Antibacterial Carbon Dots: Mechanisms, Design, and Applications

Dual oxygen supply system of carbon dot-loaded microbubbles with acoustic cavitation for enhanced sonodynamic therapy in diabetic wound healing

Diabetic wounds present significant treatment challenges due to their complex microenvironment, marked by persistent inflammation from bacterial infections, hypoxia caused by diabetic microangiopathy, and biofilm colonization. Sonodynamic therapy (SDT) offers potential for treating such wounds by targeting deep tissues with antibacterial effects, but its efficacy is limited by hypoxic conditions and biofilm barriers. To overcome these obstacles, we developed a novel approach using oxygen-carrying microbubbles loaded with Mn2+-doped carbon dots (MnCDs@O2MBs) to enhance SDT and disrupt biofilms. Through precursor screening and design, MnCDs are engineered to exhibit tailored properties of sonodynamic activity and enzyme-like catalytic capabilities. This system provides a dual oxygen supply for amplifying the SDT effects: MnCDs, serving as a sonosensitizer, also chemically convert excess H2O2 at infection sites into oxygen, while the O2MBs physically release oxygen through ultrasound-induced cavitation. The cavitation effect also disrupts biofilms, improving the delivery of sonosensitizers and boosting SDT efficacy. In a diabetic wound model, this strategy downregulated TLR, NF-κB, and TNF inflammatory pathways, reduced pro-inflammatory factor secretion, promoted angiogenesis, and accelerated wound healing, thereby acting as a promising treatment approach for diabetic wound healing.

Green biomass carbon points with efficient broad-spectrum antibacterial activity and widespread application

With low toxicity and good biocompatibility, carbon dots (CDs) are widely used in the fields of biosensing and drug delivery. In recent years, they have demonstrated excellent antimicrobial properties, thus becoming another research hotspot in the antimicrobial field. However, most of the studies showed that CDs were effective in inhibiting Gram-positive bacteria but ineffective against Gram-negative bacteria. In this study, macadamia nutshell (MNS)-CDs were prepared from the hard shells of macadamia nuts by a one-step hydrothermal method, and their appearance, morphology, structural composition, antimicrobial properties, and toxicity were investigated. The results showed that the MNS-CDs were spherical particles with an average diameter of about 4.25 nm, with hydrophilic groups, a hemolysis rate of less than 2%, good biocompatibility, and excellent antimicrobial properties against both Gram-negative and Gram-positive bacteria. The antimicrobial mechanism of these materials was also investigated. The inhibition of Gram-negative bacteria by MNS-CDs was mainly due to electrostatic interactions, while the inhibition of Gram-positive bacteria was mainly based on activated oxygen sterilization. Furthermore, MNS-CDs achieved good antimicrobial effects when applied in the fields of water purification, plates, fabrics, and food packaging, indicating that the prospects of their broad application are good.

Dextran guanidinylated carbon dots with antibacterial and immunomodulatory activities as eye drops for the topical treatment of MRSA-induced infectious keratitis

Bacterial keratitis (BK) develops rapidly and can cause serious consequences, requiring timely and efficient treatment. As the main treatment strategy, antibiotic eye drops are still plagued by bacterial resistance by biofilms and failure to modulate immunity. Herein, dextran guanidinylated carbon dots (DG-CDs) with antimicrobial and immunomodulatory properties were developed. DG-CDs with the graphitized core-like structure with the ordered arrangement of carbon atoms and surface groups of CN, COC, and -OH were thoroughly characterized and modeled as a graphene-like sheet. DG-CDs exhibited strong antimicrobial and anti-biofilm activities with a minimum inhibitory concentration (MIC) of 5 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA). Molecular docking based on well-characterized structures of DG-CDs revealed that DG-CDs had strong affinity for key bacterial proteins including FtsA, IcaA and ArgA, which were confirmed by corresponding RT-qPCR and transcriptomics. Furthermore, DG-CDs regulated macrophage polarization by inhibiting the M1 subtype and promoting the transition to the M2 subtype. In vivo experiments illustrated that DG-CDs used as eye drops significantly attenuated corneal infection, enhanced the expression of anti-inflammatory factors, and effectively promoted corneal repair in MRSA-infected BK. Overall, this study provides a promising antibacterial nanomaterial with clarified properties and acting mechanism for treating BK as eye drops. STATEMENT OF SIGNIFICANCE: Besides bacterial invasion, bacterial keratitis (BK) also suffers from immune imbalance, which further impairs corneal healing. Current antibiotic eye drops are plagued by bacterial resistance and their inability to modulate immunity. Herein, dextran guanidinylated carbon dots (DG-CDs) with dual functions of antimicrobial and immunomodulatory were developed for treating MRSA infected BK. DG-CDs, with clarified structure and surface groups, exhibited strong antimicrobial activity and no detectable resistance. Molecular docking, based on well-characterized structures of DG-CDs, was achieved to reveal the antibacterial mechanism, which was subsequently confirmed by RT-qPCR and transcriptomics. In addition, DG-CDs exhibited an effective healing ability in an MRSA-infected rat keratitis model by exerting antibacterial activity and regulating macrophage polarization from M1 type to M2 type. DG-CDs represent a promising antibacterial nanomedicine with clarified properties and acting mechanism for treating bacterial infection.

The Use of Carbon Dots for Food Packaging and Preservation: Toxic or Beneficial?

Carbon dots (CDs), which are emerging as versatile nanomaterials, have gained interest in food packaging and preservation due to their sustainable origin and multifunctional characteristics, such as antimicrobial, antioxidant, and UV-protective properties. CDs can be synthesized from biomass and have been proposed as functional additives to packaging material to improve the safety and shelf life of the packaged food. Despite these benefits, concerns are raised about their potential toxicity when leached into foods, especially since they belong to the nanomaterial category. Interestingly, foodborne CDs, which are naturally formed in heat-processed foods and have been consumed by humans for centuries, add a new complexity to the debate. Although there is no definitive evidence linking these endogenous CDs to adverse health effects, some studies suggest their potential to interfere with metabolism in animal models. In addition, the presence of hazardous substances in thermally processed foods, such as polycyclic aromatic hydrocarbons (PAHs), may further complicate safety assessment. This review addresses the paradox of CD from food and packaging sources, highlighting its dual role as both a potentially toxic agent and a beneficial functional material. More extensive research is essential to fully understand the long-term effects of CD on human health and to determine whether its use in food packaging is truly safe or beneficial.

Carbon-based metal oxide nanocomposites for water treatment by photocatalytic processes

The increasing contamination of water by emerging contaminants and the need for more efficient and sustainable treatment methods have prompted the exploration of advanced materials and technologies, with a particular focus on photocatalysis. Carbon-based metal oxide nanocomposites are a promising solution for the treatment of polluted water. This paper aims to review the current state of research on the application of these nanocomposites as photocatalysts for complete water treatment, describing breakthroughs in contaminant removal from 2019 through 2024 and milestones in water disinfection from 2016 through 2024. It includes discussion on the utilization of nanocomposites of Metal Oxides (MOs) with carbon materials to improve photocatalytic efficiency and addresses the advantages and drawbacks of these materials, including electron-hole recombination and agglomeration. The review focuses on the photocatalytic mechanisms of these nanocomposites and highlights the importance of heterostructures formed between metal oxides and carbon materials (e.g., graphene, carbon nanotubes, and carbon quantum dots), which enhance light absorption and hydroxyl radical generation, thereby increasing the efficiency of pollutant degradation and water disinfection. The review describes the properties of different MOs (n-type and p-type), exploring synergies between MOs and carbon materials and discussing the benefits and challenges of their application in wastewater treatment and pathogen inactivation. The review ends with a scientometric analysis of research trends in this field.

Smearable CQD-entrapped hydrogel with sensitive pH response and photodynamic antibacterial properties for visual intelligent wound monitoring

The treatment of chronic wounds remains a significant challenge in the clinical field, and optimizing the treatment plan through visual monitoring of wound healing is an effective way to solve such problem. Herein, we propose a feasible strategy to construct a smearable C-P-T/mCQDs hydrogel for real-time monitoring of wound infection and healing status, through the synergistic combination of modified carbon quantum dots (mCQD), cellulose nanofiber, tannic acid, and polyvinyl alcohol. The hydrogel can be readily applied on the skin and rapidly forms a gel dressing through high-density hydrogen bonding, demonstrating exceptional mechanical robustness (tensile elongation: 600 %) and autonomous self-healing capabilities. In particular, the carboxyl-rich mCQDs are more easily recognized by the sensitive pH-mediated polychromatic fluorescence response under ultraviolet excitation, exhibiting encouraging photodynamic therapy effect against bacterial infections. Under the irradiation of sunlight or near-infrared laser, the hydrogel achieves 99.99 % bactericidal efficacy against multiple types of bacteria (S. aureus, E. coli, P. aeruginosa, A. baumannii) within 20 min through reactive oxygen species generation. Furthermore, C-P-T/mCQDs demonstrates excellent antioxidant activity, biocompatibility, hemostatic efficiency and pro-healing properties. Notably, the mCQD-integrated hydrogel enables real-time, visual monitoring of wound status through its pH-responsive properties, providing substantial translational potential for personalized chronic wound management.

Polyvalent aptamer DNA nanoassembly based near-infrared carbon dots and rolling circle amplification for synergistic therapy of breast cancer

Integrating imaging and therapy is of great significance in the field of tumor treatment. Here, we report a polyvalent aptamer nanoplatform for breast cancer cell treatment based on rolling circle amplification (RCA). The platform consists of a long single-stranded DNA scaffold from RCA and short-stranded DNAs with various functions. One short strand is linked to near-infrared carbon dots (NIR-CDs), another carries a MUC1 aptamer targeting cancer cells, and the third loads small interfering RNA (siRNA) for gene therapy. Doxorubicin (Dox) attaches to the platform via CG base pairs, integrating fluorescence targeting, photothermal therapy (PTT), gene therapy, and chemotherapy. Aptamer enhances breast cancer cell uptake of the platform. NIR-CDs serve as fluorescence imaging agents and are used for PTT. When deoxyribonucleases degrade the nanoplatform, Dox is released and then exerts its chemotherapeutic effect. SiRNA can form the RNA-induced silencing complex to reduce drug tolerance and enhance the efficacy of loaded drugs. The experimental results show that the platform can accumulate in cancer cells, exert a killing effect on them, and meanwhile reduce side effects on normal cells. In summary, this study expands the application of DNA materials in biomedicine by constructing a diagnostic and therapeutic platform that integrates NIR-CDs and RCA.

Antifungal Performance and Mechanisms of Carbon Quantum Dots in Cellulosic Materials

Cellulosic materials, which are widely utilized in daily life, are highly susceptible to fungal degradation. However, commercial fungicides are usually toxic, posing severe threats to human health and the environment, highlighting the necessity of developing eco-friendly antifungal agents for cellulosic materials. In this work, we synthesized nitrogen-doped carbon quantum dots (CQDs) via a microwave-assisted method. CQDs with proper structure demonstrated significant antifungal effects against both brown-rot (Postia placenta, Pp) and white-decay fungi (Trametes versicolor, Tv) on various cellulosic materials. The underlying antifungal mechanisms of CQDs on cellulosic materials were further elucidated. We found that positively charged nanosized CQDs primarily adhered to and penetrated into fungal cell membranes. This led to fungal metabolism disorder, a significant reduction in enzymatic activities, and ultimately cell death, as confirmed by transcriptome analysis. Additionally, CQDs generated reactive oxygen species (ROS) under light, causing oxidation and dysfunction of the fungal cell wall. Furthermore, CQDs have the ability to chelate Fe3+, which results in the inhibition of the Fenton reaction and the hindering of the nonenzymatic cellulose degradation. These findings suggest that CQDs inhibit fungal degradation of cellulosic materials through integrated mechanisms, with potential implications for sustainable cellulose applications.

Norfloxacin-Derived Carbon Dots with Rich Electron Pyrrolic Nitrogen for Copper Corrosion Inhibition and Antibacterial Functions

The coexisting anticorrosion and antibacterial functions are of great significance for the marine industry. Controllable surface negative charge and wettability of pyrrolic nitrogen-doped carbon dots (NCDs) derived from the single antibiotic norfloxacin precursor with a special nitrogen heterocyclic structure were successfully fabricated through the hydrothermal route. The incorporated functional groups and chemical bonds, surface charge, mechanism of pyrrole nitrogen ring formation at the molecular level, and antibacterial properties of NCDs were revealed by FTIR, XPS, zeta potential, LC-MS, and electrochemical techniques. The present corrosion efficiency (96.1%) in 3.5 wt % NaCl saline solution in the presence of air and N2 or UO22+ is higher than most previously reported values. The proposed electron transfer corrosion mechanism suggests that the negative charge domains of NCDs were strengthened by the saltwater electron sink effect to repel chlorine and simultaneously a large number of electrons of NCDs were injected into copper as the electron reservoir based on energy-level matching, thereby avoiding Cu0 oxidization. Current works provide a guideline for exploring novel eco-friendly and highly efficient NCD corrosion inhibitor materials with antibacterial properties for safeguarding metals in seawater.

Recent advances in nanomaterials and their mechanisms for infected wounds management

Wounds infected by bacteria pose a considerable challenge in the field of healthcare, particularly with the increasing prevalence of antibiotic-resistant pathogens. Traditional antibiotics often fail to achieve effective results due to limited penetration, resistance development, and inadequate local concentration at wound sites. These limitations necessitate the exploration of alternative strategies that can overcome the drawbacks of conventional therapies. Nanomaterials have emerged as a promising solution for tackling bacterial infections and facilitating wound healing, thanks to their distinct physicochemical characteristics and multifunctional capabilities. This review highlights the latest developments in nanomaterials that demonstrated enhanced antibacterial efficacy and improved wound healing outcomes. The antibacterial mechanisms of nanomaterials are varied, including ion release, chemodynamic therapy, photothermal/photodynamic therapy, electrostatic interactions, and delivery of antibacterial drugs, which not only combat bacterial infections but also address the challenges posed by biofilms and antibiotic resistance. Furthermore, these nanomaterials create an optimal environment for tissue regeneration, promoting faster wound closure. By leveraging the unique attributes of nanomaterials, there is a significant opportunity to revolutionize the management of infected wounds and markedly improve patient outcomes.

"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.

Peroxidase-like copper-doped carbon-dots embedded in hydrogels for stimuli-responsive bacterial biofilm elimination and wound healing

Bacterial biofilms and their microenvironment are significant challenges that must be faced in the design of antibacterial drugs. Microenvironment-responsive mimetic peroxidases (POD) have been demonstrated to be an efficient solution to eliminating bacterial biofilms. However, they inevitably require additional H2O2 and/or acid due to the poor permeabilities towards biofilms. Herein, we report POD-like copper-doped carbon dots (named CuCD1) synthesized through a facile microwave-assisted carbonization manner. The characteristics of ultrasmall size (< 5 nm) and positive charge enabled it to possess good penetrability toward bacterial biofilm. As expected, CuCD1 showed great damage to bacteria due to the generation of hydroxyl radicals (•OH), which originated from the catalytic decomposition of endogenous H2O2 under a weak acid bacterial biofilm microenvironment. This highly increased oxidative stress resulted in the alteration of cell membrane permeability, subsequent cell death, and the final eradication of bacterial biofilm and the exposed bacteria. Moreover, to verify the practicality in vivo, CuCD1 was introduced to a routine hydrogel that was crosslinked by carboxymethyl chitosan (CMCS) and oxidized dextran (ODEX). In comparison with the control groups, the composite hydrogel, i.e., CuCD1-CMCS-ODEX revealed better antibacterial performance and thus accelerated wound healing and collagen disposition. This work would open opportunities to design CDs-based biofilm microenvironment-responsive antibacterial nanoagents. STATEMENT OF SIGNIFICANCE: (1) Ultrasmall size, positively charged, peroxidase (POD)-like CuCD1 were designed and harvested by a facile microwave-assisted carbonization method. (2) CuCD1 revealed a competitive in vitro antibacterial performance, good penetrability, and microenvironment-responsive clearing capacity towards bacterial biofilm. (3) By composing with CMCS-ODEX hydrogel, the composite hydrogel could continuously eliminate bacteria, promote wound healing, as well as collagen disposition. (4) This work would provide a new strategy in the design of CDs-based biofilm microenvironment-responsive antibacterial nano-agents.

Near-infrared Emission Carbon Dots Derived from Bromo-Substituted Perylene Derivatives with Simultaneously High Type I/II ROS Generation for Effective Bacterial Elimination and Tumor Ablation

Bacterial infections and tumor tissues are characterized by complex microenvironments with uneven oxygen availability. Effective photodynamic therapy for these conditions requires photosensitizers that can perform optimally within such environments, specifically by generating both type I and II reactive oxygen species (ROS) simultaneously. Carbon dots (CDs), a type of fluorescent nanomaterial smaller than 10 nm, are commonly used to treat bacterial infections and tumors. However, their current limitations, such as short maximum absorption and emission wavelengths, significantly restrict their therapeutic efficacy in deep tissues. In response to these challenges, a new type of fluorescent carbon dots with near-infrared (NIR) absorption and emission properties is reported, featuring a maximum emission peak beyond 700 nm (NIR-I region). These CDs offer strong tissue penetration and reduced tissue absorption advantages. Additionally, bromine atom doping significantly enhances the generation of type I and II ROS through efficient photodynamic processes. In vitro studies demonstrated their high photodynamic efficacy in antibacterial and antitumor applications. Ultimately, these findings translate into significant therapeutic effectiveness for treating skin infections and tumors in vivo. This study employs bromine-doped CDs nanomaterials, which demonstrate maximum fluorescence emission in the NIR region, to achieve efficient photodynamic treatment of bacterial infections and tumor ablation in complex microenvironments.

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.

Programmed Transformation of Osteogenesis Microenvironment by a Multifunctional Hydrogel to Enhance Repair of Infectious Bone Defects

Repair of infectious bone defects remains a serious problem in clinical practice owing to the high risk of infection and excessive reactive oxygen species (ROS) during the early stage, and the residual bacteria and delayed Osseo integrated interface in the later stage, which jointly creates a complex and dynamic microenvironment and leads to bone non-union. The melatonin carbon dots (MCDs) possess antibacterial and osteogenesis abilities, greatly simplifying the composition of a multifunctional material. Therefore, a multifunctional hydrogel containing MCDs (GH-MCD) is developed to meet the multi-stage and complex repair needs of infectious bone injury in this study. The GH-MCD can intelligently release MCDs responding to the acidic microenvironment to scavenge intracellular ROS and exhibit good antibacterial activity by inducing the production of ROS in bacteria and inhibiting the expression of secA2. Moreover, it has high osteogenesis and long-lasting antimicrobial activity during bone repair. RNA-seq results reveal that the hydrogels promote the repair of infected bone healing by enhancing cellular resistance to bacteria, balancing osteogenesis and osteoclastogenesis, and regulating the immune microenvironment. In conclusion, the GH-MCD can promote the repair of infectious bone defects through the programmed transformation of the microenvironment, providing a novel strategy for infectious bone defects.

Review of carbonaceous nanoparticles for antibacterial uses in various dental infections

The mouth cavity is the second most complex microbial community in the human body. It is composed of bacteria, viruses, fungi, and protozoa. An imbalance in the oral microbiota may lead to various conditions, including caries, soft tissue infections, periodontitis, root canal infections, peri-implantitis (PI), pulpitis, candidiasis, and denture stomatitis. Additionally, several locally administered antimicrobials have been suggested for dentistry in surgical and non-surgical applications. The main drawbacks are increased antimicrobial resistance, the risk of upsetting the natural microbiota, and hypersensitivity responses. Because of their unique physiochemical characteristics, nanoparticles (NPs) can circumvent antibiotic-resistance mechanisms and exert antimicrobial action via a variety of new bactericidal routes. Because of their anti-microbial properties, carbon-based NPs are becoming more and more effective antibacterial agents. Periodontitis, mouth infections, PI, dentin and root infections, and other dental diseases are among the conditions that may be treated using carbon NPs (CNPs) like graphene oxide and carbon dots. An outline of the scientific development of multifunctional CNPs concerning oral disorders will be given before talking about the significant influence of CNPs on dental health. Some of these illnesses include Periodontitis, oral infections, dental caries, dental pulp disorders, dentin and dental root infections, and PI. We also review the remaining research and application barriers for carbon-based NPs and possible future problems.

Phenylboronic acid-modified carbon dot-proteinase K nanohybrids for enhanced photodynamic therapy against bacterial biofilm infections

Nanohybrids combining phenylboronic acid-modified carbon dots (PCDs) and proteinase K have been engineered for addressing the formidable challenges of antimicrobial photodynamic therapy (aPDT) against bacterial biofilm infections, overcoming biofilm barrier obstruction, the limited diffusion of reactive oxygen species (ROS), and the inadequate ROS generation of traditional photosensitizers. PCDs are formulated for superior water solubility and robust singlet oxygen (1O2) production, mitigating issues related to dispersion and aggregation-induced quenching typical of conventional photosensitizers. The conjugation of phenylboronic acid to CDs not only enhanced 1O2 generation through increased electron-hole separation but also imparted strong bacterial binding capabilities to the PCDs, enabling broad-spectrum sterilization by maximizing the ROS-mediated bacterial destruction. Proteinase K, serving as a structural "glue", actively breaks down biofilms and facilitates the deep penetration of functional PCDs, aiding effective treatment of biofilm infections. In vivo studies confirm that PCDs-proteinase K nanohybrids dramatically accelerate healing in biofilm-infected wounds by synergizing enhanced photosensitization, potent bacterial adherence, and efficient biofilm elimination and penetration. This approach highlights a straightforward strategy to significantly advance aPDT, promoting the clinical adoption of non-antibiotic methods for combating bacterial biofilm infections. STATEMENT OF SIGNIFICANCE: 1) Phenylboronic acid-modified carbon dots (PCDs) were designed for enhanced water solubility and efficient singlet oxygen generation through surface modulation, also suggesting that surface modification can improve the inherent photosensitizing activity of CDs by promoting electron-hole separation; 2) The conjugation of phenylboronic acid endowed PCDs with strong bacterial binding capabilities, enabling highly efficient and broad-spectrum sterilization by maximizing reactive oxygen species-mediated bacterial destruction; 3) Incorporation of proteinase K (PK) leveraged its specific extracellular polymeric substance degrading capability, along with the stimuli-responsive release of PCDs from the PCDs-PK nanohybrids, facilitating biofilm breakdown and enabling deeper penetration of PCDs, thereby improving the treatment of biofilm infections.

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.

Functional modification and antibacterial evaluation of orthodontic adhesives with poly (lysine)-derived carbon dots

Fixed appliances used in orthodontic treatment make oral hygiene difficult to maintain, leading to bacterial adhesion around brackets and consequently resulting in white spot lesions (WSLs). After the bracket debonding, the residual adhesive is difficult to remove precisely due to its appearance similar to tooth enamel. In this study, we successfully synthesized small-sized and highly active PL-CDs by one-pot pyrolysis using ε-poly-l-lysine as a precursor. It was incorporated into orthodontic adhesives for multi-function modification. Based on our experimental results, the 3 wt% PL-CDs modified orthodontic adhesive exhibited excellent antibacterial properties and color identifiability. The addition of 3 wt% PL-CDs did not affect the biocompatibility and mechanical properties of the adhesive, and the cell survival rate was up to 80%. Therefore, this study provides a new strategy to solve the two major problems of enamel white spot and adhesive removal in the process of fixed orthodontics, and has important clinical application.

Hemoadhican Fiber Composite with Carbon Dots for Treating Severe Hemorrhage and Infected Wounds

Uncontrolled bleeding and infection following trauma continue to pose significant clinical challenges. This study employs hemoadhican (HD) polysaccharide, known for its superior hemostatic properties, as the foundational material to synthesize antibacterial carbon dots (H-CDs) through a hydrothermal method at various temperatures. The H-CDs exhibiting optimal antimicrobial properties were identified via in vitro antimicrobial characterization. The selected H-CDs possess nanoscale dimensions and a positive surface charge. They contain aldehyde groups and generate reactive oxygen species, which effectively eliminate bacteria. Subsequently, H-CDs were integrated into HD fibers (CDs-HD fibers) using a wet-spinning technique. The water vapor transmission rate, blood contact angle, and in vitro antimicrobial efficacy were evaluated. In a rat model of severe femoral artery hemorrhage and a noncompressible hepatic hemorrhage model, CDs-HD fibers demonstrated superior hemostatic performance compared to the commercially available QuikClot Combat Gauze. Furthermore, in a rat model of mixed bacterial wound infection, CDs-HD fibers significantly enhanced epithelial tissue remodeling and collagen deposition. In vivo studies confirmed the excellent biocompatibility of CDs-HD fibers. These findings suggest that CDs-HD fibers hold promise as a potential dressing for managing severe bleeding and preventing wound infections.

Gadolinium doped carbon dots for anti-gram-negative bacteria and visible light photodynamic enhancement of antibacterial effect

Infection with gram-negative bacteria is the main source of the most serious infectious pathogens. Developing new antibacterial materials that break through their external membranes and stay in the bacterial body to result in an antibacterial effect is the key to achieving high efficiency against Gram-negative bacteria. A Gd-doped carbon dot (GRCD) was prepared using the approved therapeutic diagnostic agents Rose Bengal (RB) and gadolinium ions (Gd3+), which was used to resist Gram-negative bacteria (e.g. E. coli, Escherichia coli). GRCD not only showed strong antibacterial activity by destroying the external membranes of E. coli (inhibition rate against E. coli was 92.0 % at 20 μg/mL) but also bound to E. coli DNA and generated single oxygen (1O2) (quantum yield was 0.50) through visible light-driven catalysis, thus decomposing the DNA of E. coli and further enhancing the antibacterial performance of GRCD. Under visible light conditions, the inhibition rate against E. coli reached 95.8 % at a low concentration of 2.5 μg/mL, without obvious cytotoxicity to NIH3T3 cells. The use of GRCD in treating wound infections in mice caused by E. coli was quite good, without side reactions on the mice's essential organs. In this study, a new approach has been provided to the design and synthesis of carbon dot nanocomposites for use against Gram-negative bacteria.

Super antioxidant and high antibacterial ability bi-functional xylitol/2-hydroxypropyl-β-cyclodextrin carbon dots with hydroxyl-functionalized for rainbow trout preservation

In 2020, Rainbow trout production reached 959,600 tons, representing 4 % of the global trout output. However, microbial contamination and lipid and protein oxidation spoil around 15 % of total aquatic products. Traditional food preservatives, used for their antibacterial or antioxidant properties, often fall short due to the disparity between the radical-scavenging ability of antioxidants and the ROS-generating capability of antimicrobial agents. This study developed bifunctional xylitol-based carbon dots (xβ-CDs) using 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), which exhibited both super antioxidant and high antibacterial activities. The incorporation of xylitol into xβ-CDs substantially enhanced their functional performance. The xβ-CDs displaying remarkable inhibition of DPPH (1-Diphenyl-2-trinitrophenylhydrazine), ABTS (2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate), and ·OH radicals (96.31 %, 99.74 %, and 99.72 %, respectively), rivaling the antioxidant capacity of vitamin C (VC). The xβ-CDs also effectively combated spoilage bacteria by compromising the cell wall and membrane integrity, reducing total protein, AKP, and ATP enzyme levels by 51.25 %, 70.08 %, and 57.80 %, respectively. Moreover, storage tests revealed that xβ-CDs extended the shelf life of Rainbow trout fillets by 3 days. These results indicate that xylitol/2-hydroxypropyl-β-cyclodextrin carbon dots offer a promising approach to preventing bacterial infections, protein oxidation, and lipid oxidation in rainbow trout.

Facile preparation of multifunctional biomaterials BTO/Ag and their applications in photoelectrochemical sensing, photodegradation and antibacterial activities

With the progress of modern technology and the diversification of societal demands, traditional materials with single properties can no longer meet the requirements of complex and constantly evolving application scenarios. To tackle intricate biomedical applications like disease diagnosis and treatment, scientists are focusing on exploring the design of novel multifunctional biomaterials that possess diverse activities. Bismuth titanate (Bi4Ti3O12, BTO), which has multifunctionality and great application potential, unfortunately suffers from inadequate photocatalytic performance. On the other hand, silver nanoparticles (Ag), known for their antibacterial properties, have relatively limited functions. In this study, we overcame these limitations by combining BTO with Ag to form a BTO/Ag biomultifunctional material. Our experiments showed that the addition of Ag effectively improved BTO's UV absorption ability, decreased electron transfer resistance, and increased carrier concentration. As a result, the photocatalytic performance of BTO/Ag was significantly enhanced, and its photoelectrochemical sensing and photodegradation capabilities were also greatly improved. Moreover, BTO served as an effective substrate, preventing Ag from agglomerating and maximizing its antibacterial potential. In specific performance evaluations, ascorbic acid and methylene blue (MB) were used to study the photoelectrochemical sensing and photodegradation capabilities respectively, while Escherichia coli and Staphylococcus aureus were chosen as test organisms to assess the antibacterial properties. All in all, this research has yielded promising results.

Tea Polyphenol-Derived Carbon Dots Alleviate Abdominal Aortic Aneurysm Progression by Mitigating Oxidative Stress and Ferroptosis

Abdominal aortic aneurysm (AAA) is a cardiovascular disease with potentially fatal consequences, yet effective therapies to prevent its progression remain unavailable. Oxidative stress is associated with AAA development. Carbon dots have reactive oxygen species-scavenging activity, while green tea extract exhibits robust antioxidant properties. However, the potential of green tea derived carbon dots in mitigating AAA progression has not been fully elucidated. In this study, tea polyphenol carbon dots (TP-CDs) were synthesized via hydrothermal methods and characterized for their antioxidant properties. The antioxidant effects of TP-CDs were evaluated, and TP-CDs' impact on phenotypic transformation, oxidative stress, apoptosis and ferroptosis was investigated comprehensively in an Ang II-induced AAA model, employing techniques such as Western blotting, flow cytometry, and immunohistochemistry. The results revealed that TP-CDs effectively alleviated oxidative stress induced by Ang II stimulation, thereby inhibiting phenotypic transformation, apoptosis, and ferroptosis in vivo. Furthermore, treatment with TP-CDs significantly attenuated AAA progression in a mouse AAA model. Overall, these findings demonstrate that TP-CDs reduced reactive oxygen species levels in the microenvironment and alleviated the progression of AAA, offering a promising therapeutic strategy for this condition.

Advances in the synthesis and properties of sulfur quantum dots for food safety detection and antibacterial applications

Food safety is closely related to human health and has become a worldwide, pressing concern. Food safety analysis is essential for ensuring food safety. Sulfur quantum dots (SQDs), a new type of zero-dimensional metal-free nanomaterials, have recently become the focus of scientific research due to their good luminescence properties, dispersibility, biocompatibility, and inherent antibacterial properties. This review focuses on recent advances in SQDs, with emphasis on their practical applications in the food field. First, commonly used methods for the synthesis of SQDs are presented, including traditional and emerging strategies. The properties of SQDs are then analyzed in detail, particularly their luminescence properties, catalytic activities, and reducing properties. Next, the use of SQDs in food safety detection and antibacterial fields are elaborated. Finally, this review discusses the challenges associated with the use of SQDs in food safety detection and antimicrobial applications.

Construction of a one-stop N-doped negatively charged carbon dot nanoplatform with antibacterial and anti-inflammatory dual activities for wound infection based on biocompatibility

The development of bacterial resistance significantly contributes to the persistence of infections. Although previous studies have highlighted the benefits of metal-doped positive carbon nanodots in managing bacterial wound infections, their mechanism of action is relatively simple and they may pose potential hazards to human cells. Therefore, it is essential to develop a one-stop carbon dot nanoplatform that offers high biocompatibility, antibacterial properties, and anti-inflammatory activities for wound infection management. This study explores the antibacterial efficacy, without detectable resistance, and wound-healing potential of nitrogen-doped (N-doped) negatively charged carbon dots (TPP-CDs). These carbon dots are synthesized using tannic acid (TA), polyethylene polyamine, and polyethylene glycol (PEG) as precursors, with a focus on their biocompatibility. Numerous systematic studies have shown that TPP-CDs can effectively destroy bacterial biofilms and deoxyribonucleic acid (DNA), while also inducing oxidative stress, leading to a potent antimicrobial effect. TPP-CDs also demonstrate the ability to scavenge excess free radicals, promote cellular proliferation, and inhibit inflammatory factors, all of which contribute to improved wound healing. TPP-CDs also demonstrate favorable cell imaging capabilities. These findings suggest that N-doped negatively charged TPP-CDs hold significant potential for treating bacterial infections and offer practical insights for their application in the medical field.

Carboxyl-functionalized multifunctional red-emitting carbon quantum dots as an ideal biomaterial

Carbon quantum dots (CQDs) have been developed into a popular nanomaterial due to their abundant surface state, good biocompatibility, and excellent antimicrobial properties. However, CQDs with multiple functions, such as being red-emitting, having good antibacterial activity, and having excellent pH sensitivity, have rarely been reported. In this work, red-emitting CQDs (R-CQDs) with excellent optical properties and antimicrobial activity were prepared by a simple green hydrothermal method. In antimicrobial applications, the R-CQDs featured good antibacterial activity due to the generation of reactive oxygen species, indicating excellent photodynamic antimicrobial ability. In addition, the R-CQDs showed fine pH sensitivity, giving them potential as pH sensors to monitor the pH of wounds in real time. The promising potential application of R-CQDs for cell imaging was also demonstrated. In summary, we offer R-CQDs with good antibacterial and pH sensitivity as a potential nanomaterial for pH and antimicrobial monitoring of wounds, shedding light on the biomedical field.

Antimicrobial and Remineralization of Carboxymethyl Chitosan and Xylitol Functionalized Carbon Dots Coating on Orthodontic Brackets

Purpose

During fixed orthodontic treatment, oral hygiene is difficult to ensure and can easily lead to an imbalance in the oral micro-ecological balance. In this study, based on the adhesive properties of polydopamine (PDA) and the good antimicrobial and remineralization properties of carboxymethyl chitosan (CMC) and xylitol (Xy), new nanocomposites with both antimicrobial and remineralization capabilities were prepared to coat on orthodontic brackets.

Methods

Composite carbon dots (CDs) were synthesized using carboxymethyl chitosan and xylitol, we characterized them and the antimicrobial properties of the CMC-Xy-CDs were investigated by co-cultivation with S. mutans in vitro and in vivo. The composite coating was then adhered to the brackets. After the characterization measurements, antibacterial properties against S. mutans and the ability to promote remineralization of isolated teeth were investigated.

Results

Biological studies demonstrated that L929 cells co-cultured with CMC-Xy-CDs did not observe significant cytotoxicity and CMC-Xy-CDs have good biocompatibility. In the adhesive action of PDA, various characterizations have proved that CDs are modified on the brackets surface. In the antibacterial experiment, CMC-Xy-CDs and the adhesive coating on the brackets were found to have better antibacterial performance than the control group, with an antibacterial rate of up to 80%. In the animal experiment, the results of CMC-Xy-CDs promoting the healing of S. mutans infection wound models showed that there was a significant difference at 7d (P < 0.001), indicating that the experimental group had good antibacterial effects. The SEM of teeth after CMC-Xy-CDs promoted remineralization showed that the structure of the tooth surface became dense and some precipitation appeared, and the surface hardness measurement was significantly increased (p<0.0001).

Conclusion

Our study revealed that new nanocomposites with both antimicrobial and remineralization capabilities coated on orthodontic brackets provide a good basis for future clinical applications.

Carbon dots for efficient detection of water content in organic solvents

The trace amount of water in organic solvents can affect the progress of chemical reactions, which will adversely affect chemical production in many industries, resulting in a doubling of costs. In this work, carbon dots (CDs) with abundant polar groups were synthesized by a simple one-step hydrothermal method. The prepared CDs showed superior dispersibility and fluorescence performance compared to the CDs that have been reported for the detection of water content in organic solvents. It can realize the fluorescence detection of trace water in several water-soluble organic solvents such as N,N-dimethylformamide, ethanol and methanol with wide linear range (0 %-100 %) and high sensitivity. This will provide a powerful tool for the rapid detection of water content in organic solvents in chemical production.

Guanidinium-Functionalized Carbon Dots: An Efficient Antibacterial Agent against Multidrug-Resistant ESKAPE Pathogens

The rise of multidrug-resistant (MDR) bacteria poses a substantial challenge in clinical settings, particularly with the increasing prevalence of ESKAPE pathogens (E. faecium, S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, and E. coli) as critical MDR bacteria. These ESKAPE pathogens have the capability to undermine antibiotic treatments, leading to a high incidence of drug resistance. However, the development of efficient antibacterial agents against ESKAPE pathogens is still in the bottleneck. Herein, the first example of antibacterial carbon dots against ESKAPE pathogens was reported. Onion powder-based carbon dots were melted with poly(hexamethylene biguanide) hydrochloride (PHMB) to obtain guanidinium-functionalized carbon dots (GCDs), which exhibited satisfactory antibacterial activity against all the tested bacteria, including both Gram-positive and Gram-negative bacteria, and even ESKAPE pathogens. The efficient antibacterial ability of GCDs derives from the rupture of the bacterial cell membrane and elevated ROS levels. Safety assessments revealed that GCDs neither trigger detectable drug resistance nor exhibit any cytotoxic effects. Furthermore, GCDs effectively promoted wound healing without observable adverse reactions of mixed MDR bacteria-infected wounds in rats. The GCDs also showed excellent long-term stability. These findings indicate that GCDs hold promise as an efficient antibacterial agent for the treatment of MDR strain-caused clinical infected-wound healing.

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

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

Hectogram-Scale Synthesis of Visible Light Excitable Room Temperature Phosphorescence Carbon Dots

Carbon dots (CDs) based room temperature phosphorescence (RTP) materials can be prepared via facile procedures and exhibit excellent photostability and biocompatibility. Furthermore, doping of hetero-atoms into CDs can afford multiple triplet levels. The RTP emission generated from the resultant CDs always displays outstanding dynamic behaviors and even can be efficiently excited by visible light. Given this, CDs-based RTP materials not only can be used for anti-counterfeiting but also exhibit great application potential in signage and illumination fields. In this contribution, a type of B, N, and P co-doped CDs are prepared in hectogram scale. Upon excitation by UV lamp and white LED, the obtained CDs emit green and yellow RTP, respectively, the lifetime of which are 851 and 481 ms, respectively. It is found that the luminescence color of the CDs can be further tuned. By controlling the degree of carbonization, the RTP color of the CDs can be facilely tuned from green to orange-red. Based on an energy transfer strategy, the luminescence color can be further tuned to red. Benefited from the dynamic and visible-excited colorful RTP emission, the application of these obtained CDs in anti-counterfeiting, fingerprint collection, and luminescent traffic signage are also explored.

Carbon Dots with Integrated Photothermal Antibacterial and Heat-Enhanced Antioxidant Properties for Diabetic Wound Healing

Diabetic wounds pose a persistent challenge due to their slow healing nature, primarily caused by bacterial infection and excessive reactive oxygen species (ROS)-induced inflammation. In this study, carbon dots with synergistic antibacterial and antioxidant properties, referred to as AA-CDs, are developed specifically for diabetic wound healing using a straightforward solvothermal method. By utilizing cost-effective precursors like citric acid and ascorbic acid, AA-CDs are engineered to possess tailored functions of photothermal sterilization and ROS scavenging. The resulting AA-CDs demonstrats broad-spectrum antibacterial activity, particularly against multidrug-resistant strains, along with efficient ROS scavenging both in solution and within cells. Additionally, AA-CDs exhibits a protective effect against oxidative stress-induced damage. Notably, with a high photothermal conversion efficiency (41.18%), AA-CDs displays heat-enhanced antioxidant performance, providing not only augmented ROS scavenging but also additional protection against oxidative stress, yielding a true "1 + 1 > 2" effect. To facilitate their use in vivo, AA-CDs are incorporated into a thermally responsive hydrogel, which exhibits evident anti-inflammatory properties by modulating inflammatory factors and significantly promots the healing of diabetic wounds. This study underscores the value of integrated platforms for diabetic wound healing and highlights the potential of versatile CDs as promising therapeutic agents in biomedical applications.

Carbon-Dots-Mediated Improvement of Antimicrobial Activity of Natural Products

The development of new microbicidal compounds has become a top priority due to the emergence and spread of drug-resistant pathogenic microbes. In this study, blue-emitting and positively charged carbon dots (CDs), called Du-CDs, were fabricated for the first time utilizing the natural product extract of endophyte Diaporthe unshiuensis YSP3 as raw material through a one-step solvothermal method, which possessed varied functional groups including amino, carboxyl, hydroxyl, and sulfite groups. Interestingly, Du-CDs exhibited notably enhanced antimicrobial activities toward both bacteria and fungi as compared to the natural product extract of YSP3, with low minimum inhibitory concentrations. Moreover, Du-CDs significantly inhibited the formation of biofilms. Du-CDs bound with the microbial cell surface via electronic interaction or hydrophobic interaction entered the microbial cells and were distributed fully inside the cells. Du-CDs caused cell membrane damage and/or cell division cycle interruption, resulting in microbial cell death. Moreover, Du-CDs exhibited an improved antimicrobial effect and accelerated wound healing ability with good biocompatibility in the mouse model. Overall, we demonstrate that the formation of CDs from fungal natural products presents a promising and potential means to develop novel antimicrobial agents with great fluorescence, improved microbiocidal effect and wound healing capacity, and good biosafety for combating microbial infections.

Carbon Quantum Dot-Functionalized Dermis-Derived Transparent Electronic Skin for Multimodal Human Motion Signal Monitoring and Construction of Self-Powered Triboelectric Nanogenerator

Electronic skin (e-skin) is considered as a highly promising interface for human-computer interaction systems and wearable electronic devices. Through elaborate design and assembly of various materials, it possesses multiple characteristics similar to human skin, including remarkable flexibility, stretchability, sensitivity to temperature and humidity, biocompatibility, and efficient interfacial ion/electron transport capabilities. Here, we innovatively integrate multifunctional carbon quantum dots (CQDs), which exhibit conductivity, antibacterial properties, ultraviolet absorption, and fluorescence emission, with poly(acrylic acid) and glycerin (Gly) into a three-dimensional network structure of natural goatskin collagen fibers. Through a top-down design strategy enhanced by hydrogen bond reconstruction, we successfully fabricated a novel transparent e-skin (PAC-eSkin). This e-skin exhibited significant tensile properties (4.94 MPa of tensile strength and 263.42% of a maximum breaking elongation), while also possessing Young's modulus similar to human skin (2.32 MPa). It is noteworthy that the functionalized CQDs used was derived from discarded goat hair, and the addition of Gly gave PAC-eSkin excellent antifreezing and moisturizing properties. Due to the presence of ultrasmall CQDs, which creates efficient ion/electron transport channels within PAC-eSkin, it could rapidly sense human motion and physiological signals (with a gauge factor (GF) of 1.88). Furthermore, PAC-eSkin had the potential to replace traditional electrode patches for real-time monitoring of electrocardiogram, electromyogram, and electrooculogram signals, with a higher SNR (signal-to-noise ratio) of 25.1 dB. Additionally, the customizable size and shape of PAC-eSkin offer vast possibilities for the construction of single-electrode triboelectric nanogenerator systems. We have reason to believe that the design and development of this transparent e-skin based on CQDs-functionalized dermal collagen matrices can pave a new way for innovations in human-computer interaction interfaces and their sensing application in diverse scenarios.

Carbon Dots-Inked Paper with Single/Two-Photon Excited Dual-Mode Thermochromic Afterglow for Advanced Dynamic Information Encryption

Achieving thermochromic afterglow (TCAG) in a single material for advanced information encryption remains a significant challenge. Herein, TCAG in carbon dots (CDs)-inked paper (CDs@Paper) is achieved by tuning the temperature-dependent dual-mode afterglow of room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF). The CDs are synthesized through thermal treatment of levofloxacin in melting boric acid with postpurification via dialysis. CDs@Paper exhibit both TCAG and excitation-dependent afterglow color properties. The TCAG of CDs@Paper exhibits dynamic color changes from blue at high temperatures to yellow at low temperatures by adjusting the proportion of the temperature-dependent TADF and phosphorescence. Notably, two-photon afterglow in CDs-based afterglow materials and time-dependent two-photon afterglow colors are achieved for the first time. Moreover, leveraging the opposite emission responses of phosphorescence and TADF to temperature, CDs@Paper demonstrate TCAG with temperature-sensing capabilities across a wide temperature range. Furthermore, a CDs@Paper-based 3D code containing color and temperature information is successfully developed for advanced dynamic information encryption.

Dynamic Directional Ultrasonically In Situ-Generated N,S-Codoped Carbon Dots in Poly(ethylene glycol) for Improved Tribological Performance

The dispersion stability of nanomaterials in lubricants significantly influences tribological performance, yet their addition as lubricant additives often presents challenges in secondary dispersion. Here, we present a straightforward method for in situ preparation of N,S-codoped CDs (N,S-CDs)-based lubricants using heterocyclic aromatic hydrocarbons containing N/S elements in poly(ethylene glycol) (PEG) base oil by a directional ultrasound strategy. Two types of N,S-CDs were successfully prepared via the directional ultrasound treatment of PEG with benzothiazole (BTA) and benzothiadiazole (BTH) separately. The resultant N,S-CDs have a uniform distribution of N and S elements and maintain good colloidal dispersion stability in PEG even after 9 months of storage. The N,S-CDs can enter the surface gap of the friction pairs and then induce a tribochemical reaction. Benefiting from the synergistic effect of N and S activating elements, a robust and stable protective film consisting of iron sulfides, iron oxides, carbon nitrides, and amorphous carbonaceous compounds is formed, thus endowing N,S-CDs-based lubricants with improved antiwear and friction-reducing performance. Compared with pure PEG, the coefficient of friction (COF) of the N,S-CDs(BTH)-based lubricant decreased to 0.108 from 0.292, accompanied by a 91.2% reduction in wear volume, and the maximum load carrying capacity increased to 450 from 150 N.

An ultrasensitive smartphone-assisted bicolor-ratiometric fluorescence sensing platform based on a "noise purifier" for point-of-care testing of pathogenic bacteria in food

Non-specific binding in fluorescence resonance energy transfer (FRET) remains a challenge in foodborne pathogen detection, resulting in interference of high background signals. Herein, we innovatively reported a dual-mode FRET sensor based on a "noise purifier" for the ultrasensitive quantification of Escherichia coli O157:H7 in food. An efficient FRET system was constructed with polymyxin B-modified nitrogen-sulfur co-doped graphene quantum dots (N, S-GQDs@PMB) as donors and aptamer-modified yellow carbon dots (Y-CDs@Apt) as acceptors. Magnetic multi-walled carbon nanotubes (Fe@MWCNTs) were employed as a "noise purifier" to reduce the interference of the fluorescence background. Under the background purification mode, the sensitivity of the dual-mode signals of the FRET sensor has increased by an order of magnitude. Additionally, smartphone-assisted colorimetric analysis enabled point-of-care detection of E. coli O157:H7 in real samples. The developed sensing platform based on a "noise purifier" provides a promising method for ultrasensitive on-site testing of trace pathogenic bacteria in various foodstuffs.

Carbon Dot-Loaded Apoptotic Vesicles Improve the Liver Kupffer Cell-Mediated Antibacterial Effect to Synergistically Alleviate Sepsis

Sepsis is a lethal systemic inflammatory disease against infection that lacks effective therapeutic approaches. Liver resident macrophage Kupffer cell (KC)-initiated bacterial clearance is crucial for the host to defend against infection. However, it remains unclear whether this process also governs the antibacterial therapy of sepsis that would be used to improve therapeutic outcomes. Here, we found that copper-doped carbon dots (Cu-CDs) exhibited superior antibacterial capabilities in vitro but displayed limited therapeutic effects in septic mice due to their limited ability to target the liver and restore KC antimicrobial capacity. Thus, we developed a composite nanodrug of copper-doped carbon dot-loaded apoVs (CC-apoVs) that combined the antibacterial ability of Cu-CDs and liver KC targeting features of apoV. Moreover, intravenous injection of CC-apoVs markedly alleviated the systemic infection and decreased the mortality of septic mice compared to Cu-CD and apoV infusion alone. Mechanistically, CC-apoV injection rescued impaired liver KCs during sepsis and enhanced their ability to capture and kill bloodborne bacteria. In addition, apoV-promoted macrophage killing of bacteria could be blocked by the inhibition of small GTPase Rab5. This study reveals a liver KC-targeted therapeutic strategy for sepsis and provides a nanodrug CC-apoV to improve the host antibacterial defense and amplify the therapeutic effect of the nanodrug.

Design and Fabrication of Broad-Spectrum Antimicrobial Porous Metallo-Polymeric Microsphere for Water Disinfection

An expedient and efficient approach is used to synthesize a new class of metallo-polymeric microspheres (MPMs) as antimicrobials to succumb the wide range of bacteria from water. Three types of MPMs, that is, poly[Silver (I)-methacrylate-co-methylmethacrylate] (pAgMA), poly[Copper (II)-methacrylate-co-methyl methacrylate] (pCuMA), and poly[Nickel (II)-methacrylate-co-methylmethacrylate] (pNiMA), are prepared via radical suspension polymerization technique in 3D shape with porous texture. The structural and morphological characterization of the prepared microspheres are examined by analytical techniques. The antimicrobial potentialities of prepared MPMs are investigated at the laboratory scale study, revealing that the MPMs exhibit strong antibacterial activity (≈99.9% killing) against Gram-negative and Gram-positive bacteria [Enterobacter hormaechei (EH), Bacillus megatarium (BM), and Bacillus bataviensis (BB)]. The MacConkey agar medium test reveals that MPMs have substantial biocidal efficacy against broad-spectrum Gram-negative bacteria present in tap water. The MPMs exhibit significant antimicrobial efficacy via contact killing owe to the presence of integrated biocidal metal moiety, which represents that the MPMs are safe for water disinfection.

Comprehensive Overview of Controlled Fabrication of Multifunctional Fluorescent Carbon Quantum Dots and Exploring Applications

In recent years, carbon dots (CDs) have garnered increasing attention due to their simple preparation methods, versatile performances, and wide-ranging applications. CDs can manifest various optical, physical, and chemical properties including quantum yield (QY), emission wavelength (Em), solid-state fluorescence (SSF), room-temperature phosphorescence (RTP), material-specific responsivity, pH sensitivity, anti-oxidation and oxidation, and biocompatibility. These properties can be effectively regulated through precise control of the CD preparation process, rendering them suitable for diverse applications. However, the lack of consideration given to the precise control of each feature of CDs during the preparation process poses a challenge in obtaining the requisite features for various applications. This paper is to analyze existing research and present novel concepts and ideas for creating CDs with different distinct features and applications. The synthesis methods of CDs are discussed in the first section, followed by a comprehensive overview of the important properties of CDs and the modification strategy. Subsequently, the application of CDs and their requisite properties are reviewed. Finally, the paper outlines the current challenges in controlling CDs properties and their applications, discusses potential solutions, and offers suggestions for future research.

Multi-step strategies for synergistic treatment of urinary tract infections based on D-xylose-decorated antimicrobial peptide carbon dots

Urinary tract infections (UTIs) caused by Uropathogenic Escherichia coli (UPEC), often reoccur due to the formation of intracellular bacterial colonies (IBCs) and antibiotic resistance. Given the significance of YadC for UPEC infection in our previous study, we developed D-xylose-decorated ɛ-poly-L-lysine (εPL)-based carbon dots (D-xyl@εPLCDs) that can be traced, and employed multi-step approaches to elucidate the functional roles of D-xyl@εPLCDs in UPEC infection. Compared to undecorated particles, D-xyl@εPLCDs demonstrate YadC-dependent bacterial targeting and exhibit enhanced bactericidal activities both intracellularly and extracellularly. Moreover, pre-treatment of D-xyl@εPLCDs before infection blocked the subsequent adhesion and invasion of UPEC to bladder epithelial cells 5637. Increase of ROS production and innate immune responses were observed in bladder epithelial cells 5637 treated with D-xyl@εPLCDs. In addition, treatment of D-xyl@εPLCDs post-infection facilitated clearance of UPEC in the bladders of the UTI mouse model, and reduced ultimate number of neutrophils, macrophages and inflammatory responses raised by invaded bacteria. Collectively, we presented a comprehensive evaluating system to show that D-xyl@εPLCDs exhibits superior bactericidal effects against UPEC, making them a promising candidate for drug development in clinical UTI therapeutics.

Semiconducting polymer dots for multifunctional integrated nanomedicine carriers

The expansion applications of semiconducting polymer dots (Pdots) among optical nanomaterial field have long posed a challenge for researchers, promoting their intelligent application in multifunctional nano-imaging systems and integrated nanomedicine carriers for diagnosis and treatment. Despite notable progress, several inadequacies still persist in the field of Pdots, including the development of simplified near-infrared (NIR) optical nanoprobes, elucidation of their inherent biological behavior, and integration of information processing and nanotechnology into biomedical applications. This review aims to comprehensively elucidate the current status of Pdots as a classical nanophotonic material by discussing its advantages and limitations in terms of biocompatibility, adaptability to microenvironments in vivo, etc. Multifunctional integration and surface chemistry play crucial roles in realizing the intelligent application of Pdots. Information visualization based on their optical and physicochemical properties is pivotal for achieving detection, sensing, and labeling probes. Therefore, we have refined the underlying mechanisms and constructed multiple comprehensive original mechanism summaries to establish a benchmark. Additionally, we have explored the cross-linking interactions between Pdots and nanomedicine, potential yet complete biological metabolic pathways, future research directions, and innovative solutions for integrating diagnosis and treatment strategies. This review presents the possible expectations and valuable insights for advancing Pdots, specifically from chemical, medical, and photophysical practitioners' standpoints.

Green synthesis of N-rich carbon dot-derived crosslinked covalent organic nanomaterial for multipurpose chromatographic applications

Carbon dots (CDs) derived crosslinked covalent organic nanomaterials (CONs) possessing high specific surface area and abundant surface functional groups are considered to be potential candidates for multimodal chromatographic separations. Typically, the synthesis of CDs and CONs requires harsh reaction conditions and toxic organic solvents, hence, the pursuit of facile and mild preparation strategies is the goal of researchers. In this work, 3-aminopropyltriethoxysilane and D-glucose were used as nitrogen and carbon sources, respectively, to prepare amino-CDs (AmCDs) by rapid low-temperature polymerization rather than the common high-temperature and high-pressure reaction. Then, surface functionalization of the aminated silica gel was carried out in a deep eutectic solvent by using hydrophilic AmCDs and 1,3,5-triformylbenzene (TFB) as the functional monomers. Consequently, a novel N-rich CDs derived CON surface-functionalized silica gel (AmCDs-CON@SiO2) was obtained under mild reaction conditions. The combination of AmCDs and TFB created an ideal CON based chromatographic stationary phase. The incorporation of TFB not only contributed to the successful construction of a crosslinked CON, but also enhanced the interaction forces. The developed AmCDs-CON@SiO2 has a great potential for versatile applications in liquid chromatography. This study proposes a simple stationary phase preparation strategy by the surface modification of silica gel with CDs-based CON. Moreover, this study verified the application potential of CDs derived CON in chromatographic separation. This not only promotes the development of CDs in the field of liquid chromatographic stationary phase, but also provides some reference value for the wide application of cross-linked CON.

Biofilm Inhibition on Medical Devices and Implants Using Carbon Dots: An Updated Review

Biofilms are an intricate community of microbes that colonize solid surfaces, communicating via a quorum-sensing mechanism. These microbial aggregates secrete exopolysaccharides facilitating adhesion and conferring resistance to drugs and antimicrobial agents. The escalating global concern over biofilm-related infections on medical devices underscores the severe threat to human health. Carbon dots (CDs) have emerged as a promising substrate to combat microbes and disrupt biofilm matrices. Their numerous advantages such as facile surface functionalization and specific antimicrobial properties, position them as innovative anti-biofilm agents. Due to their minuscule size, CDs can penetrate microbial cells, inhibiting growth via cytoplasmic leakage, reactive oxygen species (ROS) generation, and genetic material fragmentation. Research has demonstrated the efficacy of CDs in inhibiting biofilms formed by key pathogenic bacteria such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Consequently, the development of CD-based coatings and hydrogels holds promise for eradicating biofilm formation, thereby enhancing treatment efficacy, reducing clinical expenses, and minimizing the need for implant revision surgeries. This review provides insights into the mechanisms of biofilm formation on implants, surveys major biofilm-forming pathogens and associated infections, and specifically highlights the anti-biofilm properties of CDs emphasizing their potential as coatings on medical implants.

Shining light on carbon dots: Toward enhanced antibacterial activity for biofilm disruption

In spite of tremendous efforts dedicated to addressing bacterial infections and biofilm formation, the post-antibiotic ear continues to witness a gap between the established materials and an easily accessible yet biocompatible antibacterial reagent. Here we show carbon dots (CDs) synthesized via a single hydrothermal process can afford promising antibacterial activity that can be further enhanced by exposure to light. By using citric acid and polyethyleneimine as the precursors, the photoluminescence CDs can be produced within a one-pot, one-step hydrothermal reaction in only 2 h. The CDs demonstrate robust antibacterial properties against both Gram-positive and Gram-negative bacteria and, notably, a considerable enhancement of antibacterial effect can be observed upon photo-irradiation. Mechanistic insights reveal that the CDs generate singlet oxygen (1O2) when exposed to light, leading to an augmented reactive oxygen species level. The approach for disruption of biofilms and inhibition of biofilm formation by using the CDs has also been established. Our findings present a potential solution to combat antibacterial resistance and offer a path to reduce dependence on traditional antibiotics.

Carrageenan/polyvinyl alcohol composite film reinforced with spermidine carbon dots: An active packaging material with dual-mode antibacterial activity

Exploring biopolymer-based antibacterial packaging materials is promising to tackle the issues caused by petroleum plastic pollution and microbial contamination. Herein, a novel packaging material with two antibacterial modes, continuous and efficient, is constructed by dispersing positively charged spermidine carbon dots (Spd-CDs) in a carrageenan/polyvinyl alcohol (CP) composite biopolymer. The obtained nanocomposite film (CP/CDs film) not only gradually releases the ultra-small Spd-CDs but also rapidly generates reactive oxygen species to inhibit the reproduction of E. coli and S. aureus. Benefiting from the complementary advantages of carrageenan and polyvinyl alcohol, as well as the addition of Spd-CDs, the CP/CDs films exhibit high transparency, good mechanical performance, water vapor barrier ability, low migration, etc. The CP/CDs film as a packaging material is validated to be effective in preventing microbial contamination of pork samples. Our prepared nanocomposite film with sustainability and efficient antibacterial properties is expected as food active packaging.

Catalytic Nanodots-Driven Pyroptosis Suppression in Nucleus Pulposus for Antioxidant Intervention of Intervertebral Disc Degeneration

Low back pain resulting from intervertebral disc degeneration (IVDD) is a prevalent global concern; however, its underlying mechanism remains elusive. Single-cell sequencing analyses revealed the critical involvement of pyroptosis in IVDD. Considering the involvement of reactive oxygen species (ROS) as the primary instigator of pyroptosis and the lack of an efficient intervention approach, this study developed carbonized Mn-containing nanodots (MCDs) as ROS-scavenging catalytic biomaterials to suppress pyroptosis of nucleus pulposus (NP) cells to efficiently alleviate IVDD. Catalytic MCDs have superior efficacy in scavenging intracellular ROS and rescuing homeostasis in the NP microenvironment compared with N-acetylcysteine, a classical antioxidant. The data validates that pyroptosis plays a vital role in mediating the protective effects of catalytic MCDs against oxidative stress. Systematic in vivo assessments substantiate the effectiveness of MCDs in rescuing a puncture-induced IVDD rat model, further demonstrating their ability to suppress pyroptosis. This study highlights the potential of antioxidant catalytic nanomedicine as a pyroptosis inhibitor and mechanistically unveils an efficient strategy for the treatment of IVDD.

Biophilic Positive Carbon Dot Exerts Antifungal Activity and Augments Corneal Permeation for Fungal Keratitis

Fungal keratitis (FK) is an infectious eye disease that poses a significant risk of blindness. However, the effectiveness of conventional antifungal drugs is limited due to the intrinsic ocular barrier that impedes drug absorption. There is an urgent need to develop new therapeutic strategies to effectively combat FK. Herein, we synthesized an ultrasmall positively charged carbon dot using a simple stage-melting method. The carbon dot can penetrate the corneal barrier by opening the tight junctions, allowing them to reach the lesion site and effectively kill the fungi. The results both in vitro and in vivo demonstrated that it exhibited good biocompatibility and antifungal activity, significantly improving the therapeutic effect in a mouse model of FK. Therefore, this biophilic ultrasmall size and positive carbon dot, characterized by its ability to penetrate the corneal barrier and its antifungal properties, may offer valuable insights into the design of effective ocular nanomedicines.