Cell Membrane Coating Nanotechnology

Biomimetic Micromotor Enables Active Delivery of Antigens for Oral Vaccination

Vaccination represents one of the most effective means of preventing infectious disease. In order to maximize the utility of vaccines, highly potent formulations that are easy to administer and promote high patient compliance are desired. In the present work, a biomimetic self-propelling micromotor formulation is developed for use as an oral antivirulence vaccine. The propulsion is provided by a magnesium-based core, and a biomimetic cell membrane coating is used to detain and neutralize a toxic antigenic payload. The resulting motor toxoids leverage their propulsion properties in order to more effectively elicit mucosal immune responses. After demonstrating the successful fabrication of the motor toxoids, their uptake properties are shown in vitro. When delivered to mice via an oral route, it is then confirmed that the propulsion greatly improves retention and uptake of the antigenic material in the small intestine in vivo. Ultimately, this translates into markedly elevated generation of antibody titers against a model toxin. This work provides a proof-of-concept highlighting the benefits of active oral delivery for vaccine development, opening the door for a new set of applications, in which biomimetic motor technology can provide significant benefits.

Coordination Nanosheets of Phthalocyanine as Multifunctional Platform for Imaging-Guided Synergistic Therapy of Cancer

"All-in-one" nanodrugs integrating various functionalities into one nanosystem are highly desired for cancer treatment. Coordination nanosheets as one type of two dimensional (2D) nanomaterials offer great opportunities, but there is lack of enough candidates. Here, a new kind of coordination nanosheets based on phthalocyanine are constructed. Manganese phthalocyanine (MnPc) tetracarboxylic acid is employed as photoactive ligand to form MnPc nanosheets; meanwhile, hyaluronic acid (HA) is coated on their surface. The obtained MnPc@HA nanosheets exhibit superior near-infrared (NIR) photothermal effect with photothermal conversion efficiency of 72.3%, much higher than those of the previously reported photothermal agents. Due to their 2D nanostructures, MnPc@HA nanosheets possess superhigh drug-loading capacity for chemotherapy drug curcumin. With HA as a targeting group, the nanosheets selectively accumulated in CD44 overexpressed tumors, followed by drug release under the control of NIR light. Moreover, MnPc@HA nanosheets with intrinsic paramagnetism can serve as T₁ contrast agent for magnetic resonance imaging. The synergistic effect of phototherapy and chemotherapy endows curcumin-loaded MnPc@HA nanosheets with superior tumor-eradicating efficacy. Besides, MnPc@HA nanosheets are biocompatible and safe for biomedical applications. This work provides novel insight for developing new multifunctional platforms based on 2D coordination nanosheets to synergistically combat cancer.

Biomimetic Nanosponges Suppress In Vivo Lethality Induced by the Whole Secreted Proteins of Pathogenic Bacteria

Polymeric nanoparticles coated with membrane of intact red blood cells have emerged as biomimetic toxin nanosponges (RBC-NS) that absorb and neutralize bacterial virulence factors associated with numerous bacterial infections. Despite its promise, a clear correlation between in vitro neutralization of complex bacterial toxins and in vivo therapeutic efficacy remains elusive. In this study, the whole secreted proteins (wSP) of methicillin-resistant Staphylococcus aureus (MRSA) are collected to induce lethality in mice. The wSP preserve the complexity of bacterial virulence profile while avoiding the intricacy and dynamics of infections by live bacteria. RBC-NS are first quantified for their neutralization capacity against the hemolytic activity of MRSA wSP in vitro. Using a mouse model, in vivo studies further demonstrate that, by neutralizing the hemolytic activity, RBC-NS confer significant survival benefits against wSP-induced lethality. Furthermore, when mice are challenged with a sublethal dosage of MRSA supernatant, RBC-NS reduce lung damages and inhibit the activation of nuclear factor kappa B in the spleen. These results provide a systematic evaluation of RBC-NS toward the treatment of severe MRSA infections such as MRSA bacteremia and MRSA-induced sepsis.

Phototheranostics: Active Targeting of Orthotopic Glioma Using Biomimetic Proteolipid Nanoparticles

Advances in phototheranostics revolutionized glioma intraoperative fluorescence imaging and phototherapy. However, the lack of desired active targeting agents for crossing the blood-brain barrier (BBB) significantly compromises the theranostic efficacy. In this study, biomimetic proteolipid nanoparticles (NPs) with U.S. Food and Drug Administration (FDA)-approved indocyanine green (ICG) were constructed to allow fluorescence imaging, tumor margin detection, and phototherapy of orthotopic glioma in mice. By embedding glioma cell membrane proteins into NPs, the obtained biomimetic ICG-loaded liposome (BLIPO-ICG) NPs could cross BBB and actively reach glioma at the early stage thanks to their specific binding to glioma cells due to their excellent homotypic targeting and immune escaping characteristics. High accumulation in the brain tumor with a signal to background ratio of 8.4 was obtained at 12 h post-injection. At this time point, the glioma and its margin were clearly visualized by near-infrared fluorescence imaging. Under the imaging guidance, the glioma tissue could be completely removed as a proof of concept. In addition, after NIR laser irradiation (1 W/cm², 5 min), the photothermal effect exerted by BLIPO-ICG NPs efficiently suppressed glioma cell proliferation with a 94.2% tumor growth inhibition. No photothermal damages of normal brain tissue and treatment-induced side effects were observed. These results suggest that the biomimetic proteolipid NP is a promising phototheranostic nanoplatform for brain-tumor-specific imaging and therapy.

Route to Rheumatoid Arthritis by Macrophage-Derived Microvesicle-Coated Nanoparticles

The targeted delivery of therapeutics to sites of rheumatoid arthritis (RA) has been a long-standing challenge. Inspired by the intrinsic inflammation-targeting capacity of macrophages, a macrophage-derived microvesicle (MMV)-coated nanoparticle (MNP) was developed for targeting RA. The MMV was efficiently produced through a novel method. Cytochalasin B (CB) was applied to relax the interaction between the cytoskeleton and membrane of macrophages, thus stimulating MMV secretion. The proteomic profile of the MMV was analyzed by iTRAQ (isobaric tags for relative and absolute quantitation). The MMV membrane proteins were similar to those of macrophages, indicating that the MMV could exhibit bioactivity similar to that of RA-targeting macrophages. A poly(lactic- co-glycolic acid) (PLGA) nanoparticle was subsequently coated with MMV, and the inflammation-mediated targeting capacity of the MNP was evaluated both in vitro and in vivo. The in vitro binding of MNP to inflamed HUVECs was significantly stronger than that of the red blood cell membrane-coated nanoparticle (RNP). Compared with bare NP and RNP, MNP showed a significantly enhanced targeting effect in vivo in a collagen-induced arthritis (CIA) mouse model. The targeting mechanism was subsequently revealed according to the proteomic analysis, indicating that Mac-1 and CD44 contributed to the outstanding targeting effect of the MNP. A model drug, tacrolimus, was encapsulated in MNP (T-RNP) and significantly suppressed the progression of RA in mice. The present study demonstrates MMV as a promising and rich material, with which to mimic macrophages, and demonstrates that MNP is an efficient biomimetic vehicle for RA targeting and treatment.

A biomimetic cascade nanoreactor for tumor targeted starvation therapy-amplified chemotherapy

Targeted drug delivery with precisely controlled drug release and activation is highly demanding and challenging for tumor precision therapy. Herein, a biomimetic cascade nanoreactor (designated as Mem@GOx@ZIF-8@BDOX) is constructed for tumor targeted starvation therapy-amplified chemotherapy by assembling tumor cell membrane cloak and glucose oxidase (GOx) onto zeolitic imidazolate framework (ZIF-8) with the loading prodrug of hydrogen peroxide (H₂O₂)-sensitive BDOX. Biomimetic membrane camouflage affords superior immune evasion and homotypic binding capacities, which significantly enhance the tumor preferential accumulation and uptake for targeted drug delivery. Moreover, GOx-induced glycolysis would cut off glucose supply and metabolism pathways for tumor starvation therapy with the transformation of tumor microenvironments. Importantly, this artificial adjustment could trigger the site-specific BDOX release and activation for cascade amplified tumor chemotherapy regardless of the complexity and variability of tumor physiological environments. Both in vitro and in vivo investigations indicate that the biomimetic cascade nanoreactor could remarkably improve the therapeutic efficacy with minimized side effects through the synergistic starvation therapy and chemotherapy. This biomimetic cascade strategy would contribute to developing intelligent drug delivery systems for tumor precision therapy.

Zwitterionic polypeptide nanomedicine with dual NIR/reduction-responsivity for synergistic cancer photothermal-chemotherapy

Dual NIR/reduction-responsive and zwitterionic polypeptide nanoparticles of PMC/DOX-ICG were fabricated, which achieved in vivo NIR fluorescence imaging and synergistic cancer PTT-CT treatment, and effectively ablated the HeLa tumors without recurrence for 30 days.

Recent Advances in Cell Membrane-Camouflaged Nanoparticles for Cancer Phototherapy

Phototherapy including photothermal therapy (PTT) and photodynamic therapy (PDT) employs phototherapeutic agents to generate heat or cytotoxic reactive oxygen species (ROS), and has therefore garnered particular interest for cancer therapy. However, the main challenges faced by conventional phototherapeutic agents include easy recognition by the immune system, rapid clearance from blood circulation, and low accumulation in target sites. Cell-membrane coating has emerged as a potential way to overcome these limitations, owing to the abundant proteins on the surface of cell membranes that can be inherited to the cell membrane-camouflaged nanoparticles. This review summarizes the recent advances in the development of biomimetic cell membrane-camouflaged nanoparticles for cancer phototherapy. Different sources of cell membranes can be used to coat nanoparticles uisng different coating approaches. After cell-membrane coating, the photophysical properties of the original phototherapeutic nanoparticles remain nearly unchanged; however, the coated nanoparticles are equipped with additional physiological features including immune escape, in vivo prolonged circulation time, or homologous targeting, depending on the cell sources. Moreover, the coated cell membrane can be ablated from phototherapeutic nanoparticles under laser irradiation, leading to drug release and thus synergetic therapy. By combining other supplementary agents to normalize tumor microenvironment, cell-membrane coating can further enhance the therapeutic efficacy against cancer.

Biomedical Applications of Layer-by-Layer Self-Assembly for Cell Encapsulation: Current Status and Future Perspectives

Encapsulating living cells within multilayer functional shells is a crucial extension of cellular functions and a further development of cell surface engineering. In the last decade, cell encapsulation has been widely utilized in many cutting-edge biomedical fields. Compared with other techniques for cell encapsulation, layer-by-layer (LbL) self-assembly technology, due to the versatility and tunability to fabricate diverse multilayer shells with controllable compositions and structures, is considered as a promising approach for cell encapsulation. This review summarizes the state-of-the-art and potential future biomedical applications of LbL cell encapsulation. First of all, a brief introduction to the LbL self-assembly technique, including assembly mechanisms and technologies, is made. Next, different cell encapsulation strategies by LbL self-assembly techniques are explained. Then, the biomedical applications of LbL cell encapsulation in cell-based biosensors, cell transplantation, cell/molecule delivery, and tissue engineering, are highlighted. Finally, discussions on the current limitations and future perspectives of LbL cell encapsulation are also provided.

Biomimetic Nanoparticle Vaccines for Cancer Therapy

It is currently understood that, in order for a tumor to successfully grow, it must evolve means of evading immune surveillance. In the past several decades, researchers have leveraged increases in our knowledge of tumor immunology to develop therapies capable of augmenting endogenous immunity and eliciting strong antitumor responses. In particular, the goal of anticancer vaccination is to train the immune system to properly utilize its own resources in the fight against cancer. Although attractive in principle, there are currently only limited examples of anticancer vaccines that have been successfully translated to the clinic. Recently, there has been a significant push towards the use of nanotechnology for designing vaccine candidates that exhibit enhanced potency and specificity. In this progress report, we discuss recent developments in the field of anticancer nanovaccines. By taking advantage of the flexibility offered by nanomedicine to purposefully program immune responses, this new generation of vaccines has the potential to address many of the hurdles facing traditional platforms. A specific emphasis is placed on the emergence of cell membrane-coated nanoparticles, a novel biomimetic platform that can be used to generate personalized nanovaccines that elicit strong, multi-antigenic antitumor responses.

Cell-Membrane Immunotherapy Based on Natural Killer Cell Membrane Coated Nanoparticles for the Effective Inhibition of Primary and Abscopal Tumor Growth

Developing effective immunotherapies with low toxicity and high tumor specificity is the ultimate goal in the battle against cancer. Here, we reported a cell-membrane immunotherapy strategy that was able to eliminate primary tumors and inhibited distant tumors by using natural killer (NK) cell membrane cloaked photosensitizer 4,4',4'',4'''-(porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) (TCPP)-loaded nanoparticles (NK-NPs). The proteomic profiling of NK cell membranes was performed through shotgun proteomics, and we found that NK cell membranes enabled the NK-NPs to target tumors and could induce or enhance pro-inflammatory M1-macrophages polarization to produce antitumor immunity. The TCPP loaded in NK-NPs could induce cancer cell death through photodynamic therapy and consequently enhanced the antitumor immunity efficiency of the NK cell membranes. The results confirmed that NK-NPs selectively accumulated in the tumor and were able to eliminate primary tumor growth and produce an abscopal effect to inhibit distant tumors. This cell-membrane immunotherapeutic approach offers a strategy for tumor immunotherapy.

Mesenchymal stem cell-based drug delivery strategy: from cells to biomimetic

Owing to the diversity and ease of preparation of nanomaterials, the rational nanocarriers with a rational design have become increasingly popular in medical researches. Although nanoparticle-based drug delivery exhibits great potential, there are some challenges facing like rapid plasma clearance, triggering or aggravation of immune response, etc. Herein, cell-based targeted drug delivery systems have drawn more and more attention owing to low immunogenicity and intrinsic mutation rate, and innate ability to allow targeted delivery. Mesenchymal stem cells (MSCs) have been used in gene and drug delivery. The use of MSCs is a promising approach for the development of gene transfer systems and drug loading strategies because of their intrinsic properties, including homing ability and tumor tropism. By combining the inherent cell properties and merits of synthetic nanoparticles (NPs), cell membrane coated NPs emerge as the time requires. Overall, we provide a comprehensive overview of the utility of MSCs in drug and gene delivery as well as MSC membrane coated nanoparticles for therapy and drug delivery, aiming to figure out the significant room for development and highlight the potential future directions.

Biomimetic surface modification of discoidal polymeric particles

The rationale for the design of drug delivery nanoparticles is traditionally based on co-solvent self-assembly following bottom-up approaches or in combination with top-down approaches leading to tailored physiochemical properties to regulate biological responses. However, the optimal design and control of material properties to achieve specific biological responses remain the central challenge in drug delivery research. Considering this goal, we herein designed discoidal polymeric particles (DPPs) whose surfaces are re-engineered with isolated red blood cell (RBC) membranes to tailor their pharmacokinetics. The RBC membrane-coated DPPs (RBC-DPPs) were found to be biocompatible in cell-based in vitro experiments and exhibited extended blood circulation half-life. They also demonstrated unique kinetics at later time points in a mouse model compared to that of bare DPPs. Our results suggested that the incorporation of biomimicry would enable the biomimetic particles to cooperate with systems in the body such as cells and biomolecules to achieve specific biomedical goals.

Platelets and their biomimetics for regenerative medicine and cancer therapies

Platelets, circulating blood cells derived from megakaryocytes, play a key role in various physical activities, including coagulation, hemostasis, the body's innate immune response, and cancer metastasis. By taking advantage of their key traits, researchers have developed strategies to exploit platelets and platelet-mimicking nanoassemblies to treat a number of conditions, including wounds, cancers, and bacterial infections. Compared to traditional polymer, lipsosome, and inorganic nanoparticles-based delivery systems, platelets and platelet-mimicking vehicles hold many advantages. Among these are their enhanced circulation time, their large volumes and surface areas for drug loading or conjugation, and their inherent ability to target some diseases. In this review, we will highlight the recent progress made in the development of disease-targeting platelets- and platelet-mimicking-vehicles as therapeutic platforms.

Biomimetic Nanoemulsions for Oxygen Delivery In Vivo

Blood transfusion is oftentimes required for patients suffering from acute trauma or undergoing surgical procedures in order to help maintain the body's oxygen levels. The continued demand worldwide for blood products is expected to put significant strain on available resources and infrastructure. Unfortunately, efforts to develop viable alternatives to human red blood cells for transfusion are generally unsuccessful. Here, a hybrid natural-synthetic nanodelivery platform that combines the biocompatibility of the natural RBC membrane with the oxygen-carrying ability of perfluorocarbons is reported. The resulting formulation can be stored long-term and exhibits a high capacity for oxygen delivery, helping to mitigate the effects of hypoxia in vitro. In an animal model of hemorrhagic shock, mice are resuscitated at an efficacy comparable to whole blood infusion. By leveraging the advantageous properties of its constituent parts, this biomimetic oxygen delivery system may have the potential to address a critical need in the clinic.

Fabrication of Chlorophyll-Incorporated Nanogels for Potential Applications in Photothermal Cancer Therapy

Nanogels have been widely used in biomedical applications, such as carriers for hyperthermia cancer treatment, drug delivery, and imaging. Owing to the enhanced permeability and retention effect, nanogels have shown a great potential in cancer therapy. In this study, sodium copper chlorophyllin (SCC), a low cytotoxicity and biodegradable photothermal agent, was copolymerized with a nanogel of N-[3-(dimethylamino)propyl]methacrylamide. The nanogels could produce heat under exposure to a green laser with a 532 nm wavelength. The positively charged nature of the nanogels enhanced the endocytosis of the nanogels. The cell mortality was greatly enhanced with the treatment of the SCC-containing nanogels and green light illumination. Our results suggest the potential of SCC-containing nanogels in photothermal cancer therapy.

Erythrocyte-cancer hybrid membrane-camouflaged melanin nanoparticles for enhancing photothermal therapy efficacy in tumors

Cell membrane coating has emerged as an intriguing biomimetic strategy to endow nanomaterials with functions and properties inherent to source cells for various biomedical applications. Hybrid membrane of different types of cells could be coated onto nanoparticle surface to achieve additional functions. Herein, we fused red blood cell (RBC) membrane together with MCF-7 cell membrane and fabricated an erythrocyte-cancer (RBC-M) hybrid membrane-camouflaged melanin nanoparticle (Melanin@RBC-M) platform for enhancing therapeutic efficacy of photothermal therapy (PTT). The fused RBC-M hybrid membrane vesicles retained both RBC and MCF-7 cell membrane proteins and the resultant Melanin@RBC-M exhibited prolonged blood circulation and homotypic targeting to source MCF-7 cells simultaneously. Interestingly, increasing MCF-7 membrane components in RBC-M significantly enhanced the homotypic targeting function of Melanin@RBC-M while increasing RBC membrane components in RBC-M effectively reduced the cellular uptake of Melanin@RBC-M by macrophages and improved their circulation time in the blood. After intravenous injection into MCF-7 tumor-bearing athymic nude mice, Melanin@RBC-M with 1:1 membrane protein weight ratio of RBC to MCF-7 exhibited significantly higher tumor accumulation and better PTT efficacy compared with other Melanin@RBC-M with different membrane protein weight ratios as well as pristine melanin nanoparticles, due to the optimal balance between prolonged blood circulation and homotypic targeting. In addition, in vitro photoacoustic results revealed that Melanin@RBC-M had a photoacoustic signal enhancement with the increase of nanoparticle size (64 → 148 nm) and the photoacoustic amplitudes increased linearly with nanoparticle concentration at the excitation wavelength ranged from 680 nm to 800 nm, which could be used for quantification of Melanin@RBC-M in vivo. Looking forward, coating hybrid membrane onto nanoparticles could add flexibility and controllability in enhancing nanoparticles functionality and offer new opportunities for biomedical applications.

T-Cell-Mimicking Nanoparticles Can Neutralize HIV Infectivity

To improve human immunodeficiency virus (HIV) treatment and prevention, therapeutic strategies that can provide effective and broad-spectrum neutralization against viral infection are highly desirable. Inspired by recent advances of cell-membrane coating technology, herein, plasma membranes of CD4+ T cells are collected and coated onto polymeric cores. The resulting T-cell-membrane-coated nanoparticles (denoted as "TNPs") inherit T cell surface antigens critical for HIV binding, such as CD4 receptor and CCR5 or CXCR4 coreceptors. The TNPs act as decoys for viral attack and neutralize HIV by diverting the viruses away from their intended host targets. This decoy strategy, which simulates host cell functions for viral neutralization rather than directly suppressing viral replication machinery, has the potential to overcome HIV genetic diversity while not eliciting high selective pressure. In this study, it is demonstrated that TNPs selectively bind with gp120, a key envelope glycoprotein of HIV, and inhibit gp120-induced killing of bystander CD4+ T cells. Furthermore, when added to HIV viruses, TNPs effectively neutralize the viral infection of peripheral mononuclear blood cells and human-monocyte-derived macrophages in a dose-dependent manner. Overall, by leveraging natural T cell functions, TNPs show great potential as a new therapeutic agent against HIV infection.

Engineering biological interactions on the nanoscale

Nanoparticulate platforms have contributed significantly to the field of biomedical research, demonstrating advantages over traditional modalities in areas such as drug delivery, detoxification, and vaccination. When it comes to the design of nanoparticles, biomimetic strategies have become increasingly popular as a means of promoting effective interactions with biological systems. A recently developed cell membrane-coated nanoparticle platform can leverage the natural interactions that cells engage in with other cells, the extracellular matrix, and biomolecules in order to reduce undesirable nonspecific interactions, while increasing target-specific interactions. Here, we discuss the current state of these biomimetic nanoparticles and highlight how they can be used for various biomedical applications.

T-Cell-Mimicking Nanoparticles Can Neutralize HIV Infectivity

To improve human immunodeficiency virus (HIV) treatment and prevention, therapeutic strategies that can provide effective and broad-spectrum neutralization against viral infection are highly desirable. Inspired by recent advances of cell-membrane coating technology, herein, plasma membranes of CD4⁺ T cells are collected and coated onto polymeric cores. The resulting T-cell-membrane-coated nanoparticles (denoted as "TNPs") inherit T cell surface antigens critical for HIV binding, such as CD4 receptor and CCR5 or CXCR4 coreceptors. The TNPs act as decoys for viral attack and neutralize HIV by diverting the viruses away from their intended host targets. This decoy strategy, which simulates host cell functions for viral neutralization rather than directly suppressing viral replication machinery, has the potential to overcome HIV genetic diversity while not eliciting high selective pressure. In this study, it is demonstrated that TNPs selectively bind with gp120, a key envelope glycoprotein of HIV, and inhibit gp120-induced killing of bystander CD4⁺ T cells. Furthermore, when added to HIV viruses, TNPs effectively neutralize the viral infection of peripheral mononuclear blood cells and human-monocyte-derived macrophages in a dose-dependent manner. Overall, by leveraging natural T cell functions, TNPs show great potential as a new therapeutic agent against HIV infection.

Cell-Like Micromotors

In the past decade, versatile micro- and nanosized machines have emerged as active agents for large-scale detoxification, sensing, microfabrication, and many other promising applications. Micromachines have also been envisioned as the next advancement in dynamic therapy with numerous proof-of-concept studies in drug delivery, microsurgery, and detoxification. However, the practical use of synthetic micromotors in the body requires the development of fully biocompatible designs facilitating micromotor movement in biological fluids of diverse composition and displaying desired functions in specific locations. The combination of the efficient movement of synthetic micromotors with the biological functions of natural cells has resulted in cell-like micromotors with expanded therapeutic and toxin-removing capabilities toward different biological applications. Thus, these biocompatible and biomimetic cell-like micromotors can provide efficient movement in complex biofluids and mimic the functionalities of natural cells. This Account highlights a variety of recent proof-of-concept examples of cell-like micromotors, based on different designs and actuation mechanisms, which perform diverse in vivo tasks. The cell-like micromotors are divided into two groups: (i) cell membrane-coated micromotors, which use natural cell membranes derived from red blood cells, platelets, or a combination of different cells to cloak and functionalize synthetic motors, and (ii) cell-based micromotors, which directly use entire cells such as blood cells, spermatozoa, and bacteria as the micromotor engine. Cell-like micromotors, composed of different cellular components and actuated by different mechanisms, have shown unique advantages for operation in complex biofluids such as blood. Due to the inherent biocompatibility of cell-derived materials, these cell-like micromotors do not provoke an immune response while utilizing useful secondary functions of the blood cells such as strong ability to soak up foreign agents or bind toxins. Additionally, the utilization of autonomously motile cells (e.g., bacteria) allows for built-in chemotactic motion, which eliminates the need for harmful fuels or complex actuation equipment. Furthermore, a broad range of cells, both passive and motile, can be incorporated into micromachine designs constituting a large library of functional components depending on the limits of the desired application. The coupling of cellular and artificial components has led to active biohybrid swimming microsystems with greatly enhanced capabilities and functionalities compared to the individual biological or synthetic components. These characteristics have positioned these cell-like micromotors as promising biomimetic dynamic tools for potential actuation in vivo. Finally, the key challenges and limitations of cell-like micromotors are discussed in the context of expanded future clinical uses and translation to human trials.

Hierarchical Tumor Microenvironment-Responsive Nanomedicine for Programmed Delivery of Chemotherapeutics

Nanomedicines have been demonstrated to have passive or active tumor targeting behaviors, which are promising for cancer chemotherapy. However, most nanomedicines still suffer from a suboptimal targeting effect and drug leakage, resulting in unsatisfactory treatment outcome. Herein, a hierarchical responsive nanomedicine (HRNM) is developed for programmed delivery of chemotherapeutics. The HRNMs are prepared via the self-assembly of cyclic Arg-Gly-Asp (RGD) peptide conjugated triblock copolymer, poly(2-(hexamethyleneimino)ethyl methacrylate)-poly(oligo-(ethylene glycol) monomethyl ether methacrylate)-poly[reduction-responsive camptothecin] (PC7A-POEG-PssCPT). In blood circulation, the RGD peptides are shielded by the POEG coating; therefore, the nanosized HRNMs can achieve effective tumor accumulation through passive targeting. Once the HRNMs reach a tumor site, due to the hydrophobic-tohydrophilic conversion of PC7A chains induced by the acidic tumor microenvironment, the RGD peptides will be exposed for enhanced tumor retention and cellular internalization. Moreover, in response to the glutathione inside cells, active CPT drugs will be released rapidly for chemotherapy. The in vitro and in vivo results confirm effective tumor targeting, potent antitumor effect, and reduced systemic toxicity of the HRNMs. This HRNM is promising for enhanced chemotherapeutic delivery.

Cell Membrane Coated Semiconducting Polymer Nanoparticles for Enhanced Multimodal Cancer Phototheranostics

Phototheranostic nanoagents are promising for early diagnosis and precision therapy of cancer. However, their imaging ability and therapeutic efficacy are often limited due to the presence of delivery barriers in the tumor microenvironment. Herein, we report the development of organic multimodal phototheranostic nanoagents that can biomimetically target cancer-associated fibroblasts in the tumor microenvironment for enhanced multimodal imaging-guided cancer therapy. Such biomimetic nanocamouflages comprise a near-infrared (NIR) absorbing semiconducting polymer nanoparticle (SPN) coated with the cell membranes of activated fibroblasts. The homologous targeting mechanism allows the activated fibroblast cell membrane coated SPN (AF-SPN) to specifically target cancer-associated fibroblasts, leading to enhanced tumor accumulation relative to the uncoated and cancer cell membrane coated counterparts after systemic administration in living mice. As such, AF-SPN not only provides stronger NIR fluorescence and photoacoustic signals to detect tumors but also generates enhanced cytotoxic heat and singlet oxygen to exert combinational photothermal and photodynamic therapy, ultimately leading to an antitumor efficacy higher than that of the counterparts. This study introduces an organic phototheranostic system that biomimetically targets the component in the tumor microenvironment for enhanced multimodal cancer theranostics.

Cell membrane coating for reducing nanoparticle-induced inflammatory responses to scaffold constructs

The controlled release of therapeutics from micro or nanoparticles has been well-studied. Incorporation of these particles inside biomaterial scaffolds is promising for tissue regeneration and immune modulation. However, these particles may induce inflammatory and foreign body responses to scaffold constructs, limiting their applications. Here we show that widely used poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs) formed by double emulsion dramatically increased neutrophil infiltration and pro-inflammatory cytokines in alginate scaffolds 1 day after the subcutaneous injection of the scaffolds into mice. The coating of red blood cell (RBC) membranes on PLGA NPs completely eliminated these short-term inflammatory responses. For a longer term of 10 days, neither PLGA NPs nor RBC membrane-coated nanoparticles exerted a significant effect on the infiltration of neutrophils or macrophages in alginate scaffolds possibly due to the degradation and/or clearance of nanoparticles by infiltrating cells by that time. Despite the extensive exploration of cell membrane-coated nanoparticles, our study is the first to investigate the effects of cell membrane coating on foreign body reaction to nanoparticles. Harnessing the natural biocompatibility of cell membranes, our strategy of anti-inflammatory protection for scaffolds may be pivotal for many applications, such as those relying on the recruitment of stem cells and/or progenitor cells to scaffolds.

Erythrocyte–platelet hybrid membranes coating polypyrrol nanoparticles for enhanced delivery and photothermal therapy

A dual-membrane coating technique was developed to camouflage polypyrrole nanoparticles with red blood cells and platelet membranes for enhanced delivery and photothermal tumor therapy.