Biological Cells as Therapeutic Delivery Vehicles

Macrophage based drug delivery: Key challenges and strategies

As a natural immune cell and antigen presenting cell, macrophages have been studied and engineered to treat human diseases. Macrophages are well-suited for use as drug carriers because of their biological characteristics, such as excellent biocompatibility, long circulation, intrinsic inflammatory homing and phagocytosis. Meanwhile, macrophages' uniquely high plasticity and easy re-education polarization facilitates their use as part of efficacious therapeutics for the treatment of inflammatory diseases or tumors. Although recent studies have demonstrated promising advances in macrophage-based drug delivery, several challenges currently hinder further improvement of therapeutic effect and clinical application. This article focuses on the main challenges of utilizing macrophage-based drug delivery, from the selection of macrophage sources, drug loading, and maintenance of macrophage phenotypes, to drug migration and release at target sites. In addition, corresponding strategies and insights related to these challenges are described. Finally, we also provide perspective on shortcomings on the road to clinical translation and production.

Immune Cell-Based Microrobots for Remote Magnetic Actuation, Antitumor Activity, and Medical Imaging

Translating medical microrobots into clinics requires tracking, localization, and performing assigned medical tasks at target locations, which can only happen when appropriate design, actuation mechanisms, and medical imaging systems are integrated into a single microrobot. Despite this, these parameters are not fully considered when designing macrophage-based microrobots. This study presents living macrophage-based microrobots that combine macrophages with magnetic Janus particles coated with FePt nanofilm for magnetic steering and medical imaging and bacterial lipopolysaccharides for stimulating macrophages in a tumor-killing state. The macrophage-based microrobots combine wireless magnetic actuation, tracking with medical imaging techniques, and antitumor abilities. These microrobots are imaged under magnetic resonance imaging and optoacoustic imaging in soft-tissue-mimicking phantoms and ex vivo conditions. Magnetic actuation and real-time imaging of microrobots are demonstrated under static and physiologically relevant flow conditions using optoacoustic imaging. Further, macrophage-based microrobots are magnetically steered toward urinary bladder tumor spheroids and imaged with a handheld optoacoustic device, where the microrobots significantly reduce the viability of tumor spheroids. The proposed approach demonstrates the proof-of-concept feasibility of integrating macrophage-based microrobots into clinic imaging modalities for cancer targeting and intervention, and can also be implemented for various other medical applications.

Bio-inspired drug delivery systems: A new attempt from bioinspiration to biomedical applications

Natural organisms have evolved sophisticated and multiscale hierarchical structures over time to enable survival. Currently, bionic design is revolutionizing drug delivery systems (DDS), drawing inspiration from the structure and properties of natural organisms that offer new possibilities to overcome the challenges of traditional drug delivery systems. Bionic drug delivery has contributed to a significant improvement in therapeutic outcomes, providing personalized regimens for patients with various diseases and enhancing both their quality of life and drug efficacy. Therefore, it is important to summarize the progress made so far and to discuss the challenges and opportunities for future development. Herein, we review the recent advances in bio-inspired materials, bio-inspired drug vehicles, and drug-loading platforms of biomimetic structures and properties, emphasizing the importance of adapting the structure and function of organisms to meet the needs of drug delivery systems. Finally, we highlight the delivery strategies of bionics in DDS to provide new perspectives and insights into the research and exploration of bionics in DDS. Hopefully, this review will provide future insights into utilizing biologically active vehicles, bio-structures, and bio-functions, leading to better clinical outcomes.

Advancing in vivo reprogramming with synthetic biology

Reprogramming cells will play a fundamental role in shaping the future of cell therapies by developing new strategies to engineer cells for improved performance and higher-order physiological functions. Approaches in synthetic biology harness cells' natural ability to sense diverse signals, integrate environmental inputs to make decisions, and execute complex behaviors based on the health of the organism or tissue. In this review, we highlight strategies in synthetic biology to reprogram cells, and discuss how recent approaches in the delivery of modified mRNA have created new opportunities to alter cell function in vivo. Finally, we discuss how combining concepts from synthetic biology and the delivery of mRNA in vivo could provide a platform for innovation to advance in vivo cellular reprogramming.

Covalent Organic Frameworks: Opportunities for Rational Materials Design in Cancer Therapy

Nanomedicines are extensively used in cancer therapy. Covalent organic frameworks (COFs) are crystalline organic porous materials with several benefits for cancer therapy, including porosity, design flexibility, functionalizability, and biocompatibility. This review examines the use of COFs in cancer therapy from the perspective of reticular chemistry and function-oriented materials design. First, the modification sites and functionalization methods of COFs are discussed, followed by their potential as multifunctional nanoplatforms for tumor targeting, imaging, and therapy by integrating functional components. Finally, some challenges in the clinical translation of COFs are presented with the hope of promoting the development of COF-based anticancer nanomedicines and bringing COFs closer to clinical trials.

Review of electrospun microtube array membrane (MTAM)-a novel new class of hollow fiber for encapsulated cell therapy (ECT) in clinical applications

Encapsulated cell therapy (ECT) shows significant potential for treating neurodegenerative disorders including Alzheimer's and Parkinson's, which currently lack curative medicines and must be managed symptomatically. This novel technique encapsulates functional cells with a semi-permeable membrane, providing protection while enabling critical nutrients and therapeutic substances to pass through. Traditional ECT procedures, on the other hand, pose difficulties in terms of cell survival and retrieval. We introduce the Microtube Array Membrane (MTAM), a revolutionary technology that solves these constraints, in this comprehensive overview. Microtube Array Membrane has distinct microstructures that improve encapsulated cells' long-term viability by combining the advantages of macro and micron scales. Importantly, the MTAM platform improves biosafety by allowing the entire encapsulated unit to be retrieved in the event of an adverse reaction. Our findings show that MTAM-based ECT has a great potential in a variety of illness situations. For cancer treatment, hybridoma cells secreting anti-CEACAM 6 antibodies inhibit triple-negative breast cancer cell lines for an extended period of time. In animal brain models of Alzheimer's disease, hybridoma cells secreting anti-pTau antibodies successfully reduce pTau buildup, accompanied by improvements in memory performance. In mouse models, MTAM-encapsulated primary cardiac mesenchymal stem cells dramatically improve overall survival and heart function. These findings illustrate the efficacy and adaptability of MTAM-based ECT in addressing major issues such as immunological isolation, cell viability, and patient safety. We provide new possibilities for the treatment of neurodegenerative illnesses and other conditions by combining the potential of ECT with MTAM. Continued research and development in this subject has a lot of promise for developing cell therapy and giving hope to people suffering from chronic diseases.

Genetically engineered mesenchymal stem cells as a nitric oxide reservoir for acute kidney injury therapy

Nitric oxide (NO), as a gaseous therapeutic agent, shows great potential for the treatment of many kinds of diseases. Although various NO delivery systems have emerged, the immunogenicity and long-term toxicity of artificial carriers hinder the potential clinical translation of these gas therapeutics. Mesenchymal stem cells (MSCs), with the capacities of self-renewal, differentiation, and low immunogenicity, have been used as living carriers. However, MSCs as gaseous signaling molecule (GSM) carriers have not been reported. In this study, human MSCs were genetically modified to produce mutant β-galactosidase (β-GALH363A). Furthermore, a new NO prodrug, 6-methyl-galactose-benzyl-oxy NONOate (MGP), was designed. MGP can enter cells and selectively trigger NO release from genetically engineered MSCs (eMSCs) in the presence of β-GALH363A. Moreover, our results revealed that eMSCs can release NO when MGP is systemically administered in a mouse model of acute kidney injury (AKI), which can achieve NO release in a precise spatiotemporal manner and augment the therapeutic efficiency of MSCs. This eMSC and NO prodrug system provides a unique and tunable platform for GSM delivery and holds promise for regenerative therapy by enhancing the therapeutic efficiency of stem cells.

Evolution of molecular switches for regulation of transgene expression by clinically licensed gluconate

Synthetic biology holds great promise to improve the safety and efficacy of future gene and engineered cell therapies by providing new means of endogenous or exogenous control of the embedded therapeutic programs. Here, we focused on gluconate as a clinically licensed small-molecule inducer and engineered gluconate-sensitive molecular switches to regulate transgene expression in human cell cultures and in mice. Several switch designs were assembled based on the gluconate-responsive transcriptional repressor GntR from Escherichia coli. Initially we assembled OFF- and ON-type switches by rewiring the native gluconate-dependent binding of GntR to target DNA sequences in mammalian cells. Then, we utilized the ability of GntR to dimerize in the presence of gluconate to activate gene expression from a split transcriptional activator. By means of random mutagenesis of GntR combined with phenotypic screening, we identified variants that significantly enhanced the functionality of the genetic devices, enabling the construction of robust two-input logic gates. We also demonstrated the potential utility of the synthetic switch in two in vivo settings, one employing implantation of alginate-encapsulated engineered cells and the other involving modification of host cells by DNA delivery. Then, as proof-of-concept, the gluconate-actuated genetic switch was connected to insulin secretion, and the components encoding gluconate-induced insulin production were introduced into type-1 diabetic mice as naked DNA via hydrodynamic tail vein injection. Normoglycemia was restored, thereby showcasing the suitability of oral gluconate to regulate in situ production of a therapeutic protein.

Cellular Drug Delivery System for Disease Treatment

The application of variable novel drug delivery system has shown a flowering trend in recent years. Among them, the cell-based drug delivery system (DDS) utilizes the unique physiological function of cells to deliver drugs to the lesion area, which is the most complex and intelligent DDS at present. Compared with the traditional DDS, the cell-based DDS has the potential of prolonged circulation in body. Cellular DDS is expected to be the best carrier to realize multifunctional drug delivery. This paper introduces and analyzes common cellular DDSs such as blood cells, immune cells, stem cells, tumor cells and bacteria as well as relevant research examples in recent years. We hope that this review can provide a reference for future research on cell vectors and promote the innovative development and clinical transformation of cell-based DDS.

Living Leukocyte-Based Drug Delivery Systems

Leukocytes play a vital role in immune responses, including defending against invasive pathogens, reconstructing impaired tissue, and maintaining immune homeostasis. When the immune system is activated in vivo, leukocytes accomplish a series of orderly and complex regulatory processes. While cancer and inflammation-related diseases like sepsis are critical medical difficulties plaguing humankind around the world, leukocytes have been shown to largely gather at the focal site, and significantly contribute to inflammation and cancer progression. Therefore, the living leukocyte-based drug delivery systems have attracted considerable attention in recent years due to the innate and specific targeting effect, low immunogenicity, improved therapeutic efficacy, and low reverse effect. In this review, the recent advances in the development of living leukocyte-based drug delivery systems including macrophages, neutrophils, and lymphocytes as promising treatment strategies for cancer and inflammation-related diseases are introduced. The advantages, current challenges, and limitations of these delivery systems are also discussed, as well as perspectives on the future development of precision and targeted therapy in the clinics are provided. Collectively, it is expected that such kind of living cell-based drug delivery system is promising to improve or even revolutionize the treatments of cancers and inflammation-related diseases in the clinics.

Proteomes of Micro- and Nanosized Carriers Engineered from Red Blood Cells

Red blood cell (RBC)-derived systems offer a potential platform for delivery of biomedical cargos. Although the importance of specific proteins associated with the biodistribution and pharmacokinetics of these particles has been recognized, it remains to be explored whether some of the key transmembrane and cytoskeletal proteins responsible for immune-modulatory effects and mechanical integrity of the particles are retained. Herein, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and quantitative tandem mass tag mass spectrometry in conjunction with bioinformatics analysis, we have examined the proteomes of micro- and nanosized erythrocyte ghosts doped with indocyanine green and compared them with those of RBCs. We identified a total of 884 proteins in each set of RBCs, micro-, and nanosized particles, of which 8 and 45 proteins were expressed at significantly different relative abundances when comparing micro-sized particles vs RBCs and nanosized particles vs RBCs, respectively. We found greater differences in relative abundances of some mechano-modulatory proteins, such as band 3 and protein 4.2, and immunomodulatory proteins like CD44, CD47, and CD55 in nanosized particles as compared to RBCs. Our findings highlight that the methods utilized in fabricating RBC-based systems can induce substantial effects on their proteomes. Mass spectrometry data are available at ProteomeXchange with the identifier PXD038780.

Exosomes-Based Nanomedicine for Neurodegenerative Diseases: Current Insights and Future Challenges

Neurodegenerative diseases constitute a group of pathologies whose etiology remains unknown in many cases, and there are no treatments that stop the progression of such diseases. Moreover, the existence of the blood-brain barrier is an impediment to the penetration of exogenous molecules, including those found in many drugs. Exosomes are extracellular vesicles secreted by a wide variety of cells, and their primary functions include intercellular communication, immune responses, human reproduction, and synaptic plasticity. Due to their natural origin and molecular similarities with most cell types, exosomes have emerged as promising therapeutic tools for numerous diseases. Specifically, neurodegenerative diseases have shown to be a potential target for this nanomedicine strategy due to the difficult access to the brain and the strategy's pathophysiological complexity. In this regard, this review explores the most important biological-origin drug delivery systems, innovative isolation methods of exosomes, their physicochemical characterization, drug loading, cutting-edge functionalization strategies to target them within the brain, the latest research studies in neurodegenerative diseases, and the future challenges of exosomes as nanomedicine-based therapeutic tools.

Layer-by-layer development of chitosan/alginate-based platelet-mimicking nanocapsules for augmenting doxorubicin cytotoxicity against breast cancer

Breast carcinoma is considered one of the most invasive and life-threatening malignancies in females. Mastectomy, radiation therapy, hormone therapy and chemotherapy are the most common treatment choices for breast cancer. Doxorubicin (DOX) is one of the most regularly utilized medications in breast cancer protocols. However, DOX has showed numerous side effects including lethal cardiotoxicity. This study aims to fortify DOX cytotoxicity and lowering its side effects via its combining with the antidiabetic metformin (MET) as an adjuvant therapy, along with its effective delivery using natural platelet-rich plasma (PRP), and newly-developed PRP-mimicking nanocapsules (NCs). The PRP-mimicking NCs were fabricated via layer-by-layer (LBL) deposition of oppositely charged biodegradable and biocompatible chitosan (CS) and alginate (ALG) on a core of synthesized polystyrene nanoparticles (PS NPs) followed by removal of the PS core. Both natural PRP and PRP-mimicking NCs were loaded with DOX and MET adjuvant therapy, followed by their physicochemical characterizations including DLS, FTIR, DSC, and morphological evaluation using TEM. In-vitro drug release studies, cytotoxicity, apoptosis/necrosis, and cell cycle analysis were conducted using MCF-7 breast cancer cells. Also, an in-vivo assessment was carried out using EAC-bearing balb/c mice animal model to evaluate the effect of DOX/MET-loaded natural PRP and PRP-mimicked NCs on tumor weight, volume and growth biomarkers in addition to analyzing the immunohistopathology of the treated tissues. Results confirmed the development of CS/ALG-based PRP-mimicking NCs with a higher loading capacity of both drugs (DOX and MET) and smaller size (259.7 ± 19.3 nm) than natural PRP (489 ± 20.827 nm). Both in-vitro and in-vivo studies were in agreement and confirmed that MET synergized the anticancer activity of DOX against breast cancer. Besides, the developed LBL NCs successfully mimicked the PRP in improving the loaded drugs biological efficiency more than free drugs.

Red blood cell-based vaccines for ameliorating cancer chemoimmunotherapy

Immune checkpoint blockade (ICB) therapy has shown promising antitumor effects, but its immune response rate remains unsatisfactory. In recent years, chemotherapy has been proven to have synergistic effects with ICB therapy because some chemotherapeutic agents can enhance the immunogenicity of tumor cells by inducing immunogenic cell death (ICD). However, it cannot be ignored that chemotherapy often shows limited therapeutic efficacy due to high cytotoxicity, drug resistance, and some other side effects. Herein, we report a strategy to improve cancer immunotherapy by utilizing red blood cell-based vaccines (RBC-vaccines) where chemotherapy-induced tumor antigens (cAgs) are anchored onto red blood cells (RBCs) via the EDC/NHS-mediated amine coupling reaction. In this work, RBC-vaccines administered subcutaneously are primarily devoured by dendritic cells (DCs) and significantly improve the efficacy of αPD-1 (anti-programmed cell death 1) treatment by increasing the infiltration of intratumoral CD8⁺ and CD4⁺ T cells and elevating the intratumoral ratio of CD8⁺ T cells to regulatory T cells in the CT-26 colon cancer model. Finally, based on the rejection of tumor rechallenge in cured mice, the combination therapy of RBC-vaccines and αPD-1 can induce the expansion of memory T cells and thereby establish a long-term antitumor immune response. Taken together, the proposed RBC-vaccines have great potential to improve chemoimmunotherapy. STATEMENT OF SIGNIFICANCE: Immunotherapy, especially immune checkpoint blockade therapy, has made great contributions to the treatment of some advanced cancers. Unfortunately, the great majority of patients with cancer do not benefit from immunotherapy. To enhance the response rate of immunotherapy, we developed red blood cell-based vaccines (RBC-vaccines) against cancers where antigens were harvested from chemotherapy-treated cancer cells and then attached to erythrocytes via covalent surface modification. Such RBC-vaccines could provide a wide variety of tumor antigens and damage-associated molecular patterns without the use of any extra ingredients to trigger a stronger antitumor immune response. More importantly, the combination of RBC-vaccines with PD-1 blockade could significantly improve the efficacy of cancer immunotherapy and induce durable antitumor immunity.

Platelet-promoting drug delivery efficiency for inhibition of tumor growth, metastasis, and recurrence

Nanomedicines are considered one of the promising strategies for anticancer therapy; however, the low targeting efficiency of nanomedicines in vivo is a great obstacle to their clinical applications. Camouflaging nanomedicines with either platelet membrane (PM) or platelet would significantly prolong the retention time of nanomedicines in the bloodstream, enhance the targeting ability of nanomedicines to tumor cells, and reduce the off-target effect of nanomedicines in major organs during the anticancer treatment. In the current review, the advantages of using PM or platelet as smart carriers for delivering nanomedicines to inhibit tumor growth, metastasis, and recurrence were summarized. The opportunities and challenges of this camouflaging strategy for anticancer treatment were also discussed.

Nanodelivery of cGAS-STING activators for tumor immunotherapy

Activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway has great potential to promote antitumor immunity. Development of activators for the cGAS-STING pathway (cGAS-STING activators) has profoundly revolutionized tumor immunotherapy. However, successful clinical application of cGAS-STING activators is contingent on having appropriate systems to achieve safe, effective, and specific delivery. There is an increasing emphasis on the design and application of nano drug delivery systems (NDDS) that can facilitate the delivery potential of cGAS-STING activators. In this review, we discuss barriers for translational development of cGAS-STING activators (DNA damaging drugs and STING agonists) and recent advances of NDDS for these agents in tumor immunotherapy.

Probing cell membrane integrity using a histone-targeting protein nanocage displaying precisely positioned fluorophores

Cell membrane integrity is fundamental to the normal activities of cells and is involved in both acute and chronic pathologies. Here, we report a probe for analyzing cell membrane integrity developed from a 9 nm-sized protein nanocage named Dps via fluorophore conjugation with high spatial precision to avoid self-quenching. The probe cannot enter normal live cells but can accumulate in dead or live cells with damaged membranes, which, interestingly, leads to weak cytoplasmic and strong nuclear staining. This differential staining is found attributed to the high affinity of Dps for histones rather than DNA, providing a staining mechanism different from those of known membrane exclusion probes (MEPs). Moreover, the Dps nanoprobe is larger in size and thus applies a more stringent criterion for identifying severe membrane damage than currently available MEPs. This study shows the potential of Dps as a new bioimaging platform for biological and medical analyses.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (Figs. S1-S12 including distance information between neighboring fluorophores on Dps, TEM images, MALDI-TOF analysis, fluorescence spectra, confocal images, gel retardation analysis, tissue staining, and additional data) is available in the online version of this article at 10.1007/s12274-022-4785-5.

Red Blood Cell Inspired Strategies for Drug Delivery: Emerging Concepts and New Advances

In the past five decades, red blood cells (RBCs) have been extensively explored as drug delivery systems due to their distinguishing potential in modulating the pharmacokinetic, pharmacodynamics, and biological activity of carried payloads. The extensive interests in RBC-mediated drug delivery technologies are in part derived from RBCs' unique biological features such as long circulation time, wide access to many tissues in the body, and low immunogenicity. Owing to these outstanding properties, a large body of efforts have led to the development of various RBC-inspired strategies to enable precise drug delivery with enhanced therapeutic efficacy and reduced off-target toxicity. In this review, we discuss emerging concepts and new advances in such RBC-inspired strategies, including native RBCs, ghost RBCs, RBC-mimetic nanoparticles, and RBC-derived extracellular vesicles, for drug delivery.

COVID-19 inflammation and implications in drug delivery

Growing evidence indicates that hyperinflammatory syndrome and cytokine storm observed in COVID-19 severe cases are narrowly associated with the disease's poor prognosis. Therefore, targeting the inflammatory pathways seems to be a rational therapeutic strategy against COVID-19. Many anti-inflammatory agents have been proposed; however, most of them suffer from poor bioavailability, instability, short half-life, and undesirable biodistribution resulting in off-target effects. From a pharmaceutical standpoint, the implication of COVID-19 inflammation can be exploited as a therapeutic target and/or a targeting strategy against the pandemic. First, the drug delivery systems can be harnessed to improve the properties of anti-inflammatory agents and deliver them safely and efficiently to their therapeutic targets. Second, the drug carriers can be tailored to develop smart delivery systems able to respond to the microenvironmental stimuli to release the anti-COVID-19 therapeutics in a selective and specific manner. More interestingly, some biosystems can simultaneously repress the hyperinflammation due to their inherent anti-inflammatory potency and endow their drug cargo with a selective delivery to the injured sites.

A Platelet Intelligent Vehicle with Navigation for Cancer Photothermal-Chemotherapy

Controllable and visible delivery of therapeutic agents is critical for tumor precise therapy. Tumor targeting and deep penetration of therapeutic agents are still challenging issues for controllable delivery. Visible drug delivery with imaging navigation can optimize the treatment window for personalized medicine. Herein, a biomimetic platelet intelligent vehicle with navigation (IRDNP-PLT) was developed to achieve controllable and visible delivery with a navigation system, a driving system, and a loading system. The platelets acted as engines and drug repositories to exert the target driving and delivery functions. The fluorescent photothermal agent IR-820 was introduced in the platform to offer an imaging navigation for the intelligent platelet vehicle in addition to photothermal therapy. The nanodrug-loaded platelets enabled efficient drug loading and controlled release of the therapeutic payload by encapsulating photothermal-/pH-sensitive chemotherapeutic nanoparticles (PDA@Dox NPs). In in vivo experiments on 4T1 tumor-bearing mice models, IRDNP-PLT performed well in tumor targeting and showed excellent therapeutic efficacy and tumor recurrence prevention ability. The intelligent platelet vehicle achieved the functions of tumor targeting and deep penetration, fluorescence imaging guidance, photocontrolled drug release, and chemo-photothermal combination therapy, suggesting the advancement for tumor precise delivery and efficient therapy.

Cell-derived membrane biomimetic nanocarriers for targeted therapy of pulmonary disease

Pulmonary diseases are currently one of the major threats of human health, especially considering the recent COVID-19 pandemic. However, the current treatments are facing the challenges like insufficient local drug concentrations, the fast lung clearance and risks to induce unexpected inflammation. Cell-derived membrane biomimetic nanocarriers are recently emerged delivery strategy, showing advantages of long circulation time, excellent biocompatibility and immune escape ability. In this review, applications of using cell-derived membrane biomimetic nanocarriers from diverse cell sources for the targeted therapy of pulmonary disease were summarized. In addition, improvements of the cell-derived membrane biomimetic nanocarriers for augmented therapeutic ability against different kinds of pulmonary diseases were introduced. This review is expected to provide a general guideline for the potential applications of cell-derived membrane biomimetic nanocarriers to treat pulmonary diseases.

Engineering Bacteria and Bionic Bacterial Derivatives with Nanoparticles for Cancer Therapy

Natural bacteria are interesting subjects for cancer treatments owing to their unique autonomy-driven and hypoxic target properties. Genetically modified bacteria (such as bacteria with msbB gene and aroA gene modifications) can effectively cross sophisticated physiological barriers and transport antitumor agents into deep tumor tissues, and they have good biosafety. Additionally, bacteria can secrete cytokines (such as interleukin-224, interferon-gamma [IFN-γ], and interleukin-1β) and activate antitumor immune responses in the tumor microenvironment, resulting in tumor inhibition. All of these characteristics can be easily utilized to develop synergistic antitumor strategies by combining bacteria-based agents with other therapeutic approaches. Herein, representative studies of bacteria-instructed multimodal synergistic cancer therapy are introduced (e.g., photothermal therapy, chemoimmunotherapy, photodynamic therapy, and photocontrolled bacterial metabolite therapy), and their key advantages are systematically expounded. The current challenges and future prospects in advancing the development of bacteria-based micro/nanomedicines in the field of synthetic biology research are also emphasized, which will hopefully promote the development of related bacteria-based cancer therapies.

Inhibition of miRNA-100 facilitates bone regeneration defects of mesenchymal stem cells in osteoporotic mice through the protein kinase B pathway

Osteoporotic patients suffer from bone microstructure damage and are prone to fracture and bone defect. Due to the damage of bone healing ability, the bone repair of osteoporotic patients is usually slow. Here we aimed to explore the function and potential molecular mechanism of miR-100 in osteogenic differentiation ability of bone marrow stem cells (BMSCs). Ovariectomy was performed on mice to induce osteoporosis. BMSCs were extracted from normal and ovariectomized (OVX) mice to examine the effect of microRNA (miR)-100 on BMSC osteogenic differentiation. Hematoxylin and eosin (H&E) staining and safranin O-fast green staining assays were performed on femur tissues to reveal pathological changes. The osteogenic differentiation of BMSCs were determined by Alkaline Phosphatase and Alizarin red staining assays. The results showed that miR-100 expression was significantly upregulated in bone tissues and BMSCs from osteoporotic mice. MiR-100 knockdown partially improved osteogenic function of OVX mice-derived BMSCs. Next, mechanistic target of rapamycin kinase (MTOR) was identified as the target downstream miR-100. MiR-100 deficiency can activate the protein kinase B (AKT)/mTOR pathway. MiR-100 controlled the osteogenic function of BMSCs by the AKT/mTOR pathway. Collectively, our findings demonstrate that inhibition of miR-100 facilitates bone regeneration defects of BMSCs in osteoporotic mice through AKT pathway, indicating that miR-100 might be an effective target for the treatment of osteoporotic mandibular injury and bone defect diseases.

Nature-inspired dynamic gene-loaded nanoassemblies for the treatment of brain diseases

Gene therapy has great potential to treat brain diseases. However, genetic drugs need to overcome a cascade of barriers for their full potential. The conventional delivery systems often struggle to meet expectations. Natural biological particles that are highly optimized for specific functions in body, can inspire optimization of dynamic gene-loaded nanoassemblies (DGN). The DGN refer to gene loaded nanoassemblies whose functions and structures are changeable in response to the biological microenvironments or can dynamically interact with tissues or cells. The nature-inspired DGN can meet the needs in brain diseases treatment, including i) Non-elimination in blood (N), ii) Across the blood-brain barrier (A), iii) Targeting cells (T), iv) Efficient uptake (U), v) Controllable release (R), vi) Eyeable (E)-abbreviated as the "NATURE". In this Review, from nature to "NATURE", we mainly summarize the specific application of nature-inspired DGN in the "NATURE" cascade process. Furthermore, the Review provides an outlook for this field.

Design and development of engineered receptors for cell and tissue engineering

Advances in synthetic biology have provided genetic tools to reprogram cells to obtain desired cellular functions that include tools to enable the customization of cells to sense an extracellular signal and respond with a desired output. These include a variety of engineered receptors capable of transmembrane signaling that transmit information from outside of the cell to inside when specific ligands bind to them. Recent advances in synthetic receptor engineering have enabled the reprogramming of cell and tissue behavior, controlling cell fate decisions, and providing new vehicles for therapeutic delivery.

Macrophage membrane camouflaged reactive oxygen species responsive nanomedicine for efficiently inhibiting the vascular intimal hyperplasia

BACKGROUND

Intimal hyperplasia caused by vascular injury is an important pathological process of many vascular diseases, especially occlusive vascular disease. In recent years, Nano-drug delivery system has attracted a wide attention as a novel treatment strategy, but there are still some challenges such as high clearance rate and insufficient targeting.

RESULTS

In this study, we report a biomimetic ROS-responsive MM@PCM/RAP nanoparticle coated with macrophage membrane. The macrophage membrane with the innate "homing" capacity can superiorly regulate the recruitment of MM@PCM/RAP to inflammatory lesion to enhance target efficacy, and can also disguise MM@PCM/RAP nanoparticle as the autologous cell to avoid clearance by the immune system. In addition, MM@PCM/RAP can effectively improve the solubility of rapamycin and respond to the high concentration level of ROS accumulated in pathological lesion for controlling local cargo release, thereby increasing drug availability and reducing toxic side effects.

CONCLUSIONS

Our findings validate that the rational design, biomimetic nanoparticles MM@PCM/RAP, can effectively inhibit the pathological process of intimal injury with excellent biocompatibility.

Biomaterials, biological molecules, and polymers in developing vaccines

Vaccines have been used to train the immune system to recognize pathogens, and prevent and treat diseases, such as cancer, for decades. However, there are continuing challenges in their manufacturing, large-scale production, and storage. Some of them also show suboptimal immunogenicity, requiring additional adjuvants and booster doses. As an alternate vaccination strategy, a new class of biomimetic materials with unique functionalities has emerged in recent years. Here, we explore the current bioengineering techniques that make use of hydrogels, modified polymers, cell membranes, self-assembled proteins, virus-like particles (VLPs), and nucleic acids to deliver and develop biomaterial-based vaccines. We also review design principles and key regulatory issues associated with their development. Finally, we critically assess their limitations, explore approaches to overcome these limitations, and discuss potential future applications for clinical translation.

Extracellular Vesicles of Mesenchymal Stem Cells: Therapeutic Properties Discovered with Extraordinary Success

Mesenchymal stem cells (MSCs), the cells distributed in the stromas of the body, are known for various properties including replication, the potential of various differentiations, the immune-related processes including inflammation. About two decades ago, these cells were shown to play relevant roles in the therapy of numerous diseases, dependent on their immune regulation and their release of cytokines and growth factors, with ensuing activation of favorable enzymes and processes. Such discovery induced great increase of their investigation. Soon thereafter, however, it became clear that therapeutic actions of MSCs are risky, accompanied by serious drawbacks and defects. MSC therapy has been therefore reduced to a few diseases, replaced for the others by their extracellular vesicles, the MSC-EVs. The latter vesicles recapitulate most therapeutic actions of MSCs, with equal or even better efficacies and without the serious drawbacks of the parent cells. In addition, MSC-EVs are characterized by many advantages, among which are their heterogeneities dependent on the stromas of origin, the alleviation of cell aging, the regulation of immune responses and inflammation. Here we illustrate the MSC-EV therapeutic effects, largely mediated by specific miRNAs, covering various diseases and pathological processes occurring in the bones, heart and vessels, kidney, and brain. MSC-EVs operate also on the development of cancers and on COVID-19, where they alleviate the organ lesions induced by the virus. Therapy by MSC-EVs can be improved by combination of their innate potential to engineering processes inducing precise targeting and transfer of drugs. The unique properties of MSC-EVs explain their intense studies, carried out with extraordinary success. Although not yet developed to clinical practice, the perspectives for proximal future are encouraging.