A Smart Near-Infrared Carbon Dot-Metal Organic Framework Assemblies for Tumor Microenvironment-Activated Cancer Imaging and Chemodynamic-Photothermal Combined Therapy

A new strategy of using low-dose caffeic acid carbon nanodots for high resistance to poorly differentiated human papillary thyroid cancer

Thyroid cancer is one of the most common endocrine malignancies in clinical practice. Traditional surgery and radioactive iodine ablation have poor treatment results for poorly differentiated thyroid cancer, and there is a risk of metastasis and recurrence. In this study, caffeic acid, a natural herbal extract with certain biological activity, has been as precursor to prepare new caffeic acid carbon nanodots via a one-step hydrothermal method. The caffeic acid carbon nanodots retains part of the structure and biological activity of caffeic acid, and have good biocompatibility, water solubility and stability. The construction of the carbon nanodots could effectively improve their bio-absorption rate and the efficacy. In vitro cell experiments showed that low-dose caffeic acid carbon nanodots had a significant inhibitory effect on poorly differentiated papillary thyroid carcinoma BCPAP cells. At low concentrations of 16 µg/mL, the inhibition rate of human thyroid cancer cells BCPAP was ~ 79%. The anti-tumor mechanism was predicted and verified by transcriptome, real-time quantitative PCR and western blot experiments. The caffeic acid carbon nanodots showed to simultaneously downregulate the expression of KRAS, p-BRAF, p-MEK1 and p-ERK1/2, the four continuous key proteins in a MAPK classical signaling pathway. In vivo experiments further confirmed the caffeic acid carbon nanodots could significantly inhibit the tumorigenicity of xenografts in papillary thyroid carcinoma at quite low doses. This piece of work provides a new nanomedicine and therapeutic strategy for highly resistant poorly differentiated papillary thyroid carcinoma.

Synthesis and Characterization of Copper-Crosslinked Carbon Dot Nanoassemblies for Efficient Macrophage Manipulation

Nanomedicines loaded in macrophages (MAs) can actively target tumors without dominantly relying on the enhanced permeability and retention (EPR) effect, making them effective for treating EPR-deficient malignancies. Herein, copper-crosslinked carbon dot clusters (CDCs) are synthesized with both photodynamic and chemodynamic functions to manipulate MAs, aiming to direct the MA-mediated tumor targeting. First, green fluorescent CDs (g-CDs) are prepared by a one-step hydrothermal method. Subsequently, the g-CDs are complexed with divalent copper ions to form copper-crosslinked CDCs (g-CDCs/Cu), which are incubated with MAs for their manipulation. Experimental results revealed that the prepared g-CDCs/Cu displayed good aqueous dispersibility and fluorescent emission properties. The nanoassemblies can be activated to deplete the overexpressed glutathione (GSH) and generate reactive oxygen species (ROS) in the presence of laser irradiation through the combined Cu-mediated chemodynamic therapy and CD-mediated photodynamic therapy. Furthermore, the ROS produced in MAs enabled polarization of MAs to antitumor M1 phenotype, suggesting the future potential use to reverse the immunosuppressive tumor microenvironment. These results obtained from the current study suggest a significant potential to develop g-CDCs/Cu for GSH depletion, ROS generation, and MA M1 polarization as a theransotic agent to tackle cancer.

Carbon Dots in the Pathological Microenvironment: ROS Producers or Scavengers?

Reactive oxygen species (ROS), as metabolic byproducts, play pivotal role in physiological and pathological processes. Recently, studies on the regulation of ROS levels for disease treatments have attracted extensive attention, mainly involving the ROS-induced toxicity therapy mediated by ROS producers and antioxidant therapy by ROS scavengers. Nanotechnology advancements have led to the development of numerous nanomaterials with ROS-modulating capabilities, among which carbon dots (CDs) standing out as noteworthy ROS-modulating nanomedicines own their distinctive physicochemical properties, high stability, and excellent biocompatibility. Despite progress in treating ROS-related diseases based on CDs, critical issues such as rational design principles for their regulation remain underexplored. The primary cause of these issues may stem from the intricate amalgamation of core structure, defects, and surface states, inherent to CDs, which poses challenges in establishing a consistent generalization. This review succinctly summarizes the recently progress of ROS-modulated approaches using CDs in disease treatment. Specifically, it investigates established therapeutic strategies based on CDs-regulated ROS, emphasizing the interplay between intrinsic structure and ROS generation or scavenging ability. The conclusion raises several unresolved key scientific issues and prominent technological bottlenecks, and explores future perspectives for the comprehensive development of CDs-based ROS-modulating therapy.

High-temperature PTT/CDT coordination nanoplatform realizing exacerbated hypoxia for enhancing hypoxia-activated chemotherapy to overcome tumor drug resistance

BACKGROUND

Hypoxia-activated prodrugs present new opportunities for safe and effective tumor drug resistance therapy due to their high selectivity for hypoxic cells. However, the uneven distribution of oxygen in solid tumor and insufficient hypoxia in the tumor microenvironment greatly limit its therapeutic efficacy.

RESULTS

In this paper, a novel AQ4N-Mn(II)@PDA coordination nanoplatform was designed and functionalized with GMBP1 to target drug-resistant tumor cells. Its excellent photothermal conversion efficiency could achieve local high-temperature photothermal therapy in tumors, which could not only effectively exacerbate tumor hypoxia and thus improve the efficacy of hypoxia-activated chemotherapy of AQ4N but also significantly accelerate Mn2+-mediated Fenton-like activity to enhance chemodynamic therapy. Moreover, real-time monitoring of blood oxygen saturation through photoacoustic imaging could reflect the hypoxic status of tumors during treatment. Furthermore, synergistic treatment effectively inhibited tumor growth and improved the survival rate of mice bearing orthotopic drug-resistant tumors.

CONCLUSIONS

This study not only provided a new idea for PTT combined with hypoxia-activated chemotherapy and CDT for drug-resistant tumors but also explored a vital theory for real-time monitoring of hypoxia during treatment.

Metal-organic framework (MOF)/C-dots and covalent organic framework (COF)/C-dots hybrid nanocomposites: Fabrications and applications in sensing, medical, environmental, and energy sectors

Developing new hybrid materials is critical for addressing the current needs of the world in various fields, such as energy, sensing, health, hygiene, and others. C-dots are a member of the carbon nanomaterial family with numerous applications. Aggregation is one of the barriers to the performance of C-dots, which causes luminescence quenching, surface area decreases, etc. To improve the performance of C-dots, numerous matrices including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and polymers have been composited with C-dots. The porous crystalline structures, which are constituents of metal nodes and organic linkers (MOFs) or covalently attached organic units (COFs) provide privileged features such as high specific surface area, tunable structures, and pore diameters, modifiable surface, high thermal, mechanical, and chemical stabilities. Also, the MOFs and COFs protect the C-dots from the environment. Therefore, MOF/C-dots and COF/C-dots composites combine their features while retaining topological properties and improving performances. In this review, we first compare MOFs with COFs as matrices for C-dots. Then, the recent progress in developing hybrid MOFs/C-dots and COFs/C-dots composites has been discussed and their applications in various fields have been explained briefly.

pH-responsive iron-loaded carbonaceous nanoparticles for chemodynamic therapy based on the Fenton reaction

The Fenton reaction-based chemodynamic therapy is a form of cancer therapy, and its efficacy can be significantly improved by promoting catalytic reactions involving iron ions. A system with high catalytic capacity and low biological toxicity that effectively inhibits tumor progression is required for optimal treatment. In this study, iron-loaded carbonaceous nanoparticles (CNPs@Fe) with Fenton catalytic activity were fabricated and applied for the chemodynamic therapy of cancer. The carbonaceous nanoparticles derived from glucose via a caramelization reaction demonstrated high biocompatibility. Besides, aromatic structures in the carbonaceous nanoparticles helped accelerate electron transfer to enhance the catalytic decomposition of H2O2, resulting in the formation of highly reactive hydroxyl radicals (˙OH). At pH 6.0 (representing weak acidity in the tumor microenvironment), the Fenton catalytic activity of CNPs@Fe in the decomposition of H2O2 was 15.3 times higher than that of Fe2+ and 28.3 times higher than that of Fe3O4via a chromogenic reaction. The reasons for the enhancement were revealed by analyzing the chemical composition of carbonaceous nanoparticles using high-resolution mass spectra. The developed Fenton agent also demonstrated significant therapeutic effectiveness and minimal side effects in in vitro and in vivo anticancer studies. This work proposes a novel approach to promote the generation of reactive oxygen species (ROS) for the chemodynamic therapy of cancer.

A copper-loaded self-assembled nanoparticle for disturbing the tumor redox balance and triple anti-tumor therapy

Both chemodynamic therapy and photodynamic therapy, based on the production of reactive oxygen (ROS), have excellent potential in cancer therapy. However, the abnormal redox homeostasis in tumor cells, especially the overexpressed glutathione (GSH) could scavenge ROS and reduce the anti-tumor efficiency. Therefore, it is essential to develop a simple and effective tumor-specific drug delivery system for modulating the tumor microenvironment (TME) and achieving synergistic therapy at the tumor site. In this study, self-assembled nanoparticles (named CDZP NPs) were developed using copper ion (Cu2+), doxorubicin (Dox), zinc phthalocyanine (ZnPc) and a trace amount of poly(2-(di-methylamino)ethylmethacrylate)-poly[(R)-3-hydroxybutyrate]-poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA-PHB-PDMAEMA) through chelation, π-π stacking and hydrophobic interaction. These triple factor-responsive (pH, laser and GSH) nanoparticles demonstrated unique advantages through the synergistic effect. Highly controllable drug release ensured its effectiveness at the tumor site, Dox-induced chemotherapy and ZnPc-mediated fluorescence (FL) imaging exhibited the distribution of nanoparticles. Meanwhile, Cu2+-mediated GSH-consumption not only reduced the intracellular ROS elimination but also produced Cu+ to catalyze hydrogen peroxide (H2O2) and generated hydroxyl radicals (˙OH), thereby enhancing the chemodynamic and photodynamic therapy. Herein, this study provides a green and relatively simple method for preparing multifunctional nanoparticles that can effectively modulate the TME and improve synergetic cancer therapy.

Nanomaterials-Induced Redox Imbalance: Challenged and Opportunities for Nanomaterials in Cancer Therapy

Cancer cells typically display redox imbalance compared with normal cells due to increased metabolic rate, accumulated mitochondrial dysfunction, elevated cell signaling, and accelerated peroxisomal activities. This redox imbalance may regulate gene expression, alter protein stability, and modulate existing cellular programs, resulting in inefficient treatment modalities. Therapeutic strategies targeting intra- or extracellular redox states of cancer cells at varying state of progression may trigger programmed cell death if exceeded a certain threshold, enabling therapeutic selectivity and overcoming cancer resistance to radiotherapy and chemotherapy. Nanotechnology provides new opportunities for modulating redox state in cancer cells due to their excellent designability and high reactivity. Various nanomaterials are widely researched to enhance highly reactive substances (free radicals) production, disrupt the endogenous antioxidant defense systems, or both. Here, the physiological features of redox imbalance in cancer cells are described and the challenges in modulating redox state in cancer cells are illustrated. Then, nanomaterials that regulate redox imbalance are classified and elaborated upon based on their ability to target redox regulations. Finally, the future perspectives in this field are proposed. It is hoped this review provides guidance for the design of nanomaterials-based approaches involving modulating intra- or extracellular redox states for cancer therapy, especially for cancers resistant to radiotherapy or chemotherapy, etc.

Dual chemodynamic/photothermal therapeutic nanoplatform based on DNA-functionalized prussian blue

The combination of chemodynamic therapy and photothermal therapy has a promising application owing to its impressive anti-cancer effects. However, the degradability of the material and the lack of targeting severely limit its further clinical application. Herein, DNAs containing nucleolin aptamer (AS1411) and different bases sequences were used to functionalize PB NPs for the targeted treatment. Compared to prussian blue, DNA-functionalized prussian blue does not reduce the photothermal properties of prussian blue. Moreover, DNA confers DNA-functionalized prussian blue targeting and higher enzymatic activity, thereby achieving a more effective combination of chemodynamic and photothermal treatment. The therapeutic efficacy of this nanoplatform was evaluated in vivo and in vitro experiments, exhibiting that DNA-functionalized prussian blue nanozyme can maximize the precise control of the therapeutic effect, reduce the toxic and side effects caused by non-specific accumulation on other normal cells, and effectively achieve targeted killing of cancer cells. This work demonstrates that DNA-functionalized prussian blue can improve the efficiency of combined tumor treatment and enhance the application value of prussian blue in tumor treatment, which is expected to provide theoretical support for clinical application.

Near-Infrared Fluorescent Silica Nanoparticles Based on Gold-Silver Alloy Nanoclusters for Clinical Diagnosis

In clinical diagnosis, fluorescent particles are applied to detect analytes in biofluids, such as blood and saliva. However, current fluorescence detection methods have not been optimized to account for the overlapping autofluorescence peaks of biological substances. Gold and silver nanoclusters are known to the novel fluorescent materials and their emission wavelengths depend on cluster size. In this study, we developed fluorescent silica nanoparticles using gold-silver alloy nanoclusters and chitosan (CS) (NH2-SiO2@Au@CS@AuAg) by the layer-by-layer method. Under UV-light irradiation at 365 nm, the emission wavelength of NH2-SiO2@Au@CS@AuAg reached 750 nm in the near-IR region. Scanning electron microscopy images revealed that the shape of NH2-SiO2@Au@CS@AuAg was uniform and spherical. The fluorescence spectrum of horse blood obtained in the presence of NH2-SiO2@Au@CS@AuAg contained a specific fluorescence peak attributed to NH2-SiO2@Au@CS@AuAg, which was distinguishable from the autofluorescence peaks. These results showed that NH2-SiO2@Au@CS@AuAg has advantageous fluorescence properties for clinical diagnostic applications.

Multifunctional Carbon Dots for Biomedical Applications: Diagnosis, Therapy, and Theranostic

Designing suitable nanomaterials is an ideal strategy to enable early diagnosis and effective treatment of diseases. Carbon dots (CDs) are luminescent carbonaceous nanoparticles that have attracted considerable attention. Through facile synthesis, they process properties including tunable light emission, low toxicity, and light energy transformation, leading to diverse applications as optically functional materials in biomedical fields. Recently, their potentials have been further explored, such as enzyme-like activity and ability to promote osteogenic differentiation. Through refined synthesizing strategies carbon dots, a rich treasure trove for new discoveries, stand a chance to guide significant development in biomedical applications. In this review, the authors start with a brief introduction to CDs. By presenting mechanisms and examples, the authors focus on how they can be used in diagnosing and treating diseases, including bioimaging failure of tissues and cells, biosensing various pathogenic factors and biomarkers, tissue defect repair, anti-inflammation, antibacterial and antiviral, and novel oncology treatment. The introduction of the application of integrated diagnosis and treatment follows closely behind. Furthermore, the challenges and future directions of CDs are discussed. The authors hope this review will provide critical perspectives to inspire new discoveries on CDs and prompt their advances in biomedical applications.

Target Design of Multinary Metal-Organic Frameworks for Near-Infrared Imaging and Chemodynamic Therapy

Imaging-guided chemodynamic therapy is widely considered a promising modality for personalized and precision cancer treatment. Combining both imaging and chemodynamic functions in one system conventionally relies on the hybrid materials approach. However, the heterogeneous, ill-defined, and dissociative/disintegrative nature of the composites tends to complicate their action proceedings in biological environments and thus makes the treatment imprecise and ineffective. Herein, a strategy to employ two kinds of inorganic units with different functions─reactive oxygen species generation and characteristic emission─has achieved two single-crystalline metal-organic frameworks (MOFs), demonstrating the competency of reticular chemistry in creating multifunctional materials with atomic precision. The multinary MOFs could not only catalyze the transformation from H2O2 to hydroxyl radicals by utilizing the redox-active Cu-based units but also emit characteristic tissue-penetrating near-infrared luminescence brought by the Yb4 clusters in the scaffolds. Dual functions of MOF nanoparticles are further evidenced by pronounced cell imaging signals, elevated intracellular reactive oxygen species levels, significant cell apoptosis, and reduced cell viabilities when they are taken up by the HeLa cells. In vivo NIR imaging is demonstrated after the MOF nanoparticles are further functionalized. The independent yet interconnected modules in the intact MOFs could operate concurrently at the same cellular site, achieving a high spatiotemporal consistency. Overall, our work suggests a new method to effectively accommodate both imaging and therapy functions in one well-defined material for precise treatment.

Current status and prospects of MIL-based MOF materials for biomedicine applications

This article mainly reviews the biomedicine applications of two metal-organic frameworks (MOFs), MIL-100(Fe) and MIL-101(Fe). These MOFs have advantages such as high specific surface area, adjustable pore size, and chemical stability, which make them widely used in drug delivery systems. The article first introduces the properties of these two materials and then discusses their applications in drug transport, antibacterial therapy, and cancer treatment. In cancer treatment, drug delivery systems based on MIL-100(Fe) and MIL-101(Fe) have made significant progress in chemotherapy (CT), chemodynamic therapy (CDT), photothermal therapy (PTT), photodynamic therapy (PDT), immunotherapy (IT), nano-enzyme therapy, and related combined therapy. Overall, these MIL-100(Fe) and MIL-101(Fe) materials have tremendous potential and diverse applications in the field of biomedicine.

Recent strategies of carbon dot-based nanodrugs for enhanced emerging antitumor modalities

Nanomaterial-based cancer therapy has recently emerged as a new therapeutic modality with the advantages of minimal invasiveness and negligible normal tissue toxicity over traditional cancer treatments. However, the complex microenvironment and self-protective mechanisms of tumors have suppressed the therapeutic effect of emerging antitumor modalities, which seriously hindered the transformation of these modalities to clinical settings. Due to the excellent biocompatibility, unique physicochemical properties and easy surface modification, carbon dots, as promising nanomaterials in the biomedical field, can effectively improve the therapeutic effect of emerging antitumor modalities as multifunctional nanoplatforms. In this review, the mechanism and limitations of emerging therapeutic modalities are described. Further, the recent advances related to carbon dot-based nanoplatforms in overcoming the therapeutic barriers of various emerging therapies are systematically summarized. Finally, the prospects and potential obstacles for the clinical translation of carbon dot-based nanoplatforms in tumor therapy are also discussed. This review is expected to provide a reference for nanomaterial design and its development for the efficacy enhancement of emerging therapeutic modalities.

Zero-Dimensional Carbon Nanomaterials for Fluorescent Sensing and Imaging

Advances in nanotechnology and nanomaterials have attracted considerable interest and play key roles in scientific innovations in diverse fields. In particular, increased attention has been focused on carbon-based nanomaterials exhibiting diverse extended structures and unique properties. Among these materials, zero-dimensional structures, including fullerenes, carbon nano-onions, carbon nanodiamonds, and carbon dots, possess excellent bioaffinities and superior fluorescence properties that make these structures suitable for application to environmental and biological sensing, imaging, and therapeutics. This review provides a systematic overview of the classification and structural properties, design principles and preparation methods, and optical properties and sensing applications of zero-dimensional carbon nanomaterials. Recent interesting breakthroughs in the sensitive and selective sensing and imaging of heavy metal pollutants, hazardous substances, and bioactive molecules as well as applications in information encryption, super-resolution and photoacoustic imaging, and phototherapy and nanomedicine delivery are the main focus of this review. Finally, future challenges and prospects of these materials are highlighted and envisaged. This review presents a comprehensive basis and directions for designing, developing, and applying fascinating fluorescent sensors fabricated based on zero-dimensional carbon nanomaterials for specific requirements in numerous research fields.

Carbon Quantum Dots Derived from Herbal Medicine as Therapeutic Nanoagents for Rheumatoid Arthritis with Ultrahigh Lubrication and Anti-inflammation

As a typical chronic inflammatory joint disease with swelling and pain syndromes, rheumatoid arthritis (RA) is closely related to articular lubrication deficiency and excessive proinflammatory cytokines in its progression and pathogenesis. Herein, inspired by the dual effects of joint lubrication improvement and anti-inflammation to treat RA, two novel potential therapeutic nanoagents have been developed rationally by employing herbal medicine-derived carbon quantum dots (CQDs), i.e., safflower (Carthamus tinctorius L.) CQDs and Angelica sinensis CQDs, yielding ultrahigh lubrication and anti-inflammation bioefficacy. In vitro experimental results show that the two nanoagents display excellent friction reduction due to their good water solubility and spherical structure. Using RA rat models, it is indicated that the nanoagents significantly relieved swelling symptoms and inhibited the expression of related inflammatory cytokines, including IL-1, IL-6, and TNF-α, indicating their extraordinary anti-inflammation bioefficacy. Thus, combining the lubricating and anti-inflammation bioefficacy of CQDs derived from herbal medicine is an attractive strategy to develop new nanoagents for RA treatment.

Carbon nanodots constructed by ginsenosides and their high inhibitory effect on neuroblastoma

BACKGROUND

Neuroblastoma is one of the common extracranial tumors in children (infants to 2 years), accounting for 8 ~ 10% of all malignant tumors. Few special drugs have been used for clinical treatment currently.

RESULTS

In this work, herbal extract ginsenosides were used to synthesize fluorescent ginsenosides carbon nanodots via a one-step hydrothermal method. At a low cocultured concentration (50 µg·mL^- 1) of ginsenosides carbon nanodots, the inhibition rate and apoptosis rate of SH-SY5Y cells reached ~ 45.00% and ~ 59.66%. The in vivo experiments showed tumor volume and weight of mice in ginsenosides carbon nanodots group were ~ 49.81% and ~ 34.14% to mice in model group. Since ginsenosides were used as sole reactant, ginsenosides carbon nanodots showed low toxicity and good animal response.

CONCLUSION

Low-cost ginsenosides carbon nanodots as a new type of nanomedicine with good curative effect and little toxicity show application prospects for clinical treatment of neuroblastoma. It is proposed a new design for nanomedicine based on bioactive carbon nanodots, which used natural bioactive molecules as sole source.

Photothermal Nanomaterials: A Powerful Light-to-Heat Converter

All forms of energy follow the law of conservation of energy, by which they can be neither created nor destroyed. Light-to-heat conversion as a traditional yet constantly evolving means of converting light into thermal energy has been of enduring appeal to researchers and the public. With the continuous development of advanced nanotechnologies, a variety of photothermal nanomaterials have been endowed with excellent light harvesting and photothermal conversion capabilities for exploring fascinating and prospective applications. Herein we review the latest progresses on photothermal nanomaterials, with a focus on their underlying mechanisms as powerful light-to-heat converters. We present an extensive catalogue of nanostructured photothermal materials, including metallic/semiconductor structures, carbon materials, organic polymers, and two-dimensional materials. The proper material selection and rational structural design for improving the photothermal performance are then discussed. We also provide a representative overview of the latest techniques for probing photothermally generated heat at the nanoscale. We finally review the recent significant developments of photothermal applications and give a brief outlook on the current challenges and future directions of photothermal nanomaterials.

Supramolecular Chemistry of Carbon-Based Dots Offers Widespread Opportunities

Carbon dots are an emerging class of nanomaterials that has recently attracted considerable attention for applications that span from biomedicine to energy. These photoluminescent carbon nanoparticles are defined by characteristic sizes of <10 nm, a carbon-based core and various functional groups at their surface. Although the surface groups are widely used to establish non-covalent bonds (through electrostatic interactions, coordinative bonds, and hydrogen bonds) with various other (bio)molecules and polymers, the carbonaceous core could also establish non-covalent bonds (ππ stacking or hydrophobic interactions) with π-extended or apolar compounds. The surface functional groups, in addition, can be modified by various post-synthetic chemical procedures to fine-tune the supramolecular interactions. Our contribution categorizes and analyzes the interactions that are commonly used to engineer carbon dots-based materials and discusses how they have allowed preparation of functional assemblies and architectures used for sensing, (bio)imaging, therapeutic applications, catalysis, and devices. Using non-covalent interactions as a bottom-up approach to prepare carbon dots-based assemblies and composites can exploit the unique features of supramolecular chemistry, which include adaptability, tunability, and stimuli-responsiveness due to the dynamic nature of the non-covalent interactions. It is expected that focusing on the various supramolecular possibilities will influence the future development of this class of nanomaterials.

Recent developments in carbon dots: a biomedical application perspective

Recently, newly developed carbon-based nanomaterials known as carbon dots (CDs) have generated significant interest in nanomedicine. However, current knowledge regarding CD research in the biomedical field is still lacking. An overview of the most recent development of CDs in biomedical research is given in this review article. Several crucial CD applications, such as biosensing, bioimaging, cancer therapy, and antibacterial applications, are highlighted. Finally, CD-based biomedicine's challenges and future potential are also highlighted to enrich biomedical researchers' knowledge about the potential of CDs and the need for overcoming various technical obstacles.

Self-Assembled Aza-BODIPY and Iron(III) Nanoparticles for Photothermal-Enhanced Chemodynamic Therapy in the NIR-II Window

Despite its promising potential in cancer treatment, synergistic photothermal/chemodynamic therapy remains underdeveloped with regard to the utilization of metal-organic materials under second near-infrared (NIR-II) laser excitation. Herein, we report a three-dimensional network constructed via the metal coordination between catechol-functionalized aza-boron dipyrromethenes and iron ions (ABFe), which was further encapsulated by F127 to obtain ABFe nanoparticles (NPs) for combined photothermal/chemodynamic therapy. ABFe NPs exhibited intense absorption in the NIR-II range and negligible fluorescence. Upon 1064 nm laser irradiation, ABFe NPs showed high photothermal conversion efficiency (PCE = 55.0%) and excellent photothermal stability. The results of electron spin resonance spectra and o-phenylenediamine chromaticity spectrophotometry proved that ABFe NPs were capable of generating harmful reactive oxygen species from hydrogen peroxide for chemodynamic therapy, which was promoted by photothermal performance. Notably, in vitro and in vivo experiments demonstrated the great potential of ABFe NPs in photoacoustic imaging and photothermal-enhanced chemodynamic therapy under NIR-II laser irradiation. Therefore, the current work presents a prospective NIR-II excitation therapeutic nanomedicine for combination therapy, offering a novel strategy for simultaneously achieving extended NIR absorption of aza-BODIPY and enhanced chemodynamic therapy with metal-organic materials.

Carbon dots for photothermal applications

Carbon dots are zero-dimensional nanomaterials that have garnered significant research interest due to their distinct optical properties, biocompatibility, low fabrication cost, and eco-friendliness. Recently, their light-to-heat conversion ability has led to several novel photothermal applications. In this minireview, we categorize and describe the photothermal application of carbon dots along with methods incorporated to enhance their photothermal efficiency. We also discuss the possible mechanisms by which the photothermal effect is realized in these carbon-based nanoparticles. Taken together, we hope to provide a comprehensive landscape highlighting several promising research directions for using carbon dots for photothermal applications.

Assignment of Core and Surface States in Multicolor-Emissive Carbon Dots

It is important to reveal the luminescence mechanisms of carbon dots (CDs). Herein, CDs with two types of optical centers are synthesized from citric acid in formamide by a solvothermal method, and show high photoluminescence quantum yield reaching 42%. Their green/yellow emission exhibits pronounced vibrational structure and high resistance toward photobleaching, while broad red photoluminescence is sensitive to solvents, temperature, and UV-IR. Under UV-IR, the red emission is gradually bleached due to the photoinduced dehydration of the deprotonated surface of CDs in dimethyl sulfoxide, while this process is hindered in water. From the analysis of steady-state and time-resolved photoluminescence and transient absorption data together with density functional theory calculations, the green/ yellow emission is assigned to conjugated sp² -domains (core state) similar to organic dye derivatives stacked within disk-shaped CDs; and the broad red emission-to oxygen-containing groups bound to sp² -domains (surface state), whereas energy transfer from the core to the surface state can happen.

High-efficiency synthesis of red carbon dots using machine learning

Due to their excellent optical properties, red carbon dots (CDs) have been widely used in cell imaging and biomedical therapy. However, the efficiency of red CD synthesis is deficient, and the synthesis cost is high. Here, we propose an efficient synthesis method based on machine learning to assist researchers in synthesizing red fluorescent CDs. This strategy can quickly and efficiently predict the predesigned conditions of CD synthesis. It avoids invalid synthetic experiments and improves the efficiency of red CD synthesis.

Highly Efficient GSH-Responsive "Off-On" NIR-II Fluorescent Fenton Nanocatalyst for Multimodal Imaging-Guided Photothermal/Chemodynamic Synergistic Cancer Therapy

Accurate diagnosis and effective treatment of malignant tumors under the interference of complex and diverse tumor microenvironments (TMEs) have become the focus of research. Herein, an innovative TME-activated biomimetic nanocatalyst with quad-modal imaging capabilities of second near-infrared (NIR-II) "turn-on" fluorescence imaging, magnetic resonance imaging (MRI), photoacoustic imaging (PAI), and photothermal imaging (PTI) was designed and developed for self-enhanced photothermal/chemodynamic synergistic therapy. The catalyst was fabricated by loading glucose oxidase (GOD) and Ag₂S quantum dots (QDs) on MnO₂ nanosheets and coating them with a 4T1 cell membrane (AMG@CM), which enables them to successfully escape immune clearance and have appealing tumor-targeting ability and biocompatibility. The NIR-II fluorescence at 1130 nm of Ag₂S QDs quenched by MnO₂ could be recovered in vivo through the glutathione (GSH)-induced degradation of MnO₂, enabling excellent TME-responsive tumor visualization. Simultaneously, the released Mn²⁺ can catalyze H₂O₂ to produce abundant hydroxyl radicals (•OH), achieving photothermal synergistically enhanced chemodynamic therapy (CDT) under NIR-II radiation. Moreover, the CDT could be self-enhanced by GOD due to the extra produced H₂O₂. This work demonstrates a novel and highly efficient multimodal imaging-guided integrated treatment strategy for dual-enhanced CDT tumor precise diagnosis and treatment.

Research Progress of Photothermal Nanomaterials in Multimodal Tumor Therapy

The aggressive growth of cancer cells brings extreme challenges to cancer therapy while triggering the exploration of the application of multimodal therapy methods. Multimodal tumor therapy based on photothermal nanomaterials is a new technology to realize tumor cell thermal ablation through near-infrared light irradiation with a specific wavelength, which has the advantages of high efficiency, less adverse reactions, and effective inhibition of tumor metastasis compared with traditional treatment methods such as surgical resection, chemotherapy, and radiotherapy. Photothermal nanomaterials have gained increasing interest due to their potential applications, remarkable properties, and advantages for tumor therapy. In this review, recent advances and the common applications of photothermal nanomaterials in multimodal tumor therapy are summarized, with a focus on the different types of photothermal nanomaterials and their application in multimodal tumor therapy. Moreover, the challenges and future applications have also been speculated.

Research Progress on Improving the Efficiency of CDT by Exacerbating Tumor Acidification

In recent years, chemodynamic therapy (CDT) has received extensive attention as a novel means of cancer treatment. The CDT agents can exert Fenton and Fenton-like reactions in the acidic tumor microenvironment (TME), converting hydrogen peroxide (H₂O₂) into highly toxic hydroxyl radicals (·OH). However, the pH of TME, as an essential factor in the Fenton reaction, does not catalyze the reaction effectively, hindering its efficiency, which poses a significant challenge for the future clinical application of CDT. Therefore, this paper reviews various strategies to enhance the antitumor properties of nanomaterials by modulating tumor acidity. Ultimately, the performance of CDT can be further improved by inducing strong oxidative stress to produce sufficient ·OH. In this paper, the various acidification pathways and proton pumps with potential acidification functions are mainly discussed, such as catalytic enzymes, exogenous acids, CAIX, MCT, NHE, NBCn1, etc. The problems, opportunities, and challenges of CDT in the cancer field are also discussed, thereby providing new insights for the design of nanomaterials and laying the foundation for their future clinical applications.