Engineered Bacterial Bioreactor for Tumor Therapy via Fenton-Like Reaction with Localized H2 O2 Generation

Immunoadjuvant-Modified Rhodobacter sphaeroides Potentiate Cancer Photothermal Immunotherapy

Photothermal immunotherapy has become a promising strategy for tumor treatment. However, the intrinsic drawbacks like light instability, poor immunoadjuvant effect, and poor accumulation of conventional inorganic or organic photothermal agents limit their further applications. Based on the superior carrying capacity and active tumor targeting property of living bacteria, an immunoadjuvant-intensified and engineered tumor-targeting bacterium was constructed to achieve effective photothermal immunotherapy. Specifically, immunoadjuvant imiquimod (R837)-loaded thermosensitive liposomes (R837@TSL) were covalently decorated onto Rhodobacter sphaeroides (R.S) to obtain nanoimmunoadjuvant-armed bacteria (R.S-R837@TSL). The intrinsic photothermal property of R.S combined R837@TSL to achieve in situ near-infrared (NIR) laser-controlled release of R837. Meanwhile, tumor immunogenic cell death (ICD) caused by photothermal effect of R.S-R837@TSL, synergizes with released immunoadjuvants to promote maturation of dendritic cells (DCs), which enhance cytotoxic T lymphocytes (CTLs) infiltration for further tumor eradication. The photosynthetic bacteria armed with immunoadjuvant-loaded liposomes provide a strategy for immunoadjuvant-enhanced cancer photothermal immunotherapy.

Multifunctional Protein Hybrid Nanoplatform for Synergetic Photodynamic-Chemotherapy of Malignant Carcinoma by Homologous Targeting Combined with Oxygen Transport

Photodynamic therapy (PDT) under hypoxic conditions and drug resistance in chemotherapy are perplexing problems in anti-tumor treatment. In addition, central nervous system neoplasm-targeted nanoplatforms are urgently required. To address these issues, a new multi-functional protein hybrid nanoplatform is designed, consisting of transferrin (TFR) as the multicategory solid tumor recognizer and hemoglobin for oxygen supply (ODP-TH). This protein hybrid framework encapsulates the photosensitizer protoporphyrin IX (PpIX) and chemotherapeutic agent doxorubicin (Dox), which are attached by a glutathione-responsive disulfide bond. Mechanistically, ODP-TH crosses the blood-brain barrier (BBB) and specifically aggregated in hypoxic tumors via protein homology recognition. Oxygen and encapsulated drugs ultimately promote a therapeutic effect by down-regulating the abundance of multidrug resistance gene 1 (MDR1) and hypoxia-inducible factor-1-α (HIF-1α). The results reveal that ODP-TH achieves oxygen transport and protein homology recognition in the hypoxic tumor occupation. Indeed, compared with traditional photodynamic chemotherapy, ODP-TH achieves a more efficient tumor-inhibiting effect. This study not only overcomes the hypoxia-related inhibition in combination therapy by targeted oxygen transport but also achieves an effective treatment of multiple tumors, such as breast cancer and glioma, providing a new concept for the construction of a promising multi-functional targeted and intensive anti-tumor nanoplatform.

Both-In-One Hybrid Bacteria Suppress the Tumor Metastasis and Relapse via Tandem-Amplifying Reactive Oxygen Species-Immunity Responses

Bacterial therapy, which targets the tumor site and aims at exerting an antitumor immune response, has displayed a great potential against malignant tumors. However, failure of the phase I clinical trial of Salmonella strain VNP20009 alone demonstrates that bacterial treatment alone can unsatisfy the requirements of high efficiency and biosafety. Herein, a strategy of both-in-one hybrid bacteria is proposed, wherein the chemotherapeutic drug doxorubicin (DOX) is integrated onto the surface of glucose dehydrogenase (GDH)-overexpressed non-pathogenic Escherichia coli (E. coli) strain, to potentiate the antitumor efficacy. Nicotinamide adenine dinucleotide phosphate (NADPH), which is produced by GDH from E. coli, promotes the generation of toxic reactive oxygen species (ROS) within the tumor, and ROS is then catalyzed by the DOX-activated NADPH oxidases. Importantly, the hybrid bacteria enhance stimulated systemic antitumor immune responses, thereby leading to effective tumor eradication. When this strategy is applied in four different tumor models, the hybrid bacteria significantly inhibited tumor metastasis, postsurgical regrowth, and primary/distal tumor relapse. The both-in-one ROS-immunity-boosted hybrid bacteria strategy provides knowledge for the rational design of bacteria-based synergistic cancer therapy.

Mutual Benefit between Cu(II) and Polydopamine for Improving Photothermal-Chemodynamic Therapy

Combination therapy has attracted extensive interest in alleviating the shortcomings of monotherapy and enhancing the treatment efficacy. In this work, hollow mesoporous silica nanoparticles (HMSNs) play the role of nanocarriers in the delivery of Cu(II)-doped polydopamine (PDA), termed as HMSNs@PDA-Cu, for synergistic therapy. PDA acts as a traditional photothermal agent to realize photothermal treatment (PTT). Chemodynamic therapy (CDT) is realized by the reaction of Cu(II) with intracellular glutathione (GSH), and subsequently, the generated Cu(I) reacts with H₂O₂ to produce toxic hydroxyl radical (^•OH) through a Fenton-like reaction. The photothermal performance of PDA is improved after its coordination with Cu(II). On the other hand, PDA exhibits superoxide dismutase (SOD)-mimicking activity. PDA converts O₂^•- to H₂O₂ and improves the production of H₂O₂, which promotes the therapeutic effect of CDT. Moreover, the high temperature caused by PTT further enhances the yield of ^•OH for CDT. This nanotheranostic platform perfectly applied to the tumor depletion of mice, presenting great potential for cancer metastasis therapy in vitro and in vivo.

Cell membrane covered polydopamine nanoparticles with two-photon absorption for precise photothermal therapy of cancer

HYPOTHESIS

In view of the photothermal effect of polydopamine (PDA) nanoparticles and their internal D-π-D structures during assembly, the two-photon excited properties of PDA were studied toward the biomedical application. Further, the PDA molecules were coordinated with Mn²⁺ and the assembled nanoparticles were covered by cancer cell membranes, the complex system could be used directly for the treatment of cancer with photothermal and chemodynamic therapy.

EXPERIMENTS

The two-photon excited PDA-Mn²⁺ nanoparticles were used for the photothermal therapy combined with chemodynamic therapy. The complexes were coated with cancer cell membranes in order to enhance the tumor homologous efficiency. Multi-modal bioimaging and anti-tumor detections were carried out both in vitro and in vivo.

FINDINGS

PDA nanoparticles were demonstrated to have both good two-photon excited fluorescence and photothermal efficiency. The assembled nanoparticles modified with Mn²⁺ and cancer cell membranes have an obvious targeting and synergetic anti-cancer efficiency. The system creates a simple way for a precise operation with multi-modal imaging function.

Chemodynamic nanomaterials for cancer theranostics

It is of utmost urgency to achieve effective and safe anticancer treatment with the increasing mortality rate of cancer. Novel anticancer drugs and strategies need to be designed for enhanced therapeutic efficacy. Fenton- and Fenton-like reaction-based chemodynamic therapy (CDT) are new strategies to enhance anticancer efficacy due to their capacity to generate reactive oxygen species (ROS) and oxygen (O2). On the one hand, the generated ROS can damage the cancer cells directly. On the other hand, the generated O2 can relieve the hypoxic condition in the tumor microenvironment (TME) which hinders efficient photodynamic therapy, radiotherapy, etc. Therefore, CDT can be used together with many other therapeutic strategies for synergistically enhanced combination therapy. The antitumor applications of Fenton- and Fenton-like reaction-based nanomaterials will be discussed in this review, including: (iþ) producing abundant ROS in-situ to kill cancer cells directly, (ii) enhancing therapeutic efficiency indirectly by Fenton reaction-mediated combination therapy, (iii) diagnosis and monitoring of cancer therapy. These strategies exhibit the potential of CDT-based nanomaterials for efficient cancer therapy.

Bacteria-Mediated Synergistic Cancer Therapy: Small Microbiome Has a Big Hope

The use of bacteria to specifically migrate to cancerous tissue and elicit an antitumor immune response provides a promising platform against cancer with significantly high potency. With dozens of clinical trials underway, some researchers hold the following views: "humans are nearing the first commercial live bacteria therapeutic." However, the facultative anaerobe Salmonella typhimurium VNP20009, which is particularly safe and shows anticancer effects in preclinical studies, had failed in a phase I clinical trial due to low tumor regression and undesired dose-dependent side effects. This is almost certain to disappoint people's inflated expectations, but it is noted that recent state-of-the-art research has turned attention to bacteria-mediated synergistic cancer therapy (BMSCT). In this review, the foundation of bacteria-mediated bio-therapy is outlined. Then, we summarize the potential benefits and challenges of bacterial bio-therapy in combination with different traditional anticancer therapeutic modalities (chemotherapy, photothermal therapy, reactive oxygen and nitrogen species therapy, immunotherapy, or prodrug-activating therapy) in the past 5 years. Next, we discuss multiple administration routes of BMSCT, highlighting potentiated antitumor responses and avoidance of potential side effects. Finally, we envision the opportunities and challenges for BMSCT development, with the purpose of inspiring medicinal scientists to widely utilize the microbiome approach in patient populations.

All-in-One Theranostic Nanomedicine with Ultrabright Second Near-Infrared Emission for Tumor-Modulated Bioimaging and Chemodynamic/Photodynamic Therapy

Reactive oxygen species (ROS)-based therapeutic modalities including chemodynamic therapy (CDT) and photodynamic therapy (PDT) hold great promise for conquering malignant tumors. However, these two methods tend to be restricted by the overexpressed glutathione (GSH) and hypoxia in the tumor microenvironment (TME). Here, we develop biodegradable copper/manganese silicate nanosphere (CMSN)-coated lanthanide-doped nanoparticles (LDNPs) for trimodal imaging-guided CDT/PDT synergistic therapy. The tridoped Yb³⁺/Er³⁺/Tm³⁺ in the ultrasmall core and the optimal Yb³⁺/Ce³⁺ doping in the shell enable the ultrabright dual-mode upconversion (UC) and downconversion (DC) emissions of LDNPs under near-infrared (NIR) laser excitation. The luminescence in the second near-infrared (NIR-II, 1000-1700 nm) window offers deep-tissue penetration, high spatial resolution, and reduced autofluorescence when used for optical imaging. Significantly, the CMSNs are capable of relieving the hypoxic TME through decomposing H₂O₂ to produce O₂, which can react with the sample to generate ¹O₂ upon excitation of UC photons (PDT). The GSH-triggered degradation of CMSNs results in the release of Fenton-like Mn²⁺ and Cu⁺ ions for ^•OH generation (CDT); simultaneously, the released Mn²⁺ ions couple with NIR-II luminescence imaging, computed tomography (CT) imaging, and magnetic resonance (MR) imaging of LDNPs, performing a TME-amplified trimodal effect. In such a nanomedicine, the TME modulation, bimetallic silicate photosensitizer, Fenton-like nanocatalyst, and NIR-II/MR/CT contrast agent were achieved "one for all", thereby realizing highly efficient tumor theranostics.

Metal-Based Nanocatalyst for Combined Cancer Therapeutics

As a classical nanocatalyst-based therapeutic modality, chemodynamic therapy (CDT) has received more and more attention. To improve the therapeutic efficacy of CDT, various metal-based nanocatalysts have been designed and constructed to catalyze the Fenton or Fenton-like reaction in the past few years. However, the therapeutic efficacy of certain CDT is still restricted by the tumor microenvironment, such as limited concentration of intracellular H₂O₂, inappropriate pH condition, as well as overexpressed glutathione (GSH). Therefore, many other therapeutic modalities, such as photodynamic therapy (PDT), photothermal therapy (PTT), starvation therapy, chemotherapy, and gas therapy, have been utilized to combine with CDT for increasing the tumor treatment performance. In this review, we summarized the development of combinatory therapeutic modalities based on CDT in recent years.

Engineering H2O2 Self-Supplying Nanotheranostic Platform for Targeted and Imaging-Guided Chemodynamic Therapy

Developing highly efficient chemodynamic therapy (CDT)-based theranostic technology for cancer treatment is highly desired but still challenging. A novel nanotheranostic platform is constructed for enhanced CDT by engineering hybrid CaO₂ and Fe₃O₄ nanoparticles with a hyaluronate acid (HA) stabilizer and NIR fluorophore label. This design not only enables the nanotheranostic agent to afford highly efficient CDT against tumor cells but also confers NIR fluorescence (NIRF) and magnetic resonance (MR) bimodal imaging for in vivo visualization of CDT. Moreover, the use of the HA stabilizer allows for the facile synthesis of the nanotheranostic agent with excellent biocompatibility and active targetability. The nanotheranaostic agent possesses a high capacity of self-supplying H₂O₂ and producing ^•OH in acidic conditions, while retaining the desired stability under physiological conditions. It also demonstrates high selectivity to tumor cells via CDT with minimized toxicity to normal cells. In vivo studies reveal that our nanotheranaostic agent exhibits efficacious tumor growth inhibition via a CDT mechanism with favorable biosafety. Moreover, in vivo visualization of the CDT progress via NIRF and MR bimodal imaging demonstrates specific targeting and treatment of tumors. The developed H₂O₂ self-supplying, active targeting, and bimodal imaging nanotheranostic platform holds the potential as a highly efficient strategy for CDT of cancer.