Surface functionalization of gold nanoparticles with red blood cell membranes

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.

Tumor Microenvironment Modulation by Cyclopamine Improved Photothermal Therapy of Biomimetic Gold Nanorods for Pancreatic Ductal Adenocarcinomas

Due to the rich stroma content and poor blood perfusion, pancreatic ductal adenocarcinoma (PDA) is a tough cancer that can hardly be effectively treated by chemotherapeutic drugs. Tumor microenvironment modulation or advanced design of nanomedicine to achieve better therapeutic benefits for PDA treatment was widely advocated by many reviews. In the present study, a new photothermal therapy strategy of PDA was developed by combination of tumor microenvironment modulation and advanced design of biomimetic gold nanorods. On one hand, biomimetic gold nanorods were developed by coating gold nanorods (GNRs) with erythrocyte membrane (MGNRs). It was shown that MGNRs exhibited significantly higher colloidal stability in vitro, stronger photothermal therapeutic efficacy in vitro, and longer circulation in vivo than GNRs. On the other hand, tumor microenvironment modulation by cyclopamine treatment successfully disrupted the extracellular matrix of PDA and improved tumor blood perfusion. Moreover, cyclopamine treatment significantly increased the accumulation of MGNRs in tumors by 1.8-fold and therefore produced higher photothermal efficiency in vivo than the control group. Finally, cyclopamine treatment combined with photothermal MGNRs achieved the most significant shrinkage of Capan-2 tumor xenografts among all the treatment groups. Therefore, with the integrated advantages of tumor microenvironment regulation and long-circulation biomimetic MGNRs, effective photothermal therapy of PDA was achieved. In general, this new strategy of combining tumor microenvironment modulation and advanced design of biomimetic nanoparticles might have great potential in PDA therapy.

Enzymes as key features in therapeutic cell mimicry

Cell mimicry is a nature inspired concept that aims to substitute for missing or lost (sub)cellular function. This review focuses on the latest advancements in the use of enzymes in cell mimicry for encapsulated catalysis and artificial motility in synthetic bottom-up assemblies with emphasis on the biological response in cell culture or more rarely in animal models. Entities across the length scale from nano-sized enzyme mimics, sub-micron sized artificial organelles and self-propelled particles (swimmers) to micron-sized artificial cells are discussed. Although the field remains in its infancy, the primary aim of this review is to illustrate the advent of nature-mimicking artificial molecules and assemblies on their way to become a complementary alternative to their role models for diverse biomedical purposes.

In Situ Capture of Bacterial Toxins for Antivirulence Vaccination

Antivirulence vaccination is a promising strategy for addressing bacterial infection that focuses on removing the harmful toxins produced by bacteria. However, a major challenge for creating vaccines against biological toxins is that the vaccine potency is often limited by lack of antigenic breadth, as most formulations have focused on single antigens, while most bacteria secrete a plethora of toxins. Here, a facile approach for generating multiantigenic nanotoxoids for use as vaccines against pathogenic bacteria by leveraging the natural affinity of virulence factors for cellular membranes is reported. Specifically, multiple virulent toxins from bacterial protein secretions are concurrently and naturally entrapped using a membrane-coated nanosponge construct. The resulting multivalent nanotoxoids are capable of delivering virulence factors together, are safe both in vitro and in vivo, and can elicit functional immunity capable of combating live bacterial infections in a mouse model. Despite containing the same bacterial antigens, the reported nanotoxoid formulation consistently outperforms a denatured protein preparation in all of the metrics studied, which underscores the utility of biomimetic nanoparticle-based neutralization and delivery. Overall this strategy helps to address major hurdles in the design of antivirulence vaccines, enabling increased antigenic breadth while maintaining safety.

Erythrocyte-Membrane-Enveloped Perfluorocarbon as Nanoscale Artificial Red Blood Cells to Relieve Tumor Hypoxia and Enhance Cancer Radiotherapy

Hypoxia, a common feature within many types of solid tumors, is known to be closely associated with limited efficacy for cancer therapies, including radiotherapy (RT) in which oxygen is essential to promote radiation-induced cell damage. Here, an artificial nanoscale red-blood-cell system is designed by encapsulating perfluorocarbon (PFC), a commonly used artificial blood substitute, within biocompatible poly(d,l-lactide-co-glycolide) (PLGA), obtaining PFC@PLGA nanoparticles, which are further coated with a red-blood-cell membrane (RBCM). The developed PFC@PLGA-RBCM nanoparticles with the PFC core show rather efficient loading of oxygen, as well as greatly prolonged blood circulation time owing to the coating of RBCM. With significantly improved extravascular diffusion within the tumor mass, owing to their much smaller nanoscale sizes compared to native RBCs with micrometer sizes, PFC@PLGA-RBCM nanoparticles are able to effectively deliver oxygen into tumors after intravenous injection, leading to greatly relieved tumor hypoxia and thus remarkably enhanced treatment efficacy during RT. This work thus presents a unique type of nanoscale RBC mimic for efficient oxygen delivery into solid tumors, favorable for cancer treatment by RT, and potentially other types of therapy as well.

Oxygen self-enriched nanoparticles functionalized with erythrocyte membranes for long circulation and enhanced phototherapy

In recent years, indocyanine green (ICG) encapsulated in different kinds of nano-carriers have been developed to overcome its short lifetime in vivo and non-selectivity in cancer cells. However, these nanoparticles are still easily recognized and captured by the reticuloendothelial system (RES) and the low singlet oxygen quantum (0.08) of ICG inevitably leads to a limited efficacy of phototherapy. To overcome these limitations, a novel oxygen self-enriched biomimetic red blood cell (RBC) was developed by cloaking albumin nanoparticles which contained ICG and perfluorocarbon (PFC) with RBC membranes. Due to the high oxygen capacity of PFC, the oxygen self-enriched nanoparticles can enhance photodynamic therapy (PDT) by generating more singlet oxygen (¹O₂). After successfully coated RBC membranes onto nanoparticles, the novel oxygen self-enriched biomimetic RBCs remained the characteristics of photothermal therapy (PTT) and enhanced PDT in vitro. Importantly, it can effectively reduce immune clearance in macrophage cells (RAW264.7) and significantly prolong blood circulation time, achieving high accumulation in tumor. In addition, the tumor growth was effectively inhibited after intravenous injection to tumor-bearing mice. Altogether, this oxygen self-enriched RBCs with long circulation time and high oxygen capacity as natural RBCs provide a new strategy to design biomimetic nano-system for clinical cancer phototherapy treatment.

STATEMENT OF SIGNIFICANCE

Near-infrared (NIR) dyes encapsulated in nanocarriers have been achieved great interest in cancer phototherapy treatment. However, the low singlet oxygen (¹O₂) quantum of NIR dyes and short circulation time of nanoparticles lead to unsatisfactory efficacy, limiting their applications. In this study, a novel oxygen self-enriched biomimetic red blood cell (bio-RBC) was developed to produce fluorescence, imaging-guided for photothermal therapy (PTT) and enhanced photodynamic therapy (PDT). It was composed of RBC membranes and albumin nanoparticles (IPH) which contained indocyanine green (ICG) and perfluorocarbon (PFC). After RBC membranes successfully being coated on nanoparticles, bio-RBC can effectively reduce immune clearance in macrophage cells and achieve longer circulation time in vivo, due to the protein retention in RBC membranes. In addition, PFC with high oxygen capacity can provide more oxygen to generate more ¹O₂ and dissolve ¹O₂ to enhance its life-time, enhancing PDT cancer treatment. In summary, the novel bio-RBC with longer lifetime and higher oxygen capacity as natural RBCs can significantly accumulate on tumor and effectively enhance phototherapy. It could serve as a novel strategy to overcome the problems of NIR dyes encapsulated nanoparticles, promising for future clinical application.

Cancer Cell Membrane Camouflaged Cascade Bioreactor for Cancer Targeted Starvation and Photodynamic Therapy

Selectively cuting off the nutrient supply and the metabolism pathways of cancer cells would be a promising approach to improve the efficiency of cancer treatment. Here, a cancer targeted cascade bioreactor (designated as mCGP) was constructed for synergistic starvation and photodynamic therapy (PDT) by embedding glucose oxidase (GOx) and catalase in the cancer cell membrane-camouflaged porphyrin metal-organic framework (MOF) of PCN-224 (PCN stands for porous coordination network). Due to biomimetic surface functionalization, the immune escape and homotypic targeting behaviors of mCGP would dramatically enhance its cancer targeting and retention abilities. Once internalized by cancer cells, mCGP was found to promote microenvironmental oxygenation by catalyzing the endogenous hydrogen peroxide (H₂O₂) to produce oxygen (O₂), which would subsequently accelerate the decomposition of intracellular glucose and enhance the production of cytotoxic singlet oxygen (¹O₂) under light irradiation. Consequently, mCGP displayed amplified synergistic therapeutic effects of long-term cancer starvation therapy and robust PDT, which would efficiently inhibit the cancer growth after a single administration. This cascade bioreactor would further facilitate the development of complementary modes for spatiotemporally controlled cancer treatment.

Receptor and Microenvironment Dual-Recognizable Nanogel for Targeted Chemotherapy of Highly Metastatic Malignancy

Targeted delivery of chemotherapeutic drugs to the desired lesion sites is the main objective in malignancy treatment, especially in highly metastatic malignancies. However, extensive studies around the world on traditional targeting strategies of recognizing either overexpressed receptors or microenvironments in tumors show great limitations, owing to the off-target effect and tumor homogeneity. Integration of both receptor-mediated targeting (RMT) and environment-mediated targeting (EMT) enhances the tumor accumulation and subsequent cell uptake at the same time, which may avoid these limitations. Herein, a dual targeting nanogel of PMNG engineered with both phenylboronic acid (PBA) and morpholine (MP) was reported for not only RMT via specific recognition of sialyl (SA) epitopes but also EMT toward extracellular acidity. Further engineering the nanoparticles via loading doxorubicin (DOX) brought a novel dual targeting system, that is, PMNG/DOX. PMNG/DOX demonstrated a greater targeting effect to both primary and metastatic B16F10 melanoma than the single PBA-modified nanogel (PNG) with only RMT in vitro and in vivo. Moreover, PMNG/DOX was also proved to be highly potent on inhibiting primary tumor growth as well as tumor metastasis on B16F10 melanoma-grafted mouse model. The results demonstrated the dual targeting design as a translational approach for drug delivery to highly metastatic tumor.

Preparation and Application of Cell Membrane-Camouflaged Nanoparticles for Cancer Therapy

Cancer is one of the leading causes of death worldwide. Many treatments have been developed so far, although effective, suffer from severe side effects due to low selectivity. Nanoparticles can improve the therapeutic index of their delivered drugs by specifically transporting them to tumors. However, their exogenous nature usually leads to fast clearance by mononuclear phagocytic system. Recently, cell membrane-camouflaged nanoparticles have been investigated for cancer therapy, taking advantages of excellent biocompatibility and versatile functionality of cell membranes. In this review, we summarized source materials and procedures that have been used for constructing and characterizing biomimetic nanoparticles with a focus on their application in cancer therapy.

Nanoparticle design strategies for enhanced anticancer therapy by exploiting the tumour microenvironment

Nanovehicles can efficiently carry and deliver anticancer agents to tumour sites. Compared with normal tissue, the tumour microenvironment has some unique properties, such as vascular abnormalities, hypoxia and acidic pH. There are many types of cells, including tumour cells, macrophages, immune and fibroblast cells, fed by defective blood vessels in the solid tumour. Exploiting the tumour microenvironment can benefit the design of nanoparticles for enhanced therapeutic effectiveness. In this review article, we summarized the recent progress in various nanoformulations for cancer therapy, with a special emphasis on tumour microenvironment stimuli-responsive ones. Numerous tumour microenvironment modulation strategies with promising cancer therapeutic efficacy have also been highlighted. Future challenges and opportunities of design consideration are also discussed in detail. We believe that these tumour microenvironment modulation strategies offer a good chance for the practical translation of nanoparticle formulas into clinic.

Cell membrane-derived nanomaterials for biomedical applications

The continued evolution of biomedical nanotechnology has enabled clinicians to better detect, prevent, manage, and treat human disease. In order to further push the limits of nanoparticle performance and functionality, there has recently been a paradigm shift towards biomimetic design strategies. By taking inspiration from nature, the goal is to create next-generation nanoparticle platforms that can more effectively navigate and interact with the incredibly complex biological systems that exist within the body. Of great interest are cellular membranes, which play essential roles in biointerfacing, self-identification, signal transduction, and compartmentalization. In this review, we explore the major ways in which researchers have directly leveraged cell membrane-derived biomaterials for the fabrication of novel nanotherapeutics and nanodiagnostics. Such emerging technologies have the potential to significantly advance the field of nanomedicine, helping to improve upon traditional modalities while also enabling novel applications.

Dipole Orientation Matters: Longer-Circulating Choline Phosphate than Phosphocholine Liposomes for Enhanced Tumor Targeting

Zwitterionic phosphocholine (PC) liposomes are widely used in drug delivery because of their high biocompatibility and long blood circulation time. We herein report that by flipping the direction of the PC dipole, the resulting choline phosphate (CPe) liposomes have an even longer circulation time, as confirmed at both cellular and animal-model levels. Even when 33% cholesterol was included in the lipid formulation with a poly(ethylene glycol) layer, the CPe liposome still had a longer blood circulation time. Isothermal titration calorimetry indicates a lack of protein adsorption or PC membrane attachment for the CPe liposomes. This is different from the previously reported adhesion of CP polymers to PC lipid membranes, which may be attributed to the different ways of displaying the CP headgroup. With a longer blood circulation time, the CPe liposomes accumulated in tumors more easily than PC liposomes, which is likely due to the enhanced permeation and retention effect and tumor cell uptake. This study provides key insights into zwitterionic biointerfaces for biomedical, analytical, and materials applications.

Smart Asymmetric Vesicles with Triggered Availability of Inner Cell-Penetrating Shells for Specific Intracellular Drug Delivery

Smart nanocarriers attract considerable interest in the filed of precision nanomedicine. Dynamic control of the interaction between nanocarriers and cells offers the feasibility that in situ activates cellular internalization at the targeting sites. Herein, we demonstrate a novel class of enzyme-responsive asymmetric polymeric vesicles self-assembled from matrix metalloproteinase (MMP)-cleavable peptide-linked triblock copolymer, poly(ethylene glycol)-GPLGVRG-b-poly(ε-caprolactone)-b-poly(3-guanidinopropyl methacrylamide) (PEG-GPLGVRG-PCL-PGPMA), in which the cell-penetrating PGPMA segments asymmetrically distribute in the outer and inner shells with fractions of 9% and 91%, respectively. Upon treatment with MMP-2 to cleave the stealthy PEG shell, the vesicles undergo morphological transformation into fused multicavity vesicles and small nanoparticles, accompanied by redistribution of PGPMA segments with 76% exposed to the outside. The vesicles after dePEGylation show significantly increased cellular internalization efficiency (∼10 times) as compared to the original ones due to the triggered availability of cell-penetrating shells. The vesicles loading hydrophobic anticancer drug paclitaxel (PTX) in the membrane exhibit significantly enhanced cytotoxicity against MMP-overexpressing HT1080 cells and multicellular spheroids. The proposed vesicular system can serve as a smart nanoplatform for in situ activating intracellular drug delivery in MMP-enriched tumors.

Erythrocyte membrane nanoparticles improve the intestinal absorption of paclitaxel

Paclitaxel (PTX) is a cytotoxic chemotherapy drug with encouraging activity in human malignancies. However, free PTX has a very low oral bioavailability due to its low aqueous solubility and the gastrointestinal drug barrier. In order to overcome this obstacle, we have designed erythrocyte membrane nanoparticles (EMNP) using sonication method. The permeability of PTX by EMNP was 3.5-fold (P_app = 0.425 nm/s) and 16.2-fold (P_app = 394.1 nm/s) higher than free PTX in MDCK-MDR1 cell monolayers and intestinal mucosal tissue, respectively. The in vivo pharmacokinetics indicated that the AUC_0-t (μg/mL·h) and C_max (μg/mL) of EMNP were 14.2-fold and 6.0-fold higher than that of free PTX, respectively. In summary, the EMNP appears to be a promising nanoformulation to enhance the oral bioavailability of insoluble and poorly permeable drugs.

Microfluidic Electroporation-Facilitated Synthesis of Erythrocyte Membrane-Coated Magnetic Nanoparticles for Enhanced Imaging-Guided Cancer Therapy

Biomimetic cell membrane-coated nanoparticles (CM-NPs) with superior biochemical properties have been broadly utilized for various biomedical applications. Currently, researchers primarily focus on using ultrasonic treatment and mechanical extrusion to improve the synthesis of CM-NPs. In this work, we demonstrate that microfluidic electroporation can effectively facilitate the synthesis of CM-NPs. To test it, Fe₃O₄ magnetic nanoparticles (MNs) and red blood cell membrane-derived vesicles (RBC-vesicles) are infused into a microfluidic device. When the mixture of MNs and RBC-vesicles flow through the electroporation zone, the electric pulses can effectively promote the entry of MNs into RBC-vesicles. After that, the resulting RBC membrane-capped MNs (RBC-MNs) are collected from the chip and injected into experimental animals to test the in vivo performance. Owing to the superior magnetic and photothermal properties of the MN cores and the long blood circulation characteristic of the RBC membrane shells, core-shell RBC-MNs were used for enhanced tumor magnetic resonance imaging (MRI) and photothermal therapy (PTT). Due to the completer cell membrane coating, RBC-MNs prepared by microfluidic electroporation strategy exhibit significantly better treatment effect than the one fabricated by conventional extrusion. We believe the combination of microfluidic electroporation and CM-NPs provides an insight into the synthesis of bioinpired nanoparticles to improve cancer diagnosis and therapy.

Erythrocyte-Platelet Hybrid Membrane Coating for Enhanced Nanoparticle Functionalization

Cell-membrane-coated nanoparticles have recently been studied extensively for their biological compatibility, retention of cellular properties, and adaptability to a variety of therapeutic and imaging applications. This class of nanoparticles, which has been fabricated with a variety of cell membrane coatings, including those derived from red blood cells (RBCs), platelets, white blood cells, cancer cells, and bacteria, exhibit properties that are characteristic of the source cell. In this study, a new type of biological coating is created by fusing membrane material from two different cells, providing a facile method for further enhancing nanoparticle functionality. As a proof of concept, the development of dual-membrane-coated nanoparticles from the fused RBC membrane and platelet membrane is demonstrated. The resulting particles, termed RBC-platelet hybrid membrane-coated nanoparticles ([RBC-P]NPs), are thoroughly characterized, and it is shown that they carry properties of both source cells. Further, the [RBC-P]NP platform exhibits long circulation and suitability for further in vivo exploration. The reported strategy opens the door for the creation of biocompatible, custom-tailored biomimetic nanoparticles with varying hybrid functionalities, which may be used to overcome the limitations of current nanoparticle-based therapeutic and imaging platforms.

Insight into the interactions between nanoparticles and cells

This review summarizes the latest advances in nanoparticle (NP)–cell interactions. The influence of NP size, shape, shell structure, surface chemistry and protein corona formation on cellular uptake and cytotoxicity is highlighted in detail. Their impact on other cellular responses such as cell proliferation, differentiation and cellular mechanics is also discussed.

Erythrocyte membrane based cationic polymer-mcDNA complexes as an efficient gene delivery system

An erythrocyte membrane based gene delivery system presents high transfection efficiency and negligible cytotoxicity.

Stem-Cell-Membrane Camouflaging on Near-Infrared Photoactivated Upconversion Nanoarchitectures for in Vivo Remote-Controlled Photodynamic Therapy

The upconversion nanoparticle (UCNP)-based photodynamic therapy (PDT) agents are promising for deep-tissue cancer treatment because they may overcome current limitations due to the shallow penetration depth of visible light. However, limited blood circulation time and poor tumor-targeting capability challenge the therapeutic efficacy of UCNP-based PDT in vivo. Here, we demonstrate intravenous injectable stem-cell-membrane-camouflaged upconversion nanoarchitectures as a biomimetic tumor PDT platform. The biomimetic PDT system is constructed by fusing mesoporous-silica-encapsulated β-NaYF4:Yb³⁺,Er³⁺ UCNPs with stem-cell membranes. Translocation of the stem-cell membranes to the UCNPs led to the translation of multiple membrane components, bringing the membranes' long circulation and tumor-targeting capability to the resulting platform. Multiphotosensitizers were encapsulated and simultaneously activated by a 980 nm single laser because of the multicolor emission capability of the UCNP cores. In vitro and in vivo experiments demonstrate that this novel platform inherits the tumor-targeting properties of stem cells and exhibits remarkable accumulation at the tumor site. In vivo tumor PDT results show higher tumor inhibition efficacy by tail intravenous administration of this new photosensitizer-loaded system. This stem-cell-membrane-camouflaged upconversion nanoarchitecture provides artificial UCNPs with natural cell membranes and holds considerable promise for deep-tissue PDT cancer treatment by systemic administration.

Biointerfacing and Applications of Cell Membrane-Coated Nanoparticles

The cell membrane-coated nanoparticle is a biomimetic platform consisting of a nanoparticulate core coated with membrane derived from a cell, such as a red blood cell, platelet, or cancer cell. The cell membrane "disguise" allows the particles to be perceived by the body as the source cell by interacting with its surroundings using the translocated surface membrane components. The newly bestowed characteristics of the membrane-coated nanoparticle can be utilized for biological interfacing in the body, providing natural solutions to many biomedical issues. This Review will cover the interactions of these cell membrane-coated nanoparticles and their applications within three biomedical areas of interest, including (i) drug delivery, (ii) detoxification, and (iii) immune modulation.

Cancer-Cell-Biomimetic Nanoparticles for Targeted Therapy of Homotypic Tumors

A unique biomimetic drug-delivery system composed of 4T1-breast-cancer-cell membranes and paclitaxel-loaded polymeric nanoparticles (PPNs) (cell-membrane-coated PPNs), demonstrates superior interactions to its source tumor cells and elongated blood circulation, and displays highly cell-specific targeting of the homotypic primary tumor and metastases, with successful inhibition of the growth and lung metastasis of the breast cancer cells.

Upper Critical Solution Temperature Polymer, Photothermal Agent, and Erythrocyte Membrane Coating: An Unexplored Recipe for Making Drug Carriers with Spatiotemporally Controlled Cargo Release

"On-demand" drug release within target site is critical for targeted drug delivery systems. We herein integrate the advantages of upper critical solution temperature (UCST) polymers, photothermal agent, and red blood cell (RBC) membrane coating into a single drug delivery nanosystem and, for the first time, achieve remotely controlled UCST polymer-based drug delivery system that undergoes "on-demand" drug release within specified zone. When in laser-off state, the resulting nanosystem demonstrates significantly diminished drug self-leakage, owing to shielding by the RBC membrane coating. Upon laser irradiation, this system undergoes responsive drug release, likely because of particle swelling due to its UCST polymer component's hydrophobic-to-hydrophilic transition triggered by the rapid localized heating generated by its preloaded photothermal agent via photothermal effects. As a result, this drug delivery system exhibits spatiotemporally controlled cytotoxicity to cultured cells, efficiently eradicating irradiated cancerous cells without appreciably impacting nonirradiated ones, those ∼0.7 cm away from the irradiation zone. This work may open an avenue to thermosensitive drug delivery systems potentially "ideal" for intravenous administration and inspire future efforts on biomedical applications of UCST polymers.

Liposomes Coated with Isolated Macrophage Membrane Can Target Lung Metastasis of Breast Cancer

Cancer metastasis leads to high mortality of breast cancer and is difficult to treat because of the poor delivery efficiency of drugs. Herein, we report the wrapping of a drug-carrying liposome with an isolated macrophage membrane to improve delivery to metastatic sites. The macrophage membrane decoration increased cellular uptake of the emtansine liposome in metastatic 4T1 breast cancer cells and had inhibitory effects on cell viability. In vivo, the macrophage membrane enabled the liposome to target metastatic cells and produced a notable inhibitory effect on lung metastasis of breast cancer. Our results provide a biomimetic strategy via the biological properties of macrophages to enhance the medical performance of a nanoparticle in vivo for treating cancer metastasis.

Coating nanoparticles with cell membranes for targeted drug delivery

Targeted delivery allows drug molecules to preferentially accumulate at the sites of action and thus holds great promise to improve therapeutic index. Among various drug-targeting approaches, nanoparticle-based delivery systems offer some unique strengths and have achieved exciting preclinical and clinical results. Herein, we aim to provide a review on the recent development of cell membrane-coated nanoparticle system, a new class of biomimetic nanoparticles that combine both the functionalities of cellular membranes and the engineering flexibility of synthetic nanomaterials for effective drug delivery and novel therapeutics. This review is particularly focused on novel designs of cell membrane-coated nanoparticles as well as their underlying principles that facilitate the purpose of drug targeting. Three specific areas are highlighted, including: (i) cell membrane coating to prolong nanoparticle circulation, (ii) cell membrane coating to achieve cell-specific targeting and (iii) cell membrane coating for immune system targeting. Overall, cell membrane-coated nanoparticles have emerged as a novel class of targeted nanotherapeutics with strong potentials to improve on drug delivery and therapeutic efficacy for treatment of various diseases.

The use of CD47-modified biomaterials to mitigate the immune response

Addressing the aberrant interactions between immune cells and biomaterials represents an unmet need in biomaterial research. Although progress has been made in the development of bioinert coatings, identifying and targeting relevant cellular and molecular pathways can provide additional therapeutic strategies to address this major healthcare concern. To that end, we describe the immune inhibitory motif, receptor-ligand pairing of signal regulatory protein alpha and its cognate ligand CD47 as a potential signaling pathway to enhance biocompatibility. The goals of this article are to detail the known roles of CD47-signal regulatory protein alpha signal transduction pathway and to describe how immobilized CD47 can be used to mitigate the immune response to biomaterials. Current applications of CD47-modified biomaterials will also be discussed herein.

Cancer Cell Membrane-Coated Upconversion Nanoprobes for Highly Specific Tumor Imaging

Cancer cell membrane-coated upconversion nanoprobes (CC-UCNPs) with immune escape and homologous targeting capabilities are used for highly specific tumor imaging. The combination of UCNPs with biomimetic cancer cell membranes embodies a novel materials design strategy and presents a compelling class of advanced materials.

Safe and Immunocompatible Nanocarriers Cloaked in RBC Membranes for Drug Delivery to Treat Solid Tumors

The therapeutic potential of nanoparticle-based drug carriers depends largely on their ability to evade the host immune system while delivering their cargo safely to the site of action. Of particular interest are simple strategies for the functionalization of nanoparticle surfaces that are both inherently safe and can also bestow immunoevasive properties, allowing for extended blood circulation times. Here, we evaluated a recently reported cell membrane-coated nanoparticle platform as a drug delivery vehicle for the treatment of a murine model of lymphoma. These biomimetic nanoparticles, consisting of a biodegradable polymeric material cloaked with natural red blood cell membrane, were shown to efficiently deliver a model chemotherapeutic, doxorubicin, to solid tumor sites for significantly increased tumor growth inhibition compared with conventional free drug treatment. Importantly, the nanoparticles also showed excellent immunocompatibility as well as an advantageous safety profile compared with the free drug, making them attractive for potential translation. This study demonstrates the promise of using a biomembrane-coating approach as the basis for the design of functional, safe, and immunocompatible nanocarriers for cancer drug delivery.

Macrophage Cell Membrane Camouflaged Au Nanoshells for in Vivo Prolonged Circulation Life and Enhanced Cancer Photothermal Therapy

Macrophage cell membrane (MPCM)-camouflaged gold nanoshells (AuNS) that can serve as a new generation of photothermal conversion agents for in vivo photothermal cancer therapy are presented. They are constructed by the fusion of biocompatible AuNSs and MPCM vesicles. The resulting MPCM-coated AuNSs exhibited good colloidal stability and kept the original near-infrared (NIR) adsorption of AuNSs. Because AuNS carried high-density coverage of MPCMs, the totally functional portions of macrophage cells membrane were grafted onto the surface of AuNSs. This surface functionalization provided active targeting ability by recognizing tumor endothelium and thus improved tumoritropic accumulation compared to the red blood cell membrane-coating approach. These biomimetic nanoparticles significantly enhance in vivo blood circulation time and local accumulation at the tumor when administered systematically. Upon NIR laser irradiation, local heat generated by the MPCM-coated AuNS achieves high efficiency to suppress tumor growth and selectively ablate cancerous cells within the illuminated zone. Therefore, MPCM-coated AuNSs remained the natural properties of their source cells, which may improve the efficacy of photothermal therapy modulated by AuNSs and other noble-metal nanoparticles.

Erythrocytes in nanomedicine: an optimal blend of natural and synthetic materials

A hybrid approach strategy using synthetic nanoparticles and erythrocytes offers an optimal blend of natural and synthetic materials. The combined advantages of erythrocytes and nanoparticles could serve as an immune-evasive multifunctional platform. This review summarized the research on state-of-the-art and significant advances in erythrocytes for nanomedicine, and presented are their fabrication process, their unique properties and applications. According to its structure, this review mainly focuses on three kinds of erythrocyte-based nanomedicine: whole erythrocytes as carriers, cell membrane coated nanoparticles, and nanoerythrosomes. In addition, some future prospects are also prudentially addressed. We expect rapid success in the advancement of erythrocyte-based nanomedicines, from the bench to the bedside.

Leucocyte Membrane-Coated Janus Microcapsules for Enhanced Photothermal Cancer Treatment

Polyelectrolyte multilayer (PEM) capsules are promising candidates for many kinds of cancer detection and treatment but are usually intended to deliver cargo to specific sites or to destroy cancer cells based on photothermal effects from the outside. In this publication we prove that it is possible to kill cancer cells from the inside based on phagocytosed PEM capsules. In addition we show how to open the cells and bring the PEM capsules to the surface of cancer cells based on photothermal effects and rapid evaporation of water. Diffusion-based temperature determinations of the photothermal effect up to the evaporation temperature of water are presented.

Monocyte cell membrane-derived nanoghosts for targeted cancer therapy

Core-shell type 'nanoghosts' were synthesized with a drug-loaded biodegradable PLGA core and a monocyte cell membrane-derived shell. The nanoghosts were monodisperse with an average size <200 nm, and showed good serum stability for 120 h. Doxorubicin-loaded nanoghosts showed greater cellular uptake and cytotoxicity compared to non-coated nanoparticle controls in metastatic MCF-7 breast cancer cell lines.

Red blood cell membrane camouflaged magnetic nanoclusters for imaging-guided photothermal therapy

Along with intrinsic magnetic resonance imaging (MRI) advantages, iron oxide nanomaterials capable of photothermal conversion have been reported very recently and have again raised great interest in their designs among biomedical researchers. However, like other inorganic nanomaterials, high macrophage uptake, short blood retention time and unfavorable biodistributions have strongly hampered their applications in vivo. To solve these problems, a rational design of red blood cell (RBC) membrane camouflaged iron oxide magnetic clusters (MNC@RBCs) is presented in this paper. Our data show that by simply introducing an "ultra-stealth" biomimetic coating to iron oxide magnetic nanoclusters (MNCs), MNC@RBCs maintain the imaging and photothermal functionalities inherited from MNCs cores while achieving much lower nonspecific macrophage uptake and dramatically altered fate in vivo. MNC@RBCs with superior prolonged blood retention time, preferred high tumor accumulation and relatively lowered liver biodistribution are demonstrated when injected intravenously in mice, leading to greatly enhanced photothermal therapeutic efficacy by a single treatment without further magnetic force manipulation. Our study illustrates a well prepared integration of MNCs and RBCs, exploiting advantages of both functionalities within a single unit and suggests a promising future for iron-based nanomaterials application in vivo.

Synthetic nanoparticles camouflaged with biomimetic erythrocyte membranes for reduced reticuloendothelial system uptake

Suppression of the reticuloendothelial system (RES) uptake is one of the most challenging tasks in nanomedicine. Coating stratagems using polymers, such as poly(ethylene glycol) (PEG), have led to great success in this respect. Nevertheless, recent observations of immunological response toward these synthetic polymers have triggered a search for better alternatives. In this work, natural red blood cell (RBC) membranes are camouflaged on the surface of Fe3O4 nanoparticles for reducing the RES uptake. In vitro macrophage uptake, in vivo biodistribution and pharmacokinetic studies demonstrate that the RBC membrane is a superior alternative to the current gold standard PEG for nanoparticle 'stealth'. Furthermore, we systematically investigate the in vivo potential toxicity of RBC membrane-coated nanoparticles by blood biochemistry, whole blood panel examination and histology analysis based on animal models. The combination of synthetic nanoparticles and natural cell membranes embodies a novel and biomimetic nanomaterial design strategy and presents a compelling property of functional materials for a broad range of biomedical applications.

How Leucocyte Cell Membrane Modified Janus Microcapsules are Phagocytosed by Cancer Cells

Modern drug delivery systems rely on either antibody-based single-surface recognition or on surface-hydrophobicity-based approaches. For a tumor showing various surface mutations, both approaches fail. This publication hereby presents Janus capsules based on polyelectrolyte multilayer microcapsules exhibiting human leucocyte (THP-1 cell line) cell membranes for discriminating HUVEC cells from three different cancer cell lines. Despite destroying the cellular integrity of leucocyte cells, the modified Janus capsules are able to adhere to cancer cells. Leucocyte cell-membrane-coated Janus capsules are phagocytosed with the cellular membrane part pointing to the cells.

Emerging nanomedicine approaches fighting tumor metastasis: animal models, metastasis-targeted drug delivery, phototherapy, and immunotherapy

Nanomedicine approaches may bring new opportunities for tumor metastasis treatment.

Anti-phagocytosis and tumor cell targeting micelles prepared from multifunctional cell membrane mimetic polymers

“Stealthy bio-missile” kinds of micelles were fabricated for developing advanced anticancer formulations by cell membrane mimicking.

Cell membrane-camouflaged nanoparticles for drug delivery

Nanoparticles can preferentially accumulate at sites of action and hold great promise to improve the therapeutic index of many drugs. While conventional methods of nanocarrier-mediated drug delivery have focused on primarily synthetic approaches, engineering strategies that combine synthetic nanoparticles with natural biomaterials have recently gained much attention. In particular, cell membrane-camouflaged nanoparticles are a new class of biomimetic nanoparticles that combine the unique functionalities of cellular membranes and engineering versatility of synthetic nanomaterials for effective delivery of therapeutic agents. Herein, we report on the recent progress on cell membrane-coated nanoparticles for drug delivery. In particular, we highlight three areas: (i) prolonging systemic circulation via cell membrane coating, (ii) cell-specific targeting via cell membrane coating, and (iii) applications of cell membrane coating for drug delivery. The cell membrane-camouflaged nanoparticle platform has emerged as a novel delivery strategy with the potential to improve the therapeutic efficacy for the treatment of a variety of diseases.

Red Blood Cell Membrane as a Biomimetic Nanocoating for Prolonged Circulation Time and Reduced Accelerated Blood Clearance

For decades, poly(ethylene glycol) (PEG) has been widely incorporated into nanoparticles for evading immune clearance and improving the systematic circulation time. However, recent studies have reported a phenomenon known as "accelerated blood clearance (ABC)" where a second dose of PEGylated nanomaterials is rapidly cleared when given several days after the first dose. Herein, we demonstrate that natural red blood cell (RBC) membrane is a superior alternative to PEG. Biomimetic RBC membrane-coated Fe(3)O(4) nanoparticles (Fe(3)O(4) @RBC NPs) rely on CD47, which is a "don't eat me" marker on the RBC surface, to escape immune clearance through interactions with the signal regulatory protein-alpha (SIRP-α) receptor. Fe(3)O(4) @RBC NPs exhibit extended circulation time and show little change between the first and second doses, with no ABC suffered. In addition, the administration of Fe(3)O(4) @RBC NPs does not elicit immune responses on neither the cellular level (myeloid-derived suppressor cells (MDSCs)) nor the humoral level (immunoglobulin M and G (IgM and IgG)). Finally, the in vivo toxicity of these cell membrane-camouflaged nanoparticles is systematically investigated by blood biochemistry, hematology testing, and histology analysis. These findings are significant advancements toward solving the long-existing clinical challenges of developing biomaterials that are able to resist both immune response and rapid clearance.

Cell Membrane-Coated Nanoparticles As an Emerging Antibacterial Vaccine Platform

Nanoparticles have demonstrated unique advantages in enhancing immunotherapy potency and have drawn increasing interest in developing safe and effective vaccine formulations. Recent technological advancement has led to the discovery and development of cell membrane-coated nanoparticles, which combine the rich functionalities of cellular membranes and the engineering flexibility of synthetic nanomaterials. This new class of biomimetic nanoparticles has inspired novel vaccine design strategies with strong potential for modulating antibacterial immunity. This article will review recent progress on using cell membrane-coated nanoparticles for antibacterial vaccination. Specifically, two major development strategies will be discussed, namely (i) vaccination against virulence factors through bacterial toxin sequestration; and (ii) vaccination against pathogens through mimicking bacterial antigen presentation.

Synthesis of Nanogels via Cell Membrane-Templated Polymerization

The synthesis of biomimetic hydrogel nanoparticles coated with a natural cell membrane is described. Compared to the existing strategy of wrapping cell membranes onto pre-formed nanoparticle substrates, this new approach forms the cell membrane-derived vesicles first, followed by growing nanoparticle cores in situ. It adds significant controllability over the nanoparticle properties and opens unique opportunities for a broad range of biomedical applications.

Biomimetic Acoustically-Responsive Vesicles for Theranostic Applications

In recent years, biomimetic cell membrane-derived particles have emerged as a new class of drug delivery system with advantages of biocompatibility, ease of isolation and long circulation profile. Here we report the development and potential theranostic applications of a new biomimetic acoustically-responsive droplet system derived from mammalian red blood cell membrane (RBCM). We hypothesized that drug-loaded RBCM droplets (RBCMDs) would undergo a transition from liquid (droplets) to gas (bubbles) upon high intensity focused ultrasound (HIFU) insonation, resulting in on-demand drug release. The generated microbubbles could also serve as a contrast agent to enhance ultrasound imaging. As-synthesized RBCMDs exhibited uniform size, good dispersity and preservation of RBCM-associated proteins that prevented uptake by macrophages. Camptothecin (CPT), an anti-cancer drug, was successfully loaded in the RBCMDs with a loading efficiency of 2-3% and an encapsulation efficiency of 62-97%. A short (3 min) exposure to HIFU irradiation triggered release of CPT from the RBCMDs and the physical explosion of droplets damaged nearby cancer cells resulting in significant cell death. In addition, the acoustically vaporized RBCMDs significantly increased the ultrasound echo signal to 30 dB. Lastly, we demonstrated that RBCMDs could be acoustically vaporized in vivo in target tissues, and enhancing ultrasound imaging. Taken together, we have developed a new class of naturally derived RBCMDs which show great potential for future application in remotely triggered drug delivery and ultrasound imaging enhancement.

Macrophage Cell Membrane Camouflaged Mesoporous Silica Nanocapsules for In Vivo Cancer Therapy

Engineering natural macrophage cell membrane-camouflaged mesoporous silica nanocapsules can reduce the arrested percentage of immune cells and tissues, effectively prolong the survival time of nanoparticles in blood circulation system, and improve the accumulation in tumor.

Blended nanoparticle system based on miscible structurally similar polymers: a safe, simple, targeted, and surprisingly high efficiency vehicle for cancer therapy

A novel blended nanoparticle (NP) system for the delivery of anticancer drugs and its surprisingly high efficacy for cancer chemotherapy by blending a targeting polymer folic acid-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (FA-PEG-b-PLGA) and a miscible structurally similar polymer D-α-tocopheryl polyethylene glycol 1000 succinate-poly(lactide-co-glycolide) (TPGS-PLGA) is reported. This blended NP system can be achieved through a simple and effective nanoprecipitation technique, and possesses unique properties: i) improved long-term compatibility brought by PEG-based polymers; ii) reduced multidrug resistance mediated by P-glycoprotein (P-gp) in tumor cells and increased bioavailability of anticancer drugs by incorporation of TPGS; iii) the regulation of controlled release through polymer ratios and active targeting by FA. Both in vitro cell experiments and in vivo antitumor assays demonstrated the reported blended NP system can achieve the best therapeutic efficiency in an extremely safe, simple and highly efficient process for cancer therapy. Moreover, this NP system is highly efficient in forming NPs with multiple functions, without repeated chemical modification of polymers, which is sometimes complex, inefficient and high cost. Therefore, the development of this novel blended NP concept is extremely meaningful for the application of pharmaceutical nanotechnology in recent studies.

Inherently stealthy and highly tumor-selective gold nanoraspberries for photothermal cancer therapy

Owing to their unique optical properties such as large absorption and scattering cross section and large enhancement of electromagnetic field at the surface, plasmonic nanostructures have received extensive attention as a highly promising class of materials for nano-oncology. Most of the existing plasmonic nanostructures require extensive post-synthesis treatments and biofunctionalization routines to mitigate their cytotoxicity and/or make them tumor-specific. Here, we report one-pot synthesis of a novel class of plasmonic nanostructures, namely, gold nanoraspberries (GRBs) with tunable size and localized surface plasmon resonance by using a naturally abundant polysaccharide, chitosan, which acts as a template and capping agent. Significantly, the GRBs, which do not require any further biofunctionalization, exhibit excellent selectivity to tumor cells, thus enabling locoregional therapy at the cellular level. We demonstrate the tumor-selectivity of GRBs by photothermal ablation of tumor cells selectively from their co-culture with normal cells. The simple, scalable and tumor-selective nature of GRBs makes them excellent candidates for translational plasmonics-based nanomedicine.