes towards a systematic understanding of the mechanism of shape-dependent effects on nanoparticles (NPs) for elaborating and predicting their properties and applications based on the past two decades of research. Recently, the significance of shape-dependent physical chemistry and biomedicine has drawn ever increasing attention. While there has been a great deal of effort to utilize NPs with different morphologies in these fields, so far research studies are largely localized in particular materials, synthetic methods, or biomedical applications, and have ignored the interactional and interdependent relationships of these areas. This review is a comprehensive description of the NP shapes from theory, synthesis, property to application. We figure out the roles that shape plays in the properties of different kinds of nanomaterials together with physicochemical and biomedical applications. Through systematic elaboration of these shape-dependent impacts, better utilization of nanomaterials with diverse morphologies would be realized and definite strategies would be expected for breakthroughs in these fields. In addition, we have proposed some critical challenges and open problems that need to be addressed in nanotechnology.

Characteristics and roles of extracellular vesicles released by epidermal keratinocytes

Keratinocytes, which constitute 90% of the cells in the epidermis of the skin, have been demonstrated to communicate with other skin cells such as fibroblasts, melanocytes and immune cells through extracellular vesicles (EVs). This communication is facilitated by the enriched EV biomolecular cargo which regulates multiple biological processes within skin tissue, including cell proliferation, cell migration, anti-apoptosis, pigmentation transfer and extracellular matrix remodelling. This review will provide an overview of the current literature and advances in the field of keratinocyte-derived EV research with particular regard to the interactions and communication between keratinocytes and other skin cells, mediated by EVs and EV components. Importantly, this information may shed some light on the potential for keratinocyte-derived EVs in future biomedical studies.

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.