Inactive Trojan Bacteria as Safe Drug Delivery Vehicles Crossing the Blood-Brain Barrier

Living therapeutics: Precision diagnosis and therapy with engineered bacteria

Bacteria-based therapy has emerged as a promising strategy for cancer treatment, offering the potential for targeted tumor delivery, immune activation, and modulation of the tumor microenvironment. However, the unpredictable behavior, safety concerns, and limited efficacy of wild-type bacteria pose significant challenges to their clinical translation. Recent advancements in synthetic biology and chemical engineering have enabled the development of precisely engineered bacterial platforms with enhanced controllability, targeted delivery, and reduced toxicity. This review summarize the current progress of engineered bacteria in cancer therapy. We first introduce the theoretical underpinnings and key advantages of bacterial therapies in cancer. Subsequently, we delve into the applications of genetic engineering and chemical modification techniques to enhance their therapeutic potential. Finally, we address critical challenges and future prospects, with a focus on improving safety and efficacy. This review aims to stimulate further research and provide valuable insights into the development of engineered bacterial therapies for precision oncology.

Breaking the fortress: a mechanistic review of meningitis-causing bacteria breaching tactics in blood brain barrier

The blood-brain barrier is a physiological protective barrier around blood vessels in the brain. It prevents most bacteria and harmful substances from entering the brain through the blood. However, when bacterial meningitis occurs, bacteria enter the brain either from the circulation or by direct invasion from neighbouring structures, causing an inflammatory response that in severe cases may lead to death. High morbidity and mortality are prominent features of the disease. Many pathogenic bacteria can break through the blood-brain barrier and cause meningitis, such as Streptococcus pneumoniae, Group B Streptococcus, Streptococcus suis, Neisseria meningitidis, meningitis-associated Escherichia coli, etc. This article reviews the mechanisms by which these bacteria cross the blood-brain barrier when causing meningitis and the interactions between bacteria and host cells to help pathogens invade the brain. Clarifying the mechanism by which pathogens cross the blood-brain barrier can provide new ideas for developing effective treatments for bacterial meningitis.

Nanoarchitecting intelligently encapsulated designs for improved cancer therapy

Despite the success in exploring various aspects of origination and therapeutic strategies, cancer has remained one of the most dreadful metabolic disorders due to failure to eradicate tumors comprehensively and frequent recurrence because of acquired resistance to the drugs. Recently, several advancements have been evidenced in the fabrication of various smart nanocarriers encapsulated with multiple components. Several reasons for smart nanoencapsulation include the enhancement of the bioavailability of drugs, precise targetability to reduce adverse effects on normal cells, and the ability to enable controlled drug release rates at the tumor sites. In addition, these smart nanocarriers protect encapsulated therapeutic cargo from deactivation, responsively delivering it based on the physiological or pathological characteristics of tumors. In this review, we present various smart approaches for cancer therapy, including organic materials, inorganic components, and their composites, as well as biomembrane-based nanoencapsulation strategies. These nanoencapsulation strategies, along with practical applications and their potential in cancer treatment, are discussed in depth, highlighting advantages and disadvantages, as well as aiming to reveal the ultimate prospects of nanoencapsulation in enhancing drug delivery efficiency and targeted cancer therapy.

Escherichia coli combination with PD-1 blockade synergistically enhances immunotherapy in glioblastoma multiforme by regulating the immune cells

BACKGROUND

Glioblastoma multiforme (GBM) is the most common and aggressive primary intracranial malignancy. It is characterized by insufficient infiltration of anti-tumor T lymphocytes within the tumor microenvironment (TME), rendering it an "immune cold" disease. This immune deficiency results in poor responses to immune checkpoint blockade (ICB) therapies. Recent studies have demonstrated that bacteria can proliferate within tumors and activate immune responses. Therefore, in this study, we employed Escherichia coli (E. coli) in combination with anti-PD-1 antibodies to treat GBM, with the aim of exploring the immune-activating potential of E. coli in GBM and its synergistic effect on anti-PD-1 therapy.

METHODS

The E. coli and anti-PD-1 antibody therapy were administered intravenously and intraperitoneally, respectively. Complete blood cell count, blood biochemical analysis, hematoxylin and eosin (H&E) staining, and agar plate culture were employed to evaluate the biosafety and tumor-targeting capability of E. coli. ELISA kits were used to detect innate immune cytokines. Flow cytometry and immunofluorescence staining were used to investigate T cells. Tumor volume of tumor-bearing mice was recorded to evaluate the combined treatment efficacy. H&E staining and immunofluorescence staining were used to observe the tumor inhibition markers.

RESULTS

E.coli can specifically target into the tumor region, and activate the innate immune response in mice. Immunofluorescence staining and flow cytometry results demonstrated that the combination treatment group exhibited a significant upregulation of cytotoxic CD8+ T cells and a marked suppression of regulatory T cells compared to the control group. The expression of Ki67 was significantly downregulated, and TUNEL staining revealed an increased number of apoptotic cells in the combination treatment group. Furthermore, the tumor growth rate in the combination treatment group was significantly slower than that in the control group.

CONCLUSIONS

E. coli exhibits potential anti-tumor activity and can activate the innate immune response and further regulate immune cells in the tumor tissues to synergize the effect of anti-PD-1 therapy on GBM, providing new insights to enhance the efficacy of GBM immunotherapy.

Nanorobots mediated drug delivery for brain cancer active targeting and controllable therapeutics

Brain cancer pose significant life-threats by destructively invading normal brain tissues, causing dysneuria, disability and death, and its therapeutics is limited by underdosage and toxicity lying in conventional drug delivery that relied on passive delivery. The application of nanorobots-based drug delivery systems is an emerging field that holds great potential for brain cancer active targeting and controllable treatment. The ability of nanorobots to encapsulate, transport, and supply therapies directly to the lesion site through blood-brain barriers makes it possible to deliver drugs to hard-to-reach areas. In order to improve the efficiency of drug delivery and problems such as precision and sustained release, nanorobots are effectively realized by converting other forms of energy into propulsion and motion, which are considered as high-efficiency methods for drug delivery. In this article, we described recent advances in the treatment of brain cancer with nanorobots mainly from three aspects: firstly, the development history and characteristics of nanorobots are reviewed; secondly, recent research progress of nanorobots in brain cancer is comprehensively investigated, like the driving mode and mechanism of nanorobots are described; thirdly, the potential translation of nanorobotics for brain diseases is discussed and the challenges and opportunities for future research are outlined.

Transvascular transport of nanocarriers for tumor delivery

Nanocarriers (NCs) play a crucial role in delivering theranostic agents to tumors, making them a pivotal focus of research. However, the persistently low delivery efficiency of engineered NCs has been a significant challenge in the advancement of nanomedicine, stirring considerable debate. Transvascular transport is a critical pathway for NC delivery from vessels to tumors, yet a comprehensive understanding of the interactions between NCs and vascular systems remains elusive. In recent years, considerable efforts have been invested in elucidating the transvascular transport mechanisms of NCs, leading to promising advancements in tumor delivery and theranostics. In this context, we highlight various delivery mechanisms, including the enhanced permeability and retention effect, cooperative immune-driven effect, active transcytosis, and cell/bacteria-mediated delivery. Furthermore, we explore corresponding strategies aimed at enhancing transvascular transport of NCs for efficient tumor delivery. These approaches offer intriguing solutions spanning physicochemical, biological, and pharmacological domains to improve delivery and therapeutic outcomes. Additionally, we propose a forward-looking delivery framework that relies on advanced tumor/vessel models, high-throughput NC libraries, nano-bio interaction datasets, and artificial intelligence, which aims to guide the design of next-generation carriers and implementation strategies for optimized delivery.

Smart delivery vehicles for cancer: categories, unique roles and therapeutic strategies

Chemotherapy and surgery remain the primary treatment modalities for cancers; however, these techniques have drawbacks, such as cancer recurrence and toxic side effects, necessitating more efficient cancer treatment strategies. Recent advancements in research and medical technology have provided novel insights and expanded our understanding of cancer development; consequently, scholars have investigated several delivery vehicles for cancer therapy to improve the efficiency of cancer treatment and patient outcomes. Herein, we summarize several types of smart therapeutic carriers and elaborate on the mechanism underlying drug delivery. We reveal the advantages of smart therapeutic carriers for cancer treatment, focus on their effectiveness in cancer immunotherapy, and discuss the application of smart cancer therapy vehicles in combination with other emerging therapeutic strategies for cancer treatment. Finally, we summarize the bottlenecks encountered in the development of smart cancer therapeutic vehicles and suggest directions for future research. This review will promote progress in smart cancer therapy and facilitate related research.

Ameliorating Mitochondrial Dysfunction for the Therapy of Parkinson's Disease

Parkinson's disease (PD) is currently the second most incurable central neurodegenerative disease resulting from various pathogenesis. As the "energy factory" of cells, mitochondria play an extremely important role in supporting neuronal signal transmission and other physiological activities. Mitochondrial dysfunction can cause and accelerate the occurrence and progression of PD. How to effectively prevent and suppress mitochondrial disorders is a key strategy for the treatment of PD from the root. Therefore, the emerging mitochondria-targeted therapy has attracted considerable interest. Herein, the relationship between mitochondrial dysfunction and PD, the causes and results of mitochondrial dysfunction, and major strategies for ameliorating mitochondrial dysfunction to treat PD are systematically reviewed. The study also prospects the main challenges for the treatment of PD.

Programmed Nanocloak of Commensal Bacteria-Derived Nanovesicles Amplify Strong Immunoreactivity against Tumor Growth and Metastatic Progression

Recent discoveries in commensal microbiota demonstrate the great promise of intratumoral bacteria as attractive molecular targets of tumors in improving cancer treatment. However, direct leveraging of in vivo antibacterial strategies such as antibiotics to potentiate cancer therapy often leads to uncertain effectiveness, mainly due to poor selectivity and potential adverse effects. Here, building from the clinical discovery that patients with breast cancer featured rich commensal bacteria, we developed an activatable biointerface by encapsulating commensal bacteria-derived extracellular vesicles (BEV) with a responsive nanocloak to potentiate immunoreactivity against intratumoral bacteria and breast cancer. We show that the interfacially cloaked BEV (cBEV) not only overcame serious systemic side responses but also demonstrated heightened immunogenicity by intercellular responsive immunogenicity, facilitating dendritic cell maturation through activating the cGAS-STING pathway. As a preventive measure, vaccination with nanocloaked cBEVs achieved strong protection against bacterial infection, largely providing prophylactic efficiency against tumor challenges. When treated in conjunction with immune checkpoint inhibitor anti-PD-L1 antibodies, the combined approach elicited a potent tumor-specific immune response, synergistically inhibiting tumor progression and mitigating lung metastases.

Neutrophil hitchhiking nanoparticles enhance bacteria-mediated cancer therapy via NETosis reprogramming

Bacteria have shown great potential in anti-tumor treatment, and an attenuated strain of Salmonella named VNP20009 has been shown to be safe in clinical trials. However, colonized bacteria recruit neutrophils into the tumor, which release NETs to capture and eliminate bacteria, compromising bacterial-based tumor treatment. In this study, we report a neutrophil hitchhiking nanoparticles (SPPS) that block the formation of NET to enhance bacteria-mediated tumor therapy. In the 4 T1 tumor-bearing mouse model, following 24 h of bacterial therapy, there was an approximately 3.0-fold increase in the number of neutrophils in the bloodstream, while the amount of SPPS homing to tumor tissue through neutrophil hitchhiking increased approximately 2.0-fold. It is worth noting that the NETs in tumors significantly decreased by approximately 2.0-fold through an intracellular ROS scavenging-mediated NETosis reprogramming, thereby increasing bacterial vitality by 1.9-fold in tumors. More importantly, the gene drug (siBcl-2) loaded in SPPS can be re-encapsulated in apoptotic bodies by reprogramming neutrophils from NETosis to apoptosis, and enable the redelivery of drugs to tumor cells, further boosting the antitumor efficacy with a synergistic effect, resulting in about 98% tumor inhibition rate and 90% survival rate.

Genetically engineered probiotics for an optical imaging-guided tumor photothermal therapy/immunotherapy

Bacteria-based cancer therapy (BCT) has been extensively investigated because of the tumor targeting and antitumor immunity activating abilities of bacteria over traditional nanodrugs, but their potential systemic toxicity poses a challenge. Therefore, it is important to visualize the precise localization and real-time distribution of bacteria in vivo to guide the treatment. Herein, biogenetically engineered Escherichia coli Nissle 1917 (EcN) were constructed to highly express tyrosinase to intracellularly generate cyanine 5-labeled melanin-like polymers (Cy5-Mel), thus endowing them with a bright fluorescence and an excellent photothermal performance upon NIR laser irradiation, thereby inducing the intense immunogenic death of tumor cells and release of tumor-associated antigens. Acting as adjuvants, bacteria can greatly stimulate the maturation of dendritic (DC) cells. The in vivo behaviors of these bacteria was monitored via noninvasive optical imaging when they were intravenously administrated to tumor-bearing mice. From this, NIR exposure on tumor sites was carried out at an appropriate time point to induce the damage to tumor cells and for the modulation of tumor immune microenvironments. Thus, via a simple bioengineering strategy, a promising bacteria-based theranostic platform was constructed for tumor treatment.

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.