Carbon Dots Derived from Citric Acid and Glutathione as a Highly Efficient Intracellular Reactive Oxygen Species Scavenger for Alleviating the Lipopolysaccharide-Induced Inflammation in Macrophages

Fabrication and Efficient Interfacial Assembly of Bright Red-Emitting Carbon Quantum Dots for Security-Warning Textiles

Carbon quantum dots (CQDs) have attracted more attentions due to their multiple performances. However, the fabrication of long-wavelength emitting CQDs with aliphatic precursors still remains a challenge, mainly because it is difficult to generate large sp2 domains to reduce energy gap, which is not conducive to a redshift of the luminescence peak. Hereon, by regulating the pH of citric acid and thiourea mixture, a N, S co-doped CQD emitting bright red fluorescence at 635 nm is successfully fabricated through the solvothermal reaction under acidic condition, achieving a high quantum yield of 32.66%. Solvatochromic effects of the CQDs are discussed through theoretical equations and models, which confirm that the hydrogen-bonding interaction dominates the fluorescence emission behavior of CQDs in polar solvents. Besides, a feasible strategy is proposed to prepare an anti-counterfeiting textile via the deposition of red-emitting CQDs onto cotton fibers, through rapidly evaporating the preferred organic solvent. As expected, the CQD-decorated textiles exhibit encouraging anti-counterfeiting and security-warning functions, along with underwater and long-distance detectability, washability, and sun resistance. It is worth noting that the present work is innovative in realizing the application of red-light-emitting CQDs in the fields of security-warning textiles.

Carbon dots encapsulated zeolitic imidazolate framework-8 as an enhanced multi-antioxidant for efficient cytoprotection to HK-2 cells

Excessive reactive oxygen species (ROS) can lead to the imbalance of antioxidant system in the body and cause oxidative damage to cells. It is imperative to rationally design nanomaterials with high catalytic activity and multiple antioxidant activities. Here, line peppers-derived carbon dots (CDs) is encapsulated into zeolitic imidazolate framework-8 (CDs@ZIF-8) to achieve enhanced antioxidant activities for improved protective effect on cells. This nanosystem has a broad spectrum of antioxidant properties, which can effectively remove a variety of intracellular ROS and protect cells from ROS-induced death and cytoskeleton damage. In addition, CDs@ZIF-8 can reduce malondialdehyde (MDA) level and increase the enzyme activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx), as well as the level of glutathione (GSH) in human kidney proximal tubular epithelial cells (HK-2) cells. Mechanism studies demonstrated that CDs@ZIF-8 can up-regulate the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), allowing the regulation of antioxidant enzymes to further achieve antioxidant effect. Besides, CDs@ZIF-8 inhibited the secretion of proinflammatory cytokines. This work demonstrates that the constructed CDs@ZIF-8 with multi-antioxidant activity can act as a highly efficient intracellular ROS scavenger and provide potential for the application in related oxidative stress-induced diseases.

Multifunctional Nanosystem Based on Ultrasmall Carbon Dots for the Treatment of Acute Kidney Injury

Acute kidney injury (AKI) is a critical medical condition characterized by high morbidity and mortality rates. The pathogenesis of AKI potentially involves bursts of reactive oxygen species (ROS) bursts and elevated levels of inflammatory mediators. Developing nanoparticles (NPs) that downregulate ROS and inflammatory mediators is a promising approach to treat AKI. However, such NPs would be affected by the glomerular filtration barrier (GFB). Typically, NPs are too large to penetrate the glomerular system and reach the renal tubules─the primary site of AKI injury. Herein, we report the development of ultrasmall carbon dots-gallic acid (CDs-GA) NPs (∼5 nm). These NPs exhibited outstanding biocompatibility and were shown not only to efficiently eliminate ROS and alleviate oxidative stress but also to suppress the activation of the NF-κB signaling pathway, leading to a reduction in the release of inflammatory factors. Importantly, CDs-GA NPs were shown to be able to rapidly accumulate rapidly in the renal tissues without the need for intricate targeting strategies. In vivo studies demonstrated that CDs-GA NPs significantly reduced the incidence of cisplatin (CDDP)-induced AKI in mice, surpassing the efficacy of the small molecular drug, N-acetylcysteine. This research provides an innovative strategy for the treatment of AKI.

Activation of the PPARγ/NF-κB pathway by A-MPDA@Fe3O4@PVP via scavenging reactive oxygen species to alleviate hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) is a common pathological process during hepatectomy and liver transplantation and the two primary reasons for hepatic IRI are reactive oxygen species (ROS)-mediated oxidative stress and excessive inflammatory responses. Herein, a novel antioxidant nanodrug (A-MPDA@Fe3O4@PVP) is prepared by employing L-arginine-doped mesoporous polydopamine (A-MPDA) nanoparticles as the carrier for deposition of ultra-small ferric oxide (Fe3O4) nanoparticles and further surface modification with polyvinylpyrrolidone (PVP). A-MPDA@Fe3O4@PVP not only effectively reduces the aggregation of ultra-small Fe3O4, but also simultaneously replicates the catalytic activity of catalase (CAT) and superoxide dismutase (SOD). A-MPDA@Fe3O4@PVP with good antioxidant activity can rapidly remove various toxic reactive oxygen species (ROS) and effectively regulate macrophage polarization in vitro. In the treatment of hepatic IRI, A-MPDA@Fe3O4@PVP effectively alleviates ROS-induced oxidative stress, reduces the expression of inflammatory factors, and prevents apoptosis of hepatocytes through immune regulation. A-MPDA@Fe3O4@PVP can further protect liver tissue by activating the PPARγ/NF-κB pathway. This multiplex antioxidant enzyme therapy can provide new references for the treatment of IRI in organ transplantation and other ROS-related injuries such as fibrosis, cirrhosis, and bacterial and hepatic viral infection.

Functional carbon dots-hydrogel complex for selective antibacterial and detection applications

The carbon dots (CDs) with excellent optical properties and their hydrogel complex are of great significance in biomedicine, healthcare and biochemical detection fields. This paper reports the preparation of green-emitting CDs (MA-CDs) through one-step hydrothermal route with citric acid as reducing agent, L-malic acid as carbon source and N-(2-hydroxyethyl)ethylenediamine as nitrogen source. To expand its application in biology, MA-CDs were coupled with vancomycin to obtain multifunctional CDs (VMA-CDs). The prepared VMA-CDs exhibit selective antibacterial behavior to Gram-positive bacteria, and it could be used as a fluorescent probe to selectively label Staphylococcus aureus (S. aureus). Moreover, thanks to the excellent optical properties of VMA-CDs, it has been used as a fluorescent sensor to detect Au3+ with detection range of 6.50 nM-21.93 μM and detection limit 3.98 nM. By introducing the fluorescence of CDs as the reference signal, and VMA-CDs as a response signal, the hydrogel (V-SP) was prepared and realized the detection of Au3+ in microfluidics with assistance of a smartphone to collect and analyze data.

Biomass-derived carbon dots as fluorescent quantum probes to visualize and modulate inflammation

Quantum dots, which won the Nobel Prize in Chemistry, have recently gained significant attention in precision medicine due to their unique properties, such as size-tunable emission, high photostability, efficient light absorption, and vibrant luminescence. Consequently, there is a growing demand to identify new types of quantum dots from various sources and explore their potential applications as stimuli-responsive biosensors, biomolecular imaging probes, and targeted drug delivery agents. Biomass-waste-derived carbon quantum dots (CQDs) are an attractive alternative to conventional QDs, which often require expensive and toxic precursors, as they offer several merits in eco-friendly synthesis, preparation from renewable sources, and cost-effective production. In this study, we evaluated three CQDs derived from biomass waste for their potential application as non-toxic bioimaging agents in various cell lines, including human dermal fibroblasts, HeLa, cardiomyocytes, induced pluripotent stem cells, and an in-vivo medaka fish (Oryzias latipes) model. Confocal microscopic studies revealed that CQDs could assist in visualizing inflammatory processes in the cells, as they were taken up more by cells treated with tumor necrosis factor-α than untreated cells. In addition, our quantitative real-time PCR gene expression analysis has revealed that citric acid-based CQDs can potentially reduce inflammatory markers such as Interleukin-6. Our studies suggest that CQDs have potential as theragnostic agents, which can simultaneously identify and modulate inflammatory markers and may lead to targeted therapy for immune system-associated diseases.

Rapamycin functionalized carbon Dots: Target-oriented synthesis and suppression of vascular cell senescence

Suppression of vascular cell senescence is of great significance in preventing cardiovascular diseases such as hypertension and atherosclerosis. The oxidative stress damage caused by reactive oxygen species (ROS) can lead to cellular senescence. Rapamycin (Rapa) is well known to suppress cell senescence via mammalian target of rapamycin (mTOR) pathway. However, poor water solubility and lack of ROS scavenging ability limit the further development of Rapa. To improve the solubility of Rapa and endow with ROS scavenging ability, Rapa functionalized carbon dots (Rapa-CDs) are target-oriented synthesized via free radical polymerization combination with hydrothermal carbonization. Rapa-CDs improve the solubility of Rapa and show ROS scavenging abilities. The solubility of Rapa-CDs with 9.41 g is improved 3.6 × 104 times higher than that of Rapa (2.6 × 10-4 g). The half maximal inhibitory concentration (IC50) of Rapa-CDs toward hydroxyl radical (•OH) and 2,2-Diphenyl-1-picrylhydrazyl free radical (DPPH•) are 0.18 and 0.17 mg/mL, respectively. Rapa-CDs show anti-oxidative stress effect in HEVECs (Human Umbilical Vein Endothelial Cells) via reducing ROS levels by 87 %. Rapa-CDs alleviate HUVECs senescence by suppressing mTOR overactivation, attenuate the expression of P53, P21 and P16. The study demonstrates the target-oriented synthesis of drugs functionalized CDs with anti-senescence via dual-pathway of anti-oxidative stress and mTOR.

Oxidative stress-induced neurotoxicity of quantum dots and influencing factors

Quantum dots (QDs) have significant potential for treating and diagnosing CNS diseases. Meanwhile, the neurotoxicity of QDs has garnered attention. In this review, we focus on elucidating the mechanisms and consequences of CNS oxidative stress induced by QDs. First, we discussed the pathway of QDs transit into the brain. We then elucidate the relationship between QDs and oxidative stress from in vivo and in vitro studies. Furthermore, the main reasons and adverse outcomes of QDs leading to oxidative stress are discussed. In addition, the primary factors that may affect the neurotoxicity of QDs are analyzed. Finally, we propose potential strategies for mitigating QDs neurotoxicity and outline future perspectives for their development.

Molecular interactions between gelatin-derived carbon quantum dots and Apo-myoglobin: Implications for carbon nanomaterial frameworks

Carbon nanomaterials (CNMs), including carbon quantum dots (CQDs), have found widespread use in biomedical research due to their low toxicity, chemical tunability, and tailored applications. Yet, there exists a gap in our understanding of the molecular interactions between biomacromolecules and these novel carbon-centered platforms. Using gelatin-derived CQDs as a model CNM, we have examined the impact of this exemplar nanomaterial on apo-myoglobin (apo-Mb), an oxygen-storage protein. Intrinsic fluorescence measurements revealed that the CQDs induced conformational changes in the tertiary structure of native, partially unfolded, and unfolded states of apo-Mb. Titration with CQDs also resulted in significant changes in the secondary structural elements in both native (holo) and apo-Mb, as evidenced by the circular dichroism (CD) analyses. These changes suggested a transition from isolated helices to coiled-coils during the loss of the helical structure of the apo-protein. Infra-red spectroscopic data further underscored the interactions between the CQDs and the amide backbone of apo-myoglobin. Importantly, the CQDs-driven structural perturbations resulted in compromised heme binding to apo-myoglobin and, therefore, potentially can attenuate oxygen storage and diffusion. However, a cytotoxicity assay demonstrated the continued viability of neuroblastoma cells exposed to these carbon nanomaterials. These results, for the first time, provide a molecular roadmap of the interplay between carbon-based nanomaterial frameworks and biomacromolecules.

Designing of chitosan/gelatin based nanocomposite films integrated with Vachellia nilotica gum carbon dots for smart food packaging applications

Microbial growth and exposure to UV light is a persistent global concern resulting in food spoilage, therefore, smart packaging is crucial for the availability of safer and quality food. Present work describes fabrication of chitosan (CH) and gelatin (GL) based nanocomposite films by introducing green source, highly fluorescent Vachillia nilotica gum-derived carbon dots (VNG-CDs). The VNG-CDs and incorporated CH/GL nanocomposite films were characterized by UV-Visible, FTIR, XRD, SEM and TGA analysis. The FTIR and XRD data revealed that VNG-CDs, chitosan, gelatin, and glycerol are combined/interlinked to form homogeneous nanocomposite films. The inclusion of VNG-CDs to CS/GL-CDs nanocomposite film efficiently enhanced the thermal stability and improved mechanical properties. VNG-CDs added to films markedly blocked the ultraviolet light and their effectiveness improved as concentration of CDs increases, being >90 % in UVC (200-280 nm) region. The prepared CS/GL-CDs nanocomposite films manifested radical scavenging activity, reducing capability and also excellently inhibited growth of E. coli, K. pneumonia and S. aureus bacteria. The viability of CS/GL-CDs nanocomposite films examined using banana as a model fruit extending the storage time by two weeks. In conclusion, CH/GL films containing VNG-CDs can be developed into smart packaging materials with enhanced protection and antimicrobial properties.

Utilization of Nitrogen-Doped Graphene Quantum Dots to Neutralize ROS and Modulate Intracellular Antioxidant Pathways to Improve Dry Eye Disease Therapy

Purpose

Patients afflicted with dry eye disease (DED) experience significant discomfort. The underlying cause of DED is the excessive accumulation of ROS on the ocular surface. Here, we investigated the nitrogen doped-graphene quantum dots (NGQDs), known for their ROS-scavenging capabilities, as a treatment for DED.

Methods

NGQDs were prepared by using citric acid and urea as precursors through hydrothermal method. The antioxidant abilities of NGQDs were evaluated through: scavenging the ROS both extracellular and intracellular, regulating the nuclear factor-erythroid 2-related factor (Nrf2) antioxidant pathway of human corneal epithelial cells (HCECs) and their transcription of inflammation related genes. Furthermore, NGQDs were modified by Arg-Gly-Asp-Ser (RGDS) peptides to obtain RGDS@NGQDs. In vivo, both the NGQDs and RGDS@NGQDs were suspended in 0.1% Pluronic F127 (w/v) and delivered as eye drops in the scopolamine hydrobromide-induced DED mouse model. Preclinical efficacy was compared to the healthy and DPBS treated DED mice.

Results

These NGQDs demonstrated pronounced antioxidant properties, efficiently neutralizing free radicals and activating the intracellular Nrf2 pathway. In vitro studies revealed that treatment of H2O2-exposed HCECs with NGQDs induced a preservation in cell viability. Additionally, there was a reduction in the transcription of inflammation-associated genes. To prolong the corneal residence time of NGQDs, they were further modified with RGDS peptides and suspended in 0.1% Pluronic F127 (w/v) to create RGDS@NGQDs F127 eye drops. RGDS@NGQDs exhibited superior intracellular antioxidant activity even at low concentrations (10 μg/mL). Subsequent in vivo studies revealed that RGDS@NGQDs F127 eye drops notably mitigated the symptoms of DED mouse model, primarily by reducing ocular ROS levels.

Conclusion

Our findings underscore the enhanced antioxidant benefits achieved by modifying GQDs through nitrogen doping and RGDS peptide tethering. Importantly, in a mouse model, our novel eye drops formulation effectively ameliorated DED symptoms, thereby representing a novel therapeutic pathway for DED management.

Ce6-modified Fe ions-doped carbon dots as multifunctional nanoplatform for ferroptosis and photodynamic synergistic therapy of melanoma

BACKGROUND

Despite the higher sensitivity of melanoma towards ferroptosis and photodynamic therapy (PDT), the lack of efficient ferroptosis inducers and the poor solubility of photosensitizers restrict their synergistic strategies. With unique advantages, carbon dots (CDs) are expected to serve as innovative building blocks for combination therapy of cancers.

RESULTS

Herein, an ferroptosis/PDT integrated nanoplatform for melanoma therapy is constructed based on chlorin e6-modified Fe ions-doped carbon dots (Fe-CDs@Ce6). As a novel type of iron-carbon hybrid nanoparticles, the as-prepared Fe-CDs can selectively activate ferroptosis, prevent angiogenesis and inhibit the migration of mouse skin melanoma cells (B16), but have no toxicity to normal cells. The nano-conjugated structures facilitate not only the aqueous dispersibility of Ce6, but also the self-accumulation ability of Fe-CDs@Ce6 within melanoma area without requiring extra targets. Moreover, the therapeutic effects of Fe-CDs@Ce6 are synergistically enhanced due to the increased GSH depletion by PDT and the elevated singlet oxygen (1O2) production efficiency by Fe-CDs. When combined with laser irradiation, the tumor growth can be significantly suppressed by Fe-CDs@Ce6 through cyclic administration. The T2-weighted magnetic resonance imaging (MRI) capability of Fe-CDs@Ce6 also reveals their potentials for cancer diagnosis and navigation therapy.

CONCLUSIONS

Our findings indicate the multifunctionality of Fe-CDs@Ce6 in effectively combining ferroptosis/PDT therapy, tumor targeting and MRI imaging, which enables Fe-CDs@Ce6 to become promising biocompatible nanoplatform for the treatment of melanoma.

Carbon dots with selective fluorescence response to hydroxyl radical for sensitive detection of bleomycin

In this work, antioxidant carbon dots (ACDs) with high quantum yield (63.98%) were developed through a one-step strategy using citric acid, ethylenediamine, and L-arginine as sources. The ACDs demonstrated excellent in vitro antioxidant activity. Additionally, ACDs displayed a unique fluorescence response to hydroxyl radical (OH). Leveraging this distinctive feature, a selective and sensitive fluorescence-based sensor was developed for detecting bleomycin (BLM) in the presence of ferrous ions (Fe2+). The studies on the oxidizing properties and dynamic quenching mechanism of ACDs by OH suggested that OH reduced the contents of the amino and hydroxyl groups of ACDs, leading to a decreased electron cloud density of ACDs for dynamic quenching of ACDs. Under optimally refined conditions, the detection limit of this strategy for BLM was 0.58 μg/mL, with a linear range spanning from 1 to 24 μg/mL when employing ACDs as the probe. This fluorescence sensing strategy provides a promising method for the detection of BLM in clinical samples.

Target Functionalized Carbon Dot Nanozymes with Dual-Model Photoacoustic and Fluorescence Imaging for Visual Therapy in Atherosclerosis

Multifunctional nanomedicines have been used in atherosclerosis theranostics. Herein, phosphatidylserine-specific peptide CLIKKPF-functionalized carbon-dots nanozymes (pep-CDs) are reported for specific and efficient noninvasive theranostic of atherosclerosis. Surprisingly, pep-CDs are discovered to not only inherit the inherent properties of carbon dots (CDs), including deep-red fluorescence emission, photoacoustic response, and superoxide dismutase-like antioxidant, and anti-inflammatory activities but also possess the ability to target recognition on foam cells and target localization on plaques due to the specific interaction of CLIKKPF with phosphatidylserine on the membrane outer surface of foam cells. Furthermore, the target localization effect of pep-CDs vastly promotes the efficient accumulation of CDs in plaque, thus maximizing AS theranostic of CDs. Interestingly, pep-CDs could be developed to image plaque for monitoring atherosclerosis pathological progression in real-time resulting from the different content of foam cells. This work on the one hand proposes a simple and feasible strategy to construct theranostic nanoplatform employing only a single functional unit (i.e., multifunctional CDs) to simplify the fabrication procedure, on the other hand, highlights the advantages of the active target auxiliary mode for atherosclerosis theranostic applications.

Highly Antibacterial and Antioxidative Carbon Nanodots/Silk Fibroin Films for Fruit Preservation

The issues of fruit waste and safety resulting from rot have spurred a demand for improved packaging systems. Herein, we present highly antibacterial and antioxidative carbon nanodot/silk fibroin (CD/SF) films for fruit preservation. The films are composed of CDs and SF together with a small amount of glycerol via hydrogen bonding, exhibiting outstanding biosafety, transparency, and stretchability. The films effectively integrate key functionalities (atmosphere control, resistance to food-borne pathogens, and antioxidation properties) and can be manufactured in large sizes (about 20 × 30 cm), boasting a transmission rate of 13 183 cm3/m2·day for oxygen and 2860 g/m2·day for water vapor, favoring the preservation of fresh fruits. A convenient dip-coating method enables in situ fabrication of films with a thickness of approximately 14 μm directly on the fruits' surface providing comprehensive protection. Importantly, the films are washable and biodegradable. This work presents a promising technology to produce multifunctional and eco-friendly antibacterial packaging systems.

Fe-doped carbon dots: a novel biocompatible nanoplatform for multi-level cancer therapy

BACKGROUND

Tumor treatment still remains a clinical challenge, requiring the development of biocompatible and efficient anti-tumor nanodrugs. Carbon dots (CDs) has become promising nanomedicines for cancer therapy due to its low cytotoxicity and easy customization.

RESULTS

Herein, we introduced a novel type of "green" nanodrug for multi-level cancer therapy utilizing Fe-doped carbon dots (Fe-CDs) derived from iron nutrient supplement. With no requirement for target moieties or external stimuli, the sole intravenous administration of Fe-CDs demonstrated unexpected anti-tumor activity, completely suppressing tumor growth in mice. Continuous administration of Fe-CDs for several weeks showed no toxic effects in vivo, highlighting its exceptional biocompatibility. The as-synthesized Fe-CDs could selectively induce tumor cells apoptosis by BAX/Caspase 9/Caspase 3/PARP signal pathways and activate antitumoral macrophages by inhibiting the IL-10/Arg-1 axis, contributing to its significant tumor immunotherapy effect. Additionally, the epithelial-mesenchymal transition (EMT) process was inhibited under the treatment of Fe-CDs by MAPK/Snail pathways, indicating the capacity of Fe-CDs to inhibit tumor recurrence and metastasis.

CONCLUSIONS

A three-level tumor treatment strategy from direct killing to activating immunity to inhibiting metastasis was achieved based on "green" Fe-CDs. Our findings reveal the broad clinical potential of Fe-CDs as a novel candidate for anti-tumor nanodrugs and nanoplatform.

Green carbon dots derived from Atractylodes macrocephala: A potential nanodrug for treating alcoholic gastric ulcer

Alcoholic gastric ulcer is a common acute gastric injury disease. The drugs currently used in clinical practice not only cannot fundamentally treat gastric injury, but also have serious side effects. There is an urgent demand for the discovery of a mild drug to treat alcoholic gastric ulcers. Herein, the green carbon dots derived from charred Atractylodes macrocephala (CAM-CDs) were acquired and have been proven to be safe and effective in alleviating alcoholic gastric ulcers at an inhibition rate up to 60%. CAM-CDs can markedly attenuate the gastric mucosa damage such as mucosal defect, bleeding and inflammatory cell infiltration by histopathological examination. Serum and tissue inflammatory cytokine measurements, as well as immunohistochemistry results, indicate that its mechanism of gastric mucosal protection may involve the reduction of IL-1β and TNF-α by regulating inflammatory signaling pathway of the NF-κB/NLRP3 axis, as well as elevation of IL-10 levels. CAM-CDs also can reduce oxidative stress markers (MDA), increase PGE2 and mucin secretion (MUC5AC), and it simultaneously exerts slight inhibition of hydrogen potassium ATPase and pepsin activity to protect gastric mucosa, as well as increases the microbial diversity and regulates species composition of gut microbiota in rats with gastric ulcer. Our work provides a new perspective on utilizing carbon-based nanomaterials in the development of new mild drugs.

N-Acetyl-l-cysteine-Derived Carbonized Polymer Dots with ROS Scavenging via Keap1-Nrf2 Pathway Regulate Alveolar Bone Homeostasis in Periodontitis

Periodontitis is a type of chronic inflammatory oral disease characterized by the destruction of periodontal connective tissue and progressive alveolar bone resorption. As oxidative stress is the key cause of periodontitis in the early periodontal microenvironment, antioxidative therapy has been considered a viable treatment for periodontitis. However, more stable and effective reactive oxygen species (ROS)-scavenging nanomedicines are still highly needed due to the instability of traditional antioxidants. Herein, a new type of N-acetyl-l-cysteine (NAC)-derived red fluorescent carbonized polymer dots (CPDs) has been synthesized with excellent biocompatibility, which can serve as an extracellular antioxidant to scavenge ROS effectively. Moreover, NAC-CPDs can promote osteogenic differentiation in human periodontal ligament cells (hPDLCs) under H2 O2 stimulation. In addition, NAC-CPDs are capable of targeted accumulation in alveolar bone in vivo, reducing the level of alveolar bone resorption in periodontitis mice, as well as performing fluorescence imaging in vitro and in vivo. In terms of mechanism, NAC-CPDs may regulate redox homeostasis and promote bone formation in the periodontitis microenvironment by modulating the kelch-like ECH-associated protein l (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. This study provides a new strategy for the application of CPDs theranostic nanoplatform for periodontitis.

N-Acetylcysteine-Derived Carbon Dots for Free Radical Scavenging in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is associated with oxidative stress induced reactive oxygen species (ROS) dynamic equilibrium disturbance. Nanozymes, as nanomaterials with enzyme-like activity, can regulate intro-cellular ROS levels. In this study, a new carbon dots nanozyme, N-acetylcysteine-derived carbon dots (NAC-CDs), is developed and proved to be an ideal antioxidant and anti-senescent agent in IVDD management. The results confirmed the NAC-CDs have satisfactory biocompatibility and strong superoxide dismutase (250 U mg-1 ), catalase, glutathioneperoxidase-like activity, and total antioxidant capacity. Then, the powerful free radical scavenging and antioxidant ability of NAC-CDs are demonstrated in vitro as observing the reduced ROS in H2 O2 induced senescent nucleus pulposus cells (NPCs), in which the elimination efficiency of toxic ROS is more than 90%. NAC-CDs also maintained mitochondrial homeostasis and suppressed cellular senescence, subsequently inhibited the expression of inflammatory factors in NPCs. In vivo, evaluations of imaging and tissue morphology assessments suggested that disc height index, magnetic resonance imaging grade and histological score are significantly improved from the degenerative models when NAC-CDs is applied. In conclusion, the study developed a novel carbon dots nanozyme, which efficiently rescues IVDD from ROS induced NPCs senescence and provides a potential strategy in management of IVDD in clinic.

Doped Graphene Quantum Dots as Biocompatible Radical Scavenging Agents

Oxidative stress is proven to be a leading factor in a multitude of adverse conditions, from Alzheimer's disease to cancer. Thus, developing effective radical scavenging agents to eliminate reactive oxygen species (ROS) driving many oxidative processes has become critical. In addition to conventional antioxidants, nanoscale structures and metal-organic complexes have recently shown promising potential for radical scavenging. To design an optimal nanoscale ROS scavenging agent, we have synthesized ten types of biocompatible graphene quantum dots (GQDs) augmented with various metal dopants. The radical scavenging abilities of these novel metal-doped GQD structures were, for the first time, assessed via the DPPH, KMnO4, and RHB (Rhodamine B protectant) assays. While all metal-doped GQDs consistently demonstrate antioxidant properties higher than the undoped cores, aluminum-doped GQDs exhibit 60-95% radical scavenging ability of ascorbic acid positive control. Tm-doped GQDs match the radical scavenging properties of ascorbic acid in the KMnO4 assay. All doped GQD structures possess fluorescence imaging capabilities that enable their tracking in vitro, ensuring their successful cellular internalization. Given such multifunctionality, biocompatible doped GQD antioxidants can become prospective candidates for multimodal therapeutics, including the reduction of ROS with concomitant imaging and therapeutic delivery to cancer tumors.

Carbon Dots from Camelina Decorating hFGF2-Linked Camelina Lipid Droplets Cooperate to Accelerate Wound Healing

Constant oxidative stress at the wound site prolongs the inflammation period and slows down the proliferation stage. In order to shorten the inflammatory period meanwhile promote the proliferative activity of fibroblasts, herein, we synthesized novel camelina-derived carbon dots (CDs) decorating on hFGF2-linked camelina lipid droplets (CLD-hFGF2) to form nanobiomaterial CDs-CLD-hFGF2. The CDs-CLD-hFGF2 possesses peroxidase activity and has effective reactive oxygen species radical scavenging activity while achieving proliferation of NIH/3T3 cells under oxidative stress in vitro. In the acute wound model, wound healing after CDs-CLD-hFGF2 treatment reached nearly 92% on the 10th day, compared with 82% for CLD-hFGF2. Moreover, the wound site showed significant anti-inflammatory effects characterized by the downregulation of pro-inflammatory factors and the upregulation of anti-inflammatory factor levels. Overall, this study provided a strategy for the comprehensive utilization of camelina oil crops and revealed a promising future that could be considered an effective method for wound healing on the skin.

AND-Gated Nanosensor for Imaging of Glutathione and Apyrimidinic Endonuclease 1 in Cells, Animals, and Organoids

The development of a strategy for imaging of glutathione (GSH) and apurinic/apyrimidinic endonuclease 1 (APE1) in an organism remains challenging despite their significance in elaborating the correlated pathophysiological processes. Therefore, in this study, we propose a DNA-based AND-gated nanosensor for fluorescence imaging of the GSH as well as APE1 in living cells, animals, and organoids. The DNA probe is composed of a G-strand and A-strand. The disulfide bond in the G-strand is cleaved through a GSH redox reaction, and the hybridization stability between the G-strand and A-strand is decreased, leading to a conformational change of the A-strand. In the presence of APE1, the apurinic/apyrimidinic (AP) site in the A-strand is digested, producing a fluorescence signal for the correlated imaging of GSH and APE1. This nanosensor enables monitoring of the expression level change of GSH and APE1 in cells. Additionally, we illustrate the capability of this "dual-keys-and-locked" conceptual methodology in achieving specific tumor imaging when GSH and APE1 are present simultaneously (overexpressed GSH and APE1 in tumor cells) with improving tumor-to-normal tissue ratio in vivo. Furthermore, using this nanosensor, the GSH and APE1 also are visualized in organoids that recapitulate the phenotypic and functional traits of the original biological specimens. Overall, this study demonstrates the potential of our proposed biosensing technology in investigating the roles of various biological molecules involved in specific diseases.

Carbon Dots for the Treatment of Inflammatory Diseases: An Appraisal of In Vitro and In Vivo Studies

In recent decades, several studies demonstrating various applications of carbon dots (C-dots), including metal sensing, bioimaging, pH sensing, and antimicrobial activities, have been published. Recent developments have shifted this trend toward biomedical applications that target various biomarkers relevant to chronic diseases. However, relevant developments and research results regarding the anti-inflammatory properties of C-dots against inflammation-associated diseases have not been systematically reviewed. Hence, this review discusses the anti-inflammatory effects of C-dots in in vivo and in vitro models of LPS-induced inflammation, gout, cartilage tissue engineering, drug-induced inflammation, spinal cord injury, wound healing, liver diseases, stomach cancer, gastric ulcers, acute kidney and lung injury, psoriasis, fever or hypothermia, and bone tissue regeneration. The compiled studies demonstrate the promising potential of C-dots as anti-inflammatory agents for the development of new drugs.

Congo Red-Derived Carbon Dots: Simultaneously as Fluorescence Probe for Protein Aggregates, Inhibitor for Protein Aggregation, and Scavenger of Free Radicals

The pathological aggregation of some proteins is claimed to be highly related to several human diseases, such as β-amyloid 1-42 (Aβ₄₂ ) to Alzheimer's disease (AD), islet amyloid polypeptide, and insulin to type 2 diabetes mellitus. Therefore, it is in desperate need to develop effective methods for detection of protein aggregates and inhibition of abnormal aggregation. Herein, to construct all-in-one probe with both diagnosis and treatment potentials for protein aggregation diseases, Congo red (CR), a classical staining reagent with red fluorescence signal output for protein aggregates, is deliberately adopted to react with three different reductive carbon sources and ammonium persulfate to generate three CR-derived carbon dots (CDs). The obtained CDs exhibit the capabilities of turn-on red fluorescence imaging of protein aggregates, and/or inhibition of protein aggregation as well as scavenging of free radicals. Among them, CA-CDs, using citric acid as the reductive carbon source, demonstrate the superiority to the other two studied CDs in integrating all of these functions, and particularly exert excellent cytoprotection effect against toxic Aβ₄₂ species, possessing tremendous potential in diagnosis and treatment of AD for future study. The present study paves a new way to develop all-in-one CDs for the protein disease research.

Flammulina velutipes-derived carbon dots for fluorescence detection and imaging of hydroxyl radical

Monitoring hydroxyl radical (•OH) fluctuation is of great importance to study some relative pathological processes and to predict early diagnosis of diseases. Efficient •OH-responsive fluorescent sensors based on carbon dots (CDs) have been reported, but most researches have focused on the new strategies for the synthesis and doping of the CDs. Herein, a kind of biomass CDs (F-CDs) with Flammulina velutipes (F. velutipes) as the carbon source was prepared by a one-step hydrothermal method without any additional modification. The prepared F-CDs have remarkable sensitivity and selectivity and there is a good linear relationship from 0 to 12 μM with a low detection limit of 95 nM for quantitative •OH assay. With excitation-independent emission, favourable biocompatibility and low toxicity, the F-CDs can penetrate cell membranes as •OH-responsive fluorescent sensors to detect intracellular •OH in A549 cells stimulated by phorbol 12-myristate 13-acetate (PMA) and successfully monitor the •OH concentration levels by the corresponding fluorescence change. Given the combined benefits of the green and eco-friendly approach, the F-CDs show promise as novel theranostics tools for early detection and treatment of related diseases.

Renal-friendly Li+-doped carbonized polymer dots activate Schwann cell autophagy for promoting peripheral nerve regeneration

Activation of autophagy in Schwann cells (SCs) has emerged as a powerful trigger for peripheral nerve injury (PNI) repair. Lithium ion (Li⁺) is a classical autophagy activator that plays an important role in promoting axonal extension and remyelination. However, the therapeutic window of existing lithium drugs is extremely narrow, and the adverse side effects, especially nephrotoxicity, severely limit their therapeutic value. Herein, Li⁺-doped carbonized polymer dots (Li-CPDs) was synthesized for the first time to change the pharmacokinetics of Li⁺ from occupying epithelial sodium channels to lipid raft-mediated endocytosis. The in-vivo results confirmed that Li-CPDs could accelerate the removal of myelin debris and promote nerve regeneration via activating autophagy of SCs. Moreover, Li-CPDs exhibited almost no renal toxicity compared to that of raw lithium drugs. Thus, Li-CPDs could serve as a promising Li⁺-based nanomedicine for PNI regeneration with improved biosafety. STATEMENT OF SIGNIFICANCE: Regardless of the fact that lithium drugs have been used in treatment of mental illness such as manic depression, the systemic side effects and renal metabolic toxicity still seriously restrict their clinical application. Since Li⁺ and Na⁺ compete for ion channels of cell membrane, the cell entry efficiency is extremely low and easily affected by body fluctuations, which seems to be an unsolvable problem. Herein, we rationally exploited the endocytotic features of CPDs to develop Li-CPDs. The Li-CPDs improved the entry pathway, greatly reduced nephrotoxicity, and inherited the biological function of Li⁺ to activate autophagy for promoting peripheral nerve regeneration. Due to the BBB-crossing property of Li-CPDs, it also showed application prospects in future research on central nervous system diseases.

Hydrothermally Derived Green Carbon Dots from Broccoli Water Extracts: Decreased Toxicity, Enhanced Free-Radical Scavenging, and Anti-Inflammatory Performance

Biomass carbon dots (CDs) derived from natural plants possess the advantages of low cost, photostability, and excellent biocompatibility, with potential applications in chemical sensing, bioimaging, and nanomedicine. However, the development of biomass CDs with excellent antioxidant activity and good biocompatibility is still a challenge. Herein, we propose a hypothesis for enhancing the antioxidant capacity of biomass CDs based on precursor optimization, extraction solvent, and other conditions with broccoli as the biomass. Compared to broccoli water extracts, broccoli powders, and broccoli organic solvent extracts, CDs derived from broccoli water extracts (BWE-CDs) have outstanding antioxidant properties due to the abundant C═C, carbonyl, and amino groups on their surface. After optimization of the preparation condition, the obtained BWE-CDs exhibit excellent free-radical scavenging activity with an EC₅₀ of 68.2 μg/mL for DPPH^• and 22.4 μg/mL for ABTS^•+. Cytotoxicity and zebrafish embryotoxicity results indicated that BWE-CDs have lower cytotoxicity and better biocompatibility than that of CDs derived from organic solvents. In addition, BWE-CDs effectively scavenged reactive oxygen species (ROS) in A549 cells, 293T cells, and zebrafish, as well as eliminating inflammation in LPS-stimulated zebrafish. Mechanistic studies showed that the anti-inflammatory effect of BWE-CDs was dependent on the direct reaction of CDs with free radicals, the regulation of NO levels, and the upregulation of the expression of SOD and GPX-4. This work indicates that the antioxidant activity of CDs could be enhanced by using solvent extracts of biomass as precursors, and the obtained BWE-CDs exhibit characteristics of greenness, low toxicity, and excellent antioxidant and anti-inflammatory activities, which suggests the potential promising application of BWE-CDs as an antioxidant nanomedicine for inflammatory therapy.

Graphene quantum dots: A comprehensive overview

Because of their prospective applications and exceptional features, graphene quantum dots (GQDs) have gotten a lot of recognition as a new class of fluorescent carbon materials. One of the carbon family’s newest superstars is the GQD. Due to its exceptional optoelectrical qualities, it has sparked a lot of curiosity since its debut in 2008. Two of the most important traits are a band gap that is not zero, biocompatibility, and highly changeable characteristics. GQDs have several important characteristics. GQDs have shown potential in a variety of fields, for instance, catalysis, sensing, energy devices, drug delivery, bioimaging, photothermal, and photodynamic therapy. Because this area constantly evolves, it is vital to recognize emerging GQD concerns in the current breakthroughs, primarily since some specific uses and developments in the case of GQDs synthesis have not been thoroughly investigated through previous studies. The current results in the properties, synthesis, as well as benefits of GQDs are discussed in this review study. As per the findings of this research, the GQD’s future investigation is boundless, mainly if the approaching investigation focuses on purifying simplicity and environmentally friendly synthesis, as well as boosting photoluminescence quantum output and manufacturing output of GQDs.

Recent advances of antioxidant low-dimensional carbon materials for biomedical applications

As the primary cause of many tissue damage and diseases, reactive oxygen species (ROS) and reactive nitrogen species (RNS) are well known to be extremely harmful to a variety of biological components in cells including lipids, proteins and DNA. Numerous antioxidative nanomaterials have been artificially designed and rationally synthesized to protect cells from the oxidative damage caused by reactive oxygen species/reactive nitrogen species. Recent studies demonstrate that low dimensional carbon antioxidative nanomaterials have received a lot of attention owing to their tiny nanoscales and unique physicochemical property. As a result, a brief overview of recent advancements in antioxidant low-dimensional carbon materials is provided. Typically, carbon nanomaterials are classified according to their nanostructure dimensions, which are zero-dimension, one-dimension, and two-dimension. Last but not least, the challenges and perspectives of these high-performance low-dimensional materials in biomedical fields and further clinical usages are discussed as well.

Carbon dot-based nanomaterials: a promising future nano-platform for targeting tumor-associated macrophages

The tumor microenvironment (TME) is the internal environment that tumors depend on for survival and development. Tumor-associated macrophages (TAMs), as an important part of the tumor microenvironment, which plays a crucial role in the occurrence, development, invasion and metastasis of various malignant tumors and has immunosuppressant ability. With the development of immunotherapy, eradicating cancer cells by activating the innate immune system has yielded encouraging results, however only a minority of patients show a lasting response. Therefore, in vivo imaging of dynamic TAMs is crucial in patient-tailored immunotherapy to identify patients who will benefit from immunotherapy, monitor efficacy after treatment, and identify alternative strategies for non-responders. Meanwhile, developing nanomedicines based on TAMs-related antitumor mechanisms to effectively inhibit tumor growth is expected to become a promising research field. Carbon dots (CDs), as an emerging member of the carbon material family, exhibit unexpected superiority in fluorescence imaging/sensing, such as near infrared imaging, photostability, biocompatibility and low toxicity. Their characteristics naturally integrate therapy and diagnosis, and when CDs are combined with targeted chemical/genetic/photodynamic/photothermal therapeutic moieties, they are good candidates for targeting TAMs. We concentrate our discussion on the current learn of TAMs and describe recent examples of macrophage modulation based on carbon dot-associated nanoparticles, emphasizing the advantages of their multifunctional platform and their potential for TAMs theranostics.

Carbon dots derived from folic acid attenuates osteoarthritis by protecting chondrocytes through NF-κB/MAPK pathway and reprogramming macrophages

Background

Osteoarthritis (OA) is a common joint disorder worldwide which causes great health and economic burden. However, there remains an unmet goal to develop an effective therapeutic method to prevent or delay OA. Chondrocytes, as the major cells involved in OA progression, may serve as a promising therapeutic target.

Results

A kind of carbon dots (CDs) with excellent biocompatibility was fabricated from folic acid via hydrothermal method and could effectively attenuate osteoarthritis. It was demonstrated that CDs treatment could rescue IL1β-induced proinflammatory responses, oxidative stress, cartilage degeneration and extracellular matrix degradation. Moreover, CDs reprogrammed lipopolysaccharide (LPS)-induced macrophage inflammation and polarization. Conditioned medium (CM) from CDs-treated macrophages could attenuate IL1β-induced chondrocyte injury. Also, CM from CDs-treated chondrocytes had immunoregulatory functions on macrophages. Mechanistically, CDs inhibited the activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPK) signaling pathways in IL1β-stimulated chondrocytes. In vivo, anterior cruciate ligament transection (ACLT) mice model was adopted and it was indicated that intra-articular injection of CDs effectively delays OA pathogenesis.

Conclusions

Taken together, these findings indicated CDs could mediate OA via promoting cartilage repair and immunomodulating macrophages within local microenvironment, which may provide evidences for utilizing CDs as a novel nanomaterial for OA treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01681-6.

Colourful fluorescence-based carbon dots for tumour imaging-guided nanosurgery

Fluorescent-intraoperative navigation is a visual technique that allows surgeons to accurately distinguish malignant and normal tissues during surgery. It has the advantages of immediacy, high resolution, and high specificity. However, a single fluorescent source cannot provide sufficient surgical information. Multicolour carbon dots (CDs) are more suitable since they provide outstanding water solubility, photostability, and multicolour-fluorescence imaging. Here, we prepared an optical probe with CD-based multicolour-fluorescence imaging via a hydrothermal method. CDs can be endocytosed by tumour cells, and after intravenous injection, they can effectively accumulate at the tumour site. In a pancreatic cancer mouse model, we demonstrated the multicolour-fluorescence imaging capabilities of CDs, which aided the accurate resection of tumours under fluorescent-intraoperative navigation. Stereoscopic fluorescence microscopy imaging and H&E staining proved that the removed tissue belonged to the pancreatic tumour. This study emphasizes the potential of CDs for fluorescence-guided intraoperative resection and expands the application of CDs in biological fields.

Protein-Mimicking Nanoparticles in Biosystems

Proteins are essential elements for almost all life activities. The emergence of nanotechnology offers innovative strategies to create a diversity of nanoparticles (NPs) with intrinsic capacities of mimicking the functions of proteins. These artificial mimics are produced in a cost-efficient and controllable manner, with their protein-mimicking performances comparable or superior to those of natural proteins. Moreover, they can be endowed with additional functionalities that are absent in natural proteins, such as cargo loading, active targeting, membrane penetrating, and multistimuli responding. Therefore, protein-mimicking NPs have been utilized more and more often in biosystems for a wide range of applications including detection, imaging, diagnosis, and therapy. To highlight recent progress in this broad field, herein, representative protein-mimicking NPs that fall into one of the four distinct categories are summarized: mimics of enzymes (nanozymes), mimics of fluorescent proteins, NPs with high affinity binding to specific proteins or DNA sequences, and mimics of protein scaffolds. This review covers their subclassifications, characteristic features, functioning mechanisms, as well as the extensive exploitation of their great potential for biological and biomedical purposes. Finally, the challenges and prospects in future development of protein-mimicking NPs are discussed.

Glycine assists in efficient synthesis of herbal carbon dots with enhanced yield and performance

As a special type of biomass, herbal medicine often contains a variety of biologically active substances, and taking it as a carbon source, it is expected to produce various types of biologically functional carbon dots (CDs). However, there are few reports in this field, especially in achieving enhanced performance of CDs by improving the utilization efficiency of active substances in medicinal materials. In this work, by adding glycine as an auxiliary agent in the preparation of CDs from herbal medicine (Exocarpium Citri Grandis), the carboxyl and amino groups of the adjuvant provided more reactive sites, which greatly improved the yield of CDs (about 6 times). More importantly, the antioxidant and biological activities of herbal CDs were also improved. By controlling the functional groups of adjuvants, the effects of carboxyl and amino groups in adjuvants on the synthesis of herbal CDs were compared. The results reveal that both carboxyl and amino groups can react with the substances in the carbon source, and the influence of amino groups was greater. After adding glycine, the size of the CDs became larger, resulting from the more abundant functional groups on the carbon skeleton, which was the main reason for the improved performance of the CDs. Finally, the biological activity experiment demonstrated that CDs derived from Exocarpium Citri Grandis and glycine could greatly enhance the vitality of cells and activate immune cells, which are expected to be applied in the field of cell reproduction and biological immunity. The method proposed in this work provides a potential strategy for high-yield preparation of CDs from biomass.

Preparation of a Novel Carbon Dot/Polyvinyl Alcohol Composite Film and Its Application in Food Preservation

Carbon dots (CDs) were synthesized with the facile hydrothermal method to produce CDs/polyvinyl alcohol (PVA) active food packaging films. The CDs had a diameter ranging from 2.01 to 5.61 nm and were well-dispersed. The effects of different concentrations of CDs on mechanical strength, water resistance, morphology, optical, and thermal performance of the CDs/PVA films were discussed. The incorporation of CDs in the PVA film improved its mechanical properties, water resistance properties, UV blocking properties, and thermal stability and endowed the composite film with antioxidant and antimicrobial properties. The maximum scavenging rates of 2,2-diphenyl-1-picrylhydrazyl and ABTS free radicals by the 0.50% CDs/PVA film were 72.81 and 97.08%, respectively. The inhibition zone diameters of the 0.50% CDs/PVA solution against Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), and Escherichia coli (E. coli) were 9.52, 8.21, and 9.05 mm, respectively. Using the 0.50% CDs/PVA film as active packaging, the shelf life of banana, jujube, and fried meatballs was observed to be extended significantly. These results demonstrate the viability of the CDs/PVA composite film as a promising active food packaging material.

Citric Acid-Derived Carbon Quantum Dots Attenuate Paraquat-Induced Neuronal Compromise In Vitro and In Vivo

The potent environmental herbicide and weedicide paraquat is linked to neuromotor defects and Parkinson's disease (PD). We have evaluated the neuroprotective role of citric acid-sourced carbon quantum dots (Cit-CQDs) on paraquat-insulted human neuroblastoma-derived SH-SY5Y cell lines and on a paraquat-exposed nematode (Caenorhabditis elegans). Our data reveal that Cit-CQDs are able to scavenge free radicals in test tube assays and mitigate paraquat-elevated reactive oxygen species (ROS) levels in SH-SY5Y cells. Furthermore, Cit-CQDs protect the cell line from paraquat, which otherwise elicits cell death. Cit-CQDs-challenged nematodes demonstrate enhanced survival rates 72 h post-paraquat exposure compared to controls. Paraquat ablates dopamine (DA) neurons, which results in compromised locomotor function in nematodes. However, the neurons remained intact when the nematodes were incubated with Cit-CQDs prior to neurotoxicant exposure. The collective data suggest Cit-CQDs offer neuroprotection for cell lines and organisms from xenotoxicant-associated neuronal injury and death. The study suggests Cit-CQDs as a potentially viable green chemistry-synthesized, biobased nanomaterial for intervention in neurodegenerative disorders.

Immunotoxicity of Carbon-Based Nanomaterials, Starring Phagocytes

In the field of science, technology and medicine, carbon-based nanomaterials and nanoparticles (CNMs) are becoming attractive nanomaterials that are increasingly used. However, it is important to acknowledge the risk of nanotoxicity that comes with the widespread use of CNMs. CNMs can enter the body via inhalation, ingestion, intravenously or by any other route, spread through the bloodstream and penetrate tissues where (in both compartments) they interact with components of the immune system. Like invading pathogens, CNMs can be recognized by large numbers of receptors that are present on the surface of innate immune cells, notably monocytes and macrophages. Depending on the physicochemical properties of CNMs, i.e., shape, size, or adsorbed contamination, phagocytes try to engulf and process CNMs, which might induce pro/anti-inflammatory response or lead to modulation and disruption of basic immune activity. This review focuses on existing data on the immunotoxic potential of CNMs, particularly in professional phagocytes, as they play a central role in processing and eliminating foreign particles. The results of immunotoxic studies are also described in the context of the entry routes, impacts of contamination and means of possible elimination. Mechanisms of proinflammatory effect depending on endocytosis and intracellular distribution of CNMs are highlighted as well.

A multi-target theranostic nano-composite against Alzheimer's disease fabricated by conjugating carbon dots and triple-functionalized human serum albumin

The complex pathogenesis of Alzheimer's disease (AD) involves the aggregation and accumulation of amyloid β-protein (Aβ) as well as elevated levels of reactive oxygen species (ROS), which requires the development of comprehensive diagnostic and therapeutic interventions. In this work, a multifunctional theranostic nano-composite (HSA-BFP@CDs) is constructed by conjugating triple-functionalized human serum albumin (HSA-BFP) as a theranostic agent targeting Aβ and carbon dots (CDs) as an ROS scavenger. HSA-BFP@CDs exhibits a fluorescence "off-on" effect at 700 nm upon interaction with Aβ aggregates, showing the capability for detection of Aβ plaques and potential for early diagnosis of AD. Besides, HSA-BFP@CDs effectively inhibits the aggregation of Aβ, increasing the viability of Aβ-treated cells from 74% to over 95% at 100 µg/mL. Moreover, multiple ROS, including hydroxyl radicals, superoxide radicals, hydrogen peroxide, and Aβ-Cu²⁺-induced-ROS, can be scavenged by HSA-BFP@CDs, thus resulting in the mitigation of cellular oxidative damages. Experiments with the AD model of Caenorhabditis elegans further demonstrate the multifunctionality of HSA-BFP@CDs in imaging amyloid plaques, reducing Aβ deposition, and relieving oxidative stress in vivo, showing the prospect for Aβ- and ROS-targeted AD diagnosis and treatment. This work provided new insight into the design of protein-carbon dots conjugate and the development of multi-target therapy of AD. STATEMENT OF SIGNIFICANCE: Alzheimer's disease (AD) is the most common form of dementia, which currently affects over 55 million people worldwide. Due to the complex pathogenesis of AD involving amyloid β-protein (Aβ) aggregation as well as elevated levels of reactive oxygen species (ROS), it is highly desired to develop comprehensive diagnostic and therapeutic interventions. In this paper, we fabricated a multifunctional theranostic nano-composite (HSA-BFP@CDs) via the conjugation of triple-functionalized human serum albumin (HSA-BFP) and carbon dots (CDs). The multifunctionality of HSA-BFP@CDs for efficient detection of Aβ aggregates and inhibition of Aβ aggregation as well as scavenging of ROS was demonstrated, demonstrating the potential of the protein-carbon dots conjugate for the multi-target therapy of AD.

CdSe magic-sized quantum dots attenuate reactive oxygen species generated by neutrophils and macrophages with implications in experimental arthritis

The biological applicability of nanomaterials has been limited due to cytotoxicity. Studies have described the effects of nanomaterials on different tissues and cell types, but their actions on immune cells are less elucidated. This study describes unprecedented in vitro and in vivo antioxidant activities of cadmium selenide magic-sized quantum dots (CdSe MSQDs) with implications on rheumatoid arthritis. While the generation of ROS induced by nanomaterials is linked to cytotoxicity, we found that CdSe MSQDs reduced ROS production by neutrophils and macrophages following opsonized-zymosan stimuli, and we did not find cytotoxic effects. Interestingly, inherent antioxidant properties of CdSe MSQDs were confirmed through DPPH, FRAP, and ORAC assays. Furthermore, CdSe MSQDs reduced ROS levels generated by infiltrating leukocytes into joints in experimental model of rheumatoid arthritis. Briefly, we describe a novel application of CdSe MSQDs in modulating the inflammatory response in experimental rheumatoid arthritis through an unexpected antioxidant activity.

Partial carbonization of quercetin boosts the antiviral activity against H1N1 influenza A virus

Inflenza A viruses (IAVs) are highly transmissible and pathogenic Orthomyxoviruses, which have led to worldwide outbreaks and seasonal pandemics of acute respiratory diseases, causing serious threats to public health. Currently used anti-influenza drugs may cause neurological side effects, and they are increasingly less effective against mutant strains. To help prevent the spread of IAVs, in this work, we have developed quercetin-derived carbonized nanogels (CNGs_Qur) that display potent viral inhibitory, antioxidative, and anti-inflammatory activities. The antiviral CNGs_Qur were synthesized by mild carbonization of quercetin (Qur), which successfully preserved their antioxidative and anti-inflammatory properties while also contributed enhanced properties, such as water solubility, viral binding, and biocompatibility. Antiviral assays of co-treatment, pre-treatment, and post-treatment indicate that CNGs_Qur interacts with the virion, revealing that the major antiviral mechanism resulting in the inhibition of the virus is by their attachment on the cell surface. Among them, the selectivity index (SI) of CNGs_Qur270 (>857.1) clearly indicated its great potential for clinical application in IAVs inhibition, which was much higher than that of pristine quercetin (63.7) and other clinical drugs (4-81). Compared with quercetin at the same dose, the combined effects of viral inhibition, antioxidative and anti-inflammatory activities impart the superior therapeutic effects of CNGs_Qur270 aerosol inhalation in the treatment of IAVs infection, as evidenced by a mouse model. These CNGs_Qur effectively prevent the spread of IAVs and suppress virus-induced inflammation while also exhibiting good in vivo biocompatibility. CNGs_Qur shows much promise as a clinical therapeutic agent against infection by IVAs.

A general carbon dot-based platform for intracellular delivery of proteins

The shortcomings of proteins, such as poor stability in biological environments, the impermeability of the membrane and the susceptibility to enzymolysis, restrict their potential applications. Therefore, constructing universal nanocarriers for intracellular delivery of a variety of proteins remains a great challenge. In this work, gallic acid (GA) and L-lysine were used as starting materials to synthesize carbon dots (CDs). The CDs were used as carriers to interact with bovine serum albumin (BSA), enhanced green fluorescent protein (EGFP) and glucose oxidase (GOx) via supramolecular interaction to construct CDs-protein nanocomposites CDs-BSA, CDs-EGFP and CDs-GOx. Furthermore, CDs-EGFP and CDs-GOx can achieve intracellular protein delivery and maintain 89% of the biological activity of GOx. In this work, the latency of CDs is projected as a universal platform for effective intracellular delivery of proteins.

Mandelic acid appended chiral gels as efficient templates for multicolour circularly polarized luminescence

Mandelic acid is a medicinally important chiral molecule that is widely used as a vital component in antibiotics, antiseptics and cosmetics. While the medicinal properties of mandelic acid are well known, its aggregation and gelation characteristics, which are crucial to finding applications as cosmetics and ointments, are least explored. We have designed and synthesized a pair of mandelic acid derivatives and investigated their aggregation properties in binary solvent mixtures. The compounds undergo self-assembly through various noncovalent interactions, leading to the formation of robust chiral gels. Strong birefringence could be visualised from the individual structures constituting the gel. The large rod-like chiral structures are utilized as efficient templates for the assembly of ultra-small luminescent achiral carbon nanodots. The transfer of optical activity from the chiral host matrix to the fluorescent guest nanoparticles resulted in the generation of circularly polarized luminescence signals from the hybrid nanocomposites. The use of blue, green and red-emitting nanodots led to the fabrication of multicolour chiral light-emitting materials capable of covering the entire visible range. Considering the numerous medicinal benefits offered by mandelic acid and carbon nanodots, the materials constituting the nanocomposites, the distinct dimensions presented in the current work open new avenues for chiral light emitting materials to be used in biomedical research.

Application of carbon dots in food preservation: a critical review for packaging enhancers and food preservatives

Carbon dots (CDs) have two unique advantages: one is ease of synthesis at low price, the other is desirable physical and chemical properties, such as ultra-small size, abundant surface functional groups, nontoxic/low-toxicity, good biocompatibility, excellent antibacterial and antioxidant activities etc. These advantages provide opportunities for the development of new food packaging enhancers and food preservatives. This paper systematically reviews the studies of CDs used to strengthen the physical properties of food packaging, including strengthen mechanical strength, ultraviolet (UV) barrier properties and water barrier properties. It also reviews the researches of CDs used to fabricate active packaging with antioxidant and/or antibacterial properties and intelligent packaging with the capacity of sensing the freshness of food. In addition, it analyzes the antioxidant and antibacterial properties of CDs as preservatives, and discusses the effect of CDs applied as coating agents and nano-level food additives for extension the shelf life of food samples. It also provides a brief review on the security and the release behavior of CDs.

A metal free catalyst for efficient and stable one-step photocatalytic production of pure hydrogen peroxide

Hydrogen peroxide (H2O2) is widely used as a green and clean energy. The pure H2O2 solution has attracted much attention for its special applications in many fields. Photocatalytic water splitting...

Eco-friendly functionalization of hexagonal boron nitride nanosheets with carbon dots towards reinforcement of the protective performance of water-borne epoxy coatings

A h-BN@CDs/WEP coating shows superior corrosion protection under intact or damaged status owing to the improved barrier properties and interfacial bonding of the coating.

Antioxidant Enzymes Sequestered within Lipid-Polymer Hybrid Nanoparticles for the Local Treatment of Inflammatory Bowel Disease

The local treatment of inflammatory bowel disease (IBD) by enzyme therapeutics is challenging owing to hostile environments in the gastrointestinal tract, leading to the hydrolysis and enzymatic degradation of labile proteins. In this study, safe and efficient local drug delivery systems were developed by antioxidant superoxide dismutase (SOD) sequestered within lipid-polymer hybrid nanoparticles through sequential self-assembly processes. Interestingly, we found that the sequestered SOD exhibited long-term enzymatic stability and comparable biological activity to the enzymes in the native form, probably owing to particle encapsulation providing a physical barrier to prevent the enzymolysis of proteins. We demonstrated that nanoparticle-based local drug delivery systems showed excellent mucus-penetrating ability and inflammation-targeting properties, owing to the particle surface with a poly(ethylene glycol) (PEG) coating and folate functionalization, thus improving mucosal retention time and drug delivery efficiency within the colorectal region. Furthermore, SOD-containing lipid-polymer hybrid nanoparticles could effectively mitigate inflammatory responses by regulating the secretion of inflammation-associated cytokines, thus increasing therapeutic outcomes in colitis mice through intrarectal administration. The findings indicated that antioxidant enzymes sequestered within lipid-polymer hybrid nanoparticles might be potential enzyme therapeutics for the local treatment of some inflammatory diseases in the near future.

Defective Ag-In-S/ZnS quantum dots: an oxygen-derived free radical scavenger for mitigating macrophage inflammation

Oxidative stress plays an important role in the development of inflammatory diseases including allergy, heart disease, diabetes and cancer. Nanomaterial-mediated antioxidant therapy is regarded as a promising strategy to treat oxidative stress-mediated inflammation. Herein, defective Ag-In-S/ZnS quantum dots (AIS/ZnS QDs) with oxygen-derived radical-scavenging capabilities are developed. Owing to their intrinsic defects and abundant surface functional groups, these quantum dots exhibit excellent oxygen-derived free radical removal efficiency in vitro. In macrophages, AIS/ZnS QDs can eliminate intracellular excessive ROS stimulated by either H₂O₂ or lipopolysaccharide (LPS), thus can effectively protect macrophages against ROS-induced oxidative injury. Moreover, in the model of LPS-triggered macrophage inflammation, they exhibit benign anti-inflammatory ability by inhibiting the expression of related proinflammatory cytokines (e.g., TNF-α and IL-6). These findings indicate that AIS/ZnS QDs hold great potential for the treatment of ROS-related inflammatory disorders.

Carbon Dots: Classification, Properties, Synthesis, Characterization, and Applications in Health Care-An Updated Review (2018-2021)

Carbon dots (CDs) are usually smaller than 10 nm in size, and are meticulously formulated and recently introduced nanomaterials, among the other types of carbon-based nanomaterials. They have gained significant attention and an incredible interest in the field of nanotechnology and biomedical science, which is merely due to their considerable and exclusive attributes; including their enhanced electron transferability, photobleaching and photo-blinking effects, high photoluminescent quantum yield, fluorescence property, resistance to photo-decomposition, increased electrocatalytic activity, good aqueous solubility, excellent biocompatibility, long-term chemical stability, cost-effectiveness, negligible toxicity, and acquaintance of large effective surface area-to-volume ratio. CDs can be readily functionalized owing to the abundant functional groups on their surfaces, and they also exhibit remarkable sensing features such as specific, selective, and multiplex detectability. In addition, the physico-chemical characteristics of CDs can be easily tunable based on their intended usage or application. In this comprehensive review article, we mainly discuss the classification of CDs, their ideal properties, their general synthesis approaches, and primary characterization techniques. More importantly, we update the readers about the recent trends of CDs in health care applications (viz., their substantial and prominent role in the area of electrochemical and optical biosensing, bioimaging, drug/gene delivery, as well as in photodynamic/photothermal therapy).