Camouflaging bacteria by wrapping with cell membranes

Single-cell encapsulation systems for probiotic delivery: Armor probiotics

Functional foods or drugs based on probiotics have gained unprecedented attention and development due to the increasingly clear relationship between probiotics and human health. Probiotics can regulate intestinal microbiota, dynamically participating in various physiological activities to directly affect human health. Some probiotic-based functional preparations have shown great potential in treating multiple refractory diseases. Currently, the survival and activity of probiotic cells in complex environments in vitro and in vivo have taken priority, and various encapsulation systems based on food-derived materials have been designed and constructed to protect and deliver probiotics. However, traditional encapsulation technology cannot achieve precise protection for a single probiotic, which makes it unable to have a significant effect after release. In this case, single-cell encapsulation systems can be assembled based on biological interfaces to protect and functionalize individual probiotic cells, maximizing their physiological activity. This review discussed the arduous challenges of probiotics in food processing, storage, human digestion, and the commonly used probiotic encapsulation system. Besides, a novel technology of probiotic encapsulation was introduced based on single-cell coating, namely, "armor probiotics". We focused on the classification, structural design, and functional characteristics of armor coatings, and emphasized the essential functional characteristics of armor probiotics in human health regulation, including regulating intestinal health and targeted bioimaging and treatment of diseased tissues. Subsequently, the benefits, limitations, potential challenges, as well as future direction of armor probiotics were put forward. We hope this review may provide new insights and ideas for developing a single-cell probiotics encapsulating system.

Advancements of engineered live oncolytic biotherapeutics (microbe/virus/cells): Preclinical research and clinical progress

The proven efficacy of immunotherapy in fighting tumors has been firmly established, heralding a new era in harnessing both the innate and adaptive immune systems for cancer treatment. Despite its promise, challenges such as inefficient delivery, insufficient tumor penetration, and considerable potential toxicity of immunomodulatory agents have impeded the advancement of immunotherapies. Recent endeavors in the realm of tumor prophylaxis and management have highlighted the use of living biological entities, including bacteria, oncolytic viruses, and immune cells, as a vanguard for an innovative class of live biotherapeutic products (LBPs). These LBPs are gaining recognition for their inherent ability to target tumors. However, these LBPs must contend with significant barriers, including robust immune clearance mechanisms, cytotoxicity and other in vivo adverse effects. Priority must be placed on enhancing their safety and therapeutic indices. This review consolidates the latest preclinical research and clinical progress pertaining to the exploitation of engineered biologics, spanning bacteria, oncolytic viruses, immune cells, and summarizes their integration with combination therapies aimed at circumventing current clinical impasses. Additionally, the prospective utilities and inherent challenges of the biotherapeutics are deliberated, with the objective of accelerating their clinical application in the foreseeable future.

Design of probiotic delivery systems and their therapeutic effects on targeted tissues

The microbiota at different sites in the body is closely related to disease. The intake of probiotics is an effective strategy to alleviate diseases and be adjuvant in their treatment. However, probiotics may suffer from harsh environments and colonization resistance, making it difficult to maintain a sufficient number of live probiotics to reach the target sites and exert their original probiotic effects. Encapsulation of probiotics is an effective strategy. Therefore, probiotic delivery systems, as effective methods, have been continuously developed and innovated to ensure that probiotics are effectively delivered to the targeted site. In this review, initially, the design of probiotic delivery systems is reviewed from four aspects: probiotic characteristics, processing technologies, cell-derived wall materials, and interactions between wall materials. Subsequently, the review focuses on the effects of probiotic delivery systems that target four main microbial colonization sites: the oral cavity, skin, intestine, and vagina, as well as disease sites such as tumors. Finally, this review also discusses the safety concerns of probiotic delivery systems in the treatment of disease and the challenges and limitations of implementing this method in clinical studies. It is necessary to conduct more clinical studies to evaluate the effectiveness of different probiotic delivery systems in the treatment of diseases.

Nanomaterial combined engineered bacteria for intelligent tumor immunotherapy

Cancer remains the leading cause of human death worldwide. Compared to traditional therapies, tumor immunotherapy has received a lot of attention and research focus due to its potential to activate both innate and adaptive immunity, low toxicity to normal tissue, and long-term immune activity. However, its clinical effectiveness and large-scale application are limited due to the immunosuppression microenvironment, lack of spatiotemporal control, expensive cost, and long manufacturing time. Recently, nanomaterial combined engineered bacteria have emerged as a promising solution to the challenges of tumor immunotherapy, which offers spatiotemporal control, reversal of immunosuppression, and scalable production. Therefore, we summarize the latest research on nanomaterial-assisted engineered bacteria for precise tumor immunotherapies, including the cross-talk of nanomaterials and bacteria as well as their application in different immunotherapies. In addition, we further discuss the advantages and challenges of nanomaterial-engineered bacteria and their future prospects, inspiring more novel and intelligent tumor immunotherapy.

Microbe-material hybrids for therapeutic applications

As natural living substances, microorganisms have emerged as useful resources in medicine for creating microbe-material hybrids ranging from nano to macro dimensions. The engineering of microbe-involved nanomedicine capitalizes on the distinctive physiological attributes of microbes, particularly their intrinsic "living" properties such as hypoxia tendency and oxygen production capabilities. Exploiting these remarkable characteristics in combination with other functional materials or molecules enables synergistic enhancements that hold tremendous promise for improved drug delivery, site-specific therapy, and enhanced monitoring of treatment outcomes, presenting substantial opportunities for amplifying the efficacy of disease treatments. This comprehensive review outlines the microorganisms and microbial derivatives used in biomedicine and their specific advantages for therapeutic application. In addition, we delineate the fundamental strategies and mechanisms employed for constructing microbe-material hybrids. The diverse biomedical applications of the constructed microbe-material hybrids, encompassing bioimaging, anti-tumor, anti-bacteria, anti-inflammation and other diseases therapy are exhaustively illustrated. We also discuss the current challenges and prospects associated with the clinical translation of microbe-material hybrid platforms. Therefore, the unique versatility and potential exhibited by microbe-material hybrids position them as promising candidates for the development of next-generation nanomedicine and biomaterials with unique theranostic properties and functionalities.

Functional modification of gut bacteria for disease diagnosis and treatment

Intestinal bacteria help keep humans healthy by regulating lipid and glucose metabolism as well as the immunological and neurological systems. Oral treatment using intestinal bacteria is limited by the high acidity of stomach fluids and the immune system's attack on foreign bacteria. Scientists have created coatings and workarounds to overcome these limitations and improve bacterial therapy. These preparations have demonstrated promising outcomes, with advances in synthetic biology and optogenetics improving their focused colonization and controlled release. Engineering bacteria preparations have become a revolutionary therapeutic approach that converts intestinal bacteria into cellular factories for medicinal chemical synthesis. The present paper discusses various aspects of engineering bacteria preparations, including wrapping materials, biomedical uses, and future developments.

Engineered E. coli for Long-Term Oral Enzyme Delivery

Intestinal flora shows excellent affinity in the gut, and the adhesive property is borrowed for oral drug delivery. A facile strategy for bacteria engineering has been successfully developed by introducing metal-organic framework (MOF) mineralization. The MOF exoskeleton serves as an extendable platform for accommodating various cargoes with good Escherichia coli morphology maintained. The artificial exoskeleton surrounding E. coli is employed for encapsulating macromolecules as a therapeutic cargo, maintaining good bioactivity with high immobilization efficiency (60%) after systematic optimization of the MOF precursor. Leveraging the natural affinity of E. coli in the gut, the in-vivo tracking of MOF-engineered E. coli in the gastrointestinal tract confirmed excellent adhesion to the GI mucosa and a 17.9-fold increase in the gut retention half-time, demonstrating significant advantages in retention capability. In comparison, the control group without E. coli equipment resulted in quick gut passage. Furthermore, the artificially engineered E. coli serves as an effective carrier for macromolecules without notable oral toxicity, as evidenced by biocompatibility evaluations in cells and animals. Overall, the MOF-engineered E. coli provides an extendable platform for loading on-demand cargoes in versatile therapeutic functions with promising clinical transnationality for long-term applications.

Intestinal Delivery of Probiotics: Materials, Strategies, and Applications

Probiotics with diverse and crucial properties and functions have attracted broad interest from many researchers, who adopt intestinal delivery of probiotics to modulate the gut microbiota. However, the major problems faced for the therapeutic applications of probiotics are the viability and colonization of probiotics during their processing, oral intake, and subsequent delivery to the gut. The challenges of simple oral delivery (stability, controllability, targeting, etc.) have greatly limited the use of probiotics in clinical therapies. Nanotechnology can endow the probiotics to be delivered to the intestine with improved survival rate and increased resistance to the adverse environment. Additionally, the progress in synthetic biology has created new opportunities for efficiently and purposefully designing and manipulating the probiotics. In this article, a brief overview of the types of probiotics for intestinal delivery, the current progress of different probiotic encapsulation strategies, including the chemical, physical, and genetic strategies and their combinations, and the emerging single-cell encapsulation strategies using nanocoating methods, is presented. The action mechanisms of probiotics that are responsible for eliciting beneficial effects are also briefly discussed. Finally, the therapeutic applications of engineered probiotics are discussed, and the future trends toward developing engineered probiotics with advanced features and improved health benefits are proposed.

Toward Photosynthetic Mammalian Cells through Artificial Endosymbiosis

Photosynthesis in plants occurs within specialized organelles known as chloroplasts, which are postulated to have originated through endosymbiosis with cyanobacteria. In nature, instances are also observed wherein specific invertebrates engage in symbiotic relationships with photosynthetic bacteria, allowing them to subsist as photoautotrophic organisms over extended durations. Consequently, the concept of engineering artificial endosymbiosis between mammalian cells and cyanobacteria represents a promising avenue for enabling photosynthesis in mammals. The study embarked with the identification of Synechocystis PCC 6803 as a suitable candidate for establishing a long-term endosymbiotic relationship with macrophages. The cyanobacteria internalized by macrophages exhibited the capacity to rescue ATP deficiencies within their host cells under conditions of illumination. Following this discovery, a membrane-coating strategy is developed for the intracellular delivery of cyanobacteria into non-macrophage mammalian cells. This pioneering technique led to the identification of human embryonic kidney cells HEK293 as optimal hosts for achieving sustained endosymbiosis with Synechocystis PCC 6803. The study offers valuable insights that may serve as a reference for the eventual achievement of artificial photosynthesis in mammals.

Surface nanocoating of bacteria as a versatile platform to develop living therapeutics

Bacteria have been extensively utilized as living therapeutics for disease treatment due to their unique characteristics, such as genetic manipulability, rapid proliferation and specificity to target disease sites. Various in vivo insults can, however, decrease the vitality of dosed bacteria, leading to low overall bioavailability. Additionally, the innate antigens on the bacterial surface and the released toxins and metabolites may cause undesired safety issues. These limitations inevitably result in inadequate treatment outcomes, thereby hindering the clinical transformation of living bacterial therapeutics. Recently, we have developed a versatile platform to prepare advanced living bacterial therapeutics by nanocoating bacteria individually via either chemical decoration or physical encapsulation, which can improve bioavailability and reduce side effects for enhanced microbial therapy. Here we use interfacial self-assembly to prepare lipid membrane-coated bacteria (LCB), exhibiting increased resistance against a variety of harsh environmental conditions owing to the nanocoating's protective capability. Meanwhile, we apply mechanical extrusion to generate cell membrane-coated bacteria (CMCB), displaying improved biocompatibility owing to the nanocoating's shielding effect. We describe their detailed preparation procedures and demonstrate the expected functions of the coated bacteria. We also show that following oral delivery and intravenous injection in mouse models, LCB and CMCB present appealing potential for treating colitis and tumors, respectively. Compared with bioengineering that lacks versatile molecular tools for heterogeneous expression, the surface nanocoating technique is convenient to introduce functional components without restriction on bacterial strain types. Excluding bacterial culture, the fabrication of LCB takes ~2 h, while the preparation of CMCB takes ~5 h.

Preparation of environmentally responsive PDA&DOX@LAC live drug carrier for synergistic tumor therapy

The development of intelligent, environmentally responsive and biocompatible photothermal system holds significant importance for the photothermal combined therapy of tumors. In this study, inspired by Lactobacillus (LAC), we prepared a biomimetic nanoplatform PDA&DOX@LAC for tumor photothermal-chemotherapy by integrating the chemotherapeutic drug doxorubicin (DOX) with dopamine through oxidative polymerization to form polydopamine (PDA) on the surface of LAC. The PDA&DOX@LAC nanoplatform not only achieves precise and controlled release of DOX based on the slightly acidic microenvironment of tumor tissues, but also exhibits enzyme-like properties to alleviate tumor hypoxia. Under near-infrared light irradiation, it effectively induces photothermal ablation of tumor cells, enhances cellular uptake of DOX with increasing temperature, and thus efficiently inhibits tumor cell growth. Moreover, it is further confirmed in vivo experiments that photothermal therapy combined with PDA&DOX@LAC induces tumor cells apoptosis, releases tumor-associated antigens, which is engulfed by dendritic cells to activate cytotoxic T lymphocytes, thereby effectively suppressing tumor growth and prolonging the survival period of 4T1 tumor-bearing mice. Therefore, the PDA&DOX@LAC nanoplatform holds immense potential in precise tumor targeting as well as photothermal combined therapy and provides valuable insights and theoretical foundations for the development of novel tumor treatment strategies based on endogenous substances within the body.

Novel strategies for modulating the gut microbiome for cancer therapy

Recent advancements in genomics, transcriptomics, and metabolomics have significantly advanced our understanding of the human gut microbiome and its impact on the efficacy and toxicity of anti-cancer therapeutics, including chemotherapy, immunotherapy, and radiotherapy. In particular, prebiotics, probiotics, and postbiotics are recognized for their unique properties in modulating the gut microbiota, maintaining the intestinal barrier, and regulating immune cells, thus emerging as new cancer treatment modalities. However, clinical translation of microbiome-based therapy is still in its early stages, facing challenges to overcome physicochemical and biological barriers of the gastrointestinal tract, enhance target-specific delivery, and improve drug bioavailability. This review aims to highlight the impact of prebiotics, probiotics, and postbiotics on the gut microbiome and their efficacy as cancer treatment modalities. Additionally, we summarize recent innovative engineering strategies designed to overcome challenges associated with oral administration of anti-cancer treatments. Moreover, we will explore the potential benefits of engineered gut microbiome-modulating approaches in ameliorating the side effects of immunotherapy and chemotherapy.

Advances in bacteria-based drug delivery systems for anti-tumor therapy

In recent years, bacteria have gained considerable attention as a promising drug carrier that is critical in improving the effectiveness and reducing the side effects of anti-tumor drugs. Drug carriers can be utilised in various forms, including magnetotactic bacteria, bacterial biohybrids, minicells, bacterial ghosts and bacterial spores. Additionally, functionalised and engineered bacteria obtained through gene engineering and surface modification could provide enhanced capabilities for drug delivery. This review summarises the current studies on bacteria-based drug delivery systems for anti-tumor therapy and discusses the prospects and challenges of bacteria as drug carriers. Furthermore, our findings aim to provide new directions and guidance for the research on bacteria-based drug systems.

Melanin Nanoparticle-Modified Probiotics for Targeted Synergistic Therapy of Ulcerative Colitis

Ulcerative colitis (UC) is a recurrent chronic mucosal inflammation disease whose most significant pathological characteristics are intestinal inflammation and damaged mucosal barrier induced by reactive oxygen/nitrogen species, abnormal immune microenvironment, and intestinal microecological imbalance. Oral probiotics are a living therapy for intestinal diseases, but their clinical application is hindered by poor bacterial biological activity and insufficient intestinal retention. Here, we developed a targeted oral formulation, functionalized probiotic Lf@MPB, with Lactobacillus fermentum (Lf) as the core and modified melanin nanoparticles (MNPs) on its surface through a click reaction of tricarboxyphenylboronic acid for synergistic therapy of UC. In vitro experiments showed that Lf@MPB not only possessed strong free radical scavenging ability, reduced cellular mitochondrial polarization, and inhibited apoptosis but also significantly enhanced the viability of Lf probiotics in simulated gastrointestinal fluid. Fluorescence imaging in vivo revealed the high accumulation of Lf@MPB at the site of intestinal inflammation in dextran sulfate sodium-induced UC mice. Moreover, in vivo results demonstrated that Lf@MPB effectively alleviated oxidative stress and inflammatory response and restored the intestinal barrier. In addition, 16S rRNA gene sequencing verified that Lf@MPB could increase the abundance and diversity of intestinal microbial communities and optimize microbial composition to inhibit the progression of UC. This work combines effective antioxidant and anti-inflammatory strategies with the oral administration of functionalized probiotics to provide a promising alternative for UC treatment.

Breaking barriers: bacterial-microalgae symbiotic systems as a probiotic delivery system

The gut microbiota is one of the essential contributors of the pathogenesis and progress of inflammatory bowel disease (IBD). Compared with first-line drug therapy, probiotic supplementation has emerged as a viable and secure therapeutic approach for managing IBD through the regulation of both the immune system and gut microbiota. Nevertheless, the efficacy of oral probiotic supplements is hindered by their susceptibility to the gastrointestinal barrier, leading to diminished bioavailability and restricted intestinal colonization. Here, we developed a bacteria-microalgae symbiosis system (EcN-SP) for targeted intestinal delivery of probiotics and highly effective treatment of colitis. The utilization of mircroalge Spirulina platensis (SP) as a natural carrier for the probiotic Escherichia coli Nissle 1917 (EcN) demonstrated potential benefits in promoting EcN proliferation, facilitating effective intestinal delivery and colonization. The alterations in the binding affinity of EcN-SP within the gastrointestinal environment, coupled with the distinctive structural properties of the SP carrier, served to overcome gastrointestinal barriers, minimizing transgastric EcN loss and enabling sustained intestinal retention and colonization. The oral administration of EcN-SP could effectively treat IBD by reducing the expression of intestinal inflammatory factors, maintaining the intestinal barrier and regulating the balance of gut microbiota. This probiotic delivery approach is inspired by symbiotic interactions found in nature and offers advantages in terms of feasibility, safety, and efficacy, thus holding significant promise for the management of gastrointestinal disorders.

Engineered Microorganisms for Advancing Tumor Therapy

Engineered microorganisms have attracted significant interest as a unique therapeutic platform in tumor treatment. Compared with conventional cancer treatment strategies, engineering microorganism-based systems provide various distinct advantages, such as the intrinsic capability in targeting tumors, their inherent immunogenicity, in situ production of antitumor agents, and multiple synergistic functions to fight against tumors. Herein, the design, preparation, and application of the engineered microorganisms for advanced tumor therapy are thoroughly reviewed. This review presents a comprehensive survey of innovative tumor therapeutic strategies based on a series of representative engineered microorganisms, including bacteria, viruses, microalgae, and fungi. Specifically, it offers extensive analyses of the design principles, engineering strategies, and tumor therapeutic mechanisms, as well as the advantages and limitations of different engineered microorganism-based systems. Finally, the current challenges and future research prospects in this field, which can inspire new ideas for the design of creative tumor therapy paradigms utilizing engineered microorganisms and facilitate their clinical applications, are discussed.

Advances of Bacterial Biomaterials for Disease Therapy

Bacteria have immense potential as biological therapeutic agents that can be used to treat diseases, owing to their inherent immunomodulatory activity, targeting capabilities, and biosynthetic functions. The integration of synthetic biomaterials with natural bacteria has led to the construction of bacterial biomaterials with enhanced functionality and exceptional safety features. In this review, recent progress in the field of bacterial biomaterials, including bacterial drug delivery systems, bacterial drug-producing factories, bacterial biomaterials for metabolic engineering, bacterial biomaterials that can be remotely controlled, and living bacteria hydrogel formulations, is described and summarized. Furthermore, future trends in advancing next-generation bacterial biomaterials for enhanced clinical applications are proposed in the conclusion.

Novel Drug Delivery Systems: An Important Direction for Drug Innovation Research and Development

The escalating demand for enhanced therapeutic efficacy and reduced adverse effects in the pharmaceutical domain has catalyzed a new frontier of innovation and research in the field of pharmacy: novel drug delivery systems. These systems are designed to address the limitations of conventional drug administration, such as abbreviated half-life, inadequate targeting, low solubility, and bioavailability. As the disciplines of pharmacy, materials science, and biomedicine continue to advance and converge, the development of efficient and safe drug delivery systems, including biopharmaceutical formulations, has garnered significant attention both domestically and internationally. This article presents an overview of the latest advancements in drug delivery systems, categorized into four primary areas: carrier-based and coupling-based targeted drug delivery systems, intelligent drug delivery systems, and drug delivery devices, based on their main objectives and methodologies. Additionally, it critically analyzes the technological bottlenecks, current research challenges, and future trends in the application of novel drug delivery systems.

Bacteria Synergized with PD-1 Blockade Enhance Positive Feedback Loop of Cancer Cells-M1 Macrophages-T Cells in Glioma

Cancer immunotherapy is an attractive strategy because it stimulates immune cells to target malignant cells by regulating the intrinsic activity of the immune system. However, due to lacking many immunologic markers, it remains difficult to treat glioma, a representative "cold" tumor. Herein, to wake the "hot" tumor immunity of glioma, Porphyromonas gingivalis (Pg) is customized with a coating to create an immunogenic tumor microenvironment and further prove the effect in combination with the immune checkpoint agent anti-PD-1, exhibiting elevated therapeutic efficacy. This is accomplished not by enhancing the delivery of PD-1 blockade to enhance the effect of immunotherapy, but by introducing bacterial photothermal therapy to promote greater involvement of M1 cells in the immune response. After reaching glioma, the bacteria further target glioma cells and M2 phenotype macrophages selectively, enabling precise photothermal conversion for lysing tumor cells and M2 phenotype macrophages, which thereby enhances the positive feedback loop of cancer cells-M1 macrophages-T cells. Collectively, the bacteria synergized with PD-1 blockade strategy may be the key to overcoming the immunosuppressive glioma microenvironment and improving the outcome of immunotherapy toward glioma.

Enzyme-like biomimetic oral-agent enabling modulating gut microbiota and restoring redox homeostasis to treat inflammatory bowel disease

Reactive oxygen species (ROS), immune dysregulation-induced inflammatory outbreaks and microbial imbalance play critical roles in the development of inflammatory bowel disease (IBD). Herein, a novel enzyme-like biomimetic oral-agent ZnPBA@YCW has been developed, using yeast cell wall (YCW) as the outer shell and zinc-doped Prussian blue analogue (ZnPBA) nanozyme inside. When orally administered, the ZnPBA@YCW is able to adhere to Escherichia coli occupying the ecological niche in IBD and subsequently release the ZnPBA nanozyme for removal of E. coli, meanwhile exhibiting improved intestinal epithelial barrier repair. Moreover, it is found that the ZnPBA nanozyme exhibits remarkable capability in restoring redox homeostasis by scavenging ROS and inhibiting NF-κB signaling pathway. More importantly, the 16S ribosomal RNA gene sequencing results indicate that post-oral of ZnPBA@YCW can effectively regulate gut microbiota by enhancing the bacterial richness and diversity, significantly increasing the abundance of probiotics with anti-inflammatory phenotype while downgrading pathogenic E. coli to the same level as normal mice. Such a novel nanomedicine provides a new idea for efficient treating those ROS-mediated diseases accompanying with flora disorders.

Biochemotaxis-Oriented Engineering Bacteria Expressing GLP-1 Enhance Diabetes Therapy by Regulating the Balance of Immune

Glucagon like peptide-1 (GLP-1) is an effective hypoglycemic drug that can repair the pancreas β cells and promote insulin secretion. However, GLP-1 has poor stability and lacks of target ability, which makes it difficult to reach the site of action to exert its efficacy. Here, GLP-1-expressing plasmids are introduced into the Escherichia coli Nissle 1917 (EcN) and a lipid membrane is formed through simple self-assembly on its surface, resulting in an oral delivery system (LEG) capable of resisting the harsh environment of the gastrointestinal tract. The system utilizes the chemotactic properties of probiotics to achieve efficient enrichment at the pancreatic site, and protects islet β cells from destruction by regulating the balance of immune cells. More interestingly, LEG not only continuously produces GLP-1 to restore pancreatic islet β cell function and secrete insulin to control blood sugar levels, but also regulates the intestinal flora and increases the richness and diversity of probiotics. In mice diabetes models, oral administration of LEG only once every other day has good biosafety and compliance, and achieves long-term control of blood glucose. Therefore, this strategy not only provides an oral delivery platform for pancreatic targeting, but also opens up new avenues for reversing diabetes.

Upconversion dual-photosensitizer-expressing bacteria for near-infrared monochromatically excitable synergistic phototherapy

Synergistic phototherapy stands for superior treatment prospects than a single phototherapeutic modality. However, the combined photosensitizers often suffer from incompatible excitation mode, limited irradiation penetration depth, and lack of specificity. We describe the development of upconversion dual-photosensitizer-expressing bacteria (UDPB) for near-infrared monochromatically excitable combination phototherapy. UDPB are prepared by integrating genetic engineering and surface modification, in which bacteria are encoded to simultaneously express photothermal melanin and phototoxic KillerRed protein and the surface primary amino groups are derived to free thiols for biorthogonal conjugation of upconversion nanoparticles. UDPB exhibit a near-infrared monochromatic irradiation-mediated dual-activation characteristic as the photothermal conversion of melanin can be initiated directly, while the photodynamic effect of KillerRed can be stimulated indirectly by upconverted visible light emission. UDPB also show living features to colonize hypoxic lesion sites and inhibit pathogens via bacterial community competition. In two murine models of solid tumor and skin wound infection, UDPB separately induce robust antitumor response and a rapid wound healing effect.

Layer-by-layer coated probiotics with chitosan and liposomes demonstrate improved stability and antioxidant properties in vitro

Probiotics are of increasing interest for their potential health benefits, but their survival and adhesion in the harsh gastrointestinal environment remain a concern. This study explored a single-cell encapsulation technique to enhance probiotic survival and adhesion in the gastrointestinal tract. We encapsulated probiotics in curcumin-loaded liposomes, further coated them with polymers using layer-by-layer techniques. The coated probiotics were evaluated for survival in simulated gastrointestinal conditions, adhesion to colonic mucus, and scavenging of reactive oxygen species (ROS). The results showed that multi-layer encapsulation increased probiotic size at the nanoscale, enhancing their survival in simulated gastrointestinal conditions. Upon reaching the colon, the shedding of the coating coincided with probiotic proliferation. Additionally, the coated probiotics exhibited increased adhesion to colonic mucus. Moreover, the coating acted as a protective barrier for effectively scavenging reactive oxygen radicals, ensuring probiotic survival in inflammatory environments. This study combines the synergistic effects of probiotics and curcumin, underscoring the promise of single-cell encapsulation techniques in improving the efficacy of probiotics for addressing colitis-related diseases.

Bacteria-based drug delivery for treating non-oncological diseases

Bacteria inhabit all over the human body, especially the skin, gastrointestinal tract, respiratory tract, urogenital tract, as well as specific lesion sites, such as wound and tumor. By leveraging their distinctive attributes including rapid proliferation, inherent abilities to colonize various biointerfaces in vivo and produce diverse biomolecules, and the flexibility to be functionalized via genetic engineering or surface modification, bacteria have been widely developed as living therapeutic agents, showing promising potential to make a great impact on the exploration of advanced drug delivery systems. In this review, we present an overview of bacteria-based drug delivery and its applications in treating non-oncological diseases. We systematically summarize the physiological positions where living bacterial therapeutic agents can be delivered to, including the skin, gastrointestinal tract, respiratory tract, and female genital tract. We discuss the success of using bacteria-based drug delivery systems in the treatment of diseases that occur in specific locations, such as skin wound healing/infection, inflammatory bowel disease, respiratory diseases, and vaginitis. We also discuss the advantages as well as the limitations of these living therapeutics and bacteria-based drug delivery, highlighting the key points that need to be considered for further translation. This review article may provide unique insights for designing next-generation bacteria-based therapeutics and developing advanced drug delivery systems.

Bacterial therapies at the interface of synthetic biology and nanomedicine

Bacteria are emerging as living drugs to treat a broad range of disease indications. However, the inherent advantages of these replicating and immunostimulatory therapies also carry the potential for toxicity. Advances in synthetic biology and the integration of nanomedicine can address this challenge through the engineering of controllable systems that regulate spatial and temporal activation for improved safety and efficacy. Here, we review recent progress in nanobiotechnology-driven engineering of bacteria-based therapies, highlighting limitations and opportunities that will facilitate clinical translation.

Gram-negative bacterial sRNAs encapsulated in OMVs: an emerging class of therapeutic targets in diseases

Small regulatory RNAs (sRNAs) encapsulated in outer membrane vesicles (OMVs) are critical post-transcriptional regulators of gene expression in prokaryotic and eukaryotic organisms. OMVs are small spherical structures released by Gram-negative bacteria that serve as important vehicles for intercellular communication and can also play an important role in bacterial virulence and host-pathogen interactions. These molecules can interact with mRNAs or proteins and affect various cellular functions and physiological processes in the producing bacteria. This review aims to provide insight into the current understanding of sRNA localization to OMVs in Gram-negative bacteria and highlights the identification, characterization and functional implications of these encapsulated sRNAs. By examining the research gaps in this field, we aim to inspire further exploration and progress in investigating the potential therapeutic applications of OMV-encapsulated sRNAs in various diseases.

The single-cell modification strategies for probiotics delivery in inflammatory bowel disease: A review

Oral probiotic therapy has become an increasingly attractive method for treating various diseases, including intestinal barrier dysfunction, inflammatory bowel disease (IBD), and colorectal cancer due to its safety and convenience. However, only a few probiotics after oral gavage can survive the acidic and bile salt conditions of the gastrointestinal tract and colonize the colon to have a nutritional effect on the host. To address these challenges, encapsulation technology has been applied to protect probiotics from harsh gastrointestinal conditions, improve gut adhesion, and reduce immunogenicity. In addition, some of the functional polysaccharides are used to endow probiotics with exogenous functions as prebiotics. In this review, we systematically introduced the advancements of emerging single-cell modification strategies for probiotics in IBD applications. Additionally, we discussed the limitations and perspectives of single-cell modification strategies for probiotics. This review contributed to the development of probiotic delivery systems with higher therapeutic efficacy against colitis.

Camouflaging attenuated Salmonella by cryo-shocked macrophages for tumor-targeted therapy

Live bacteria-mediated antitumor therapies mark a pivotal point in cancer immunotherapy. However, the difficulty in reconciling the safety and efficacy of bacterial therapies has limited their application. Improving bacterial tumor-targeted delivery while maintaining biosafety is a critical hurdle for the clinical translation of live microbial therapy for cancer. Here, we developed "dead" yet "functional" Salmonella-loaded macrophages using liquid nitrogen cold shock of an attenuated Salmonella typhimurium VNP20009-contained macrophage cell line. The obtained "dead" macrophages achieve an average loading of approximately 257 live bacteria per 100 cells. The engineered cells maintain an intact cellular structure but lose their original pathogenicity, while intracellular bacteria retain their original biological activity and are delay freed, followed by proliferation. This "Trojan horse"-like bacterial camouflage strategy avoids bacterial immunogenicity-induced neutrophil recruitment and activation in peripheral blood, reduces the clearance of bacteria by neutrophils and enhances bacterial tumor enrichment efficiently after systemic administration. Furthermore, this strategy also strongly activated the tumor microenvironment, including increasing antitumor effector cells (including M1-like macrophages and CD8+ Teffs) and decreasing protumor effector cells (including M2-like macrophages and CD4+ Tregs), and ultimately improved antitumor efficacy in a subcutaneous H22 tumor-bearing mouse model. The cryo-shocked macrophage-mediated bacterial delivery strategy holds promise for expanding the therapeutic applications of living bacteria for cancer.

Bacteria-Based Living Probes: Preparation and the Applications in Bioimaging and Diagnosis

Bacteria can colonize a variety of in vivo biointerfaces, particularly the skin, nasal, and oral mucosa, the gastrointestinal tract, and the reproductive tract, but also target specific lesion sites, such as tumor and wound. By virtue of their prominent characteristics in motility, editability, and targeting ability, bacteria carrying imageable agents are widely developed as living probes for bioimaging and diagnosis of different diseases. This review first introduces the strategies used for preparing bacteria-based living probes, including biological engineering, chemical modification, intracellular loading, and optical manipulation. It then summarizes the recent progress of these living probes for fluorescence imaging, near-infrared imaging, ultrasonic imaging, photoacoustic imaging, magnetic resonance imaging, and positron emission tomography imaging. The biomedical applications of bacteria-based living probes are also reviewed particularly in the bioimaging and diagnosis of bacterial infections, cancers, and intestine-associated diseases. In addition, the advantages and challenges of bacteria-based living probes are discussed and future perspectives are also proposed. This review provides an updated overview of bacteria-based living probes, highlighting their great potential as a unique yet versatile platform for developing next-generation imageable agents for intelligent bioimaging, diagnosis, and even therapy.

Cancer cell membrane-coated bacterial ghosts for highly efficient paclitaxel delivery against metastatic lung cancer

Chemotherapy is one of the major approaches for the treatment of metastatic lung cancer, although it is limited by the low tumor delivery efficacy of anticancer drugs. Bacterial therapy is emerging for cancer treatment due to its high immune stimulation effect; however, excessively generated immunogenicity will cause serious inflammatory response syndrome. Here, we prepared cancer cell membrane-coated liposomal paclitaxel-loaded bacterial ghosts (LP@BG@CCM) by layer-by-layer encapsulation for the treatment of metastatic lung cancer. The preparation processes were simple, only involving film formation, electroporation, and pore extrusion. LP@BG@CCM owned much higher 4T1 cancer cell toxicity than LP@BG due to its faster fusion with cancer cells. In the 4T1 breast cancer metastatic lung cancer mouse models, the remarkably higher lung targeting of intravenously injected LP@BG@CCM was observed with the almost normalized lung appearance, the reduced lung weight, the clear lung tissue structure, and the enhanced cancer cell apoptosis compared to its precursors. Moreover, several major immune factors were improved after administration of LP@BG@CCM, including the CD4+/CD8a+ T cells in the spleen and the TNF-α, IFN-γ, and IL-4 in the lung. LP@BG@CCM exhibits the optimal synergistic chemo-immunotherapy, which is a promising medication for the treatment of metastatic lung cancer.

Red blood cells in biology and translational medicine: natural vehicle inspires new biomedical applications

Red blood cells (RBCs) are the most abundant cell type in the blood, and play a critical role in oxygen transport. With the development of nanobiotechnology and synthetic biology, scientists have found multiple ways to take advantage of the characteristics of RBCs, such as their long circulation time, to construct universal RBCs, develop drug delivery systems, and transform cell therapies for cancer and other diseases. This article reviews the component and aging mystery of RBCs, the methods for the applied universal RBCs, and the application prospects of RBCs, such as the engineering modification of RBCs used in cytopharmaceuticals for drug delivery and immunotherapy. Finally, we summarize some perspectives on the biological features of RBCs and provide further insights into translational medicine.

Triggerable Prodrug Nanocoating Enables On-Demand Activation of Microbial and Small-Molecular Therapeutics for Combination Treatment

The synergy of living microbial and small-molecular therapeutics has been widely explored for treating a variety of diseases, while current combination strategies often suffer from low bioavailability, heterogeneous spatiotemporal distribution, and premature drug release. Here, the use of a triggerable prodrug nanocoating is reported to enable the on-demand activation of microbial and small-molecular therapeutics for combination treatment. As a proof-of-concept study, a reactive oxygen species-responsive aromatic thioacetal linker is employed to prepare cationic chitosan-drug conjugates, which can form a nanocoating on the surface of living bacteria via electrostatic interaction. Following administration, the wrapped bacteria can be prevented from in vivo insults by the shielding effect of the nanocoating and be co-delivered with the conjugated drug in a spatiotemporally synchronous manner. Upon reaching the lesion site, the upgraded reactive oxygen species trigger in situ cleavage of the thioacetal linker, resulting in the release of the conjugated drug and a linker-derived therapeutic cinnamaldehyde. Meanwhile, a charge reversal achieved by the generation of negatively charged thiolated chitosan induces the dissociation of the nanocoating, leading to synchronous release of the living bacteria. The adequate activation of the combined therapeutics at the lesion site exhibits superior synergistic treatment efficacy, as demonstrated by an in vivo assessment using a mouse model of colitis. This work presents an appealing approach to combine living microbial and small-molecular therapeutics for advanced therapy of diseases.

Converting bacteria into autologous tumor vaccine via surface biomineralization of calcium carbonate for enhanced immunotherapy

Autologous cancer vaccine that stimulates tumor-specific immune responses for personalized immunotherapy holds great potential for tumor therapy. However, its efficacy is still suboptimal due to the immunosuppressive tumor microenvironment (ITM). Here, we report a new type of bacteria-based autologous cancer vaccine by employing calcium carbonate (CaCO3) biomineralized Salmonella (Sal) as an in-situ cancer vaccine producer and systematical ITM regulator. CaCO3 can be facilely coated on the Sal surface with calcium ionophore A23187 co-loading, and such biomineralization did not affect the bioactivities of the bacteria. Upon intratumoral accumulation, the CaCO3 shell was decomposed at an acidic microenvironment to attenuate tumor acidity, accompanied by the release of Sal and Ca2+/A23187. Specifically, Sal served as a cancer vaccine producer by inducing cancer cells' immunogenic cell death (ICD) and promoting the gap junction formation between tumor cells and dendritic cells (DCs) to promote antigen presentation. Ca2+, on the other hand, was internalized into various types of immune cells with the aid of A23187 and synergized with Sal to systematically regulate the immune system, including DCs maturation, macrophages polarization, and T cells activation. As a result, such bio-vaccine achieved remarkable efficacy against both primary and metastatic tumors by eliciting potent anti-tumor immunity with full biocompatibility. This work demonstrated the potential of bioengineered bacteria as bio-active vaccines for enhanced tumor immunotherapy.

Surface engineering Salmonella with pH-responsive polyserotonin and self-activated DNAzyme for better microbial therapy of tumor

Bacteria-based microbial immunotherapy shows various unique properties for tumor therapy owing to their active tropism to tumor and multiple anti-tumor mechanisms. However, its clinical benefit is far from satisfactory, which is limited by rapid systemic clearance and neutrophils-mediated immune restriction to compromise the efficacy, as well as non-specific distribution to cause toxicity. To address all these limitations, herein we reported a polyserotonin (PST) coated Salmonella (Sal) with surface adsorption of DNAzyme (Dz)-functionalized MnO2 nanoparticles (DzMN) for tumor therapy. PST could facilely coat on Sal surface via oxidation and self-polymerization of its serotonin monomer, which enabled surface stealth to avoid rapid systemic clearance while maintaining the tumor homing effect. Upon targeting to tumor, the PST was degraded and exfoliated in response to acidic tumor microenvironment, thus liberating Sal to recover its anti-tumor activities. Meanwhile, the DzMN was also delivered into tumor via hitchhiking Sal, which could release Dz and Mn2+ after tumor cells internalization. The Dz was then activated by its cofactor of Mn2+ to cleave target PD-L1 mRNA, thus serving as a self-activated system for gene silencing. Combining Sal and Dz for immune activation and PD-L1 knockdown, respectively, anti-tumor immunotherapy was achieved with enhanced efficacy. Notably, PST coating could significantly decrease infection potential and non-specific colonization of Sal at normal organs, achieving high in vivo biosafety. This work addresses the key limitations of Sal for in vivo application via biomaterials modification, and provides a promising platform for better microbial immunotherapy.

An Outer Membrane-Inspired Polymer Coating Protects and Endows Escherichia coli with Novel Functionalities

A bio-inspired membrane made of Pluronic L-121 is produced around Escherichia coli thanks to the simple co-extrusion of bacteria and polymer vesicles. The block copolymer-coated bacteria can withstand various harsh shocks, for example, temperature, pressure, osmolarity, and chemical agents. The polymer membrane also makes the bacteria resistant to enzymatic digestion and enables them to degrade toxic compounds, improving their performance as whole-cell biocatalysts. Moreover, the polymer membrane acts as an anchor layer for the surface modification of the bacteria. Being decorated with α-amylase or lysozyme, the cells are endowed with the ability to digest starch or self-predatory bacteria are created. Thus, without any genetic engineering, the phenotype of encapsulated bacteria is changed as they become sturdier and gain novel metabolic functionalities.

Advancement of Engineered Bacteria for Orally Delivered Therapeutics

The use of bacteria and their biotic components as therapeutics has shown great potential in the treatment of diseases. Orally delivered bacteria improve patient compliance compared with injection-administered bacteria and are considered the preferred mode. However, due to the harsh gastrointestinal environment, the viability and therapeutic efficacy of orally delivered bacteria are significantly reduced in vivo. In recent years, with the rapid development of synthetic biology and nanotechnology, bacteria and biotic components have been engineered to achieve directed genetic reprogramming for construction and precise spatiotemporal control in the gastrointestinal tract, which can improve viability and therapeutic efficiency. Herein, a state-of-the-art review on the current progress of engineered bacterial systems for oral delivery is provided. The different types of bacterial and biotic components for oral administration are first summarized. The engineering strategies of these bacteria and biotic components and their treatment of diseases are next systematically summarized. Finally, the current challenges and prospects of these bacterial therapeutics are highlighted that will contribute to the development of next-generation orally delivered bacteriotherapy.

Armored probiotics for oral delivery

As a kind of intestinal flora regulator, probiotics show great potential in the treatment of many diseases. However, orally delivered probiotics are often vulnerable to unfriendly gastrointestinal environments, resulting in a low survival rate and decreased therapeutic efficacy. Decorating or encapsulating probiotics with functional biomaterials has become a facile yet useful strategy, and probiotics can be given different functions by wearing different armors. This review systematically discusses the challenges faced by oral probiotics and the research progress of armored probiotics delivery systems. We focus on how various functional armors help probiotics overcome different obstacles and achieve efficient delivery. We also introduce the applications of armor probiotics in disease treatment and analyze the future trends of developing advanced probiotics-based therapies.

Bacteria and Bacterial Components as Natural Bio-Nanocarriers for Drug and Gene Delivery Systems in Cancer Therapy

Bacteria and bacterial components possess multifunctional properties, making them attractive natural bio-nanocarriers for cancer diagnosis and targeted treatment. The inherent tropic and motile nature of bacteria allows them to grow and colonize in hypoxic tumor microenvironments more readily than conventional therapeutic agents and other nanomedicines. However, concerns over biosafety, limited antitumor efficiency, and unclear tumor-targeting mechanisms have restricted the clinical translation and application of natural bio-nanocarriers based on bacteria and bacterial components. Fortunately, bacterial therapies combined with engineering strategies and nanotechnology may be able to reverse a number of challenges for bacterial/bacterial component-based cancer biotherapies. Meanwhile, the combined strategies tend to enhance the versatility of bionanoplasmic nanoplatforms to improve biosafety and inhibit tumorigenesis and metastasis. This review summarizes the advantages and challenges of bacteria and bacterial components in cancer therapy, outlines combinatorial strategies for nanocarriers and bacterial/bacterial components, and discusses their clinical applications.

Hypoxia-targeted and spatial-selective tumor suppression by near infrared nanoantenna sensitized engineered bacteria

It is an active research area in the development of engineered bacteria to address the bottleneck issue of hypoxic tumors, which otherwisely possess resistance to chemotherapies, radiotherapies, and photodynamic therapies. Here we report a new method to ablate hypoxic tumors with NIR-nanoantenna sensitized engineered bacteria (NASEB) in a highly effective and dual selective manner. It features engineered E. coli MG1655 (EB) with coatings of lanthanide upconversion nanoparticles (UCNPs) as external antennas on bacterial surface (MG1655/HlyE-sfGFP@UCNP@PEG), enabling NIR laser-switchable generation/secretion of HlyE perforin to kill cancer cells. We have demonstrated that NASEB enrichment on hypoxic tumor sites via their innate chemotactic tendency, in assistance of localized NIR laser irradiation, can suppress tumors with improved efficacy and selectivity, thus minimizing potential side effects in cancer treatment. The NIR-responsive nanoantenna sensitized switching in engineering bacteria is distinct from the previous reports, promising conceptually new development of therapeutics against hypoxic tumors. STATEMENT OF SIGNIFICANCE: Tumor hypoxia exacerbates tumor progression, but also reduces the efficacy of conventional chemotherapies, radiotherapies, or photodynamic therapies. Here we develop near infrared Nano Antenna Sensitized Engineered Bacteria (NASEB) to treat hypoxic tumors. NASEB can accumulate and proliferate on hypoxic tumor sites via their innate chemotactic tendency. After receiving NIR laser signals, the upconversion nanoparticles on NASEB surface as antennas can transduce them to blue light for activation of HlyE perforin in the protein factory of EB. Our method features dual selectivity on the tumor sites, contributed by hypoxic tumor homing of anaerobic bacteria and spatial confinement through selective NIR laser irradiation. The concept of NASEB promises to address the challenges of tumor hypoxia for cancer therapies.

Surface-modified bacteria: synthesis, functionalization and biomedical applications

The past decade has witnessed a great leap forward in bacteria-based living agents, including imageable probes, diagnostic reagents, and therapeutics, by virtue of their unique characteristics, such as genetic manipulation, rapid proliferation, colonization capability, and disease site targeting specificity. However, successful translation of bacterial bioagents to clinical applications remains challenging, due largely to their inherent susceptibility to environmental insults, unavoidable toxic side effects, and limited accumulation at the sites of interest. Cell surface components, which play critical roles in shaping bacterial behaviors, provide an opportunity to chemically modify bacteria and introduce different exogenous functions that are naturally unachievable. With the help of surface modification, a wide range of functionalized bacteria have been prepared over the past years and exhibit great potential in various biomedical applications. In this article, we mainly review the synthesis, functionalization, and biomedical applications of surface-modified bacteria. We first introduce the approaches of chemical modification based on the bacterial surface structure and then highlight several advanced functions achieved by modifying specific components on the surface. We also summarize the advantages as well as limitations of surface chemically modified bacteria in the applications of bioimaging, diagnosis, and therapy and further discuss the current challenges and possible solutions in the future. This work will inspire innovative design thinking for the development of chemical strategies for preparing next-generation biomedical bacterial agents.

The role of bacteria and its derived biomaterials in cancer radiotherapy

Bacteria-mediated anti-tumor therapy has received widespread attention due to its natural tumor-targeting ability and specific immune-activation characteristics. It has made significant progress in breaking the limitations of monotherapy and effectively eradicating tumors, especially when combined with traditional therapy, such as radiotherapy. According to their different biological characteristics, bacteria and their derivatives can not only improve the sensitivity of tumor radiotherapy but also protect normal tissues. Moreover, genetically engineered bacteria and bacteria-based biomaterials have further expanded the scope of their applications in radiotherapy. In this review, we have summarized relevant researches on the application of bacteria and its derivatives in radiotherapy in recent years, expounding that the bacteria, bacterial derivatives and bacteria-based biomaterials can not only directly enhance radiotherapy but also improve the anti-tumor effect by improving the tumor microenvironment (TME) and immune effects. Furthermore, some probiotics can also protect normal tissues and organs such as intestines from radiation via anti-inflammatory, anti-oxidation and apoptosis inhibition. In conclusion, the prospect of bacteria in radiotherapy will be very extensive, but its biological safety and mechanism need to be further evaluated and studied.

Prodigiosin-Functionalized Probiotic Ghosts as a Bioinspired Combination Against Colorectal Cancer Cells

Lactobacillus acidophilus ghosts (LAGs) with the unique safety of a probiotic, inherent tropism for colon cells, and multiple bioactivities offer promise as drug carriers for colon targeting. Our objective was to evaluate LAGs functionalized with prodigiosin (PG), apoptotic secondary bacterial metabolite, as a bioinspired formulation against colorectal cancer (CRC). LAGs were prepared by a chemical method and highly purified by density gradient centrifugation. LAGs were characterized by microscopic and staining techniques as relatively small-sized uniform vesicles (≈1.6 µm), nearly devoid of cytoplasmic and genetic materials and having a negatively charged intact envelope. PG was highly bound to LAGs envelope, generating a physiologically stable bioactive entity (PG-LAGs), as verified by multiple microscopic techniques and lack of PG release under physiological conditions. PG-LAGs were active against HCT116 CRC cells at both the cellular and molecular levels. Cell viability data highlighted the cytotoxicity of PG and LAGs and LAGs-induced enhancement of PG selectivity for HCT116 cells, anticipating dose reduction for PG and LAGs. Molecularly, expression of the apoptotic caspase 3 and P53 biomarkers in HCT116 intracellular proteins was significantly upregulated while that of the anti-apoptotic Bcl-2 (B-cell lymphoma 2) was downregulated by PG-LAGs relative to PG and 5-fluorouracil. PG-LAGs provide a novel bacteria-based combination for anticancer biomedicine.

Cell membrane nanomaterials composed of phospholipids and glycoproteins for drug delivery in inflammatory bowel disease: A review

Inflammatory bowel disease (IBD) is a serious chronic intestinal disorder with an increasing global incidence. However, current treatment strategies, such as anti-inflammatory drugs and probiotics, have limitations in terms of safety, stability, and effectiveness. The emergence of targeted nanoparticles has revolutionized IBD treatment by enhancing the biological properties of drugs and promoting efficiency and safety. Unlike synthetic nanoparticles, cell membrane nanomaterials (CMNs) consist primarily of biological macromolecules, including phospholipids, proteins, and sugars. CMNs include red blood cell membranes, macrophage membranes, and leukocyte membranes, which possess abundant glycoprotein receptors and ligands on their surfaces, allowing for the formation of cell-to-cell connections with other biological macromolecules. Consequently, they exhibit superior cell affinity, evade immune responses, and target inflammation effectively, making them ideal material for targeted delivery of IBD therapies. This review explores various CMNs delivery systems for IBD treatment. However, due to the complexity and harsh nature of the intestinal microenvironment, the lack of flexibility or loss of selectivity poses challenges in designing single CMNs delivery strategies. Therefore, we propose a hierarchically programmed delivery modality that combines CMNs with pH, charge, ROS and ligand-modified responsive nanoparticles. This approach significantly improves delivery efficiency and points the way for future research in this area.

Recent Advances in the Nanoshells Approach for Encapsulation of Single Probiotics

The intestine, often referred to as the "second brain" of the human body, houses a vast microbial community that plays a crucial role in maintaining the host's balance and directly impacting overall health. Probiotics, a type of beneficial microorganism, offer various health benefits when consumed. However, probiotics face challenges such as acidic conditions in the stomach, bile acids, enzymes, and other adverse factors before they can colonize the intestinal tissues. At present, pills, dry powder, encapsulation, chemically modified bacteria, and genetically engineered bacteria have emerged as the preferred method for the stable and targeted delivery of probiotics. In particular, the use of nanoshells on the surface of single probiotics has shown promise in regulating their growth and differentiation. These nanoshells can detach from the probiotics' surface upon reaching the intestine, facilitating direct contact between the probiotics and intestinal mucosa. In this perspective, we provide an overview of the current developments in the formation of nanoshells mediated by single probiotics. We also discuss the advantages and disadvantages of different nanocoating strategies and explore future trends in probiotic protection.

Knowledge Gaps in Generating Cell-Based Drug Delivery Systems and a Possible Meeting with Artificial Intelligence

Cell-based drug delivery systems are new strategies in targeted delivery in which cells or cell-membrane-derived systems are used as carriers and release their cargo in a controlled manner. Recently, great attention has been directed to cells as carrier systems for treating several diseases. There are various challenges in the development of cell-based drug delivery systems. The prediction of the properties of these platforms is a prerequisite step in their development to reduce undesirable effects. Integrating nanotechnology and artificial intelligence leads to more innovative technologies. Artificial intelligence quickly mines data and makes decisions more quickly and accurately. Machine learning as a subset of the broader artificial intelligence has been used in nanomedicine to design safer nanomaterials. Here, how challenges of developing cell-based drug delivery systems can be solved with potential predictive models of artificial intelligence and machine learning is portrayed. The most famous cell-based drug delivery systems and their challenges are described. Last but not least, artificial intelligence and most of its types used in nanomedicine are highlighted. The present Review has shown the challenges of developing cells or their derivatives as carriers and how they can be used with potential predictive models of artificial intelligence and machine learning.

Artificially engineered bacteria to treat gastrointestinal disease and cancer

Therapeutics based on living organisms provide a roadmap for next-generation biomedicine. Bacteria have an essential role in the development, regulation, and treatment of gastrointestinal disease and cancer through similar mechanisms. However, primitive bacteria lack the stability to overcome complex drug delivery barriers, and their multifunctionality in reinforcing both conventional and emerging therapeutics is limited. Artificially engineered bacteria (ArtBac) with modified surfaces and genetic functions show promise for tackling these problems. Herein, we discuss recent applications of ArtBac as living biomedicine for the treatment of gastrointestinal diseases and tumors. Future perspectives are given to guide the rational design of ArtBac toward safe multifunctional medicine.

Probiotics formulation and cancer nanovaccines show synergistic effect in immunotherapy and prevention of colon cancer

Probiotics play essential roles in immune modulation. Combining probiotics with cancer vaccines potentially can achieve a synergistic effect. To maximize the efficacy of probiotics, proper probiotics formulation is necessary. Herein, Lactobacillus rhamnosus and Bifidobacterium longum are coated with lipid membrane to achieve the goal of losing less activity and bettering colonization in colon. In the subcutaneous transplanted colon cancer mouse model, probiotics formulation showed potent preventive and therapeutic efficacy, and the efficacy could be further improved by combining with cancer nanovaccines. Probiotics formulation can perform as immune adjuvants to enhance the innate immune response or as in-situ cancer vaccines. In the study of preventing chemical-induced orthotopic colon cancer model, probiotics formulation alone efficiently reduced tumor number in colon and the efficacy is improved by combining with cancer nanovaccines. All in all, the studies demonstrated that probiotics formulation can assist to maximize the efficacy of cancer nanovaccines.

Engineered Living Materials for Advanced Diseases Therapy

Natural living materials serving as biotherapeutics exhibit great potential for treating various diseases owing to their immunoactivity, tissue targeting, and other biological activities. In this review, the recent developments in engineered living materials, including mammalian cells, bacteria, viruses, fungi, microalgae, plants, and their active derivatives that are used for treating various diseases are summarized. Further, the future perspectives and challenges of such engineered living material-based biotherapeutics are discussed to provide considerations for future advances in biomedical applications.

Synthetic engineered bacteria for cancer therapy

INTRODUCTION

Cancer mortality worldwide highlights the urgency for advanced therapeutic methods to fill the gaps in conventional cancer therapies. Bacteriotherapy is showing great potential in tumor regression due to the motility and colonization tendencies of bacteria. However, the complicated in vivo environment and tumor pathogenesis hamper the therapeutic outcomes. Synthetic engineering methods endow bacteria with flexible abilities both at the extracellular and intracellular levels to meet treatment requirements. In this review, we introduce synthetic engineering methods for bacterial modifications. We highlight the recent progress in engineered bacteria and explore how these synthetic methods endow bacteria with superior abilities in cancer therapy. The current clinical translations are further discussed. Overall, this review may shed light on the advancement of engineered bacteria for cancer therapy.

AREAS COVERED

Recent progress in synthetic methods for bacterial engineering and specific examples of their applications in cancer therapy are discussed in this review.

EXPERT OPINION

Bacteriotherapy bridges the gaps of conventional cancer therapies through the natural motility and colonization tendency of bacteria, as well as their synthetic engineering. Nevertheless, to fulfill the bacteriotherapy potential and move into clinical trials, more research focusing on its safety concerns should be conducted.

Aggregation-Induced Emission Photosensitizer/Bacteria Biohybrids Enhance Cerenkov Radiation-Induced Photodynamic Therapy by Activating Anti-Tumor Immunity for Synergistic Tumor Treatment

Cerenkov radiation-induced photodynamic therapy (CR-PDT) gets rid of the limited tissue penetration depth of the external light source and provides a feasible scheme for the PDT excited by the internal light. However, due to the low luminescence intensity of Cerenkov radiation, CR-PDT alone cannot effectively inhibit tumor growth, curbing the potential clinical translation of CR-PDT. Herein, we reported an AIE-PS/bacteria biohybrid (EcN@TTVP) composed of Escherichia coli Nissle 1917 (EcN) loaded with aggregation-induced emission photosensitizer (AIE-PS) termed TTVP, which enhanced CR-PDT by activating anti-tumor immunity for synergistic tumor treatment. The preferential tumor-colonized EcN@TTVP and radiopharmaceutical ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) were administered sequentially to enable them to co-enrich in the tumor site, thereby triggering CR-PDT and promoting immunogenic tumor cell death. Most importantly, EcN acting as immunoadjuvants enhanced the maturation of dendritic cells (DCs) and priming of cytotoxic T cells (CTLs). Therefore, under the synergistic treatment of CR-PDT and immunotherapy, AIE-PS/bacteria biohybrids resulted in either efficient tumor remission or a survival prolongation in tumor-bearing mice, which presented significant advantages over single CR-PDT. Remarkably, no obvious toxic effects were observed during the treatment. In this study, we proposed a synergistic therapeutic strategy based on EcN@TTVP for combined CR-PDT and immunotherapy against tumors. Moreover, this strategy may have great potential in clinical translation and provide references for deep-seated tumor treatment. STATEMENT OF SIGNIFICANCE: PDT is restricted due to the shallow penetration depth of light into tumor tissues. Using CR as the excitation light source for PDT can overcome the aforementioned issue and greatly expand the application of PDT. However, the low efficacy of single CR-PDT limits further its applications. Therefore, the design and development of feasible strategies to improve the efficacy of CR-PDT are of immediate importance. Introducing probiotics to our study can be used not only as tumor-targeting carriers of photosensitizers but also as immunoadjuvants. Under co-stimulation by immunogenic tumor cell death triggered by CR-PDT and probiotics acting as immunoadjuvants, anti-tumor immune responses were effectively activated, thus remarkably enhancing the efficacy of CR-PDT.