Bacteria-driven hypoxia targeting delivery of chemotherapeutic drug proving outcome of breast cancer

Inspired by nature: Bioluminescent systems for bioimaging applications

Bioluminescence is a natural process where biological organisms produce light through chemical reactions. These reactions predominantly occur between small-molecule substrates and luciferase within bioluminescent organisms. Bioluminescence imaging (BLI) has shown significant potential in biomedical research owing to its non-invasive, real-time observation and quantification. In this review, we introduced the chemical mechanism of bioluminescent systems and categorized several strategies that successfully addressed the native limitations, including improvements on the chemical structures of luciferase-luciferin bioluminescence system and bioluminescence resonance energy transfer (BRET) methods. In addition, we also reviewed and summarized recent advances in bioimaging applications. We hope that this review can provide effective guidance for the development and application of bioluminescent systems in the field of bioimaging.

The application of bacteria-nanomaterial hybrids in antitumor therapy

Adverse effects and multidrug resistance remain significant obstacles in conventional cancer therapy. Nanomedicines, with their intrinsic properties such as nano-sized dimensions and tunable surface characteristics, have the potential to mitigate the side effects of traditional cancer treatments. While nanomaterials have been widely applied in cancer treatment, challenges such as low targeting efficiency and poor tumor penetration persist. Recent research has shown that anaerobic bacteria exhibit high selectivity for primary tumors and metastatic cancers, offering good safety and superior tumor penetration capabilities. This suggests that combining nanomaterials with bacteria could complement their respective limitations, opening vast potential applications in cancer therapy. The use of bacteria in combination with nanomaterials for anticancer treatments, including chemotherapy, radiotherapy, and photothermal/photodynamic therapy, has contributed to the rapid development of the field of bacterial oncology treatments. This review explores the mechanisms of bacterial tumor targeting and summarizes strategies for synthesizing bacterial-nanomaterial and their application in cancer therapy. The combination of bacterial-nanomaterial hybrids with modern therapeutic approaches represents a promising avenue for future cancer treatment research, with the potential to improve treatment outcomes for cancer patients.

Path to bacteriotherapy: From bacterial engineering to therapeutic perspectives

The major reason for the failure of conventional therapies is the heterogeneity and complexity of tumor microenvironments (TMEs). Many malignant tumors reprogram their surface antigens to evade the immune surveillance, leading to reduced antigen-presenting cells and hindered T-cell activation. Bacteria-mediated cancer immunotherapy has been extensively investigated in recent years. Scientists have ingeniously modified bacteria using synthetic biology and nanotechnology to enhance their biosafety with high tumor specificity, resulting in robust anticancer immune responses. To enhance the antitumor efficacy, therapeutic proteins, cytokines, nanoparticles, and chemotherapeutic drugs have been efficiently delivered using engineered bacteria. This review provides a comprehensive understanding of oncolytic bacterial therapies, covering bacterial design and the intricate interactions within TMEs. Additionally, it offers an in-depth comparison of the current techniques used for bacterial modification, both internally and externally, to maximize their therapeutic effectiveness. Finally, we outlined the challenges and opportunities ahead in the clinical application of oncolytic bacterial therapies.

Harnessing and Mimicking Bacterial Features to Combat Cancer: From Living Entities to Artificial Mimicking Systems

Bacterial-derived micro-/nanomedicine has garnered considerable attention in anticancer therapy, owing to the unique natural features of bacteria, including specific targeting ability, immunogenic benefits, physicochemical modifiability, and biotechnological editability. Besides, bacterial components have also been explored as promising drug delivery vehicles. Harnessing these bacterial features, cutting-edge physicochemical and biotechnologies have been applied to attenuated tumor-targeting bacteria with unique properties or functions for potent and effective cancer treatment, including strategies of gene-editing and genetic circuits. Further, the advent of bacteria-inspired micro-/nanorobots and mimicking artificial systems has furnished fresh perspectives for formulating strategies for developing highly efficient drug delivery systems. Focusing on the unique natural features and advantages of bacteria, this review delves into advances in bacteria-derived drug delivery systems for anticancer treatment in recent years, which has experienced a process from living entities to artificial mimicking systems. Meanwhile, a summary of relative clinical trials is provided and primary challenges impeding their clinical application are discussed. Furthermore, future directions are suggested for bacteria-derived systems to combat cancer.

Insights into the enigma of oral streptococci in carcinogenesis

SUMMARYThe genus Streptococcus consists of a taxonomically diverse group of Gram-positive bacteria that have earned significant scientific interest due to their physiological and pathogenic characteristics. Within the genus Streptococcus, viridans group streptococci (VGS) play a significant role in the oral ecosystem, constituting approximately 80% of the oral biofilm. Their primary role as pioneering colonizers in the oral cavity with multifaceted interactions like adherence, metabolic signaling, and quorum sensing contributes significantly to the complex dynamics of the oral biofilm, thus shaping oral health and disease outcomes. Perturbations in oral streptococci composition drive oral dysbiosis and therefore impact host-pathogen interactions, resulting in oral inflammation and representing VGS as an opportunistic pathogen. The association of oral streptococci in tumors across distant organs, spanning the esophagus, stomach, pancreas, and colon, illuminates a potential association between oral streptococci, inflammation, and tumorigenesis. This finding emphasizes the need for further investigations into the role of oral streptococci in mucosal homeostasis and their involvement in carcinogenesis. Hence, here, we review the significance of oral streptococci in biofilm dynamics and how the perturbation may impact mucosal immunopathogenesis in the context of cancer, with a vision of exploiting oral streptococci for cancer intervention and for the development of non-invasive cancer diagnosis.

An oral bioactive chitosan-decorated doxorubicin nanoparticles/bacteria bioconjugates enhance chemotherapy efficacy in an in-situ breast cancer model

Breast cancer is the second leading cause of cancer-related deaths among women worldwide. Despite significant advancements in chemotherapy, its effectiveness is often limited by poor drug distribution and systemic toxicity caused by the weak targeting ability of conventional therapeutic agents. The hypoxic tumor microenvironment (TME) also plays a vital role in treatment outcomes. Oral anticancer therapeutic agents have gained popularity and show promising results due to their ease of repeated administration. This study introduces autopilot biohybrids (Bif@BDC-NPs) for the effective delivery of doxorubicin (DOX) to the tumor site. This hybrid combines albumin-encapsulated DOX nanoparticles (BD-NPs) coated with chitosan (CS) for breast cancer chemotherapy, along with anaerobic Bifidobacterium infantis (B. infantis, Bif) serving as self-propelled motors. Due to Bif's specific anaerobic properties, Bif@BDC-NPs precisely anchor hypoxic regions of tumor tissue and significantly increase drug accumulation at the tumor site, thereby promoting tumor cell death. In an in-situ mouse breast cancer model, Bif@BDC-NPs achieved 94 % tumor inhibition, significantly prolonging the median survival of mice to 62 days, and reducing the toxic side effects of DOX. Therefore, the new bacteria-driven oral drug delivery system, Bif@BDC-NPs, overcomes multiple physiological barriers and holds great potential for the precise treatment of solid tumors.

Long-Term Tumor-Targeting Effect of E. coli as a Drug Delivery System

To overcome the limitations of current nano/micro-scale drug delivery systems, an Escherichia coli (E. coli)-based drug delivery system could be a potential alternative, and an effective tumor-targeting delivery system can be developed by attempting to perform chemical binding to the primary amine group of a cell membrane protein. In addition, positron emission tomography (PET) is a representative non-invasive imaging technology and is actively used in the field of drug delivery along with radioisotopes capable of long-term tracking, such as zirconium-89 (89Zr). The membrane proteins were labeled with 89Zr using chelate (DFO), and not only was the long-term biodistribution in tumors and major organs evaluated in the body, but the labeling stability of 89Zr conjugated to the membrane proteins was also evaluated through continuous tracking. E. coli accumulated at high levels in the tumor within 5 min (initial time) after tail intravenous injection, and when observed after 6 days, 89Zr-DFO on the surface of E. coli was found to be stable for a long period of time in the body. In this study, we demonstrated the long-term biodistribution and tumor-targeting effect of an E. coli-based drug delivery system and verified the in vivo stability of radioisotopes labeled on the surface of E. coli.

Towards overcoming obstacles of type II photodynamic therapy: Endogenous production of light, photosensitizer, and oxygen

Conventional photodynamic therapy (PDT) approaches face challenges including limited light penetration, low uptake of photosensitizers by tumors, and lack of oxygen in tumor microenvironments. One promising solution is to internally generate light, photosensitizers, and oxygen. This can be accomplished through endogenous production, such as using bioluminescence as an endogenous light source, synthesizing genetically encodable photosensitizers in situ, and modifying cells genetically to express catalase enzymes. Furthermore, these strategies have been reinforced by the recent rapid advancements in synthetic biology. In this review, we summarize and discuss the approaches to overcome PDT obstacles by means of endogenous production of excitation light, photosensitizers, and oxygen. We envision that as synthetic biology advances, genetically engineered cells could act as precise and targeted "living factories" to produce PDT components, leading to enhanced performance of PDT.

Doxorubicin-Loaded Microalgal Delivery System for Combined Chemotherapy and Enhanced Photodynamic Therapy of Osteosarcoma

Osteosarcoma (OS) is considered the most frequent type of primary malignant bone tumor. Currently, radiotherapy, photodynamic (PDT), and other therapies for osteosarcoma are limited by tumor hypoxia and single efficacy and serve side-effects. Herein, we reported a microalgal drug delivery system (SpiD), doxorubicin (DOX)-loaded Spirulina platensis (Spi) for OS therapy. The specific surface of Spirulina platensis allowed for effective loading of DOX via surface channels and electrostatic interactions. Under 650 nm laser irradiation, SpiD enabled high oxygen production by photosynthesis and enhanced reactive oxygen species (ROS) generation via chlorophyll-assisted photosensitization, synergistically killing tumor cells with the released DOX. Combined chemotherapy and enhanced PDT mediated by SpiD exerted synergic antitumor effects and resulted in potent therapeutic efficacy in orthotopic osteosarcoma mice. Furthermore, SpiD could reduce the side-effects of chemotherapy, showing excellent blood and tissue safety. Taken together, this microalgal drug delivery system provided a natural, efficient, safe, and inexpensive strategy for OS treatment.

Albumin conjugation promotes arsenic trioxide transport through alkaline phosphatase-associated transcytosis in MUC4 wildtype pancreatic cancer cells

Pancreatic cancer (PC) has a poor prognosis due to chemotherapy resistance and unfavorable drug transportation. Albumin conjugates are commonly used as drug carriers to overcome these obstacles. However, membrane-bound glycoprotein mucin 4 (MUC4) has emerged as a promising biomarker among the genetic mutations affecting albumin conjugates therapeutic window. Human serum albumin-conjugated arsenic trioxide (HSA-ATO) has shown potential in treating solid tumors but is limited in PC therapy due to unclear targets and mechanisms. This study investigated the transport mechanisms and therapeutic efficacy of HSA-ATO in PC cells with different MUC4 mutation statuses. Results revealed improved penetration of ATO into PC tumors through conjugated with HSA. However, MUC4 mutation significantly affected treatment sensitivity and HSA-ATO uptake both in vitro and in vivo. Mutant MUC4 cells exhibited over ten times higher IC50 for HSA-ATO and approximately half the uptake compared to wildtype cells. Further research demonstrated that ALPL activation by HSA-ATO enhanced transcytosis in wildtype MUC4 PC cells but not in mutant MUC4 cells, leading to impaired uptake and weaker antitumor effects. Reprogramming the transport process holds potential for enhancing albumin conjugate efficacy in PC patients with different MUC4 mutation statuses, paving the way for stratified treatment using these delivery vehicles.

Bacteria-Based Nanoprobes for Cancer Therapy

Surgical removal together with chemotherapy and radiotherapy has used to be the pillars of cancer treatment. Although these traditional methods are still considered as the first-line or standard treatments, non-operative situation, systemic toxicity or resistance severely weakened the therapeutic effect. More recently, synthetic biological nanocarriers elicited substantial interest and exhibited promising potential for combating cancer. In particular, bacteria and their derivatives are omnipotent to realize intrinsic tumor targeting and inhibit tumor growth with anti-cancer agents secreted and immune response. They are frequently employed in synergistic bacteria-mediated anticancer treatments to strengthen the effectiveness of anti-cancer treatment. In this review, we elaborate on the development, mechanism and advantage of bacterial therapy against cancer and then systematically introduce the bacteria-based nanoprobes against cancer and the recent achievements in synergistic treatment strategies and clinical trials. We also discuss the advantages as well as the limitations of these bacteria-based nanoprobes, especially the questions that hinder their application in human, exhibiting this novel anti-cancer endeavor comprehensively.

Cell-Based Micro/Nano-Robots for Biomedical Applications: A Review

Micro/nano-robots are powerful tools for biomedical applications and are applied in disease diagnosis, tumor imaging, drug delivery, and targeted therapy. Among the various types of micro-robots, cell-based micro-robots exhibit unique properties because of their different cell sources. In combination with various actuation methods, particularly externally propelled methods, cell-based microrobots have enormous potential for biomedical applications. This review introduces recent progress and applications of cell-based micro/nano-robots. Different actuation methods for micro/nano-robots are summarized, and cell-based micro-robots with different cell templates are introduced. Furthermore, the review focuses on the combination of cell-based micro/nano-robots with precise control using different external fields. Potential challenges, further prospects, and clinical translations are also discussed.

Self-driven bioactive hybrids co-deliver doxorubicin and indocyanine green nanoparticles for chemo/photothermal therapy of breast cancer

Breast cancer is characterized by insidious onset, rapid progression, easy recurrence, and metastasis. Conventional monotherapies are usually ineffective due to insufficient drug delivery. Therefore, the combination of multimodal therapy with tumor microenvironment (TME)-responsive nanoplatforms is increasingly being considered for the targeted treatment of breast cancer. We synthesized bioactive hybrid nanoparticles for synergistic chemotherapy and photothermal therapy. Briefly, doxorubicin (DOX) and indocyanine green (ICG)-loaded nanoparticles (DI) of average particle size 113.58 ± 2.14 nm were synthesized, and their surface were modified with polydopamine (PDA) and attached to the anaerobic probiotic Bifidobacterium infantis (Bif). The bioactive Bif@DIP hybrid showed good photothermal conversion efficiency of about 38.04%. In addition, the self-driving ability of Bif allowed targeted delivery of the PDA-coated DI nanoparticles (DIP) to the hypoxic regions of the tumor. The low pH and high GSH levels in the TME stimulated the controlled release of DOX and ICG from the Bif@DIP hybrid, which then triggered apoptosis of tumor cells and induced immunogenic cell death (ICD), resulting in effective and sustained anti-tumor effect with minimum systemic toxicity. Thus, the self-driven Bif@DIP hybrid is a promising nanodrug for the targeted chemotherapy and photothermal therapy against solid cancers.

Nano/Micromotors for Cancer Diagnosis and Therapy: Innovative Designs to Improve Biocompatibility

Nano/micromotors are artificial robots at the nano/microscale that are capable of transforming energy into mechanical movement. In cancer diagnosis or therapy, such "tiny robots" show great promise for targeted drug delivery, cell removal/killing, and even related biomarker sensing. Yet biocompatibility is still the most critical challenge that restricts such techniques from transitioning from the laboratory to clinical applications. In this review, we emphasize the biocompatibility aspect of nano/micromotors to show the great efforts made by researchers to promote their clinical application, mainly including non-toxic fuel propulsion (inorganic catalysts, enzyme, etc.), bio-hybrid designs, ultrasound propulsion, light-triggered propulsion, magnetic propulsion, dual propulsion, and, in particular, the cooperative swarm-based strategy for increasing therapeutic effects. Future challenges in translating nano/micromotors into real applications and the potential directions for increasing biocompatibility are also described.

Salmonella immunotherapy engineered with highly efficient tumor antigen coating establishes antigen-specific CD8+ T cell immunity and increases in antitumor efficacy with type I interferon combination therapy

Bacteria-based cancer therapy employs various strategies to combat tumors, one of which is delivering tumor-associated antigen (TAA) to generate specific immunity. Here, we utilized a poly-arginine extended HPV E7 antigen (9RE7) for attachment on Salmonella SL7207 outer membrane to synthesize the bacterial vaccine Salmonella-9RE7 (Sal-9RE7), which yielded a significant improvement in the amount of antigen presentation compared to the previous lysine-extended antigen coating strategy. In TC-1 tumor mouse models, Sal-9RE7 monotherapy decreased tumor growth by inducing E7 antigen-specific immunity. In addition, pairing Sal-9RE7 with adjuvant Albumin-IFNβ (Alb-IFNβ), a protein cytokine fusion, the combination significantly increased the antitumor efficacy and enhanced immunogenicity in the tumor microenvironment (TME). Our study made a significant contribution to personalized bacterial immunotherapy via TAA delivery and demonstrated the advantage of combination therapy.

Bacteria-driven cancer therapy: Exploring advancements and challenges

Cancer, a serious fatal disease caused by the uncontrolled growth of cells, is the biggest challenge flagging around medicine and health fields. Conventionally, various treatments-based strategies such as radiotherapy, chemotherapy, and alternative cancer therapies possess drugs that cannot reach the cancerous tissues and make them toxic to noncancerous cells. Cancer immunotherapy has made outstanding achievements in reducing the chances of cancer. Our considerable attention towards cancer-directed immune responses and the mechanisms behind which immune cells kill cancer cells have progressively been helpful in the advancement of new therapies. Among them, bacteria-based cancer immunotherapy has achieved much more attention due to smart and robust mechanisms in activating the host anti-tumor response. Moreover, bacterial-based therapy can be utilized as a single monotherapy or in combination with multiple anticancer immunotherapies to accelerate productive clinical results. Herein, we comprehensively reviewed recent advancements, challenges, and future perspectives in developing bacterial-based cancer immunotherapies.

Revolutionizing cancer treatment: The power of cell-based drug delivery systems

Intravenous administration of drugs is a widely used cancer therapy approach. However, the efficacy of these drugs is often hindered by various biological barriers, including circulation, accumulation, and penetration, resulting in poor delivery to solid tumors. Recently, cell-based drug delivery platforms have emerged as promising solutions to overcome these limitations. These platforms offer several advantages, including prolonged circulation time, active targeting, controlled release, and excellent biocompatibility. Cell-based delivery systems encompass cell membrane coating, intracellular loading, and extracellular backpacking. These innovative platforms hold the potential to revolutionize cancer diagnosis, monitoring, and treatment, presenting a plethora of opportunities for the advancement and integration of pharmaceuticals, medicine, and materials science. Nevertheless, several technological, ethical, and financial barriers must be addressed to facilitate the translation of these platforms into clinical practice. In this review, we explore the emerging strategies to overcome these challenges, focusing specifically on the functions and advantages of cell-mediated drug delivery in cancer treatment.

Hacking the Immune Response to Solid Tumors: Harnessing the Anti-Cancer Capacities of Oncolytic Bacteria

Oncolytic bacteria are a classification of bacteria with a natural ability to specifically target solid tumors and, in the process, stimulate a potent immune response. Currently, these include species of Klebsiella, Listeria, Mycobacteria, Streptococcus/Serratia (Coley's Toxin), Proteus, Salmonella, and Clostridium. Advancements in techniques and methodology, including genetic engineering, create opportunities to "hijack" typical host-pathogen interactions and subsequently harness oncolytic capacities. Engineering, sometimes termed "domestication", of oncolytic bacterial species is especially beneficial when solid tumors are inaccessible or metastasize early in development. This review examines reported oncolytic bacteria-host immune interactions and details the known mechanisms of these interactions to the protein level. A synopsis of the presented membrane surface molecules that elicit particularly promising oncolytic capacities is paired with the stimulated localized and systemic immunogenic effects. In addition, oncolytic bacterial progression toward clinical translation through engineering efforts are discussed, with thorough attention given to strains that have accomplished Phase III clinical trial initiation. In addition to therapeutic mitigation after the tumor has formed, some bacterial species, referred to as "prophylactic", may even be able to prevent or "derail" tumor formation through anti-inflammatory capabilities. These promising species and their particularly favorable characteristics are summarized as well. A complete understanding of the bacteria-host interaction will likely be necessary to assess anti-cancer capacities and unlock the full cancer therapeutic potential of oncolytic bacteria.

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.

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.

Dual mode imaging guided multi-functional bio-targeted oxygen production probes for tumor therapy

Focused ultrasound ablation surgery (FUAS) is a novel therapy with a wide range of potential applications. However, synergists are crucial to the therapy process due to the ultrasonic energy's attenuation properties. As a result of the complex hypoxic environment in the tumor area and many factors, the existing synergists have limitations such as weak targeting, single imaging mode, and easy tumor recurrence after treatment. Because of the above deficiencies, this study intends to construct bio-targeted oxygen production probes consisting of Bifidobacterium that naturally target the hypoxia region of the tumor and multi-functional oxygen-producing nanoparticles equipped with IR780, perfluorohexane (PFH), CBP (carboplatin), and oxygen. The probes are expected to achieve targeted and synergistic FUAS therapy and dual-mode imaging to mediate tumor diagnosis and treatment. The oxygen and drugs carried in it are accurately released after FUAS stimulation, which is expected to alleviate tumor hypoxia, avoid tumor drug resistance, improve the effect of chemotherapy, and realize FUAS combined with chemotherapy antitumor therapy. This strategy is expected to make up for the deficiencies of existing synergists, improve the effectiveness and safety of treatment, and provide the foundation for future tumor therapy progress.

Bacterial-Mediated Tumor Therapy: Old Treatment in a New Context

Targeted therapy and immunotherapy have brought hopes for precision cancer treatment. However, complex physiological barriers and tumor immunosuppression result in poor efficacy, side effects, and resistance to antitumor therapies. Bacteria-mediated antitumor therapy provides new options to address these challenges. Thanks to their special characteristics, bacteria have excellent ability to destroy tumor cells from the inside and induce innate and adaptive antitumor immune responses. Furthermore, bacterial components, including bacterial vesicles, spores, toxins, metabolites, and other active substances, similarly inherit their unique targeting properties and antitumor capabilities. Bacteria and their accessory products can even be reprogrammed to produce and deliver antitumor agents according to clinical needs. This review first discusses the role of different bacteria in the development of tumorigenesis and the latest advances in bacteria-based delivery platforms and the existing obstacles for application. Moreover, the prospect and challenges of clinical transformation of engineered bacteria are also summarized.

Establishment of ultrasound-responsive SonoBacteriaBot for targeted drug delivery and controlled release

Bacteria-driven biohybrid microbots have shown great potential in caⁿcer treatment. However, how precisely controlling drug release at the tumor site is still an issue. To overcome the limitation of this system, we proposed the ultrasound-responsive SonoBacteriaBot (DOX-PFP-PLGA@EcM). Doxorubicin (DOX) and perfluoro-n-pentane (PFP) were encapsulated in polylactic acid-glycolic acid (PLGA) to form ultrasound-responsive DOX-PFP-PLGA nanodroplets. Then, DOX-PFP-PLGA@EcM is created by DOX-PFP-PLGA amide-bonded to the surface of E. coli MG1655 (EcM). The DOX-PFP-PLGA@EcM was proved to have the characteristics of high tumor-targeting efficiency, controlled drug release capability, and ultrasound imaging. Based on the acoustic phase change function of nanodroplets, DOX-PFP-PLGA@EcM enhance the signal of US imaging after ultrasound irradiation. Meanwhile, the DOX loaded into DOX-PFP-PLGA@EcM can be released. After being intravenously injected, DOX-PFP-PLGA@EcM can efficiently accumulate in tumors without causing harm to critical organs. In conclusion, the SonoBacteriaBot has significant benefits in real-time monitoring and controlled drug release, which has significant potential applications for therapeutic drug delivery in clinical settings.

Bacteria-Driven Tumor Microenvironment-Sensitive Nanoparticles Targeting Hypoxic Regions Enhances the Chemotherapy Outcome of Lung Cancer

Background

Chemotherapy still plays a dominant role in cancer treatment. However, the inability of conventional chemotherapeutic drugs to reach the hypoxic zone of solid tumors significantly weakens their efficacy. Bacteria-mediated drug delivery systems can be an effective targeting strategy for improving the therapeutic outcomes in cancer. Anaerobic bacteria have the unique ability to selectively transport drug loads to the hypoxic regions of tumors.

Methods

We designed a Bifidobacterium infantis (Bif)-based biohybrid (Bif@PDA-PTX-NPs) to deliver polydopamine (PDA)-coated paclitaxel nanoparticles (PTX-NPs) to tumor tissues.

Results

The self-driven Bif@PDA-PTX-NPs maintained the toxicity of PTX as well as the hypoxic homing tendency of Bif. Furthermore, Bif@PDA-PTX-NPs significantly inhibited the growth of A549 xenografts in nude mice, and prolonged the survival of the tumor-bearing mice compared to the other PTX formulations without any systemic or localized toxicity.

Conclusion

The Bif@PDA-PTX-NPs biohybrids provide a new therapeutic strategy for targeted chemotherapy to solid tumors.

Stimuli-responsive nanoassemblies for targeted delivery against tumor and its microenvironment

Despite the emergence of various cancer treatments, such as surgery, chemotherapy, radiotherapy, and immunotherapy, their use remains restricted owing to their limited tumor elimination efficacy and side effects. The use of nanoassemblies as delivery systems in nanomedicine for tumor diagnosis and therapy is flourishing. These nanoassemblies can be designed to have various shapes, sizes, and surface charges to meet the requirements of different applications. It is crucial for nanoassemblies to have enhanced delivery of payloads while inducing minimal to no toxicity to healthy tissues. In this review, stimuli-responsive nanoassemblies capable of combating the tumor microenvironment (TME) are discussed. First, various TME characteristics, such as hypoxia, oxidoreduction, adenosine triphosphate (ATP) elevation, and acidic TME, are described. Subsequently, the unique characteristics of the vascular and stromal TME are differentiated, and multiple barriers that have to be overcome are discussed. Furthermore, strategies to overcome these barriers for successful drug delivery to the targeted site are reviewed and summarized. In conclusion, the possible challenges and prospects of using these nanoassemblies for tumor-targeted delivery are discussed. This review aims at inspiring researchers to develop stimuli-responsive nanoassemblies for tumor-targeted delivery for clinical applications.

Genetically engineered bacteria-mediated multi-functional nanoparticles for synergistic tumor-targeting therapy

Focused ultrasonic ablation surgery (FUAS) for tumor treatment has emerged as an effective non-invasive therapeutic approach, but its widespread clinical utilization is limited by its low therapeutic efficiency caused by inadequate tumor targeting, single imaging modality, and possible tumor recurrence following surgery. Therefore, this study aimed to develop a biological targeting synergistic system consisting of genetically engineered bacteria and multi-functional nanoparticles to overcome these limitations. Escherichia coli was genetically modified to carry an acoustic reporter gene encoding the formation of gas vesicles (GVs) and then target the tumor hypoxic environment in mice. After E. coli producing GVs (GVs-E. coli) colonized the tumor target area, ultrasound imaging and collaborative FUAS were performed; multi-functional nanoparticles were then enriched in the tumor target area through electrostatic adsorption. Multi-functional cationic lipid nanoparticles containing IR780, perfluorohexane, and banoxantrone dihydrochloride (AQ4N) were coloaded in the tumor to realize targeted multimodal imaging and enhance the curative effect of FUAS. AQ4N was stimulated by the tumor hypoxic environment and synergistically cooperated with FUAS to kill tumor cells. In sum, synergistic tumor therapy involving multi-functional nanoparticles mediated by genetically engineered bacteria overcomes the limitations and improves the curative effect of existing FUAS. STATEMENT OF SIGNIFICANCE: Inadequate tumor targeting, single image monitoring mode, and prone tumor recurrence following surgery remain significant challenges yet critical for tumor therapy. This study proposes a strategy for genetically engineered bacteria-mediated multifunctional nanoparticles for synergistic tumor therapy. The multifunctional genetically engineered biological targeting synergistic agent can accomplish tumor-targeting therapy, synergistic FUAS ablation, hypoxia-activated chemotherapy combined with FUAS ablation, and multiple-imaging guidance and monitoring all at the same time, thereby compensating for the shortcomings of FUAS treatment. This strategy could pave the way for the progress of tumor therapy.

US/MR Bimodal Imaging-Guided Bio-Targeting Synergistic Agent for Tumor Therapy

Purpose

Breast cancer is detrimental to the health of women due to the difficulty of early diagnosis and unsatisfactory therapeutic efficacy of available breast cancer therapies. High intensity focused ultrasound (HIFU) ablation is a new method for the treatment of breast tumors, but there is a problem of low ablation efficiency. Therefore, the improvement of HIFU efficiency to combat breast cancer is immediately needed. This study aimed to describe a novel anaerobic bacteria-mediated nanoplatform, comprising synergistic HIFU therapy for breast cancer under guidance of ultrasound (US) and magnetic resonance (MR) bimodal imaging.

Methods

The PFH@CL/Fe₃O₄ nanoparticles (NPs) (Perfluorohexane (PFH) and superparamagnetic iron oxides (SPIO, Fe₃O₄) with cationic lipid (CL) NPs) were synthesized using the thin membrane hydration method. The novel nanoplatform Bifidobacterium bifidum-mediated PFH@CL/Fe₃O₄ NPs were constructed by electrostatic adsorption. Thereafter, US and MR bimodal imaging ability of B. bifidum-mediated PFH@CL/Fe₃O₄ NPs was evaluated in vitro and in vivo. Finally, the efficacy of HIFU ablation based on B. bifidum-PFH@CL/Fe₃O₄ NPs was studied.

Results

B. bifidum combined with PFH@CL/Fe₃O₄ NPs by electrostatic adsorption and enhanced the tumor targeting ability of PFH@CL/Fe₃O₄ NPs. US and MR bimodal imaging clearly displayed the distribution of the bio-targeting nanoplatform in vivo. It was conducive for accurate and effective guidance of HIFU synergistic treatment of tumors. Furthermore, PFH@CL/Fe₃O₄ NPs could form microbubbles by acoustic droplet evaporation and promote efficiency of HIFU ablation under guidance of bimodal imaging.

Conclusion

A bio-targeting nanoplatform with high stability and good physicochemical properties was constructed. The HIFU synergistic agent achieved early precision imaging of tumors and promoted therapeutic effect, monitored by US and MR bimodal imaging during the treatment process.

Design and Evaluation of pH Sensitive PEG-Protamine Nanocomplex of Doxorubicin for Treatment of Breast Cancer

Cancer is the most common cause of mortality worldwide. There is dire need of modern strategies—such as surface modification of nanocarriers—to combat this global illness. Incorporation of active targeting ligands has arisen as a novel platform for specific tumor targeting. The aim of the current study was to formulate PEG-protamine complex (PPC) of doxorubicin (DOX) for treatment of breast cancer (BC). DOX coupling with PEG can enhance cell-penetrating ability: combating resistance in MDA-MB 231 breast cancer cells. Ionic gelation method was adopted to fabricate a pH sensitive nanocomplex. The optimized nanoformulation was characterized for its particle diameter, zeta potential, surface morphology, entrapment efficiency, crystallinity, and molecular interaction. In vitro assay was executed to gauge the release potential of nanoformulation. The mean particle size, zeta potential, and polydispersity index (PDI) of the optimized nanoparticles were observed to be 212 nm, 15.2 mV, and 0.264, respectively. Crystallinity studies and Fourier transform infrared (FTIR) analysis revealed no molecular interaction and confirmed the amorphous nature of drug within nanoparticles. The in vitro release data indicate sustained drug release at pH 4.8, which is intracellular pH of breast cancer cells, as compared to the drug solution. PPC loaded with doxorubicin can be utilized as an alternative and effective approach for specific targeting of breast cancer.