Implications of the Human Gut-Brain and Gut-Cancer Axes for Future Nanomedicine

Role of Gut Microbe Composition in Psychosocial Symptom Response to Exercise Training in Breast Cancer Survivors (ROME) study: protocol for a randomised controlled trial

INTRODUCTION

Breast cancer survivors have an increased risk for chronic fatigue and altered gut microbiota composition, both with negative health and quality of life affects. Exercise modestly improves fatigue and is linked to gut microbial diversity and production of beneficial metabolites. Studies suggest that gut microbiota composition is a potential mechanism underlying fatigue response to exercise. Randomised controlled trials testing the effects of exercise on the gut microbiome are limited and there is a scarcity of findings specific to breast cancer survivors. The objective of this study is to determine if fitness-related modifications to gut microbiota occur and, if so, mediate the effects of aerobic exercise on fatigue response.

METHODS AND ANALYSIS

The research is a randomised controlled trial among breast cancer survivors aged 18-74 with fatigue. The primary aim is to determine the effects of aerobic exercise training compared with an attention control on gut microbiota composition. The secondary study aims are to test if exercise training (1) affects the gut microbiota composition directly and/or indirectly through inflammation (serum cytokines), autonomic nervous system (heart rate variability) or hypothalamic-pituitary-adrenal axis mediators (hair cortisol assays), and (2) effects on fatigue are direct and/or indirect through changes in the gut microbiota composition. All participants receive a standardised controlled diet. Assessments occur at baseline, 5 weeks, 10 weeks and 15 weeks (5 weeks post intervention completion). Faecal samples collect the gut microbiome and 16S gene sequencing will identify the microbiome. Fatigue is measured by a 13-item multidimensional fatigue scale.

ETHICS AND DISSEMINATION

The University of Alabama at Birmingham Institutional Review Board (IRB) approved this study on 15 May 2019, UAB IRB#30000320. A Data and Safety Monitoring Board convenes annually or more often if indicated. Findings will be disseminated in peer-reviewed journals and conference presentations.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, NCT04088708.

Therapeutic applications of gut microbes in cardiometabolic diseases: current state and perspectives

Cardiometabolic disease (CMD) encompasses a range of diseases such as hypertension, atherosclerosis, heart failure, obesity, and type 2 diabetes. Recent findings about CMD's interaction with gut microbiota have broadened our understanding of how diet and nutrition drive microbes to influence CMD. However, the translation of basic research into the clinic has not been smooth, and dietary nutrition and probiotic supplementation have yet to show significant evidence of the therapeutic benefits of CMD. In addition, the published reviews do not suggest the core microbiota or metabolite classes that influence CMD, and systematically elucidate the causal relationship between host disease phenotypes-microbiome. The aim of this review is to highlight the complex interaction of the gut microbiota and their metabolites with CMD progression and to further centralize and conceptualize the mechanisms of action between microbial and host disease phenotypes. We also discuss the potential of targeting modulations of gut microbes and metabolites as new targets for prevention and treatment of CMD, including the use of emerging technologies such as fecal microbiota transplantation and nanomedicine. KEY POINTS: • To highlight the complex interaction of the gut microbiota and their metabolites with CMD progression and to further centralize and conceptualize the mechanisms of action between microbial and host disease phenotypes. • We also discuss the potential of targeting modulations of gut microbes and metabolites as new targets for prevention and treatment of CMD, including the use of emerging technologies such as FMT and nanomedicine. • Our study provides insight into identification-specific microbiomes and metabolites involved in CMD, and microbial-host changes and physiological factors as disease phenotypes develop, which will help to map the microbiome individually and capture pathogenic mechanisms as a whole.

Emerging nanotherapeutic strategies targeting gut-X axis against diseases

Gut microbiota can coordinate with different tissues and organs to maintain human health, which derives the concept of the gut-X axis. Conversely, the dysbiosis of gut microbiota leads to the occurrence and development of various diseases, such as neurological diseases, liver diseases, and even cancers. Therefore, the modulation of gut microbiota offers new opportunities in the field of medicines. Antibiotics, probiotics or other treatments might restore unbalanced gut microbiota, which effects do not match what people have expected. Recently, nanomedicines with the high targeting ability and reduced toxicity make them an appreciative choice for relieving disease through targeting gut-X axis. Considering this paradigm-setting trend, the current review summarizes the advancements in gut microbiota and its related nanomedicines. Specifically, this article introduces the immunological effects of gut microbiota, summarizes the gut-X axis-associated diseases, and highlights the nanotherapeutics-mediated treatment via remolding the gut-X axis. Moreover, this review also discusses the challenges in studies related to nanomedicines targeting the gut microbiota and offers the future perspective, thereby aiming at charting a course toward clinic.

Direct and gut microbiota-mediated toxicities of environmental antibiotics to fish and aquatic invertebrates

The accumulation of antibiotics in the environment has ecological impacts that have received less attention than the human health risks of antibiotics, although the effects could be far-reaching. This review discusses the effects of antibiotics on the health of fish and zooplankton, manifesting in direct or dysbiosis-mediated physiological impairment. Acute effects of antibiotics in these organism groups are usually induced at high concentrations (LC₅₀ at ∼100-1000 mg/L) that are not commonly present in aquatic environments. However, when exposed to sub-lethal, environmentally relevant levels of antibiotics (ng/L-μg/L) disruption of physiological homeostasis, development, and fecundity can occur. Antibiotics at similar or lower concentrations can induce dysbiosis of gut microbiota which can affect the health of fish and invertebrates. We show that the data about molecular-level effects of antibiotics at low exposure concentrations are limited, hindering environmental risk assessment and species sensitivity analysis. Fish and crustaceans (Daphnia sp.) were the two groups of aquatic organisms used most often for antibiotic toxicity testing, including microbiota analysis. While low levels of antibiotics impact the composition and function of gut microbiota in aquatic organisms, the correlation and causality of these changes to host physiology are not straightforward. In some cases, negative or lack of correlation have occurred, and, unexpectedly, gut microbial diversity has been unaffected or increased upon exposure to environmental levels of antibiotics. Efforts to incorporate functional analyses of gut microbiota are beginning to provide valuable mechanistic information, but more data is needed for ecological risk assessment of antibiotics.

Oral polyphenol-armored nanomedicine for targeted modulation of gut microbiota-brain interactions in colitis

Developing oral nanomedicines that suppress intestinal inflammation while modulating gut microbiota and brain interactions is essential for effectively treating inflammatory bowel disease. Here, we report an oral polyphenol-armored nanomedicine based on tumor necrosis factor-α (TNF-α)-small interfering RNA and gallic acid-mediated graphene quantum dot (GAGQD)-encapsulated bovine serum albumin nanoparticle, with a chitosan and tannin acid (CHI/TA) multilayer. Referred to "armor," the CHI/TA multilayer resists the harsh environment of the gastrointestinal tract and adheres to inflamed colon sites in a targeted manner. TA provides antioxidative stress and prebiotic activities that modulate the diverse gut microbiota. Moreover, GAGQD protected TNF-α-siRNA delivery. Unexpectedly, the armored nanomedicine suppressed hyperactive immune responses and modulated bacterial gut microbiota homeostasis in a mouse model of acute colitis. Notably, the armored nanomedicine alleviated anxiety- and depression-like behaviors and cognitive impairment in mice with colitis. This armor strategy sheds light on the effect of oral nanomedicines on bacterial gut microbiome-brain interactions.

Research advances in nanomedicine applied to the systemic treatment of colorectal cancer

The systematic treatment of colorectal cancer (CRC) still has room for improvement. The efficacy of chemotherapy, that of anti-vascular therapy, and that of immunotherapy have been unsatisfactory. In recent years, nanomaterials have been used as carriers to improve the bioavailability of anticancer drugs. For the treatment of colorectal cancer, nanodrugs increase the possibility of more precise targeted delivery. However, the actual benefits may cover more aspects. Nanocarriers can produce synergistic effects with anticancer drugs, including the scavenging of reactive oxygen species and co-delivery of a variety of drugs. Currently, immunotherapy has very limited clinical applications in CRC. Modified nanocarriers can activate the immune microenvironment, which can be used for staging antigen recognition or the immune response. Cancer vaccines based on nanomaterials and modified immune checkpoint inhibitors have shown therapeutic potential in animal models. Considering the direct or indirect relationship between the intestinal microflora and CRC, a variety of nanodrugs that regulate microbial function have been explored as an anticancer strategy, and the special structure of microorganisms can also be used as a basis for improving the delivery of traditional nanoparticles (NPs). This review summarizes recent research performed on nanocarriers in in vivo and in vitro models and the synergistic anticancer effects of nanocarriers, focusing on the interaction between NPs and the body, resulting in enhanced efficacy and immune activation. Furthermore, this review describes the current trend of NPs used in the treatment of CRC.

Tumor resident microbiota and response to therapies: An insight on tissue bacterial microbiota

The role of the intestinal microbiota in the promotion, progression, and response to therapies is gaining importance, but recent studies confirm the presence of microbiota also in the tumor, thus becoming a component of the tumor microenvironment. There is not much knowledge on the characteristics and mechanisms of action of the tumor resident microbiota, but there are already indications of its involvement in conditioning the response to therapies. In this review, we discuss recent publications on the interaction between microbiota and anticancer treatments, mechanisms of resistance and possible strategies for manipulating the microbiota that could improve treatments in a personalized medicine perspective.

Orally fed EGCG coronate food released TiO2 and enhanced penetrability into body organs via gut

Owing to unique nano-scale properties, TiO₂-NPs (T-NPs) are employed as food-quality enhancers in >900 processed food products. Whereas, epigallocatechin-3-gallate (EGCG), a green tea polyphenol is consumed in traditional brewed tea, globally. Taken together, we aimed to investigate whether human gastric-acid digested T-NPs and complex tea catechins yield ionic species (Ti⁴⁺_, Ti³⁺ etc.) and active EGCG forms to meet favourable conditions for in vivo bio-genesis of EGCG-coronated TiO₂-NPs (ET-NPs) in human gut. Secondly, compared to bare-surface micro and nano-scale TiO₂, i.e., T-MPs and T-NPs, respectively, how EGCG coronation on ET-NPs in the gut facilitates the modulation of intrinsic propensity of internalization of TiO₂ species into bacteria, body-organs, and gut-microbiota (GM), and immune system. ET-NPs were synthesized in non-toxic aqueous solution at varied pH (3-10) and characterised by state-of-the-arts for crystallinity, surface-charge, EGCG-encapsulation, stability, size, composition and morphology. Besides, flow-cytometry (FCM), TEM, EDS, histopathology, RT-PCR, 16S-rRNA metagenomics and ELISA were also performed to assess the size and surface dependent activities of ET-NPs, T-NPs and T-MPs vis-a-vis planktonic bacteria, biofilm, GM bacterial communities and animal's organs. Electron-microscopic, NMR, FTIR, DLS, XRD and EDS confirmed the EGCG coronation, dispersity, size-stability of ET-NPs, crystallinity and elemental composition of ET-NPs-8 and T-NPs. Besides, FCM, RT-PCR, 16S-rRNA metagenomics, histopathology, SEM and EDS analyses exhibited that EGCG coronation in ET-NPs-8 enhanced the penetration into body organs (i.e., liver and kidney etc.) and metabolically active bacterial communities of GM.

P2X7 receptor as the regulator of T-cell function in intestinal barrier disruption

The intestinal mucosa is a highly compartmentalized structure that forms a direct barrier between the host intestine and the environment, and its dysfunction could result in a serious disease. As T cells, which are important components of the mucosal immune system, interact with gut microbiota and maintain intestinal homeostasis, they may be involved in the process of intestinal barrier dysfunction. P2X7 receptor (P2X7R), a member of the P2X receptors family, mediates the effects of extracellular adenosine triphosphate and is expressed by most innate or adaptive immune cells, including T cells. Current evidence has demonstrated that P2X7R is involved in inflammation and mediates the survival and differentiation of T lymphocytes, indicating its potential role in the regulation of T cell function. In this review, we summarize the available research about the regulatory role and mechanism of P2X7R on the intestinal mucosa-derived T cells in the setting of intestinal barrier dysfunction.

In Situ Upregulating Heat Shock Protein 70 via Gastric Nano-Heaters for the Interference of Helicobacter pylori Infection

Taking inspiration from the mechanism of Helicobacter pylori infection can lead to innovative antibacterial ways to fight antibiotics resistance. Herein, a gastric nano-heater iron-cobalt alloy shielded with graphitic shells (FeCo@G) is developed to interfere with H. pylori infection under an alternating magnetic field. FeCo@G shows a high and stable specific loss power (SLP = 534.1 W g^-1) in the acidic environment and provides efficient magnetothermal stimulation in the stomach. Such stimulation upregulates the cytoprotective heat shock protein 70 (HSP70) in gastric epithelial cells, which antagonizes the infection of H. pylori. This finding is further supported by the transcriptomic analysis verifying the upregulation of HSP70 in the stomach. Moreover, the nano-heater shows a high inhibition rate of H. pylori in vivo with good biocompatibility; 95% of FeCo@G is excreted from the mouse's gastrointestinal tract within 12 h. In summary, FeCo@G allows magnetothermal therapy to be used in harsh gastric environments, providing an approach for the therapy against H. pylori.

Silver and Hyaluronic Acid-Coated Gold Nanoparticles Modulate the Metabolism of a Model Human Gut Bacterium Lactobacillus casei

Medical applications of nanotechnology are promising in creating efficient and targeted therapies. However, so far, nanodrug design has not taken into consideration possible effects on human microbiota. The beneficial functions of bacteria could be stimulated by nanodrugs while negative effects on beneficial bacteria could cause risks to human health. Here, simulated intestinal fluid (IF) was optimized for culturing a human commensal and probiotic bacterial strain, Lactobacillus casei, to study the effects of medically relevant NPs—Ag and hyaluronic acid-coated Au NPs (HA-Au NPs)—in conditions pertinent to the gastrointestinal tract. When cultivated either aerobically or anaerobically, the specific growth rates of L. casei were ~0.2 h−1 in IF and ~0.4 h−1 in the standard medium of lactobacilli (MRS). Ag NPs inhibited the growth of L. casei in IF at lower concentrations (EC50 ~ 65 and 15 mg/L in aerobic and anaerobic conditions, respectively) than in MRS (EC50 > 100 mg/L), likely caused by differences in the composition of the two media and different intrinsic growth rates of bacteria in IF and MRS. Ag NP dissolution in IF and MRS did not explain the differences in growth inhibition, implying NP-specific effects. HA-Au NPs were not growth-inhibitory to L. casei up to 250 mg/L. Still, both NPs at sub-growth-inhibitory concentrations suppressed the expression of bacteriocin genes in L. casei, suggesting an inhibitory effect of NPs on the probiotic properties of L. casei, i.e., its competitiveness in microbial communities. However, HA-Au NPs did not appear to affect or even stimulated the immunomodulatory properties of L. casei in human intestinal epithelial cells. Thus, medically relevant NPs at low, sub-bacteriostatic levels can affect the metabolism of beneficial human bacteria and potentially induce changes in the microbiota and immune signaling.

Advanced Light Source Analytical Techniques for Exploring the Biological Behavior and Fate of Nanomedicines

Exploration of the biological behavior and fate of nanoparticles, as affected by the nanomaterial-biology (nano-bio) interaction, has become progressively critical for guiding the rational design and optimization of nanomedicines to minimize adverse effects, support clinical translation, and aid in evaluation by regulatory agencies. Because of the complexity of the biological environment and the dynamic variations in the bioactivity of nanomedicines, in-situ, label-free analysis of the transport and transformation of nanomedicines has remained a challenge. Recent improvements in optics, detectors, and light sources have allowed the expansion of advanced light source (ALS) analytical technologies to dig into the underexplored behavior and fate of nanomedicines in vivo. It is increasingly important to further develop ALS-based analytical technologies with higher spatial and temporal resolution, multimodal data fusion, and intelligent prediction abilities to fully unlock the potential of nanomedicines. In this Outlook, we focus on several selected ALS analytical technologies, including imaging and spectroscopy, and provide an overview of the emerging opportunities for their applications in the exploration of the biological behavior and fate of nanomedicines. We also discuss the challenges and limitations faced by current approaches and tools and the expectations for the future development of advanced light sources and technologies. Improved ALS imaging and spectroscopy techniques will accelerate a profound understanding of the biological behavior of new nanomedicines. Such advancements are expected to inspire new insights into nanomedicine research and promote the development of ALS capabilities and methods more suitable for nanomedicine evaluation with the goal of clinical translation.

Nanoparticles for oral delivery: targeted therapy for inflammatory bowel disease

As a group of chronic and idiopathic gastrointestinal (GI) disorders, inflammatory bowel disease (IBD) is characterized by recurrent intestinal mucosal inflammation. Oral administration is critical for the treatment of IBD. Unfortunately, it is difficult to target the bowel located in the GI tract due to multiple physical barriers. The unique physicochemical properties of nanoparticle-based drug delivery systems (DDSs) and their enhanced permeability and retention effects in the inflamed bowel, render nanomedicines to be used to implement precise drug delivery at diseased sites in IBD therapy. In this review, we described the pathophysiological features of IBD, and designed strategies to exploit these features for intestinal targeting. In addition, we introduced the types of currently developed nano-targeted carriers, including synthetic nanoparticle-based and emerging naturally derived nanoparticles (e.g., extracellular vesicles and plant-derived nanoparticles). Moreover, recent developments in targeted oral nanoparticles for IBD therapy were also highlighted. Finally, we presented challenges associated with nanotechnology and potential directions for future IBD treatment.

Anti-Parkinsonian Therapy: Strategies for Crossing the Blood-Brain Barrier and Nano-Biological Effects of Nanomaterials

Parkinson's disease (PD), a neurodegenerative disease that shows a high incidence in older individuals, is becoming increasingly prevalent. Unfortunately, there is no clinical cure for PD, and novel anti-PD drugs are therefore urgently required. However, the selective permeability of the blood-brain barrier (BBB) poses a huge challenge in the development of such drugs. Fortunately, through strategies based on the physiological characteristics of the BBB and other modifications, including enhancement of BBB permeability, nanotechnology can offer a solution to this problem and facilitate drug delivery across the BBB. Although nanomaterials are often used as carriers for PD treatment, their biological activity is ignored. Several studies in recent years have shown that nanomaterials can improve PD symptoms via their own nano-bio effects. In this review, we first summarize the physiological features of the BBB and then discuss the design of appropriate brain-targeted delivery nanoplatforms for PD treatment. Subsequently, we highlight the emerging strategies for crossing the BBB and the development of novel nanomaterials with anti-PD nano-biological effects. Finally, we discuss the current challenges in nanomaterial-based PD treatment and the future trends in this field. Our review emphasizes the clinical value of nanotechnology in PD treatment based on recent patents and could guide researchers working in this area in the future.

Multifunctional Therapeutic Approach of Nanomedicines against Inflammation in Cancer and Aging

Cancer is a fatal disorder that affects people across the globe, yet existing therapeutics are ineffective. The development of submicrometer transport for optimizing the biodistribution of systemically provided medications is the focus of nanomedicine. Nanoparticle- (NP-) based treatments may enable the development of novel therapeutic approaches to combat this deadly disorder. In multifunctional, multimodal imaging, and drug delivery carriers, NPs generally play a major role. They have emerged as potential strategies for the invention of innovative therapeutic procedures in the last decade. The exponential growth of nanotechnologies in recent years has increased public awareness of the application of these innovative therapeutic approaches. Many tumor-targeted nanomedicines have been studied in cancer therapy, and there is clear evidence for a significant improvement in the therapeutic index of antineoplastic drugs. Age-related factors such as metabolic and physiological alterations in old age and inadequate animal models are currently understudied in nanomedicine and pharmacology. This review highlighted the most important targeting approaches, as well as public awareness, therapeutic advancements, and future prospects in age-related metabolic variations, and tumor-targeted nanomedicine studies.

Current understandings and clinical translation of nanomedicines for breast cancer therapy

Breast cancer is one of the most frequently diagnosed cancers that is threatening women's life. Current clinical treatment regimens for breast cancer often involve neoadjuvant and adjuvant systemic therapies, which somewhat are associated with unfavorable features. Also, the heterogeneous nature of breast cancers requires precision medicine that cannot be fulfilled by a single type of systemically administered drug. Taking advantage of the nanocarriers, nanomedicines emerge as promising therapeutic agents for breast cancer that could resolve the defects of drugs and achieve precise drug delivery to almost all sites of primary and metastatic breast tumors (e.g. tumor vasculature, tumor stroma components, breast cancer cells, and some immune cells). Seven nanomedicines as represented by Doxil® have been approved for breast cancer clinical treatment so far. More nanomedicines including both non-targeting and active targeting nanomedicines are being evaluated in the clinical trials. However, we have to realize that the translation of nanomedicines, particularly the active targeting nanomedicines is not as successful as people have expected. This review provides a comprehensive landscape of the nanomedicines for breast cancer treatment, from laboratory investigations to clinical applications. We also highlight the key advances in the understanding of the biological fate and the targeting strategies of breast cancer nanomedicine and the implications to clinical translation.

Oral nanomedicine for modulating immunity, intestinal barrier functions, and gut microbiome

The gastrointestinal tract (GIT) affects not only local diseases in the GIT but also various systemic diseases. Factors that can affect the health and disease of both GIT and the human body include 1) the mucosal immune system composed of the gut-associated lymphoid tissues and the lamina propria, 2) the intestinal barrier composed of mucus and intestinal epithelium, and 3) the gut microbiota. Selective delivery of drugs, including antigens, immune-modulators, intestinal barrier enhancers, and gut-microbiome manipulators, has shown promising results for oral vaccines, immune tolerance, treatment of inflammatory bowel diseases, and other systemic diseases, including cancer. However, physicochemical and biological barriers of the GIT present significant challenges for successful translation. With the advances of novel nanomaterials, oral nanomedicine has emerged as an attractive option to not only overcome these barriers but also to selectively deliver drugs to the target sites in GIT. In this review, we discuss the GIT factors and physicochemical and biological barriers in the GIT. Furthermore, we present the recent progress of oral nanomedicine for oral vaccines, immune tolerance, and anti-inflammation therapies. We also discuss recent advances in oral nanomedicine designed to fortify the intestinal barrier functions and modulate the gut microbiota and microbial metabolites. Finally, we opine about the future directions of oral nano-immunotherapy.

Customized materials-assisted microorganisms in tumor therapeutics

Microorganisms have been extensively applied as active biotherapeutic agents or drug delivery vehicles for antitumor treatment because of their unparalleled bio-functionalities. Taking advantage of the living attributes of microorganisms, a new avenue has been opened in anticancer research. The integration of customized functional materials with living microorganisms has demonstrated unprecedented potential in solving existing questions and even conferring microorganisms with updated antitumor abilities and has also provided an innovative train of thought for enhancing the efficacy of microorganism-based tumor therapy. In this review, we have summarized the emerging development of customized materials-assisted microorganisms (MAMO) (including bacteria, viruses, fungi, microalgae, as well as their components) in tumor therapeutics with an emphasis on the rational utilization of chosen microorganisms and tailored materials, the ingenious design of biohybrid systems, and the efficacious antitumor mechanisms. The future perspectives and challenges in this field are also discussed.

Carbon Nanotubes Promote the Development of Intestinal Organoids through Regulating Extracellular Matrix Viscoelasticity and Intracellular Energy Metabolism

The biological effect of engineered carbon nanotubes (CNTs) as beneficial biomaterials on the intestine, especially on its development, remains unclear. Here, we investigated the profitable effect of CNTs with a different graphene layer and surface modification on the 3D model of intestinal organoids and demonstrated that CNTs (50 μg/mL) promoted the development of intestinal organoids over time (0-5 days). The mechanisms involve the modulation of extracellular matrix (ECM) viscoelasticity and intracellular energy metabolism. In particular, CNTs reduced the hardness of the extracellular matrix through decreasing the elasticity and increasing the viscosity as a result of elevated metalloproteinase and binding to a protein scaffold, which activated the mechanical membrane sensors of cells, Piezo, and downstream P-p38-yes-associated protein (YAP) pathway. Moreover, CNTs altered the metabolic profile of intestinal organoids and induced increased mitochondria activity, respiration, and nutrient absorption. These mechanisms cooperated with each other to promote the proliferation and differentiation of intestinal organoids. In addition, the promoted effect of CNTs is highly dependent on the number of graphene layers, manifested as multiwalled CNTs > single-walled CNTs. Our findings highlight the CNT-intestine interaction and imply the potential of CNTs as biomaterials for intestine-associated tissue engineering.

The intratumoural microbiota in cancer: new insights from inside

The human body harbors a vast array of microbiota that modulates host pathophysiological processes and modifies the risk of diseases including cancer. With the advent of metagenomic sequencing studies, the intratumoural microbiota has been found as a component of the tumor microenvironment, imperceptibly affecting the tumor progression and response to current antitumor treatments. The underlying carcinogenic mechanisms of intratumoural microbiota, mainly including inducing DNA damages, activating oncogenic signaling pathways and suppressing the immune response, differ significantly in varied organs and are not fully understood. Some native or genetically engineered microbial species can specifically accumulate and replicate within tumors to initiate antitumor immunity, which will be conducive to pursue precise cancer therapies. In this review, we summarized the community characteristics and therapeutic potential of intratumoural microbiota across diverse tumor types. It may provide new insights for a better understanding of tumor biology and hint at the significance of manipulating intratumoural microbiota.

Tailoring metal-organic frameworks-based nanozymes for bacterial theranostics

Nanozymes are next-generation artificial enzymes having distinguished features such as cost-effective, enhanced surface area, and high stability. However, limited selectivity and moderate activity of nanozymes in the biochemical environment hindered their usage and encouraged researchers to seek alternative catalytic materials. Recently, metal-organic frameworks (MOFs) characterized by distinct crystalline porous structures with large surface area, tunable pores, and uniformly dispersed active sites emerged, that filled the gap between natural enzymes and nanozymes. Moreover, by selecting suitable metal ions and organic linkers, MOFs can be designed for effective bacterial theranostics. In this review, we briefly presented the design and fabrication of MOFs. Then, we demonstrated the applications of MOFs in bacterial theranostics and their safety considerations. Finally, we proposed the major obstacles and opportunities for further development in research on the interface of nanozymes and MOFs. We expect that MOFs based nanozymes with unique physicochemical and intrinsic enzyme-mimicking properties will gain broad interest in both fundamental research and biomedical applications.