Carbon Dots in Bioimaging, Biosensing and Therapeutics: A Comprehensive Review

Recent advances in fluorescent nanomaterials designed for biomarker detection and imaging

The highly sensitive detection and imaging of biomarkers are critical for early diagnosis, treatment, and prognosis monitoring. The unique size and structure of fluorescent nanomaterials provide key benefits such as excellent photostability, high fluorescence quantum yield, and tunable excitation and emission wavelengths. These properties have led to the widespread application of nanomaterials in fluorescent biomarkers detection and imaging. In this review, we began by introducing the composition of fluorescent probes and discussing the underlying sensing mechanisms. We then summarized recent advances in the use of fluorescent nanomaterials such as quantum dots (QDs), metal nanoclusters (MNCs), carbon dots (CDs), and metal-organic frameworks (MOFs) for biomarker detection and imaging. Additionally, we highlighted the applications of fluorescent nanomaterials in the detection and imaging of small molecules, biomacromolecules, and various biomarkers, including metal ions, bacteria, and circulating tumor cells (CTCs). The challenges and future prospects of fluorescent nanomaterials in biomarker detection and imaging were also discussed. We anticipate that fluorescent nanomaterials will have profound implications for clinical biomarker detection and imaging, with considerable application in both academic research and industrial applications.

Isolating the effects of photon reabsorption in the photoluminescence spectrum of carbon dots

Carbon dots (CDs) are highly emissive nanoparticles that exhibit broad photoluminescence (PL) across a wide frequency range in solutions and thin films. However, at high concentrations, CDs suffer from PL quenching, traditionally attributed to aggregation effects, which induce PL spectral shifts and changes in PL lifetimes. In this study, we demonstrate that photon reabsorption is a pivotal, often overlooked mechanism contributing to emission quenching, without any change in lifetimes. An excitation depth-dependent PL measurement was performed to separate out the effects of reabsorption in the emission spectrum of CDs. Photon reabsorption arises from the wavelength-dependent absorption of emitted photons as they propagate through the CD solution, leading to a redshift in the emission peak and a reduction in PL intensity. We corrected the apparent spectral shift by accounting for the absorption of the CD sample in the region where the emission and absorption spectra overlap. Furthermore, time-resolved PL decay measurements ruled out aggregation effects, confirming that reabsorption is the primary mechanism causing PL quenching in our sample. These findings highlight the necessity of addressing reabsorption effects to accurately measure the PL spectra for emissive species, such as CDs, which exhibit broad absorption and emission with significant spectral overlap.

Biomass-Derived Carbon Dots: Sustainable Solutions for Advanced Energy Storage Applications

The growing energy demand has underscored the importance of sustainable energy storage devices. Biomass-derived carbon dots (B-Cdots) have gained significant attention for their potential to address this challenge. Utilizing greener routes for the large-scale synthesis of B-Cdots is not only eco-friendly and cost-effective but also promotes sustainability. This review highlights various synthesis methods for B-Cdots, including microwave-assisted, hydrothermal, and pyrolysis-based carbonization processes. It also explores their electrochemical applications in supercapacitors, lithium-ion batteries, sodium-ion batteries, and other energy storage devices, along with recent advancements in the field. The fabrication of electrodes using B-Cdots offers several advantages, such as tunable chemical and physical properties, porous structures, efficient heteroatom doping, and excellent electrical conductivity. These attributes make B-Cdots highly attractive for energy storage applications. Overall, this review emphasizes the critical role of sustainable materials in shaping the future of energy storage technologies.

Glucose oxidase/copper‑carbon dots/hyaluronic acid self-assembly for self-supply hydrogen peroxide in a double-enzyme cascade to enhance anti-tumor therapy

Although chemodynamic therapy (CDT) has proven to be a promising anti-tumor strategy, its efficacy is limited by the insufficient supply of H2O2 in tumor tissues. To solve the problem of insufficient H2O2, in this paper, a novel double-enzyme cascade nanoreactor hyaluronic-cinnamaldehyde Schiff base@glucose oxidase (GOx)/copper doped carbon dot (abbreviation HCFCTG), which constructed by co-assembly of copper doped carbon dot (CuFACDs-TPP), glucose oxidase (GOx) and hyaluronic-cinnamaldehyde Schiff base (HA-CA) was designed for the first time. The HCFCTG released GOx and CuFACDs-TPP under pH stimulation. GOx continues to supply H2O2 to CDT by consuming glucose, while cutting off the supply of nutrients to starve cancer cells to death (ST), ultimately amplifying the therapeutic effect of CDT. CuFACDs-TPP precisely anchors mitochondria to destroy mitochondria and induce apoptosis, while copper ions consume glutathione to amplify reactive oxygen species (ROS) levels. Self‑oxygenation of HCFCTG by Fenton-like reaction down-regulates hypoxia-inducible factor (HIF-1α) to consolidate CDT effect. The 808 nm laser activates the photothermal effect enhances CDT. In vitro and in vivo experiments proved that HCFCTG has good biocompatibility and excellent CDT effect. HCFCTG overcomes the problem of insufficient H2O2 in the CDT process.

Eco-Friendly Biomass-Based Carbon Dots, Carbon Nanotubes, Graphene, and Their Derivatives for Enhanced Oil Recovery: A New Horizon for Petroleum Industry

Oil extraction from reservoirs has never been easy, particularly when easily accessible oil sources run out. Enhanced oil recovery (EOR) is a dynamic area of petroleum engineering that seeks to maximize the quantity of crude oil that can be retrieved from an oil field. Researchers and oil producers have emphasized assessing tertiary-stage recovery approaches, such as chemical EOR (CEOR), due to the problems posed by the diverse carbonate rocks. Polymers and surfactants used in CEOR procedures have the potential to harm formation and contaminate the environment. The environmentally beneficial "green enhanced oil recovery" (GEOR) technique includes infusing green fluids to raise tertiary oil output and boost macroscopic and microscopic sweep efficiency, ensuring sustainable practices while minimizing environmental concerns. Utilizing eco-friendly carbon nanomaterials such as biomass-based carbon dots (CDs), carbon nanotubes (CNTs), graphene, and their derivatives for EOR and reservoir monitoring applications represents a promising frontier in the petroleum industry. These particles are pricey and do not extend to GEOR but have been successfully tested in EOR. This innovative approach capitalizes on the unique properties of these nanomaterials to improve the efficiency and sustainability of oil extraction processes. This review aims to explore biomass-derived carbon nanoparticles and investigate their possible functions in GEOR. Furthermore, the use of carbon particles in the GEOR approach is still poorly understood; thus, there needs to be a lot of credentials. The effectiveness, sustainability, and environmental responsibility of petroleum production operations can be enhanced by incorporating carbon nanomaterials from biomass into enhanced oil recovery systems. An environmentally friendly and more resilient energy future may be possible if research and development in this area are allowed to continue. This might completely change how oil resources are found and used.

Nanoengineering Carbon Dot-Polymer Brush Interfaces for Adaptive Optical Materials

We present a versatile platform for fabricating two-photon excitable carbon dot-based nanocomposite thin films by harnessing the structural versatility of polymer brushes in combination with electron-beam lithography (EBL). This approach enables the precise spatial organization of carbon dots (CDs) at the nanoscale, facilitating dynamic modulation of their photoluminescent properties in response to environmental stimuli. Three model systems were examined, incorporating pH- and thermally responsive polymers, functionalized through covalent and dynamic covalent bonding strategies. By leveraging the spatial control afforded by nanostructured polymer brushes, we achieved precise tuning of optical properties while mitigating aggregation-induced quenching, a longstanding challenge in solid-state CD applications. In addition to the advances in controlling optical properties, this work highlights the potential of polymer brush systems to function as optically active, reprogrammable surfaces. The resulting nanoscale-engineered materials exhibit highly responsive, reconfigurable photonic behavior, offering a scalable pathway for integrating advanced optical interfaces into microchip technologies, biosensing platforms, and multiplexed diagnostic systems. The fusion of polymer brushes, carbon dots, and advanced lithographic techniques marks a substantial advancement in the development of functional materials with nanoscale precision and stimuli-responsive properties.

Biogenic fluorescent carbon dot-decorated mesoporous organosilica nanoparticles for enhanced bioimaging and chemotherapy

Hybrid materials possess the unique properties of their individual components, enabling their use in multiple synergistic applications. In this study, we synthesized biogenic fluorescent carbon dots (CDs) decorated with biodegradable periodic mesoporous organosilica nanoparticles (BPMO), creating BPMO@CDs. The CDs, approximately 9.8 nm in diameter, were derived from Musa paradisiaca cv. Awak juice using a rapid microwave method, exhibiting a spherical shape and green and red luminescence. The resulting BPMO@CDs are spherical, around 100 nm in size, and maintain high pore volume and surface area. The elemental chemical state in the BPMO@CDs remains consistent with that of pure BPMO. Our findings demonstrate that BPMO@CDs achieve efficient cellular uptake rates of 46.74% in MCF7 cells and 17.07% in L929 cells, with preserved fluorescence within the cells. The optical properties of the CDs are retained in the BPMO@CDs, allowing for detection upon cellular uptake. Additionally, when loaded with anticancer drugs, the BPMO@CDs significantly enhance the cytotoxicity against MCF7 breast cancer cells, highlighting their potential for synergistic bioimaging and chemotherapy applications.

Effect of temperature on the carbonization process of cationic carbon dots: a physicochemical and in vitro study

This work highlights the critical role of synthesis conditions in tuning the properties of carbon dots (CDs) for optimized performance in biomedical applications, offering valuable insights into the design of these carbon nanomaterials. Although various synthesis methods and carbon sources have been explored for CD production, few studies have investigated how synthesis temperature modulates and optimizes their physicochemical attributes. In this study, cationic CDs derived from poly(ethylene imine) (PEI) and chitosan (CS) were synthesized using a microwave-assisted hydrothermal method at different temperatures to explore this aspect. It was found that higher carbonization temperatures during the hydrothermal process resulted in smaller, more photoluminescent CDs. This increase in temperature significantly enhanced the biological interactions of the CDs, demonstrating notable biocompatibility. In contrast, the lowest hydrothermal temperature enhanced cytotoxic effects against the Gram-positive pathogen Staphylococcus aureus under light exposure. Furthermore, gastric cancer (AGS), colon cancer (HT-29), cervical cancer (HeLa), prostate cancer (PC-3), and breast epithelial (MCF-10) cell lines showed cytotoxicity that was dependent on the CDs synthesized at different temperatures.

Dead Cell Discrimination with Red Emissive Carbon Quantum Dots from the Medicinal and Edible Herb Echinophora tenuifolia

Accurately determining the viability of cells is crucial for in vitro cell research. Fluorescence-based live/dead cell staining is a highly desirable method to assess cell viability and survival in in vitro studies. We describe a green synthesis method to create red-emissive CQDs from the medicinal and edible herb Echinophora tenuifolia using microwave irradiation. We observed that the biocompatibility and photostability of the CQDs are superior. The antioxidant capacity of the CQDs and the plant extract were also investigated using different chemical methods (DPPH, ABTS, CUPRAC, FRAP, PBD, and MCA). The antioxidant capacity of the CQDs was similar to that of the extract of E. tenuifolia. Cytotoxicity studies indicate that while the CQDs are not toxic to L929, they exhibit significant toxicity towards HepG2 cells. The CQDs exhibited a strong negative zeta potential (-44.0 mV), which contributed to their selective interaction with dead cells while being repelled by viable cells with intact membrane potentials. The optimal concentration for effective, non-toxic imaging was determined to be 25 µg/mL, as lower concentrations did not produce detectable fluorescence. Differential staining experiments confirmed that CQDs selectively stained dead cells, with red fluorescence observed under the Texas Red filter. Moreover, CQDs exhibited favorable fluorescence intensity and stability, which may offer advantages for long-term and reliable bioimaging applications. In vitro studies on HepG2 and L929 cell lines revealed that the red-emissive CQDs from E. tenuifolia can be potentially used in bioimaging.

Xylooligosaccharides, monosaccharides, and pH-sensitive carbon dots production from Toona sinensis branches using organic acid hydrolysis and hydrothermal treatment

The present study focused on exploring the effectiveness of delignification of the lignocellulosic biomass and pH-controlled organic acid hydrolysis in the cascade utilization of Toona sinensis branches (TB) for the production of xylooligosaccharides (XOS), monosaccharides and carbon dots (CDs). The hydrolysis of delignified TB with propionic acid (PA) resulted in a high XOS yield of 48.1 % at pH 3.0, 170 °C for 60 min. The PA hydrolyzates upon hydrolysis with xylanase yielded 61.2 % XOS. The solid residue from XOS production was subjected to cellulase hydrolysis, resulting in a glucose yield of 87.8 %. Furthermore, CDs were synthesized through a green hydrothermal method using the solid residue from cellulase hydrolysis as a precursor. These CDs exhibited excitation-independent and pH-dependent fluorescence properties. This study demonstrated the integrated utilization of TB for efficient production of XOS, monosaccharides, and pH-sensitive CDs.

Dual functionality of malt bagasse-based carbonaceous material for obtaining carbon dots and adsorbent: removing and detecting tetracycline

Malt bagasse was used as a precursor to produce a carbonaceous material (CM) with dual functionality: adsorbing tetracycline (TC) from aqueous solutions and serving as raw material for carbon dots (CDs) capable of detecting TC qualitatively. A 23 experimental design evaluated the effects of temperature (200-500 °C), heating rate (2-8 °C/min), and carbonization time (30-180 min) on the adsorption capacity of CM and the quantum yield of CDs. Adsorption capacity was evaluated in an aqueous solution of tetracycline (30 mg/L) and 1 g/L of CM. The use of CD as a qualitative sensor was studied in TC solutions (30 μM), based on the comparison of the areas under the fluorescence spectrum between samples with and without the antibiotic. Temperature was the most significant factor, followed by carbonization time. The material obtained at 350 °C for 30 min with a heating rate of 5 °C/min had a TC adsorption capacity of 7.0 mg/g ± 0.6 mg/g and a quantum yield ranging from 4.90% to 7.62%. These samples also achieved TC detection above 58%. This material had a heterogeneous mesoporous structure, with low graphitization and a greater presence of defects and/or disorder. Additionally, the CD particles exhibit an almost spherical morphology and good dispersion, with an average diameter ranging between 1 nm and 3 nm. These results demonstrate the innovative use of malt bagasse as a precursor for multi-functional carbonaceous materials. The results highlight the potential of lignocellulosic biomass as a versatile and sustainable resource for environmental applications, paving the way for future advances in integrated pollutant management strategies.

"Self-Capped" Carbon Dots with Excellent Anti-Bacteria Effect and an Extremely Low Cytotoxicity Applied for Hand Sanitizer

The increasing challenge of antibiotic resistance necessitates the development of novel antibacterial strategies. In this study, a novel kind of self-capped carbon dots is synthesized from methylene blue (MB) and cetyltrimethylammonium chloride (CTAC), and named as MC-CDs that are specifically designed for enhanced photodynamic antibacterial activity. Under 660 nm laser irradiation, MC-CDs demonstrate high inactivation rates of Escherichia coli (96.83%) and Staphylococcus aureus (94.44%) at 14 and 18 µg mL-1 effectively, disrupting bacterial cell membranes. The incorporation of zinc cations (Zn2+) doping further enhances the antibacterial potential of MC-CDs, enabling substantial efficacy even in the absence of light due to improved electrostatic interactions with bacterial membranes. In comparison to commercial agents such as salicylic acid, p-chloro-m-xylenol, and triclosan, Zn@MC-CDs exhibit superior antibacterial performance. When formulated into a hand sanitizer, Zn@MC-CDs maintained over 90% efficacy, displaying excellent stability and extremely low cytotoxicity, highlighting their potential for safe and effective use in personal hygiene products. This study introduces self-capped carbon dot as a promising antibacterial agent, addressing a critical need for advanced and reliable solutions in infection control.

Mulberry Leaves-Derived Carbon Dots for Photodynamic Treatment of Methicillin-Resistant Staphylococcus aureus-Infected Wounds via Metabolic Perturbation

Antibiotic-resistant pathogens pose a significant global public health challenge, particularly in refractory infections associated with biofilms. The urgent development of innovative, safe, and therapeutically adaptive strategies to combat these resistant biofilms is essential. We present a novel, precise, and controllable photodynamic antibacterial carbon dot (B-M-CD) inspired by the natural antibacterial properties of the mulberry leaf and the bacterial targeting function of boric acid. This photocatalytic antibacterial agent exhibits good biocompatibility and utilizes its inherent antibacterial activities, along with photoactivated oxidase-mimicking activity, to generate reactive oxygen species for the eradication of methicillin-resistant Staphylococcus aureus (MRSA). By leveraging the reversible covalent binding between boronic acid groups and cis-diol groups on bacterial surfaces, we further enhance the targeted antibacterial activity. B-M-CDs effectively penetrate extracellular polymeric substances and demonstrate a precise photodynamic antibacterial effect, allowing for localized delivery aimed at biofilm inhibition and destruction. Metabolomic analyses reveal that B-M-CDs disrupt amino acid metabolism, protein synthesis, electron transport chain, and energy metabolism in MRSA. In vivo experiments confirm that this photocatalyst effectively treats MRSA-induced wounds with an efficacy comparable to that of vancomycin while also exhibiting high biocompatibility. This study represents the first development of a precise, photoactivated, controllable, and targeted carbon-based antibacterial nanozyme derived from the traditional Chinese herb, mulberry leaf, providing a novel strategy for designing intelligent antibacterial nanoagents and underscoring their potential as candidate therapeutics for conditions analogous to MRSA infections.

Applications of Green Carbon Dots in Personalized Diagnostics for Precision Medicine

Green carbon dots (GCDs) have emerged as a revolutionary tool in precision medicine, offering transformative capabilities for personalized diagnostics and therapeutic strategies. Their unique optical and biocompatible properties make them ideal for non-invasive imaging, real-time monitoring, and integration with genomics, proteomics, and bioinformatics, enabling accurate diagnosis and tailored treatments based on patients' genetic and molecular profiles. This study explores the potential of GCDs in advancing individualized patient care by examining their applications in precision medicine. It evaluates their utility in non-invasive diagnostic imaging, targeted therapy delivery, and the formulation of personalized treatment plans, emphasizing their interaction with advanced genomic, proteomic, and bioinformatics platforms. GCDs demonstrated exceptional versatility in enabling precise diagnostics and delivering targeted therapies. Their integration with cutting-edge technologies showed significant promise in crafting personalized treatment strategies, enhancing their functionality and effectiveness in real-time monitoring and patient-specific applications. The findings underscore the pivotal role of GCDs in reshaping healthcare by advancing precision medicine and improving patient outcomes. The ongoing development and integration of GCDs with emerging technologies promise to further enhance their capabilities, paving the way for more effective, individualized medical care.

Exploring Green Practices: a Review of Carbon Dot-Based Sustainable Sensing Approaches

The increasing demand for sustainable and eco-friendly technologies has driven significant interest in carbon dots (CDs) due to their unique optical properties, low toxicity, and versatile applications in sensing. The aim of this review is to provide a comprehensive analysis of the current advancements in CD-based sensing approaches, with a focus on their environmental sustainability based on greenness evaluation tools. We begin by discussing the principles and methodologies of greenness evaluation, including various assessment tools and metrics used to measure the environmental impact of CD synthesis and applications. Key applications of CD-based sensors in detecting pollutants, biomolecules, and other analytes are examined, emphasizing their potential in environmental monitoring, biological, and food analysis. The review concludes with a discussion on future research directions aimed at overcoming these challenges and enhancing the sustainability of CD-based sensing technologies. Through this detailed exploration, we aim to provide valuable insights into the greenness of CDs, fostering their development as a cornerstone of sustainable sensing technologies. The evaluation tools applied for future probes confirmed their superior environmental friendliness.

Turning Waste into Treasure: Functionalized Biomass-Derived Carbon Dots for Superselective Visualization and Eradication of Gram-Positive Bacteria

Gram-positive bacteria pose significant threats to human health, necessitating the development of targeted bacterial detection and eradication strategies. Nevertheless, current approaches often suffer from poor targeting specificity. Herein, the study utilizes purple rice lixivium to synthesize biomass carbon dots (termed BCDs) with wheat germ agglutinin-like residues for precisely targeting Gram-positive bacteria. Subsequently, fluorescein isothiocyanate (FITC) molecules are grafted onto BCDs to yield FITC-labeled BCDs (termed CDFs), which can selectively and rapidly (≤5 min) stain bacterial cell wall and particularly target the peptidoglycan component. Strikingly, CDFs achieve superselective visualization of Gram-positive bacteria even in the presence of mammalian cells and Gram-negative bacteria. Furthermore, protoporphyrin (PpIX) molecules are conjugated onto BCDs to yield PpIX-modified BCDs (termed CDPs), which can induce bacterial aggregation and in situ generate singlet oxygen for realizing enhanced antibacterial photodynamic therapy (PDT). At the minimum bactericidal concentration of CDPs (PpIX: 5 µg mL-1), CDP-mediated PDT disrupts bacterial structure and metabolism pathways, thereby affecting bacterial interactions to eradicate biofilms. Importantly, CDP-mediated PDT efficiently modulates antiinflammatory responses to promote wound healing in the bacteria-infected mice. This study underscores the significance of harnessing renewable and cost-effective biomass resources for preparing Gram-positive bacteria-targeting theranostic agents, which may find potential clinical applications in the future.

Carbon dots derived from organic drug molecules with improved therapeutic effects and new functions

Carbon dots (CDs) are new types of fluorescent nanomaterials with particle diameters of 1∼10 nm and have excellent photoluminescence (PL) properties, good biocompatibility, simple preparation methods and numerous raw materials; consequently, they are promising in the biomedical field. In recent years, to overcome drug resistance and toxic side effects of traditional organic drugs, the synthesis of CDs from drug molecules has become an effective strategy, which produces CDs with the same therapeutic effects as the raw drugs and even possessing new properties. At present, many CDs derived from organic drugs have been developed, which can be classified according to their sources such as antibiotics, anti-inflammatory drugs, and guanidine drugs. This article focuses on the progress of the above-mentioned drug-derived CDs compared with their drug precursors in terms of therapeutic efficacy, enhanced performance and new additional functions, with special attention to the structure-activity relationship between the drug precursors and the CD-based therapeutic agents. It demonstrates the feasibility of designing new drug-derived CDs for clinical applications, summarizes the shortcomings and research gaps of the existing work, and provides a reference for related work in the future.

Nucleolus-Targeting Carbon Dot Nanocomplexes for Combined Photodynamic/Photothermal Therapy

The low cure rate and high mortality associated with cancer pose significant threats to human health. Photodynamic and photothermal therapies have emerged as promising treatment strategies for various types of cancers. In this study, we successfully synthesized a novel type of carbon dot (CD) using 1,2,4-aminobenzene and ethylenediamine as precursors. Surprisingly, these CDs exhibited outstanding nucleolus-targeting capabilities coupled with a remarkable photothermal effect. Through the integration of these nucleolus-targeting CDs with indocyanine green (ICG) and folic acid (FA), we created CDs-ICG-FA nanocomplexes suitable for combined photodynamic and photothermal therapy. In vitro experiments demonstrated that CDs-ICG-FA maintained a robust photothermal ability, achieving a conversion efficiency of up to 34.3%. Furthermore, CDs-ICG-FA generated abundant reactive oxygen species, effectively inducing cancer cell death and demonstrating its potential for photodynamic therapy. In MCF-7 cancer cells, CDs-ICG-FA exhibited a pronounced synergistic photothermal/photodynamic anticancer effect. Subsequent in vivo experiments in mice revealed that CDs-ICG-FA could selectively accumulate at tumor sites, significantly inhibiting tumor growth upon exposure to an 808 nm laser. These findings suggest that the developed nucleolus-targeting CDs-ICG-FA hold promising potential for cancer targeting and the application of combined photothermal/photodynamic therapy.

Rhodamine-functionalized carbon dots with pH-regulated FRET efficiency for ratiometric fluorescence sensing and imaging of extremely alkaline pH

A ratiometric fluorescent nanoprobe (CDs-Rho), synthesized through the simple covalent amide linkage between carbon dots (CDs) and pH-sensitive rhodamine dye (Rho), was designed for the precise sensing and imaging of extremely alkaline environments. The sensing mechanism involves the opposite pH-dependent fluorescence changes in CDs and Rho, respectively, coupled with pH-regulated FRET efficiency from CDs to Rho. The nanoprobe features a wide pH response window from pH 7.0 to 12.0 with a pKa value of 11.3 and shows high sensitivity, robust anti-interference capability, and high reversibility. Moreover, the significant shifts in emission wavelength following the pH fluctuations result in two well-separated emission signals, thus ensuring the visualization of reversible and distinct color changes (from green to red) during in vivo fluorescence imaging. This work furnished a facile protocol that contributes to the advancement of a novel method for the accurate sensing and imaging of extreme alkaline environments.

d-arginine-functionalized carbon dots with enhanced near-infrared emission and prolonged metabolism time for tumor fluorescent-guided photothermal therapy

Carbon dots (CDs) have garnered significant interest owing to their distinctive optical properties. However, their bioimaging and biomedical applications are limited by pronounced fluorescence (FL) quenching in aqueous media and low tumor accumulation efficacy associated with their ultra-small size. This study proposes a simple surface modification approach using functioning d-arginine on CDs (d-Arg@CDs) to improve their near-infrared (NIR) FL in aqueous solution and maintain their high photothermal conversion properties. Because of the low utilization rate of dextral amino acids in animals, modifying CDs with low molecular weight d-arginine did not increase particle size but extended the metabolism time in blood circulation, thereby leading to enhanced accumulation efficacy at tumor sites in the mice model. The enhanced tumor accumulation of d-Arg@CDs resulted in significantly superior tumor NIR FL imaging and photothermal therapy performance compared with pure CDs and l-arginine functionalized CDs. This dextral amino acid modification approach is expected to be an effective tool for enhancing the biomedical applications of CDs.

Green synthesis and multifaceted applications: challenges and innovations in carbon dot nanocomposites

This paper describes the potential of carbon dot nanocomposites (CDs) synthesized from waste materials by top-down and bottom-up state-of-the-art approaches. Through sustainable practices, wastes are converted into valuable nanomaterials, solving environmental problems and pioneering advances in nanotechnology. In this paper, an overview of the synthesis aspects of CDs is presented with the formation of their versatile nanocomposites and metal/metal oxide elements. The phase of this paper has been devoted to elaborate study of the multifaceted applications of CDs in various sectors, ranging from electronics and biomedicine to environmental remediation. Although having huge potential, CDs application is presently hampered due to limitations on scalability, stability, and reproducibility. In this review paper, most profound insights have been drawn into overcoming these barriers for clear routes toward future innovations. The present research being undertaken in this area has, therefore, underscored sustainable nanotechnology to resolve global problems and achieving technological development through green synthesis. Necessitating the efficient sewage disposal systems ensuring minimum toxin generation.

Carbon dots: synthesis, sensing mechanisms, and potential applications as promising materials for glucose sensors

The disruption of glucose (Glu) metabolism in the human body can lead to conditions such as diabetes and hyperglycemia. Therefore, accurately determining Glu levels is crucial for clinical diagnosis and other applications. Carbon dots (CDs) are a novel category of carbon nanomaterials that exhibit outstanding optical properties, excellent biocompatibility, high water solubility, low production costs, and straightforward synthesis. Recently, researchers have developed various carbon dot sensors for fast and real-time Glu monitoring. In this context, we provide a comprehensive introduction to Glu and CDs for the first time. We categorize the synthetic methods for CDs and the sensing mechanisms, further classifying the applications of carbon dot probes into single-probe sensing, ratiometric sensing, and visual detection. Finally, we discuss the future development needs for CD-based Glu sensors. This review aims to offer insights into advancing Glu sensors and modern medical treatments.

Photothermally Active Quantum Dots in Cancer Imaging and Therapeutics: Nanotheranostics Perspective

Cancer is becoming a global threat, as the cancerous cells manipulate themselves frequently, resulting in mutants and more abnormalities. Early-stage and real-time detection of cancer biomarkers can provide insight into designing cost-effective diagnostic and therapeutic modalities. Nanoparticle and quantum dot (QD)-based approaches have been recognized as clinically relevant methods to detect disease biomarkers at the molecular level. Over decades, as an emergent noninvasive approach, photothermal therapy has evolved to eradicate cancer. Moreover, various structures, viz., nanoparticles, clusters, quantum dots, etc., have been tested as bioimaging and photothermal agents to identify tumor cells selectively. Among them, QDs have been recognized as versatile probes. They have attracted enormous attention for imaging and therapeutic applications due to their unique colloidal stability, optical and physicochemical properties, biocompatibility, easy surface conjugation, scalable production, etc. However, a few critical concerns of QDs, viz., precise engineering for molecular imaging and sensing, selective interaction with the biological system, and their associated toxicity, restrict their potential intervention in curing cancer and are yet to be explored. According to the U.S. Food and Drug Administration (FDA), there is no specific regulation for the approval of nanomedicines. Therefore, these nanomedicines undergo the traditional drug, biological, and device approval process. However, the market survey of QDs is increasing, and their prospects in translational nanomedicine are very promising. From this perspective, we discuss the importance of QDs for imaging, sensing, and therapeutic usage pertinent to cancer, especially in its early stages. Moreover, we also discuss the rapidly growing translational view of QDs. The long-term safety studies and cellular interaction of these QDs could enhance their visibility and bring photothermally active QDs to the clinical stage and concurrently to FDA approval.

Smart chitosan-based nanofibers for real-time monitoring and promotion of wound healing

Timely healing of acute wounds and stopping wound chronicity are current and future priorities in wound therapy. It is urgent and relevant to develop a wound dressing that has antimicrobial and monitors the wound microenvironment in real time. In this study, quaternary ammonium chitosan (HTCC) was selected as the antimicrobial agent and CS/PEO/HTCC nanofiber membranes (CPHs) were prepared by electrostatic spinning technique. The nanofiber membrane (CPH91) with the best antimicrobial performance was screened by the disk diffusion method and drug susceptibility testing by dilution method, and its antimicrobial effect on S. aureus was better than that of E. coli. Subsequently, functional carbon dots (CDs) were synthesized by solvothermal method and doped into CPH91 nanofibers by electrospinning. A good linear relationship between pH value (5.0-8.0) and the fluorescence intensity of CDs was observed. In addition, the nanofibers (CPH91@CDs) had good morphology, hydrophilicity, and biocompatibility. Changes in fluorescence intensity of CPH91@CDs at different pH (5.0-8.0) were monitored and converted into RGB values that were linearly fitted to pH value. Finally, the potential of CPH91@CDs of improving wound healing and instantaneously controlling wound healing process was confirmed by an infected wound model (S. aureus) on the back of SD rats.

Carbon Quantum Dots in Biomedical Applications: Advances, Challenges, and Future Prospects

Carbon quantum dots (CQDs) represent a rapidly emerging class of nanomaterials with significant potential in biomedical applications due to their tunable fluorescence, high biocompatibility, and versatile functionalization. This review focuses on the recent progress in utilizing CQDs for drug delivery, bioimaging, biosensing, and cancer therapy. With their unique optical properties, such as tunable fluorescence, high quantum yield, and photostability, CQDs enable precise bioimaging and sensitive biosensing. Their small size, biocompatibility, and ease of surface functionalization allow for the development of targeted drug delivery systems, enhancing therapeutic precision and minimizing side effects. In cancer therapy, CQDs have shown potential in photodynamic and photothermal treatments by generating reactive oxygen species under light exposure, selectively targeting cancer cells while sparing healthy tissues. Furthermore, CQDs’ ability to penetrate biological barriers including the blood–brain barrier opens new possibilities for delivering therapeutic agents to hard‐to‐reach areas, such as tumors or diseased tissues. However, challenges such as optimizing synthesis, ensuring long‐term stability, and addressing safety concerns in biological environments remain critical hurdles. This review discusses current efforts to overcome these barriers and improve CQD performance in clinical settings, including scalable production methods and enhanced biocompatibility. As research progresses, CQDs are expected to play an important role in improving healthcare by offering more targeted treatment options and contributing to advancements in personalized medicine.

Optimization of Preparation Technology for PET-Based Carbon Dots by Response Surface Method and Its Application

The preparation of polyethylene terephthalate(PET)-based Carbon Dots (PET-CDs) using one-step hydrothermal method with PET waste, pyromellitic acid (PMA) and ammonia (NH3·H2O) as precursors is a high-value utilization strategy for PET waste, offering significant application potential. To achieve efficient recycling of PET waste, response surface methodology was adopted for to optimize the precursor ratio during the synthesis of PET-CDs with fluorescence quantum yield (QY) as the key performance indicator. The optimal preparation conditions were determined to be: 1.180 g of PET, 3.287 g of PMA, 8.969 mL of NH3·H2O, a reaction temperature of 260 °C, and a reaction time of 12 h. The as-prepared PET-CDs exhibit excitation-independent emission properties in the range from 360 nm to 440 nm, with the optimal excitation wavelength of 410 nm and the optimal emission wavelength was 485 nm, resulting in a QY of 83.34%. Structurally, PET-CDs exhibit a spherical morphology, featuring amino and carboxyl groups on their surface, with the particle size ranging from 1.61 to 4.92 nm and an average particle size of 2.88 nm. The prepared PET-CDs can be utilized in light-blocking films (LBFs) and fluorescence anti-counterfeiting technologies. The intensity of light passing through the LBFs significantly is decreased in the ultraviolet and blue light wavelength ranges, with performance comparable to commercial anti-blue light glasses. Additionally, the PET-CDs solution can be adopted for printing patterns that are visible under ultraviolet excitation and are not visible in visible light, demonstrating that PET-CDs can be employed in fluorescence anti-counterfeiting measures.

Magnesium-Doped Carbon Quantum Dot Nanomaterials Alleviate Salt Stress in Rice by Scavenging Reactive Oxygen Species to Increase Photosynthesis

Salt stress has strongly impacted the long-term growth of eco-friendly farming worldwide. By targeting the oxidative stress induced by salt, the utilization of biomass-derived carbon dots (CDs) that possess high-efficiency antioxidant properties, are nontoxic, and have excellent biocompatibility represents a viable and effective approach for enhancing the salt tolerance of plants. In this study, we blended magnesium oxide nanoparticles with carbon sources derived from durian shells to construct Mg-doped carbon dots (Mg-CDs) through a hydrothermal reaction. We demonstrated that the foliar application of 150 μg/mL Mg-CDs to rice plants after treatment with 100 mM salt effectively increased the plant height (9.52%), fresh weight (22.41%), dry weight (33.33%), K+ content (21.46%), chlorophyll content (36.21%), and carotenoid content (16.21%); decreased the malondialdehyde (MDA) (9.43%), Na+ (25.75%), H2O2 (17.50%), and O2•- contents (37.99%); and promoted the photosynthetic system and antioxidant activity. Transcriptome analysis revealed that Mg-CD pretreatment triggered transcriptional reprogramming in rice seedlings. The enrichment analysis of the Kyoto Encyclopedia of Genes and Genomes pathways based on trend groups of gene expression patterns of Profile 8 and Profile 15 indicated that priming with Mg-CDs activated stress signaling- and defense-related pathways, such as metabolic pathways, biosynthesis of secondary metabolites, and photosynthesis pathways. These activations subsequently prompted the expression of genes related to the mitogen-activated protein kinase signaling pathway, hormone signal transduction, the oxidative stress response, and the photosynthetic system. This study demonstrated that the use of Mg-CDs represents a potential strategy to increase plant salt tolerance, creating the possibility for the regulation of crop salinity stress and offering valuable advancements in sustainable agriculture.

Carbon dots for pathogen detection and imaging: recent breakthroughs and future trends

As a class of carbon-based nanomaterials, carbon dots (CDs) have gained a lot of interest for a variety of applications. They offer distinctive optical, chemical, and structural characteristics along with favourable attributes such as low cost, availability of abundant functional groups, remarkable chemical inertness, high stability, exceptional biocompatibility, and ecofriendliness. This review discusses synthesis methods, structural characteristics, and surface modifications of CDs, specific for pathogen detection. Furthermore, it delves into the mechanisms that govern the interaction between pathogens and CDs. In addition, the study explores the use of CDs in a number of detection modalities, such as optical, electrochemical, and electrochemiluminescence, emphasising real-time pathogen monitoring. Moreover, both the challenges and opportunities related to the application of CDs-based detection and imaging methods are highlighted in field and clinical contexts.

Recent Advances in the Synthesis and Optical Applications of Acridine-based Hybrid Fluorescent Dyes

Acridine-based hybrid fluorescent dyes represent a category of dyes that integrate the acridine chromophore with other functional groups or materials to enhance their fluorescence properties. These dyes have garnered substantial attention across various domains, encompassing bioimaging, sensing, and optoelectronics. In recent years, researchers have directed their efforts toward fabricating acridine-based hybrid fluorescent dyes with improved water solubility, biocompatibility, and targeting capabilities. These advancements have facilitated their utilization in biological imaging applications, such as monitoring cellular processes, investigating protein-protein interactions, and detecting specific biomolecules. This review delineates the recent progress in synthesizing acridine-based hybrid fluorescent dyes and their applications in optical properties over the past decade. This review is anticipated to catalyze the development of innovative fluorescent materials featuring heightened properties and functionalities.

Biomass-derived carbon dots with pharmacological activity for biomedicine: Recent advances and future perspectives

Carbon dots (CDs), a type of nanoparticle with excellent optical properties, good biocompatibility, and small size, are finding increasing application across the fields of biology and biomedicine. In recent years, biomass-derived CDs with pharmacological activity (BP-CDs) derived from herbal medicines (HMs), HMs extracts and other natural products with demonstrated pharmaceutical activity have attracted particular attention. Herein, we review recent advances in the development of BP-CDs, covering the selection of biomass precursors, different methods used for the synthesis of BP-CDs from natural sources, and the purification of BP-CDs. Additionally, we summarize the many remarkable properties of BP-CDs including optical properties, biocompatibility and pharmaceutical efficacy. Moreover, the antibacterial, antiviral, anticancer, biosensing, bioimaging, and other applications of BP-CDs are reviewed. Thereafter, we discuss the advantages and disadvantages of BP-CDs and Western drug-derived CDs, highlighting the excellent performance of BP-CDs. Finally, based on the current state of research on BP-CDs, we suggest several aspects of BP-CDs that urgently need to be addressed and identify directions that should be pursued in the future. This comprehensive review on BP-CDs is expected to guide the precise design, preparation, and future development of BP-CDs, thereby advancing the application of BP-CDs in biomedicine.

Advances in Shell and Core Engineering of Carbonized Polymer Dots for Enhanced Applications

ConspectusCarbon dots (CDs), as a novel type of fluorescent nanocarbon material, attract widespread attention in nanomedicine, optoelectronic devices, and energy conversion/storage due to their excellent optical properties, low toxicity, and high stability. They can be classified as graphene quantum dots, carbon quantum dots, and carbonized polymer dots (CPDs). Among these, CPDs exhibit tunable structures and components that allow fine-tuning of their optoelectronic properties, making them one of the most popular types of CDs in recent years. However, the structural complexity of CPDs stimulates deep exploration of the relationship between their unique structure and luminescent performance. As an organic-inorganic hybrid system, the diversity of self-limited quantum state carbon cores and polymer-hybrid shell layers makes understanding the underlying mechanisms and structure-property relationships in CPDs a very challenging task. In this context, elucidating the structural composition of CPDs and the factors that affect their optical properties is vital if the enormous potential of CPDs is to be realized. Achieving controllable structures with predefined optical properties via the adoption of specific functionalization strategies is the prized goal of current researchers in the field.In this Account, we describe the efforts made by our group in the synthesis, mechanism analysis, structural regulation, and functional applications of CPDs, with particular emphasis on the design of CPDs core-shell structures with tailored optoelectronic properties for applications in the fields of optoelectronics and energy. Specifically, through the rational selection of precursors, optimization of reaction conditions, and postmodification strategies for CPDs, we have demonstrated that it is possible to regulate both the carbon core and polymer shell layers, thereby achieving full-spectrum emission, high quantum yield, persistent luminescence, thermally activated delayed fluorescence, and laser action in CPDs. Furthermore, we have established structure-performance relationship in CPDs and proposed a universal strategy for synergistic interactions between hybrid carbon-based cores and surface micronanostructures. In addition, we unveiled a novel luminescence mechanism in cross-linked CPDs, specifically "cross-linking synergistically inducing quantum-state luminescence", which addresses the challenge of efficient circularly polarized luminescence in the liquid and solid phases of CPDs. Subsequently, strong cross-linking, dual-rigidity, and ordering preparation methods were introduced, thereby pioneering tunable laser emission from blue to near-infrared wavelengths. Additionally, we developed a new strategy of "confined composite nanocrystals of CPDs", leading to various high-performance hydrogen evolution catalysts for water electrolysis. The CPDs developed by this strategy not only possessed excellent optical properties but also enabled high efficiencies in field of energy conversion, thus maximizing the utilization of CPDs. Finally, we discuss important new trends in CPD research and development. Overall, this Account summarizes the latest advancements in CPDs in recent years, providing case-studies that enable deep understanding of structure-property-performance relationships and regulation strategies in CPDs, guiding the future expansion and application of CPDs.

Nanotechnology-Mediated Immunomodulation Strategy for Inflammation Resolution

Inflammation serves as a common characteristic across a wide range of diseases and plays a vital role in maintaining homeostasis. Inflammation can lead to tissue damage and the onset of inflammatory diseases. Although significant progress is made in anti-inflammation in recent years, the current clinical approaches mainly rely on the systemic administration of corticosteroids and antibiotics, which only provide short-term relief. Recently, immunomodulatory approaches have emerged as promising strategies for facilitating the resolution of inflammation. Especially, the advanced nanosystems with unique biocompatibility and multifunctionality have provided an ideal platform for immunomodulation. In this review, the pathophysiology of inflammation and current therapeutic strategies are summarized. It is mainly focused on the nanomedicines that modulate the inflammatory signaling pathways, inflammatory cells, oxidative stress, and inflammation targeting. Finally, the challenges and opportunities of nanomaterials in addressing inflammation are also discussed. The nanotechnology-mediated immunomodulation will open a new treatment strategy for inflammation therapy.

Antioxidant Carbon Dots Nanozymes Alleviate Stress-induced Depression by Modulating Gut Microbiota

Depression is a debilitating mental illness that severely threatens millions of individuals and public health. Because of the multifactorial etiologies, there is currently no cure for depression; thus, it is urgently imperative to find alternative antidepressants and strategies. Growing evidence underscores the prominent role of oxidative stress as key pathological hallmarks of depression, making oxidative stress a potential therapeutic target. In this study, we report a N-doped carbon dot nanozyme (CDzyme) with excellent antioxidant capacity for treating depression by remodeling redox homeostasis and gut microbiota. The CDzymes prepared via microwave-assisted fast polymerization of histidine and glucose exhibit superior biocompatibility. Benefiting from the unique structure, CDzymes can provide abundant electrons, hydrogen atoms, and protons for reducing reactions, as well as catalytic sites to mimic redox enzymes. These mechanisms collaborating endow CDzymes with broad-spectrum antioxidant capacity to scavenge reactive oxygen and nitrogen species (•OH, O2-•, H2O2, ONOO-), and oxygen/nitrogen centered free radicals. A depression animal model was established by chronic unpredictable mild stress (CUMS) to evaluate the therapeutic efficacy of CDzymes from the behavioral, physiological, and biochemical index and intestinal flora assessments. CDzymes can remarkably improve depression-like behaviors and key neurotransmitters produced in hippocampus tissues and restore the gut microbiota compositions and the amino acid metabolic functions, proving the potential in treating depression through the intestinal-brain axis system. This study will facilitate the development of intestinal flora dysbiosis nanomedicines and treatment strategies for depression and other oxidative stress related multifactorial diseases.

Carbonized Polymer Dots: Influence of the Carbon Nanoparticle Structure on Cell Biocompatibility

Carbonized polymer dots (CPDs) were obtained by using microwave irradiation under the same conditions. However, different carbogenic precursors were used, such as aromatic diamine molecules, ortho-phenylenediamine (o-OPDA), and 3,4-diaminobenzoic acid (3,4-DABA). Both carbon nanoparticles showed different structural results based on Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and atomic force microscopy analyses. However, there are similar spectroscopic (UV-visible and fluorescence emission) profiles. The photophysical results, like quantum yield (QY) and fluorescence lifetime, were not identical; CPDs-OPDA has a higher QY and fluorescence lifetime than CPDs-3,4-DABA. CPDs-3,4-DABA presents a more hydrophobic character than CPDs-OPDA and has a more negative superficial charge. Cell viability studies in both standard and tumor lines demonstrated higher cytotoxicity from CPDs-OPDA than that from CPDs-3,4-DABA. The oxidative stress identified in cells treated with CPDs-OPDA was based on reactive oxygen species and associated with nitric oxide production. CPDs-3,4-DABA showed more DPHH inhibition than CPDs-OPDA, indicating the antioxidant activity of CPDs.

Carbon Dots: A Versatile Platform for Cu2+ Detection, Anti-Counterfeiting, and Bioimaging

Carbon dots (CDs) have garnered extensive interest in basic physical chemistry as well as in biomedical applications due to their low cost, good biocompatibility, and great aqueous solubility. However, the synthesis of multi-functional carbon dots has always been a challenge for researchers. Here, we synthesized novel CDs with a high quantum yield of 28.2% through the straightforward hydrothermal method using Diaminomaleonitrile and Boc-D-2, 3-diaminopropionic acid. The size, chemical functional group, and photophysical properties of the CDs were characterized by TEM, FTIR, XPS, UV, and fluorescence. It was demonstrated in this study that the prepared CDs have a high quantum yield, excellent photostability, and low cytotoxicity. Regarding the highly water-soluble property of CDs, they were proven to possess selective and sensitive behavior against Cu2+ ions (linear range = 0-9 μM and limit of detection = 1.34 μM). Moreover, the CDs were utilized in fluorescent ink in anti-counterfeiting measures. Because of their low cytotoxicity and good biocompatibility, the CDs were also successfully utilized in cell imaging. Therefore, the as-prepared CDs have great potential in fluorescence sensing, anti-counterfeiting, and bioimaging.

Ultra-Photostable Bacterial-Seeking Near-Infrared CPDs for Simultaneous NIR-II Bioimaging and Antibacterial Therapy

Bacterial infections can pose significant health risks as they have the potential to cause a range of illnesses. These infections can spread rapidly and lead to complications if not promptly diagnosed and treated. Therefore, it is of great significance to develop a probe to selectively target and image pathogenic bacteria while simultaneously killing them, as there are currently no effective clinical solutions available. This study presents a novel approach using near-infrared carbonized polymer dots (NIR-CPDs) for simultaneous in vivo imaging and treatment of bacterial infections. The core-shell structure of the NIR-CPDs facilitates their incorporation into bacterial cell membranes, leading to an increase in fluorescence brightness and photostability. Significantly, the NIR-CPDs exhibit selective bacterial-targeting properties, specifically identifying Staphylococcus aureus (S. aureus) while sparing Escherichia coli (E. coli). Moreover, under 808 nm laser irradiation, the NIR-CPDs exhibit potent photodynamic effects by generating reactive oxygen species that target and damage bacterial membranes. In vivo experiments on infected mouse models demonstrate not only precise imaging capabilities but also significant therapeutic efficacy, with marked improvements in wound healing. The study provides the dual-functional potential of NIR-CPDs as a highly effective tool for the advancement of medical diagnostics and therapeutics in the fight against bacterial infections.

Semiconducting Polymer Dots for Dual-Wavelength Differential Background-Suppressed Photoacoustic Imaging

Photoacoustic imaging (PAI) can sensitively detect regions and substances with strong optical absorption, which means that diseased tissue can be imaged with high contrast in the presence of surrounding healthy tissue through the photoacoustic effect. However, its signal intensity and resolution may be limited by background signals generated by endogenous chromophores such as melanin and hemoglobin. A feasible method for practical application of this so-called background-suppressed PAI is still lacking. In this work, a dual-wavelength differential background noise-suppressed photoacoustic tomography is developed based on organic semiconducting polymer dots (Pdots). The Pdots have a strong absorption peak at 945 nm, and then the absorption decreases sharply with the increase of wavelength, and the absorption intensity drops to only about a quarter of the original value at 1050 nm. The present system significantly suppresses the strong background noise of blood through dual-wavelength differential PAI, enabling precise monitoring of the distribution information of theranostic agents in diseased tissues. The signal-to-noise ratio of the theranostic agent distribution map is increased by about 20 dB. This work provides a platform for real-time and accurate monitoring of tumors and drugs, which helps avoid damage to healthy tissue during treatment and has clinical significance in cancer treatment.

An injectable chitosan-based hydrogel incorporating carbon dots with dual enzyme-mimic activities for synergistically treatment of bacteria infected wounds

Bacterial infections pose a serious threat to human health, and the emergence of superbugs and the growing antibiotic resistance phenomenon have made the development of novel antimicrobial products. In this paper, an ultrasmall Cu, N co-doped carbon dots (CDs-Cu-N) with excellent peroxidase mimic activity and enhanced catalase mimic activity was successfully prepared and anchored to an injectable chitosan (CS)-based hybrid hydrogel. As expected, the CDs-Cu-N-H2O2-CS hybrid hydrogel maintains the excellent enzyme-mimicking properties of CDs-Cu-N and shows superior antibacterial property, which has been proven to effectively promote the healing of S. aureus-infected wounds with good biocompatibility. Benefitting from the dual-enzyme-mimic activity of CDs-Cu-N, the hybrid hydrogel not only can catalyze the generation of highly toxic ROS from low concentration of H2O2 to inhibit the bacterial infections, but also can significantly promote the wound tissue repair and regeneration by improving the anoxic microenvironment and promoting neovascularization. In addition, this hybrid hydrogel also possessed excellent injectability and moldability. It can adapt to various the irregular shapes of acute wounds, maintaining a moist and safe microenvironment while prolonging the action time of nanozyme on wounds, thus promoting wound healing. This injectable hybrid hydrogel shows great potential applications in the field of wound infection management.

Nitrogen-Doped Carbon Dots: A New Powerful Fluorescent Dye with Substantial Effect on Bacterial Cell Labeling

Carbon dots (CDs)-minute carbon nanoparticles with remarkable luminescent properties, photostability, and low toxicity-show potential for various applications. CDs synthesized using citric acid and urea are the least toxic to biological environments. Here, we aimed to explore the effect of CDs synthesized using citric acid and urea at 50, 33, and 25% (CDs 1/1, 1/2, and 1/3, respectively) weight ratios in a microwave on bacterial cell fluorescence sensing and labeling. The nanoscale properties of CDs were investigated via transmission electron microscopy and dynamic light scattering particle size analysis. X-ray powder diffraction confirmed the graphitic structures of CDs. X-ray photoelectron spectroscopy revealed that the nitrogen content increased gradually with increasing urea ratios, indicating functional group changes. Transient photoluminescence decay periods demonstrated superior fluorescence intensity of CDs 1/3 under blue, green, and red lights. The use of CDs was notably more efficient than traditional methods in staining bacterial cells. Fluorescence microscopy of 10 g-positive and 10 g-negative bacteria revealed enhanced staining of Gram-positive strains, with CDs 1/3 presenting the best results. The CDs exhibited excellent photostability, maintaining poststaining fluorescence for 100 min, surpassing the performance of conventional dyes. CDs could serve as potential fluorescent dyes for the rapid discrimination of Gram-positive and Gram-negative bacteria.

Antioxidant Carbon Dots and Ursolic Acid Co-Encapsulated Liposomes Composite Hydrogel for Alleviating Adhesion Formation and Enhancing Tendon Healing in Tendon Injury

Background

The formation of adhesion after tendon injury represents a major obstacle to tendon repair, and currently there is no effective anti-adhesion method in clinical practice. Oxidative stress, inflammation, and fibrosis can occur in tendon injury and these factors can lead to tendon adhesion. Antioxidant carbon dots and ursolic acid (UA) both possess antioxidant and anti-inflammatory properties. In this experiment, we have for the first time created RCDs/UA@Lipo-HAMA using red fluorescent carbon dots and UA co-encapsulated liposomes composite hyaluronic acid methacryloyl hydrogel. We found that RCDs/UA@Lipo-HAMA could better attenuate adhesion formation and enhance tendon healing in tendon injury.

Materials and Methods

RCDs/UA@Lipo-HAMA were prepared and characterized. In vitro experiments on cellular oxidative stress and fibrosis were performed. Reactive oxygen species (ROS), and immunofluorescent staining of collagens type I (COL I), collagens type III (COL III), and α-smooth muscle actin (α-SMA) were used to evaluate anti-oxidative and anti-fibrotic abilities. In vivo models of Achilles tendon injury repair (ATI) and flexor digitorum profundus tendon injury repair (FDPI) were established. The major organs and blood biochemical indicators of rats were tested to determine the toxicity of RCDs/UA@Lipo-HAMA. Biomechanical testing, motor function analysis, immunofluorescence, and immunohistochemical staining were performed to assess the tendon adhesion and repair after tendon injury.

Results

In vitro, the RCDs/UA@Lipo group scavenged excessive ROS, stabilized the mitochondrial membrane potential (ΔΨm), and reduced the expression of COL I, COL III, and α-SMA. In vivo, assessment results showed that the RCDs/UA@Lipo-HAMA group improved collagen arrangement and biomechanical properties, reduced tendon adhesion, and promoted motor function after tendon injury. Additionally, the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) in the RCDs/UA@Lipo-HAMA group increased; the levels of cluster of differentiation 68 (CD68), inducible Nitric Oxide Synthase (iNOS), COL III, α-SMA, Vimentin, and matrix metallopeptidase 2 (MMP2) decreased.

Conclusion

In this study, the RCDs/UA@Lipo-HAMA alleviated tendon adhesion formation and enhanced tendon healing by attenuating oxidative stress, inflammation, and fibrosis. This study provided a novel therapeutic approach for the clinical treatment of tendon injury.

Fabrication of a ratiometric fluorescent probe based on Tb3+ doped dual-emitting carbon dots for the detection of cytochrome c

Cytochrome c (Cyt-c) was commonly an intrinsic biomarker for a variety of cellular characteristics, such as respiration, energy levels, and apoptosis. Herein, a simple fluorescence sensor was constructed for the detection of Cyt-c in buffer and real serum samples. The carbon dots doped with Tb3+ on the premise of 1-(2-pyridylazo)-2-naphthol (PAN) were fabricated and used as a dual-emission ratiometric fluorescent probe for detecting Cyt-c based on the internal filtering effect (IFE). As a fluorescent probe for ultra-sensitive detection, Cyt-c was quantitatively detected at different concentrations from 1 to 1000 nM. The fluorescent detection method for Cyt-c showed a good linear relationship from 1 to 50 nM, and the limit of detection (LOD) was 0.35 nM. In the recovery range of 101.27-103.39 % in human serum samples, the relative standard deviation (RSD) was less than 3.27 % (n = 3). In the end, the possible structures of CDs were predicted by DFT theoretical simulation calculations. All the results proved the ability of carbon dots as fluorescent probes to detect biomarkers and the application prospects in bioanalysis.

The Emerging Star of Carbon Luminescent Materials: Exploring the Mysteries of the Nanolight of Carbon Dots for Optoelectronic Applications

Carbon dots (CDs), a class of carbon-based nanomaterials with dimensions less than 10 nm, have attracted significant interest since their discovery. They possess numerous excellent properties, such as tunability of photoluminescence, environmental friendliness, low cost, and multifunctional applications. Recently, a large number of reviews have emerged that provide overviews of their synthesis, properties, applications, and their composite functionalization. The application of CDs in the field of optoelectronics has also seen unprecedented development due to their excellent optical properties, but reviews of them in this field are relatively rare. With the idea of deepening and broadening the understanding of the applications of CDs in the field of optoelectronics, this review for the first time provides a detailed summary of their applications in the field of luminescent solar concentrators (LSCs), light-emitting diodes (LEDs), solar cells, and photodetectors. In addition, the definition, categories, and synthesis methods of CDs are briefly introduced. It is hoped that this review can bring scholars more and deeper understanding in the field of optoelectronic applications of CDs to further promote the practical applications of CDs.

Nanomaterial-Based Sensors for Coumarin Detection

Sensors are widely used owing to their advantages including excellent sensing performance, user-friendliness, portability, rapid response, high sensitivity, and specificity. Sensor technologies have been expanded rapidly in recent years to offer many applications in medicine, pharmaceuticals, the environment, food safety, and national security. Various nanomaterial-based sensors have been developed for their exciting features, such as a powerful absorption band in the visible region, excellent electrical conductivity, and good mechanical properties. Natural and synthetic coumarin derivatives are attracting attention in the development of functional polymers and polymeric networks for their unique biological, optical, and photochemical properties. They are the most abundant organic molecules in medicine because of their biological and pharmacological impacts. Furthermore, coumarin derivatives can modulate signaling pathways that affect various cellular processes. This review covers the discovery of coumarins and their derivatives, the integration of nanomaterial-based sensors, and recent advances in nanomaterial-based sensing for coumarins. This review also explains how sensors work, their types, their pros and cons, and sensor studies for coumarin detection in recent years.

Emerging Trends in Nanomedicine: Carbon-Based Nanomaterials for Healthcare

Carbon-based nanomaterials, such as carbon quantum dots (CQDs) and carbon 2D nanosheets (graphene, graphene oxide, and graphdiyne), have shown remarkable potential in various biological applications. CQDs offer tunable photoluminescence and excellent biocompatibility, making them suitable for bioimaging, drug delivery, biosensing, and photodynamic therapy. Additionally, CQDs' unique properties enable bioimaging-guided therapy and targeted imaging of biomolecules. On the other hand, carbon 2D nanosheets exhibit exceptional physicochemical attributes, with graphene excelling in biosensing and bioimaging, also in drug delivery and antimicrobial applications, and graphdiyne in tissue engineering. Their properties, such as tunable porosity and high surface area, contribute to controlled drug release and enhanced tissue regeneration. However, challenges, including long-term biocompatibility and large-scale synthesis, necessitate further research. Potential future directions encompass theranostics, immunomodulation, neural interfaces, bioelectronic medicine, and expanding bioimaging capabilities. In summary, both CQDs and carbon 2D nanosheets hold promise to revolutionize biomedical sciences, offering innovative solutions and improved therapies in diverse biological contexts. Addressing current challenges will unlock their full potential and can shape the future of medicine and biotechnology.

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.

The Enhanced Photoluminescence Properties of Carbon Dots Derived from Glucose: The Effect of Natural Oxidation

The investigation of the fluorescence mechanism of carbon dots (CDs) has attracted significant attention, particularly the role of the oxygen-containing groups. Dual-CDs exhibiting blue and green emissions are synthesized from glucose via a simple ultrasonic treatment, and the oxidation degree of the CDs is softly modified through a slow natural oxidation approach, which is in stark contrast to that aggressively altering CDs' surface configurations through chemical oxidation methods. It is interesting to find that the intensity of the blue fluorescence gradually increases, eventually becoming the dominant emission after prolonging the oxidation periods, with the quantum yield (QY) of the CDs being enhanced from ~0.61% to ~4.26%. Combining the microstructure characterizations, optical measurements, and ultrafiltration experiments, we hypothesize that the blue emission could be ascribed to the surface states induced by the C-O and C=O groups, while the green luminescence may originate from the deep energy levels associated with the O-C=O groups. The distinct emission states and energy distributions could result in the blue and the green luminescence exhibiting distinct excitation and emission behaviors. Our findings could provide new insights into the fluorescence mechanism of CDs.

ROS-Responsive Poly(α-l-lysine)-Based Nanoparticles Loaded with Doxycycline Combat Oxidative Stress and Bacterial Infection

Bacterial pneumonia is one of the major threats in clinical practice, and the reactive oxygen species (ROS) generated at the infection site can exacerbate the damage. Currently, conventional antibiotic therapies have low utilization, and their excessive use can result in substantial toxicity. Nanocarrier systems provide an ideal approach for treating bacterial infection by facilitating more efficient utilization of antibiotics. In this study, the ROS-responsive amphiphilic nanoparticles (NPs) are developed and used to encapsulate the antibiotic doxycycline (DOXY) to achieve antibacterial and antioxidant functionalities. The NPs are prepared from poly(α-l-lysine) (α-PLL) and phenylboronic acid pinacol ester simultaneously conjugated carbonyldiimidazole (abbreviated as CDIPB). The phenylboronic acid ester groups on CDIPB could react with excessive ROS to suppress oxidative damage at the infection site. The ROS-responsive degradation of CDIPB also facilitates the rapid release of internal DOXY, effectively killing the accumulated bacteria. Additionally, in vitro cell experiments demonstrate the good biocompatibility of the NPs. These results suggest that the ROS-responsive amphiphilic nanoparticles can serve as a novel nanoplatform for the treatment of bacterial pneumonia.