Antibacterial activity of positively charged carbon quantum dots without detectable resistance for wound healing with mixed bacteria infection

Eco-Friendly Multifunctional Hydrogel Sensors Enabled Sustainable and Accurate Human-Machine Interaction System

Wearable epidermic electronics assembled by conductive hydrogels exhibit great application potential for their seamless integration with the human body for human-machine interactions (HMI). However, most multifunctional hydrogel sensors are prone to water loss and become useless e-waste, resulting in a growing threat to the global environment and human health. Inspired by the resurrection plants, this paper introduces the reversible intermolecular forces and physical crosslinking method into the hydrogel system to obtain a fully recyclable multifunctional smart hydrogel sensor (RMSHS), which can be completely recycled in a simple step. Meanwhile, RMSHS possesses admirable biocompatibility, excellent antibacterial ability (S. aureus and E. coli bacterial inhibition rate of 99.8%), rapid self-healing ability, and outstanding sensing performances such as low detection limit, fast response/recovery time (160/200 ms). Intelligent medical rehabilitation and smart HMI systems are developed for medical diagnostics and real-time remote controlling. Moreover, the recyclable triboelectric nanogenerator (R-TENG) intelligent array, designed based on RMSHS, replaces the electrode consumables in traditional TENGs, realizing the generation of green energy and 100% recyclability of electrode materials. RMSHS can be generalized and applied to other remote-controlling platforms, paving the way for large-scale, multi-scenario applications.

Toxicological Effects of Metal-Doped Carbon Quantum Dots

Multi-domain biological and environmental research highlights the efficacy of carbon quantum dots (CQDs) as a safer alternative to toxic metal-based quantum dots (QDs) and expensive conventional organic dyes, particularly in biomedical applications. CQDs are often functionalized by metal heteroatoms to improve their electron-donating properties and modify charge density, thereby enhancing their physicochemical characteristics. However, metal doping may re-introduce toxicity concerns similar to traditional QDs and further increase environmental risks. Thus, detailed ecotoxicology studies are necessary to understand the environmental impact of these CQDs in different organisms. To address this, we synthesized metal-doped CQDs (Mn, Fe, Cu and Ag) using microwave-assisted technique and conducted in-vitro experiments on diverse biological models belonging to different trophic levels, including bacteria (E. coli and B. subtilis), plants (Vigna radiata) and mammalian cells (mouse myoblast cells- C2C12). Results revealed that among all the CQDs explored, Ag-CQDs exhibited highest toxicity causing ~85% bacterial and 100% mammalian cell death even at 10 μg mL-1 and ~60% radicle growth inhibition after 5 days of exposure at 50 μg mL-1, whereas Mn-CQD showed the least toxicity. These findings contribute significantly to the critical need for determining optimal concentration ranges for metal-doped CQDs and enhance our understanding of their environmental implications.

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.

In vitro antimicrobial and anticancer potentials of green synthesized luminescent carbon quantum dots derived from artichoke leaves

Naturally derived carbon quantum dots (CQDs) are novel carbon-based nanomaterials with excellent traits. It is highly demanded to develop CQDs from biowaste that have excellent photostability, a simple synthesis approach, and an appealing output so that they can be used widely in various fields. Herein, highly fluorescent CQDs were synthesized hydrothermally using artichoke leaves. The CQDs were synthesized and analyzed for their structure, optical properties, antimicrobial, and anticancer activities. The CQDs exhibited antimicrobial action against a single fungus strain in addition to Gram-positive and Gram-negative cells; also, the cytotoxicity against the MCF-7 cell line was evaluated as 96.5 µg/mL. The findings indicated that the spherical dots have a semi-spherical shape with the smallest size of 2.88 nm, and a zeta potential value of 37.31 V, thus confirming that the synthetic CQDs are in an outstanding colloidal state. When photoexcited at 320 nm, the dots were found to show blue fluorescence at 398 nm with a fluorescence quantum yield of 3.32%, long fluorescence decay time, high photostability, and good sensing for hydrogen peroxide. Additionally, the effect of ionic strength was evaluated.

Multifunctional Carbon Quantum Dots for Monitoring and Therapy of Bacterial Infected Wounds

Bacterial infections in wounds and bacteremia present significant global health challenges, driving the urgent need for innovative alternatives to traditional antibiotics. Here, the development of PEI-EDTA-2Na carbon quantum dots (PECDs) synthesized via a hydrothermal method is reported. Synthesis conditions affect PECDs' antibacterial efficacy; those at 180 °C have optimal -NH2 functionalization for better adhesion and activity. PECDs are pH - responsive, eradicating bacteria in weakly acidic conditions by disrupting DNA and proteins. Following the resolution of infection, PECDs adapt to neutral and alkaline environments, where they scavenge reactive oxygen species (ROS), reduce inflammation, promote macrophage polarization, and accelerate wound healing. Furthermore, PECDs significantly improve survival in bacteremia models. Their intrinsic fluorescence enables real-time pH monitoring of wounds, offering a non-invasive diagnostic tool. Genomic and transcriptomic analyses reveal that PECDs disrupt bacterial metabolism and resistance pathways, while simultaneously supporting antibacterial and anti-inflammatory responses during tissue repair. This dual functionality-combining therapeutic efficacy in wound healing with antimicrobial and anti-inflammatory properties in bacteremia-positions PECDs as a versatile platform for smart wound management and an emerging candidate for advanced biomedical applications.

Artificial Bone Materials for Infected Bone Defects: Advances in Antimicrobial Functions

Infected bone defects, caused by bacterial contamination following disease or injury, result in the partial loss or destruction of bone tissue. Traditional bone transplantation and other clinical approaches often fail to address the therapeutic complexities of these conditions effectively. In recent years, advanced biomaterials have attracted significant attention for their potential to enhance treatment outcomes. This review explores the pathogenic mechanisms underlying infected bone defects, including biofilm formation and bacterial internalization into bone cells, which allow bacteria to evade the host immune system. To control bacterial infection and facilitate bone repair, we focus on antibacterial materials for bone regeneration. A detailed introduction is given on intrinsically antibacterial materials (e.g., metal alloys, oxide materials, carbon-based materials, hydroxyapatite, chitosan, and Sericin). The antibacterial functionality of bone repair materials can be enhanced through strategies such as the incorporation of antimicrobial ions, surface modification, and the combined use of multiple materials to treat infected bone defects. Key innovations discussed include biomaterials that release therapeutic agents, functional contact biomaterials, and bioresponsive materials, which collectively enhance antibacterial efficacy. Research on the clinical translation of antimicrobial bone materials has also facilitated their practical application in infection prevention and bone healing. In conclusion, advancements in biomaterials provide promising pathways for developing more biocompatible, effective, and personalized therapies to reconstruct infected bone defects.

Chemical and functional inheritance of carbon quantum dots hydrothermally-derived from chitosan

Owing to their extremely small size, carbon-quantum-dots (CQDs) can cross biological barriers, which makes them attractive for many biomedical and other applications. CQDs can retain key-chemical features and associated functionalities of the molecular sources they are derived from, provided a suitable synthesis method is used at relative mild carbonization temperatures. Here we demonstrate that CQDs hydrothermally-derived from chitosan or 2-hydroxypropyltrimethyl ammonium-chloride (HAC)-chitosan under pressurized conditions at 180 °C have a comparable elemental and molecular composition, as determined using X-ray photoelectron spectroscopy and Fourier-transform-infrared spectroscopy. In addition, both types of CQDs generated reactive-oxygen-species as an added functionality alien to their molecular carbon sources. As a result, CQDs exhibited stronger antibacterial properties against a Gram-positive Staphylococcus aureus and a Gram-negative Escherichia coli strain, while both molecular HAC-chitosan as well as CQDs derived from it had stronger antibacterial properties than molecular chitosan and chitosan CQDs due to the possession of quaternary ammonium groups in HAC-chitosan. Therewith, carbonization of chitosan and HAC-chitosan yields enhanced properties that can be beneficial in a high variety of different applications, including promotion of healing and bacterial infection control, preservation of food and beverages, pesticide control in agriculture and horticulture, water treatment and in many cosmetics and personal care products.

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.

Nanobiotic Formulations utilizing Quinoline-based-Triazole functionalized Carbon Quantum Dots via Click Chemistry for Combatting Clinical-Resistant Bacterial Pathogens

Therapeutic options for preventing the trajectory of multi-drug resistance bacterial pathogens could rely on the effort to design a novel technique to develop a potent antimicrobial agent to counter the key issue. To curb the current outbreak, we synthesized first generation of antimicrobial amine-modified carbon quantum dots, CQDs-NH2 as carbon precursors followed by hydrothermal carbonization of ethylenediamine/citric acid, and postmodified with propargyl alcohol (CQDs-1) and quinoline derivative; 8-hydroxy quinoline (CQDs-2) through Cu(I)-catalyzed azide-alkyne cycloaddition. The novel clicked 1,2,3-triazole functionalized CQDs-NH2 templates, were evaluated against standard Gram-positive; Staphylococcus aureus (S. aureus), and Gram-negative; Escherichia coli (E. coli), MRSA, along with clinical-resistant diabetic foot PUS swab isolated bacterial pathogens by 96-well method as well as agar-well diffusion method, to unleased the potential antibacterial activity. 1,2,3-triazole functionalized CQDs-NH2 template showed enhanced antibacterial activity against distinct bacterial strains, with minimum inhibitory concentration for standard bacteria, MRSA-bacteria, and clinical resistant bacterial pathogens in the range of 0.25-8, 64-128, and 128-256 μg mL-1 respectively. This nanobiotic template displays good potential through the hybridization of 1,2,3-triazole with antibacterial pharmacophores CQDs-NH2 and quinoline, to overcome drug resistance, reduce toxicity, and improve pharmacokinetic profiles. The findings of this study might have a favorable impact on antibiotic pharmacodynamics and, as a result, nanobiotic dosing regimens as well as clinical outcomes.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-024-01266-x.

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.

Synthesis and Characterization of Lignocellulose-Based Carbon Quantum Dots (CQDs) and Their Antimicrobial and Antioxidant Functionalities

Carbon quantum dots (CQDs) have recently drawn enormous attention due to not only their unique chemical, biological, and optical properties but also because a variety of renewable biomasses are readily utilized as carbon sources in their synthesis. This study investigated the synthesis, characterization, and functional evaluation of CQDs from unbleached mechanical pulp as a natural lignocellulosic resource. The CQDs were synthesized using a one-step hydrothermal synthesis with varying temperature, time, and pulp consistency. The resulting CQDs exhibit a spherical shape with a size distribution of 9.73 ± 0.82 nm and lattice parameters of 0.21 and 0.34 nm, indicating a graphite core. The photoluminescence spectra showed evident fluorescence characteristics, with an emission peak at 435 nm at an excitation wavelength of 370 nm. The as-prepared CQDs were also chemically composed of C=C and C=O bonds linked to the hydroxyl and carboxyl functional groups, which are typically found in lignocellulose-based CQDs. The CQDs demonstrated antibacterial activity exceeding 99.9% against E. coli at the lowest concentration of 0.75 mg/mL. Demonstrating its antioxidation property, the DPPH radical scavenging activity surpassed 90% with more than 40 µg/mL of the CQD solution.

Carbon Quantum Dot Nanoparticles Enhance the Efficacy of Spodoptera littoralis Nucleopolyhedrovirus Suspoemulsion

This study evaluates the efficacy of Spodoptera littoralis nucleopolyhedrovirus (SpliNPV) and laboratory-synthesized carbon quantum dot nanoparticles (CQDNPs) against the second instar Spodoptera littoralis larvae under laboratory and greenhouse conditions. Individually, both SpliNPV and CQDNPs exhibited substantial lethality (91.6% and 83.3% at 1 × 108 OBs/ml and 700 mg/ml, respectively) (p < 0.05). The LC50 values were 1.88 × 105 OB/ml and 434.2 mg/mL, and the LT50 values were 8.9 and 9.8 days, respectively. Four LC-based combined treatments demonstrated significant additive effects, with the SpliNPV (LC50) + CQDNPs (LC25) combination achieving the optimum effect with a mortality rate of 86.3% and an LT50 value of 6.6 days, leading to its selection for the suspoemulsion nanoparticle (SENP) formulation. The SENP formulation displayed superior performance, achieving the highest mortality rates and fastest killing times across all environments: 89.0% in laboratory conditions, 83.3% on eggplant plants, and 76.6% on pepper plants. In contrast, the suspoemulsion (SE) and unformulated (UF) formulations showed lower efficacy, emphasizing the importance of formulation in enhancing the biological activity of SpliNPV. The LT50 values further supported these findings, with the SENP formulation demonstrating the shortest LT50 values, indicating faster lethality. A significant decrease in CHS-B, IIM2, PER3, REPAT14, and CDA1 expression was observed, particularly in the combined CQDNPs + SpliNPV treatment, while API expression increased significantly. These findings highlight the potential of nanoparticle-enhanced formulations like SENP, and integrating CQDNPs with SpliNPV can significantly enhance pest control efficacy.

Blazing Carbon Dots: Unfolding its Luminescence Mechanism to Photoinduced Biomedical Applications

Carbon dots (CDs) are carbon-based nanomaterials that have garnered immense attention owing to their exceptional photophysical and optoelectronic properties. They have been employed extensively for biomedical imaging and phototherapy due to their superb water dispersibility, low toxicity, outstanding biocompatibility, and exceptional tissue permeability. This review summarizes the structural classification of CDs, the classification of CDs according to precursor sources, and the luminescence mechanism of CDs. The modification in CDs via various doping routes is comprehensively reviewed, and the effect of such alterations on their photophysical properties, such as absorbance, photoluminescence (PL), and reactive oxygen species generation ability, is also highlighted. This review strives to summarize the role of CDs in cellular imaging and fluorescence lifetime imaging for cellular metabolism. Subsequently, recent advancements and the future potential of CDs as nanotheranostic agents have been discussed. Herein, we have discussed the role of CDs in photothermal, photodynamic, and synergistic therapy of anticancer, antiviral, and antibacterial applications. The overall summary of the review highlights the prospects of CD-based research in bioimaging and biomedicine.

High Inhibition Activity of CQDs-Macaranga tanarius Organic Framework Nanomaterial-Based Antibacterials

Antibacterial agent based on modification of Macaranga tanarius (M. tanarius) extract into CQDs@M. tanarius has been successfully synthesized and applied against Escherichia coli and Staphylococcus aureus. Macaranga tanarius plants were obtained from Buton Island, Southeast Sulawesi-Indonesia, and used as precursors for Carbon Quantum Dots (CQDs). In the synthesis, the dried leaves of M. tanarius were macerated, and then the filtrate was modified hydrothermally in a Teflon-lined stainless steel autoclave. The modification results produce nano-sized CQDs@M. tanarius particles. The PSA test confirmed this, which described the CQDs@M. tanarius particle size as 57.0 nm. The results of UV-Vis spectroscopy tests illustrate that the CQDs@M. tanarius molecules experience π → π* and n → π* electronic transitions at a wavelength of 367 nm. Meanwhile, in the FTIR spectroscopy test, stretching vibrations from the functional groups -OH, C-H, C=O, C-O, and the benzene ring were observed at wave numbers 3415.93 cm-1, 2976.16 cm-1, 1641.42 cm-1, 1274.95 cm-1, and 692.44 cm-1, respectively. Based on the antibacterial activity test, it is known that CQDs@M. tanarius has high inhibitory activity against E. coli and S. aureus. The resulting inhibition diameters are 15.82 mm and 11.24 mm, respectively. This high inhibitory diameter further illustrates the potential of CQDs@M. tanarius for its further application as an antibacterial material in the future.

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.

New emerging materials with potential antibacterial activities

The increasing prevalence of multidrug-resistant pathogens is a critical public health issue, necessitating the development of alternative antibacterial agents. Examples of these pathogens are methicillin-resistant Staphylococcus aureus (MRSA) and the emergence of "pan-resistant" Gram-negative strains, such as Pseudomonas aeruginosa and Acinetobacter baumannii, which occurred more recently. This review examines various emerging materials with significant antibacterial activities. Among these are nanomaterials such as quantum dots, carbon quantum dots, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and layered double hydroxides, all of which demonstrate excellent antibacterial properties. Interestingly, including antibacterial agents within the structure of these materials can help avoid bacterial resistance and improve the long-term efficacy of the materials. Additionally, the antibacterial potential of liquid solvents, including ionic liquids and both deep eutectic solvents and natural deep eutectic solvents, is explored. The review discusses the synthesis methods, advantages, and antibacterial efficacy of these new materials. By providing a comprehensive overview of these innovative materials, this review aims to contribute to the ongoing search for effective solutions to combat antibiotic resistance. Key studies demonstrating antibacterial effects against pathogens like Escherichia coli, Staphylococcus aureus, and multidrug-resistant strains are summarized. MOFs have exhibited antibacterial properties through controlled ion release and surface interactions. COFs have enhanced the efficacy of encapsulated antibiotics and displayed intrinsic antibacterial activity. Other nanomaterials, such as quantum dots, have generated reactive oxygen species, leading to microbial inactivation. This review aims to provide insights into these new classes of antibacterial materials and highlight them for addressing the global crisis of antibiotic resistance. KEY POINTS: • Nanomaterials show strong antibacterial effects against drug-resistant bacteria • Emerging solvents like ionic liquids offer novel solutions for bacterial resistance • MOFs and COFs enhance antibiotic efficacy, showing promise in combating resistance.

Green synthesis of fluorescent N-doped carbon quantum dots from castor seeds and their applications in cell imaging and pH sensing

Water-soluble fluorescent N-doped carbon quantum dots (N-CQDs) were hydrothermally prepared through a green synthesis route using castor seeds as a single precursor and a hydrothermal method. Several experimental techniques have been used to characterize synthesized N-CQDs to confirm their structure and to verify their applicability in cell imaging and pH sensing. The synthesized N-CQDs were found to have are characterized by amorphous nature with a spherical shape with an average particle size of 6.57 nm as revealed from XRD and TEM measurements. The FTIR results reveal the presence of carboxylic and hydroxyl functional groups on the surface of the CQDs, which was also confirmed by XPS analysis. The fluorescence characterization of the synthesized N-CQDs showed blue emission and excitation dependence with good photostability. It was found that the optimal excitation and emission wavelengths were (λEx = 360) and (λEm = 432) nm, respectively. The fluorescence quantum yield (QY) of about 9.6% at the optimum excitation wavelength 360 nm. Moreover, the fluorescence intensity of N-CQDs showed good linear dependence with the pH values in ranges of 3.5 - 7.5 and 8 - 12 as well as high sensitivity for slight changes of pH values. According to these results, two fluorescent pH sensors were created based on acidic and basic media. The obtained N-CQDs have zeta potential of -21.86 mV and thus have excellent stability in water. Moreover, N-CQDs derived from the castor seeds have antimicrobial activity and exhibits low cytotoxicity to WI-13 cells with IC50 = 394.4 ± 13.8 µg/mL. The results of this study demonstrated that the synthesized N-CQDs derived from castor seeds can be used as pH sensing and antimicrobial materials. On the other hand, they are also promising in applications in cell imaging, thermo-sensing and optoelectronics.

Functional composite films incorporating triphala-derived carbon dots for extending chicken preservation

Triphala-based carbon dots (T-CDs) were successfully prepared using a simple one-step hydrothermal method. T-CDs were characterized by absorbance, fluorescence, Fourier-transform infrared, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. T-CDs showed bright blue fluorescence at 434 nm upon excitation at 360 nm. Functional composite films were prepared using poly(vinyl alcohol) and gelatin mixture by incorporating T-CDs and applied as a packaging film to extend the shelf life of chicken. The antibacterial activity of T-CDs against Listeria monocytogenes and Staphylococcus aureus was evaluated using well diffusion and colony count methods. T-CDs were evenly dispersed throughout the PVA/Gel solution to form a dense and uninterrupted film. They also formed strong bonds with polymer chains, which improved the tensile strength of the film from 32.44 to 42.70 MPa. Furthermore, the presence of T-CDs significantly enhanced the UV-blocking ability of the PVA/Gel films, achieving 99.7 % for UV-B and 97.2 % for UV-A. In addition, the PVA/Gel/T-CDs composite films showed excellent antioxidant, antimicrobial and UV-barrier properties, extending the shelf life of chicken. Therefore, the PVA/Gel/T-CDs composite films showed great potential as an active food packaging material to extend the shelf life and preserve the visual quality of packaged meat.

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.

Multifunctional nitrogen-sulfur codoped carbon quantum dots: Determining reduced glutathione, broad-spectrum antibacterial activity, and cell imaging

In this study, nitrogen-sulfur codoped carbon quantum dots (N-S/CQDs) with various functions and properties were synthesized through a one-step method utilizing citric acid and cysteine as reaction substrates. The fluorescence of N-S/CQDs can be specifically quenched by permanganate ion (MnO4 -), and the quenched fluorescence can be recovered by the presence of reduced glutathione (GSH). A fluorescence sensing system based on N-S/CQDs@MnO4 - was developed and successfully applied for the determination of GSH in pharmaceutical preparations. Additionally, N-S/CQDs demonstrated broad-spectrum antibacterial activity, with minimum inhibitory concentrations of 32 μg/ml against Staphylococcus aureus (gram-positive bacterium) and 64 μg/ml against Escherichia coli (gram-negative bacterium). N-S/CQDs also proved effective for cell imaging, exhibiting excellent biocompatibility. These findings underscore the multifunctional characteristics and promising application potential of N-S/CQDs. Furthermore, this study provides a solid foundation for the development of multifunctional carbon quantum dots and the expansion of their applications in various fields.

Anticancer activity of quantum size carbon dots: opportunities and challenges

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

A Comprehensive Review of Nanoparticles: From Classification to Application and Toxicity

Nanoparticles are structures that possess unique properties with high surface area-to-volume ratio. Their small size, up to 100 nm, and potential for surface modifications have enabled their use in a wide range of applications. Various factors influence the properties and applications of NPs, including the synthesis method and physical attributes such as size and shape. Additionally, the materials used in the synthesis of NPs are primary determinants of their application. Based on the chosen material, NPs are generally classified into three categories: organic, inorganic, and carbon-based. These categories include a variety of materials, such as proteins, polymers, metal ions, lipids and derivatives, magnetic minerals, and so on. Each material possesses unique attributes that influence the activity and application of the NPs. Consequently, certain NPs are typically used in particular areas because they possess higher efficiency along with tenable toxicity. Therefore, the classification and the base material in the NP synthesis hold significant importance in both NP research and application. In this paper, we discuss these classifications, exemplify most of the major materials, and categorize them according to their preferred area of application. This review provides an overall review of the materials, including their application, and toxicity.

Seizing the Hidden Assassin: Current Detection Strategies for Staphylococcus aureus and Methicillin-Resistant S. aureus

Staphylococcus aureus (S. aureus) is a kind of pathogenic bacteria which can lead to food poisoning, hospital, and community infections. S. aureus and methicillin-resistant S. aureus (MRSA) have become headaches for public health worldwide. Therefore, strengthening the detection of S. aureus and MRSA is a critical step to prevent and control its spread and infection. This review summarized multiple detection methods (electrochemical, optical, and other biosensors) for sensitive and efficient detection of nonresistant and resistant S. aureus. First, we have introduced the principle and methods of detection platform for S. aureus and MRSA. We also contrasted various detection strategies. Finally, the current situation and prospect of S. aureus and MRSA detection in the future are explored in depth, and its development direction of detection methods is also predicted. In this review, we found that although biosensors have shown tremendous brilliance in the field of monitoring, they are currently in the experimental stage. It can be certain that we are very close to entering the commercialization stage. The point-of care testing available to nonprofessionals will become a new direction. We firmly believe that the monitoring system will be more perfect and stable and public life will be healthier and safer.

Preparation of the double cross-linking carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film for food active packaging application

This paper prepared a new kind of carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film with antibacterial properties. Carbon dots and citric acid were used as cross-linking agents, and polyvinyl alcohol and carboxymethyl cellulose were used as matrices respectively. The mechanical properties, UV shielding performance, thermal stability, antioxidant capability, and antibacterial activities of the carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film were researched. The prepared carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film was applied in the strawberry freshness preservation test. And test results indicated that the carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film could prevent rotting and extend the shelf life of strawberries. This carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film could be applied in the food active packaging field.

Emerging Trends in Nanomedicine: Carbon-Based Nanomaterials for Healthcare

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

Carbon dots as a novel photosensitizer for photodynamic therapy of cancer and bacterial infectious diseases: recent advances

Carbon dots (CDs) are novel carbon-based nanomaterials that have been used as photosensitizer-mediated photodynamic therapy (PDT) in recent years due to their good photosensitizing activity. Photosensitizers (PSs) are main components of PDT that can produce large amounts of reactive oxygen species (ROS) when stimulated by light source, which have the advantages of low drug resistance and high therapeutic efficiency. CDs can generate ROS efficiently under irradiation and therefore have been extensively studied in disease local phototherapy. In tumor therapy, CDs can be used as PSs or PS carriers to participate in PDT and play an extremely important role. In bacterial infectious diseases, CDs exhibit high bactericidal activity as CDs are effective in disrupting bacterial cell membranes leading to bacterial death upon photoactivation. We focus on recent advances in the therapy of cancer and bacteria with CDs, and also briefly summarize the mechanisms and requirements for PSs in PDT of cancer, bacteria and other diseases. We also discuss the role CDs play in combination therapy and the potential for future applications against other pathogens.

Endowing Polyetheretherketone with Anti-Infection and Immunomodulatory Properties through Guanidination Carbon Dots Modification to Promote Osseointegration in Diabetes with MRSA Infection

Methicillin-resistant Staphylococcus aureus (MRSA) infection and compromised immunity are the severe complications associated with implantation surgery in diabetes mellitus. Enhancing the antibacterial and immunomodulatory properties of implants represents an effective approach to improve the osseointegration of implant in diabetes mellitus. Herein, guanidination carbon dots (GCDs) with antibacterial and immunoregulatory functions are synthesized. The GCDs demonstrate killing effect on MRSA without detectable induced resistance. Additionally, they promote the polarization of macrophages from the M1 to M2 subtype, with the inhibiting pro-inflammatory cytokines and promoting anti-inflammatory factors. Correspondingly, GCDs are immobilized onto sulfonated polyether ether ketone (SP@GCDs) using a polyvinyl butyraldehyde (PVB) coating layer through soaking-drying technique. SP@GCDs maintain stable antibacterial efficacy against MRSA for six consecutive days and retain the immunomodulatory function, while also possessing the long-term storage stability and biocompatibility of more than 6 months. Moreover, SP@GCDs significantly promote the proliferation and mineralization of osteoblasts. SP@GCDs facilitate osteogenesis through immunoregulatory. Additionally, SP@GCDs exert stable antibacterial and immune regulatory functions in implantation site of a diabetes rat, effectively promoting implant osseointegration regardless of the MRSA infection. These findings provide valuable insights into implant modification through designing nanomaterials with multifunction for enhancing osseointegration of diabetes mellitus, suggesting the promising clinical application prospects.

Antibacterial potentials of carbon dots immobilized on chitosan and glass surfaces

Due to their antibacterial activity, chitosan‑carbon dot composites possess great potential for pharmaceuticals, medicine, and food preservation. Conducting a comprehensive study of the interactions between chitosan, carbon dots, and bacteria is crucial to understanding the processes behind applying these composites. This study aimed to immobilize carbon dots (C-dots) synthesized from Elaeagnus angustifolia fruits on chitosan and glass microbeads' surfaces, to characterize the test materials obtained after synthesis and immobilization, and to investigate their antibacterial potentials. C-dot synthesis was carried out from water extract in an acidic medium with the help of microwave irradiation, and their structural and optical properties were characterized by TEM, XRD, FT-IR, UV-vis, Zeta potential, and fluorescence methods. The surface of the glass microbeads was first activated and functionalized with surface amine groups with a silaning agent. C-dots were immobilized on both glass and chitosan microbeads using a crosslinking agent. Antibacterial potentials of nine different test materials, obtained before or after immobilization, were evaluated both qualitatively (MIC and MBC) and quantitatively (GI50) on E. coli, S. typhimurium, B. subtilis, and S. aureus, with the standard broth microdilution method. FT-IR and SEM-EDX analyses showed that C-dots were immobilized on chitosan (˂1 mm) and glass (˂100 μm) microbead surfaces. C-dots reduced the cell viability by ~25 % on S. typhimurium and B. subtilis (MIC = 25 mg/mL). It was also found that the highest antibacterial effect was recorded for C-dots-glass microbeads, which had a toxic effect of 43 % on S. aureus. In addition, binding C-dots to glass microbeads increased the antibacterial effect selectively in Gram-positive bacteria, while binding to chitosan microbeads was effective in all bacteria. The study showed that the antibacterial potential of C-dots-chitosan microbeads is more effective than C-dots-glass microbeads. C-dots could be used as carbon-based nanomaterials in antibacterial surface preparation once immobilized.

Nanotechnology in the Diagnosis and Treatment of Antibiotic-Resistant Infections

The development of antimicrobial resistance (AMR), along with the relative reduction in the production of new antimicrobials, significantly limits the therapeutic options in infectious diseases. Thus, novel treatments, especially in the current era, where AMR is increasing, are urgently needed. There are several ongoing studies on non-classical therapies for infectious diseases, such as bacteriophages, antimicrobial peptides, and nanotechnology, among others. Nanomaterials involve materials on the nanoscale that could be used in the diagnosis, treatment, and prevention of infectious diseases. This review provides an overview of the applications of nanotechnology in the diagnosis and treatment of infectious diseases from a clinician's perspective, with a focus on pathogens with AMR. Applications of nanomaterials in diagnosis, by taking advantage of their electrochemical, optic, magnetic, and fluorescent properties, are described. Moreover, the potential of metallic or organic nanoparticles (NPs) in the treatment of infections is also addressed. Finally, the potential use of NPs in the development of safe and efficient vaccines is also reviewed. Further studies are needed to prove the safety and efficacy of NPs that would facilitate their approval by regulatory authorities for clinical use.

Construction and properties of a carbon dots-decorated gelatin-dialdehyde starch hydrogel with pH response release and antibacterial activity

An antibacterial carbon dot hydrogel (GDSS-PCD) was constructed based on gelatin, dialdehyde starch (DS) and carbon dots (S-PCDs). The formation mechanism of GDSS-PCD hydrogels was attributed to the synergistic cross-linking of hydrogen bonds and dynamic covalent bonds. With increasing S-PCD content, the mechanical and rheological properties of GDSS-PCD hydrogels can be improved, and the micropore size becomes denser. GDSS-PCD hydrogels had pH-dependent swelling and degradation behavior, with a high swelling rate under acidic conditions and relatively low swelling under neutral and alkaline conditions. The cumulative release of S-PCDs from the same hydrogel in an acidic environment was higher than that in an alkaline environment, indicating that the GDSS-PCD hydrogel had a pH-dependent controlled release ability. The release behavior of S-PCDs conformed to the first-order kinetic release model (R2 > 0.95), and the release mechanism was related to Fickian diffusion. The synergistic antibacterial mechanism of GDSS-PCD hydrogels against Staphylococcus aureus suggested that bacterial metabolism leads to an acidic culture environment, which releases S-PCDs and destroys the bacterial cell membrane for antibacterial purposes. In GDSS-PCD hydrogels, S-PCDs play the main antibacterial role, and the hydrogel plays a synergistic role in trapping bacteria. Carbon dot hydrogels are promising materials to fulfil the functions of antibacterial and controlled release in the food and biomedical fields.

Synthesis of multicolor luminescent carbon dots based on carboxymethyl chitosan for cell imaging and wound healing application: In vitro and in vivo studies

The construction of biomaterials that can facilitate wound healing is significantly challenging in the medical field, and bacterial infections increase this complexity. In this study, we selected the biomacromolecule carboxymethyl chitosan as a carbon source and citric acid as an auxiliary carbon source. We prepared carbon quantum dots with multicolor luminescence properties and higher quantum yields (QYs) using a facile one-pot hydrothermal method. We characterized them to select carbon dots (CDs) suitable for cell growth. Subsequently, their biocompatibility with L929 cells, antibacterial properties against Staphylococcus aureus, and efficiency in promoting wound healing in vivo were investigated. Our experimental results showed that CDs at an appropriate concentration had excellent bioimaging ability, were suitable for cell growth, and accelerated the healing of infected wounds. We believe these bioactive CDs have great potential in promoting wound healing.

Antibacterial Activity and Mechanism of Self-Assembly Spermidine-Capped Carbon Dots against Staphylococcus aureus

This paper investigated the antibacterial mechanism of spermidine-capped carbon dots (S-PCDs) against Staphylococcus aureus. The results showed that there were a large number of amino groups on the surface of S-PCDs and they had a high positive charge (+47.06 mV), which could be adsorbed on the negatively charged bacterial surface through electrostatic interaction and changed the permeability of the bacterial cell membrane. The extracellular protein and nucleic acid contents of S. aureus treated with S-PCDs were 5.4 and 1.2 times higher than those of the control group, respectively. The surface folds and defects of the bacterial cell membrane, and the leakage of cell contents were observed using SEM and TEM. The expression of metabolic oxidation regulatory genes dmpI, narJ and narK was upregulated and the intracellular ROS generation was induced, causing bacterial oxidative stress and eventually bacterial death. S-PCDs can effectively inhibit biofilm formation and had low cytotoxicity. The S-PCD treatment successfully inhibited microbial reproduction when pasteurized milk was stored at 25 °C and 4 °C. These results provide important insights into the antimicrobial mechanism of S-PCDs and lay the foundation for their application in the food field as a potentially novel bacteriostatic nanomaterial.

Biogenic carbon dots: a novel mechanistic approach to combat multidrug-resistant critical pathogens on the global priority list

This study delves into investigating alternative methodologies for anti-microbial therapy by focusing on the mechanistic assessment of carbon dots (CDs) synthesized from F. benghalensis L. extracts. These biogenic CDs have shown remarkable broad-spectrum anti-bacterial activity even against multi-drug resistant (MDR) bacterial strains, prompting a deeper examination of their potential as novel anti-microbial agents. The study highlights the significant detrimental impact of CDs on bacterial cells through oxidative damage, which disrupts the delicate balance of ROS control within the cells. Notably, even at low doses, the anti-bacterial activity of CDs against MDR strains of P. aeruginosa and E. cloacae is highly effective, demonstrating their promise as potent antimicrobial agents. The research sheds light on the capacity of CDs to generate ROS, leading to membrane lipid peroxidation, loss of membrane potential, and rupture of bacterial cell membranes, resulting in cytoplasmic leakage. SEM and TEM analysis revealed time-dependent cell surface, morphological, and ultrastructural changes such as elongation of the cells, irregular surface protrusion, cell wall and cell membrane disintegration, internalization, and aggregations of CDs. These mechanisms offer a comprehensive explanation of how CDs exert their anti-bacterial effects. We also determined the status of plasma membrane integrity and evaluated live (viable) and dead cells upon CD exposure by flow cytometry. Furthermore, comet assay, biochemical assays, and SDS PAGE identify DNA damage, carbohydrate and protein leakage, and distinct differences in protein expression, adding another layer of understanding to the mechanisms behind CDs' anti-bacterial activity. These findings pave the way for future research on managing ROS levels and developing CDs with enhanced anti-bacterial properties, presenting a breakthrough in anti-microbial therapy.

Boric Acid-Functionalized Carbon Dots as a High-Performance Antibacterial Agent against Escherichia coli

Bacterial infections and antibiotic abuse are a global threat to human health. In recent years, there has been a boom in research on antimicrobial agents with low toxicity and efficient nanomaterials. Boric acid-functionalized carbon dots (B-CDs) with negative surface charge were synthesized by the hydrothermal method. Covalent bonds were formed between the boric acid groups and the cis-diol groups of the polysaccharide in the bacterial cell wall, and numerous B-CDs were trapped on the bacterial surface. In the experiments of antibacterial activity, B-CDs presented strong bactericidal activity against Escherichia coli (E. coli) with a minimum bactericidal concentration of 12.5 μg/mL. The antibacterial mechanism suggested that B-CDs entered the cell interior by diffusion and posed significant damage to the double helix structure of E. coli DNA. Furthermore, B-CDs exhibited low toxicity. The results demonstrated that the novel antimicrobial B-CDs not only fought against E. coli infection and antibiotic misuse but also provided new ideas for safe and effective antimicrobial agents of carbon nanomaterials.

Polydopamine-activated celastrol carbon dots for synergistic chemotherapy-photothermal therapy of tumors

Synergistic chemotherapy and photothermal therapy (PTT) holds the promise of addressing the weakness of individualized chemotherapy and PTT. In this study, we synthesized a chemotherapeutic agent, PDA-Ce-CDs, which combines the photothermal conversion ability and the generation of hydroxyl radicals (•OH), enabling synergistic enhancement of antitumor effects. Furthermore, the localized heating effect of NIR radiation promoted the uptake of the PDA-Ce-CDs and enhances the sensitivity of intracellular reactive oxygen species (ROS). Finally, the antitumor activity of the PDA-Ce-CDs was evaluated through cell experiments and tumor-bearing mice experiments, confirming its excellent antitumor efficacy in vivo and in vitro. Our work presents a new strategy in cancer treatment by utilizing carbon dots in combination with photothermal agents for synergistic chemotherapy-photothermal therapy. This innovative approach offers a new therapeutic avenue for synergistic tumor treatment by harnessing the combined effects of photothermal therapy and chemotherapy.

Carbon Dots' Potential in Wound Healing: Inducing M2 Macrophage Polarization and Demonstrating Antibacterial Properties for Accelerated Recovery

Bacterial infections and persistent inflammation can impede the intrinsic healing process of wounds. To combat this issue, researchers have delved into the potential use of carbon dots (CDs) in the regulation of inflammation and counteract infections. These CDs were synthesized using a microwave-assisted hydrothermal process and have demonstrated outstanding antibacterial and antibiofilm properties against Gram-positive and Gram-negative bacteria. Additionally, CDs displayed biocompatibility at therapeutic concentrations and the ability to specifically target mitochondria. CD treatment effectively nullified lipopolysaccharide-triggered reactive oxygen species production by macrophages, while simultaneously promoting macrophage polarization toward an anti-inflammatory phenotype (M2), leading to a reduction in inflammation and an acceleration in wound healing. In vitro scratch assays also revealed that CDs facilitated the tissue-repairing process by stimulating epithelial cell migration during reepithelialization. In vivo studies using CDs topically applied to lipopolysaccharide (LPS)-stimulated wounds in C57/BL6 mice demonstrated significant improvements in wound healing due to enhanced fibroblast proliferation, angiogenesis, and collagen deposition. Crucially, histological investigations showed no indications of systemic toxicity in vital organs. Collectively, the application of CDs has shown immense potential in speeding up the wound-healing process by regulating inflammation, preventing bacterial infections, and promoting tissue repair. These results suggest that further clinical translation of CDs should be considered.

The Addition of Co into CuO-ZnO Oxides Triggers High Antibacterial Activity and Low Cytotoxicity

In the present work, a simple two-step method is proposed for mixed oxide synthesis aimed at the achievement of antibacterial nanomaterials. In particular, Cu, Zn and Co have been selected to achieve single-, double- and triple-cation oxides. The synthesized samples are characterized by XRD, IR, SEM and EDX, indicating the formation of either crystalline or amorphous hydrocarbonate precursors. The oxides present one or two crystalline phases, depending on their composition; the triple-cation oxides form a solid solution of tenorite. Also, the morphology of the samples varies with the composition, yielding nanoparticles, filaments and hydrangea-like microaggregates. The antibacterial assays are conducted against E. coli and indicate an enhanced efficacy, especially displayed by the oxide containing 3% Co and 9% Zn incorporated into the CuO lattice. The oxides with the highest antibacterial properties are tested for their cytotoxicity, indicating a low toxicity impact, in line with literature data.

Antibacterial functionalized carbon dots and their application in bacterial infections and inflammation

Bacterial infections and inflammation pose a severe threat to human health and the social economy. The existence of super-bacteria and the increasingly severe phenomenon of antibiotic resistance highlight the development of new antibacterial agents. Due to low cytotoxicity, high biocompatibility, and different antibacterial mechanisms from those for antibiotics, functionalized carbon dots (FCDs) promise a new platform for the treatment of bacterial infectious diseases. However, few articles have systematically sorted out the available antibacterial mechanisms for FCDs and their application in the treatment of bacterial inflammation. This review focuses on the available antibacterial mechanisms for FCDs, including covalent and non-covalent interactions, reactive oxygen species, photothermal therapy, and size effect. Meanwhile, the design of antibacterial FCDs is introduced, including surface modification, doping, and combination with other nanomaterials. Furthermore, this review specifically concentrates on the research advances of antibacterial FCDs in the treatment of bacterial inflammation. Finally, the advantages and challenges of applying FCDs in practical antimicrobial applications are discussed.

Synthesis, properties and mechanism of carbon dots-based nano-antibacterial materials

Antibiotics play an important role in the treatment of diseases, but bacterial resistance caused by their widespread and unreasonable use has become an urgent problem in clinical treatment. With the rapid advancement of nanoscience and nanotechnology, the development of nanomedicine has been transformed into a new approach to the problem of bacterial resistance. As a new type of carbon-based nanomaterial, carbon dots (CDs) have attracted the interest of antibacterial researchers due to their ease of preparation, amphiphilicity, facile surface functionalization, and excellent optical properties, among other properties. This article reviewed the synthesis methods and properties of various CDs and their composites in order to highlight the advancements in the field of CDs-based antibacterial agents. Then we focused on the relationship between the principal properties of CDs and the antibacterial mechanism, including the following: (1) the physical damage caused by the small size, amphiphilicity, and surface charge of CDs. (2) Photogenerated electron transfer characteristics of CDs that produce reactive oxygen species (ROS) in themselves or in other compounds. The ability of ROS to oxidize can lead to the lipid peroxidation of cell membranes, as well as damage proteins and DNA. (3) The nano-enzyme properties of CDs can catalyze reactions that generate ROS. (4) Synergistic antibacterial effect of CDs and antibiotics or other nanocomposites. Finally, we look forward to the challenges that CDs-based nanocomposites face in practical antibacterial applications and propose corresponding solutions to further expand the application potential of nanomaterials in the treatment of infectious diseases, particularly drug-resistant bacterial infections.

Quaternized carbon dots with enhanced antimicrobial ability towards Gram-negative bacteria for the treatment of acute peritonitis caused by E. coli

Infections caused by Gram-negative bacteria still pose a clinical challenge. Although nanomaterials have been developed for antibacterial treatments, a systematic evaluation of the mechanisms and intervention models of antibacterial materials toward Gram-negative bacteria is still lacking. Herein, antibacterial quaternized carbon dots (QCDs) were synthesized via a one-step melting method using anhydrous citric acid and diallyl dimethyl ammonium chloride (DDA). The QCDs exhibited effective broad-spectrum antibacterial activity and enhanced inhibitory ability towards Gram-negative bacteria. The antibacterial mechanism of the QCDs with respect to Gram-negative bacteria was investigated through the characterization of bacterial morphology changes, the absorption modes of the QCDs on bacteria, and the potential generation of reactive oxygen species by the QCDs. The QCDs showed low toxicity in different cells, and did not cause hemolysis. The QCDs were administered via intraperitoneal injection to treat acute peritonitis in mice infected with E. coli. Routine blood examination, magnetic resonance imaging, and pathological analysis were undertaken and it was found that, similar to the positive control group treated with gentamicin sulfate, the QCDs exhibited a therapeutic effect that eliminated infection and inflammation. This study explores a controllable synthetic strategy for the synthesis of active carbon dots with antibacterial activity, a material that is a promising candidate for new treatments of Gram-negative bacterial infections.

Antibacterial Carbon Dots: Mechanisms, Design, and Applications

The increase in antibiotic resistance promotes the situation of developing new antibiotics at the forefront, while the development of non-antibiotic pharmaceuticals is equally significant. In the post-antibiotic era, nanomaterials with high antibacterial efficiency and no drug resistance make them attractive candidates for antibacterial materials. Carbon dots (CDs), as a kind of carbon-based zero-dimensional nanomaterial, are attracting much attention for their multifunctional properties. The abundant surface states, tunable photoexcited states, and excellent photo-electron transfer properties make sterilization of CDs feasible and are gradually emerging in the antibacterial field. This review provides comprehensive insights into the recent development of CDs in the antibacterial field. The topics include mechanisms, design, and optimization processes, and their potential practical applications are also highlighted, such as treatment of bacterial infections, against bacterial biofilms, antibacterial surfaces, food preservation, and bacteria imaging and detection. Meanwhile, the challenges and outlook of CDs in the antibacterial field are discussed and proposed.

Biofabrication of carbon quantum dots and their food packaging applications: a review

Carbon quantum dots (CQDs) are an emerging class of novel carbon nanomaterials (< 10 nm). These zero-dimensional CQDs have recently invoked significant interest due to their high fluorescence ability, strong electronic conductivity, biocompatibility, excellent chemical stability, non-toxicity, and environmental safety. Bio-fabrication of CQDs from organic resources remains attractive owing to their excellent functional properties. An emerging class of CQDs is fabricated by various conventional methods. However, these methods need many chemical agents and instrument facilities. Bio-fabrication of CQDs has a lot of benefits because of its simple fabrication and eco-friendly. Therefore, the green synthesized CQDs are considered optimistic candidates for developing novel functional materials for food packaging applications. Thus, it is important to investigate the latest update on green-based CQDs for food packaging applications. This current review paper discusses the physicochemical properties of CQDs, the bio-fabrication of CQDs, and the fluorescent properties of CQDs along with their food packaging applications.

Novel carbon nanozymes with enhanced phosphatase-like catalytic activity for antimicrobial applications

In this work, Sulfur and Nitrogen co-doped carbon nanoparticles (SN-CNPs) were synthesized by hydrothermal method using dried beet powder as the carbon source. TEM and AFM images indicated that these SN-CNPs form a round-shape ball with an approximate diameter of 50 nm. The presence of Sulfur and Nitrogen in these carbon-based nanoparticles was confirmed by FTIR and XPS analyses. These SN-CNPs were found to have strong phosphatase-like enzymatic activity. The enzymatic behavior of SN-CNPs follows the Michaelis-Menten mechanism with greater v_max and much lower K_m values compared to alkaline phosphatase. Their antimicrobial properties were tested on E. coli and L. lactis, with MIC values of 63 μg mL^-1 and 250 μg mL^-1, respectively. SEM and AFM images of fixed and live E. coli cells revealed that SN-CNPs strongly interacted with the outer membranes of bacterial cells, significantly increasing the cell surface roughness. The chemical interaction between SN-CNPs and phospholipid modeled using quantum mechanical calculations further support our hypothesis that the phosphatase and antimicrobial properties of SN-CNPs are due to the thiol group on the SN-CNPs, which is a mimic of the cysteine-based protein phosphatase. The present work is the first to report carbon-based nanoparticles with strong phosphatase activity and propose a phosphatase natured antimicrobial mechanism. This novel class of carbon nanozymes has the potential to be used for effective catalytic and antibacterial applications.

pH-Responsive wound dressings: advances and prospects

Wound healing is a complex and dynamic process, in which the pH value plays an important role in reflecting the wound status. Wound dressings are materials that are able to accelerate the healing process. Among the multifunctional advanced wound dressings developed in recent years, pH-responsive wound dressings, especially hydrogels, show great potential owing to their unique properties of adjusting their functions according to the wound conditions, thereby allowing the wound to heal in a regulated manner. However, a comprehensive review of pH-responsive wound dressings is lacking. This review summarizes the design strategies and advanced functions of pH-responsive hydrogel wound dressings, including their excellent antibacterial properties and significant pro-healing abilities. Other advanced pH-responsive materials, such as nanofibers, composite films, nanoparticle clusters, and microneedles, are also classified and discussed. Next, the pH-monitoring functions of pH-responsive wound dressings and the related pH indicators are summarized in detail. Finally, the achievements, challenges, and future development trends of pH-responsive wound dressings are discussed.

Antibacterial Properties of Three-Dimensional Flower Cluster ZIF-L Modified by N-Doped Carbon Dots

To overcome the problems of excessive ion release of inorganic antimicrobial agents and the biological toxicity of organic antimicrobial agents, metal organic framework (MOF) materials are attracting attention in the antimicrobial field due to their tunable structural properties and multifunctional applications. Most current studies are limited to zeolitic imidazolate framework-8 (ZIF-8), which has low antimicrobial efficiency by component release. Two-dimensional (2D) zeolitic imidazolate framework nanoleaf (ZIF-L) possesses better antimicrobial effect than ZIF-8 because of the physical destructionto bacteria by its blade tip. However, the in-situ synthesis method of two-dimensional ZIF-L, and the problem of leaf accumulation, limit the wider application of ZIF-L. In this paper, three-dimensional(3D) flower cluster-like ZIF-L (2–3 μm, +31.23 mv), with better antibacterial effects and a wider application range, was prepared by stirring without adding other reagents. To further improve the antibacterial performance of ZIF-L, nitrogen-doped carbon dots (NCDs) were electrostatically absorbed by ZIF-L to obtain NCDs@ZIF-L composites. The NCDs@ZIF-L composites showed over 95% and 85% antibacterial efficiency against E. coli and S. aureus, respectively, at a concentration of 0.25 mg/mL. In addition, polylactic acid (PLA) films mixed with ZIF-L and NCDs@ZIF-L composites with PLA showed good antimicrobial properties, indicating the applicability of ZIF-L and NCDs@ZIF-L composites for antibacterial materials. With a unique three-dimensional crystal shape and positive surface charge, ZIF-L and NCDs@ZIF-L composites exhibited excellent antibacterial properties, which provided a new perspective for the study of antimicrobial materials.

Chitosan/silk fibroin/nitrogen-doped carbon quantum dot/α-tricalcium phosphate nanocomposite electrospinned as a scaffold for wound healing application: In vitro and in vivo studies

A highly porous nanofibrous network that can functionalize antibacterial and therapeutic agents can be considered a suitable option for skin wound healing. In this study, α-tricalcium phosphate (α-TCP)/nitrogen-doped carbon quantum dots (N-CQDs) nanocomposite was synthesized and then applied to the fabrication of novel chitosan (CS)/silk fibroin (SF)/N-CQDs/α-TCP wound dressing via electrospinning system. The prepared nanomaterials were well characterized using X-ray diffraction, Fourier-transform infrared, scanning and transmission electron microscopes analyses, and antibacterial assay. Furthermore, nanofibers were evaluated regarding their physical properties, such as tensile behavior, water uptake capacity, and water contact angle. The results reveal that CS/SF/N-CQDs/α-TCP showed lower MIC values against E. coli and S. aureus (1.45 ± 0.26 mg/mL and 1.59 ± 0.12 mg/mL) compared to other synthesized materials. Also, in-vitro investigations were performed, and the MTT assay on the HFF cell line revealed that CS/SF/N-CQDs/α-TCP nanofiber could possess good biocompatibility. Interestingly, the scratch test proved that faster cell migration and proliferation occurred in the presence of CS/SF/N-CQDs/α-TCP (73 ± 3.12 %). Finally, we examined the wound healing ability of CS/SF/N-CQDs/α-TCP nanofiber using an animal model. The results confirmed that produced nanofiber could efficiently promote wound closure by 96.73 ± 1.25 % in 12 days. Histopathological analyses verified accelerated re-epithelization and well-structured epidermis in CS/SF/N-CQDs/α-TCP nanofiber-treated group. Based on our findings, the CS/SF/N-CQDs/α-TCP nanofiber with excellent antimicrobial properties is highly suitable for wound healing and skin tissue regeneration applications.

Antibacterial and antibiofilm mechanisms of carbon dots: a review

Due to the increasing bacterial resistance to conventional antibiotics, developing safe and effective approaches to combat infections caused by bacteria and biofilms has become an urgent clinical problem. Recently, carbon dots (CDs) have received great attention as a promising alternative to conventional antimicrobial agents due to their excellent antimicrobial efficacy and biocompatibility. Although CDs have been widely used in the field of antibacterial applications, their antibacterial and antibiofilm mechanisms have not been systematically discussed. This review provides a systematic overview on the complicated mechanisms of antibacterial and antibiofilm CDs based on recent development.

Carbon Dots for Killing Microorganisms: An Update since 2019

Frequent bacterial/fungal infections and occurrence of antibiotic resistance pose increasing threats to the public and thus require the development of new antibacterial/antifungal agents and strategies. Carbon dots (CDs) have been well demonstrated to be promising and potent antimicrobial nanomaterials and serve as potential alternatives to conventional antibiotics. In recent years, great efforts have been made by many researchers to develop new carbon dot-based antimicrobial agents to combat microbial infections. Here, as an update to our previous relevant review (C 2019, 5, 33), we summarize the recent achievements in the utilization of CDs for microbial inactivation. We review four kinds of antimicrobial CDs including nitrogen-doped CDs, metal-containing CDs, antibiotic-conjugated CDs, and photoresponsive CDs in terms of their starting materials, synthetic route, surface functionalization, antimicrobial ability, and the related antimicrobial mechanism if available. In addition, we summarize the emerging applications of CD-related antimicrobial materials in medical and industry fields. Finally, we discuss the existing challenges of antimicrobial CDs and the future research directions that are worth exploring. We believe that this review provides a comprehensive overview of the recent advances in antimicrobial CDs and may inspire the development of new CDs with desirable antimicrobial activities.