Enzymatically synthesised MnO2 nanoparticles for efficient near-infrared photothermal therapy and dual-responsive magnetic resonance imaging

Multi-responsive cascade enzyme-like catalytic nanoassembly for ferroptosis amplification and nanozyme-assisted mild photothermal therapy

Ferroptosis is greatly restricted by low reactive oxygen species (ROS) generation efficiency, and the inherent self-protection mechanism originating in heat shock proteins (HSPs) seriously impedes the efficiency of photothermal therapy (PTT). Herein, we designed an intelligent strategy utilizing cascade catalytic nanoassemblies (Au@COF@MnO2) with triple-enzyme activity for amplifying ferroptosis therapy and improving the efficiency of PTT in tumor. Gold nanozyme was encapsulated within a hollow manganese dioxide (MnO2) shell with the help of covalent organic frameworks (COFs). The nanoassemblies possess the ability of photothermal conversion. Mechanism studies suggested that glutathione (GSH) depletion by Au@COF@MnO2 leads to the inactivation of glutathione peroxidase 4 (GPX4). This effect synergized with Mn2+-mediated reactive oxygen species (ROS) generation to enhance the accumulation of lipid peroxide (LPO), thereby inducing high-efficiency ferroptosis. Notably, gold nanozyme facilitated the conversion of glucose into gluconic acid and hydrogen peroxide (H2O2). This process augmented the endogenous H2O2 levels necessary for Fenton chemistry, which could effectively promote the generation of ROS. Simultaneously, glucose depletion downregulated the expression of HSPs induced by hyperthermia, consequently reducing cellular heat resistance for enhancing PTT. Therefore, the cascade catalytic nanoassembly not only exhibits high tumor inhibition and admirable biosafety, but also possesses trimodal imaging performance for imaging-guided tumor therapy in vivo, holding great potential for clinical application. STATEMENT OF SIGNIFICANCE: This study engineered multi-responsive cascade catalytic nanoassembly (Au@COF@MnO2) with triple enzymatic functions for amplifying ferroptosis therapy and improving the efficiency of PTT in tumor. The nanoassembly exhibited multi-responsive release and great photothermal conversion performance. Glucose consumption-evoked starvation downregulated the hyperthermia-induced expression of HSPs in tumor cells, thereby improving the efficacy of PTT. Mechanism studies suggested that GSH depletion by Au@COF@MnO2 lead to the inactivation of GPX4, which synergized with Mn2+-mediated ROS generation to bolster the accumulation of LPO, thereby inducing high-efficiency ferroptosis. Moreover, the nanoassembly demonstrated trimodal (PT, PA, and MR) imaging in vivo, enabling the visualization of the tumor treatment with nanoassembly. Such nanoassembly exhibited high tumor inhibition and admirable biosafety in tumor therapy in vivo, holding a great potential for clinical application.

Coenzyme-A-Responsive Nanogel-Coated Electrochemical Sensor for Osteoarthritis-Detection-Based Genetic Models

An electrochemical sensor sensitive to coenzyme A (CoA) was designed using a CoA-responsive polyallylamine-manganese oxide-polymer dot nanogel coated on the electrode surface to detect various genetic models of osteoarthritis (OA). The CoA-responsive nanogel sensor responded to the abundance of CoA in OA, causing the breakage of MnO2 in the nanogel, thereby changing the electroconductivity and fluorescence of the sensor. The CoA-responsive nanogel sensor was capable of detecting CoA depending on the treatment time and distinguishing the response towards different OA genetic models that contained different levels of CoA (wild type/WT, NudT7 knockout/N7KO, and Acot12 knockout/A12KO). The WT, N7KO, and A12KO had distinct resistances, which further increased as the incubation time were changed from 12 h (R12h = 2.11, 2.40, and 2.68 MΩ, respectively) to 24 h (R24h = 2.27, 2.59, and 2.92 MΩ, respectively) compared to the sensor without treatment (Rcontrol = 1.63 MΩ). To simplify its application, the nanogel sensor was combined with a wireless monitoring device to allow the sensing data to be directly transmitted to a smartphone. Furthermore, OA-indicated anabolic (Acan) and catabolic (Adamts5) factor transcription levels in chondrocytes provided evidence regarding CoA and nanogel interactions. Thus, this sensor offers potential usage in simple and sensitive OA diagnostics.

Agonists and Inhibitors of the cGAS-STING Pathway

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is pivotal in immunotherapy. Several agonists and inhibitors of the cGAS-STING pathway have been developed and evaluated for the treatment of various diseases. The agonists aim to activate STING, with cyclic dinucleotides (CDNs) being the most common, while the inhibitors aim to block the enzymatic activity or DNA binding ability of cGAS. Meanwhile, non-CDN compounds and cGAS agonists are also gaining attention. The omnipresence of the cGAS-STING pathway in vivo indicates that its overactivation could lead to undesired inflammatory responses and autoimmune diseases, which underscores the necessity of developing both agonists and inhibitors of the cGAS-STING pathway. This review describes the molecular traits and roles of the cGAS-STING pathway and summarizes the development of cGAS-STING agonists and inhibitors. The information is supposed to be conducive to the design of novel drugs for targeting the cGAS-STING pathway.

Nanomaterial-mediated modulation of the cGAS-STING signaling pathway for enhanced cancer immunotherapy

Despite the current promise of immunotherapy, many cancer patients still suffer from challenges such as poor immune response rates, resulting in unsatisfactory clinical efficacy of existing therapies. There is an urgent need to combine emerging biomedical discoveries and innovations in traditional therapies. Modulation of the cGAS-STING signalling pathway represents an important innate immunotherapy pathway that serves as a crucial DNA sensing mechanism in innate immunity and viral defense. It has attracted increasing attention as an emerging target for cancer therapy. The recent advancements in nanotechnology have led to the significant utilization of nanomaterials in cancer immunotherapy, owing to their exceptional physicochemical properties such as large specific surface area and efficient permeability. Given the rapid development of cancer immunotherapy driven by the cGAS-STING activation, this study reviews the latest research progress in employing nanomaterials to modulate this signaling pathway. Based on the introduction of the main activation mechanisms of cGAS-STING pathway, this review focuses on nanomaterials that mediate the agonists involved and effectively activate this signaling pathway. In addition, combination nanotherapeutics based on the activation of the cGAS-STING signaling pathway are also discussed, including emerging strategies combining nanoformulated agonists with chemotherapy, radiotherapy as well as other immunomodulation in tumor targeting therapy. STATEMENT OF SIGNIFICANCE: Given the rapid development of cancer immunotherapy driven by the cGAS / STING activation, this study reviews the latest research advances in the use of nanomaterials to modulate this signaling pathway. Based on the introduction of key cGAS-STING components and their activation mechanisms, this review focuses on nanomaterials that can mediate the corresponding agonists and effectively activate this signaling pathway. In addition, combination nanotherapies based on the activation of the cGAS-STING signaling pathway are also discussed, including emerging strategies combining nanoformulated agonists with chemotherapy, radiotherapy as well as immunomodulation in cancer therapy,.

Laboratory Evolution of Metalloid Reductase Substrate Recognition and Nanoparticle Product Size

Glutathione reductase-like metalloid reductase (GRLMR) is an enzyme that reduces selenodiglutathione (GS-Se-SG), forming zerovalent Se nanoparticles (SeNPs). Error-prone polymerase chain reaction was used to create a library of ∼10,000 GRLMR variants. The library was expressed in BL21Escherichia coli in liquid culture with 50 mM of SeO32- present, under the hypothesis that the enzyme variants with improved GS-Se-SG reduction kinetics would emerge. The selection resulted in a GRLMR variant with two mutations. One of the mutations (D-E) lacks an obvious functional role, whereas the other mutation is L-H within 5 Å of the enzyme active site. This mutation places a second H residue within 5 Å of an active site dicysteine. This GRLMR variant was characterized for NADPH-dependent reduction of GS-Se-SG, GSSG, SeO32-, SeO42-, GS-Te-SG, and TeO32-. The evolved enzyme demonstrated enhanced reduction of SeO32- and gained the ability to reduce SeO42-. This variant is named selenium reductase (SeR) because of its emergent broad activity for a wide variety of Se substrates, whereas the parent enzyme was specific for GS-Se-SG. This study overall suggests that new biosynthetic routes are possible for inorganic nanomaterials using laboratory-directed evolution methods.

Phytic acid-modified manganese dioxide nanoparticles oligomer for magnetic resonance imaging and targeting therapy of osteosarcoma

Osteosarcoma is the most common malignant tumor in the skeletal system with high mortality. Phytic acid (PA) is a natural compound extracted from plant seeds, which shows certain antitumor activity and good bone targeting ability. To develop a novel theranostics for magnetic resonance imaging (MRI) and targeting therapy of osteosarcoma, we employed PA to modify manganese dioxide nanoparticles (MnO₂@PA NPs) for osteosarcoma treatment. The MnO₂ NPs oligomer was formed by PA modification with uniformed size distribution and negative zeta potential. Fourier-transform infrared spectroscopy, X-ray diffraction, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis demonstrated that PA has been successfully modified on MnO₂ NPs, and the structure of MnO₂@PA NPs is amorphous. In vitro experiments demonstrated that MnO₂@PA NPs oligomer can be efficiently internalized by tumor cell, and the internalized NPs can react with H₂O₂ under acid microenvironment to produce Mn²⁺ and O₂. In vivo experiments demonstrated that MnO₂@PA NPs oligomer can passively accumulate in tumor tissue, and the accumulated NPs can produce Mn²⁺ and O₂ for MRI and targeting therapy of osteosarcoma. In conclusion, we prepared a novel bone-targeting nano theranostics for MRI and therapy of osteosarcoma.

Nanoparticles for imaging-guided photothermal therapy of colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies with a high mortality rate worldwide. While surgery, chemotherapy, and radiotherapy have shown some effectiveness in improving survival rates, they come with drawbacks such as side effects and harm to healthy tissues. The theranostic approach, which integrates the processes of cancer diagnosis and treatment, can minimize biological side effects. Photothermal therapy (PTT) is an emerging treatment method that usages light-sensitive agents to generate heat at the tumor site and induce thermal erosion. The development of nanotechnology for CRC treatment using imaging-guided PTT has garnered significant. Nanoparticles with suitable physical and chemical properties can enhance the efficiency of cancer diagnosis and PTT. This approach enables the monitoring of cancer treatment progress and safeguards healthy tissues. In this article, we concisely introduce the application of metal nanoparticles, polymeric nanoparticles, and carbon nanoparticles in imaging-guided PTT of colorectal cancer.

Research progress in green synthesis of manganese and manganese oxide nanoparticles in biomedical and environmental applications - A review

Nanomaterials and nanotechnology have this unassailable position for environmental remediation and medicine. Currently, global environmental pollution and public health problems are increasing and need to be urgently addressed. Manganese (Mn) is one of the essential metal elements for plants and animals, it is necessary to integrate with nanotechnology. Mn and Mn oxide (MnO) nanoparticles (NPs) have applications in dye degradation, biomedicine, electrochemical sensors, plant and animal growth, and catalysis. However, the current research is limited, especially in terms of optimal synthesis of Mn and MnO NPs, separation, purification conditions, and the development of potential application areas is too basic and do not support by in-depth studies. Hence, this review comprehensively discusses the classification, green synthesis methods, and applications of Mn and MnO NPs in biomedical, environmental, and other fields and gives a perspective for the future.

Multifunctional and multimodality theranostic nanomedicine for enhanced phototherapy

Photodynamic therapy (PDT) has attracted much attention in recent years for its favorable therapeutic efficacy in cancer therapy. However, PDT alone is insufficient to improve the therapeutic efficiency mainly due to the limited penetration depth of light, the insufficient O₂ supply in the hypoxic microenvironment, and the high level of reducing substances in cancer cells. To overcome these limitations, a multifunctional MnO₂ nanoparticle was constructed with honeycomb MnO₂ which was loaded with the photosensitizer Ce6 and modified with polydopamine on its surface (HMnO₂/C&P) to achieve efficient PDT/mild photothermal treatment (PTT) combination therapy. HMnO₂/C&P had high drug loading contents (11.2% Ce6) and can be responsive to the tumor microenvironment (TME), supply O₂ to alleviate the hypoxic microenvironment, and clear GSH to reduce the consumption of ROS, thus enhancing the PDT effect. The introduction of PDA can improve the stability of HMnO₂/C&P, and further give the ability of PTT to act as nanomedicine. The results of in vitro and in vivo experiments show that HMnO₂/C&P based PDT/mild PTT combination therapy has an excellent inhibitory effect on tumor growth. Meanwhile, HMnO₂/C&P can act as a fluorescence imaging reagent and a TME triggerable magnetic resonance imaging (MRI) contrast agent, thus having excellent multimodal self-tracking abilities. Collectively, this study provides a new perspective on the design of multifunctional theranostic nanomedicine to maximize the efficacy of cancer phototherapy.

Advances of MnO2 nanomaterials as novel agonists for the development of cGAS-STING-mediated therapeutics

As an essential micronutrient, manganese plays an important role in the physiological process and immune process. In recent decades, cGAS-STING pathway, which can congenitally recognize exogenous and endogenous DNA for activation, has been widely reported to play critical roles in the innate immunity against some important diseases, such as infections and tumor. Manganese ion (Mn²⁺) has been recently proved to specifically bind with cGAS and activate cGAS-STING pathway as a potential cGAS agonist, however, is significantly restricted by the low stability of Mn²⁺ for further medical application. As one of the most stable forms of manganese, manganese dioxide (MnO₂) nanomaterials have been reported to show multiple promising functions, such as drug delivery, anti-tumor and anti-infection activities. More importantly, MnO₂ nanomaterials are also found to be a potential candidate as cGAS agonist by transforming into Mn²⁺, which indicates their potential for cGAS-STING regulations in different diseased conditions. In this review, we introduced the methods for the preparation of MnO₂ nanomaterials as well as their biological activities. Moreover, we emphatically introduced the cGAS-STING pathway and discussed the detailed mechanisms of MnO₂ nanomaterials for cGAS activation by converting into Mn²⁺. And we also discussed the application of MnO₂ nanomaterials for disease treatment by regulating cGAS-STING pathway, which might benefit the future development of novel cGAS-STING targeted treatments based on MnO₂ nanoplatforms.

A cancer cell membrane coated nanoparticles-based gene delivery system for enhancing cancer therapy

Gene therapy is a superior therapeutic means in cancer therapy. However, the instability of nucleic acid and the lack of suitable delivery carrier greatly restricts its further development and application. Herein, we coupled low molecular weight polyethyleneimine (LMW PEI) through disulfide bonds, then modified it with manganese dioxide (MnO2) nanosheets and nuclear localization signal peptide (NLS), as a p53 gene carrier, and finally coated it with B16F10 cell membrane to construct a novel gene-carrier system CM@MnO2-PEI-NLS-ss/p53 (M@MPNs/p53). Tumor cell membrane coating endows nanoparticles with homotypic targeting and immune escape capabilities, disulfide-crosslinked LMW-PEI has high transfection efficiency and low toxicity, and NLS peptides enhance nuclear delivery and improve p53 gene delivery efficiency; meanwhile, MnO2 nanosheets oxidize high intracellular concentration of glutathione (GSH), sensitizing p53 gene-mediated antitumor therapy. The results showed that the novel biofilm-camouflaged M@MPNs/p53 nanoparticles had a highly specific targeting effect on homologous cancer cells and could effectively inhibit tumor growth in vitro and in vivo. Besides, MnO2 loading improved p53-mediated tumor regression. This novel gene delivery platform is of great significance in improving gene delivery efficiency and enhancing anti-tumor therapy.

MnO2 coated multi-layer nanoplatform for enhanced sonodynamic therapy and MR imaging of breast cancer

Sonodynamic therapy (SDT) is a promising new anti-tumor therapy that inhibits tumor growth by ultrasound activation of sonosensitizers to produce reactive oxygen species (ROS). However, the problems of hypoxia in the microenvironment within solid tumors and the effectiveness of SDT will decrease due to the little accumulation of sonosensitizers at the tumor site, as well as tumor cell tolerance, have limited the development of SDT. To overcome these problems, a core-shell structured nanoparticle (IR780/PLGA@MnO2 NPs) loaded with IR780 and manganese dioxide (MnO2) was developed as a nanocarrier to transport the sonosensitizer IR780 and the generated oxygen into the tumor tissue. The MnO2 shell layer of IR780/PLGA@MnO2 NPs can prevent the premature release of IR780 in the blood and also it can react with acidic and high H2O2, the generated oxygen can relieve tumor tissue hypoxia, and the generated Mn can enhance magnetic resonance imaging (MRI) signal intensity by acting as a contrast agent for MRI. More importantly, the released IR780 can produce ROS to kill tumor cells under ultrasound excitation. This PH-responsive and H2O2-triggered SDT based on the IR780/PLGA@MnO2NPs is an effective platform to inhibit tumor growth with negligible systemic toxicity. This work develops a multifunctional therapeutic integrated nanoplatform for breast cancer treatment, which is expected to be used in the clinic.

Sheet-like 2D Manganese(IV) Complex with High Photothermal Conversion Efficiency

We report a stable, water-soluble, mononuclear manganese(IV) complex [Mn^IV(H₂L)]·5H₂O (Mn-HDCL) that acts as an efficient photothermal material. This system is based on a hexahydrazide clathrochelate ligand (L/HDCL) and is obtained via an efficient one-pot templated synthesis that avoids the need for harsh reaction conditions. Scanning tunneling microscopy images reveal that Mn-HDCL exists as a 2D sheet-like structure. In Mn-HDCL, the manganese(IV) ion is trapped within the cavity of the cage-like ligand. This effectively shields the Mn(IV) ion from the external environment while providing adequate water solubility. As a result of orbital transitions involving the coordinated manganese(IV) ion, as well as metal-to-ligand charge transfer effects, Mn-HDCL possesses a large extinction coefficient and displays a photothermal performance comparable to single-wall carbon nanotubes in the solid state. A high photothermal conversion efficiency (ca. 71%) was achieved in aqueous solution when subjected to near-infrared 730 nm laser photo-irradiation. Mn-HDCL is paramagnetic and provides a modest increase in the T₁-weighted contrast of magnetic resonance images both in vitro and in vivo. Mn-HDCL was found to target tumors passively and allow tumor margins to be distinguished in vivo in a mouse model. In addition, it also exhibited an efficient laser-triggered photothermal therapy effect in vitro and in vivo. We thus propose that Mn-HDCL could have a role to play as a tumor-targeting photothermal sensitizer.

Ultrasound and laser-promoted dual-gas nano-generator for combined photothermal and immune tumor therapy

The combination of photothermal therapy (PTT) and immune tumor therapy has emerged as a promising avenue for cancer treatment. However, the insufficient immune response caused by inefficient immunogenic cell death (ICD) inducers and thermal resistance, immunosuppression, and immune escape resulting from the hypoxic microenvironment of solid tumors severely limit its efficacy. Herein, we report an ultrasound and laser-promoted dual-gas nano-generator (calcium carbonate-polydopamine-manganese oxide nanoparticles, CPM NPs) for enhanced photothermal/immune tumor therapy through reprogramming tumor hypoxic microenvironment. In this system, CPM NPs undergo reactive decomposition in a moderately acidic tumor, resulting in the generation of calcium, manganese ions, carbon dioxide (CO₂), and oxygen (O₂). Calcium and manganese ions act as adjuvants that trigger an immune response. The cancer cell membrane rupture caused by sudden burst of bubbles (CO₂ and O₂) under ultrasound stimulation and the photothermal properties of PDA also contributed to the ICD effect. The generation of O₂ alleviates tumor hypoxia and thus reduces hypoxia-induced heat resistance and immunosuppressive effects, thereby improving the therapeutic efficacy of combination PTT and immune therapy. The present study provides a novel approach for the fabrication of a safe and effective tumor treatment platform for future clinical applications.

Biomineralized Manganese Oxide Nanoparticles Synergistically Relieve Tumor Hypoxia and Activate Immune Response with Radiotherapy in Non-Small Cell Lung Cancer

Radiotherapy (RT) is currently considered as an essential treatment for non-small cell lung cancer (NSCLC); it can induce cell death directly and indirectly via promoting systemic immune responses. However, there still exist obstacles that affect the efficacy of RT such as tumor hypoxia and immunosuppressive tumor microenvironment (TME). Herein, we report that the biomineralized manganese oxide nanoparticles (Bio-MnO₂ NPs) prepared by mild enzymatic reaction could be a promising candidate to synergistically enhance RT and RT-induced immune responses by relieving tumor hypoxia and activating cGAS-STING pathway. Bio-MnO₂ NPs could convert endogenic H₂O₂ to O₂ and catalyze the generation of reactive oxygen species so as to sensitize the radiosensitivity of NSCLC cells. Meanwhile, the release of Mn²⁺ into the TME significantly enhanced the cGAS-STING activity to activate radio-immune responses, boosting immunogenic cell death and increasing cytotoxic T cell infiltration. Collectively, this work presents the great promise of TME reversal with Bio-MnO₂ NPs to collaborate RT-induced antitumor immune responses in NSCLC.

Effects of biodegradable biomedical porous MnO2 nanoparticles on blood components and functions

In recent years, manganese dioxide (MnO₂) nanoparticles with unique physicochemical properties have been widely used in many biomedical fields, such as biosensors, contrast agents, tumor therapy, and drug delivery. From these applications, MnO₂ nanoparticles have great clinical translation potential. However, by contrast, the in vitro and in vivo biosafety of MnO₂ nanoparticles have been deeply and thoroughly clarified for the clinical translation, which hinders their clinical applications. In this work, we deeply investigated the blood safety of MnO₂ nanoparticles by conducting a series of in vitro and in vivo experiments. These included the effects of MnO₂ nanoparticles on morphology of red blood cells, activation of platelets, coagulation functions, and toxicity of key organs. The obtained results show that these effects displayed a concentration-dependent manner of MnO₂ nanoparticles. Different safe concentration ranges could be found in the different experimental index. This study provides important guidance for the specific biomedical applications of MnO₂ nanoparticles, greatly accelerating their laboratory development and clinical translation.

Heat-Confined Tumor-Docking Reversible Thermogel Potentiates Systemic Antitumor Immune Response During Near-Infrared Photothermal Ablation in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) features immunologically "cold" tumor microenvironments with limited cytotoxic T lymphocyte (CTL) infiltration. Although ablation therapies have demonstrated modulation of "cold" TNBC tumors to inflamed "hot" tumors, recruitment of myeloid derived suppressor cells (MDSCs) at the tumors post ablation therapies prevents the infiltration of CTLs and challenge the antitumor potentials of T-cell therapies. Here, a thermal ablation immunotherapy strategy is developed to prevent the immune suppressive effects of MDSCs during photothermal ablation and induce a durable systemic antitumor immunity to eradicate TNBC tumors. An injectable pluronic F127/hyaluronic acid (HA)-based hydrogel embedded with manganese dioxide (BM) nanoparticles and TLR7 agonist resiquimod (R848) (BAGEL-R848), is synthesized to induce in situ laser-assisted gelation of the hydrogel and achieve desired ablation temperatures at a low laser-exposure time. Upon 808-nm laser irradiation, a significant reduction in the tumor burden is observed in BAGEL-R848-injected 4T1 tumor-bearing mice. The ablation induced immunogenic cell death and sustained release of R848 from BAGEL-R848 promotes dendritic cell maturation and reduced MDSCs localization in tumors. In addition, inflammatory M1 macrophages and CD8+IFN+ CTL are enriched in distant tumors in bilateral 4T1 tumor model, preventing metastatic tumor growth and signifying the potential of BAGEL-R848 to treat TNBC.

In situ synthesis of fluorescent polydopamine on biogenic MnO2 nanoparticles as stimuli responsive multifunctional theranostics

Multifunctional nanocomposites have drawn great attention in clinical applications because of their ability to integrate diagnostic and therapeutic functions. Manganese dioxide (MnO₂), owing to its biocompatibility and magnetic resonance imaging (MRI) properties, has been widely applied in biomedical research. Our previous work on biogenic MnO₂ nanoparticles (Bio-MnO₂ NPs) revealed that intrinsic photothermal properties and stimuli-responsive MRI imaging are particularly promising for the development of theranostic systems. However, further improvement in the photothermal therapy (PTT) performance of Bio-MnO₂ NPs is still required. Herein, we have improved the PTT efficiency of Bio-MnO₂ NPs by in situ synthesis of fluorescent polydopamine (PDA) while generating additional stimuli responsive fluorescence properties in this system, thus further broadening the scope of their theranostic functions. These synthesis conditions are mild and green. The fluorescence of PDA was quenched by capping Bio-MnO₂ NPs and could be recovered upon degradation of Bio-MnO₂ NPs inside tumour cells. Additionally, Mn²⁺ released from the nanoparticles can support T₁-weighted MR imaging. Compared to the Bio-MnO₂ NPs alone, the integration of Bio-MnO₂ NPs and PDA significantly enhances the photothermal performance in vitro and in vivo. With their high biocompatibility, these multifunctional composite nanodevices hold great potential for fluorescence imaging and MRI-guided photothermal therapy.