Cell source determines the immunological impact of biomimetic nanoparticles

Biomimetic nanoparticles for effective Celastrol delivery to targeted treatment of rheumatoid arthritis through the ROS-NF-κB inflammasome axis

Previous study has indicated that Celastrol (Cel) has various physiological and pharmacological effects, including antibacterial, antioxidant, pro-apoptotic, anticancer and anti-rheumatoid arthritis (RA) effects. However, low water solubility, low oral bioavailability, narrow treatment window, and high incidence of systemic adverse reactions still limit the further clinical application of Cel. Here, aiming at effectively overcome those shortcomings of Cel to boost its beneficial effects for treating RA, we developed the leukosome (LEUKO) coated biomimetic nanoparticles (NPs) for the targeted delivery of Cel to arthritis injury area in RA. LEUKO were synthesized using membrane proteins purified from activated J774 macrophage. LEUKO and Cel-loaded LEUKO (Cel@LEUKO) were characterized using dynamic light scattering and transmission electron microscopy. Our results demonstrated that Cel@LEUKO can inhibit the inflammatory response of lipopolysaccharide (LPS) induced mouse monocyte macrophage leukemia cells (RAW264.7 cells) and human rheumatoid arthritis synovial fibroblasts (MH7A) cells through the inhibition of reactive oxygen species (ROS)-NF-κB pathway. In addition, research has shown that LEUKO effectively targets and transports Cel to the inflammatory site of RA, increased drug concentration in affected areas, reduced systemic toxicity of Cel, and reduced clinical symptoms, inflammatory infiltration, bone erosion, and serum inflammatory factors in collagen-induced arthritis (CIA) rats.

Delivery of nucleic acids using nanomaterials

The increasing number of approved nucleic acid therapeutics demonstrates the potential for the prevention and treatment of a broad spectrum of diseases. This trend underscores the significant impact and promise of nucleic acid-based treatments in the field of medicine. Nevertheless, employing nucleic acids as therapeutics is challenging due to their susceptibility to degradation by nucleases and their unfavorable physicochemical characteristics that hinder delivery into cells. Appropriate vectors play a pivotal role in improving nucleic acid stability and delivering nucleic acids into specific cells. The maturation of delivery systems has led to breakthroughs in the development of therapeutics based on nucleic acids such as DNA, siRNA, and mRNA. Non-viral vectors have gained prominence among the myriad of nanomaterials due to low immunogenicity, ease of manufacturing, and simplicity of cost-effective, large-scale production. Here, we provide an overview of the recent advancements in nanomaterials for nucleic acid delivery. Specifically, we give a detailed introduction to the characteristics of polymers, lipids, and polymer-lipid hybrids, and provide comprehensive descriptions of their applications in nucleic acid delivery. Also, biological barriers, administration routes, and strategies for organ-selective delivery of nucleic acids are discussed. In summary, this review offers insights into the rational design of next-generation delivery vectors for nucleic acid delivery.

Technological aspects of manufacturing and analytical control of biological nanoparticles

Extracellular vesicles (EVs) are cell-derived biological nanoparticles that gained great interest for drug delivery. EVs have numerous advantages compared to synthetic nanoparticles, such as ideal biocompatibility, safety, ability to cross biological barriers and surface modification via genetic or chemical methods. On the other hand, the translation and the study of these carriers resulted difficult, mostly because of significant issues in up-scaling, synthesis and impractical methods of quality control. However, current manufacturing advances enable EV packaging with any therapeutic cargo, including DNA, RNA (for RNA vaccines and RNA therapeutics), proteins, peptides, RNA-protein complexes (including gene-editing complexes) and small molecules drugs. To date, an array of new and upgraded technologies have been introduced, substantially improving EV production, isolation, characterization and standardization. The used-to-be "gold standards" of EV manufacturing are now outdated, and the state-of-art requires extensive revision. This review re-evaluates the pipeline for EV industrial production and provides a critical overview of the modern technologies required for their synthesis and characterization.

Nanoparticle-Based Interventions for Liver Transplantation

Liver transplantation is the only treatment for hepatic insufficiency as a result of acute and chronic liver injuries/pathologies that fail to recover. Unfortunately, there remains an enormous and growing gap between organ supply and demand. Although recipients on the liver transplantation waitlist have significantly higher mortality, livers are often not allocated because they are (i) classified as extended criteria or marginal livers and (ii) subjected to longer cold preservation time (>6 h) with a direct correlation of poor outcomes with longer cold ischemia. Downregulating the recipient's innate immune response to successfully tolerate a graft having longer cold ischemia times or ischemia-reperfusion injury through induction of immune tolerance in the graft and the host would significantly improve organ utilization and post-transplant outcomes. Broadly, technologies proposed for development aim to extend the life of the transplanted liver through post-transplant or recipient conditioning. In this review, we focus on the potential benefits of nanotechnology to provide unique pre-transplant grafting and recipient conditioning of extended criteria donor livers using immune tolerance induction and hyperthermic pre-conditioning.

Implications of biomimetic nanocarriers in targeted drug delivery

Nanomaterials and nanostructures have shown fascinating performances in various biomedicine fields, from cosmetic to cancer diagnosis and therapy. Engineered nanomaterials can encapsulate both lipophilic and hydrophilic substances/drugs to eliminate their limitations in the free forms, such as low bioavailability, multiple drug administration, off-target effects, and various side effects. Moreover, it is possible to deliver the loaded cargo to the desired site of action using engineered nanomaterials. One approach that has made nanocarriers more sophisticated is the "biomimetic" concept. In this scenario, biomolecules (e.g., natural proteins, peptides, phospholipids, cell membranes) are used as building blocks to construct nanocarriers and/or modify agents. For instance, it has been reported that specific cells tend to migrate to a particular site during specific circumstances (e.g., inflammation, tumor formation). Employing the cell membrane of these cells as a coating for nanocarriers confers practical targeting approaches. Accordingly, we introduce the biomimetic concept in the current study, review the recent studies, challenge the issues, and provide practical solutions.

Melatonin loaded hybrid nanomedicine: DoE approach, optimization and in vitro study on diabetic retinopathy model

Melatonin (MEL) is a pleiotropic neurohormone of increasing interest as a neuroprotective agent in ocular diseases. Improving the mucoadhesiveness is a proposed strategy to increase the bioavailability of topical formulations. Herein, the design and optimization of MEL-loaded lipid-polymer hybrid nanoparticles (mel-LPHNs) using Design of Experiment (DoE) was performed. LPHNs consisted of PLGA-PEG polymer nanoparticles coated with a cationic lipid-shell. The optimized nanomedicine showed suitable size for ophthalmic administration (189.4 nm; PDI 0.260) with a positive surface charge (+39.8 mV), high encapsulation efficiency (79.8 %), suitable pH and osmolarity values, good mucoadhesive properties and a controlled release profile. Differential Scanning Calorimetry and Fourier-Transform Infrared Spectroscopy confirmed the encapsulation of melatonin in the systems and the interaction between lipids and polymer matrix. Biological evaluation in an in vitro model of diabetic retinopathy demonstrated enhanced neuroprotective and antioxidant activities of mel-LPHNs, compared to melatonin aqueous solution at the same concentration (0.1 and 1 μM). A modified Draize test was performed to assess the ocular tolerability of the formulation showing no signs of irritation. To the best our knowledge, this study reported for the first time the development of mel-LPHNs, a novel and safe hybrid platform suitable for the topical management of retinal diseases.

Research update on cell membrane camouflaged nanoparticles for cancer therapy

Cell membrane-camouflaged biomimetic functionalization of nanoparticles has emerged as a promising strategy for cancer theranostics. These cell membranes used for camouflaging are generally isolated from natural or engineered erythrocytes, neutrophils, macrophages, T lymphatic cells, stem cells, and cancer cells. The camouflaging strategy of coating nanoparticles with cell membranes allows for tumor homotypic targeting through self-recognition as source cells, immune evasion, and a prolonged blood circulation time, thereby improving the effective payload delivery and tumor therapy. More so, some engineered cell membranes with functionalized peptides, proteins and moieties on membrane surface can be transferred for therapy in the same time. In this review, we summarize the latest research on various types of cell membrane-camouflaged nanoparticles aimed at anti-cancer therapy, focusing on the biological advantages of different cell membranes, constitutions of nanoparticles, fabrication processes, key findings, potential therapies, and discuss the major challenges and future opportunities.

Biomimetic Nanomaterials: Diversity, Technology, and Biomedical Applications

Biomimetic nanomaterials (BNMs) are functional materials containing nanoscale components and having structural and technological similarities to natural (biogenic) prototypes. Despite the fact that biomimetic approaches in materials technology have been used since the second half of the 20th century, BNMs are still at the forefront of materials science. This review considered a general classification of such nanomaterials according to the characteristic features of natural analogues that are reproduced in the preparation of BNMs, including biomimetic structure, biomimetic synthesis, and the inclusion of biogenic components. BNMs containing magnetic, metal, or metal oxide organic and ceramic structural elements (including their various combinations) were considered separately. The BNMs under consideration were analyzed according to the declared areas of application, which included tooth and bone reconstruction, magnetic and infrared hyperthermia, chemo- and immunotherapy, the development of new drugs for targeted therapy, antibacterial and anti-inflammatory therapy, and bioimaging. In conclusion, the authors’ point of view is given about the prospects for the development of this scientific area associated with the use of native, genetically modified, or completely artificial phospholipid membranes, which allow combining the physicochemical and biological properties of biogenic prototypes with high biocompatibility, economic availability, and scalability of fully synthetic nanomaterials.

Biomimetic Nanotherapeutics: Employing Nanoghosts to fight Melanoma

Melanoma is a cancer of melanocytes present at the basal layer of the skin. Nanomedicine has armed us with competent platform to manage such fatal neoplastic diseases. Nevertheless, it suffers from numerous pitfalls such as rapid clearance and opsonization of surface-functionalized carriers, biocompatibility and idiopathic reactions which could be difficult to predict in the patient. Biomimetic approach, a novel step towards personalized medicine bridges these drawbacks by employing endogenous cell membranes to traverse physiological barriers. Camouflaged carriers coated with natural cell membranes possess unique characteristics such as high circulatory periods, and the absence of allogenic and xenogenic responses. Proteins residing on the cell membranes render a diverse range of utilities to the coated nanoparticles including natural efficiency to identify cellular targets, homologous targeting, reticuloendothelial system evasion, biocompatibility and reduced adverse and idiopathic effects. In the present article, we have focused on cell membrane camouflaged nanocarriers for melanoma management. We have discussed various types of biomimetic systems, their processing and coating approaches, and their characterization. We have also enumerated novel avenues in melanoma treatment and the combination of biomimetic systems with smart nanoparticulate systems with the potential to bring breakthroughs in the near future. Additionally, immunotherapy-based biomimetic systems to combat melanoma have been highlighted. Hurdles towards clinical translation and ways to overcome them have been explained in detail.

Application of lipid nanovesicle drug delivery system in cancer immunotherapy

Immunotherapy has gradually emerged as the most promising anticancer therapy. In addition to conventional anti-PD-1/PD-L1 therapy, anti-CTLA-4 therapy, CAR-T therapy, etc., immunotherapy can also be induced by stimulating the maturation of immune cells or inhibiting negative immune cells, regulating the tumor immune microenvironment and cancer vaccines. Lipid nanovesicle drug delivery system includes liposomes, cell membrane vesicles, bacterial outer membrane vesicles, extracellular vesicles and hybrid vesicles. Lipid nanovesicles can be used as functional vesicles for cancer immunotherapy, and can also be used as drug carriers to deliver immunotherapy drugs to the tumor site for cancer immunotherapy. Here, we review recent advances in five kinds of lipid nanovesicles in cancer immunotherapy and assess the clinical application prospects of various lipid nanovesicles, hoping to provide valuable information for clinical translation in the future.

Nanocarriers surface engineered with cell membranes for cancer targeted chemotherapy

Background

Inspired by nature, the biomimetic approach has been incorporated into drug nanocarriers for cancer targeted chemotherapy. The nanocarriers are cloaked in cell membranes, which enables them to incorporate the functions of natural cells.

Key scientific concepts of review

Nanocarriers surface engineered with cell membranes have emerged as a fascinating source of materials for cancer targeted chemotherapy. A distinctive characteristic of cell membrane-coated nanocarriers (CMCNs) is that they include carbohydrates, proteins, and lipids, in addition to being biocompatible. CMCNs are capable of interacting with the complicated biological milieu of the tumor because they contain the signaling networks and intrinsic functions of their parent cells. Numerous cell membranes have been investigated for the purpose of masking nanocarriers with membranes, and various tumor-targeting methods have been devised to improve cancer targeted chemotherapy. Moreover, the diverse structure of the membrane from different cell sources broadens the spectrum of CMCNs and offers an entirely new class of drug-delivery systems.

Aim of review

This review will describe the manufacturing processes for CMCNs and the therapeutic uses for different kinds of cell membrane-coated nanocarrier-based drug delivery systems, as well as addressing obstacles and future prospects.

Graphical Abstract

Biomimetic immunomodulation strategies for effective tissue repair and restoration

Inflammation plays a central role in wound healing following injury or disease and is mediated by a precise cascade of cellular and molecular events. Unresolved inflammatory processes lead to chronic inflammation and fibrosis, which can result in prolonged wound healing lasting months or years that hampers tissue function. Therapeutic interventions mediated by immunomodulatory drugs, cells, or biomaterials, are therefore most effective during the inflammatory phase of wound healing when a pro-regenerative environment is essential. In this review, we discuss the advantages of exploiting knowledge of the native tissue microenvironment to develop therapeutics capable of modulating the immune response and promoting functional tissue repair. In particular, we provide examples of the most recent biomimetic platforms proposed to accomplish this goal, with an emphasis on those able to induce macrophage polarization towards a pro-regenerative phenotype.

Biomimetic and immunomodulatory therapeutics as an alternative to natural exosomes for vascular and cardiac applications

Inflammation is a central mechanism in cardiovascular diseases (CVD), where sustained oxidative stress and immune responses contribute to cardiac remodeling and impairment. Exosomes are extracellular vesicles released by cells to communicate with their surroundings and to modulate the tissue microenvironment. Recent evidence indicates their potential as cell-free immunomodulatory therapeutics for CVD, preventing cell death and fibrosis while inducing wound healing and angiogenesis. Biomimetic exosomes are semi-synthetic particles engineered using essential moieties present in natural exosomes (lipids, RNA, proteins) to reproduce their therapeutic effects while improving on scalability and standardization due to the ample range of moieties available to produce them. In this review, we provide an up-to-date description of the use of exosomes for CVD and offer our vision on the areas of opportunity for the development of biomimetic strategies. We also discuss the current limitations to overcome in the process towards their translation into clinic.

Chemically Engineered Immune Cell-Derived Microrobots and Biomimetic Nanoparticles: Emerging Biodiagnostic and Therapeutic Tools

Over the past decades, considerable attention has been dedicated to the exploitation of diverse immune cells as therapeutic and/or diagnostic cell-based microrobots for hard-to-treat disorders. To date, a plethora of therapeutics based on alive immune cells, surface-engineered immune cells, immunocytes' cell membranes, leukocyte-derived extracellular vesicles or exosomes, and artificial immune cells have been investigated and a few have been introduced into the market. These systems take advantage of the unique characteristics and functions of immune cells, including their presence in circulating blood and various tissues, complex crosstalk properties, high affinity to different self and foreign markers, unique potential of their on-demand navigation and activity, production of a variety of chemokines/cytokines, as well as being cytotoxic in particular conditions. Here, the latest progress in the development of engineered therapeutics and diagnostics inspired by immune cells to ameliorate cancer, inflammatory conditions, autoimmune diseases, neurodegenerative disorders, cardiovascular complications, and infectious diseases is reviewed, and finally, the perspective for their clinical application is delineated.

Bioinspired Extracellular Vesicles: Lessons Learned From Nature for Biomedicine and Bioengineering

Efficient communication is essential in all layers of the biological chain. Cells exchange information using a variety of signaling moieties, such as small molecules, proteins, and nucleic acids. Cells carefully package these messages into lipid complexes, collectively named extracellular vesicles (EVs). In this work, we discuss the nature of these cell carriers, categorize them by their origin, explore their role in the homeostasis of healthy tissues, and examine how they regulate the pathophysiology of several diseases. This review will also address the limitations of using EVs for clinical applications and discuss novel methods to engineer nanoparticles to mimic the structure, function, and features of EVs. Using lessons learned from nature and understanding how cells use EVs to communicate across distant sites, we can develop a better understanding of how to tailor the fundamental features of drug delivery carriers to encapsulate various cargos and target specific sites for biomedicine and bioengineering.

Multi-component clobetasol-loaded monolithic lipid-polymer hybrid nanoparticles ameliorate imiquimod-induced psoriasis-like skin inflammation in Swiss albino mice

Lipid-polymer hybrid nanoparticles (LPNs) exhibit several advantages over polymeric and non-polymeric systems in terms of improved drug loading, controlled release, stability, and cellular uptake. Herein we report a scalable and stable monolithic lipid-polymer hybrid nanoparticles (LPNs) consisting of a combination of lipids (solid and liquid) and an amphiphilic copolymer, mPEG-PLA. Clobetasol propionate, a topical corticosteroid, was encapsulated in the hydrophobic core of these LPNs that showed spherical shaped particles with a z-average size of 94.8 nm (PDI = 0.213) and encapsulation efficiency of 84.3%. These clobetasol loaded LPNs (CP/LPNs) were formulated into a topical hydrogel using carbopol 974P. CP/LPNs gel showed a sustained in vitro clobetasol release for 7 days with no burst release and 6 month stability at 2-8°C and room temperature. Further, CP/LPNs showed an improved cellular uptake with significant growth inhibition of HaCaT cells. In ex vivo studies, these LPNs penetrated into the viable epidermis and dermis region of the psoriatic skin with undetectable quantities leaching to the reservoir. Further, the topical application of CP/LPNs gel on Swiss albino mice with psoriasis-like inflammation showed negligible leaching of clobetasol into the systemic circulation. Efficacy assessment showed significantly improved PASI score, reduced skin damage and proliferation after treatment with CP/LPNs gel as compared to marketed product (Clobetamos™). Collectively, the enhanced cellular uptake, high skin penetration with increased skin retention, and improved efficacy demonstrate the potential of these LPNs for future clinical application.

Biomimetic Nanocarriers for Cancer Target Therapy

Nanotechnology offers innovative tools for the design of biomimetic nanocarriers for targeted cancer therapy. These nano-systems present several advantages such as cargo's protection and modulation of its release, inclusion of stimuli-responsive elements, and enhanced tumoral accumulation. All together, these nano-systems suffer low therapeutic efficacy in vivo because organisms can recognize and remove foreign nanomaterials. To overcome this important issue, different modifications on nanoparticle surfaces were exploited in order to reach the desired therapeutic efficacy eliciting, also, the response of immune system against cancer cells. For this reason, more recently, a new strategy involving cell membrane-covered nanoparticles for biomedical application has been attracting increasing attention. Membranes from red blood cells, platelets, leukocytes, tumor, and stem cells, have been exploited as biomimetic coatings of nanoparticles for evading clearance or stimulated immune system by maintaining in the same way their targeting capability. In this review, the use of different cell sources as coating of biomimetic nanocarriers for cancer therapy is discussed.

Endosomal Escape of Polymer-Coated Silica Nanoparticles in Endothelial Cells

Current investigations into hazardous nanoparticles (i.e., nanotoxicology) aim to understand the working mechanisms that drive toxicity. This understanding has been used to predict the biological impact of the nanocarriers as a function of their synthesis, material composition, and physicochemical characteristics. It is particularly critical to characterize the events that immediately follow cell stress resulting from nanoparticle internalization. While reactive oxygen species and activation of autophagy are universally recognized as mechanisms of nanotoxicity, the progression of these phenomena during cell recovery has yet to be comprehensively evaluated. Herein, primary human endothelial cells are exposed to controlled concentrations of polymer-functionalized silica nanoparticles to induce lysosomal damage and achieve cytosolic delivery. In this model, the recovery of cell functions lost following endosomal escape is primarily represented by changes in cell distribution and the subsequent partitioning of particles into dividing cells. Furthermore, multilamellar bodies are found to accumulate around the particles, demonstrating progressive endosomal escape. This work provides a set of biological parameters that can be used to assess cell stress related to nanoparticle exposure and the subsequent recovery of cell processes as a function of endosomal escape.

Cell Membrane-Based Biomimetic Nanoparticles and the Immune System: Immunomodulatory Interactions to Therapeutic Applications

Nanoparticle-based drug delivery systems have been synthesized from a wide array of materials. The therapeutic success of these platforms hinges upon their ability to favorably interact with the biological environment (both systemically and locally) and recognize the diseased target tissue. The immune system, composed of a highly coordinated organization of cells trained to recognize foreign bodies, represents a key mediator of these interactions. Although components of this system may act as a barrier to nanoparticle (NP) delivery, the immune system can also be exploited to target and trigger signaling cues that facilitate the therapeutic response stemming from systemic administration of NPs. The nano-bio interface represents the key facilitator of this communication exchange, where the surface properties of NPs govern their in vivo fate. Cell membrane-based biomimetic nanoparticles have emerged as one approach to achieve targeted drug delivery by actively engaging and communicating with the biological milieu. In this review, we will highlight the relationship between these biomimetic nanoparticles and the immune system, emphasizing the role of tuning the nano-bio interface in the immunomodulation of diseases. We will also discuss the therapeutic applications of this approach with biomimetic nanoparticles, focusing on specific diseases ranging from cancer to infectious diseases. Lastly, we will provide a critical evaluation on the current state of this field of cell membrane-based biomimetic nanoparticles and its future directions in immune-based therapy.

Liposome-Embedding Silicon Microparticle for Oxaliplatin Delivery in Tumor Chemotherapy

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

Biomimetic cellular vectors for enhancing drug delivery to the lungs

Despite recent advances in drug delivery, the targeted treatment of unhealthy cells or tissues continues to remain a priority. In cancer (much like other pathologies), delivery vectors are designed to exploit physical and biological features of unhealthy tissues that are not always homogenous across the disease. In some cases, shifting the target from unhealthy tissues to the whole organ can represent an advantage. Specifically, the natural organ-specific retention of nanotherapeutics following intravenous administration as seen in the lung, liver, and spleen can be strategically exploited to enhance drug delivery. Herein, we outline the development of a cell-based delivery system using macrophages as a delivery vehicle. When loaded with a chemotherapeutic payload (i.e., doxorubicin), these cellular vectors (CELVEC) were shown to provide continued release within the lung. This study provides proof-of-concept evidence of an alternative class of biomimetic delivery vectors that capitalize on cell size to provide therapeutic advantages for pulmonary treatments.

Cell-mediated and cell membrane-coated nanoparticles for drug delivery and cancer therapy

Nanotechnology-based drug delivery platforms have been developed over the last two decades because of their favorable features in terms of improved drug bioavailability and stability. Despite recent advancement in nanotechnology platforms, this approach still falls short to meet the complexity of biological systems and diseases, such as avoiding systemic side effects, manipulating biological interactions and overcoming drug resistance, which hinders the therapeutic outcomes of the NP-based drug delivery systems. To address these issues, various strategies have been developed including the use of engineered cells and/or cell membrane-coated nanocarriers. Cell membrane receptor profiles and characteristics are vital in performing therapeutic functions, targeting, and homing of either engineered cells or cell membrane-coated nanocarriers to the sites of interest. In this context, we comprehensively discuss various cell- and cell membrane-based drug delivery approaches towards cancer therapy, the therapeutic potential of these strategies, and the limitations associated with engineered cells as drug carriers and cell membrane-associated drug nanocarriers. Finally, we review various cell types and cell membrane receptors for their potential in targeting, immunomodulation and overcoming drug resistance in cancer.

Overcoming the Brain Barriers: From Immune Cells to Nanoparticles

Nanoparticulate carriers, often referred to as nanoparticles (NPs), represent an important pharmacological advance for drug protection and tissue-specific drug delivery. Accessing the central nervous system (CNS), however, is a complex process regulated by mainly three brain barriers. While some leukocyte (i.e., immune cell) subsets are equipped with the adequate molecular machinery to infiltrate the CNS in physiological and/or pathological contexts, the successful delivery of NPs into the CNS remains hindered by the tightness of the brain barriers. Here, we present an overview of the three major brain barriers and the mechanisms allowing leukocytes to migrate across each of them. We subsequently review different immune-inspired and -mediated strategies to deliver NPs into the CNS. Finally, we discuss the prospect of exploiting leukocyte trafficking mechanisms for further progress.

Exosome-like Nanovectors for Drug Delivery in Cancer

Cancer treatment still represents a formidable challenge, despite substantial advancements in available therapies being made over the past decade. One major issue is poor therapeutic efficacy due to lack of specificity and low bioavailability. The progress of nanotechnology and the development of a variety of nanoplatforms have had a significant impact in improving the therapeutic outcome of chemotherapeutics. Nanoparticles can overcome various biological barriers and localize at tumor site, while simultaneously protecting a therapeutic cargo and increasing its circulation time. Despite this, due to their synthetic origin, nanoparticles are often detected by the immune system and preferentially sequestered by filtering organs. Exosomes have recently been investigated as suitable substitutes for the shortcomings of nanoparticles due to their biological compatibility and particularly small size (i.e., 30-150 nm). In addition, exosomes have been found to play important roles in cell communication, acting as natural carriers of biological cargoes throughout the body. This review aims to highlight the use of exosomes as drug delivery vehicles for cancer and showcases the various attempts used to exploit exosomes with a focus on the delivery of chemotherapeutics and nucleic acids.

Nanoparticle Delivery of Immunostimulatory Agents for Cancer Immunotherapy

Immunostimulatory agents, including adjuvants, cytokines, and monoclonal antibodies, hold great potential for the treatment of cancer. However, their direct administration often results in suboptimal pharmacokinetics, vulnerability to biodegradation, and compromised targeting. More recently, encapsulation into biocompatible nanoparticulate carriers has become an emerging strategy for improving the delivery of these immunotherapeutic agents. Such approaches can address many of the challenges facing current treatment modalities by endowing additional protection and significantly elevating the bioavailability of the encapsulated payloads. To further improve the delivery efficiency and subsequent immune responses associated with current nanoscale approaches, biomimetic modifications and materials have been employed to create delivery platforms with enhanced functionalities. By leveraging nature-inspired design principles, these biomimetic nanodelivery vehicles have the potential to alter the current clinical landscape of cancer immunotherapy.

Systematic comparison of methods for determining the in vivo biodistribution of porous nanostructured injectable inorganic particles

With a wide variety of biodistribution measurement techniques reported in the literature, it is important to perform side-by-side comparisons of results obtained with different methods on the same particle platform, to determine differences across methods, highlight advantages and disadvantages, and inform methods selection according to specific applications. Inorganic nanostructured particles (INPs) have gained a central role in the development of injectable delivery vectors thanks to their controllable design, biocompatibility, and favorable degradation kinetic. Thus, accurate determination of in vivo biodistribution of INPs is a key aspect of developing and optimizing this class of delivery vectors. In this study, a systematic comparison of spectroscopy (inductively coupled plasma optical emission spectroscopy), fluorescence (in vivo imaging system, confocal microscopy, and plate reader), and radiolabeling (gamma counter)-based techniques is performed to assess the accuracy and sensitivity of biodistribution measurements in mice. Each method is evaluated on porous silicon particles, an established and versatile injectable delivery platform. Biodistribution is evaluated in all major organs and compared in terms of absolute results (%ID/g and %ID/organ when possible) and sensitivity (σ_%). Finally, we discuss how these results can be extended to inform method selection for other platforms and specific applications, with an outlook to potential benefit for pre-clinical and clinical studies. Overall, this study presents a new practical guide for selection of in vivo biodistribution methods that yield quantitative results. STATEMENT OF SIGNIFICANCE: The significance of this work lies in the use of a single platform to test performances of different biodistribution methods in vivo, with a strict quantitative metric. These results, united with the qualitative comparison of advantages and disadvantages of each technique, are aimed at supporting the rational choice of each different method according to the specific application, to improve the quantitative description of biodistribution results that will be published by others in the future.

Crosstalk between 14-3-3θ and AF4 enhances MLL-AF4 activity and promotes leukemia cell proliferation

PURPOSE

The t(4;11)(q21;q23) translocation characterizes a form of acute lymphoblastic leukemia with a poor prognosis. It results in a fusion gene encoding a chimeric transcription factor, MLL-AF4, that deregulates gene expression through a variety of still controversial mechanisms. To provide new insights into these mechanisms, we examined the interaction between AF4, the most common MLL fusion partner, and the scaffold protein 14-3-3θ, in the context of t(4;11)-positive leukemia.

METHODS

Protein-protein interactions were analyzed using immunoprecipitation and in vitro binding assays, and by fluorescence microscopy in t(4;11)-positive RS4;11 and MV4-11 leukemia cells and in HEK293 cells. Protein and mRNA expression levels were determined by Western blotting and RT-qPCR, respectively. A 5-bromo-2'-deoxyuridine assay and an annexin V/propidium iodide assay were used to assess proliferation and apoptosis rates, respectively, in t(4;11)-positive and control cells. Chromatin immunoprecipitation was performed to assess binding of 14-3-3θ and AF4 to a specific promoter element.

RESULTS

We found that AF4 and 14-3-3θ are nuclear interactors, that 14-3-3θ binds Ser⁵⁸⁸ of AF4 and that 14-3-3θ forms a complex with MLL-AF4. In addition, we found that in t(4;11)-positive cells, 14-3-3θ knockdown decreased the expression of MLL-AF4 target genes, induced apoptosis and hampered cell proliferation. Moreover, we found that 14-3-3θ knockdown impaired the recruitment of AF4, but not of MLL-AF4, to target chromatin. Overall, our data indicate that the activity of the chimeric transcription factor MLL-AF4 depends on the cellular availability of 14-3-3θ, which triggers the transactivating function and subsequent degradation of AF4.

CONCLUSIONS

From our data we conclude that the scaffold protein 14-3-3θ enhances the aberrant activity of the chimeric transcription factor MLL-AF4 and, therefore, represents a new player in the molecular pathogenesis of t(4;11)-positive leukemia and a new promising therapeutic target.

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

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

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

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

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.

Trends towards Biomimicry in Theranostics

Over the years, imaging and therapeutic modalities have seen considerable progress as a result of advances in nanotechnology. Theranostics, or the marrying of diagnostics and therapy, has increasingly been employing nano-based approaches to treat cancer. While first-generation nanoparticles offered considerable promise in the imaging and treatment of cancer, toxicity and non-specific distribution hindered their true potential. More recently, multistage nanovectors have been strategically designed to shield and carry a payload to its intended site. However, detection by the immune system and sequestration by filtration organs (i.e., liver and spleen) remains a major obstacle. In an effort to circumvent these biological barriers, recent trends have taken inspiration from biology. These bioinspired approaches often involve the use of biologically-derived cellular components in the design and fabrication of biomimetic nanoparticles. In this review, we provide insight into early nanoparticles and how they have steadily evolved to include bioinspired approaches to increase their theranostic potential.

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

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

Strategies for the enhanced intracellular delivery of nanomaterials

The intracellular delivery of nanomaterials and drugs has been attracting increasing research interest, mainly because of their important effects and functions in several organelles. Targeting specific organelles can help treat or decrease the symptoms of diabetes, cancer, infectious, and autoimmune diseases. Tuning biological and chemical properties enables the creation of functionalized nanomaterials with enhanced intracellular uptake, ability to escape premature lysosome degradation, and to reach a specific target. Here, we provide an update of recent advances in the intracellular delivery mechanisms that could help drugs reach their target more efficiently.

Design and Development of Biomimetic Nanovesicles Using a Microfluidic Approach

The advancement of nanotechnology toward more sophisticated bioinspired approaches has highlighted the gap between the advantages of biomimetic and biohybrid platforms and the availability of manufacturing processes to scale up their production. Though the advantages of transferring biological features from cells to synthetic nanoparticles for drug delivery purposes have recently been reported, a standardizable, batch-to-batch consistent, scalable, and high-throughput assembly method is required to further develop these platforms. Microfluidics has offered a robust tool for the controlled synthesis of nanoparticles in a versatile and reproducible approach. In this study, the incorporation of membrane proteins within the bilayer of biomimetic nanovesicles (leukosomes) using a microfluidic-based platform is demonstrated. The physical, pharmaceutical, and biological properties of microfluidic-formulated leukosomes (called NA-Leuko) are characterized. NA-Leuko show extended shelf life and retention of the biological functions of donor cells (i.e., macrophage avoidance and targeting of inflamed vasculature). The NA approach represents a universal, versatile, robust, and scalable tool, which is extensively used for the assembly of lipid nanoparticles and adapted here for the manufacturing of biomimetic nanovesicles.

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

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

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

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

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

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.

Lipid-polymer hybrid nanocarriers for delivering cancer therapeutics

Cancer remained a major cause of death providing diversified challenges in terms of treatment including non-specific toxicity, chemoresistance and relapse. Nanotechnology- based delivery systems grabbed tremendous attention for delivering cancer therapeutics as they provide benefits including controlled drug release, improved biological half-life, reduced toxicity and targeted delivery. Majority of the nanocarriers consists of either a polymer or a lipid component along with other excipients to stabilize the colloidal system. Lipid-based systems provide advantages like better entrapment efficiency, scalability and low- cost raw materials, however, suffer from limitations including instability, a burst release of the drug, and limited surface functionalization. On the other hand, polymeric systems provide an excellent diversity of chemical modifications, stability, controlled release, however limited drug loading capacities and scale up limit their use. Hybrid nanocarriers consisting of lipid and polymer were able to overcome some of these disadvantages while retaining the advantages of both the systems. Designing a stable lipid-polymer hybrid system requires a thorough understanding of the material properties and their behavior in in vitro and in vivo environments. This review highlights the current status and future prospects of lipid-polymer hybrid systems with a particular focus on cancer nanotherapeutics.

A chloroquine-induced macrophage-preconditioning strategy for improved nanodelivery

Site-specific localization is critical for improving the therapeutic efficacy and safety of drugs. Nanoparticles have emerged as promising tools for localized drug delivery. However, over 90% of systemically injected nanocarriers typically accumulate in the liver and spleen due to resident macrophages that form the mononuclear phagocyte system. In this study, the clinically approved antimalarial agent chloroquine was shown to reduce nanoparticle uptake in macrophages by suppressing endocytosis. Pretreatment of mice with a clinically relevant dose of chloroquine substantially decreased the accumulation of liposomes and silicon particles in the mononuclear phagocyte system and improved tumoritropic and organotropic delivery. The novel use of chloroquine as a macrophage-preconditioning agent presents a straightforward approach for addressing a major barrier in nanomedicine. Moreover, this priming strategy has broad applicability for improving the biodistribution and performance of particulate delivery systems. Ultimately, this study defines a paradigm for the combined use of macrophage-modulating agents with nanotherapeutics for improved site-specific delivery.

Engineered biomimetic nanovesicles show intrinsic anti-inflammatory properties for the treatment of inflammatory bowel diseases

Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, is a chronic inflammatory condition of the gastrointestinal (GI) tract. Currently, it is treated with immunosuppressant or biologics that often induce severe adverse effects. Thus, there is an urgent clinical need for more specific treatments. To provide a valid therapeutic tool for IBD therapy, in this work we developed biomimetic nanovesicles by manipulating leukocyte membranes to exploit mechanisms of T-cell recruitment during inflammation. A subset of T-lymphocytes participates in homing to inflamed tissue in the gastrointestinal tract by overexpressing the α4β7 integrin, which is responsible for binding to its receptor on the endothelial membrane, the mucosal addressin cell adhesion molecule 1. Based on this principle, we engineered biomimetic vesicles, referred to as specialized leukosomes (SLKs), which are leukocyte-like carriers 'doped' with the α4β7 integrin over-induced in purified immune cells. We tested SLKs in an in vivo murine model of IBD induced by treatment with dextran sulfate sodium. Notably, treatment of IBD mice with SLKs allowed us to observe a reduction of inflammation (favorable modulation of both pro- and anti-inflammatory genes, as well as reduction of immune cells infiltration into the colon tissue), and a consequent enhanced intestinal repair (low epithelial damage). In this study, we demonstrate that biological-derived nanoparticles can be used not only as naturally targeted drug delivery systems, but also as nano-therapeutics endowed with intrinsic anti-inflammatory properties.

Cell membrane coated nanoparticles: next-generation therapeutics

Cell membrane coated nanoparticles (NPs) is a biomimetic strategy developed to engineer therapeutic devices consisting of a NP core coated with membrane derived from natural cells such as erythrocytes, white blood cells, cancer cells, stem cells, platelets or bacterial cells. These biomimetic NPs have gained a lot of attention recently owing to their cell surface mimetic features and tailored nanomaterial characteristics. They have shown strong potential in diagnostic and therapeutic applications including those in drug delivery, immune modulation, vaccination and detoxification. Herein we review the various types of cell membrane coated NPs reported in the literature and the unique strengths of these biomimetic NPs with an emphasis on how these bioinspired camouflage strategies have led to improved therapeutic efficacy. We also highlight the recent progress made by each platform in advancing healthcare and precis the major challenges associated with these NPs.

Bio-inspired engineering of cell- and virus-like nanoparticles for drug delivery

The engineering of future generations of nanodelivery systems aims at the creation of multifunctional vectors endowed with improved circulation, enhanced targeting and responsiveness to the biological environment. Moving past purely bio-inert systems, researchers have begun to create nanoparticles capable of proactively interacting with the biology of the body. Nature offers a wide-range of sources of inspiration for the synthesis of more effective drug delivery platforms. Because the nano-bio-interface is the key driver of nanoparticle behavior and function, the modification of nanoparticles' surfaces allows the transfer of biological properties to synthetic carriers by imparting them with a biological identity. Modulation of these surface characteristics governs nanoparticle interactions with the biological barriers they encounter. Building off these observations, we provide here an overview of virus- and cell-derived biomimetic delivery systems that combine the intrinsic hallmarks of biological membranes with the delivery capabilities of synthetic carriers. We describe the features and properties of biomimetic delivery systems, recapitulating the distinctive traits and functions of viruses, exosomes, platelets, red and white blood cells. By mimicking these biological entities, we will learn how to more efficiently interact with the human body and refine our ability to negotiate with the biological barriers that impair the therapeutic efficacy of nanoparticles.

The Emerging Role of Nanotechnology in Cell and Organ Transplantation

Transplantation is often the only choice many patients have when suffering from end-stage organ failure. Although the quality of life improves after transplantation, challenges, such as organ shortages, necessary immunosuppression with associated complications, and chronic graft rejection, limit its wide clinical application. Nanotechnology has emerged in the past 2 decades as a field with the potential to satisfy clinical needs in the area of targeted and sustained drug delivery, noninvasive imaging, and tissue engineering. In this article, we provide an overview of popular nanotechnologies and a summary of the current and potential uses of nanotechnology in cell and organ transplantation.

Nanoantibiotics: a new paradigm for the treatment of surgical infection

Infections following orthopedic device implantations often impose a substantial health burden and result in high medical costs. Currently, preventative methods are often employed following an orthopedic implant to reduce risk of infection; however, contamination of the surgical site can still occur. Although antibiotics have demonstrated a substantial reduction in bacterial growth and maintenance, biofilm formation around the implant can often minimize efficacy of the antibiotic. Recently, nanotechnology has garnered significant interest, resulting in the development of several antibiotic delivery strategies that exhibit extended release and increased efficacy. In this review, treatment methods of orthopedic-device-related infections will be discussed and an overview of antimicrobial-based nanotechnologies will be provided. Specifically, nonmetal-, metal- and oxide-based nanotechnologies, incorporating antibacterial strategies, will be discussed.

Multistaged Nanovaccines Based on Porous Silicon@Acetalated Dextran@Cancer Cell Membrane for Cancer Immunotherapy

Immunoadjuvant porous silicon (PSi)-based nanovaccines are prepared by nanoprecipitation in a glass capillary microfluidics device. Vesicles, derived from cancer cell membranes encapsulating thermally oxidized PSi nanoparticles or PSi-polymer nanosystems binding a model antigen, are biocompatible over a wide range of concentrations, and show immunostimulant properties in human cells, promoting the expression of co-stimulatory signals and the secretion of pro-inflammatory cytokines.

Post-nano strategies for drug delivery: Multistage porous silicon microvectors

Nanodelivery systems usually improve the biodistribution of drugs, leading to reduced side effects and enhanced therapeutic efficacy. However, only a small portion of the injected nanoparticle dose accumulates in pathological tissue. Challenges in drug delivery arise due to a multitude of transport obstacles in the body, including the endothelium, the extracellular matrix, and the cell membrane. In general, nanoparticles are designed to overcome only a few biological barriers, making them inadequate for localized drug delivery. Accordingly, a multifunctional and multicomponent systems are required to effectively address a wide variety of transport obstacles. A suitable approach to obtain high levels of multifunctionality is to bring together the nanoscale with the microscale, resulting in post-nano strategies for drug delivery. This review discusses several such post-nano approaches, with an emphasis on the multistage vector (MSV) platform. The MSV consists of three components on different spatial scales, each intended to address biological barriers that exist in a specific compartment in the body. The first stage vector is a microparticle that is designed to navigate in the vascular compartment. The second stage vector consists of nanoparticles that are released from the microparticle into the tissue interstitium, where they address biological barriers in extracellular and intracellular compartments. The final component of the system is a small molecule therapeutic agent. A new generation of microparticle-based strategies with expanded applications has recently been developed, including injectable nanoparticle generators and silicon particles for immunotherapy. Notably, the advantage of incorporating microstructures in drug delivery vehicles is apparent from the observation that superior functionality only appears on the microscale, highlighting the inherent functional limitations of nanostructures.

Biomimetic carriers mimicking leukocyte plasma membrane to increase tumor vasculature permeability

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