Effects of shear stress on the cellular distribution of polystyrene nanoparticles in a biomimetic microfluidic system

Transient fluid flow improves photoimmunoconjugate delivery and photoimmunotherapy efficacy

Circulating drugs in the peritoneal cavity is an effective strategy for advanced ovarian cancer treatment. Photoimmunotherapy, an emerging modality with potential for the treatment of ovarian cancer, involves near-infrared light activation of antibody-photosensitizer conjugates (photoimmunoconjugates) to generate cytotoxic reactive oxygen species. Here, a microfluidic cell culture model is used to study how fluid flow-induced shear stress affects photoimmunoconjugate delivery to ovarian cancer cells. Photoimmunoconjugates are composed of the antibody, cetuximab, conjugated to the photosensitizer, and benzoporphyrin derivative. Longitudinal tracking of photoimmunoconjugate treatment under flow conditions reveals enhancements in subcellular photosensitizer accumulation. Compared to static conditions, fluid flow-induced shear stress at 0.5 and 1 dyn/cm2 doubled the cellular delivery of photoimmunoconjugates. Fluid flow-mediated treatment with three different photosensitizer formulations (benzoporphyrin derivative, photoimmunoconjugates, and photoimmunoconjugate-coated liposomes) led to enhanced phototoxicity compared to static conditions. This study confirms the fundamental role of fluid flow-induced shear stress in the anti-cancer effects of photoimmunotherapy.

Isolation of biofluids from tissues using a vacuum-assisted filtration biomedical device

A biopsy is usually used to remove a piece of tissue from a patient for laboratory testing. The interstitial fluid is taken out at the same time as the tissue sample. Since interstitial fluid flows between cells and capillaries in tissues, similar to blood plasma, it is necessary to separate interstitial fluid from tissues in order to study them separately. Vacuum blood sampling has been used to draw blood into vacuum-sealed tubes, while interstitial fluid can be removed directly from the skin using microneedles with standard pumps. However, no methods are available to separate blood or interstitial fluid from the tissue itself for molecular characterization. In this study, we designed a biomedical device that can separate interstitial fluid from tissue using a vacuum-assisted filtration method. The device has a chamber that collects fluid extracted from the tissue that remains on top of the filter. We characterized the weight change and glycan profiles of tissues before and after vacuum-assisted filtration. The results demonstrate that the biomedical device can remove interstitial fluid and facilitate the analysis of tissue-specific molecules while minimizing information from the interstitial fluid.

Shear stress regulation of nanoparticle uptake in vascular endothelial cells

Nanoparticles (NPs) hold tremendous targeting potential in cardiovascular disease and regenerative medicine, and exciting clinical applications are coming into light. Vascular endothelial cells (ECs) exposure to different magnitudes and patterns of shear stress (SS) generated by blood flow could engulf NPs in the blood. However, an unclear understanding of the role of SS on NP uptake is hindering the progress in improving the targeting of NP therapies. Here, the temporal and spatial distribution of SS in vascular ECs and the effect of different SS on NP uptake in ECs are highlighted. The mechanism of SS affecting NP uptake through regulating the cellular ROS level, endothelial glycocalyx and membrane fluidity is summarized, and the molecules containing clathrin and caveolin in the engulfment process are elucidated. SS targeting NPs are expected to overcome the current bottlenecks and change the field of targeting nanomedicine. This assessment on how SS affects the cell uptake of NPs and the marginalization of NPs in blood vessels could guide future research in cell biology and vascular targeting drugs.

Biomechanics and mechanobiology of the bone matrix

The bone matrix plays an indispensable role in the human body, and its unique biomechanical and mechanobiological properties have received much attention. The bone matrix has unique mechanical anisotropy and exhibits both strong toughness and high strength. These mechanical properties are closely associated with human life activities and correspond to the function of bone in the human body. None of the mechanical properties exhibited by the bone matrix is independent of its composition and structure. Studies on the biomechanics of the bone matrix can provide a reference for the preparation of more applicable bone substitute implants, bone biomimetic materials and scaffolds for bone tissue repair in humans, as well as for biomimetic applications in other fields. In providing mechanical support to the human body, bone is constantly exposed to mechanical stimuli. Through the study of the mechanobiology of the bone matrix, the response mechanism of the bone matrix to its surrounding mechanical environment can be elucidated and used for the health maintenance of bone tissue and defect regeneration. This paper summarizes the biomechanical properties of the bone matrix and their biological significance, discusses the compositional and structural basis by which the bone matrix is capable of exhibiting these mechanical properties, and studies the effects of mechanical stimuli, especially fluid shear stress, on the components of the bone matrix, cells and their interactions. The problems that occur with regard to the biomechanics and mechanobiology of the bone matrix and the corresponding challenges that may need to be faced in the future are also described.

Characterization of MXene as a Cancer Photothermal Agent Under Physiological Conditions

A growing interest has recently emerged in the use of nanomaterials in medical applications. Nanomaterials, such as MXene, have unique properties due to their 2D ultra-thin structure, which is potentially useful in cancer photothermal therapy. To be most effective, photothermal agents need to be internalized by the cancer cells. In this study, MXene was fabricated using chemical reactions and tested as a photothermal agent on MDA-231 breast cancer cells under static and physiological conditions. Fluid shear stress (∼0.1 Dyn/cm2) was applied using a perfusion system to mimic the physiological tumor microenvironment. The uptake of MXene was analyzed under fluid flow compared to static culture using confocal microscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and transmission electron microscopy (TEM). Furthermore, a viability assay was used to assess cell’s survival after exposing the treated cells to photothermal laser at different power densities and durations. We showed that when incubated with cancer cells, 2D MXene nanoparticles were successfully internalized into the cells resulting in increased intracellular temperatures when exposed to NIR laser. Interestingly, dynamic culture alone did not result in a significant increase in uptake suggesting the need for surface modifications for enhanced cellular uptake under shear stress.

Recent Developments in Nanomaterial-Based Shear-Sensitive Drug Delivery Systems

Nanomaterial-based drug delivery systems (DDSs) increase the efficacy of various therapeutics, and shear stress has been shown to be a robust modulator of payload release. In the past few decades, a deeper understanding has been gained of the effects of flow in the body and its alteration in pathological microenvironments. More recently, shear-responsive nanomaterial DDSs have been developed. Studies on this subject mainly from the last decade are reviewed here, focusing on innovations of the material design and mechanisms of the shear response. The two most popular shear-controlled drug carriers distinguished by different release mechanisms, that is, shear-deformable nanoparticles (NPs) and shear-dissociated NP aggregates (NPAs), are surveyed. The influence of material structures on their properties such as drug loading, circulation time, and shear sensitivity are discussed. The drug development stages, therapeutic effects, limitations, and potential of these DDSs are further inspected. The reviewed research emphasizes the advantages and significance of nanomaterial-based shear-sensitive DDSs in the field of targeted drug delivery. It is also believed that efforts to rationally design nanomaterial DDSs responsive to shear may prompt a new class of diagnostics and therapeutics for signaling and rectifying pathological flows in the body.

Dynamic placenta-on-a-chip model for fetal risk assessment of nanoparticles intended to treat pregnancy-associated diseases

Pregnant women often have to take medication either for pregnancy-related diseases or for previously existing medical conditions. Current maternal medications pose fetal risks due to off target accumulation in the fetus. Nanoparticles, engineered particles in the nanometer scale, have been used for targeted drug delivery to the site of action without off-target effects. This has opened new avenues for treatment of pregnancy-associated diseases while minimizing risks on the fetus. It is therefore instrumental to study the potential transfer of nanoparticles from the mother to the fetus. Due to limitations of in vivo and ex vivo models, an in vitro model mimicking the in vivo situation is essential. Placenta-on-a-chip provides a microphysiological recapitulation of the human placenta. Here, we reviewed the fetal risks associated with current therapeutic approaches during pregnancy, analyzed the advantages and limitations of current models used for nanoparticle assessment, and highlighted the current need for using dynamic placenta-on-a-chip models for assessing the safety of novel nanoparticle-based therapies during pregnancy.

Dual-targeting nanovesicles enhance specificity to dynamic tumor cells in vitro and in vivo via manipulation of αvβ3-ligand binding

The dynamic or flowing tumor cells just as leukemia cells and circulating tumor cells face a microenvironment difference from the solid tumors, and the related targeting nanomedicines are rarely reported. The existence of fluidic shear stress in blood circulation seems not favorable for the binding of ligand modified nanodrugs with their target receptor. Namely, the binding feature is very essential in this case. Herein, we utilized HSPC, PEG-DSPE, cholesterol and two αvβ3 ligands (RGDm7 and DT4) with different binding rates to build dual-targeting nanovesicles, in an effort to achieve a “fast-binding/slow-unbinding” function. It was demonstrated that the dual-targeting nanovesicles actualized efficient cellular uptake and antitumor effect in vitro both for static and dynamic tumor cells. Besides, the potency of the dual-targeting vesicles for flowing tumor cells was better than that for static tumor cells. Then, a tumor metastasis mice model and a leukemia mice model were established to detect the killing ability of the drug-loaded dual-targeting vesicles to dynamic tumor cells in vivo. The therapy efficacy of the dual-targeting system was higher than other controls including single-targeting ones. Generally, it seems possible to strengthen drug-targeting to dynamic tumor cells via the control of ligand–receptor interaction.

Anlar G, A. Hussein E, Elzatahry A, C. Yalcin H. Effect of Flow-Induced Shear Stress in Nanomaterial Uptake by Cells: Focus on Targeted Anti-Cancer Therapy

Recently, nanomedicines have gained a great deal of attention in diverse biomedical applications, including anti-cancer therapy. Being different from normal tissue, the biophysical microenvironment of tumor cells and cancer cell mechanics should be considered for the development of nanostructures as anti-cancer agents. Throughout the last decades, many efforts devoted to investigating the distinct cancer environment and understanding the interactions between tumor cells and have been applied bio-nanomaterials. This review highlights the microenvironment of cancer cells and how it is different from that of healthy tissue. We gave special emphasis to the physiological shear stresses existing in the cancerous surroundings, since these stresses have a profound effect on cancer cell/nanoparticle interaction. Finally, this study reviews relevant examples of investigations aimed at clarifying the cellular nanoparticle uptake behavior under both static and dynamic conditions.

Shear Stress-Dependent Targeting Efficiency Using Self-Assembled Gelatin-Oleic Nanoparticles in a Biomimetic Microfluidic System

Cellular properties and microenvironments, as well as the characteristics of nanoparticles (NPs), affect the cellular uptake and cytotoxic effects of drug-loaded NPs. Since there is fluid flow in the human blood system, fluid flow also affects the drug delivery efficiency of NPs. This study aimed to evaluate the cellular behaviors of drug-loaded soft NPs on A549 cancer cells under different levels of shear stress (0.5, 5, and 50 dynes/cm²) in the biomimetic microfluidic system. The soft self-assembled NPs were formed by the gelatin-oleic conjugate (GOC). The poorly water-soluble coumarin-6 or paclitaxel (PTX) were used as model markers for encapsulation within self-assembled NPs (C-GONs or PTX-GONs, respectively). The cellular uptake of C-GONs was found to be improved with shear-stress dependence. The inhibitory concentration (IC₅₀) of PTX-GONs at 0.5, 5, and 50 dynes/cm² was 0.106 µg/mL, 0.108 µg/mL, and 0.091 µg/mL, respectively, as compared to 0.138 µg/mL in a static condition. The cell killing efficiency of PTX-GONs was increased in the highest shear stress of 50 dynes/cm² in the static condition, and other levels of shear stress in dynamic conditions.

Effect of fluid shear stress on the internalization of kidney-targeted delivery systems in renal tubular epithelial cells

Renal tubular epithelial cells (RTECs) are important target cells for the development of kidney-targeted drug delivery systems. Under physiological conditions, RTECs are under constant fluid shear stress (FSS) from original urine in the renal tubule and respond to changes of FSS by altering their morphology and receptor expression patterns, which may affect reabsorption and cellular uptake. Using a microfluidic system, controlled shear stress was applied to proximal tubule epithelial cell line HK-2. Next, 2-glucosamine, bovine serum albumin, and albumin nanoparticles were selected as representative carriers to perform cell uptake studies in HK-2 cells using the microfluidic platform system with controlled FSS. FSS is proven to impact the morphology of HK-2 cells and upregulate the levels of megalin and clathrin, which then led to enhanced cellular uptake efficiencies of energy-driven carrier systems such as macromolecular and albumin nanoparticles in HK-2 cells. To further investigate the effects of FSS on endocytic behavior mediated by related receptors, a mice model of acute kidney injury with reduced fluid shear stress was established. Consistent with in vitro findings, in vivo studies have also shown reduced fluid shear stress down-regulated the levels of megalin receptors, thereby reducing the renal distribution of albumin nanoparticles.

Combinatory interpretation of protein corona and shear stress for active cancer targeting of bioorthogonally clickable gelatin-oleic nanoparticles

Nanoparticle-protein interactions under conditions mimicking physiology determine how nanoparticles (NPs) will behave inside blood vessels and, therefore, the overall outcome of the drug-delivery system. Here, for the first time, we explore the effects of bio-mimicking shear stress and protein corona conditions on novel active targeting of clickable fattigation nanoparticles (NPs) for cancer therapy. Active targeting dibenzocyclooctyne-functionalized biocompatible gelatin-oleic NPs (GON-DBCOs) via a bioorthogonal click reaction were prepared by the desolvation method for delivery of docetaxel (DTX) to lung and breast cancer models. The effect of shear stress (5 dyne/cm²) and human serum albumin (HSA) protein corona on the cellular behavior of NPs was explored under a dynamic microfluidic system in lung (A549) and breast (MCF-7) cancer cell lines. The developed drug-loaded NPs had a particle size of 300 nm, a narrow size distribution, positive zeta potential, high encapsulation efficacy (72.4%), and spherical morphology. The particle size of the protein corona-coated NPs increased to 341 nm with a negative zeta potential. The inhibitory dose (IC₅₀) increased approximately 3- and 42-fold in A549 and MCF-7 cells, respectively, under dynamic microfluidic conditions compared to static conditions. Cellular uptake was significantly decreased in the presence of shear stress and a protein corona, compared with static conditions, in both lung (A549, **p < 0.01) and breast (MCF-7, *p < 0.05) cancer cell lines. Clathrin-and energy-dependent pathways were found to be involved in the cellular uptake of NPs. This study could serve as a vital tool for the evaluation of NPs under aggressive bio-mimicking conditions comprising shear stress and a protein corona to predict the in vivo performance of NPs and support the preclinical and clinical translation of NP drug delivery systems.

Vascular endothelial cell mechanosensing: New insights gained from biomimetic microfluidic models

In vivo, cells of the vascular system are subjected to various mechanical stimuli and have demonstrated the ability to adapt their behavior via mechanotransduction. Recent advances in microfluidic and "on-chip" techniques have provided the technology to study these alterations in cell behavior. Contrary to traditional in vitro assays such as transwell plates and parallel plate flow chambers, these microfluidic devices (MFDs) provide the opportunity to integrate multiple mechanical cues (e.g. shear stress, confinement, substrate stiffness, vessel geometry and topography) with in situ quantification capabilities. As such, MFDs can be used to recapitulate the in vivo mechanical setting and systematically vary microenvironmental conditions for improved mechanobiological studies of the endothelium. Additionally, adequate modelling provides for enhanced understanding of disease progression, design of cell separation and drug delivery systems, and the development of biomaterials for tissue engineering applications. Here, we will discuss the advances in knowledge about endothelial cell mechanosensing resulting from the design and application of biomimetic on-chip and microfluidic platforms.

Current Challenges toward In Vitro Cellular Validation of Inorganic Nanoparticles

An impressive development has been achieved toward the production of well-defined "smart" inorganic nanoparticles, in which the physicochemical properties can be controlled and predicted to a high degree of accuracy. Nanoparticle design is indeed highly advanced, multimodal and multitargeting being the norm, yet we do not fully understand the obstacles that nanoparticles face when used in vivo. Increased cooperation between chemists and biochemists, immunologists and physicists, has allowed us to think outside the box, and we are slowly starting to understand the interactions that nanoparticles undergo under more realistic situations. Importantly, such an understanding involves awareness about the limitations when assessing the influence of such inorganic nanoparticles on biological entities and vice versa, as well as the development of new validation strategies.