Biomimetic Rebuilding of Multifunctional Red Blood Cells: Modular Design Using Functional Components

The Application of Drugs and Nano-Therapies Targeting Immune Cells in Hypoxic Inflammation

Immune cells are pivotal in the dynamic interplay between hypoxia and inflammation. During hypoxic conditions, HIF-1α, a crucial transcription factor, facilitates the adaptation of immune cells to the hypoxic micro-environment. This adaptation includes regulating immune cell metabolism, significantly impacting inflammation development. Strategies for anti-inflammatory and hypoxic relief have been proposed, aiming to disrupt the hypoxia-inflammation nexus. Research extensively focuses on anti-inflammatory agents and materials that target immune cells. These primarily mitigate hypoxic inflammation by encouraging M2-macrophage polarization, restraining neutrophil proliferation and infiltration, and maintaining Treg/TH17 balance. Additionally, oxygen-releasing nano-materials play a significant role. By alleviating hypoxia and clearing reactive oxygen species (ROS), these nano-materials indirectly influence immune cell functions. This paper delves into the response of immune cells under hypoxic conditions and the resultant effects on inflammation. It provides a comprehensive overview of various therapies targeting specific immune cells for anti-inflammatory purposes and explores nano-materials that either carry or generate oxygen to alleviate anoxic micro-environments.

Revolutionizing Neurocare: Biomimetic Nanodelivery Via Cell Membranes

Brain disorders represent a significant challenge in medical science due to the formidable blood-brain barrier (BBB), which severely limits the penetration of conventional therapeutics, hindering effective treatment strategies. This review delves into the innovative realm of biomimetic nanodelivery systems, including stem cell-derived nanoghosts, tumor cell membrane-coated nanoparticles, and erythrocyte membrane-based carriers, highlighting their potential to circumvent the BBB's restrictions. By mimicking native cell properties, these nanocarriers emerge as a promising solution for enhancing drug delivery to the brain, offering a strategic advantage in overcoming the barrier's selective permeability. The unique benefits of leveraging cell membranes from various sources is evaluated and advanced technologies for fabricating cell membrane-encapsulated nanoparticles capable of masquerading as endogenous cells are examined. This enables the targeted delivery of a broad spectrum of therapeutic agents, ranging from small molecule drugs to proteins, thereby providing an innovative approach to neurocare. Further, the review contrasts the capabilities and limitations of these biomimetic nanocarriers with traditional delivery methods, underlining their potential to enable targeted, sustained, and minimally invasive treatment modalities. This review is concluded with a perspective on the clinical translation of these biomimetic systems, underscoring their transformative impact on the therapeutic landscape for intractable brain diseases.

A Survey of Recent Developments in Magnetic Microrobots for Micro-/Nano-Manipulation

Magnetically actuated microrobots have become a research hotspot in recent years due to their tiny size, untethered control, and rapid response capability. Moreover, an increasing number of researchers are applying them for micro-/nano-manipulation in the biomedical field. This survey provides a comprehensive overview of the recent developments in magnetic microrobots, focusing on materials, propulsion mechanisms, design strategies, fabrication techniques, and diverse micro-/nano-manipulation applications. The exploration of magnetic materials, biosafety considerations, and propulsion methods serves as a foundation for the diverse designs discussed in this review. The paper delves into the design categories, encompassing helical, surface, ciliary, scaffold, and biohybrid microrobots, with each demonstrating unique capabilities. Furthermore, various fabrication techniques, including direct laser writing, glancing angle deposition, biotemplating synthesis, template-assisted electrochemical deposition, and magnetic self-assembly, are examined owing to their contributions to the realization of magnetic microrobots. The potential impact of magnetic microrobots across multidisciplinary domains is presented through various application areas, such as drug delivery, minimally invasive surgery, cell manipulation, and environmental remediation. This review highlights a comprehensive summary of the current challenges, hurdles to overcome, and future directions in magnetic microrobot research across different fields.

Bio-Hybrid Magnetic Robots: From Bioengineering to Targeted Therapy

Magnetic robots possess an innate ability to navigate through hard-to-reach cavities in the human body, making them promising tools for diagnosing and treating diseases minimally invasively. Despite significant advances, the development of robots with desirable locomotion and full biocompatibility under harsh physiological conditions remains challenging, which put forward new requirements for magnetic robots' design and material synthesis. Compared to robots that are synthesized with inorganic materials, natural organisms like cells, bacteria or other microalgae exhibit ideal properties for in vivo applications, such as biocompatibility, deformability, auto-fluorescence, and self-propulsion, as well as easy for functional therapeutics engineering. In the process, these organisms can provide autonomous propulsion in biological fluids or external magnetic fields, while retaining their functionalities with integrating artificial robots, thus aiding targeted therapeutic delivery. This kind of robotics is named bio-hybrid magnetic robotics, and in this mini-review, recent progress including their design, engineering and potential for therapeutics delivery will be discussed. Additionally, the historical context and prominent examples will be introduced, and the complexities, potential pitfalls, and opportunities associated with bio-hybrid magnetic robotics will be discussed.

Artificial cells for in vivo biomedical applications through red blood cell biomimicry

Recent research in artificial cell production holds promise for the development of delivery agents with therapeutic effects akin to real cells. To succeed in these applications, these systems need to survive the circulatory conditions. In this review we present strategies that, inspired by the endurance of red blood cells, have enhanced the viability of large, cell-like vehicles for in vivo therapeutic use, particularly focusing on giant unilamellar vesicles. Insights from red blood cells can guide modifications that could transform these platforms into advanced drug delivery vehicles, showcasing biomimicry's potential in shaping the future of therapeutic applications.

AI-enhanced biomedical micro/nanorobots in microfluidics

Human beings encompass sophisticated microcirculation and microenvironments, incorporating a broad spectrum of microfluidic systems that adopt fundamental roles in orchestrating physiological mechanisms. In vitro recapitulation of human microenvironments based on lab-on-a-chip technology represents a critical paradigm to better understand the intricate mechanisms. Moreover, the advent of micro/nanorobotics provides brand new perspectives and dynamic tools for elucidating the complex process in microfluidics. Currently, artificial intelligence (AI) has endowed micro/nanorobots (MNRs) with unprecedented benefits, such as material synthesis, optimal design, fabrication, and swarm behavior. Using advanced AI algorithms, the motion control, environment perception, and swarm intelligence of MNRs in microfluidics are significantly enhanced. This emerging interdisciplinary research trend holds great potential to propel biomedical research to the forefront and make valuable contributions to human health. Herein, we initially introduce the AI algorithms integral to the development of MNRs. We briefly revisit the components, designs, and fabrication techniques adopted by robots in microfluidics with an emphasis on the application of AI. Then, we review the latest research pertinent to AI-enhanced MNRs, focusing on their motion control, sensing abilities, and intricate collective behavior in microfluidics. Furthermore, we spotlight biomedical domains that are already witnessing or will undergo game-changing evolution based on AI-enhanced MNRs. Finally, we identify the current challenges that hinder the practical use of the pioneering interdisciplinary technology.

Synthetic Biohybrids of Red Blood Cells and Cascaded-Enzymes@ Metal-Organic Frameworks for Hyperuricemia Treatment

Hyperuricemia, caused by an imbalance between the rates of production and excretion of uric acid (UA), may greatly increase the mortality rates in patients with cardiovascular and cerebrovascular diseases. Herein, for fast-acting and long-lasting hyperuricemia treatment, armored red blood cell (RBC) biohybrids, integrated RBCs with proximal, cascaded-enzymes of urate oxidase (UOX) and catalase (CAT) encapsulated within ZIF-8 framework-based nanoparticles, have been fabricated based on a super-assembly approach. Each component is crucial for hyperuricemia treatment: 1) RBCs significantly increase the circulation time of nanoparticles; 2) ZIF-8 nanoparticles-based superstructure greatly enhances RBCs resistance against external stressors while preserving native RBC properties (such as oxygen carrying capability); 3) the ZIF-8 scaffold protects the encapsulated enzymes from enzymatic degradation; 4) no physical barrier exists for urate diffusion, and thus allow fast degradation of UA in blood and neutralizes the toxic by-product H2 O2 . In vivo results demonstrate that the biohybrids can effectively normalize the UA level of an acute hyperuricemia mouse model within 2 h and possess a longer elimination half-life (49.7 ± 4.9 h). They anticipate that their simple and general method that combines functional nanomaterials with living cell carriers will be a starting point for the development of innovative drug delivery systems.

Biomimetic Nano-Drug Delivery System: An Emerging Platform for Promoting Tumor Treatment

With the development of nanotechnology, nanoparticles (NPs) have shown broad prospects as drug delivery vehicles. However, they exhibit certain limitations, including low biocompatibility, poor physiological stability, rapid clearance from the body, and nonspecific targeting, which have hampered their clinical application. Therefore, the development of novel drug delivery systems with improved biocompatibility and high target specificity remains a major challenge. In recent years, biofilm mediated biomimetic nano-drug delivery system (BNDDS) has become a research hotspot focus in the field of life sciences. This new biomimetic platform uses bio-nanotechnology to encapsulate synthetic NPswithin biomimetic membrane, organically integrating the low immunogenicity, low toxicity, high tumor targeting, good biocompatibility of the biofilm with the adjustability and versatility of the nanocarrier, and shows promising applications in the field of precision tumor therapy. In this review, we systematically summarize the new progress in BNDDS used for optimizing drug delivery, providing a theoretical reference for optimizing drug delivery and designing safe and efficient treatment strategies to improve tumor treatment outcomes.

Extending the In Vivo Residence Time of Macrophage Membrane-Coated Nanoparticles through Genetic Modification

Nanoparticles coated with natural cell membranes have emerged as a promising class of biomimetic nanomedicine with significant clinical potential. Among them, macrophage membrane-coated nanoparticles hold particular appeal due to their versatility in drug delivery and biological neutralization applications. This study employs a genetic engineering approach to enhance their in vivo residence times, aiming to further improve their performance. Specifically, macrophages are engineered to express proline-alanine-serine (PAS) peptide chains, which provide additional protection against opsonization and phagocytosis. The resulting modified nanoparticles demonstrate prolonged residence times when administered intravenously or introduced intratracheally, surpassing those coated with the wild-type membrane. The longer residence times also contribute to enhanced nanoparticle efficacy in inhibiting inflammatory cytokines in mouse models of lipopolysaccharide-induced lung injury and sublethal endotoxemia, respectively. This study underscores the effectiveness of genetic modification in extending the in vivo residence times of macrophage membrane-coated nanoparticles. This approach can be readily extended to modify other cell membrane-coated nanoparticles toward more favorable biomedical applications.

Red blood cells: a potential delivery system

Red blood cells (RBCs) are the most abundant cells in the body, possessing unique biological and physical properties. RBCs have demonstrated outstanding potential as delivery vehicles due to their low immunogenicity, long-circulating cycle, and immune characteristics, exhibiting delivery abilities. There have been several developments in understanding the delivery system of RBCs and their derivatives, and they have been applied in various aspects of biomedicine. This article compared the various physiological and physical characteristics of RBCs, analyzed their potential advantages in delivery systems, and summarized their existing practices in biomedicine.

Tailored Beta-Lapachone Nanomedicines for Cancer-Specific Therapy

Nanotechnology shows the power to improve efficacy and reduce the adverse effects of anticancer agents. As a quinone-containing compound, beta-lapachone (LAP) is widely employed for targeted anticancer therapy under hypoxia. The principal mechanism of LAP-mediated cytotoxicity is believed due to the continuous generation of reactive oxygen species with the aid of NAD(P)H: quinone oxidoreductase 1 (NQO1). The cancer selectivity of LAP relies on the difference between NQO1 expression in tumors and that in healthy organs. Despite this, the clinical translation of LAP faces the problem of narrow therapeutic window that is challenging for dose regimen design. Herein, the multifaceted anticancer mechanism of LAP is briefly introduced, the advance of nanocarriers for LAP delivery is reviewed, and the combinational delivery approaches to enhance LAP potency in recent years are summarized. The mechanisms by which nanosystems boost LAP efficacy, including tumor targeting, cellular uptake enhancement, controlled cargo release, enhanced Fenton or Fenton-like reaction, and multidrug synergism, are also presented. The problems of LAP anticancer nanomedicines and the prospective solutions are discussed. The current review may help to unlock the potential of cancer-specific LAP therapy and speed up its clinical translation.

Recent advances in micro-sized oxygen carriers inspired by red blood cells

Supplementing sufficient oxygen to cells is always challenging in biomedical engineering fields such as tissue engineering. Originating from the concept of a 'blood substitute', nano-sized artificial oxygen carriers (AOCs) have been studied for a long time for the optimization of the oxygen supplementation and improvement of hypoxia environments in vitro and in vivo. When circulating in our bodies, micro-sized human red blood cells (hRBCs) feature a high oxygen capacity, a unique biconcave shape, biomechanical and rheological properties, and low frictional surfaces, making them efficient natural oxygen carriers. Inspired by hRBCs, recent studies have focused on evolving different AOCs into microparticles more feasibly able to achieve desired architectures and morphologies and to obtain the corresponding advantages. Recent micro-sized AOCs have been developed into additional categories based on their principal oxygen-carrying or oxygen-releasing materials. Various biomaterials such as lipids, proteins, and polymers have also been used to prepare oxygen carriers owing to their rapid oxygen transfer, high oxygen capacity, excellent colloidal stability, biocompatibility, suitable biodegradability, and long storage. In this review, we concentrated on the fabrication techniques, applied biomaterials, and design considerations of micro-sized AOCs to illustrate the advances in their performances. We also compared certain recent micro-sized AOCs with hRBCs where applicable and appropriate. Furthermore, we discussed existing and potential applications of different types of micro-sized AOCs.

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.

Ultrasound-Targeted Microbubble Destruction-Mediated Cell-Mimetic Nanodrugs for Treating Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that mainly affects joints, and it can lead to disability and damage to vital organs if not diagnosed and treated in time. However, all current therapeutic agents for RA have limitations such as high dose, severe side effects, long-term use, and unsatisfactory therapeutic effects. The long-term use and dose escalation of methotrexate (MTX) may cause mild and severe side effects. To overcome the limitations, it is critical to target drug delivery to the inflamed joints. In this work, we constructed a folic acid-targeted and cell-mimetic nanodrug, MTX-loaded mesoporous silica composite nanoplatform (MMPRF), which can regulate drug release under ultrasound (US) and microbubble (MB) mediation. The targeted delivery and drug therapy were investigated through in vitro RAW264.7 cell experiments and in vivo collagen-induced arthritis animal experiments. The result showed that the targeting ability to the joints of MMPRF was strong and was more significant after US and MB mediation, which can potently reduce joint swelling, bone erosion, and inflammation in joints. This work indicated that the US- and MB-mediated MMPRF not only would be a promising method for synergistic targeted treatment of RA but also may show high potential for serving as a nanomedicine for many other biomedical fields.

Probing the Interaction Between Supercarrier RBC Membrane and Nanoparticles for Optimal Drug Delivery

Red blood cell (RBC) membrane-hitchhiking nanoparticles (NPs) have been an increasingly popular supercarrier for targeted drug delivery. However, the kinetic details of the shear-induced NP detachment process from RBC in blood flow remain unclear. Here, we perform detailed computational simulations of the traversal dynamics of an RBC-NP composite supercarrier with tunable properties. We show that the detachment of NPs from RBC occurs in a shear-dependent manner which is consistent with previous experiment results. We quantify the NP detachment rate in the microcapillary flow, and our simulation results suggest that there may be an optimal adhesion strength span of 25-40 μJ/m² for rigid spherical NPs to improve the supercarrier performance and targeting efficiency. In addition, we find that the stiffness and the shape of NPs alter the detachment efficiency by changing the RBC-NP contact areas. Together, these findings provide unique insights into the shear-dependent NP release from the RBC surface, facilitating the clinical utility of RBC-NP composite supercarriers in targeted and localized drug delivery with high precision and efficiency.

Bridging the In Vitro to In Vivo gap: Using the Chick Embryo Model to Accelerate Nanoparticle Validation and Qualification for In Vivo studies

We postulate that nanoparticles (NPs) for use in therapeutic applications have largely not realized their clinical potential due to an overall inability to use in vitro results to predict NP performance in vivo. The avian embryo and associated chorioallantoic membrane (CAM) has emerged as an in vivo preclinical model that bridges the gap between in vitro and in vivo, enabling rapid screening of NP behavior under physiologically relevant conditions and providing a rapid, accessible, economical, and more ethical means of qualifying nanoparticles for in vivo use. The CAM is highly vascularized and mimics the diverging/converging vasculature of the liver, spleen, and lungs that serve as nanoparticle traps. Intravital imaging of fluorescently labeled NPs injected into the CAM vasculature enables immediate assessment and quantification of nano-bio interactions at the individual NP scale in any tissue of interest that is perfused with a microvasculature. In this review, we highlight how utilization of the avian embryo and its CAM as a preclinical model can be used to understand NP stability in blood and tissues, extravasation, biocompatibility, and NP distribution over time, thereby serving to identify a subset of NPs with the requisite stability and performance to introduce into rodent models and enabling the development of structure-property relationships and NP optimization without the sacrifice of large populations of mice or other rodents. We then review how the chicken embryo and CAM model systems have been used to accelerate the development of NP delivery and imaging agents by allowing direct visualization of targeted (active) and nontargeted (passive) NP binding, internalization, and cargo delivery to individual cells (of relevance for the treatment of leukemia and metastatic cancer) and cellular ensembles (e.g., cancer xenografts of interest for treatment or imaging of cancer tumors). We conclude by showcasing emerging techniques for the utilization of the CAM in future nano-bio studies.

Near-Infrared-II Activatable Symbiotic 2D Carbon-Clay Nanohybrids for Dual Imaging-Guided Combinational Cancer Therapy

Two-dimensional (2D) nanomaterials hold great potential for cancer theranostic applications, yet their clinical translation faces great challenges of high toxicity and limited therapeutic/diagnostic modality. Here, we have created a kind of symbiotic 2D carbon-2D clay nanohybrids, which are composed of a novel 2D carbon nanomaterial (carbon nanochips, or CNC), prepared by carbonizing a conjugated polymer polydiiodobutadiyne, and a 2D layered aluminosilicate clay mineral montmorillonite (MMT). Intriguingly, with the formation of the nanohybrids, MMT can help the dispersion of CNC, while CNC can significantly reduce the hemolysis and toxicity of MMT. The symbiotic combination of CNC and MMT also leads to a synergistic anti-cancer theranostic effect. CNC has a strong absorption and high photothermal conversion efficiency in the second near-infrared region (NIR-II, 1000-1700 nm), while MMT contains Fe3+ that can facilitate the generation of reactive oxygen species from highly expressed H2O2 in tumor microenvironment. The nanohybrids not only enable a synergy of photothermal therapy and chemodynamic therapy to suppress the extremely rapid growth of RM1 tumors in mice but also allow for dual photoacoustic and magnetic imaging to guide the drug delivery and NIR-II irradiation execution, hence establishing a highly efficient and biosafe "all-in-one" theranostic platform for precision nanomedicine.

Long-term whole blood DNA preservation by cost-efficient cryosilicification

Deoxyribonucleic acid (DNA) is the blueprint of life, and cost-effective methods for its long-term storage could have many potential benefits to society. Here we present the method of in situ cryosilicification of whole blood cells, which allows long-term preservation of DNA. Importantly, our straightforward approach is inexpensive, reliable, and yields cryosilicified samples that fulfill the essential criteria for safe, long-term DNA preservation, namely robustness against external stressors, such as radical oxygen species or ultraviolet radiation, and long-term stability in humid conditions at elevated temperatures. Our approach could enable the room temperature storage of genomic information in book-size format for more than one thousand years (thermally equivalent), costing only 0.5 $/person. Additionally, our demonstration of 3D-printed DNA banking artefacts, could potentially allow 'artificial fossilization'.

Cell Membrane-Camouflaged Nanocarriers with Biomimetic Deformability of Erythrocytes for Ultralong Circulation and Enhanced Cancer Therapy

Despite considerable advancements in cell membrane-camouflaged nanocarriers to leverage natural cell functions, artificial nanocarriers that can accurately mimic both the biological and physical properties of cells are urgently needed. Herein, inspired by the important effect of the stiffness and deformability of natural red blood cells (RBCs) on their life span and flowing through narrow vessels, we report the construction of RBC membrane-camouflaged nanocarriers that can mimic RBCs at different life stages and study how the deformability of RBC-derived nanocarriers affects their biological behaviors. RBC membrane-coated elastic poly(ethylene glycol) diacrylate hydrogel nanoparticles (RBC-ENPs) simulating dynamic RBCs exhibited high immunocompatibility with minimum immunoglobulin adsorption in the surface protein corona, resulting in reduced opsonization in macrophages and ultralong circulation. Furthermore, RBC-ENPs can deform like RBCs and achieve excellent diffusion in tumor extracellular matrix, leading to improved multicellular spheroid penetration and tumor tissue accumulation. In mouse cancer models, doxorubicin-loaded RBC-ENPs demonstrated superior antitumor efficacy to the first-line chemotherapeutic drug PEGylated doxorubicin liposomes. Our work highlights that tuning the physical properties of cell membrane-derived nanocarriers may offer an alternative approach for the bionic design of nanomedicines in the future.

Hierarchical Structures in Macromolecule-assembled Synthetic Cells

Various models of synthetic cells have been developed as researchers have sought to explore the origin of life. Based on the fact that structural complexity is the foundation of higher-order functions, this review will focus on hierarchical structures in synthetic cell models that are inspired by living systems, in which macromolecules are the dominant participants. We discuss the underlying advantages and functions provided by biomimetic higher-order structures from four perspectives, including hierarchical structures in membranes, in the composite construction of membrane-coated artificial cytoplasm, in organelle-like subcellular compartments, as well as in synthetic cell-cell assembled synthetic tissues. In parallel, various feasible driving forces and approaches for the fabrication of such higher-order structures are showcased. Furthermore, we highlight both the implemented and potential applications of biomimetic systems, bottom-up biosynthesis, biomedical tissue engineering, and disease therapy. This thriving field is gradually narrowing the gap between fundamental research and applied science. This article is protected by copyright. All rights reserved.

Cyclic arginine-glycine-aspartic acid-modified red blood cells for drug delivery: Synthesis and in vitro evaluation

Red blood cells (RBCs) are an excellent choice for cell preparation research because of their biocompatibility, high drug loading, and long half-life. In this study, doxorubicin (DOX) was encapsulated with RBCs as the carrier. The biotin-avidin system binding principle was used to modify biotinylated cyclic arginine-glycine-aspartic acid (cRGD) onto RBC surfaces for accurate targeting, high drug loading, and sustained drug release. The RBC drug delivery system (DDS) was characterized, and the concentration of surface sulfur in the energy spectrum was 6.330%. The physical and chemical properties of RBC DDS were as follows: drug content, 0.857 mg/mL; particle size, 3339 nm; potential value, -12.5 mV; and cumulative release rate, 81.35%. There was no significant change in RBC morphology for up to seven days. The results of the targeting and cytotoxicity studies of RBC DDS showed that many RBCs covered the surfaces of U251 cells, and the fluorescence intensity was higher than that of MCF-7 cells. The IC50 value of unmodified drug-loaded RBCs was 2.5 times higher than that of targeted modified drug-loaded RBCs, indicating that the targeting of cancer cells produced satisfactory inhibition. This study confirms that the RBC DDS has the characteristics of accurate targeting, high drug loading, and slow drug release, which increases its likelihood of becoming a clinical cancer treatment in the future.

Magnetic bio-hybrid micro actuators

Over the past two decades, there has been a growing body of work on wireless devices that can operate on the length scales of biological cells and even smaller. A class of these devices receiving increasing attention are referred to as bio-hybrid actuators: tools that integrate biological cells or subcellular parts with synthetic or inorganic components. These devices are commonly controlled through magnetic manipulation as magnetic fields and gradients can be generated with a high level of control. Recent work has demonstrated that magnetic bio-hybrid actuators can address common challenges in small scale fabrication, control, and localization. Additionally, it is becoming apparent that these magnetically driven bio-hybrid devices can display high efficiency and, in many cases, have the potential for self-repair and even self-replication. Combining these properties with magnetically driven forces and torques, which can be transmitted over significant distances, can be highly controlled, and are biologically safe, gives magnetic bio-hybrid actuators significant advantages over other classes of small scale actuators. In this review, we describe the theory and mechanisms required for magnetic actuation, classify bio-hybrid actuators by their diverse organic components, and discuss their current limitations. Insights into the future of coupling cells and cell-derived components with magnetic materials to fabricate multi-functional actuators are also provided.

Cell-based biocomposite engineering directed by polymers

Biological cells such as bacterial, fungal, and mammalian cells always exploit sophisticated chemistries and exquisite micro- and nano-structures to execute life activities, providing numerous templates for engineering bioactive and biomorphic materials, devices, and systems. To transform biological cells into functional biocomposites, polymer-directed cell surface engineering and intracellular functionalization have been developed over the past two decades. Polymeric materials can be easily adopted by various cells through polymer grafting or in situ hydrogelation and can successfully bridge cells with other functional materials as interfacial layers, thus achieving the manufacture of advanced biocomposites through bioaugmentation of living cells and transformation of cells into templated materials. This review article summarizes the recent progress in the design and construction of cell-based biocomposites by polymer-directed strategies. Furthermore, the applications of cell-based biocomposites in broad fields such as cell research, biomedicine, and bioenergy are discussed. Last, we provide personal perspectives on challenges and future trends in this interdisciplinary area.

Robust and Long-Term Cellular Protein and Enzymatic Activity Preservation in Biomineralized Mammalian Cells

Preservation of evolved biological structure and function in robust engineering materials is of interest for storage of biological samples before diagnosis and development of vaccines, sensors, and enzymatic reactors and has the potential to avoid cryopreservation and its associated cold-chain issues. Here, we demonstrate that "freezing cells in amorphous silica" is a powerful technique for long-term preservation of whole mammalian cell proteomic structure and function at room temperature. Biomimetic silicification employs the crowded protein microenvironment of mammalian cells as a catalytic framework to proximally transform monomeric silicic acid into silicates forming a nanoscopic silica shell over all biomolecular interfaces. Silicification followed by dehydration preserves and passivates proteomic information within a nanoscale thin silica coating that exhibits size selective permeability (<3.6 nm), preventing protein leaching and protease degradation of cellular contents, while providing access of small molecular constituents for cellular enzymatic reaction. Exposure of dehydrated silicified cells to mild etchant or prolonged hydrolysis removes the silica, completely rerevealing biomolecular components and restoring their accessibility and functionality.

Nano/Micromotors in Active Matter

Nano/micromotors (NMMs) are tiny objects capable of converting energy into mechanical motion. Recently, a wealth of active matter including synthetic colloids, cytoskeletons, bacteria, and cells have been used to construct NMMs. The self-sustained motion of active matter drives NMMs out of equilibrium, giving rise to rich dynamics and patterns. Alongside the spontaneous dynamics, external stimuli such as geometric confinements, light, magnetic field, and chemical potential are also harnessed to control the movements of NMMs, yielding new application paradigms of active matter. Here, we review the recent advances, both experimental and theoretical, in exploring biological NMMs. The unique dynamical features of collective NMMs are focused on, along with some possible applications of these intriguing systems.

Biohybrid Micro- and Nanorobots for Intelligent Drug Delivery

Biohybrid micro- and nanorobots are integrated tiny machines from biological components and artificial components. They can possess the advantages of onboard actuation, sensing, control, and implementation of multiple medical tasks such as targeted drug delivery, single-cell manipulation, and cell microsurgery. This review paper is to give an overview of biohybrid micro- and nanorobots for smart drug delivery applications. First, a wide range of biohybrid micro- and nanorobots comprising different biological components are reviewed in detail. Subsequently, the applications of biohybrid micro- and nanorobots for active drug delivery are introduced to demonstrate how such biohybrid micro- and nanorobots are being exploited in the field of medicine and healthcare. Lastly, key challenges to be overcome are discussed to pave the way for the clinical translation and application of the biohybrid micro- and nanorobots.

A Multifunctional Magnetic Red Blood Cell-Mimetic Micromotor for Drug Delivery and Image-Guided Therapy

Inspired by nature, innovative devices have been made to imitate the morphology and functions of natural red blood cells (RBCs). Here, we report a red blood cell-mimetic micromotor (RBCM), which was fabricated based on a layer-by-layer assembly method and precisely controlled by an external rotating uniform magnetic field. The main framework of the RBCM was constructed by the natural protein zein and finally camouflaged with the RBC membrane. Functional cargos such as Fe₃O₄ nanoparticles and the chemotherapeutic agent doxorubicin were loaded within the wall part of the RBCM for tumor therapy. Due to the massive loading of Fe₃O₄ nanoparticles, the RBCM can be precisely navigated by an external rotating uniform magnetic field and be used as a magnetic resonance imaging contrast agent for tumor imaging. The RBCM has been proven to be biocompatible, biodegradable, magnetically manipulated, and imageable, which are key requisites to take micromotors from the chalkboard to clinics. We expect the RBC-inspired biohybrid device to achieve wide potential applications.

Design, fabrication and application of magnetically actuated micro/nanorobots: a review

Magnetically actuated micro/nanorobots are typical micro- and nanoscale artificial devices with favorable attributes of quick response, remote and contactless control, harmless human-machine interaction and high economic efficiency. Under external magnetic actuation strategies, they are capable of achieving elaborate manipulation and navigation in extreme biomedical environments. This review focuses on state-of-the-art progresses in design strategies, fabrication techniques and applications of magnetically actuated micro/nanorobots. Firstly, recent advances of various robot designs, including helical robots, surface walkers, ciliary robots, scaffold robots and biohybrid robots, are discussed separately. Secondly, the main progresses of common fabrication techniques are respectively introduced, and application achievements on these robots in targeted drug delivery, minimally invasive surgery and cell manipulation are also presented. Finally, a short summary is made, and the current challenges and future work for magnetically actuated micro/nanorobots are discussed.

Biointeraction of Erythrocyte Ghost Membranes with Gold Nanoparticles Fluorescents

The application of new technologies for treatments against different diseases is increasingly innovative and effective. In the case of nanomedicine, the combination of nanoparticles with biological membranes consists of a “camouflage” technique, which improves biological interaction and minimizes the secondary effects caused by these remedies. In this work, gold nanoparticles synthesized by chemical reduction (Turkevich ≈13 nm) were conjugated with fluorescein isothiocyanate to amplify their optical properties. Fluorescent nanoparticles were deposited onto the surface of hemoglobin-free erythrocytes. Ghost erythrocytes were obtained from red blood cells by density gradient separation in a hypotonic medium and characterized with fluorescence, optical, and electron microscopy; the average size of erythrocyte ghosts was 9 µm. Results show that the functional groups of sodium citrate (COO-) and fluorophore (-N=C=S) adhere by electrostatic attraction to the surface of the hemoglobin-free erythrocyte membrane, forming the membrane–particle–fluorophore. These interactions can contribute to imaging applications, by increasing the sensitivity of measurement caused by surface plasmon resonance and fluorescence, in the context of biological membranes.

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.

Biomimetic recombinant of red blood cell membranes for improved photothermal therapy

Background

RBC membrane derived nanoparticles (NPs) represent an emerging platform with prolonged circulation capacity for the delivery of active substances. For functionalize derived RBCs NPs, various strategies, such as biomimetic rebuilding of RBCs, chemical modification or inserting ligands, have been carried out to improve their performance. However, one potential adverse effect for these methods is the structural failure of membrane proteins, consequently affecting its original immune escape function.

Results

In this study, we reported a green technology of “disassembly-reassembly” to prepare biomimetic reconstituted RBCs membrane (rRBCs) by separating the endogenous proteins and lipids from nature RBC membrane. IR780 iodide was used as a pattern drug to verify the property and feasibility of rRBCs by constructing IR780@rRBC NPs with IR780@RBC NPs and free IR780 as controls. The results demonstrated the superiority of IR780@rRBC NPs in toxicity, stability, pharmacokinetics and pharmacodynamics compared with IR780@rRBC and free IR780.

Conclusions

The reported “disassembly-reassembly” strategy shows great potential to produce controllable and versatile rRBC membrane-inspired delivery platform, which may be used to overcome the deficiency of functionalization in cell membrane coated nanoparticles .

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00949-7.

Fabrication of monodisperse alginate microgel beads by microfluidic picoinjection: a chelate free approach

Micron-sized alginate hydrogel beads are extensively employed as an encapsulation medium for biochemical and biomedical applications. Here we report on the microfluidic assisted fabrication of calcium alginate (Ca-alginate) beads by on-chip picoinjection of aqueous calcium chloride (CaCl2) in emulsified aqueous sodium alginate (Na-alginate) droplets or by picoinjection of Na-alginate solution in emulsified aqueous CaCl2 droplets. There is no added chelator to reduce the Ca activity in either of the two strategies. The two fabrication strategies are implemented using a flow-focusing and picoinjection modules in a single PDMS chip. Aqueous alginate solution was emulsified and infused with CaCl2 solution as the squeezed droplet pass the picoinjection channel; consequently, monodisperse, spherical, and structurally homogeneous Ca-alginate beads were obtained. Monodisperse alginate microgel populations with a mean diameter in the range of 8 to 28 μm and standard deviation less than 1 μm were successfully generated using microfluidic channels with various dimensions and controlling the flow parameters. Monodisperse but also non-spherical particles with diameters 6 to 15 μm were also fabricated when picoinjecting Na-alginate solution in emulsified aqueous CaCl2 droplets. The Ca-alginate microbeads fabricated with tailormade size in the range from sub-cellular and upwards were in both strategies realized without any use of chelators or change in pH conditions, which is considered a significant advantage for further exploitation as encapsulation process for improved enzymatic activity and cell viability.

The Fate of Nanoparticles In Vivo and the Strategy of Designing Stealth Nanoparticle for Drug Delivery

Nano-drug delivery systems (Nano-DDS) offer powerful advantages in drug delivery and targeted therapy for diseases. Compared to the traditional drug formulations, Nano-DDS can increase solubility, biocompatibility, and reduce off-targeted side effects of free drugs. However, they still have some disadvantages that pose a limitation in reaching their full potential in clinical use. Protein adsorption in blood, activation of the complement system, and subsequent sequestration by the mononuclear phagocyte system (MPS) consequently result in nanoparticles (NPs) to be rapidly cleared from circulation. Therefore, NPs have low drug delivery efficiency. So, it is important to develop stealth NPs for reducing bio-nano interaction. In this review, we first conclude the interaction between NPs and biological environments, such as blood proteins and MPS, and factors influencing each other. Next, we will summarize the new strategies to reduce NPs protein adsorption and uptake by the MPS based on current knowledge of the bio-nano interaction. Further directions will also be highlighted for the development of biomimetic stealth nano-delivery systems by combining targeted strategies for a better therapeutic effect.

Bioinspired Cell Silicification: From Extracellular to Intracellular

In nature, biosilicification directs the formation of elaborate amorphous silica exoskeletons that provide diatoms mechanically strong, chemically inert, non-decomposable silica armor conferring chemical and thermal stability as well as resistance to microbial attack, without changing the optical transparency or adversely effecting nutrient and waste exchange required for growth. These extraordinary silica/cell biocomposites have inspired decades of biomimetic research aimed at replication of diatoms' hierarchically organized exoskeletons, immobilization of cells or living organisms within silica matrices and coatings to protect them against harmful external stresses, genetic re-programming of cellular functions by virtue of physico-chemical confinement within silica, cellular integration into devices, and endowment of cells with non-native, abiotic properties through facile silica functionalization. In this Perspective, we focus our discussions on the development and concomitant challenges of bioinspired cell silicification ranging from "cells encapsulated within 3D silica matrices" and "cells encapsulated within 2D silica shells" to extra- and intracellular silica replication, wherein all biomolecular interfaces are encased within nanoscopic layers of amorphous silica. We highlight notable examples of advances in the science and technology of biosilicification and consider challenges to advancing the field, where we propose cellular "mineralization" with arbitrary nanoparticle exoskeletons as a generalizable means to impart limitless abiotic properties and functions to cells, and, based on the interchangeability of water and silicic acid and analogies between amorphous ice and amorphous silica, we consider "freezing" cells within amorphous silica as an alternative to cryo-preservation.

State-of-the-art methods for the treatment of severe hemorrhagic trauma: selective aortic arch perfusion and emergency preservation and resuscitation-what is next?

Trauma is a primary cause of death globally, with non‐compressible torso hemorrhage constituting an important part of “potentially survivable trauma death.” Resuscitative endovascular balloon occlusion of the aorta has become a popular alternative to aortic cross‐clamping under emergent thoracotomy for non‐compressible torso hemorrhage in recent years, however, it alone does not improve the survival rate of patients with severe shock or traumatic cardiac arrest from non‐compressible torso hemorrhage. Development of novel advanced maneuvers is essential to improve these patients’ survival, and research on promising methods such as selective aortic arch perfusion and emergency preservation and resuscitation is ongoing. This review aimed to provide physicians in charge of severe trauma cases with a broad understanding of these novel therapeutic approaches to manage patients with severe hemorrhagic trauma, which may allow them to develop lifesaving strategies for exsanguinating trauma patients. Although there are still hurdles to overcome before their clinical application, promising research on these novel strategies is in progress, and ongoing development of synthetic red blood cells and techniques that reduce ischemia‐reperfusion injury may further maximize their effects. Both continuous proof‐of‐concept studies and translational clinical evaluations are necessary to clinically apply these hemostasis approaches to trauma patients.

Advances in siRNA delivery strategies for the treatment of MDR cancer

RNA interference (RNAi) represents a promising therapeutic method that uses siRNA for cancer treatment. Although the RNAi technique has been increasingly used for clinical trials, systemic siRNA delivery into targeted cells is still challenging. The barriers impeding siRNA therapeutics delivery and impacting the treatment outcome must overcome with negligible systemic toxicity for a desirable and successful delivery of siRNA to MDR cancer cells. Nano delivery strategies have been investigated for nanocarrier functionalization, cancer immunotherapy and cancer targeting. Lipid nanoparticles (LNPs), dynamic polyconjugates (DPC™), GalNAc-siRNA conjugates, exosome and RBC systems have shown potential for efficient delivery of siRNA to cancer cells. Delivery of siRNA to tumor cells, immune cells to regulate T cell functions for immunotherapy are promising approaches.

Recent Progress in Magnetically Actuated Microrobots for Targeted Delivery of Therapeutic Agents

Therapeutic agents, such as drugs and cells, play an essential role in virtually every treatment of injury, illness, or disease. However, the conventional practices of drug delivery often result in undesirable side effects caused by drug overdose and off-target delivery. In the case of cell delivery, the survival rate of the transplanted cells is extremely low and difficulties with the administration route of cells remain a problem. Recently, magnetically actuated microrobots have started offering unique opportunities in targeted therapeutic delivery due to their tiny size and ability to access hard-to-reach lesions in a minimally invasive manner; considerable advances in this regard have been made over the past decade. Here, recent progress in magnetically actuated microrobots, developed for targeted drug/cell delivery, is presented, with a focus on their design features and mechanisms for controlled therapeutic release. Additionally, the practical challenges faced by the microrobots, and future research directions toward the swift bench-to-bedside translation of the microrobots are addressed.

Synthesis of Polyhedral Metal-Organic Framework@Mesoporous Silica Hybrid Nanocomposites with Branched Shapes

The structural modulation of multicompartment porous nanomaterials is one of the major challenges of nanoscience. Herein, by utilizing the polyhedral effects/characteristics of metal-organic frameworks (MOFs), we present a versatile approach to construct MOF-organosilica hybrid branched nanocomposites with MOF cores, SiO₂ shells, and periodic mesoporous organosilica (PMO) branches. The morphology, structure, and functions of the obtained hybrid nanocomposites can be facilely modulated by varying particle size, shape, or crystalline structures of the MOF cores. Specifically, these branched multicompartment porous nanoparticles exhibit evasion behaviors in epithelial cells compared with macrophage cells, which may endow them great potential as a vehicle for immunotherapy.

Detection of Viruses and Virus-Neutralizing Antibodies Using Synthetic Erythrocytes: Toward a Tuneable Tool for Virus Surveillance

The hemagglutination inhibition assay (HAI) is a classical method used worldwide in many analytical applications, including pathogen identification, vaccine production monitoring, and detection and characterization of pathogen-neutralizing antibodies (n-Ab). This is also a World Health Organization (WHO) reference method for the global surveillance of influenza viruses, which provides the information needed for the annual reformulation of the flu vaccine. HAI is a simple and inexpensive method that is performed without sophisticated equipment. However, it has to be carried out with fresh red blood cells (RBCs), a highly variable, unstable, and hard to mass-produce reagent, which impairs assay reproducibility. Here, we used the tests employed for influenza surveillance as a model to develop synthrocytes^©, a synthetic reagent that could substitute animal erythrocytes in HAI. Contrary to previous examples exploiting sophisticated production paths to generate therapeutic synthetic RBCs, we founded production on the identification of microparticles able to generate different sedimentation patterns when agglutinated or not, which is the main requirement for HAI testing. Upon incorporation of influenza-binding receptors and optimization of production and assay conditions, synthrocytes succeeded in binding influenza A(H1N1) and B viruses as erythrocytes do, but were faster and more stable. Synthrocytes were finally employed in an HAI-like assay to detect the WHO reference reagents for influenza surveillance. Our results show that it is possible to substitute erythrocytes in classical HAI by a highly tuneable and potentially mass-produced synthetic reagent, which should facilitate worldwide HAI standardization with minimal equipment or training requirements.

Biological Cells as Therapeutic Delivery Vehicles

One of the significant challenges remaining in the field of drug delivery is insufficient targeting of diseased tissues or cells. While efforts to perform targeted drug delivery by engineered nanoparticles have shown some success, there are underlying targeting, toxicity, and immunogenicity challenges. By contrast, live cells usually have innate targeting mechanisms, and can be used as drug-delivery vehicles to increase the efficiency with which a drug accumulates to act on the intended tissue. In some cases, when no native cell types exhibit the desired therapeutic phenotype, preferred outcomes can be achieved by genetically modifying and reprogramming cells with gene circuits. This review highlights recent advances in the use of cells to deliver therapeutics. Specifically, we discuss how red blood cells (RBCs), platelets, neutrophils, mesenchymal stem cells (MSCs), and bacteria have been utilized to advance drug delivery.

Künstliche Sauerstofftransporter können mehr als Sauerstoff liefern

Zum gegenwärtigen Zeitpunkt ist in der EU und den USA kein artifizieller Sauerstofftransporter zugelassen. Hämoglobin-basierte Sauerstoff-Carrier (HBOC) sind bereits seit Jahrzehnten Gegenstand wissenschaftlicher Untersuchungen. Ein wesentliches Hindernis bei der Zulassung war bisher der Anspruch der Entwickler, einen universell einsetzbaren Blutersatz zu produzieren. Die Beschränkung auf eine Indikation scheint erfolgversprechender zu sein. Der Ansatz, nicht nur Sauerstoff von der Lunge zum Gewebe, sondern auch der Abtransport von Kohlendioxid vom Gewebe zur Lunge zu transportieren, der effektiver als mit Erythrozyten durchgeführt werden kann, erscheint besonders attraktiv. Aufgrund vielversprechender präklinischer sowie klinischer Untersuchungen besteht die Hoffnung, dass in absehbarer Zeit auch in der EU künstliche Sauerstofftransporter für therapeutische Zwecke zur Verfügung stehen werden.