Recent progress of carbon dots in targeted bioimaging and cancer therapy

Biocompatible fluorescent carbon nanoparticles as nanocarriers for targeted delivery of tamoxifen for regression of Breast carcinoma

Breast cancer (BC) is the most common malignancy among females worldwide, and its high metastasis rates are the leading cause of death just after lung cancer. Currently, tamoxifen (TAM) is a hydrophobic anticancer agent and a selective estrogen modulator (SERM), approved by the FDA that has shown potential anticancer activity against BC, but the non-targeted delivery has serious side effects that limit its ubiquitous utility. Therefore, releasing anti-cancer drugs precisely to the tumor site can improve efficacy and reduce the side effects on the body. Nanotechnology has emerged as one of the most important strategies to solve the issue of overdose TAM toxicity, owing to the ability of nano-enabled formulations to deliver desirable quantity of TAM to cancer cells over a longer period of time. In view of this, use of fluorescent carbon nanoparticles in targeted drug delivery holds novel promise for improving the efficacy, safety, and specificity of TAM therapy. Here, we synthesized biocompatible carbon nanoparticles (CNPs) using chitosan molecules without any toxic surface passivating agent. Synthesized CNPs exhibit good water dispersibility and emit intense blue fluorescence upon excitation (360 nm source). The surface of the CNPs has been functionalized with folate using click chemistry to improve the targeted drug uptake by the malignant cell. The pH difference between cancer and normal cells was successfully exploited to trigger TAM release at the target site. After six hours of incubation, CNPs released ∼ 74 % of the TAM drug in acidic pH. In vitro, studies have also demonstrated that after treatment with the synthesized CNPs, significant inhibition of the tumor growth could be achieved.

Novel Carbon Quantum Dots Precisely Trigger Ferroptosis in Cancer Cells through Antioxidant Inhibition Synergistic Nanocatalytic Activity

High levels of glutathione (GSH) are an important characteristic of malignant tumors and a significant cause of ineffective treatment and multidrug resistance. Although reactive oxygen species (ROS) therapy has been shown to induce tumor cell death, the strong clearance effect of GSH on ROS significantly reduces its therapeutic efficacy. Therefore, there is a need to develop new strategies for targeting GSH. In this study, novel carbon quantum dots derived from gentamycin (GM-CQDs) were designed and synthesized. On the basis of the results obtained, GM-CQDs contain sp2 and sp3 carbon atoms as well as nitrogen oxygen groups, which decrease the intracellular levels of GSH by downregulating SLC7A11, thereby disrupting redox balance, mediating lipid peroxidation, and inducing ferroptosis. Transcriptome analysis demonstrated that GM-CQDs downregulated the expression of molecules related to GSH metabolism while significantly increasing the expression of molecules related to ferroptosis. The in vivo results showed that the GM-CQDs exhibited excellent antitumor activity and immune activation ability. Furthermore, because of their ideal biological safety, GM-CQDs are highly promising for application as drugs targeting GSH in the treatment of malignant tumors.

In-Brain Multiphoton Imaging of Vaterite Cargoes Loaded with Carbon Dots

Biocompatible fluorescent agents are key contributors to the theranostic paradigm by enabling real-time in vivo imaging. This study explores the optical properties of phenylenediamine carbon dots (CDs) and demonstrates their potential for fluorescence imaging in cells and brain blood vessels. The nonlinear absorption cross-section of the CDs was measured and achieved values near 50 Goeppert-Mayer (GM) units with efficient excitation in the 775-895 nm spectral range. Mesoporous vaterite nanoparticles were loaded with CDs to examine the possibility of a biocompatible imaging platform. Efficient one- and two-photon imaging of the CD-vaterite composites uptaken by diverse cells was demonstrated. For an in vivo scenario, CD-vaterite composites were injected into the bloodstream of a mouse, and their flow was monitored within the blood vessels of the brain through a cranial window. These results show the potential of the platform for high-brightness biocompatible imaging with the potential for both sensing and simultaneous drug delivery.

Formation and Fluorescent Mechanism of Multiple Color Emissive Carbon Dots from o-Phenylenediamine

Carbon dots (CDs) have received considerable attention in many application areas owing to their unique optical properties and potential applications; however, the fluorescent mechanism is an obstacle to their applications. Herein, three-color emissive CDs are prepared from single o-phenylenediamine (oPD) by regulating the ratio of ethanol and dimethylformamide (DMF). Fluorescent mechanism of these CDs is proposed as molecular state fluorescence. Reaction intermediates are identified using liquid chromatrography-mass spectroscopy (LC-MS) and 1H nuclear magnetic resonance (NMR) spectra. 1H-Benzo[d]imidazole (BI), 2,3-diaminophenazine (DAP), and 5,14-dihydroquinoxalino[2,3-b] phenazine (DHQP) are proposed to be the fluorophores of blue, green, and red emissive CDs by comparing their optical properties. As per the LC-MS and 1H-NMR analysis, DHQP with red emission tends to form from DAP and oPD in pure ethanol. By adding DMF, BI formation is enhanced and DHQP formation is suppressed. The prepared CDs exhibit green emission with DAP. When the DMF amount is >50%, BI formation is considerably promoted, resulting in DAP formation being suppressed. BI with blue emission then turns into the fluorophore of CDs. This result provides us an improved understanding of the fluorescent mechanism of oPD-based CDs, which guides us in designing the structure and optical properties of CDs.

Carbon dots as versatile nanomaterials in sensing and imaging: Efficiency and beyond

Carbon dots (CDs) have emerged as a versatile and promising carbon-based nanomaterial with exceptional optical properties, including tunable emission wavelengths, high quantum yield, and photostability. CDs are appropriate for various applications with many benefits, such as biocompatibility, low toxicity, and simplicity of surface modification. Thanks to their tunable optical properties and great sensitivity, CDs have been used in sensing as fluorescent probes for detecting pH, heavy metal ions, and other analytes. In addition, CDs have demonstrated potential as luminescence converters for white organic light-emitting diodes and light emitters in optoelectronic devices due to their superior optical qualities and exciton-independent emission. CDs have been used for drug administration and bioimaging in the biomedical field due to their biocompatibility, low cytotoxicity, and ease of functionalization. Additionally, due to their stability, efficient charge separation, and low recombination rate, CDs have shown interesting uses in energy systems, such as photocatalysis and energy conversion. This article highlights the growing possibilities and potential of CDs as adaptable nanomaterials in a variety of interdisciplinary areas related to sensing and imaging, at the same time addressing the major challenges involved in the current research and proposing scientific solutions to apply CDs in the development of a super smart society.

Tris-assisted one-step fabrication of functional carbon dots for specific folate receptor positive-expressed cancer cell imaging

Specific staining of cancer cells is momentous for cancer research. Nanoprobe with multivalent recognition is emerging as powerful tools for bioimaging, but the nonspecific cell uptake and complex functional modification procedures are still obstacles for specific detection and convenient synthesis. Carbon dots (CDs) with an intrinsic targeting ability, excellent optical properties and biocompatibility acquired from an efficient one-step fabrication procedure were urgently desired in specific cancer cells visualization. Herein, inspired by the interrelationships between interface and biomolecular mechanisms, we suggested that it was possible to construct CDs with the desired characteristics for folate receptor (FR) positive-expressed cancer cell imaging via rich hydroxyl groups Tris-assisted one-step hydrothermal treatment of folate acid (FA) and l-Arginine (L-Arg) precursors. The prepared small-sized F-CDs were equipped with abundant hydroxyl, pterin and negative charge surface, and possessed environmental friendliness, outstanding photostability and biocompatibility. Moreover, F-CDs had an intrinsic FR positive-expressed cancer cell targeting ability without any post-modification of the ligands. Rich hydroxyl groups play a vital role in endowing the optical properties and biological effects of F-CDs. F-CDs could be used as a promising candidate for FR-expressed cancer cell labeling and tracking. In addition, the caveolae-mediated endocytosis pathway of F-CDs was ascertained. More importantly, experimental results confirmed that the combination of physicochemical properties may provide an efficient strategy to overcome non-specific cell uptake interactions for cell labeling. Our strategy put forward a promising alternative to design fluorescent CDs for extensive chemical and biomedical applications.

A target-triggered strand displacement-assisted target recycling based on carbon dots-based fluorescent probe and MSNs@PDA nanoparticles for miRNA amplified detection and fluorescence imaging

A target-triggered strand displacement-assisted target recycling based on carbon dots-based fluorescent probe and mesoporous silica nanoparticles@polydopamine (MSNs@PDA) was established to detect miRNA. The surface of MSNs rich in mesopores was coated with a layer of PDA, which can adsorb and quench the fluorescence of single-stranded Fuel DNA with fluorescent carbon dots (CDs) modified at the end through fluorescence resonance energy transfer (FRET). After adding double-stranded DNA-gold nanoparticles (dsDNA-AuNPs) and target let-7a, it will trigger two toehold-mediated strand displacement reactions (TSDR), leading to the recovery of fluorescence and the recycling of target let-7a (excitation wavelength: 380 nm; emission wavelength: 458 nm). The recovery value of fluorescence is proportional to the logarithm of the target microRNA let-7a concentration, thus realizing the sensitivity amplification detection of disease markers. The MSNs@PDA@Fuel DNA-CDs/dsDNA-AuNPs nanoplatform based on the strategy of "on-off-on" and TSDR cyclic amplification may hold great potential as an effective and safe nanoprobe for accurate fluorescence imaging of diseases related to miRNA with low abundances.

The applications of carbon dots in oral health: A scoping review

OBJECTIVES

This scoping review aims to provide an overview of the research and potential applications of carbon dots (CDs) for oral health purposes.

DESIGN

Systematic literature searches were performed on PubMed and Web of Science databases (up to February 2023). Two co-authors selected the published works independently and extracted the data in accordance with the PRISMA statement. Studies with the application of CDs for oral health purposes were included.

RESULTS

Among 152 articles, 19 articles were finally selected. Eight studies investigated the anti-microbial effects of CDs against, for example, oral pathogens, eight studies explored the applicability of CDs in relation to oral cancer, and three studies investigated CDs in relation to cell differentiation and tissue regeneration in oral health. The studies showed the promising potential of CDs in oral health, particularly for inducing bacterial killing by increasing reactive oxygen species, killing oral cancer cells via photodynamic therapeutic effects, and inducing dental pulp and periodontal bone regeneration.

CONCLUSION

The findings show that CDs have the potential to be utilized in the future for various oral health purposes. Besides, these results underline the broad-spectrum applicability of CDs, crossing the borders of oral health.

Small Warriors of Nature: Novel Red Emissive Chlorophyllin Carbon Dots Harnessing Fenton-Fueled Ferroptosis for In Vitro and In Vivo Cancer Treatment

The appeal of carbon dots (CDs) has grown recently, due to their established biocompatibility, adjustable photoluminescence properties, and excellent water solubility. For the first time in the literature, copper chlorophyllin-based carbon dots (Chl-D CDs) are successfully synthesized. Chl-D CDs exhibit unique spectroscopic traits and are found to induce a Fenton-like reaction, augmenting photodynamic therapy (PDT) efficacies via ferroptotic and apoptotic pathways. To bolster the therapeutic impact of Chl-D CDs, a widely used cancer drug, temozolomide, is linked to their surface, yielding a synergistic effect with PDT and chemotherapy. Chl-D CDs' biocompatibility in immune cells and in vivo models showed great clinical potential.Proteomic analysis was conducted to understand Chl-D CDs' underlying cancer treatment mechanism. The study underscores the role of reactive oxygen species formation and pointed toward various oxidative stress modulators like aldolase A (ALDOA), aldolase C (ALDOC), aldehyde dehydrogenase 1B1 (ALDH1B1), transaldolase 1 (TALDO1), and transketolase (TKT), offering a deeper understanding of the Chl-D CDs' anticancer activity. Notably, the Chl-D CDs' capacity to trigger a Fenton-like reaction leads to enhanced PDT efficiencies through ferroptotic and apoptotic pathways. Hence, it is firmly believed that the inherent attributes of Chl-CDs can lead to a secure and efficient combined cancer therapy.

Carbon Dots: Synthesis, Characterizations, and Recent Advancements in Biomedical, Optoelectronics, Sensing, and Catalysis Applications

Carbon nanodots (CNDs), a fascinating carbon-based nanomaterial (typical size 2-10 nm) owing to their superior optical properties, high biocompatibility, and cell penetrability, have tremendous applications in different interdisciplinary fields. Here, in this Review, we first explore the superiority of CNDs over other nanomaterials in the biomedical, optoelectronics, analytical sensing, and photocatalysis domains. Beginning with synthesis, characterization, and purification techniques, we even address fundamental questions surrounding CNDs such as emission origin and excitation-dependent behavior. Then we explore recent advancements in their applications, focusing on biological/biomedical uses like specific organelle bioimaging, drug/gene delivery, biosensing, and photothermal therapy. In optoelectronics, we cover CND-based solar cells, perovskite solar cells, and their role in LEDs and WLEDs. Analytical sensing applications include the detection of metals, hazardous chemicals, and proteins. In catalysis, we examine roles in photocatalysis, CO2 reduction, water splitting, stereospecific synthesis, and pollutant degradation. With this Review, we intend to further spark interest in CNDs and CND-based composites by highlighting their many benefits across a wide range of applications.

Carbon quantum dots as immune modulatory therapy in a Sjögren's syndrome mouse model

OBJECTIVES

The objective of the study was to evaluate the therapeutic effects of carbon quantum dots (CQDs) in immunomodulation on non-obese diabetic (NOD) mice, as the model for Sjögren's syndrome (SS).

METHODS

Carbon quantum dots were generated from Setaria viridis via a hydrothermal process. Their toxic effects were tested by cell viability and blood chemistry analysis, meanwhile therapeutic effects were investigated in NOD mice in the aspects of saliva flow, histology, and immune cell distribution.

RESULTS

Carbon quantum dots, with rich surface chemistry and unique optical properties, showed non-cytotoxicity in vitro or no damage in vivo. Intravenously applied CQDs alleviated inflammation in the submandibular glands in NOD mice after 6-week treatments. The inflammatory area index and focus score were significantly decreased in CQD-treated mice. Besides, the levels of anti-SSA and anti-SSB were decreased in the presence of CQDs. The stimulated saliva flow rates and weight of submandibular glands were significantly increased in CQD-treated mice by reducing the apoptosis of cells. The CD3+ and CD4+ T cells distributed around the ducts of submandibular glands were significantly decreased, while the percentage of Foxp3+ cells was higher in CQD-treated mice than that in the control group.

CONCLUSIONS

Our findings suggest that CQDs may ameliorate the dysregulated immune processes in NOD mice.

pH-Dependent Non-Covalent Release of Chemotherapy from Carriers

Although Warburg discovered pH discrepancies between tumor and normal tissues nearly 100 years ago, developing therapies to take advantage of this concept was relatively slow for the first 70 years. During the last 30 years, there has been an exponential increase in the use of pH-dependent strategies for both low molecular weight drugs and nanoparticles. Two frequently discussed approaches are the chemotherapy's release from pH-sensitive covalent linkages of macromolecules or from pH-dependent disruption of charged polymeric nanoparticles. In contrast, pH-dependent non-covalent bonds between the chemotherapy agent and macromolecules have rarely been discussed, yet this underappreciated strategy has great potential. These non-covalent interactions are primarily ionic or hydrogen bonds with supporting roles from hydrophobic bonds. In addition to the facile coupling of the drug with the carrier, these non-covalent interactions may show marked pH dependence. Consistent with pH dependence, many of these drug-loaded carriers showed significant in vitro and, in some cases, striking in vivo activity. In this review, we will focus on pH-sensitive non-covalent bonds, highlighting the release of drugs from diverse carriers such as tetrahedron DNA structures, cyclodextrin, polymeric carriers, and carbon-based quantum particles.

Herbal Medicine-Inspired Carbon Quantum Dots with Antibiosis and Hemostasis Effects for Promoting Wound Healing

Bleeding and bacterial infections are crucial factors affecting wound healing. The usage of herbal medicine-derived materials holds great potential for promoting wound healing. However, the uncertain intrinsic effective ingredients and unclear mechanism of action remain great concerns. Herein, inspired by the herbal medicine Ligusticum wallichii, we reported the synthesis of tetramethylpyrazine-derived carbon quantum dots (TMP-CQDs) for promoting wound healing. Of note, the use of TMP as the precursor instead of L. wallichii ensured the repeatability and homogeneity of the obtained products. Furthermore, TMP-CQDs exhibited high antibacterial activity. Mechanically, TMP-CQDs inhibited the DNA repair, biosynthesis, and quorum sensing of the bacteria and induced intracellular reactive oxygen species (ROS). Moreover, TMP-CQDs could accelerate blood coagulation through activating factor VIII and promoting platelet aggregation. Effective wound healing was achieved by using TMP-CQDs in the Staphylococcus aureus-infected mouse skin wound model. This study sheds light on the development of herbal medicine-inspired materials as effective therapeutic drugs.

Modulating the Coordination Environment of Carbon-Dot-Supported Fe Single-Atom Nanozymes for Enhanced Tumor Therapy

Herein, carbon dot (CD)-supported Fe single-atom nanozymes with high content of pyrrolic N and ultrasmall size (ph-CDs-Fe SAzyme) are fabricated by a phenanthroline-mediated ligand-assisted strategy. Compared with phenanthroline-free nanozymes (CDs-Fe SAzyme), ph-CDs-Fe SAzyme exhibit higher peroxidase (POD)-like activity due to their structure similar to that of ferriporphyrin in natural POD. Aberration-corrected high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) analyses show that metal Fe is dispersed in ph-CDs-Fe SAzyme as single atoms. Steady-state kinetic studies show that the maximum velocity (Vmax ) and turnover number (kcat ) of H2 O2  homolytic cleavage catalyzed by ph-CDs-Fe SAzyme are 3.0 and 6.2 more than those of the reaction catalyzed by CDs-Fe SAzyme. Density functional theory (DFT) calculations show that the energy barrier of the reaction catalyzed by ph-CDs-Fe SAzyme is lower than that catalyzed by CDs-Fe SAzyme. Antitumor efficacy experiments show that ph-CDs-Fe SAzyme can efficiently inhibit the growth of tumor cells both in vitro and in vivo by synergistic chemodynamic and photothermal effects. Here a new paradigm is provided for the development of efficient antitumor therapeutic approaches based on SAzyme with POD-like activity.

Synthesis and Bioapplication of Emerging Nanomaterials of Hafnium

A significant amount of progress in nanotechnology has been made due to the development of engineered nanoparticles. The use of metallic nanoparticles for various biomedical applications has been extensively investigated. Biomedical research is highly focused on them because of their inert nature, nanoscale structure, and similar size to many biological molecules. The intrinsic characteristics of these particles, including electronic, optical, physicochemical, and surface plasmon resonance, that can be altered by altering their size, shape, environment, aspect ratio, ease of synthesis, and functionalization properties, have led to numerous biomedical applications. Targeted drug delivery, sensing, photothermal and photodynamic therapy, and imaging are some of these. The promising clinical results of NBTXR3, a high-Z radiosensitizing nanomaterial derived from hafnium, have demonstrated translational potential of this metal. This radiosensitization approach leverages the dependence of energy attenuation on atomic number to enhance energy-matter interactions conducive to radiation therapy. High-Z nanoparticle localization in tumor issue differentially increases the effect of ionizing radiation on cancer cells versus nearby healthy ones and mitigates adverse effects by reducing the overall radiation burden. This principle enables material multifunctionality as contrast agents in X-ray-based imaging. The physiochemical properties of hafnium (Z = 72) are particularly advantageous for these applications. A well-placed K-edge absorption energy and high mass attenuation coefficient compared to elements in human tissue across clinical energy ranges leads to significant attenuation. Chemical reactivity allows for variety in nanoparticle synthesis, composition, and functionalization. Nanoparticles such as hafnium oxide exhibit excellent biocompatibility due to physiochemical inertness prior to incidence with ionizing radiation. Additionally, the optical and electronic properties are applicable in biosensing, optical component coatings, and semiconductors. The wide interest has prompted extensive research in design and synthesis to facilitate property fine-tuning. This review summarizes synthetic methods for hafnium-based nanomaterials and applications in therapy, imaging, and biosensing with a mechanistic focus. A discussion and future perspective section highlights clinical progress and elaborates on current challenges. By focusing on factors impacting applicational effectiveness and examining limitations this review aims to support researchers and expedite clinical translation of future hafnium-based nanomedicine.

Carbon Dots: From Synthesis to Unraveling the Fluorescence Mechanism

Carbon dots (CDs) being a new type of carbon-based nanomaterial have attracted intensive interest from researchers owing to their excellent biophysical properties. CDs are a class of fluorescent carbon nanomaterials that have emerged as a promising alternative to traditional quantum dots and organic dyes in applications including bioimaging, sensing, and optoelectronics. CDs possess unique optical properties, such as tunable emission, facile synthesis, and low toxicity, making them attractive for many applications in biology, medicine, and environmental areas. The synthesis of CDs is achievable by a variety of methods, including bottom-up and top-down approaches, involving the use of different carbon sources and surface functionalization strategies. However, understanding the fluorescence mechanism of CDs remains a challenge. Various mechanistic models have been proposed to explain their origin of luminescence. This review summarizes the recent developments in the synthesis and functionalization of CDs and provides an overview of the current understanding of the fluorescence mechanism.

Manganese Amplifies Photoinduced ROS in Toluidine Blue Carbon Dots to Boost MRI Guided Chemo/Photodynamic Therapy

The contrast agents and tumor treatments currently used in clinical practice are far from satisfactory, due to the specificity of the tumor microenvironment (TME). Identification of diagnostic and therapeutic reagents with strong contrast and therapeutic effect remains a great challenge. Herein, a novel carbon dot nanozyme (Mn-CD) is synthesized for the first time using toluidine blue (TB) and manganese as raw materials. As expected, the enhanced magnetic resonance (MR) imaging capability of Mn-CDs is realized in response to the TME (acidity and glutathione), and r1 and r2 relaxation rates are enhanced by 224% and 249%, respectively. In addition, the photostability of Mn-CDs is also improved, and show an efficient singlet oxygen (1 O2 ) yield of 1.68. Moreover, Mn-CDs can also perform high-efficiency peroxidase (POD)-like activity and catalyze hydrogen peroxide to hydroxyl radicals, which is greatly improved under the light condition. The results both in vitro and in vivo demonstrate that the Mn-CDs are able to achieve real-time MR imaging of TME responsiveness through aggregation of the enhanced permeability and retention effect at tumor sites and facilitate light-enhanced chemodynamic and photodynamic combination therapies. This work opens a new perspective in terms of the role of carbon nanomaterials in integrated diagnosis and treatment of diseases.

Carbon dots and composite materials with excellent performances in cancer-targeted bioimaging and killing: a review

Carbon dots (CDs) are nanomaterials with excellent properties, including good biocompatibility, small size, ideal photoluminescence and surface modification, and are becoming one of the most attractive nanomaterials for the imaging, detection and treatment of tumors. Based on these advantages, CDs can be combined other materials to obtain composite particles with improved, even new, performance, mainly in photothermal and photodynamic therapies. This paper reviews the research progress of CDs and their composites in targeted tumor imaging, detection, diagnosis, drug delivery and tumor killing. It also discusses and proposes the challenges and perspectives of their future applications in these fields. This review provides ideas for future applications of novel CD-based materials in the diagnosis and treatment of cancer.

Green synthesis of fluorescent carbon nanodots from sage leaves for selective anticancer activity on 2D liver cancer cells and 3D multicellular tumor spheroids

Carbon nanodots, a family of carbon-based nanomaterials, have been synthesized through different methods from various resources, affecting the properties of the resulting product and their application. Herein, carbon nanodots (CNDs) were synthesized with a green and simple hydrothermal method from sage leaves at 200 °C for 6 hours. The obtained CNDs are well dispersed in water with a negative surface charge (ζ-potential = -11 mV) and an average particle size of 3.6 nm. The synthesized CNDs showed concentration-dependent anticancer activity toward liver cancer (Hep3B) cell lines and decreased the viability of the cancer cells to 23% at the highest used concentration (250 μg ml-1 of CNDs). More interestingly, the cytotoxicity of the CNDs was tested in normal liver cell lines (LX2) revealed that the CNDs at all tested concentrations didn't affect their viability including at the highest concentration showing a viability of 86.7%. The cellular uptake mechanisms of CNDs were investigated and they are thought to be through energy-dependent endocytosis and also through passive diffusion. The main mechanisms of endocytosis were lipid and caveolae-mediated endocytosis. In addition, the CNDs have hindered the formation of 3D spheroids from the Hep3B hepatocellular carcinoma cell line. Hence, it would be concluded that the synthesized CNDs from sage are more highly selective to liver cancer cells than normal ones. The CNDs' cancer-killing ability would be referred to as the production of reactive oxygen species.

Synthesis of pH-Sensitive Nitrogen-Doped Carbon Dots with Biological Imaging Function and Their Application in Cu2+ and Fe2+ Determination by Ratiometric Fluorescent Probes

pH-sensitive nitrogen-doped carbon dots (N-CDs) were synthesized using immature seeds of elm trees as a carbon source and ethylenediamine as a coreactant through a facile one-step hydrothermal method. The N-CDs were characterized using fluorescence spectroscopy, fluorescence lifetime, ultraviolet-visible absorption, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy, as well as transmission electron microscopy. The N-CDs displayed excellent fluorescence properties and responded to pH changes. The N-CDs exhibited low toxicity and good biocompatibility and had the potential to be used for the biological imaging of HeLa cells and mung bean sprouts. Utilizing the mechanism of fluorescence resonance energy transfer, ratiometric fluorescent probes were prepared by simple mixing of N-CDs and fluorexon in a Britton-Robinson buffer solution. The ratiometric fluorescent probe was used to detect Cu2+ and Fe2+. The linear equations were RCu = -0.0591[Q] + 3.505 (R2 = 0.992) and RFe = -0.0874[Q] + 3.61 (R2 = 0.999). The corresponding limits of detection were 0.5 and 0.31 μM, respectively. The good results had been obtained in the actual samples detection.

Development of biomass waste-based carbon quantum dots and their potential application as non-toxic bioimaging agents

Over recent years, carbon quantum dots (CQDs) have advanced significantly and gained substantial attention for their numerous benefits. These benefits include their simple preparation, cost-effectiveness, small size, biocompatibility, bright luminescence, and low cytotoxicity. As a result, they hold great potential for various fields, including bioimaging. A fascinating aspect of synthesizing CQDs is that it can be accomplished by using biomass waste as the precursor. Furthermore, the synthesis approach allows for control over the physicochemical characteristics. This paper unequivocally examines the production of CQDs from biomass waste and their indispensable application in bioimaging. The synthesis process involves a simple one-pot hydrothermal method that utilizes biomass waste as a carbon source, eliminating the need for expensive and toxic reagents. The resulting CQDs exhibit tunable fluorescence and excellent biocompatibility, making them suitable for bioimaging applications. The successful application of biomass-derived CQDs has been demonstrated through biological evaluation studies in various cell lines, including HeLa, Cardiomyocyte, and iPS, as well as in medaka fish eggs and larvae. Using biomass waste as a precursor for CQDs synthesis provides an environmentally friendly and sustainable alternative to traditional methods. The resulting CQDs have potential applications in various fields, including bioimaging.

In vitro and in vivo toxicity of carbon dots with different chemical compositions

Carbon dots (CDs) are easy-obtained nanoparticles with wide range of biological activity; however, their toxicity after prolonged exposure is poorly investigated. So, in vitro and in vivo toxicity of CDs with the surfaces enriched with hydroxylated hydrocarbon chains and methylene groups (CD_GE), carboxyl and phenol groups accompanied with nitrogen (CD_3011), trifluoromethyl (CDF19) or toluidine and aniline groups (CDN19) were aimed to be discovered. CDs' in vitro toxicity was assessed on A549 cells (real-time cell analysis of impedance, fluorescence microscopy) after 24 h of incubation, and we observed no changes in cell viability and morphology. CDs' in vivo toxicity was assessed on C57Bl6 mice after multiple dosages (5 mg/kg subcutaneously) for 14 days. Lethality (up to 50%) was observed in CDN19 and CD_3011 groups on different days of dosing, accompanied by toxicity signs in case of CD_3011. There were no changes in serum biochemical parameters except Urea (increased in CDF19 and CD_3011 groups), nor substantial kidney, liver, and spleen injuries. The most impactful for all organs were also CD_3011 and CDF19, causing renal tubule injury and liver blood supply violation. Thus, CDs with a surface enriched with oxygen- and nitrogen-containing functional groups might be toxic after multiple everyday dosing, without, however, significant damages of internal organs in survived animals.

Theranostics applications of quantum dots in regenerative medicine, cancer medicine, and infectious diseases

Quantum dots (QDs) have attracted attention for their application and commercialization in all industrial fields, including communications, displays, and solar cells, due to their excellent optical properties based on the quantum size effect. In recent years, the development of QDs that do not contain cadmium which is toxic to cells and living organisms, has progressed, and they have attracted considerable attention in the bio-imaging field for targeting molecules and cells. Furthermore, recently, the need for diagnostics and treatment at the single molecule and single cell level in the medical field has been increasing, and the application of QDs in the medical field is also accelerating. Therefore, this paper outlines the frontiers of diagnostic and therapeutic applications (theranostics) of QDs, especially in advanced medical fields such as regenerative medicine, oncology, and infectious diseases.

A Green Synthesis Route to Derive Carbon Quantum Dots for Bioimaging Cancer Cells

Carbon quantum dots (CQDs) are known for their biocompatibility and versatile applications in the biomedical sector. These CQDs retain high solubility, robust chemical inertness, facile modification, and good resistance to photobleaching, which makes them ideal for cell bioimaging. Many fabrication processes produce CQDs, but most require expensive equipment, toxic chemicals, and a long processing time. This study developed a facile and rapid toasting method to prepare CQDs using various slices of bread as precursors without any additional chemicals. This fast and cost-effective toasting method could produce CQDs within 2 h, compared with the 10 h process in the commonly used hydrothermal method. The CQDs derived from the toasting method could be used to bioimage two types of colon cancer cells, namely, CT-26 and HT-29, derived from mice and humans, respectively. Significantly, these CQDs from the rapid toasting method produced equally bright images as CQDs derived from the hydrothermal method.

Recent Developments in PET and SPECT Radiotracers as Radiopharmaceuticals for Hypoxia Tumors

Hypoxia, a deficiency in the levels of oxygen, is a common feature of most solid tumors and induces many characteristics of cancer. Hypoxia is associated with metastases and strong resistance to radio- and chemotherapy, and can decrease the accuracy of cancer prognosis. Non-invasive imaging methods such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) using hypoxia-targeting radiopharmaceuticals have been used for the detection and therapy of tumor hypoxia. Nitroimidazoles are bioreducible moieties that can be selectively reduced under hypoxic conditions covalently bind to intracellular macromolecules, and are trapped within hypoxic cells and tissues. Recently, there has been a strong motivation to develop PET and SPECT radiotracers as radiopharmaceuticals containing nitroimidazole moieties for the visualization and treatment of hypoxic tumors. In this review, we summarize the development of some novel PET and SPECT radiotracers as radiopharmaceuticals containing nitroimidazoles, as well as their physicochemical properties, in vitro cellular uptake values, in vivo biodistribution, and PET/SPECT imaging results.

Delivery of Chemotherapy Agents and Nucleic Acids with pH-Dependent Nanoparticles

With less than one percent of systemically injected nanoparticles accumulating in tumors, several novel approaches have been spurred to direct and release the therapy in or near tumors. One such approach depends on the acidic pH of the extracellular matrix and endosomes of the tumor. With an average pH of 6.8, the extracellular tumor matrix provides a gradient for pH-responsive particles to accumulate, enabling greater specificity. Upon uptake by tumor cells, nanoparticles are further exposed to lower pHs, reaching a pH of 5 in late endosomes. Based on these two acidic environments in the tumor, various pH-dependent targeting strategies have been employed to release chemotherapy or the combination of chemotherapy and nucleic acids from macromolecules such as the keratin protein or polymeric nanoparticles. We will review these release strategies, including pH-sensitive linkages between the carrier and hydrophobic chemotherapy agent, the protonation and disruption of polymeric nanoparticles, an amalgam of these first two approaches, and the release of polymers shielding drug-loaded nanoparticles. While several pH-sensitive strategies have demonstrated marked antitumor efficacy in preclinical trials, many studies are early in their development with several obstacles that may limit their clinical use.

Carbon Dots: Opportunities and Challenges in Cancer Therapy

Recently, carbon dots (CDs) have been actively studied and reported for their various properties. In particular, the specific characteristics of carbon dots have been considered as a possible technique for cancer diagnosis and therapy. This is also a cutting-edge technology that offers fresh ideas for treating various disorders. Though carbon dots are still in their infancy and have not yet shown their value to society, their discovery has already resulted in some noteworthy advancements. The application of CDs indicates conversion in natural imaging. Photography using CDs has demonstrated extraordinary appropriateness in bio-imaging, the discovery of novel drugs, the delivery of targeted genes, bio-sensing, photodynamic therapy, and diagnosis. This review seeks to provide a comprehensive understanding of CDs, including their benefits, characteristics, applications, and mode of action. In this overview, many CD design strategies will be highlighted. In addition, we will discuss numerous studies on cytotoxic testing to demonstrate the safety of CDs. The current study will address the production method, mechanism, ongoing research, and application of CDs in cancer diagnosis and therapy.

Carbon Dots: Classically Defined versus Organic Hybrids on Shared Properties, Divergences, and Myths

Carbon dots are defined as small carbon nanoparticles with effective surface passivation via organic functionalization. The definition is literally a description of what carbon dots are originally found for the functionalized carbon nanoparticles displaying bright and colorful fluorescence emissions, mirroring those from similarly functionalized defects in carbon nanotubes. In literature more popular than classical carbon dots are the diverse variety of dot samples from "one-pot" carbonization of organic precursors. On the two different kinds of samples from the different synthetic approaches, namely, the classical carbon dots versus those from the carbonization method, highlighted in this article are their shared properties and apparent divergences, including also explorations of the relevant sample structural and mechanistic origins for the shared properties and divergences. Echoing the growing evidence and concerns in the carbon dots research community on the major presence of organic molecular dyes/chromophores in carbonization produced dot samples, demonstrated and discussed in this article are some representative cases of dominating spectroscopic interferences due to the organic dye contamination that have led to unfound claims and erroneous conclusions. Mitigation strategies to address the contamination issues, including especially the use of more vigorous processing conditions in the carbonization synthesis, are proposed and justified.

Water Soluble PMPC-Derived Bright Fluorescent Nitrogen/Phosphorous-Doped Carbon Dots for Fluorescent Ink (Anti-Counterfeiting) and Cellular Multicolor Imaging

Here, a simple one-step hydrothermal-assisted carbonization process was adopted for the preparation of nitrogen/phosphorous-doped carbon dots from a water-soluble polymer, poly 2-(methacryloyloxy)ethyl phosphorylcholine (PMPC). By the free-radical polymerization method, PMPC was synthesized using 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and 4,4′-azobis (4-cyanovaleric acid). The water-soluble polymers, PMPC, that have nitrogen/phosphorus moieties are used to prepare carbon dots (P-CDs). The resulting P-CDs were thoroughly characterized by various analytical techniques such as field emission-scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy (EDS), high-resolution transmittance electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible (UV-vis) spectroscopy and fluorescence spectroscopy to determine their structural and optical properties. The synthesized P-CDs displayed bright/durable fluorescence, were stable for long periods, and confirmed the enrichment of functionalities including oxygen, phosphorus, and nitrogen heteroatoms in the carbon matrix. Since the synthesized P-CDs showed bright fluorescence with excellent photostability, excitation-dependent fluorescence emission, and excellent quantum yield (23%), it has been explored as a fluorescent (security) ink for drawing and writing (anti-counterfeiting). Further, cytotoxicity study results advised for biocompatibility and thus were used for cellular multicolor imaging in nematodes. This work not only demonstrated the preparation of CDs from polymers that can be used as advanced fluorescence ink, a bioimaging agent for anti-counterfeiting, and cellular multicolor imaging candidate, but additionally prominently opened a new perspective on the bulk preparation of CDs simply and efficiently for various applications.

Review on Carbon Dot-Based Fluorescent Detection of Biothiols

Biothiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play a vital role in gene expression, maintaining redox homeostasis, reducing damages caused by free radicals/toxins, etc. Likewise, abnormal levels of biothiols can lead to severe diseases, such as Alzheimer's disease (AD), neurotoxicity, hair depigmentation, liver/skin damage, etc. To quantify the biothiols in a biological system, numerous low-toxic probes, such as fluorescent quantum dots, emissive organic probes, composited nanomaterials, etc., have been reported with real-time applications. Among these fluorescent probes, carbon-dots (CDs) have become attractive for biothiols quantification because of advantages of easy synthesis, nano-size, crystalline properties, low-toxicity, and real-time applicability. A CDs-based biothiols assay can be achieved by fluorescent "Turn-On" and "Turn-Off" responses via direct binding, metal complex-mediated detection, composite enhanced interaction, reaction-based reports, and so forth. To date, the availability of a review focused on fluorescent CDs-based biothiols detection with information on recent trends, mechanistic aspects, linear ranges, LODs, and real applications is lacking, which allows us to deliver this comprehensive review. This review delivers valuable information on reported carbon-dots-based biothiols assays, the underlying mechanism, their applications, probe/CDs selection, sensory requirement, merits, limitations, and future scopes.

Multi-applications of carbon dots and polydopamine-coated carbon dots for Fe3+ detection, bioimaging, dopamine assay and photothermal therapy

Carbon dots (CDs) or CDs/polymer composites have been applied in numerous fields. Here, novel CDs were synthesized by carbonization of egg yolk, and characterized by TEM, FTIR, XPS and photoluminescence spectra. The CDs were found to be approximate sphere in shape with an average size of 4.46 ± 1.17 nm, and emitted bright blue photoluminescence under UV irradiation. The photoluminescence of CDs was found selectively quenched by Fe³⁺ in a linear manner in the range of 0.05-0.45 mM, meaning they could be applied for Fe³⁺ detection in solution. Moreover, the CDs could be uptaken by HepG2 cells to exhibit bright blue photoluminescence. The intensity could reflect the level of intracellular Fe³⁺, indicating they could be further used for cell imaging and intracellular Fe³⁺ monitoring. Next, dopamine was polymerized on the surface of CDs to obtain the polydopamine (PDA)-coated CDs (CDs@PDA). We found PDA coating could quench the photoluminescence of CDs via inner filter effect, and the degree of quenching was linearly related to the logarithm of DA concentration (Log C_DA). Also, the selectivity experiment indicated the method had a high selectivity for DA over a number of possible interfering species. This indicated the CDs in combination with Tris buffer could be potentially applied as the assay kit of dopamine. At last, the CDs@PDA exhibited excellent photothermal conversion capability, and they could efficiently kill HepG2 cells under NIR laser irradiation. Overall, the CDs and CDs@PDA in this work exhibited many excellent advantages, and could be potentially used for multi-applications, such as Fe³⁺ sensor in solution and cellular, cell imaging, dopamine assay kit, as well as photothermal agents for cancer therapy.

Recent advances in carbon dots: synthesis and applications in bone tissue engineering

Bone tissue engineering (BTE), based on the perfect combination of seed cells, scaffold materials and growth factors, has shown unparalleled potential in the treatment of bone defects and related diseases. As the site of cell attachment, proliferation and differentiation, scaffolds composed of biomaterials play a crucial role in BTE. Over the past years, carbon dots (CDs), a new type of carbon-based nanomaterial, have attracted extensive research attention due to their good biocompatibility, unique optical properties, and abundant functional groups. This paper reviews recent research progress in the use of CDs in the field of BTE. Firstly, different preparation methods of CDs are summarized. Then, the properties and categories of CDs applied in BTE are described in detail. Subsequently, the applications of CDs in BTE, including osteogenesis, fluorescence tracing, phototherapy and antibacterial activity, are presented. Finally, the challenges and future perspectives of CDs in BTE are briefly discussed to give a comprehensive picture of CDs. This review provides a theoretical basis and advanced design strategies for the application of CDs in BTE.

Functional Carbon Quantum Dots for Ocular Imaging and Therapeutic Applications

Carbon quantum dots (CDs) are a class of emerging carbonaceous nanomaterials that have received considerable attention due to their excellent fluorescent properties, extremely small size, ability to penetrate cells and tissues, ease of synthesis, surface modification, low cytotoxicity, and superior water dispersion. In light of these properties, CDs are extensively investigated as candidates for bioimaging probes, efficient drug carriers, and disease diagnostics. Functionalized CDs represent a promising therapeutic candidate for ocular diseases. Here, this work reviews the potential use of functionalized CDs in the diagnosis and treatment of eye-related diseases, including the treatment of macular and anterior segment diseases, as well as targeting Aβ amyloids in the retina.

Targeted Delivery Strategies of Herbal-Based Nanogels: Advancements and Applications

The objective of this review is to thoroughly investigate herbal nano gels as a promising drug delivery approach for the management of various chronic and acute disorders. Herbal nano gels are a novel and promising drug delivery technique, offering special benefits for better therapeutic efficacy. This review offers a comprehensive analysis of the herbal nano gels with a particular emphasis on their evaluation concerning conventional dosage forms, polymer selection criteria, drug release mechanisms, and applications. The comparison study demonstrates that herbal nano gels have different benefits over conventional dose forms. In the areas of oral administration for improved bioavailability and targeted delivery to the gastrointestinal tract, topical drug delivery for dermatological conditions, and targeted delivery strategies for the site-specific treatment of cancer, inflammatory diseases, and infections, they demonstrate encouraging results in transdermal drug delivery for systemic absorption. A promising platform for improved medication delivery and therapeutic effectiveness is provided by herbal nanogels. Understanding drug release mechanisms further contributes to the controlled and sustained delivery of herbal therapeutics. Some of the patents are discussed and the comparative analysis showcases their superiority over conventional dosage forms, and the polymer selection criteria ensure the design of efficient and optimized formulations. Herbal-based nano gels have become a potential approach for improving drug administration. They provide several advantages such as better stability, targeted delivery, and controlled release of therapeutic components. Herbal nano gels are a promising therapeutic approach with the ability to combat a wide range of conditions like cancer, wound healing and also improve patient compliance.

The Application of Carbon Nanomaterials in Sensing, Imaging, Drug Delivery and Therapy for Gynecologic Cancers: An Overview

Gynecologic cancers are one of the main health concerns of women throughout the world, and the early diagnosis and effective therapy of gynecologic cancers will be particularly important for the survival of female patients. As a current hotspot, carbon nanomaterials have attracted tremendous interest in tumor theranostics, and their application in gynecologic cancers has also been developed rapidly with great achievements in recent years. This Overview Article summarizes the latest progress in the application of diverse carbon nanomaterials (e.g., graphenes, carbon nanotubes, mesoporous carbon, carbon dots, etc.) and their derivatives in the sensing, imaging, drug delivery, and therapy of different gynecologic cancers. Important research contributions are highlighted in terms of the relationships among the fabrication strategies, architectural features, and action mechanisms for the diagnosis and therapy of gynecologic cancers. The current challenges and future strategies are discussed from the viewpoint of the real clinical application of carbon-based nanomedicines in gynecologic cancers. It is anticipated that this review will attract more attention toward the development and application of carbon nanomaterials for the theranostics of gynecologic cancers.