Highly fluorescent N, F co-doped carbon dots with tunable light emission for multicolor bio-labeling and antibacterial applications

Green synthesis of carbon dots and their application as fluorescent probes for rutin detection

Rutin has antioxidant, antitumor, antibacterial, antiviral, anti-aging, and analgesic effects, and it is a drug used to treat various circulatory disorders. However, rutin overdosage can seriously harm the health. The rutin detection method has drawbacks, including expensive costs, low sensitivity, and complicated steps. Therefore, given that carbon dots have superior fluorescence characteristics, the development of nanofluorescent probes for rutin detection is the research motivation of this article. N-CDs and N, B-CDs were produced by a hydrothermal approach using o-phenylenediamine, glucose, urea, and boron oxide, commonly available in the laboratory. The morphology and composition of CDs have been analyzed. According to the findings, the surfaces of the N-CDs and N, B-CDs were abundant in functional groups that contained oxygen, and they were spherical, uniform in size, and well distributed, which is beneficial for enhancing its fluorescence response to the detection object. In addition, two kinds of CDs emit bright yellow and blue-green fluorescence under the ultraviolet lamp at 365 nm. Rutin was detected in solution using synthesized N-CDs and N, B-CDs as fluorescent probes. Rutin was discovered to have a fluorescence quenching effect on N-CDs and N, B-CDs. Within a specific concentration range, the N-CDs and N, B-CDs fluorescence intensities demonstrated an excellent linear relationship with the rutin concentration, and the corresponding correlation coefficients R2 were 0.9897 and 0.9409, respectively. To verify the detection accuracy of the experiment, we used the random forest algorithm to predict the detection model. The results showed that the experimental and predicted values were coincident, suggesting the possibility of using N-CDs and N, B-CDs as fluorescent probes to detect rutin. This work offers experimental procedures and data references to create doping CDs with superior fluorescence qualities. It broadens the use of doped CDs in the detection of rutin.

Fluorescent Sodium Alginate Hydrogel-Carbon Dots Sensor for Detecting Perfluorooctanoic Acid in Potable Water

Per- and polyfluoroalkyl substances (PFASs), especially perfluorooctanoic acid (PFOA), are emerging environmental and health concerns due to their persistence, resistance to degradation, and bioaccumulation. In this study, we developed a sensitive and selective detection platform based on a sodium alginate (SA) hydrogel modified with nitrogen and fluorinated carbon dots (N,F-CDs) to enhance the detection of PFOA in natural and engineered water systems. The SA hydrogel-N,F-CD composite exhibited strong fluorescence at 480 nm after optimization, achieving a detection limit as low as 0.001 ppt. The sensor was characterized by using Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FT-IR), Powder X-ray Diffraction (PXRD), X-ray Photoelectron Spectroscopy (XPS), and zeta potential spectroscopy, revealing its structural integrity, functional groups, and the surface charge of the SA hydrogel-N,F-CDs network. Sensitivity assessments demonstrated a linear fluorescence response to PFOA concentrations ranging from 1 to 66 ppq. Selectivity tests confirmed the sensor's ability to distinguish PFOA from other perfluorinated compounds, with minimal interference from other substances. The practical applicability of the sensor was validated using spiked recovery experiments with tap water samples from various locations, achieving recovery rates between 94% and 106.6%. This sensor offers a reliable, efficient, and highly sensitive platform for the detection of PFAS, demonstrating its potential for real-world PFAS-monitoring applications.

Ratio fluorescence and smartphone-assisted colorimetry dual-mode detection of creatinine based on F, B, N-doped of red fluorescent carbon dots

BACKGROUND

Creatinine is a small molecule disease biomarker that reflects kidney function, accurate and effective detection of creatinine will play an important role in the prevention and treatment of diseases. Currently, commonly used creatinine detection methods are limited by expensive instruments, complex sample preparation, many interference factors from biological samples, and environmental factors that can affect the accuracy of the measurement. Therefore, developing a fast, simple, inexpensive, sensitive analysis method that can eliminate background interference and provide multi-detection modes has strong attraction and value.

RESULTS

Here, we prepared ratio fluorescence and smartphone-assisted colorimetry dual-mode platform for the detection of creatinine based on F, B, N-doped of red fluorescent carbon dots (HAc-CDs). HAc-CDs were synthesized via hydrothermal method using o-phenylenediamine and tetrafluoroboric acid. Under an excitation wavelength of 360 nm, HAc-CDs exhibit two emission peaks at 599 nm and 652 nm with full width at half-maximums of 43.8 nm and 43.3 nm, respectively. In the presence of creatinine, the fluorescence peak at 599 nm with orange light increases, while the peak at 652 nm with red light decreases. This phenomenon of creatinine-HAc-CDs is inferred to be aggregation-induced emission. The ratio of fluorescence intensity (F652/F599) is linearly related to the concentration of creatinine range from 3.0 × 10-10 to 1.0 × 10-3 M with a detection limit of 0.084 nM. Additionally, a smartphone-assisted recognition creatinine intelligent detection system based on the color change of paper strips was constructed.

SIGNIFICANCE

Creatinine in urine can be dual-mode detected with ratio fluorescence and smartphone-assisted colorimetry based on the prepared F, B, N-doped of red fluorescent carbon dots. Dual-mode detection system enables convenient, reliable and visual detection for on-site applications, and it has reference significance for the development of other disease biomarker detection methods.

Carbon-Based Nanomaterials Alter the Behavior and Gene Expression Patterns of Bacteria

One of the most dangerous characteristics of bacteria is their propensity to form biofilms and their resistance to the drugs used in clinical practice today. The total number of genes that can be categorized as virulence genes ranges from a few hundred to more than a thousand. The bacteria employ a variety of mechanisms to regulate the expression of these genes in a coordinated manner during infection. The search for new agents with anti-virulence capacity is therefore crucial. Nanotechnology provides safe platforms for targeted therapies to combat a broad spectrum of microbial infections. As a new class of innovative materials, carbon-based nanomaterials (CBNs), which include carbon dots, carbon nanotubes, graphene, and fullerenes can have strong antibacterial activity. Exposure to CBNs has been shown to affect bacterial gene expression patterns. This study investigated the effect of CBNs on the repression of specific genes related to bacterial virulence/pathogenicity.

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.

Green synthesis of red-emitting carbon dots for bioimaging, sensing, and antibacterial applications

It is a highly desirable and formidable challenge to synthesize carbon dots with long-wavelength emission using green synthesis. In this work, we explored red-emitting carbon dots (rCDs) via a hydrothermal strategy and their multifunctional application for bioimaging in vivo/vitro, curcumin sensing, and antibacterial materials. As-prepared rCDs were water-soluble and monodispersed with an average diameter of 2.34 nm. Significantly, these rCDs exhibited low toxicity and outstanding biocompatibility, which was consistent with the excellent bioimaging performance in living cells, zebrafish, and nude mice, providing them a promising prospect for clinical applications. Meanwhile, the obtained rCDs were also used as a fluorescent probe for sensitive detection of curcumin in a wide linear range of 0.03-135.73 μM with a limit of detection of 29.37 nM. Furthermore, quaternized rCDs were designed and used as antibacterial material with minimum inhibitory concentrations against Staphylococcus aureus and Escherichia coli of 0.15 mg/mL and 0.5 mg/mL, respectively, which advanced the development of novel antibacterial agents and broadened the applications of red-emitting CDs. Therefore, this work provided multifunctional CDs with red emission for use in the fields of biological imaging, fluorescence sensing, and antibacterial materials.

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.

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.

Antibacterial carbon dots

Bacterial infections significantly threaten human health, leading to severe diseases and complications across multiple systems and organs. Antibiotics remain the primary treatment strategy for these infections. However, the growing resistance of bacteria to conventional antibiotics underscores the urgent need for safe and effective alternative treatments. In response, several approaches have been developed, including carbon dots (CDs), antimicrobial peptides, and antimicrobial polymers, all of which have proven effective in combating bacterial resistance. Among these, CDs stand out due to their unique advantages, including low preparation cost, stable physicochemical properties, high biocompatibility, tunable surface chemistry, strong photoluminescence, and efficient generation of reactive oxygen species. These features make CDs highly promising in antibacterial applications. This review explores the development of antibacterial CDs, focusing on their mechanisms of action-physical destroy, biochemical damage, and synergistic effects-while highlighting their potential for clinical use as antibacterial agents.

Highly efficient and broad-spectrum antibacterial carbon dots combat antibiotic resistance

Bacterial infections have become a major global public health issue, particularly with the emergence of multidrug-resistant strains. Therefore, developing non-antibiotic antimicrobial agents is crucial for treating drug-resistant bacterial infections. Building on previous research into natural products as novel antibacterial agents, this study synthesized curcumin-derived carbon dots using curcumin and ethylenediamine as raw materials through a hydrothermal method. The resulting carbon dots not only improved the water solubility and stability of curcumin but also exhibited highly efficient broad-spectrum antibacterial activity. Detailed investigations into the antibacterial performance and mechanisms of the carbon dots were conducted through experiments such as minimum inhibitory concentration (MIC) determination, live/dead bacterial staining, morphological studies, nucleic acid concentration detection, and reactive oxygen species (ROS) detection. The results indicated that the carbon dots significantly damaged the structural integrity of bacteria and generated large amounts of ROS. They exhibited remarkable antibacterial effects against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, and effectively inhibited drug-resistant MRSA. Their antibacterial efficacy was notably superior to that of broad-spectrum antibiotics such as chloramphenicol and Sulfadiazine. This study highlights the potential application of curcumin-derived carbon dots in combating bacterial infections and provides valuable insights for developing novel antibacterial agents derived from natural products.

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.

New Strategy for Microbial Corrosion Protection: Photocatalytic Antimicrobial Quantum Dots

Microbial corrosion has significant implications for the economy, environment, and human safety worldwide. Photocatalytic antibacterial technology, owing to its advantages in environmental protection, broad-spectrum, and efficient sterilization, presents a compelling alternative to traditional antibacterial strategies for microbial corrosion protection. In recent years, photocatalytic quantum dot materials have garnered considerable attention in this field due to their unique quantum effects. This article provides a brief overview of the quantum effects associated with quantum dot materials, reviews the classification and preparation methods of these photocatalytic quantum dots, and elucidates their inhibitory effects and mechanisms against microbial corrosion. Finally, this article summarizes unresolved issues and prospects for the future development of quantum dots in the realm of microbial corrosion protection.

Synthesis of metal framework-modified carbon dots with super large stokes shift using Hami melon as a green precursor for detecting thiophanate-methyl residue in leafy vegetables

Consuming leafy vegetables with excessive thiophanate-methyl (TM) residue poses serious risks to human health. To realize rapidly and sensitively detecting TM in leafy vegetables, we developed a fluorescent probe based on zeolitic imidazolate framework-8-modified carbon dots using Hami melon as the green precursor (HM-CDs@ZIF-8). Meanwhile, the mechanism of HM-CDs@ZIF-8 for detecting TM was investigated and explained. The results of the performance tests showed that the prepared HM-CDs@ZIF-8 exhibited high sensitivity, excellent selectivity, robust anti-interference capability, reliable reproducibility and repeatability, and long-term stability. After optimization experiments, the fluorescence intensity of HM-CDs@ZIF-8 showed a strong linear correlation with the concentration of TM (0.00171-3.4239 mol/L) with a detection limit of 2.025 μmol/L. The HM-CDs@ZIF-8 was successfully applied to determine TM in spiked leafy vegetables with satisfactory recoveries of 96-105%. The relative standard deviations were in the range of 0.26-2.55%. The sensor has a promising application for detecting TM in leafy vegetables.

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.

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.

Fluorescent carbon dots for labeling of bacteria: mechanism and prospects-a review

The search for bacteria-labeling agents that are more efficient and less toxic compared to existing staining dyes is ongoing. Fluorescent quantum dots and carbon dots (CDs) have been extensively researched for various bioimaging applications. Priority is given to CDs due to several advantages, including lower toxicity, versatility in tuning their properties, and better photostability compared to metal-based quantum dots. Although significant progress is still needed to replace existing dyes with CDs for bacteria labeling, they offer promising potential for further improvement in efficiency. Surface charges and functional groups have been reported as decisive factors for bacterial discrimination and live/dead assays; however, a complete guideline for preparing CDs with optimum properties for efficient staining and predicting their labeling performance is lacking. In this review, we discuss the application of fluorescent CDs for bacterial labeling and the underlying mechanisms and principles. We primarily focus on the application and mechanism of CDs for Gram differentiation, live imaging, live/dead bacteria differentiation, bacterial viability testing, biofilm imaging, and the challenges associated with application of CDs. Based on proposed mechanisms of bacterial labeling and ambiguous results reported, we provide our view and guidelines for the researchers in this field to overcome the challenges associated with bacteria labeling using fluorescent CDs.

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.