Inflamed leukocyte-mimetic nanoparticles for molecular imaging of inflammation

Biomimetic Integrated Nanozyme for Flare and Recurrence of Gouty Arthritis

Flare and multiple recurrences pose significant challenges in gouty arthritis. Traditional treatments provide temporary relief from inflammation but fail to promptly alleviate patient pain or effectively prevent subsequent recurrences. It should also be noted that both anti-inflammation and metabolism of uric acid are necessary for gouty arthritis, calling for therapeutic systems to achieve these two goals simultaneously. In this study, we propose a biomimetic integrated nanozyme, HMPB-Pt@MM, comprising platinum nanozyme and hollow Prussian blue. It demonstrates anti-inflammatory properties by eliminating reactive oxygen species and reducing infiltration of inflammatory macrophages. Additionally, it rapidly targets inflamed ankles through the camouflage of macrophage membranes. Furthermore, HMPB-Pt@MM exhibits urate oxidase-like capabilities, continuously metabolizing locally elevated uric acid concentrations, ultimately inhibiting multiple recurrences of gouty arthritis. In summary, HMPB-Pt@MM integrates ROS clearance with uric acid metabolism, offering a promising platform for the treatment of gouty arthritis.

Drug Delivery Angle for Various Atherosclerosis and Aneurysm Percentages of the Carotid Artery

Stroke is the second cause of mortality among adult males and the first cause of death in adult females all around the world. It is also recognized as one of the most important causes of morbidity and dementia in adults. Stenosis or rupture of the only channels of the blood supply from the heart to the brain (carotid arteries) is among the main causes of stroke. In this regard, treatment of the lesions of carotid arteries, including atherosclerosis and aneurysm, could be a huge step in preventing stroke and improving brain performance. Targeted drug delivery by drug-carrying nanoparticles is the latest method for optimal delivery of drug to the damaged parts of the artery. In this study, a wide range of carotid artery lesions, including different percentages of atherosclerosis and aneurysm, were considered. After analyzing the dynamics of the fluid flow in different damaged regions and selecting the magnetic framework with proper ligand (Fe3O4@MOF) as the drug carrier, the size of the particles and their number per cycle were analyzed. Based on the results, the particle size of 100 nm and the use of 300 particles per injection at each cardiac cycle can result in maximum drug delivery to the target site. Then, the effect of the hospital bed angle on drug delivery was investigated. The results showed a unique optimal drug delivery angle for each extent of atherosclerosis or aneurysm. For example, in a 50% aneurysm, drug delivery at an angle of 30° is about 387% higher than that at an angle of 15°. Finally, simulation of real geometry indicated the effectiveness of simple geometry instead of real geometry for the simulation of carotid arteries, which can remarkably decrease the computational time and costs.

Nanocrystals for Deep-Tissue In Vivo Luminescence Imaging in the Near-Infrared Region

In vivo imaging technologies have emerged as a powerful tool for both fundamental research and clinical practice. In particular, luminescence imaging in the tissue-transparent near-infrared (NIR, 700-1700 nm) region offers tremendous potential for visualizing biological architectures and pathophysiological events in living subjects with deep tissue penetration and high imaging contrast owing to the reduced light-tissue interactions of absorption, scattering, and autofluorescence. The distinctive quantum effects of nanocrystals have been harnessed to achieve exceptional photophysical properties, establishing them as a promising category of luminescent probes. In this comprehensive review, the interactions between light and biological tissues, as well as the advantages of NIR light for in vivo luminescence imaging, are initially elaborated. Subsequently, we focus on achieving deep tissue penetration and improved imaging contrast by optimizing the performance of nanocrystal fluorophores. The ingenious design strategies of NIR nanocrystal probes are discussed, along with their respective biomedical applications in versatile in vivo luminescence imaging modalities. Finally, thought-provoking reflections on the challenges and prospects for future clinical translation of nanocrystal-based in vivo luminescence imaging in the NIR region are wisely provided.

Recent advance in treatment of atherosclerosis: Key targets and plaque-positioned delivery strategies

Atherosclerosis, a chronic inflammatory disease of vascular wall, is a progressive pathophysiological process with lipids oxidation/depositing initiation and innate/adaptive immune responses. The coordination of multi systems covering oxidative stress, dysfunctional endothelium, diseased lipid uptake, cell apoptosis, thrombotic and pro-inflammatory responding as well as switched SMCs contributes to plaque growth. In this circumstance, inevitably, targeting these processes is considered to be effective for treating atherosclerosis. Arriving, retention and working of payload candidates mediated by targets in lesion direct ultimate therapeutic outcomes. Accumulating a series of scientific studies and clinical practice in the past decades, lesion homing delivery strategies including stent/balloon/nanoparticle-based transportation worked as the potent promotor to ensure a therapeutic effect. The objective of this review is to achieve a very brief summary about the effective therapeutic methods cooperating specifical targets and positioning-delivery strategies in atherosclerosis for better outcomes.

Extracellular Vesicle (EV) biohybrid systems for cancer therapy: Recent advances and future perspectives

Extracellular vesicles (EVs) are a class of cell-derived lipid-bilayer membrane vesicles secreted by almost all mammalian cells and involved in intercellular communication by shuttling various biological cargoes. Over the last decade, EVs - namely exosomes and microvesicles - have been extensively explored as next-generation nanoscale drug delivery systems (DDSs). This is in large due to their endogenous origin, which enables EVs to circumvent some of the limitations associated with existing cancer therapy approaches (i.e. by preventing recognition by the immune system and improving selectivity towards tumor tissue). However, successful translation of these cell-derived vesicles into clinical applications has been hindered by several factors, among which the loading of exogenous therapeutic molecules still represents a great challenge. In order to address this issue and to further advance these biologically-derived systems as drug carriers, EV-biohybrid nano-DDSs, obtained through the fusion of EVs with conventional synthetic nano-DDSs, have recently been proposed as a valuable alternative as DDSs. Building on the idea of "combining the best of both worlds", a combination of these two unique entities aims to harness the beneficial properties associated with both EVs and conventional nano-DDSs, while overcoming the flaws of the individual components. These biohybrid systems also provide a unique opportunity for exploitation of new synergisms, often leading to improved therapeutic outcomes, thus paving the way for advancements in cancer therapy. This review aims to describe the recent developments of EV-biohybrid nano-DDSs in cancer therapy, to highlight the most promising results and breakthroughs, as well as to provide a glimpse on the possible intrinsic targeting mechanisms of EVs that can be bequeathed to their hybrid systems. Finally, we also provide some insights in the future perspectives of EV-hybrid DDSs.

Drug delivery performance of nanocarriers based on adhesion and interaction for abdominal aortic aneurysm treatment

Targeted drug delivery using nanocarriers (NCs) is one of the novel techniques that has recently been used to improve drug delivery to the Abdominal aortic aneurysm (AAA) disease. The purpose of this study is to evaluate the surface density of NCs (SDNC) adhered via ligand-receptor binding to the inner wall of AAA. For this purpose, fluid-structure interaction (FSI) analysis was first performed for the patient-specific and ideal AAA models. Then, by injecting NCs into the aortic artery, the values of SDNC adhered to and interacted with AAA wall were obtained. Two types of NCs, liposomes, and solid particles in four different diameters, were used to investigate the effect of the diameter and the type of NCs on the drug delivery. Additionally, the effect of the number of the injected NCs to the artery on the values of SDNC adhered to and interacted with AAA wall was investigated. The simulation results showed that the interaction and adhesion values of SDNC for Liposome nanoparticles were higher than the ones for the solid particles. Furthermore, as the diameter of NCs increases, the values of SDNC adhered to AAA wall increase, but the values of SDNC interacted with the inner wall of AAA decrease. In the low number of inserted NCs in the artery (1000 NCs), the interaction and adhesion values of SDNC were very slight, and by increasing the number of NCs inserted into the artery, the drug delivery was improved. By examining different AAA models, it was found that the complexity of the shape of AAA has a minor effect on the pattern of increase or decrease of the values of SDNC adhered to and interacted with AAA wall.This study's findings can improve the understanding of NCs design and propose the appropriate amount of their injection into various AAA models.

Validation of MRI quantitative susceptibility mapping of superparamagnetic iron oxide nanoparticles for hyperthermia applications in live subjects

The use of magnetic fluid hyperthermia (MFH) for cancer therapy has shown promise but lacks suitable methods for quantifying exogenous irons such as superparamagnetic iron oxide (SPIO) nanoparticles as a source of heat generation under an alternating magnetic field (AMF). Application of quantitative susceptibility mapping (QSM) technique to prediction of SPIO in preclinical models has been challenging due to a large variation of susceptibility values, chemical shift from tissue fat, and noisier data arising from the higher resolution required to visualize the anatomy of small animals. In this study, we developed a robust QSM for the SPIO ferumoxytol in live mice to examine its potential application in MFH for cancer therapy. We demonstrated that QSM was able to simultaneously detect high level ferumoxytol accumulation in the liver and low level localization near the periphery of tumors. Detection of ferumoxytol distribution in the body by QSM, however, required imaging prior to and post ferumoxytol injection to discriminate exogenous iron susceptibility from other endogenous sources. Intratumoral injection of ferumoxytol combined with AMF produced a ferumoxytol-dose dependent tumor killing. Histology of tumor sections corroborated QSM visualization of ferumoxytol distribution near the tumor periphery, and confirmed the spatial correlation of cell death with ferumoxytol distribution. Due to the dissipation of SPIOs from the injection site, quantitative mapping of SPIO distribution will aid in estimating a change in temperature in tissues, thereby maximizing MFH effects on tumors and minimizing side-effects by avoiding unwanted tissue heating.

Manufacturing and preclinical validation of CAR T cells targeting ICAM-1 for advanced thyroid cancer therapy

While the majority of thyroid cancer patients are easily treatable, those with anaplastic or poorly differentiated recurrent thyroid carcinomas have a very poor prognosis with a median survival of less than a year. Previously, we have shown a significant correlation between ICAM-1 overexpression and malignancy in thyroid cancer, and have pioneered the use of ICAM-1 targeted CAR T cells as a novel treatment modality. For clinical translation of this novel modality, we designed CAR T cells possessing micromolar rather than nanomolar affinity to ICAM-1 to avoid cytotoxicity in normal cells with basal levels of ICAM-1 expression. Herein, we report the automated process of CAR T cell manufacturing with CliniMACS Prodigy (Miltenyi Biotec) using cryopreserved peripheral blood leukocytes from apheresis collections. Using Prodigy, thawed leukopak cells were enriched for CD4⁺ and CD8⁺ T cells, subjected to double transduction using lentiviral vector, and expanded in culture for a total of 10 days with a final yield of 2–4 × 10⁹ cells. The resulting CAR T cells were formulated for cryopreservation to be used directly for infusion into patients after thawing with no further processing. We examined cross-reactivity of CAR T cells toward both human and murine ICAM-1 and ICAM-1 expression in human and mouse tissues to demonstrate that both efficacy and on-target, off-tumor toxicity can be studied in our preclinical model. Selective anti-tumor activity in the absence of toxicity provides proof-of-concept that micromolar affinity tuned CAR T cells can be used to target tumors expressing high levels of antigen while avoiding normal tissues expressing basal levels of the same antigen. These studies support the initiation of a phase I study to evaluate the safety and potential efficacy of micromolar affinity tuned CAR T cells against newly diagnosed anaplastic and refractory or recurrent thyroid cancers.

Erythrocyte-derived vesicles for circulating tumor cell capture and specific tumor imaging

The precise diagnosis of cancer remains a great challenge; therefore, it is our research interest to develop safe, tumor-specific reagents. In this study, we designed nanovesicles derived from erythrocyte membranes; the nanovesicles are capable of recognizing tumor cells for both circulating tumor cell (CTC) capture and tumor imaging. The tumor-targeting molecules folic acid (FA) and fluorescein Cy5 were modified on the nanovesicle surface. The developed nanovesicles exhibit excellent tumor targeting ability both in vitro and in vivo for CTC capture and in tumor imaging. Compared with traditional immunomagnetic beads, the proposed nanovesicles are capable of avoiding non-specific adsorption as a derivative of red blood cells. Combined with a non-invasive means of micromanipulation, the nanometer-sized vesicles show a high purity of CTC capture (over 90%). In vivo, the nanovesicles can also be employed for efficient tumor imaging without obvious toxicity and side effects. In brief, the nanovesicles prepared herein show potential clinical application for integrated diagnosis in vitro and in vivo.

Leutusome: A Biomimetic Nanoplatform Integrating Plasma Membrane Components of Leukocytes and Tumor Cells for Remarkably Enhanced Solid Tumor Homing

Cell membrane-camouflaged nanoparticles have appeared as a promising platform to develop active tumor targeting nanomedicines. To evade the immune surveillance, we designed a composite cell membrane-camouflaged biomimetic nanoplatform, namely, leutusome, which is made of liposomal nanoparticles incorporating plasma membrane components derived from both leukocytes (murine J774A.1 cells) and tumor cells (head and neck tumor cells HN12). Exogenous phospholipids were used as building blocks to fuse with two cell membranes to form liposomal nanoparticles. Liposomal nanoparticles made of exogenous phospholipids only or in combination with one type of cell membrane were fabricated and compared. The anticancer drug paclitaxel (PTX) was used to make drug-encapsulating liposomal nanoparticles. Leutusome resembling characteristic plasma membrane components of the two cell membranes were examined and confirmed in vitro. A xenograft mouse model of head and neck cancer was used to profile the blood clearance kinetics, biodistribution, and antitumor efficacy of the different liposomal nanoparticles. The results demonstrated that leutusome obtained prolonged blood circulation and was most efficient accumulating at the tumor site (79.1 ± 6.6% ID per gram of tumor). Similarly, leutusome composed of membrane fractions of B16 melanoma cells and leukocytes (J774A.1) showed prominent accumulation within the B16 tumor, suggesting the generalization of the approach. Furthermore, PTX-encapsulating leutusome was found to most potently inhibit tumor growth while not causing systemic adverse effects.

Double-sided effect of tumor microenvironment on platelets targeting nanoparticles

The cancer cells and stromal cells in tumor microenvironment secrete cytokines and recruit "homing" cells (macrophage, lymphocytes, platelets, etc.). Platelets can interact with tumor microenvironment and specifically aggregate at tumor sites. Surprising, we observed different "homing" effects of activated platelets in breast cancer model and pancreatic cancer model which is highly related with the blood supply of tumors. Besides, platelets targeting magnetic nanoparticles (MNPs) can home to breast cancer but be repelled from pancreatic cancer. We observed the targeting effect of MNPs is highly related with the expressions of collagen Ⅰ (marker of extracellular matrix) and CD34 (marker of tumor neovascularization). The homing nanoparticles such as platelets targeting MNPs could realize the tumor targeting ability, photo-thermal effect and tumor immunotherapeutic ability in the accessible tumor (e.g. breast cancer) but not the hypovascular tumor (e.g. pancreatic cancer).

Mapping the Transport Kinetics of Molecules and Particles in Idealized Intracranial Side Aneurysms

Intracranial side aneurysms (IA) are pathological blood-filled bulges in cerebral blood vessels. Unlike healthy blood vessels where mass transport is dominated by convection, both diffusion and convection can play an active role in aneurysm sites. Here, we study via dye washout experiments and numerical simulations, the transport characteristics of particles (1 micron) and small molecules (300 Da) into simplified side aneurysms models following bolus injection. Time-lapse fluorescent microscopy imaging performed in our idealized aneurysm models showed that the parent artery geometry (located on the inner vs. outer curvature) as well as the aneurysm aspect ratio (AR) affect the washout kinetics while the pulsatile nature of the flow, maintained within the physiological range, carries only a minor effect. Importantly, in the absence of effective diffusion, particles that are located on slow streamlines linger within the aneurysm cavity, a phenomenon that could be of importance in deposition of cells and nano/micro-particles within aneurysms. Altogether, mass transport studies may provide valuable insights for better understanding of aneurysm pathophysiology as well as for the design of new diagnostic and theranostic nano-medicines.

Peptide and protein nanoparticle conjugates: versatile platforms for biomedical applications

Peptide- and protein-nanoparticle conjugates have emerged as powerful tools for biomedical applications, enabling the treatment, diagnosis, and prevention of disease. In this review, we focus on the key roles played by peptides and proteins in improving, controlling, and defining the performance of nanotechnologies. Within this framework, we provide a comprehensive overview of the key sequences and structures utilised to provide biological and physical stability to nano-constructs, direct particles to their target and influence their cellular and tissue distribution, induce and control biological responses, and form polypeptide self-assembled nanoparticles. In doing so, we highlight the great advances made by the field, as well as the challenges still faced in achieving the clinical translation of peptide- and protein-functionalised nano-drug delivery vehicles, imaging species, and active therapeutics.

Recent Advances of Membrane-Cloaked Nanoplatforms for Biomedical Applications

In terms of the extremely small size and large specific surface area, nanomaterials often exhibit unusual physical and chemical properties, which have recently attracted considerable attention in bionanotechnology and nanomedicine. Currently, the extensive usage of nanotechnology in medicine holds great potential for precise diagnosis and effective therapeutics of various human diseases in clinical practice. However, a detailed understanding regarding how nanomedicine interacts with the intricate environment in complex living systems remains a pressing and challenging goal. Inspired by the diversified membrane structures and functions of natural prototypes, research activities on biomimetic and bioinspired membranes, especially for those cloaking nanosized platforms, have increased exponentially. By taking advantage of the flexible synthesis and multiple functionality of nanomaterials, a variety of unique nanostructures including inorganic nanocrystals and organic polymers have been widely devised to substantially integrate with intrinsic biomoieties such as lipids, glycans, and even cell and bacteria membrane components, which endow these abiotic nanomaterials with specific biological functionalities for the purpose of detailed investigation of the complicated interactions and activities of nanomedicine in living bodies, including their immune response activation, phagocytosis escape, and subsequent clearance from vascular system. In this review, we summarize the strategies established recently for the development of biomimetic membrane-cloaked nanoplatforms derived from inherent host cells (e.g., erythrocytes, leukocytes, platelets, and exosomes) and invasive pathogens (e.g., bacteria and viruses), mainly attributed to their versatile membrane properties in biological fluids. Meanwhile, the promising biomedical applications based on nanoplatforms inspired by diverse moieties, such as selective drug delivery in targeted sites and effective vaccine development for disease prevention, have also been outlined. Finally, the potential challenges and future prospects of the biomimetic membrane-cloaked nanoplatforms are also discussed.

Targeting Inflammatory Vasculature by Extracellular Vesicles

Extracellular vesicles (EVs) are cell membrane-derived compartments that regulate physiology and pathology in the body. Naturally secreted EVs have been well studied in their biogenesis and have been exploited in targeted drug delivery. Due to the limitations on production of EVs, nitrogen cavitation has been utilized to efficiently generate EV-like drug delivery systems used in treating inflammatory disorders. In this short review, we will discuss the production and purification of EVs, and we will summarize what technologies are needed to improve their production for translation. We describe the drug-loading processes in EVs and their applications as drug delivery systems for inflammatory therapies, focusing on a new type of EVs made from neutrophil membrane using nitrogen cavitation.

Biomimetic nanoparticles for inflammation targeting

There have been many recent exciting developments in biomimetic nanoparticles for biomedical applications. Inflammation, a protective response involving immune cells, blood vessels, and molecular mediators directed against harmful stimuli, is closely associated with many human diseases. As a result, biomimetic nanoparticles mimicking immune cells can help achieve molecular imaging and precise drug delivery to these inflammatory sites. This review is focused on inflammation-targeting biomimetic nanoparticles and will provide an in-depth look at the design of these nanoparticles to maximize their benefits for disease diagnosis and treatment.

Inflammation and Cancer: In Medio Stat Nano

Cancer treatment still remains a challenge due to the several limitations of currently used chemotherapeutics, such as their poor pharmacokinetics, unfavorable chemical properties, as well as inability to discriminate between healthy and diseased tissue. Nanotechnology offered potent tools to overcome these limitations. Drug encapsulation within a delivery system permitted i) to protect the payload from enzymatic degradation/ inactivation in the blood stream, ii) to improve the physicochemical properties of poorly water-soluble drugs, like paclitaxel, and iii) to selectively deliver chemotherapeutics to the cancer lesions, thus reducing the off-target toxicity, and promoting the intracellular internalization. To accomplish this purpose, several strategies have been developed, based on biological and physical changes happening locally and systemically as a consequence of tumorigenesis. Here, we will discuss the role of inflammation in the different steps of tumor development and the strategies based on the use of nanoparticles that exploit the inflammatory pathways in order to selectively target the tumor-associated microenvironment for therapeutic and diagnostic purposes.

Longitudinal PET imaging demonstrates biphasic CAR T cell responses in survivors

Clinical monitoring of adoptive T cell transfer (ACT) utilizes serial blood analyses to discern T cell activity. While useful, these data are 1-dimensional and lack spatiotemporal information related to treatment efficacy or toxicity. We utilized a human genetic reporter, somatostatin receptor 2 (SSTR2), and PET, to quantitatively and longitudinally visualize whole-body T cell distribution and antitumor dynamics using a clinically approved radiotracer. Initial evaluations determined that SSTR2-expressing T cells were detectable at low densities with high sensitivity and specificity. SSTR2-based PET was applied to ACT of chimeric antigen receptor (CAR) T cells targeting intercellular adhesion molecule-1, which is overexpressed in anaplastic thyroid tumors. Timely CAR T cell infusions resulted in survival of tumor-bearing mice, while later infusions led to uniform death. Real-time PET imaging revealed biphasic T cell expansion and contraction at tumor sites among survivors, with peak tumor burden preceding peak T cell burden by several days. In contrast, nonsurvivors displayed unrelenting increases in tumor and T cell burden, indicating that tumor growth was outpacing T cell killing. Thus, longitudinal PET imaging of SSTR2-positive ACT dynamics enables prognostic, spatiotemporal monitoring with unprecedented clarity and detail to facilitate comprehensive therapy evaluation with potential for clinical translation.

Radiolabeled theranostics: magnetic and gold nanoparticles

Introduction: Growing advances in nanotechnology have facilitated the applications of newly emerged nanomaterials in the field of biomedical/pharmaceutical sciences. Following this trend, the multifunctional nanoparticles (NPs) play a significant role in development of advanced drug delivery systems (DDSs) such as diapeutics/theranostics used for simultaneous diagnosis and therapy. Multifunctional radiolabeled NPs with capability of detecting, visualizing and destroying diseased cells with least side effects have been considered as an emerging filed in presentation of the best choice in solving the therapeutic problems. Functionalized magnetic and gold NPs (MNPs and GNPs, respectively) have produced the potential of nanoparticles as sensitive multifunctional probes for molecular imaging, photothermal therapy and drug delivery and targeting.

Methods: In this study, we review the most recent works on the improvement of various techniques for development of radiolabeled magnetic and gold nanoprobes, and discuss the methods for targeted imaging and therapies.

Results: The receptor-specific radiopharmaceuticals have been developed to localized radiotherapy in disease sites. Application of advanced multimodal imaging methods and related modality imaging agents labeled with various radioisotopes (e.g., ¹²⁵I, ¹¹¹In, ⁶⁴Cu, ⁶⁸Ga, ⁹⁹mTc) and MNPs/GNPs have significant effects on treatment and prognosis of cancer therapy. In addition, the surface modification with biocompatible polymer such as polyethylene glycol (PEG) have resulted in development of stealth NPs that can evade the opsonization and immune clearance. These long-circulating agents can be decorated with homing agents as well as radioisotopes for targeted imaging and therapy purposes.

Conclusion: The modified MNPs or GNPs have wide applications in concurrent diagnosis and therapy of various malignancies. Once armed with radioisotopes, these nanosystems (NSs) can be exploited for combined multimodality imaging with photothermal/photodynamic therapy while delivering the loaded drugs or genes to the targeted cells/tissues. These NSs will be a game changer in combating various cancers.

Biomimetic proteolipid vesicles for targeting inflamed tissues

A multitude of micro- and nanoparticles have been developed to improve the delivery of systemically administered pharmaceuticals, which are subject to a number of biological barriers that limit their optimal biodistribution. Bioinspired drug-delivery carriers formulated by bottom-up or top-down strategies have emerged as an alternative approach to evade the mononuclear phagocytic system and facilitate transport across the endothelial vessel wall. Here, we describe a method that leverages the advantages of bottom-up and top-down strategies to incorporate proteins derived from the leukocyte plasma membrane into lipid nanoparticles. The resulting proteolipid vesicles-which we refer to as leukosomes-retained the versatility and physicochemical properties typical of liposomal formulations, preferentially targeted inflamed vasculature, enabled the selective and effective delivery of dexamethasone to inflamed tissues, and reduced phlogosis in a localized model of inflammation.

Biomimetic strategies for targeted nanoparticle delivery

Nanoparticle‐based drug delivery and imaging platforms have become increasingly popular over the past several decades. Among different design parameters that can affect their performance, the incorporation of targeting functionality onto nanoparticle surfaces has been a widely studied subject. Targeted formulations have the ability to improve efficacy and function by positively modulating tissue localization. Many methods exist for creating targeted nanoformulations, including the use of custom biomolecules such as antibodies or aptamers. More recently, a great amount of focus has been placed on biomimetic targeting strategies that leverage targeting interactions found directly in nature. Such strategies, which have been painstakingly selected over time by the process of evolution to maximize functionality, oftentimes enable scientists to forgo the specialized discovery processes associated with many traditional ligands and help to accelerate development of novel nanoparticle formulations. In this review, we categorize and discuss in‐depth recent works in this growing field of bioinspired research.

Immune compatible cystine-functionalized superparamagnetic iron oxide nanoparticles as vascular contrast agents in ultrasonography

Superparamagnetic iron oxide nanoparticles (SPIONs) have been investigated for biomedical applications.

In vivo delivery, pharmacokinetics, biodistribution and toxicity of iron oxide nanoparticles

Iron oxide nanoparticles (IONPs) have been extensively used during the last two decades, either as effective bio-imaging contrast agents or as carriers of biomolecules such as drugs, nucleic acids and peptides for controlled delivery to specific organs and tissues. Most of these novel applications require elaborate tuning of the physiochemical and surface properties of the IONPs. As new IONPs designs are envisioned, synergistic consideration of the body's innate biological barriers against the administered nanoparticles and the short and long-term side effects of the IONPs become even more essential. There are several important criteria (e.g. size and size-distribution, charge, coating molecules, and plasma protein adsorption) that can be effectively tuned to control the in vivo pharmacokinetics and biodistribution of the IONPs. This paper reviews these crucial parameters, in light of biological barriers in the body, and the latest IONPs design strategies used to overcome them. A careful review of the long-term biodistribution and side effects of the IONPs in relation to nanoparticle design is also given. While the discussions presented in this review are specific to IONPs, some of the information can be readily applied to other nanoparticle systems, such as gold, silver, silica, calcium phosphates and various polymers.

Side-by-Side Comparison of Commonly Used Biomolecules That Differ in Size and Affinity on Tumor Uptake and Internalization

The ability to use a systemically injected agent to image tumor is influenced by tumor characteristics such as permeability and vascularity, and the size, shape, and affinity of the imaging agent. In this study, six different imaging biomolecules, with or without specificity to tumor, were examined for tumor uptake and internalization at the whole body, ex-vivo tissue, and cellular levels: antibodies, antibody fragments (Fab), serum albumin, and streptavidin. The time of peak tumor uptake was dependent solely on the size of molecules, suggesting that molecular size is the major factor that influences tumor uptake by its effect on systemic clearance and diffusion into tumor. Affinity to tumor antigen failed to augment tumor uptake of Fab above non-specific accumulation, which suggests that Fab fragments of typical monoclonal antibodies may fall below an affinity threshold for use as molecular imaging agents. Despite abundant localization into the tumor, albumin and streptavidin were not found on cell surface or inside cells. By comparing biomolecules differing in size and affinity, our study highlights that while pharmacokinetics are a dominant factor in tumor uptake for biomolecules, affinity to tumor antigen is required for tumor binding and internalization.

De novo chemoattractants form supramolecular hydrogels for immunomodulating neutrophils in vivo

Most immunomodulatory materials (e.g., vaccine adjuvants such as alum) modulate adaptive immunity, and yet little effort has focused on developing materials to regulate innate immunity, which get mentioned only when inflammation affects the biocompatibility of biomaterials. Traditionally considered as short-lived effector cells from innate immunity primarily for the clearance of invading microorganisms without specificity, neutrophils exhibit a key role in launching and shaping the immune response. Here we show that the incorporation of unnatural amino acids into a well-known chemoattractant-N-formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLF)-offers a facile approach to create a de novo, multifunctional chemoattractant that self-assembles to form supramolecular nanofibrils and hydrogels. This de novo chemoattractant not only exhibits preserved cross-species chemoattractant activity to human and murine neutrophils, but also effectively resists proteolysis. Thus, its hydrogel, in vivo, releases the chemoattractant and attracts neutrophils to the desired location in a sustainable manner. As a novel and general approach to generate a new class of biomaterials for modulating innate immunity, this work offers a prolonged acute inflammation model for developing various new applications.

Leukocyte mimetic polysaccharide microparticles tracked in vivo on activated endothelium and in abdominal aortic aneurysm

We have developed injectable microparticles functionalized with fucoidan, in which sulfated groups mimic the anchor sites of P-selectin glycoprotein ligand-1 (PSGL-1), one of the principal receptors supporting leukocyte adhesion. These targeted microparticles were combined with a fluorescent dye and a T2(∗) magnetic resonance imaging (MRI) contrast agent, and then tracked in vivo with small animal imaging methods. Microparticles of 2.5μm were obtained by a water-in-oil emulsification combined with a cross-linking process of polysaccharide dextran, fluorescein isothiocyanate dextran, pullulan and fucoidan mixed with ultrasmall superparamagnetic particles of iron oxide. Fluorescent intravital microscopy observation revealed dynamic adsorption and a leukocyte-like behaviour of fucoidan-functionalized microparticles on a calcium ionophore induced an activated endothelial layer of a mouse mesentery vessel. We observed 20times more adherent microparticles on the activated endothelium area after the injection of functionalized microparticles compared to non-functionalized microparticles (197±11 vs. 10±2). This imaging tool was then applied to rats presenting an elastase perfusion model of abdominal aortic aneurysm (AAA) and 7.4T in vivo MRI was performed. Visual analysis of T2(∗)-weighted MR images showed a significant contrast enhancement on the inner wall of the aneurysm from 30min to 2h after the injection. Histological analysis of AAA cryosections revealed microparticles localized inside the aneurysm wall, in the same areas in which immunostaining shows P-selectin expression. The developed leukocyte mimetic imaging tool could therefore be relevant for molecular imaging of vascular diseases and for monitoring biologically active areas prone to rupture in AAA.

Synthetic routes to magnetic nanoparticles for MPI

Magnetic particle imaging (MPI) is a new imaging technique for visualizing the three-dimensional distribution of superparamagnetic iron oxide nanoparticles with specific properties (MPI tracers). Initial results obtained with MPI using superparamagnetic iron oxide as blood pool markers suggest that the method has great potential for cardiovascular imaging. Conversely, no clinically approved MPI tracers currently exist that could be used to exploit this potential of MPI. This article describes thermal decomposition and coprecipitation, two relevant methods for synthesizing and optimizing superparamagnetic iron oxide nanoparticles for MPI. Furthermore it summarizes the recent literature on MPI tracers and explores what can be learned from structural studies with Resovist(®) for novel synthesis approaches.

Caught in the act: revealing the metastatic process by live imaging

The prognosis of metastatic cancer in patients is poor. Interfering with metastatic spread is therefore important for achieving better survival from cancer. Metastatic disease is established through a series of steps, including breaching of the basement membrane, intravasation and survival in lymphatic or blood vessels, extravasation, and growth at distant sites. Yet, although we know the steps involved in metastasis, the cellular and molecular mechanisms of dissemination and colonization of distant organs are incompletely understood. Here, we review the important insights into the metastatic process that have been gained specifically through the use of imaging technologies in murine, chicken embryo and zebrafish model systems, including high-resolution two-photon microscopy and bioluminescence. We further discuss how imaging technologies are beginning to allow researchers to address the role of regional activation of specific molecular pathways in the metastatic process. These technologies are shedding light, literally, on almost every step of the metastatic process, particularly with regards to the dynamics and plasticity of the disseminating cancer cells and the active participation of the microenvironment in the processes.

Vascular deposition patterns for nanoparticles in an inflamed patient-specific arterial tree

Inflammation, a precursor to many diseases including cancer and atherosclerosis, induces differential surface expression of specific vascular molecules. Blood-borne nanoparticles (NPs), loaded with therapeutic and imaging agents, can recognize and use these molecules as vascular docking sites. Here, a computational model is developed within the isogeometric analysis framework to understand and predict the vascular deposition of NPs within an inflamed arterial tree. The NPs have a diameter ranging from 0.1 to 2.0 μm and are decorated with antibodies directed toward three endothelial adhesion molecules, namely intravascular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin, whose surface density depends on the local wall shear stress. Results indicate VCAM-1 targeted NPs adhere more, with ICAM-1 directed NPs adhering least efficiently, resulting in approximately an order-of-magnitude lower average particle surface density. ICAM-1 and E-selectin directed 0.5 μm NPs are distributed more uniformly (heterogeneity index ≈ 0.9 and 1.0, respectively) over the bifurcating vascular branches compared to their VCAM-1 counterparts (heterogeneity index ≈ 1.4). When the NPs are coated with antibodies for VCAM-1 and E-selectin in equal proportions, a more uniform vascular distribution is achieved compared with VCAM-1-only targeted particles, thus demonstrating the advantage of NP multivalency in vascular targeting. Furthermore, the larger NPs (2 μm) adhere more (≈ 200%) in the lower branches compared to the upper branch. This computational framework provides insights into how size, ligand type, density, and multivalency can be manipulated to enhance NP vascular adhesion in an individual patient.

Liposomes and nanotechnology in drug development: focus on neurological targets

Neurological diseases represent a medical, social, and economic problem of paramount importance in developed countries. Although their etiology is generally known, developing therapeutic interventions for the central nervous system is challenging due to the impermeability of the blood-brain barrier. Thus, the fight against neurological diseases usually struggles "at the gates" of the brain. Flooding the bloodstream with drugs, where only a minor fraction reaches its target therapeutic site, is an inefficient, expensive, and dangerous procedure, because of the risk of side effects at nontargeted sites. Currently, advances in the field of nanotechnology have enabled development of a generation of multifunctional molecular platforms that are capable of transporting drugs across the blood-brain barrier, targeting specific cell types or functional states within the brain, releasing drugs in a controlled manner, and enabling visualization of processes in vivo using conventional imaging systems. The marriage between drug delivery and molecular imaging disciplines has resulted in a relatively new discipline, known as theranostics, which represents the basis of the concept of personalized medicine. In this study, we review the concepts of the blood-brain barrier and the strategies used to traverse/bypass it, the role of nanotechnology in theranostics, the wide range of nanoparticles (with emphasis on liposomes) that can be used as stealth drug carriers, imaging probes and targeting devices for the treatment of neurological diseases, and the targets and targeting strategies envisaged in the treatment of different types of brain pathology.

On the roles of polyvalent binding in immune recognition: perspectives in the nanoscience of immunology and the immune response to nanomedicines

Immunology often conveys the image of large molecules, either in the soluble state or in the membrane of leukocytes, forming multiple contacts with a target for actions of the immune system. Avidity names the ability of a polyvalent molecule to form multiple connections of the same kind with ligands tethered to the same surface. Polyvalent interactions are vastly stronger than their monovalent equivalent. In the present review, the functional consequences of polyvalent interactions are explored in a perspective of recent theoretical advances in understanding the thermodynamics of such binding. From insights on the structural biology of soluble pattern recognition molecules as well as adhesion molecules in the cell membranes or in their proteolytically shed form, this review documents the prominent role of polyvalent interactions in making the immune system a formidable barrier to microbial infection as well as constituting a significant challenge to the application of nanomedicines.

Tumor suppression via paclitaxel-loaded drug carriers that target inflammation marker upregulated in tumor vasculature and macrophages

Clinically approved chemotherapeutic nanoparticles may provide advantages over free drugs by achieving slower clearance and preferential accumulation in tumors. However, the lack of leaky vasculatures can create barriers to the permeation of ~100 nm-sized nanoparticles in solid tumors. We hypothesized that nanoparticles designed to target both tumor and tumor stroma would penetrate deeper into the tumors. To construct such comprehensive drug carriers, we utilized cross-linked amphiphilic polymer nanoparticles and functionalized them to target ICAM-1, a biomarker prevalent in various tumors and inflamed tumor stroma. The targeting moiety was derived from the modular domain present in α(L) integrin, which was engineered for high affinity and cross-reactivity with human and murine ICAM-1. ICAM-1-selective delivery of paclitaxel produced potent tumor suppression of not only ICAM-1-positive cervical cancer cells but also ICAM-1-negative tumors, presumably by causing cytotoxicity in tumor-associated endothelium (CD31(+)) and macrophages (CD68(+)) over-expressing ICAM-1. Contrary to the strategies of targeting only the tumor or specific tumor stromal constituents, we present a strategy in delivering therapeutics to the major cellular components of solid tumors. Drug carriers against inflammation-biomarkers may be effective against many different types of tumors, while being less susceptible to the highly mutable nature of tumor markers.

Complex structure of engineered modular domains defining molecular interaction between ICAM-1 and integrin LFA-1

Intermolecular contacts between integrin LFA-1 (α(L)β(2)) and ICAM-1 derive solely from the integrin α(L) I domain and the first domain (D1) of ICAM-1. This study presents a crystal structure of the engineered complex of the α(L) I domain and ICAM-1 D1. Previously, we engineered the I domain for high affinity by point mutations that were identified by a directed evolution approach. In order to examine α(L) I domain allostery between the C-terminal α7-helix (allosteric site) and the metal-ion dependent adhesion site (active site), we have chosen a high affinity variant without mutations directly influencing either the position of the α7-helix or the active sites. In our crystal, the α(L) I domain was found to have a high affinity conformation to D1 with its α7-helix displaced downward away from the binding interface, recapitulating a current understanding of the allostery in the I domain and its linkage to neighboring domains of integrins in signaling. To enable soluble D1 of ICAM-1 to fold on its own, we also engineered D1 to be functional by mutations, which were found to be those that would convert hydrogen bond networks in the solvent-excluded core into vdW contacts. The backbone structure of the β-sandwich fold and the epitope for I domain binding of the engineered D1 were essentially identical to those of wild-type D1. Most deviations in engineered D1 were found in the loops at the N-terminal region that interacts with human rhinovirus (HRV). Structural deviation found in engineered D1 was overall in agreement with the function of engineered D1 observed previously, i.e., full capacity binding to α(L) I domain but reduced interaction with HRV.