Phosphorus and Nitrogen Dual-Doped Hollow Carbon Dot as a Nanocarrier for Doxorubicin Delivery and Biological Imaging

Anticancer activity of quantum size carbon dots: opportunities and challenges

Research into the anticancer activity of quantum-sized carbon dots (CDs) has emerged as a promising avenue in cancer research. This CDs delves into the opportunities and challenges associated with harnessing the potential of these nanostructures for combating cancer. Quantum-sized carbon dots, owing to their unique physicochemical properties, exhibit distinct advantages as potential therapeutic agents. Opportunities lie in their tunable size, surface functionalization capabilities, and biocompatibility, enabling targeted drug delivery and imaging in cancer cells. However, we include challenges, a comprehensive understanding of the underlying mechanisms, potential toxicity concerns, and the optimization of synthesis methods for enhanced therapeutic efficacy. A succinct summary of the state of the research in this area is given in this review, emphasizing the exciting possibilities and ongoing challenges in utilizing quantum-sized carbon dots as a novel strategy for cancer treatment.

Phosphorus Modulated Peroxidase-Like Activity of Carbon Dots for Colorimetric Detection of Acid Phosphatase

The precise regulation of nanoenzyme activity is of great significance for application to biosensing analysis. Herein, the peroxidase-like activity of carbon dots was effectively modulated by doping phosphorus, which was successfully employed for sensitive, selective detection of acid phosphatase (ACP). Phosphorus-doped carbon dots (P-CDs) with excellent peroxidase-like activity were synthesized by a one-pot hydrothermal method, and the catalytic activity could be easily modulated by controlling the additional amount of precursor phytic acid. P-CDs could effectively catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue TMB oxidation products in the presence of hydrogen peroxide. While ACP was able to catalyze the hydrolysis of L-ascorbyl-2-phosphate trisodium salt (AAP) to produce ascorbic acid (AA), which inhibited the peroxidase-like activity of P-CDs, by combining P-CDs nanoenzymes and ACP-catalyzed hydrolysis the colorimetric method was established for ACP detection. The absorbance variation showed a good linear relationship with ACP concentration in the range of 0.4-4.0 mU/mL with a limit of detection at 0.12 mU/mL. In addition, the method was successfully applied to detect ACP in human serum samples with recoveries in the range of 98.7-101.6%. The work provides an effective strategy for regulating nanoenzymes activity and a low-cost detection technique for ACP.

Novel Drug Delivery Systems: An Important Direction for Drug Innovation Research and Development

The escalating demand for enhanced therapeutic efficacy and reduced adverse effects in the pharmaceutical domain has catalyzed a new frontier of innovation and research in the field of pharmacy: novel drug delivery systems. These systems are designed to address the limitations of conventional drug administration, such as abbreviated half-life, inadequate targeting, low solubility, and bioavailability. As the disciplines of pharmacy, materials science, and biomedicine continue to advance and converge, the development of efficient and safe drug delivery systems, including biopharmaceutical formulations, has garnered significant attention both domestically and internationally. This article presents an overview of the latest advancements in drug delivery systems, categorized into four primary areas: carrier-based and coupling-based targeted drug delivery systems, intelligent drug delivery systems, and drug delivery devices, based on their main objectives and methodologies. Additionally, it critically analyzes the technological bottlenecks, current research challenges, and future trends in the application of novel drug delivery systems.

Carbon Dot Based Carbon Nanoparticles as Potent Antimicrobial, Antiviral, and Anticancer Agents

Antimicrobial and anticancer drugs are widely used due to increasing widespread infectious diseases caused by microorganisms such as bacterial, fungal, viral agents, or cancer cells, which are one of the major causes of mortality globally. Nevertheless, several microorganisms developed resistance to antibiotics as a result of genetic changes that have occurred over an extended period. Carbon-based materials, particularly carbon dots (C-dots), are potential candidates for antibacterial and anticancer nanomaterials due to their low toxicity, ease of synthesis and functionalization, high dispersibility in aqueous conditions, and promising biocompatibility. In this Review, the content is divided into four sections. The first section concentrates on C-dot structures, surface functionalization, and morphology. Following that, we summarize C-dot classifications and preparation methods such as arc discharge, laser ablation, electrochemical oxidation, and so on. The antimicrobial applications of C-dots as antibacterial, antifungal, and antiviral agents both in vivo and in vitro are discussed. Finally, we thoroughly examined the anticancer activity displayed by C-dots.

Effective Combination of Targeted Therapies with Sonodynamic Treatment for Use in Exploring Differences in Therapeutic Efficacy across Organelle Targets

Acoustic kinetic therapy systems that target specific organelles can improve the precision of a sonosensitizer, which is a perfect combination of targeted therapy and sonodynamic therapy (SDT) and plays an important role in current acoustic kinetic therapy. In this study, we loaded PpIX, a sonosensitizer, on targeted-functional carbon dots (CDs) via an amide reaction and then generated the mitochondria-targeted system (Mit-CDs-PpIX) and nucleus-targeted system (Nuc-CDs-PpIX), respectively, to deliver the sonosensitizer. Both systems exhibited minimal cytotoxicity in the absence of ultrasound stimulation. The efficacy of the targeted SDT systems was investigated using methylthiazol tetrazolium (MTT) assays, live/dead staining, flow cytometry, etc. Compared with the free PpIX and mitochondria-targeted system, the nucleus-targeted system is more potent in killing effect under ultrasound stimulation and induces apoptosis with higher intensity. To achieve the equal killing effect, the effective concentration of Nuc-CDs-PpIX is just one third of that of Mit-CDs-PpIX.

WO3 nanosheets with peroxidase-like activity and carbon dots based ratiometric fluorescent strategy for xanthine oxidase activity sensing and inhibitor screening

The abnormal level of xanthine oxidase (XOD) often causes pathological changes, which are related to a series of diseases. Herein, a novel and sensitive ratiometric fluorescent sensing platform based on WO3 nanosheets and carbon dots (CDs) was constructed to detect XOD activity for the first time. Under the catalytic oxidation of xanthine by XOD, hydrogen peroxide (H2O2) was generated. In the presence of H2O2, WO3 nanosheets were able to catalyze the oxidation of o-phenylenediamine to generate 2,3-diaminophenazine (DAP) with a yellow fluorescence signal at 570 nm due to its great peroxidase-like activity. The oxidation product DAP was capable of quenching the fluorescence of CDs at 430 nm through the inner filter effect. Therefore, the fluorescence intensity ratio F570/F430 can be used for quantitative analysis of XOD activity. This assay displayed good linear relationships in the range of 0.005-0.05 U/L and 0.5-40 U/L with a detection limit of 0.002 U/L. In addition, this ratiometric fluorescent sensing platform was successfully applied to the determination of XOD in human serum samples and XOD inhibitor screening, demonstrating significant potential in disease diagnosis and drug-screening applications.

Carbon Dots from Tire Waste for the Photodegradation of Methyl Orange Dye, Antimicrobial Activity, and Molecular Docking Study

In this study, solvothermal pathway was employed for the synthesis of P, N codoped C-dot using tire waste as a sustainable source of carbon and nitrogen. Comprehensive analyses encompassing X-ray diffraction (XRD) analysis, Transmission Electron Microscopy (TEM), FT-IR, cyclic voltammetry, and UV-Vis spectra were used to assess the crystalline structure, purity, size, fluorescence up-conversion, and morphological attributes of the nanomaterial. Subsequently, the produced C-dots were evaluated for their efficacy in the photocatalytic degradation of methylene blue and methyl orange dyes, demonstrating notable success in degrading methyl orange dye within eight hours in the visible region. Furthermore, the same nanomaterial was applied for carrying out agar disk-diffusion assays against a spectrum of microorganisms. Results revealed substantial inhibition zones against Methicillin-Resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa. Elucidating the antimicrobial mechanism, molecular-docking simulations were excuted using on AutoDock Vina with designated ligands. The results indicated a strong binding affinity of the C-dots with certain proteins associated with antibacterial activity. This observation suggests that the synthesized C-dots effectively engage with the active sites of these proteins, indicating their potential as promising antibacterial agents. Importantly, this study implies that C-dots do not induce protein denaturation, thereby warranting further investigation of their utility as antibacterial agents.

Red Emission Carbon Nanoparticles Which Can Simultaneously Responding to Hypochlorite and pH

Multi-targets detection has obtained much attention because this sensing mode can realize the detection of multi-targets simultaneously, which is helpful for biomedical analysis. Carbon nanoparticles have attracted extensive attention due to their superior optical and chemical properties, but there are few reports about red emission carbon nanoparticles for simultaneous detection of multi-targets. In this paper, a red emission fluorescent carbon nanoparticles were prepared by 1, 2, 4-triaminobenzene dihydrochloride at room temperature. The as-prepared red emission fluorescent carbon nanoparticles exhibited strong emission peak located at 635 nm with an absolute quantum yield up to 24%. They showed excellent solubility, high photostability and good biocompatibility. Furthermore, it could sensitively and selectively response to hypochlorite and pH, thus simultaneous detection of hypochlorite and pH was achieved by combining the red emission fluorescent carbon nanoparticles with computational chemistry. The formation mechanisms of red emission fluorescent carbon nanoparticles and their response to hypochlorite and pH were investigated, respectively.

Application and Research Status of Long-Wavelength Fluorescent Carbon Dots

This article discusses the application and research status of long-wavelength fluorescent carbon dots. Currently, there are two main methods for synthesising carbon dots (CDs), either from top to bottom, according to the bulk material, or from bottom to top, according to the small molecules. In previous research, mainly graphite and carbon fibres were used as raw materials with which to prepare CDs, using methods such as arc discharge, laser corrosion, and electrochemistry. These preparation methods have low quantum efficiencies and afford CDs that are limited to blue short-wavelength light emissions. With advancing research, the raw materials used for CD preparation have expanded from graphite to biomaterials, such as strawberry, lime juice, and silkworm chrysalis, and carbon-based molecules, such as citric acid, urea, and ethylenediamine (EDA). The preparation of CDs using carbon-based materials is more rapid and convenient because it involves the use of microwaves, ultrasonication, and hydrothermal techniques. Research on developing methods through which to prepare CDs has made great progress. The current research in this regard is focused on the synthesis of CDs, including long-wavelength fluorescent CDs, with a broader range of applications.

Drug-Primed Self-Assembly of Platinum-Single-Atom Nanozyme to Regulate Cellular Redox Homeostasis Against Cancer

Single-atom nanozymes (SAzymes) with high catalytic activity exhibit the potential to disequilibrate the reactive oxygen metabolic balance in the tumor microenvironment (TME), which contains several endogenous reductive substances such as glutathione (GSH). Herein, a novel nano-assembly (CDs@Pt SAs/NCs@DOX) is first constructed using drug-primed platinum (Pt) single-atom or nanocluster nanozymes with a Pt loading of 34.8%, which exhibits prominent dual enzymatic activities to mimic peroxidase (POD) and glutathione oxidase (GSHOx). The unique GSHOx-like activity can efficiently scavenge GSH with a relatively low Km (1.04 mm) and high Vmax (7.46 × 10-6  m s-1 ), thus avoiding single oxygen (1 O2 ) depletion. CDs@Pt SAs/NCs@DOX simultaneously demonstrates low-temperature photothermal therapy and TME- or laser-controlled disassembly and drug release, which can effectively regulate cellular redox homeostasis and achieve high tumor growth inhibition. These outcomes may provide promising strategies for the preparation of Pt SAzymes with multiple activities and variable-sized nano-assemblies, allowing for broader applications of SAzymes and nano-assemblies in the biomedical field.

Luminescence of carbon quantum dots and their application in biochemistry

Similar to fullerenes, carbon nanotubes and graphene, carbon dots (CDs) are causing a lot of research work in their own right. CDs are a type of surface-passivated quantum dot that contain carbon atoms. Their distinctive characteristics, such as luminescent emission that varies with size and wavelength, resistance to photobleaching, easy biological binding, lack of toxicity, and economical production without the need for intricate synthetic processes, have led to a noteworthy surge in attention within the research community. Different techniques can be utilized to create these CDs, spanning from basic candle burning to laser ablation. This review article delves into the principles of fluorescence technology, providing insights into how different synthesis methods of quantum dots impact their luminescent properties. Additionally, it highlights the latest applications of quantum dots in catalysis and biomedical fields, with special emphasis on the current status of luminescent properties in biology and chemistry. Towards the end, the article discusses the limitations of quantum dots in current practical applications, pointing out that CDs hold promising potential for future applications.

Therapeutic Potential of Nanomedicine in Management of Alzheimer's Disease and Glioma

Neoplasm (Glioblastoma) and Alzheimer's disease (AD) comprise two of the most chronic psychological ailments. Glioblastoma is one of the aggressive and prevalent malignant diseases characterized by rapid growth and invasion resulting from cell migration and degradation of extracellular matrix. While the latter is characterized by extracellular plaques of amyloid and intracellular tangles of tau proteins. Both possess a high degree of resistance to treatment owing to the restricted transport of corresponding drugs to the brain protected by the blood-brain barrier (BBB). Development of optimized therapies using advanced technologies is a great need of today. One such approach is the designing of nanoparticles (NPs) to facilitate the drug delivery at the target site. The present article elaborates the advances in nanomedicines in treatment of both AD as well as Gliomas. The intention of this review is to provide an overview of different types of NPs with their physical properties emphasizing their importance in traversing the BBB and hitting the target site. Further, we discuss the therapeutic applications of these NPs along with their specific targets. Multiple overlapping factors with a common pathway in development of AD and Glioblastoma are discussed in details that will assist the readers in developing the conceptual approach to target the NP for an aging population in the given circumstances with limitations of currently designed NPs, and the challenges to meet and the future perspectives.

A narrative review on the role of carbon nanoparticles in oncology

The lymphatic system is the first site of metastasis for most tumors and is a common reason for the failure of cancer therapy. The lymphatic system's anatomical properties make it difficult to deliver chemotherapy agents at therapeutic concentrations while avoiding systemic toxicity. Carbon nanoparticles offer a promising alternative for identifying and transporting therapeutic molecules. The larger diameter of lymphatic vessels compared to the diameter of blood vessels, allows carbon nanoparticles to selectively enter the lymphatic system once administered subcutaneously. Carbon nanoparticles stain tumor-draining lymph nodes black following intratumoral injection, making them useful in sentinel lymph node mapping. Drug-loaded carbon nanoparticles allow higher concentrations of chemotherapeutics to accumulate in regional lymph nodes while decreasing plasma drug accumulation. The use of carbon nanoparticles for chemotherapy delivery has been associated with lower mortality, fewer histopathology changes in vital organs, and lower serum concentrations of hepatocellular enzymes. This review will focus on the ability of carbon nanoparticles to target the lymphatics as well as their current and potential applications in sentinel lymph node mapping and oncology treatment regimens. This article is categorized under: Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

Synthesis of luminescent chitosan-based carbon dots for Candida albicans bioimaging

In this work, we used chitosan as a raw material to synthesize carbon dots using fast microwave carbonization. We studied the influence of the synthesis time, doping agent, and the molar ratio between the reactants on the quantum yield of carbon dots. Chitosan-based carbon dots displayed stable blue fluorescence emission with excitation-dependent behavior and quantum yield values ranging from 1.16 to 7.07 %. ANOVA results showed that the interaction factor between the doping agent and the molar ratio of the reactants was a significant combination to produce carbon dots with higher quantum yield. The presence of the doping agent improved the carbon dots optical properties by obtaining higher fluorescence intensity values. Confocal laser microscope images showed that the carbon dots internalized in the Candida albicans cellular membrane, exhibiting blue, green, and red emissions, acting as a promising agent for bioimaging.

High quantum yield carbon dots and nitrogen-doped carbon dots as fluorescent probes for spectroscopic dopamine detection in human serum

Recent advances in fluorescent carbon dots have shown great potential for the sensing of biological molecules. In this study, one-step hydrothermally synthesised carbon dots (CD) and nitrogen doped carbon dots (NCD) with high quantum yields of 54.29% and 89.82%, respectively, were investigated and demonstrated to be a reliable, cost-effective, and naked-eye fluorescent probe for the detection of dopamine, a neurotransmitter, in human serum fluids. The current study is well supported by a comprehensive synthesis approach and has been described utilizing a variety of microscopic and spectroscopic techniques. The discovered approach is time and pH dependent, and it provides a robust platform for specifically detecting aberrant dopamine levels using a fluorescence quenching mechanism. Dopamine detection limits for CD were calculated to be 5.54 μM for CD and 5.12 μM for NCD, respectively. The fluorescence quenching shows a linear continuous trend with a range within 3.3-500 μM and 3.3-400 μM of dopamine concentration for CD and NCD respectively. To further verify the sensitivity of CD and NCD as fluorescent probes, interference studies in the presence of different biological components were also studied and validated. This work shows that carbon-based nanomaterials and their doped nanostructures, due to their high fluorescence, have significant potential as fluorescent probes in neurological disease diagnosis as they display high selectivity, sensitivity and fast responses in the real time spectroscopic detection of dopamine in human fluid samples.

Heteroatom Codoped Graphene: The Importance of Nitrogen

Although graphene has exceptional properties, they are not enough to solve the extensive list of pressing world problems. The substitutional doping of graphene using heteroatoms is one of the preferred methods to adjust the physicochemical properties of graphene. Much effort has been made to dope graphene using a single dopant. However, in recent years, substantial efforts have been made to dope graphene using two or more dopants. This review summarizes all the hard work done to synthesize, characterize, and develop new technologies using codoped, tridoped, and quaternary doped graphene. First, I discuss a simple question that has a complicated answer: When can an atom be considered a dopant? Then, I briefly discuss the single atom doped graphene as a starting point for this review's primary objective: codoped or dual-doped graphene. I extend the discussion to include tridoped and quaternary doped graphene. I review most of the systems that have been synthesized or studied theoretically and the areas in which they have been used to develop new technologies. Finally, I discuss the challenges and prospects that will shape the future of this fascinating field. It will be shown that most of the graphene systems that have been reported involve the use of nitrogen, and much effort is needed to develop codoped graphene systems that do not rely on the stabilizing effects of nitrogen. I expect that this review will contribute to introducing more researchers to this fascinating field and enlarge the list of codoped graphene systems that have been synthesized.

Fabrication of Porous Fe-Based Metal-Organic Complex for the Enhanced Delivery of 5-Fluorouracil in In Vitro Treatment of Cancer Cells

Metal-organic complexes are one of the most studied materials in the last few decades, which are fabricated from organic ligands and metal ions to form robust frameworks with porous structures. In this work, iron-1,4-benzenedicarboxylic-polyethylene glycol (Fe-BDC-PEG) with a porous structure was successfully constructed by an iron(III) benzene dicarboxylate and polyethylene glycol diacid. The drug-delivery properties of the resultant Fe-BDC-PEG were tested for the loading and release of the 5-fluorouracil compound. The maximal loading capacity of Fe-BDC-PEG for 5-fluorouracil was determined to be 348.22 mg/g. The drug release of 5-fluorouracil-loaded Fe-BDC-PEG after 7 days was 92.69% and reached a maximum of 97.52% after 10 days. The 7 day and acute oral toxicity of Fe-BDC-PEG in mice were studied. The results show that no reasonable change or mortality was observed upon administration of Fe-BDC-PEG complex in mice at 10 g/kg body weight. When the uptake of Fe-BDC-PEG particles in mice was continued for 7 consecutive days, the mortality, feed consumption, body weight, and daily activity were negligibly changed.

Developing Carbon Dots with Room-Temperature Phosphorescence for the Dual-Signal Detection of Metronidazole

Room-temperature phosphorescent carbon dots (CDs) show the advanced property owing to their dual signal; howbeit, acquiring the efficient phosphorescence of CDs is still challengeable. Here, we proposed one type of CD doped with nitrogen through the microwave method, which exhibited the obvious blue fluorescence in aqueous solution and green phosphorescence immobilized on filter paper, while diethylenetriamine pentamethylene phosphonic acid provided the source of carbon and nitrogen. Importantly, introducing metronidazole (MNZ) into the CDs leads to their simultaneous decrease in both fluorescence and phosphorescence, and thus, we successfully established a dual-signal strategy for detecting MNZ. Likewise, this fluorescent detection showed the linear range of 2-200 μM and the phosphorescent way of 50-2000 μM. Meanwhile, the corresponding detection mechanism was also explored, and both the quenched fluorescence and phosphorescence of CDs were mainly due to the occurrence of the electron transfer and internal filtration effect between CDs and MNZ. Additionally, we employed these CDs as the fluorescent and phosphorescent inks for painting and information encryption.

Insight into the Modulation of Carbon-Dot Optical Sensing Attributes through a Reduction Pathway

Oxidized/reduced carbon dots (CDs) with tunable optical features have emerged as a new class of CDs having a common "molecular origin" but different fluorescence (FL) behaviors. In the present work, using "banana peel" as a sole carbon source followed by doping with fluorine (F), boron (B), and nitrogen (N) over CDs, banana peel-derived carbon dots (BP-CDs) were synthesized using a well-known hydrothermal synthesis method. Moreover, as-synthesized BP-CDs were further reduced to "rBP-CDs" by NaBH4. At post reduction, the FL performance (i.e., quantum yield) of rBP-CDs were found to be enhanced compared with the BP-CDs, along with variations in excitation and emission wavelengths. Interestingly, the optical sensing attributes of BP-CDs and rBP-CDs were varied, that is, BP-CDs selectively sense "Co2+ with a limit of detection (LOD) value of 180 nM", whereas rBP-CDs detected Co2+ (with an LOD value of 242 nM) as well as Hg2+ (with an LOD value of 190 nM). To the best of our knowledge, this work presents the very first report on the modulation of CDs' sensing behavior after reduction. The modulation in the sensing behavior with the common carbon precursor and reduction paves a new possibility for exploring CDs for different commercial applications.

Nitrogen-doped carbon dots coupled with morin-Al3+: Cleverly design an integrated sensing platform for ratiometric optical dual-mode and smartphone-assisted visual detection of fluoride ion

Ratiometric fluorescence sensor has high selectivity and good sensitivity; however, its development is limited by intricate design, tedious synthesis, etc. Herein, a facile and effective ratiometric fluorescence sensing platform for fluoride ion (F^-) detection was developed by simply combining nitrogen-doped carbon dots (N-CDs) and morin-Al³⁺ based on inner filter effect (IFE). The competitive binding of F^- to Al³⁺ obviously decreased morin-Al³⁺ fluorescence and increased N-CDs fluorescence, attributing to the inhibition of IFE between N-CDs and morin-Al³⁺. The as-constructed ratiometric fluorescence sensing platform can be used for F^- detection with a wide linear range (0.5-150 μM) and a low detection limit (55.8 nM). Interestingly, with the introduction of F^- into the N-CDs/morin-Al³⁺ sensing platform, a distinguishable change in fluorescence color from green to blue enabled the N-CDs/morin-Al³⁺ system to be used as a smartphone-assisted visual sensing platform for F^- detection with a detection limit of 2.09 μM. This platform was successfully applied for the onsite monitoring of F^- in various water samples with satisfying results. These findings provide a novel guidance for the facile construction of a ratiometric optical dual-mode and smartphone-assisted sensing platform based on CDs, revealing the broad application prospect of CDs in environmental monitoring field.

pH-Responsive Hyperbranched Polymer Nanoparticles to Combat Intracellular Infection by Disrupting Bacterial Wall and Regulating Macrophage Polarization

Intracellular bacterial infections pose a serious threat to public health. Macrophages are a heterogeneous population of immune cells that play a vital role in intracellular bacterial infection. However, bacteria that survive inside macrophages could subvert the cell signaling and eventually reduce the antimicrobial activity of macrophages. Herein, dual pH-responsive polymer (poly[(3-phenylprop-2-ene-1,1-diyl)bis(oxy)bis(enthane-2,1-diyl)diacrylate-co-N-aminoethylpiperazine] (PCA)) nanoparticles were developed to clear intracellular bacteria by activating macrophages and destructing bacterial walls. The presence of acid-labile acetal linkages and tertiary amine groups in the polymer's backbone endow hyperbranched PCA dual pH-response activity that shows acid-induced positive charge increase and cinnamaldehyde release properties. The biodegraded PCA nanoparticles could significantly inhibit the growth of bacteria by damaging the bacterial walls. Meanwhile, PCA nanoparticles could uptake by macrophages, generate reactive oxygen species (ROS), and remodel the immune response by upregulating M1 polarization, leading to the reinforced antimicrobial capacity. Furthermore, PCA nanoparticles could promote bacteria-infected wound healing in vivo. Therefore, these dual pH-responsive PCA nanoparticles enabling bacteria-killing and macrophage activation provide a novel outlook for treating intracellular infection.

A novel carbon-nanodots-based theranostic nano-drug delivery system for mitochondria-targeted imaging and glutathione-activated delivering camptothecin

Chemotherapy is severely limited by continuously decreased therapeutic efficacy and uncontrolled side effects on normal tissue, which can be improved by constructing a nanoparticle-based drug delivery system (DDS). Nevertheless, no studies have reported on DDS-based on carbon-nanodots (CNDs), combining subcellular organelle-targeted imaging/drug delivery, high drug loading content, and glutathione (GSH)-sensitive drug release into one system. Herein, the as-fabricated CNDs can be covalently conjugated with a mitochondria-targeting ligand (triphenylphosphine, TPP), a smart GSH-responsive disulfide linker (S-S), and the anticancer drug (camptothecin, CPT) to initially prepare a theranostic nano-DDS (TPP-CNDs-S-CPT) with the drug loading efficiency of 64.6 wt%. Owing to excellent water dispersibility, superior fluorescence properties, satisfactory cell permeability, and favorable biocompatibility, TPP-CNDs-S-CPT was successfully used for intracellular mitochondrial-targeted imaging in vitro. High intracellular GSH concentrations in tumor cells caused the cleavage of S-S, resulting in concomitant activation and release of CPT, as well as significant fluorescence enhancement. In vivo, TPP-CNDs-S-CPT exhibited lower biological toxicity and even higher tumor-activatable performance than free CPT, as well as specific cancer therapy with few side effects. The mitochondria-targeted ability and the precise drug-release in tumor make TPP-CNDs-S-CPT a hopeful chemotherapy prodrug, providing significant theoretical basis and data support for in-depth understanding and exploration of chemotherapeutic DDS-based on CNDs.

Highly Luminescent Nucleoside-Based N, P-Doped Carbon Dots for Sensitive Detection of Ions and Bioimaging

The efficient detection of Fe3+ and MnO4− in a water environment is very important and challenging due to their harmful effects on the health of humanity and environmental systems. Good biocompatibility, sensitivity, selectivity, and superior photophysical properties were important attributes of carbon dot-based CDs sensors for sensing applications. In this work, we synthesized N, P-co-doped carbon dots (N/P CDs) with guanosine 5′-monophosphate (GMP) as a green carbon source, with high fluorescence quantum yield in water (QY, 53.72%). First, the luminescent N/P CDs showed a three-state “on-off-on” fluorescence response upon the sequential addition of Fe3+ and F−, with a low detection limit of 12 nM for Fe3+ and 8.5 nM for F−, respectively. Second, the N/P CDs also exhibited desirable selectivity and sensitivity for toxic MnO4− detection with the limit of detection of 18.2 nM, through a turn-off mechanism. Moreover, the luminescent N/P CDs successfully monitored the aforementioned ions in environmental water samples and in Escherichia coli.

Visual Monitoring of Nucleic Acid Dynamic Structures during Cellular Ferroptosis Using Rationally Designed Carbon Dots with Robust Anti-Interference Ability to Reactive Oxygen Species

Ferroptosis triggered by an iron-dependent accumulation of lipid reactive oxygen species (ROS) has drawn widespread attention. Directly visualizing the dynamic structures of nucleic acids during the ferroptosis of cells is of great importance considering their vital roles in numerous biological functions. However, direct imaging remains challenging, largely due to the extremely high concentrations of ROS generated during ferroptosis, which can affect the imaging of nucleic acid targeted fluorescent probes. To overcome this challenge, nucleic acid-responsive carbon dots (CDs) providing favorable optical properties together with high chemical stability were synthesized. Furthermore, the CDs penetrated the cell membrane quickly and accumulated in the nuclei of cells. The robust anti-interference ability to ROS allows the CDs to visualize the dynamic structures of nucleic acids during ferroptosis. Moreover, the CDs were successfully employed in the imaging of nucleic acids during cell division. The nuclei-targeting CDs show great potential as a powerful tool for imaging nuclei in ferroptosis-related biological and clinical research.

A Strategic Review on Carbon Quantum Dots for Cancer-Diagnostics and Treatment

The understanding of the genesis of life-threatening cancer and its invasion calls for urgent development of novel technologies for real-time observations, early diagnosis, and treatment. Quantum dots (QDs) grabbed the spotlight in oncology owing to their excellent photostability, bright fluorescence, high biocompatibility, good electrical and chemical stability with minimum invasiveness. Recently, carbon QDs (CQDs) have become popular over toxic inorganic QDs in the area of bioimaging, biosensing, and drug delivery. Further, CQDs derived from natural sources like biomolecules and medicinal plants have drawn attention because of their one-pot, low-cost and ease of synthesis, along with remarkable tunable optical properties and biocompatibility. This review introduces the synthesis and properties of CQDs derived from natural sources, focusing on the applicability of CQD-based technologies as nano-theranostics for the diagnosis and treatment of cancer. Furthermore, the current issues and future directions for the transformation of CQDs-based nanotechnologies to clinical applications are highlighted.

Intelligently design primary aromatic amines derived carbon dots for optical dual-mode and smartphone imaging detection of nitrite based on specific diazo coupling

Primary aromatic amines derived carbon dots (PAA-CDs) with the protonated amino groups and high quantum yield of 46% were favorably obtained by one-step solvothermal treatment of m-phenylenediamine (m-PDA) in acidic environment. The interaction between the PAA-CDs and nitrite (NO₂^-) was inherited the characteristic reaction of m-PDA (a primary aromatic amine) and NO₂^-, resulting in strong fluorescence quenching and obvious absorption variation of the PAA-CDs. Meanwhile, a chromogenic reaction of diazo coupling can cause significant color changes. Hence, the PAA-CDs were developed for an optical dual-mode and smartphone imaging sensor for NO₂^- detection in the range of 3.0 ~ 40.0 μM with high selectivity, good sensitivity, and excellent anti-interference capability. A limit of detection (LOD) of 0.024 μM and 0.16 μM was implemented by fluorometry and colorimetry, respectively. For smartphone imaging colorimetry, the LODs of 0.46 μM (visible color) and 0.99 μM (fluorescence color) were acquired. More importantly, the established sensor has been successfully applied for the dynamic detection of NO₂^- in various food samples with the satisfying results. A smartphone imaging colorimetry method based on the CDs was firstly proposed to visually and quantitatively detect NO₂^-, which will broaden the application range of the CDs in food safety inspection.

Template-Free Synthesis of Porous Fluorescent Carbon Nanomaterials with Gluten for Intracellular Imaging and Drug Delivery

A series of carbon nanomaterials, including carbon dots, carbon nanorings (CNRs), and porous carbon nanoballs, were facilely prepared by a template-free hydrothermal treatment of gluten as the sole carbon source. Driven by the hydrophobicity interaction, a concentration-dependent self-assembly of gluten was observed in an aqueous solution, leading to the subsequent formation of different morphologies of carbon nanomaterials in a hydrothermal treatment. Among these carbon nanomaterials, the CNRs exhibit bright photoluminescence with a quantum yield of 47.0%. Furthermore, CNRs also have a large surface area and low toxicity, making them an excellent drug carrier for chemotherapeutics. A model drug molecule doxorubicin (DOX) was successfully loaded on the CNRs, and the CNRs-DOX complexes exhibit a pH-dependent DOX release behavior. Compared with free DOX, the CNRs-DOX complexes can induce a higher level of apoptosis and lower level of necrosis, showing promise as anticancer agents.

Broadened optical absorption, enhanced photoelectric conversion and ultrafast carrier dynamics of N, P co-doped carbon dots

Carbon dots (CDs) have attracted extensive attention for their unique properties and promising applications in many fields. Many efforts have been made to improve the optical and physicochemical properties of CDs using an atomic doping strategy; however, the photoelectric properties of CD-based devices have been less studied and the photocurrent density is far from satisfactory for practical operation. Deep understanding of the doping effects on the electronic structure and photophysical properties of CDs is fundamental and essential for effectively improving the optical and photoelectrical performance of CD-based devices. Here, we have synthesized nitrogen (N) and phosphorus (P) co-doped CDs (N, P-CDs) through a one-step hydrothermal approach, and systematically investigated the effects of P-dopants on the improved optical and photoelectric properties of N, P-CDs. The introduction of P atoms into N-CDs significantly changes the electronic structure and extends the absorption spectral region, enhancing the light-harvesting ability of N, P-CDs. Meanwhile, the regulated carrier dynamics have been investigated using time-resolved fluorescence and transient absorption spectroscopy. We found that the carrier recombination was decreased with introducing P atoms, and the photogenerated electrons in the higher excited states could be efficiently transferred to the lowest excited state. Moreover, the photocurrent density of N, P-CDs was increased by twelve times compared with that of N-CDs. Therefore, the effective doping of P atoms can significantly regulate the electronic structure, optical properties, carrier dynamics and photoelectric conversion of N, P-CDs. The achieved broadband light-harvesting, good photoelectric properties and photostability of the as-prepared N, P-CDs demonstrate an important example of P-doping to improve the optical and photoelectrical properties of CD-based devices.

Cadmium induced aggregation of orange-red emissive carbon dots with enhanced fluorescence for intracellular imaging

Cadmium is a notorious toxic heavy metal, that poses serious threat to human health. Sensitive and selective detection of cadmium in cells is of great significance in poison screening and disease diagnosis. Orange-red emissive carbon dots (OR-CDs), prepared from the calcination of selected carbon sources 5-amino-1, 10-phenanthroline (Aphen) and salicylic acid (SA), were found to act as a "turn on" type fluorescence probe for Cd²⁺ detection. The structure and optical properties of OR-CDs were comprehensively investigated by both experimental characterizations and density functional theory (DFT) calculations. The OR-CDs consist of a basic unit of nine aromatic rings, and the N/O binding sites on the OR-CDs can specifically bind with Cd²⁺, leading to aggregation induced enhanced emission (AIEE). A detection limit of 0.30 μM was achieved for Cd²⁺ with a linear range of 0.80-100 μM. OR-CDs can not only be used for intracellular Cd²⁺ imaging but also have the potential to alleviate cadmium poison in living organisms.

F,N-Doped carbon dots as efficient Type I photosensitizers for photodynamic therapy

Photodynamic therapy (PDT) is a promising and emerging method for the treatment of cancer. Usually, Type II PDT is used in the clinic, and mainly involves three key elements: a photosensitizer, molecular oxygen and laser light. However, it is known that tumor tissue is deficient in oxygen molecules which is why Type I PDT is mostly preferred in the therapy of tumors in which the hypoxic tissue plays a major role. Fluorescent carbon dots (CDs) have shown great potential in cancer theranostics, acting as bioimaging agents and photosensitizers. Herein, we have synthesized novel kinds of fluorine and nitrogen co-doped carbon dots (F,NCDs) that emit bright green fluorescence under ultra-violet light. The F,NCDs have excellent water solubility and low cytotoxicity. They can generate hydroxyl radicals (˙OH) and superoxide anions (˙O2-) under LED light (400-500 nm, 15 mW cm-2) irradiation, making them ideal photosensitizers for Type I PDT. Furthermore, upon using the HepG2 cell line as an in vitro model, the F,NCDs exhibit a better cell imaging effect and higher PDT efficiency than the control sample of CDs without F and N doping. This work has illustrated that the F,NCDs are promising in achieving the image-guided PDT of cancers, usually in a hypoxia tumor microenvironment.

Nicotinamide-Functionalized Carbon Quantum Dot as New Sensing Platform for Portable Quantification of Vitamin B12 in Fluorescence, UV-Vis and Smartphone Triple Mode

Development of an efficient, portable and simple nanosensor-based systems with reliable analytical performance for on-site monitoring of vitamin B12 (VB12) are still major problems and a challenging work for quality control of manufacturers. Herein, a new fluorescence, UV-Vis and smartphone triple mode nanosensors were designed for the simultaneous detection of VB12 with high sensitivity and accuracy. A novel nanosensor was synthesized through nicotinamide-functionalizing of carbon quantum dot (NA-CQDs) by an one-step microwave-assisted method with green approach. The NA-CQDs sensor showed excellent fluorescence properties and wide linear ranges from 0.1-60 µM with the detection limits of 31.7 nM. Moreover, color changes of NA-CQDs induced by the VB12 could also be detected by UV-Vis spectrophotometer and inhouse-developed application installed on smartphone as a signal reader, simultanusly. The Red, Green and Blue (RGB) intensities of the colorimetric images of NA-CQDs/VB12 system which taken by smartphone's camera converted into quantitative values by the application. A smartphone-integrated with NA-CQDs as colorimetric sensing platform displays good linear ranges (4.16 to 66.6 μM) for on-site determination of VB12 with detection limit of 1.40 μM. The method was successfully applied in the determination of VB12 in complex pharmaceutical supplement formulations without any sample pre-treatment and matrix interfering effects. The recovery results (96.52% to 105.10%) which were in agreement with the reference methods, demonstrating the capability of the smartphone-assisted colorimetric sensing platform in many on-site practical applications of quality controls.

Two-photon excitable membrane targeting polyphenolic carbon dots for long-term imaging and pH-responsive chemotherapeutic drug delivery for synergistic tumor therapy

Long-term dynamic tracking of cells with theranostics properties remains challenging due to difficulty in preparing and delivering drugs by the probes. Herein, we developed a highly fluorescent one- and two-photon...

Mapping the Time Dependent DNA Fragmentation caused by doxorubicin Loaded on PEGylated Carbogenic Nanodots using Fluorescence Lifetime Imaging and Super-resolution microscopy

Doxorubicin is an anthracycline drug most commonly used in cancer therapy. It intercalates with the nuclear DNA and induces toxicity by causing DNA breaks and histone evictions. However, the kinetics...

Ultrasonic-Assisted Synthesis of Fe-BTC-PEG Metal-Organic Complex: An Effective and Safety Nanocarrier for Anticancer Drug Delivery

The porous metal-organic complexes are emerging as novel carriers for effective and safe delivery of drugs for cancer treatment, minimizing the side effect of drug overuse during cancer treatment. This study fabricated the Fe-BTC-PEG metal-organic complex from Fe ions, trimesic acid, and poly(ethylene glycol) as precursors using an ultrasonic-assisted method. The morphology and crystallinity of the resultant complex were observed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. FTIR spectroscopy was employed to investigate the functional groups on the surface of the Fe-BTC-PEG complex. The result showed that the prepared Fe-BTC-PEG complex was in particle form with low crystallinity and diameter ranging from 100 to 200 nm. The obtained Fe-BTC-PEG complex exhibited a high loading capacity for the 5-fluorouracil (5-FU) anticancer drug with a maximal capacity of 364 mg/g. The releasing behavior of 5-fluorouracil from the 5-FU-loaded Fe-BTC-PEG complex was studied. Notably, the acute oral toxicity of the Fe-BTC-PEG metal-organic complex was also carried out to evaluate the safety of the material in practical application.

A fluorometric and colorimetric dual-readout nanoprobe based on Cl and N co-doped carbon quantum dots with large stokes shift for sequential detection of morin and zinc ion

A novel visual nanoprobe was developed for the sequential detection of morin and zinc ion (Zn²⁺) based on Cl and N co-doped carbon quantum dots (ClNCQDs) via a fluorometric and colorimetric dual-readout mode. The yellow fluorescence ClNCQDs was synthesized by the one-step hydrothermal treatment of o-chlorobenzoic acid and p-phenylenediamine. The most distinctive property of the ClNCQDs is the large stokes shift (177 nm), which is significantly higher than other reported CQDs. The fluorescence of the ClNCQDs can be effectively quenched by morin based on the synergistic effect of IFE, electrostatic interaction, and dynamic quenching process, and recovered upon the addition of Zn²⁺ due to strong interaction between morin and Zn²⁺. The nanoprobe exhibited favorable selectivity and sensitivity toward morin and Zn²⁺ with detection limits of 0.09 µM and 0.17 µM, respectively. Simultaneously, the color of the ClNCQDs solution was changed (light-pink → faint-yellow → dark-yellow) along with the variation of the fluorescence signal of the ClNCQDs. This proposed nanoprobe was successfully applied for morin and Zn²⁺ analyses in actual samples and live cells with high accuracy. The results of this study demonstrate the great application prospects of the ClNCQDs for morin and Zn²⁺ detection in complex actual samples and biosystems.

Recent Advances in Functional Carbon Quantum Dots for Antitumour

Carbon quantum dots (CQDs) are an emerging class of quasi-zero-dimensional photoluminescent nanomaterials with particle sizes less than 10 nm. Owing to their favourable water dispersion, strong chemical inertia, stable optical performance, and good biocompatibility, CQDs have become prominent in biomedical fields. CQDs can be fabricated by “top-down” and “bottom-up” methods, both of which involve oxidation, carbonization, pyrolysis and polymerization. The functions of CQDs include biological imaging, biosensing, drug delivery, gene carrying, antimicrobial performance, photothermal ablation and so on, which enable them to be utilized in antitumour applications. The purpose of this review is to summarize the research progress of CQDs in antitumour applications from preparation and characterization to application prospects. Furthermore, the challenges and opportunities of CQDs are discussed along with future perspectives for precise individual therapy of tumours.

Fluorescent and colorimetric dual-mode detection of tetracycline in wastewater based on heteroatoms-doped reduced state carbon dots

A large amount of tetracycline (TC) persists in water, soil, food, and feed due to the overuse of antibiotics, causing serious environmental problems such as damage to ecosystems and posing risks to human health. Thus, there is an urgent need to find a method to detect TC that is practical, rapid, sensitive, and offers ready visualization of TC levels so that adequate remediation measures can be immediately implemented. Herein, we report a fluorescent and colorimetric dual-mode nanosensor for the detection of TC based on reduced state carbon dots (r-CDs). In the presence of TC, the emission fluorescence of r-CDs was quenched by the Förster resonance energy transfer mechanism to achieve high-sensitivity detection of TC with a low limit of detection (LOD) of 1.73 nM. Moreover, TC was also detected by r-CDs via a noticeable color change of the solution (from colorless to red) with the naked eye, having an LOD of 0.46 μM. Furthermore, r-CDs have excellent selectivity and sensitivity in detecting TC in wastewater, and therefore, have practical applications in wastewater treatment. The fluorescent and colorimetric dual-mode proposed in this work may offer a unique idea for the detection of TC, with great prospects for environmental wastewater applications.

State of the Art and Perspectives on the Biofunctionalization of Fluorescent Metal Nanoclusters and Carbon Quantum Dots for Targeted Imaging and Drug Delivery

The interface of nanobio science and cancer nanomedicine is one of the most important current frontiers in research, being full of opportunities and challenges. Ultrasmall fluorescent metal nanoclusters (MNCs) and carbon quantum dots (CQDs) have emerged as promising fluorescent nanomaterials due to their unique physicochemical and optical properties, facile surface functionalization, good photostability, biocompatibility, and aqueous dispersity. These characteristics make them advantageous over conventional fluorophores such as organic dye molecules and semiconductor quantum dots (QDs) for the detection, diagnosis, and treatment of various diseases including cancer. Recently, researchers have focused on the biofunctionalization strategy of the MNCs and CQDs which can tailor their physicochemical and biological properties and, in turn, can empower these biofunctionalized nanoprobes for diverse applications including imaging, drug delivery, theranostics, and other biomedical applications. In this invited feature article, we first discuss some fundamental structural and physicochemical characteristics of the fluorescent biocompatible quantum-sized nanomaterials which have some outstanding features for the development of multiplexed imaging probes, delivery vehicles, and cancer nanomedicine. We then demonstrate the diverse surface engineering of these fluorescent nanomaterials with reactive target specific functional groups which can help to construct multifunctional nanoprobes with improved targeting capabilities having minimal toxicity. The promising future of the biofunctionalized fluorescent quantum-sized nanomaterials in the field of bioanalytical and biomedical research is elaborately demonstrated, showing selected recent works with relevant applications. This invited feature article finally ends with a short discussion of the current challenges and future prospects of the development of these bioconjugated/biofunctionalized nanomaterials to provide insight into this burgeoning field of MNC- and CQD-based diagnostics and therapeutic applications.

Uptake of carbon nanodots into human AML cells in comparison to primary hematopoietic cells

Carbon nanodots (CNDs) comprise a class of next generation nanomaterials with a wide variety of potential applications. Here, we report on their uptake into primary hematopoietic cells from three normal donors and malignant cells from five patients with de novo acute myeloid leukemia (AML). A significant CND uptake was observed in all cell types of the normal and leukemic cells. Still, the uptake was significantly smaller for the CD34⁺ and CD33⁺ myeloid subsets of the malignant cell population as compared to the normal blood-derived CD34⁺ and CD33⁺ cells. For the T and B lymphoid cell populations as defined by CD3 and CD19 within the leukemic and normal samples a similar uptake was observed. The CNDs accumulate preferentially in small clusters in the periphery of the nucleus as already shown in previous studies for CD34⁺ progenitor/stem cells and human breast cancer cells. This particular subcellular localization could be useful for targeting the lysosomal compartment, which plays a pivotal role in the context of autophagy associated survival of AML cells. Our results demonstrate the usability of CNDs beyond their application for in vitro and in vivo fluorescence labeling or drug delivery into normal and malignant cells.

Carbon nanodots (CNDs) comprise a class of next generation nanomaterials with a wide variety of potential applications.

Carbon Dots: A Future Blood-Brain Barrier Penetrating Nanomedicine and Drug Nanocarrier

Drug delivery across the blood-brain barrier (BBB) is one of the biggest challenges in modern medicine due to the BBB's highly semipermeable property that limits most therapeutic agents of brain diseases to enter the central nervous system (CNS). In recent years, nanoparticles, especially carbon dots (CDs), exhibit many unprecedented applications for drug delivery. Several types of CDs and CD-ligand conjugates have been reported successfully penetrating the BBB, which shows a promising progress in the application of CD-based drug delivery system (DDS) for the treatment of CNS diseases. In this review, our discussion of CDs includes their classification, preparations, structures, properties, and applications for the treatment of neurodegenerative diseases, especially Alzheimer's disease (AD) and brain tumor. Moreover, abundant functional groups on the surface, especially amine and carboxyl groups, allow CDs to conjugate with diverse drugs as versatile drug nanocarriers. In addition, structure of the BBB is briefly described, and mechanisms for transporting various molecules across the BBB and other biological barriers are elucidated. Most importantly, recent developments in drug delivery with CDs as BBB-penetrating nanodrugs and drug nanocarriers to target CNS diseases especially Alzheimer's disease and brain tumor are summarized. Eventually, future prospects of the CD-based DDS are discussed in combination with the development of artificial intelligence and nanorobots.