Red blood cell-derived nanovesicles for safe and efficient macrophage-targeted drug delivery in vivo

Erythrocyte membrane vesicles as drug delivery systems: A systematic review of preclinical studies on biodistribution and pharmacokinetics

This systematic review aims to summarize the development of erythrocyte membrane vesicles (EMVs) as drug delivery carriers, with a focus on elucidating their fate in terms of biodistribution and pharmacokinetics in preclinical studies. The PubMed database was systematically reviewed to search for original peer-reviewed published studies on the use of EMVs for drug delivery to summarize the preclinical findings, following the PRISMA guidelines. A total of 142 articles matched the selection criteria and were included in the review. For each study, the following parameters were extracted: type of active pharmaceutical ingredient (API) encapsulated into EMVs, EMVs-API formulation method and final particle size, EMVs surface modifications for active targeting, cell lines and animal models used in the study, crucial treatment data, biodistribution data and finally, where applicable, data about the EMVs circulation time and blood half-life. EMVs size did not vary significantly among the different formulation methods. A complete list of cell lines and animal models used is provided. Circulation times and data for blood half-life were grouped per animal type. For the most commonly used animal type, BALB/c mice, the average half-life of EMV-API was calculated to be 10.4 h, and in all cases, up to a 10-fold increase was observed compared with that of free API. Surface modifications did not drastically change the circulation time but did improve target tissue accumulation. The most critical weaknesses in the analysed studies were identified. Key points for future studies are provided to fill the current knowledge gaps and improve the quality of publications.

Therapeutic Potential of Arginine-Loaded Red Blood Cell Nanovesicles Targeting Obese Asthma

Purpose: The role of the gut microbiomes has been emphasized in the pathogenesis of obese asthma (OA). However, the molecular mechanism of airway dysfunction underlying OA has not yet been fully elucidated. The effects of microbiomes on arginine metabolism in relation to lung functions and a novel method for delivering arginine to lung tissue based on arginine-loaded red blood cell (RBC)-derived nanovesicles (NVs) (NVArg) will be investigated. Materials and Methods: Inflammatory status, amino acid profiles, and microbial diversity were evaluated in 20 adult patients with OA compared to 30 adult patients with non-OA (NOA) and 10 healthy control (HC) groups. Changes in gut or lung microbial composition that altered arginine metabolism in relation to airway inflammation were investigated in an OA mouse model in vivo. Additionally, this study evaluated the delivery of arginine to lung tissue utilizing NVArg in vivo and in vitro. Results: Significantly increased Bacteroides abundance but decreased serum arginine concentration with lower forced exhaled volume at 1 s (FEV1) (%) was noted in the OA group compared to the NOA and HC groups. In mouse experiments, when OA mice were given living bacteria from normal control (NC) mice, lung arginine concentration and airway resistance were restored. However, the administration of arginine or its metabolite (citrulline) did not increase the arginine levels in the lung tissues. We therefore created NVArg, which successfully delivered arginine into the cytoplasm of the airway epithelial cell line in vitro. Oral administration of NVArg for OA mice significantly induced the AMP-activated protein kinase (AMPK) and endothelial nitric oxide synthase (eNOS) pathways in airway epithelial cells, which reduced airway resistance and inflammation. Conclusion: These findings suggest that microbiomes contribute to airway dysfunction by regulating arginine metabolism, whereas NVArg treatment may be a potential option for managing OA.

Recent Advances and Challenges in Targeted Drug Delivery Using Biofunctional Coatings

Globally, clinics are overwhelmed by drugs targeting undesired cells and organs, causing adverse systemic effects on the body. This shortfall in targeting specificity, safety, and efficiency has noticeably contributed to the failure of the bench-to-bedside transition. Activation or impairment of immune activity due to a misdirected drug and its carrier fuels complications, extending the range of destruction which can convert the course of disease into a life-threatening route. To address these great challenges, advanced coatings as indispensable components of future medicine have been investigated over the last few decades for precisely targeted drug delivery to achieve favorable prognoses in the treatment of a broad spectrum of diseases. Complemented by advancements in the pharmacological parameters, these systems hold great promise for the field. This chapter aims to discuss recent progress on new coatings for targeted drug delivery and the parameters for manufacturing these platforms for their cargo based on major determinants such as biocompatibility and bioactivity. A brief overview of the various applications of targeted drug delivery with functional coatings is also provided to offer a new perspective on the field.

A Review: Surface Engineering of Lipid-Based Drug Delivery Systems

This review explores the evolution of lipid-based nanoparticles (LBNPs) for drug delivery (DD). Herein, LBNPs are classified into liposomes and cell membrane-based nanoparticles (CMNPs), each with unique advantages and challenges. Conventional LBNPs possess drawbacks such as poor targeting, quick clearance, and limited biocompatibility. One of the possible alternatives to overcome these challenges is surface modification of nanoparticles (NPs) with materials such as polyethylene glycol (PEG), aptamers, antibody fragments, peptides, CD44, hyaluronic acid, folic acid, palmitic acid, and lactoferrin. Thus, the main focus of this review will be on the different surface modifications that enable LBNPs to have beneficial properties for DD, such as enhancing mass transport properties, immune evasion, improved stability, and targeting. Moreover, various CMNPs are explored used for DD derived from cells such as red blood cells (RBCs), platelets, leukocytes, cancer cells, and stem cells, highlighting their unique natural properties (e.g., biocompatibility and ability to evade the immune system). This discussion extends to the biomimicking of hybrid NPs accomplished through the surface coating of synthetic (mainly polymeric) NPs with different cell membranes. This review aims to provide a comprehensive resource for researchers on recent advances in the field of surface modification of LBNPs and CMNPs. Overall, this review provides valuable insights into the dynamic field of lipid-based DD systems.

Bioinspired and biomimetic cancer-cell-derived membrane nanovesicles for preclinical tumor-targeted nanotheranostics

Bioinspired cell-membrane-camouflaged nanohybrids have been proposed to enhance tumor targeting by harnessing their immune escape and self-recognition abilities. In this study, we introduce cancer-cell-derived membrane nanovesicles (CCMVs) integrated with gold nanorods (AuVNRs) in addition to therapeutic and imaging cargos such as doxorubicin and indocyanine green. This approach enhances targeted tumor imaging and enables synergistic chemo-phototherapeutics for solid tumors. CCMVs demonstrate significant tumor penetration and retention, serving as nanotheranostics with accessible surface biomarkers, biomimicking properties, and homologous targeting abilities. By evading uptake by the mononuclear phagocytic system, CCMVs can diffuse into the deep tumor core, leading to precise tumor reduction while preserving the surrounding healthy tissues. Notably, intravenous administration of these theranostic agents ensures biocompatibility, as evidenced by a survival period of approximately two months (up to 63 days) without any observed side effects. Our findings underscore the diagnostic and therapeutic potential of this biomimetic nanotheranostics platform.

'Passive' nanoparticles for organ-selective systemic delivery: design, mechanism and perspective

Nanotechnology has shown tremendous success in the drug delivery field for more effective and safer therapy, and has recently enabled the clinical approval of RNA medicine, a new class of therapeutics. Various nanoparticle strategies have been developed to improve the systemic delivery of therapeutics, among which surface modification of targeting ligands on nanoparticles has been widely explored for 'active' delivery to a specific organ or diseased tissue. Meanwhile, compelling evidence has recently been reported that organ-selective targeting may also be achievable by systemic administration of nanoparticles without surface ligand modification. In this Review, we highlight this unique set of 'passive' nanoparticles and their compositions and mechanisms for organ-selective delivery. In particular, the lipid-based, polymer-based, and biomimetic nanoparticles with tropism to different specific organs after intravenous administration are summarized. The underlying mechanisms (e.g., protein corona and size effect) of these nanosystems for organ selectivity are also extensively discussed. We further provide perspectives on the opportunities and challenges in this exciting area of organ-selective systemic nanoparticle delivery.

Maleimide as the PEG end-group promotes macrophage-targeted drug delivery of PEGylated nanoparticles in vivo by enhancing interaction with circulating erythrocytes

Radiotherapy (IR) is capable of enhancing antitumor immune responses. However, IR treatment also aggravates the infiltration of peripheral macrophages into the tumor, resulting in reversing the therapeutic effects of antitumor immunity. Thus, a strategy to effectively prevent tumor infiltration by macrophages may further improved the therapeutic efficacy of radiotherapy. Herein, we found that PEGylated solid lipid nanoparticles with maleimide as PEG end-group (SLN-PEG-Mal) show significantly enhanced adsorption onto RBCs through reacting with reactive sulfhydryl groups on RBCs' surface both in vitro and in vivo, and caused significant changes in the surface properties and morphology of RBCs. These RBCs adsorbed by SLN-PEG-Mal were rapidly removed from circulation due to efficient engulfment by reticuloendothelial macrophages, supporting the usefulness of SLN-PEG-Mal for macrophage-targeted drug delivery. While lacking the use of radioisotope tracing (considered the gold standard for PK/BD studies), our data align with the expected pathway of host defense activation through surface-loaded RBCs. Importantly, injection of paclitaxel-loaded SLN-PEG-Mal effectively inhibited the tumor-infiltration by macrophages, and significantly improved the antitumor immune responses in tumor-bearing mice treated with low-dose irradiation. This study provides insights into the effects of maleimide as PEG end-group on enhancing the interaction between PEGylated nanoparticles and RBCs and offers an effective strategy to inhibit tumor infiltration by circulating macrophages.

Tumor-associated macrophages in nanomaterial-based anti-tumor therapy: as target spots or delivery platforms

Targeting tumor-associated macrophages (TAMs) has emerged as a promising approach in cancer therapy. This article provides a comprehensive review of recent advancements in the field of nanomedicines targeting TAMs. According to the crucial role of TAMs in tumor progression, strategies to inhibit macrophage recruitment, suppress TAM survival, and transform TAM phenotypes are discussed as potential therapeutic avenues. To enhance the targeting capacity of nanomedicines, various approaches such as the use of ligands, immunoglobulins, and short peptides are explored. The utilization of live programmed macrophages, macrophage cell membrane-coated nanoparticles and macrophage-derived extracellular vesicles as drug delivery platforms is also highlighted, offering improved biocompatibility and prolonged circulation time. However, challenges remain in achieving precise targeting and controlled drug release. The heterogeneity of TAMs and the variability of surface markers pose hurdles in achieving specific recognition. Furthermore, the safety and clinical applicability of these nanomedicines requires further investigation. In conclusion, nanomedicines targeting TAMs hold great promise in cancer therapy, offering enhanced specificity and reduced side effects. Addressing the existing limitations and expanding our understanding of TAM biology will pave the way for the successful translation of these nano-therapies into clinical practice.

Multifunctional nanostructures: Intelligent design to overcome biological barriers

Over the past three decades, nanoscience has offered a unique solution for reducing the systemic toxicity of chemotherapy drugs and for increasing drug therapeutic efficiency. However, the poor accumulation and pharmacokinetics of nanoparticles are some of the key reasons for their slow translation into the clinic. The is intimately linked to the non-biological nature of nanoparticles and the aberrant features of solid cancer, which together significantly compromise nanoparticle delivery. New findings on the unique properties of tumors and their interactions with nanoparticles and the human body suggest that, contrary to what was long-believed, tumor features may be more mirage than miracle, as the enhanced permeability and retention based efficacy is estimated to be as low as 1%. In this review, we highlight the current barriers and available solutions to pave the way for approved nanoformulations. Furthermore, we aim to discuss the main solutions to solve inefficient drug delivery with the use of nanobioengineering of nanocarriers and the tumor environment. Finally, we will discuss the suggested strategies to overcome two or more biological barriers with one nanocarrier. The variety of design formats, applications and implications of each of these methods will also be evaluated.

Preparation of oral nanoparticles of Perillae Fructus oil and prevention application of cold stress in mice

Perillae Fructus oil has an important function in relieving cold stress. However, its application in this aspect has still been restricted because of instability and low bioavailability. In this study, Perillae Fructus oil was extracted through Soxhlet extraction, analyzed through gas chromatography-mass spectrometry (GC-MS), and nanopackaged into a yeast shell for the preparation of nanoparticles for oral administration. The characteristics of the nanoparticles were investigated using a Malvern zeta-size nanoinstrument, scanning electron microscopy (SEM), and high-performance liquid chromatography (HPLC). Then, the roles of orally administered nanoparticles in relieving cold stress were evaluated by investigating blood physiological and biochemical indexes in mice. The results showed that the oil yield from Perillae Fructus and shell yield from yeast cells were ~48.37% and ~16.87%, respectively. Approximately 89.21% of the added oil was packaged into the yeast shell to form nanoparticles with an average diameter of 316.74 nm and a surface charge of +2.9 mV. The nanoparticles were stable in simulated gastric acid and could be effectively released in simulated intestinal fluid with an efficiency of ~91.34%. After oral administration of nanoparticles, the mouse blood indexes of white blood cells (WBCs), superoxide dismutase (SOD) activity, and malonaldehyde (MDA) content were recovered compared to those in model mice, with a more remarkable effect than oral administration of free Perillae Fructus oil. Overall, the stability and bioavailability were improved by packaging Perillae Fructus oil into a yeast shell. These nanoparticles are a new agent for the prevention of cold stress.

Reconstructed membrane vesicles from the microalga Dunaliella as a potential drug delivery system

The aim of this biophysical study is to characterize reconstructed membrane vesicles obtained from microalgae in terms of their morphology, properties, composition, and ability to transport a model drug. The reconstructed vesicles were either emptied or non-emptied and exhibited a non-uniform distribution of spherical surface structures that could be associated with surface coat proteins, while in between there were pore-like structures of up to 10 nm that could contribute to permeability. The reconstructed vesicles were very soft and hydrophilic, which could be attributed to their composition. The vesicles were rich in proteins and were mostly derived from the cytoplasm and chloroplasts. We demonstrated that all lipid classes of D. tertiolecta are involved in the formation of the reconstructed membrane vesicles, where they play fundamental role to maintain the vesicle structure. The vesicles appeared to be permeable to calcein, impermeable to FITC-ovalbumin, and semipermeable to FITC-concanavalin A, which may be due to a specific surface interaction with glucose/mannose units that could serve as a basis for the development of drug carriers. Finally, the reconstructed membrane vesicles could pave a new way as sustainable and environmentally friendly marine bioinspired carriers and serve for studies on microtransport of materials and membrane-related processes contributing to advances in life sciences and biotechnology.

Design of erythrocyte-derived carriers for bioimaging applications

Erythrocytes are physiological entities that have been exploited in both preclinical and clinical trials for the delivery of exogenous agents. Over the years, diverse erythrocyte-derived carriers (ECs) have been developed with related patents granted for industrial and commercial purposes. However, most ECs have only been exploited for drug delivery. Serious discussions regarding their applications in imaging are scarce. This article reviews the role of ECs in enhancing imaging efficiency and subsequently delineates strategies for engineering and optimising their preclinical and clinical performance. With a snapshot of the latest developments and use of ECs in imaging, directions to streamline the clinical translation of related technologies can be attained for future research.

Development of ligand modified erythrocyte coated polydopamine nanomedicine to codeliver chemotherapeutic agent and oxygen for chemo-photothermal synergistic cancer therapy

The use of conventional chemotherapy often faces limitations such as severe side effects, weak tumor tissue specificity, and the development of multidrug resistance. To conquer these challenges, numerous novel drug carriers have been designed in recent years. However, due to the complex processes of tumor development, metastasis and recurrence, single chemotherapy cannot fulfill the goals of clinical diverse treatment. In this work, by utilizing the inherent characteristics of surface-modified erythrocyte and the outstanding photothermal conversion capability of polydopamine (PDA), we designed and constructed a biomimetic multifunctional nanomedicine DPPR NPs to codeliver chemotherapeutic agent doxorubicin (DOX) and oxygen. The results showed that DPPR NPs exhibited inspiring features including nanoscale droplet size, good physicochemical stability, and sustained, pH-, and NIR triggered drug release behavior. It can dramatically prolong the systematic circulation time and elevated the drug accumulated level in the tumor site. Moreover, DPPR NPs could be effectively internalized into tumor cells and destroyed the intracellular redox balance to mediate cell apoptosis. It exerted excellent in vivo tumor targeting effect, photothermal conversion efficiency, ultrasound imaging responses, antitumor efficacy, and good compatibility. In summary, DPPR NPs provide a biomimetic drug delivery platform to organically combine chemotherapy and photothermal therapy for precise cancer treatment.

Protein corona: challenges and opportunities for targeted delivery of nanomedicines

INTRODUCTION

Targeted drug delivery has been widely explored as a promising way to improve the performance of nanomedicines. However, protein corona formed on the nano-surface represents a major issue that has great impacts on the in vivo fate of targeting nanomedicines, which has been overlooked in the past. With the increasing understanding of protein corona in the recent decade, many efforts have been made to improve targeting efficacy.

AREAS COVERED

In this review, we briefly summarize insights of targeted delivery systems inspired by protein corona, and discuss the promising strategies to regulate protein corona for better targeting.

EXPERT OPINION

The interaction between nanomedicines and endogenous proteins brings great uncertainty and challenges, but it also provides great opportunities for the development of targeting nanomedicines at the same time. With increasing understanding of protein corona, the strategies to regulate protein corona pave new avenues for the development of targeting nanomedicines.

Synthetic cells in biomedical applications

Synthetic cells are engineered vesicles that can mimic one or more salient features of life. These features include directed localization, sense-and-respond behavior, gene expression, metabolism, and high stability. In nanomedicine, many of these features are desirable capabilities of drug delivery vehicles but are difficult to engineer. In this focus article, we discuss where synthetic cells offer unique advantages over nanoparticle and living cell therapies. We review progress in the engineering of the above life-like behaviors and how they are deployed in nanomedicine. Finally, we assess key challenges synthetic cells face before being deployed as drugs and suggest ways to overcome these challenges. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures.

Design and Optimization of the Circulatory Cell-Driven Drug Delivery Platform

Achievement of high targeting efficiency for a drug delivery system remains a challenge of tumor diagnoses and nonsurgery therapies. Although nanoparticle-based drug delivery systems have made great progress in extending circulation time, improving durability, and controlling drug release, the targeting efficiency remains low. And the development is limited to reducing side effects since overall survival rates are mostly unchanged. Therefore, great efforts have been made to explore cell-driven drug delivery systems in the tumor area. Cells, particularly those in the blood circulatory system, meet most of the demands that the nanoparticle-based delivery systems do not. These cells possess extended circulation times and innate chemomigration ability and can activate an immune response that exerts therapeutic effects. However, new challenges have emerged, such as payloads, cell function change, cargo leakage, and in situ release. Generally, employing cells from the blood circulatory system as cargo carriers has achieved great benefits and paved the way for tumor diagnosis and therapy. This review specifically covers (a) the properties of red blood cells, monocytes, macrophages, neutrophils, natural killer cells, T lymphocytes, and mesenchymal stem cells; (b) the loading strategies to balance cargo amounts and cell function balance; (c) the cascade strategies to improve cell-driven targeting delivery efficiency; and (d) the features and applications of cell membranes, artificial cells, and extracellular vesicles in cancer treatment.

In Vitro Generation of Red Blood Cells from Stem Cell and Targeted Therapy

Red blood cell (RBC) transfusion is a common therapeutic intervention, which is necessary for patients with emergency or hematological disorders to reduce morbidity and mortality. However, to date, blood available for transfusion is a limited resource, and the transfusion coverage system still depends on the volunteer-based collection system. The scarcity of blood supplies commonly develops because of local conditions that transiently affect collection. Moreover, donor-derived infectious disease transmission events also remain a risk. Thus, there is a huge demand for artificial blood. The production of cultured RBCs from stem cells is slowly emerging as a potential alternative to donor-derived red cell transfusion products. In this concise review, we summarize the recent in vitro expansion of RBCs from various stem cell sources, targeted therapy, prospects, and remaining challenges.

Red Blood Cell Membrane-Camouflaged Tedizolid Phosphate-Loaded PLGA Nanoparticles for Bacterial-Infection Therapy

Multiple drug resistance (MDR) in bacterial infections is developed with the abuse of antibiotics, posing a severe threat to global health. Tedizolid phosphate (TR-701) is an efficient prodrug of tedizolid (TR-700) against gram-positive bacteria, including methicillin-sensitive staphylococcus aureus (MSSA) and methicillin-resistant staphylococcus aureus (MRSA). Herein, a novel drug delivery system: Red blood cell membrane (RBCM) coated TR-701-loaded polylactic acid-glycolic acid copolymer (PLGA) nanoparticles (RBCM-PLGA-TR-701NPs, RPTR-701Ns) was proposed. The RPTR-701Ns possessed a double-layer core-shell structure with 192.50 ± 5.85 nm in size, an average encapsulation efficiency of 36.63% and a 48 h-sustained release in vitro. Superior bio-compatibility was confirmed with red blood cells (RBCs) and HEK 293 cells. Due to the RBCM coating, RPTR-701Ns on one hand significantly reduced phagocytosis by RAW 264.7 cells as compared to PTR-701Ns, showing an immune escape effect. On the other hand, RPTR-701Ns had an advanced exotoxins neutralization ability, which helped reduce the damage of MRSA exotoxins to RBCs by 17.13%. Furthermore, excellent in vivo bacteria elimination and promoted wound healing were observed of RPTR-701Ns with a MRSA-infected mice model without causing toxicity. In summary, the novel delivery system provides a synergistic antibacterial treatment of both sustained release and bacterial toxins absorption, facilitating the incorporation of TR-701 into modern nanotechnology.

The double-edged sword effect of macrophage targeting delivery system in different macrophage subsets related diseases

Background

Monocyte/macrophage-targeting delivery systems (MTDSs) have been focused upon as an emerging routine for delivering drugs to treat various macrophage-related diseases. However, the ability of MTDSs to distinguish different macrophage-related diseases and their impact on macrophage function and disease progression have not been systematically revealed, which is important for actively targeted therapeutic or diagnostic strategies.

Results

Herein, we used dextran-modified polystyrene nanoparticles (DEX-PS) to demonstrate that modification of nanoparticles by dextran can specifically enhance their recognition by M2 macrophages in vitro, but it is obstructed by monocytes in peripheral blood according to in vivo assays. DEX-PS not only targeted and became distributed in tumors, an M2 macrophage-related disease, but was also highly distributed in an M1 macrophage-related disease, namely acute peritonitis. Thus, DEX-PS acts as a double-edged sword in these two different diseases by reeducating macrophages to a pro-inflammatory phenotype.

Conclusions

Our results suggest that MTDSs, even those designed based on differential expression of receptors on specific macrophage subtypes, lack the ability to distinguish different macrophage subtype-related diseases in vivo. In addition to the potential impact of these carrier materials on macrophage function, studies of MTDSs should pay greater attention to the distribution of nanoparticles in non-target macrophage-infiltrated disease sites and their impact on disease processes.

Overcoming the Reticuloendothelial System Barrier to Drug Delivery with a "Don't-Eat-Us" Strategy

Overcoming the reticuloendothelial system (RES) has long been a vital challenge to nanoparticles as drug carriers. Modification of nanoparticles with polyethylene glycol helps them avoid clearance by macrophages but also suppresses their internalization by target cells. To overcome this paradox, we developed an RES-specific blocking system utilizing a "don't-eat-us" strategy. First, a CD47-derived, enzyme-resistant peptide ligand was designed and placed on liposomes (d-self-peptide-labeled liposome, DSL). After mainline administration, DSL was quickly adsorbed onto hepatic phagocyte membranes (including those of Kupffer cells and liver sinusoidal endothelial cells), forming a long-lasting mask that enclosed the cell membranes and thus reducing interactions between phagocytes and subsequently injected nanoparticles. Compared with blank conventional liposomes (CL), DSL blocked the RES at a much lower dose, and the effect was sustained for a much longer time, highly prolonging the elimination half-life of the subsequently injected nanoparticles. This "don't-eat-us" strategy by DSL was further verified on the brain-targeted delivery against a cryptococcal meningitis model, providing dramatically enhanced brain accumulation of the targeted delivery system and superior therapeutic outcome of model drug Amphotericin B compared with CL. Our study demonstrates a strategy that blocks the RES by masking phagocyte surfaces to prolong nanoparticle circulation time without excess modification and illustrates its utility in enhancing nanoparticle delivery.

Cells and cell derivatives as drug carriers for targeted delivery

For over a century, researchers have focused on how to optimize drug delivery. Systemic administration means that the drug becomes dilute and has the potential to diffuse to all tissues, which is only until the immune system steps in and rapidly clears it from blood circulation. Drug carriers are the solution for amplifying the intended effect and diminishing side effects. With drug carriers, tissue-specific drug delivery and controlled drug release is possible. Thus far, both synthetic and non-synthetic carriers exist. However, due to the numerous limitations of synthetic carriers, science has begun to concentrate on using live cells and cell-derivatives as drug carriers. The most problematic shortcomings of synthetic carriers are their limited biocompatibility and biodegradability. Most synthetic carriers are cytotoxic or induce immune responses. Moreover, synthetic carriers typically depend on passive diffusion and risk phagocytosis, further reducing their impact. On the other hand, live-cell carriers and their derivatives usually have a targeting mechanism and drug release is controlled, increasing the efficiency with which a drug accumulates and acts on a tissue. Still, both types of carriers face similar problems, including achieving high loading capacity, maintaining drug quality, efficiently accumulating in the target tissue, and minimizing side effects. This review aims to elucidate the advantages and disadvantages of each popular cell or cell-derived carrier and to spotlight novel solutions.

Functionalized erythrocyte-derived optical nanoparticles to target ephrin-B2 ligands

Over- or under-expression of erythropoietin-production human hepatocellular receptors (Eph) and their ligands are associated with various diseases. Therefore, these molecular biomarkers can potentially be used as binding targets for the delivery of therapeutic and/or imaging agents to cells characterized by such irregular expressions. We have engineered nanoparticles derived from erythrocytes and doped with the near-infrared (NIR) FDA-approved dye, indocyanine green. We refer to these nanoparticles as NIR erythrocyte-derived transducers (NETs). We functionalized the NETs with the ligand-binding domain of a particular Eph receptor, EphB1, to target the genetically modified human dermal microvascular endothelial cells (hDMVECs) with coexpression of EphB1 receptor and its ligand ephrin-B2. This cell model mimics the pathological phenotypes of lesional endothelial cells (ECs) in port wine stains (PWSs). Our quantitative fluorescence imaging results demonstrate that such functionalized NETs bind to the ephrin-B2 ligands on these hDMVECs in a dose-dependent manner that varies sigmoidally with the number density of the particles. These nanoparticles may potentially serve as agents to target PWS lesional ECs and other diseases characterized with over-expression of Eph receptors or their associated ligands to mediate phototherapy.

A multiscale flexible pressure sensor based on nanovesicle-like hollow microspheres for micro-vibration detection in non-contact mode

To detect micro-vibration, flexible pressure sensors require that the sensing materials possess superior sensitivity in non-contact sensing mode. One type of matter, nanovesicles, has the characteristics of hollow spheres and crack junctions in a single body, and provides an exciting bionic idea to explore high-sensitivity sensing materials. Hence, in this study, novel hollow microspheres with a hierarchical nanovesicle-like architecture are designed, prepared via a controlled strategy of adjusting the surface energy, and employed to fabricate multiscale flexible pressure sensors that display a high response sensitivity of 11.3 kPa-1 and a low detection limit of 5.5 Pa with good stability for 2500 cycles. The working mechanism can be deduced as the synergistic effects from the stress concentration of microstructural patterns and the successive deformation of the nanovesicle-like structure, which is revealed by controlled experiments and finite element method simulations. The as-assembled flexible pressure sensor is used to detect the dynamic micro-vibration signals caused by fluid motion (water flow and airflow) and inelastic/elastic collision in non-contact mode, revealing good sensitivity, repeatability and stability. This work provides theoretical and experimental evidence for the development of hierarchical structure-based highly sensitive flexible sensors in the future.