Carbon Dots for In Vivo Bioimaging and Theranostics

The investigation of the interaction between fluorescent carbon dots labeling silk fibroin using a fluorescence microscope-surface plasmon resonance system

The use of fluorescent carbon dots (CDs) as highly precise biolabeling probes has been widespread in the fields of live cell imaging and protein labeling due to their small size and excellent photoluminescence ability to accurately target specific molecules with surface chemical properties. However, there was a lack of research on the interaction between CDs and labeled molecules. In this work, we presented a novel investigation strategy, the fluorescence microscopy-surface plasmon resonance (FM-SPR) system, which combined the use of fluorescence microscopy and wavelength modulation surface plasmon resonance to study the interaction between CDs and labeled molecules in real-time. Using this system, simultaneously recorded the SPR signals and the fluorescence images on the surface of the FM-SPR sensor chip. We observed the dynamic curve and fluorescence images of the interaction between green emissive nitrogen-doped carbon dots (N-CDs) and silk fibroin (SF) in real-time. The kinetic parameters, the quantitative analysis, and the investigation of the binding could be achieved. The results showed a strong linear relationship between the change in SPR signals and the concentration of N-CDs, with a linear coefficient of 0.99913. The linear detection range was 2.5 μg/mL-100 μg/mL, and the real lowest detection limit reached 0.5 μg/mL. Additionally, the green fluorescence points in the imaging region on the FM-SPR sensor chip increased with the concentration of N-CDs, which was consistent with the change in SPR signals. Using this system we also acquired the association rate and dissociation rate of N-CDs to SF which were 2.65 × 10-5/s and 1.52 × 10-5/s, respectively. This demonstrated the effectiveness of our method in quantitatively analyzing SF labeled with N-CDs.

Carbonization of quercetin into nanogels: a leap in anticoagulant development

Quercetin, a flavonoid abundantly found in onions, fruits, and vegetables, is recognized for its pharmacological potential, especially for its anticoagulant properties that work by inhibiting thrombin and coagulation factor Xa. However, its clinical application is limited due to poor water solubility and bioavailability. To address these limitations, we engineered carbonized nanogels derived from quercetin (CNGsQur) using controlled pyrolysis and polymerization techniques. This led to substantial improvements in its anticoagulation efficacy, water solubility, and biocompatibility. We generated a range of CNGsQur by subjecting quercetin to varying pyrolytic temperatures and then assessed their anticoagulation capacities both in vitro and in vivo. Coagulation metrics, including thrombin clotting time (TCT), activated partial thromboplastin time (aPTT), and prothrombin time (PT), along with a rat tail bleeding assay, were utilized to gauge the efficacy. CNGsQur showed a pronounced extension of coagulation time compared to uncarbonized quercetin. Specifically, CNGsQur synthesized at 270 °C (CNGsQur270) exhibited the most significant enhancement in TCT, with a binding affinity to thrombin exceeding 400 times that of quercetin. Moreover, variants synthesized at 310 °C (CNGsQur310) and 290 °C (CNGsQur290) showed the most substantial delays in PT and aPTT, respectively. Our findings indicate that the degree of carbonization significantly influences the transformation of quercetin into various CNGsQur forms, each affecting distinct coagulation pathways. Additionally, both intravenous and oral administrations of CNGsQur were found to extend rat tail bleeding times by up to fivefold. Our studies also demonstrate that CNGsQur270 effectively delays and even prevents FeCl3-induced vascular occlusion in a dose-dependent manner in mice. Thus, controlled pyrolysis offers an innovative approach for generating quercetin-derived CNGs with enhanced anticoagulation properties and water solubility, revealing the potential for synthesizing self-functional carbonized nanomaterials from other flavonoids for diverse biomedical applications.

Metal-organic framework (MOF)/C-dots and covalent organic framework (COF)/C-dots hybrid nanocomposites: Fabrications and applications in sensing, medical, environmental, and energy sectors

Developing new hybrid materials is critical for addressing the current needs of the world in various fields, such as energy, sensing, health, hygiene, and others. C-dots are a member of the carbon nanomaterial family with numerous applications. Aggregation is one of the barriers to the performance of C-dots, which causes luminescence quenching, surface area decreases, etc. To improve the performance of C-dots, numerous matrices including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and polymers have been composited with C-dots. The porous crystalline structures, which are constituents of metal nodes and organic linkers (MOFs) or covalently attached organic units (COFs) provide privileged features such as high specific surface area, tunable structures, and pore diameters, modifiable surface, high thermal, mechanical, and chemical stabilities. Also, the MOFs and COFs protect the C-dots from the environment. Therefore, MOF/C-dots and COF/C-dots composites combine their features while retaining topological properties and improving performances. In this review, we first compare MOFs with COFs as matrices for C-dots. Then, the recent progress in developing hybrid MOFs/C-dots and COFs/C-dots composites has been discussed and their applications in various fields have been explained briefly.

Photothermal therapy: a novel potential treatment for prostate cancer

Prostate cancer (PCa) is a leading cause of cancer-related death in men, and most PCa patients treated with androgen deprivation therapy will progress to metastatic castration-resistant prostate cancer (mCRPC) due to the lack of efficient treatment. Recently, lots of research indicated that photothermal therapy (PTT) was a promising alternative that provided an accurate and efficient prostate cancer therapy. A photothermic agent (PTA) is a basic component of PPT and is divided into organic and inorganic PTAs. Besides, the combination of PTT and other therapies, such as photodynamic therapy (PDT), immunotherapy (IT), chemotherapy (CT), etc., provides an more efficient strategy for PCa therapy. Here, we introduce basic information about PTT and summarize the PTT treatment strategies for prostate cancer. Based on recent works, we think the combination of PPT and other therapies provides a novel possibility for PCa, especially CRPC clinical treatment.

CDs-ICG@BSA nanoparticles for excellent phototherapy and in situ bioimaging

For the diagnosis and treatment of cancer, a great challenge is the fabrication of straightforward, non-toxic, multifunctional green nanomaterials. In this study, carbon quantum dots self-assembled with indocyanine green dye at bovine serum albumin for phototherapy and in situ bioimaging are produced by a flexible hydrothermal method. We find that the synthesized nanoparticles have high tumor photothermal therapeutic activity when exposed to 808 nm light, with a photothermal conversion efficiency up to 61 %. The phototoxicity study revealed the excellent phototherapy of the nanoparticles mainly arises from photothermal therapeutic effect other than photodynamic therapy effect. Simultaneously, it allows biological imaging in the visible and near-infrared ranges because of the significant absorption at 365 nm and 840 nm. The current work offers a simple, environmentally friendly, and reasonable method for developing photothermal drugs with a high photothermal conversion efficiency in the near-infrared region, as well as good biosafety for multifunctional nanomaterials for bioimaging tumor diagnosis and direct phototherapy.

Nonmetallic graphite for tumor magnetic hyperthermia therapy

Magnetic hyperthermia therapy (MHT) has garnered immense interest due to its exceptional spatiotemporal specificity, minimal invasiveness and remarkable tissue penetration depth. Nevertheless, the limited magnetothermal heating capability and the potential toxicity of metal ions in magnetic materials based on metallic elements significantly impede the advancement of MHT. Herein, we introduce the concept of nonmetallic materials, with graphite (Gra) as a proof of concept, as a highly efficient and biocompatible option for MHT of tumors in vivo for the first time. The Gra exhibits outstanding magnetothermal heating efficacy owing to the robust eddy thermal effect driven by its excellent electrical conductivity. Furthermore, being composed of carbon, Gra offers superior biocompatibility as carbon is an essential element for all living organisms. Additionally, the Gra boasts customizable shapes and sizes, low cost, and large-scale production capability, facilitating reproducible and straightforward manufacturing of various Gra implants. In a mouse tumor model, Gra-based MHT successfully eliminates the tumors at an extremely low magnetic field intensity, which is less than one-third of the established biosafety threshold. This study paves the way for the development of high-performance magnetocaloric materials by utilizing nonmetallic materials in place of metallic ones burdened with inherent limitations.

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.

Multifunctionalized Carbon Dots as an Active Nanocarrier for Drug Delivery to the Glioblastoma Cell Line

Nanoparticle-based nanocarriers represent a viable alternative to conventional direct administration in cancer cells. This advanced approach employs the use of nanotechnology to transport therapeutic agents directly to cancer cells, thereby reducing the risk of damage to healthy cells and enhancing the efficacy of treatment. By approving nanoparticle-based nanocarriers, the potential for targeted, effective treatment is greatly increased. The so-called carbon-based nanoparticles, or carbon dots, have been hydrothermally prepared and initiated by a polymerization process. We synthesized and characterized nanoparticles of 2-acrylamido-2-methylpropanesulfonic acid, which showed biocompatibility with glioblastoma cells, and further, we tested them as a carrier for the drug riluzole. The obtained nanoparticles have been extensively characterized by techniques to obtain the exact composition of their surface by using Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) spectroscopy, as well as cryo-transmission electron microscopy. We found that the surface of the synthesized nanoparticles (NPs) is covered mainly by sulfonated, carboxylic, and substituted amide groups. These functional groups make them suitable as carriers for drug delivery in cancer cells. Specifically, we have successfully utilized the NPs as a delivery system for the drug riluzole, which has shown efficacy in treating glioblastoma cancer cells. The effect of nanoparticles as carriers for the riluzole system on glioblastoma cells was studied using live-cell synchrotron-based FTIR microspectroscopy to monitor in situ biochemical changes. After applying nanoparticles as nanocarriers, we have observed changes in all biomacromolecules, including the nucleic acids and protein conformation. These findings provide a strong foundation for further exploration into the development of targeted treatments for glioblastoma.

Red/NIR-I-Fluorescence Carbon Dots Based on Rhein with Active Oxygen Scavenging and Colitis Targeting for UC Therapeutics

Ulcerative colitis (UC) is a chronic inflammatory disease with uncontrolled inflammation and demage to the intestinal barrier. Rhein, a bioactive compound in traditional Chinese medicine, has anti-inflammatory and intestinal repair effect. However, their clinical application is limited by their hydrophobicity and poor bioavailability. L-arginine, as a complement to NO, has synergistic and attenuating effects. In this paper, red/NIR-I fluorescent carbon dots based on rhein and doped with L-arginine (RA-CDs), which are synthesized by a hydrothermal process without any organic solvents, are reported. RA-CDs preserve a portion of the functional group of the active precursor, increase rhein solubility, and emit red/NIR-I light for biological imaging. In vitro experiments show that RA-CDs scavenge excessive reactive oxygen species (ROS), protect cells from oxidative stress, and enable the fluorescence imaging of inflamed colons. In a DSS-induced UC mouse model, both delayed and prophylactic treatment with RA-CDs via intraperitoneal and tail vein injections alleviate UC severity by reducing intestinal inflammation and restoring the intestinal barrier. This study highlights a novel strategy for treating and imaging UC with poorly soluble small-molecule drugs.

Impact of nanotechnology at heterogeneous interphases @ Sustainability

The 21st century information and communication industries have played the pivotal role of bio-sensing technologies, refining privacy policies for human performance, facilitating scientific innovation, shaping e-governance, and reinforcing public confidence using nanotechnology. Human body is a thermodynamic heat engine in providing effective mechanical work as a function of psyche, conventional fuel transformation into enriched protein meal, and balancing of work-life fulcrum. The triboelectric effect of rubbing surfaces, interfaces, and interphases is invincible from the large field of the planet to nanodomains.

Tumor diagnosis using carbon-based quantum dots: Detection based on the hallmarks of cancer

Carbon-based quantum dots (CQDs) have been shown to have promising application value in tumor diagnosis. Their use, however, is severely hindered by the complicated nature of the nanostructures in the CQDs. Furthermore, it seems impossible to formulate the mechanisms involved using the inadequate theoretical frameworks that are currently available for CQDs. In this review, we re-consider the structure-property relationships of CQDs and summarize the current state of development of CQDs-based tumor diagnosis based on biological theories that are fully developed. The advantages and deficiencies of recent research on CQDs-based tumor diagnosis are thus explained in terms of the manifestation of nine essential changes in cell physiology. This review makes significant progress in addressing related problems encountered with other nanomaterials.

Carbon dots derived from metformin by electrochemical synthesis with broad-spectrum antibacterial properties

Due to the advantages of good aqueous dispersion and biocompatibility, carbon dots (CDs) are promising candidates for a wide range of applications in the biological field. Notably, CDs derived from biosafe organic precursors will contribute both new types of CDs and new bioactivities. Herein, metformin (MET), a first-line drug for the treatment of type II diabetes, was selected as an organic precursor to fabricate a new type of CDs, namely, semi-carbonized MET (MCDs). These MCDs derived from MET possess a completely new antibacterial activity against Staphylococcus aureus (SA) and Escherichia coli (E. coli) compared with that of MET and achieve complete antibacterial activity at 200 μg mL-1. The broad-spectrum antibacterial mechanism of MCDs involves two aspects. For the Gram-positive bacteria SA, MCDs mainly affect the transport of nutrients by adsorbing onto the surface of bacteria, thereby inhibiting bacterial growth. For the Gram-negative bacteria E. coli, MCDs can easily pass through their thin cell walls and stimulate the bacteria to produce excess ROS, eventually leading to the death of the bacteria. This work may open a new way for the future design and development of CDs prepared from biosafe organic precursors with specific functions.

Wavelength-Tuneable Fluorescent Carbon Dots for Nucleic Acid Imaging

Nucleic acid is one of the most important substances in organisms, and its dynamic changes are closely related to physiological processes. Nucleic acid labeling is conducive to providing important information for the early diagnosis and treatment of pathophysiological processes. Here, we utilized the transfer mechanism between carbon sources and CDs to synthesize wavelength-adjustable N-CDs for the nucleic acid image. Along with the increased graphite nitrogen (from 10.6 to 30.1%) gradually by the precise design of the nitrogen structure in carbon sources (e.g., primary amines, secondary amines, tertiary amines, and liking graphite-nitrogen), the energy gap of CDs reduced, resulting in adjustable wavelength from visible to near-infrared range (from 461 nm/527 nm to 650 nm/676 nm). Furthermore, N-CDs exhibited a selective affinity for nucleic acids, especially RNA. Therefore, N-CDs support an efficient platform for real-time tracking of RNA dynamic changes in cells.

Biocidal polymer derived near white light-emitting polymeric carbon particles for antibacterial and bioimaging applications

A growing antimicrobial crisis has increased demand for antimicrobial materials. It has become increasingly popular to convert polymeric macromolecules into polymeric carbon particles (PCP) in order to achieve highly biocompatible materials with unique properties as a result of the ability to synthesize nanomaterials of the right size and add value to existing stable polymers. This work presents the tuning of PCP for antibacterial application by combining a biocidal polymer with one-pot solvothermal synthesis. PCP displayed broad-spectrum antibacterial activity via various mechanisms, including inhibition of bacterial cell walls, ROS generation, and antibiotic resistance. Furthermore, these biocidal PCP were observed to show excitation-independent near-white light emission which on the other hand is generally possible due to mixed sizes, doping, and surface effects. As opposed to the parent biocidal polymer, PCP added ROS-mediated bactericidal activity, increased cytocompatibility, and nanofibers with anti-adhesive effects and potential of imaging bacterial cells.

Caffeic acid-grafted chitosan/sodium alginate/nanoclay-based multifunctional 3D-printed hybrid scaffolds for local drug release therapy after breast cancer surgery

Breast cancer is one of the most common malignant tumors in women all over the world. Mastectomy is the most effective treatment, but there are serious problems such as high tumor recurrence rate and side effects of chemotherapy. Therefore, there is an urgent need for a therapeutic strategy that can effectively promote postoperative wound healing and inhibit local tumor recurrence. In this study, a 3D printing scaffold based on carbon dots-curcumin nano-drug release (CCNPs) was developed as a local drug delivery platform (named CCNACA using CCNPs, Sodium alginate, Nanoclay and Caffeic Acid grafted Chitosan as raw materials), which has the ability to visualize drug release. The 14-day drug release test in vitro showed that the tumor inhibition rate of CCNACA scaffolds on breast cancer cells (MCF-7) was 73.77 ± 1.68 %. And the CCNACA scaffolds had good long-term antibacterial (Escherichia coli and Staphylococcus aureus) activity. Animal experiments have shown that implanting CCNACA scaffolds into surgical defects can inhibit postoperative residual cancer cells, reduce inflammation, promote angiogenesis, and repair tissue defects caused by surgery. In summary, the local drug delivery system of this manuscript has great potential in wound healing and prevention of tumor recurrence after breast cancer surgery.

Roadmap on multifunctional materials for drug delivery

This Roadmap on drug delivery aims to cover some of the most recent advances in the field of materials for drug delivery systems (DDSs) and emphasizes the role that multifunctional materials play in advancing the performance of modern DDSs in the context of the most current challenges presented. The Roadmap is comprised of multiple sections, each of which introduces the status of the field, the current and future challenges faced, and a perspective of the required advances necessary for biomaterial science to tackle these challenges. It is our hope that this collective vision will contribute to the initiation of conversation and collaboration across all areas of multifunctional materials for DDSs. We stress that this article is not meant to be a fully comprehensive review but rather an up-to-date snapshot of different areas of research, with a minimal number of references that focus upon the very latest research developments.

Multifunctional Carbon Dots for Biomedical Applications: Diagnosis, Therapy, and Theranostic

Designing suitable nanomaterials is an ideal strategy to enable early diagnosis and effective treatment of diseases. Carbon dots (CDs) are luminescent carbonaceous nanoparticles that have attracted considerable attention. Through facile synthesis, they process properties including tunable light emission, low toxicity, and light energy transformation, leading to diverse applications as optically functional materials in biomedical fields. Recently, their potentials have been further explored, such as enzyme-like activity and ability to promote osteogenic differentiation. Through refined synthesizing strategies carbon dots, a rich treasure trove for new discoveries, stand a chance to guide significant development in biomedical applications. In this review, the authors start with a brief introduction to CDs. By presenting mechanisms and examples, the authors focus on how they can be used in diagnosing and treating diseases, including bioimaging failure of tissues and cells, biosensing various pathogenic factors and biomarkers, tissue defect repair, anti-inflammation, antibacterial and antiviral, and novel oncology treatment. The introduction of the application of integrated diagnosis and treatment follows closely behind. Furthermore, the challenges and future directions of CDs are discussed. The authors hope this review will provide critical perspectives to inspire new discoveries on CDs and prompt their advances in biomedical applications.

Nitrogen-doped Carbon Dots as Efficient Photocatalysts for High Selectivity of Dehalogenative Oxyalkylation of Styrene

Carbon dots (CDs) are a type of carbon-based luminescent material with a zero-dimensional structure and a size of less than 10 nm, which are composed of sp2 /sp3 hybrid carbon nuclei and surface functional groups. Because CDs has strong photoluminescence and good light absorption in the ultraviolet and near visible regions, it is an excellent candidate for photocatalytic applications. However, the use of nonmetallic doped CDs as photosensitizers for direct photocatalytic organic reactions has been limited to several scattered reports. Herein, we present nitrogen-doped carbon dots (N-CDs) that has a capability for not only produce reactive oxygen species (ROS), including superoxide anion radical (O2 ⋅- ) and singlet oxygen (1 O2 ), but also provide an unprecedented high activity of dehalogenative oxyalkylation of styrene with a yield of 93 %. This work develops a novel opportunity to utilize cost-effective and easily accessible CDs for the advancement of photocatalysis.

Carbon dots and composite materials with excellent performances in cancer-targeted bioimaging and killing: a review

Carbon dots (CDs) are nanomaterials with excellent properties, including good biocompatibility, small size, ideal photoluminescence and surface modification, and are becoming one of the most attractive nanomaterials for the imaging, detection and treatment of tumors. Based on these advantages, CDs can be combined other materials to obtain composite particles with improved, even new, performance, mainly in photothermal and photodynamic therapies. This paper reviews the research progress of CDs and their composites in targeted tumor imaging, detection, diagnosis, drug delivery and tumor killing. It also discusses and proposes the challenges and perspectives of their future applications in these fields. This review provides ideas for future applications of novel CD-based materials in the diagnosis and treatment of cancer.

The interplay between lysosome, protein corona and biological effects of cationic carbon dots: Role of surface charge titratability

Carbon dots (CDs) are nanoparticles (NPs) with potential applications in the biomedical field. When in contact with biological fluids, most NPs are covered by a protein corona. As well, upon cell entry, most NP are sequestered in the lysosome. However, the interplay between the lysosome, the protein corona and the biological effects of NPs is still poorly understood. In this context, we investigated the role of the lysosome in the toxicological responses evoked by four cationic CDs exhibiting protonatable or non-protonatable amine groups at their surface, and the associated changes in the CD protein corona. The four CDs accumulated in the lysosome and led to lysosomal swelling, loss lysosome integrity, cathepsin B activation, NLRP3 inflammasome activation, and cell death by pyroptosis in a human macrophage model, but with a stronger effect for CDs with titratable amino groups. The protein corona formed around CDs in contact with serum partially dissociated under lysosomal conditions with subsequent protein rearrangement, as assessed by quantitative proteomic analysis. The residual protein corona still contained binding proteins, catalytic proteins, and proteins involved in the proteasome, glycolysis, or PI3k-Akt KEGG pathways, but with again a more pronounced effect for CDs with titratable amino groups. These results demonstrate an interplay between lysosome, protein corona and biological effects of cationic NPs in link with the titratability of NP surface charges.

Recent strategies of carbon dot-based nanodrugs for enhanced emerging antitumor modalities

Nanomaterial-based cancer therapy has recently emerged as a new therapeutic modality with the advantages of minimal invasiveness and negligible normal tissue toxicity over traditional cancer treatments. However, the complex microenvironment and self-protective mechanisms of tumors have suppressed the therapeutic effect of emerging antitumor modalities, which seriously hindered the transformation of these modalities to clinical settings. Due to the excellent biocompatibility, unique physicochemical properties and easy surface modification, carbon dots, as promising nanomaterials in the biomedical field, can effectively improve the therapeutic effect of emerging antitumor modalities as multifunctional nanoplatforms. In this review, the mechanism and limitations of emerging therapeutic modalities are described. Further, the recent advances related to carbon dot-based nanoplatforms in overcoming the therapeutic barriers of various emerging therapies are systematically summarized. Finally, the prospects and potential obstacles for the clinical translation of carbon dot-based nanoplatforms in tumor therapy are also discussed. This review is expected to provide a reference for nanomaterial design and its development for the efficacy enhancement of emerging therapeutic modalities.

Multifunctional polysaccharide nanoprobes for biological imaging

Imaging and tracking biological targets or processes play an important role in revealing molecular mechanisms and disease states. Bioimaging via optical, nuclear, or magnetic resonance techniques enables high resolution, high sensitivity, and high depth imaging from the whole animal down to single cells via advanced functional nanoprobes. To overcome the limitations of single-modality imaging, multimodality nanoprobes have been engineered with a variety of imaging modalities and functionalities. Polysaccharides are sugar-containing bioactive polymers with superior biocompatibility, biodegradability, and solubility. The combination of polysaccharides with single or multiple contrast agents facilitates the development of novel nanoprobes with enhanced functions for biological imaging. Nanoprobes constructed with clinically applicable polysaccharides and contrast agents hold great potential for clinical translations. This review briefly introduces the basics of different imaging modalities and polysaccharides, then summarizes the recent progress of polysaccharide-based nanoprobes for biological imaging in various diseases, emphasizing bioimaging with optical, nuclear, and magnetic resonance techniques. The current issues and future directions regarding the development and applications of polysaccharide nanoprobes are further discussed.

Zero-Dimensional Carbon Nanomaterials for Fluorescent Sensing and Imaging

Advances in nanotechnology and nanomaterials have attracted considerable interest and play key roles in scientific innovations in diverse fields. In particular, increased attention has been focused on carbon-based nanomaterials exhibiting diverse extended structures and unique properties. Among these materials, zero-dimensional structures, including fullerenes, carbon nano-onions, carbon nanodiamonds, and carbon dots, possess excellent bioaffinities and superior fluorescence properties that make these structures suitable for application to environmental and biological sensing, imaging, and therapeutics. This review provides a systematic overview of the classification and structural properties, design principles and preparation methods, and optical properties and sensing applications of zero-dimensional carbon nanomaterials. Recent interesting breakthroughs in the sensitive and selective sensing and imaging of heavy metal pollutants, hazardous substances, and bioactive molecules as well as applications in information encryption, super-resolution and photoacoustic imaging, and phototherapy and nanomedicine delivery are the main focus of this review. Finally, future challenges and prospects of these materials are highlighted and envisaged. This review presents a comprehensive basis and directions for designing, developing, and applying fascinating fluorescent sensors fabricated based on zero-dimensional carbon nanomaterials for specific requirements in numerous research fields.

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.

Effect of conjugation length on fluorescence characteristics of carbon dots

The influence of sp2- and sp3-hybridized carbon coexisting in carbon cores on fluorescence characteristics of carbon dots (CDs) was revealed by density functional theory calculations. Based on the constructed coronene-like structures, the fluorescence emission spectra, transition molecular orbital pairs and several physical quantities describing the distribution of electrons and holes were investigated. The results indicate that due to the interaction between sp2 and sp3 carbon atoms, two main factors including the hyperconjugative effect and the separation of sp2 domain by sp3 carbon atoms can regulate the fluorescence wavelength. By analyzing the transition molecular orbital pairs, it was found that the fluorescence wavelength has a close correlation with the conjugation length, suggesting that the conjugation length can predict the shift of the emission spectra of CDs. The theoretical results provide a comprehensive understanding of fluorescence mechanism and help to synthesize CDs with expected fluorescence wavelength.

Beyond traditional light: NIR-II light-activated photosensitizers for cancer therapy

With increasing demand for the accurate and safe treatment of cancer, non-invasive photodynamic therapy (PDT) has received widespread attention. However, most conventional photosensitizers are typically excited by short-wavelength visible light (400-700 nm), thus substantially hindering the penetration of light and the therapeutic effectiveness of the PDT procedure. Fortunately, near-infrared (NIR) light (>700 nm), in particular, light in the second near-infrared region (NIR-II, 1000-1700 nm) has a higher upper radiation limit, greater tissue tolerance, and deeper tissue penetration compared with traditional short-wavelength light excitation, and shows considerable potential in the clinical treatment of cancer. Therefore, it is of paramount importance and clinical value to develop photosensitizers that are excited by NIR-II light. In this review, for the first time we focus completely on recent progress made with various NIR-II photosensitizers for cancer treatment via PDT, and we briefly present the ongoing challenges and prospects of currently developed NIR-II photosensitizers for clinical practice in the near future. We believe that the above topics will inspire broad interest in researchers from interdisciplinary fields that include chemistry, materials science, pharmaceuticals, and clinical medicine, and provide insightful perspectives for exploiting new NIR-II photosensitizers for biomedical applications.

In vitro and in vivo toxicity of carbon dots with different chemical compositions

Carbon dots (CDs) are easy-obtained nanoparticles with wide range of biological activity; however, their toxicity after prolonged exposure is poorly investigated. So, in vitro and in vivo toxicity of CDs with the surfaces enriched with hydroxylated hydrocarbon chains and methylene groups (CD_GE), carboxyl and phenol groups accompanied with nitrogen (CD_3011), trifluoromethyl (CDF19) or toluidine and aniline groups (CDN19) were aimed to be discovered. CDs' in vitro toxicity was assessed on A549 cells (real-time cell analysis of impedance, fluorescence microscopy) after 24 h of incubation, and we observed no changes in cell viability and morphology. CDs' in vivo toxicity was assessed on C57Bl6 mice after multiple dosages (5 mg/kg subcutaneously) for 14 days. Lethality (up to 50%) was observed in CDN19 and CD_3011 groups on different days of dosing, accompanied by toxicity signs in case of CD_3011. There were no changes in serum biochemical parameters except Urea (increased in CDF19 and CD_3011 groups), nor substantial kidney, liver, and spleen injuries. The most impactful for all organs were also CD_3011 and CDF19, causing renal tubule injury and liver blood supply violation. Thus, CDs with a surface enriched with oxygen- and nitrogen-containing functional groups might be toxic after multiple everyday dosing, without, however, significant damages of internal organs in survived animals.

In Situ Radical Reaction-Modified Carbon Dot Nanocapsules with Macrophage Escape and Prolonged Imaging

Carbon dots (CDs) have emerged as an extremely promising platform for biological imaging, owing to their optical properties and low toxicity. However, one of the major challenges in utilizing CDs for in vivo imaging is their high immunogenicity and rapid clearance, which limits their potential. Herein, a novel approach for mitigating these issues is presented through the development of carbon dot nanocapsules (nCDs). Specifically, CDs are encapsulated within a zwitterionic polymer shell composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) to create nCDs with a size of ≈40 nm. Notably, the nCDs exhibit excitation-dependent photoluminescence behavior in the range of 550-600 nm, with tunability based on the excitation wavelength. In confocal imaging, CDs display a strong fluorescence signal after 8 h of incubation with phagocytes, while nCDs show minimal signal, suggesting that nCDs may be capable of evading phagocyte uptake. Furthermore, imaging studies in zebrafish demonstrate that nCDs exhibit a retention time >10 times longer than that of CDs, with fluorescence intensity remaining at 81% after 10 h compared to only 8% for CDs. Taken together, the study presents a novel approach for enhancing the performance of CDs in in vivo imaging applications, offering significant potential for clinical translation.

Recent advances on hyperthermia therapy applications of carbon-based nanocomposites

Generally, hyperthermia is referred to the composites capability to increase local temperature in such a way that the generated heat would lead to cancerous or bacteria cells destruction, with minimum damage to normal tissue cells. Many different materials have been utilized for hyperthermia application via different heat generating methods. Carbon-based nanomaterials consisting of graphene oxide (GO), carbon nanotube (CNT), carbon dot (CD) and carbon quantum dot (CQD), nanodiamond (ND), fullerene and carbon fiber (CF), have been studied significantly for different applications including hyperthermia due to their biocompatibility, biodegradability, chemical and physical stability, thermal and electrical conductivity and in some cases photothermal conversion. Therefore, in this comprehensive review, a structure-based view on carbon nanomaterials application in hyperthermia therapy of cancer and bacteria via various methods such as optical, magnetic, ultrasonic and radiofrequency-induced hyperthermia is presented.

Design of carbon dots for bioimaging and behavior regulation of stem cells

Carbon dots (CDs) have been widely used in bioimaging, biosensing and biotherapy because of their good biocompatibility, optical properties and stability. In this review, we comprehensively summarize the research on CDs in terms of synthesis methods, optical properties and biotoxicity. We describe and envisage the directions for CDs application in stem cell imaging and differentiation, with the aim of stimulating the design of future related CDs. We used 'carbon dots', 'stem cells', 'cell imaging', 'cell differentiation' and 'fate control' as keywords to search for important articles. The Web of Science database was used to extract vital information from a total of 357 papers, 126 review articles and 231 article proceedings within 12 years (2011-2022).

Multifaceted Carbon Dots: toward pH-Responsive Delivery of 5-Fluorouracil for In Vitro Antiproliferative Activity

The synthesis of smart hybrid material to assimilate diagnosis and treatment is crucial in nanomedicine. Herein, we present a simple and facile method to synthesize multitalented blue-emissive nitrogen-doped carbon dots N@PEGCDs. The as-prepared carbon dots N@PEGCDs show enhanced biocompatibility, small size, high fluorescence, and high quantum yield. The N@PEGCDs are used as a drug carrier for 5-fluorouracil (5-FU) with more release at acidic pH. Furthermore, the mode of action of drug-loaded CD (5FU-N@PEGCDs) has also been explored by performing wound healing assay, DCFDA assay for ROS generation, and Hoechst staining. The drug loaded with carbon dots showed less toxicity to normal cells compared to cancer cells, making it a perfect candidate to be studied for designing next-generation drug delivery systems.

Carbon Quantum Dots from Roasted Coffee Beans: Their Degree and Mechanism of Cytotoxicity and Their Rapid Removal Using a Pulsed Electric Field

Carbon quantum dots (CQDs) from heat-treated foods show toxicity, but the mechanisms of toxicity and removal of CQDs have not been elucidated. In this study, CQDs were purified from roasted coffee beans through a process of concentration, dialysis and lyophilization. The physical properties of CQDs, the degree and mechanism of toxicity and the removal method were studied. Our results showed that the size of CQDs roasted for 5 min, 10 min and 20 min were about 5.69 ± 1.10 nm, 2.44 ± 1.08 nm and 1.58 ± 0.48 nm, respectively. The rate of apoptosis increased with increasing roasting time and concentration of CQDs. The longer the roasting time of coffee beans, the greater the toxicity of CQDs. However, the caspase inhibitor Z-VAD-FMK was not able to inhibit CQDs-induced apoptosis. Moreover, CQDs affected the pH value of lysosomes, causing the accumulation of RIPK1 and RIPK3 in lysosomes. Treatment of coffee beans with a pulsed electric field (PEF) significantly reduced the yield of CQDs. This indicates that CQDs induced lysosomal-dependent cell death and increased the rate of cell death through necroptosis. PEF is an effective way to remove CQDs from roasted coffee beans.

Carbon Dots-Biomembrane Interactions and Their Implications for Cellular Drug Delivery

The effect of carbon dots (CDs) on a model blayer membrane was studied as a means of comprehending their ability to affect cell membranes. Initially, the interaction of N-doped carbon dots with a biophysical liposomal cell membrane model was investigated by dynamic light scattering, z-potential, temperature-modulated differential scanning calorimetry, and membrane permeability. CDs with a slightly positive charge interacted with the surface of the negative-charged liposomes and evidence indicated that the association of CDs with the membrane affects the structural and thermodynamic properties of the bilayer; most importantly, it enhances the bilayer's permeability against doxorubicin, a well-known anticancer drug. The results, like those of similar studies that surveyed the interaction of proteins with lipid membranes, suggest that carbon dots are partially embedded in the bilayer. In vitro experiments employing breast cancer cell lines and human healthy dermal cells corroborated the findings, as it was shown that the presence of CDs in the culture medium selectively enhanced cell internalization of doxorubicin and, subsequently, increased its cytotoxicity, acting as a drug sensitizer.

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.

The blood-brain barrier: structure, regulation, and drug delivery

Blood-brain barrier (BBB) is a natural protective membrane that prevents central nervous system (CNS) from toxins and pathogens in blood. However, the presence of BBB complicates the pharmacotherapy for CNS disorders as the most chemical drugs and biopharmaceuticals have been impeded to enter the brain. Insufficient drug delivery into the brain leads to low therapeutic efficacy as well as aggravated side effects due to the accumulation in other organs and tissues. Recent breakthrough in materials science and nanotechnology provides a library of advanced materials with customized structure and property serving as a powerful toolkit for targeted drug delivery. In-depth research in the field of anatomical and pathological study on brain and BBB further facilitates the development of brain-targeted strategies for enhanced BBB crossing. In this review, the physiological structure and different cells contributing to this barrier are summarized. Various emerging strategies for permeability regulation and BBB crossing including passive transcytosis, intranasal administration, ligands conjugation, membrane coating, stimuli-triggered BBB disruption, and other strategies to overcome BBB obstacle are highlighted. Versatile drug delivery systems ranging from organic, inorganic, and biologics-derived materials with their synthesis procedures and unique physio-chemical properties are summarized and analyzed. This review aims to provide an up-to-date and comprehensive guideline for researchers in diverse fields, offering perspectives on further development of brain-targeted drug delivery system.

Carbon Dots from Lycium barbarum Attenuate Radiation-Induced Bone Injury by Inhibiting Senescence via METTL3/Clip3 in an m6A-Dependent Manner

Radiation-induced bone injury management remains a challenge in clinical practice, and there is no effective medicine. Recently, biomass-derived carbon dots (CDs) have attracted attention in biomedical engineering due to the advantages of abundant heteroatoms, low toxicity, and no need to drug loading. Here, we report that CDs, synthesized from Lycium barbarum via hydrothermal strategy, can effectively alleviate radiation-induced bone injury. CCK-8, apoptosis analysis, β-galactosidase staining, quantitative polymerase chain reaction, and western blots demonstrate that CDs can mediate radiation-induced damage and senescence of bone marrow mesenchymal stem cells (BMSCs). CDs regulate osteogenic- and adipogenic-balance after irradiation, shown by alizarin red and oil red O staining. In vivo experiments reveal that CDs prevent the occurrence of osteoradionecrosis in rats, demonstrated by micro-CT and histology examination. The osseointegration of titanium implants installed in irradiated bone is promoted by CDs. Mechanistically, CDs increase the N6-methyladenosine (m6A) level of irradiated BMSCs via the increased methyltransferase-like 3 (METTL3). High-throughput sequencing facilitates detection of increased m6A levels located in the 3'-untranslated regions (UTR) of the CAP-Gly domain containing linker protein 3 (Clip3) mRNA. The dual-luciferase reporter assay shows that 3'UTR is the direct target of METTL3. Subsequently, the increased m6A modification led to enhanced degradation of mRNA and downregulated CLIP3 expression, eventually resulting in the alleviation of radiation-induced bone injury. Interfering with the METTL3/Clip3 axis can antagonize the effect of CDs, indicating that CDs mediate radiation-induced bone injury via the METTL3/Clip3 axis. Taken together, CDs from L. barbarum alleviate radiation-induced bone injury by inhibiting senescence via regulation of m6A modification of Clip3. The present study paves a new pathway for the management of radiation-induced bone injury.

Photothermal Nanomaterials: A Powerful Light-to-Heat Converter

All forms of energy follow the law of conservation of energy, by which they can be neither created nor destroyed. Light-to-heat conversion as a traditional yet constantly evolving means of converting light into thermal energy has been of enduring appeal to researchers and the public. With the continuous development of advanced nanotechnologies, a variety of photothermal nanomaterials have been endowed with excellent light harvesting and photothermal conversion capabilities for exploring fascinating and prospective applications. Herein we review the latest progresses on photothermal nanomaterials, with a focus on their underlying mechanisms as powerful light-to-heat converters. We present an extensive catalogue of nanostructured photothermal materials, including metallic/semiconductor structures, carbon materials, organic polymers, and two-dimensional materials. The proper material selection and rational structural design for improving the photothermal performance are then discussed. We also provide a representative overview of the latest techniques for probing photothermally generated heat at the nanoscale. We finally review the recent significant developments of photothermal applications and give a brief outlook on the current challenges and future directions of photothermal nanomaterials.

RNA-Targeting Carbon Dots for Live-Cell Imaging of Granule Dynamics

It is significant to monitor the different RNA granules dynamics and phase separation process inside cells under various stresses, for example, oxidative stress. The current small-molecule RNA probes work well only in fixed cells and usually encounter problems such as insufficient stability and biocompatibility, and thus a specific RNA-targeting fluorescent nanoprobe that can be used in the living cells is urgently desired. Here, the de novo design and microwave-assisted synthesis of a novel RNA-targeting, red-emissive carbon dots (named as M-CDs) are reported by choosing neutral red and levofloxacin as precursors. The as-synthesized M-CDs is water-soluble with a high fluorescence quantum yield of 22.83% and can selectively bind to RNA resulting in an enhanced red fluorescence. More interestingly, such an RNA-targeting, red-emissive M-CDs can be fast internalized into cells within 5 s and thus used for real-time imaging the dynamic process of intracellular stress granules under oxidative stress, revealing some characteristics of granules that have not been identified by previously reported RNA and protein biomarkers. This research paves a new pathway for visualizing bulk RNA dynamics and studying phase-separation behaviors in living cells by rational design of the fluorescent carbon dots in terms of structure and functionality.

Hydrophobic Carbon Dots Derived from Organic Pollutants and Applications in NIR Anticounterfeiting and Bioimaging

In an effort to fulfill the strategy of sustainable development, Rhodamine B, a common and toxic organic pollutant in the textile industry, was reported for the first time as a single precursor to develop a kind of novel hydrophobic nitrogen-doped carbon dot (HNCD) through a green and facile one-pot solvothermal method. The HNCDs with an average size of 3.6 nm possess left and right water contact angles of 109.56° and 110.34°, respectively. The HNCDs manifest excitation wavelength-tunable and upconverted fluorescence from the ultraviolet (UV) to the near-infrared (NIR) range. Furthermore, the PEGylation of HNCDs enables them to be used as an optical marker for cell and in vivo imaging. Notably, the HNCDs with solvent-dependent fluorescence can be used for invisible inks with a wide range of light responses from UV-vis-NIR spectra. This work not only provides an innovative way to recycle chemical waste but also expands the potential application of HNCDs in NIR security printing and bioimaging.

Boron Dopants in Red-Emitting B and N Co-Doped Carbon Quantum Dots Enable Targeted Imaging of Lysosomes

Lysosomes are of great significance to cell growth, metabolism, and survival, as they independently maintain acidity and regulate various balances in cells. Therefore, it is essential to develop advanced probes for lysosome visualization and live tracking. Herein, a type of lysosome-targeting probe based on boron (B) and nitrogen (N) co-doped carbon quantum dots (B/N-CQDs) is presented, which exhibits red emission at 618 nm, high quantum yield (28%), and excellent fluorescence stability (97% at 1 h). These B/N-CQDs are prepared by a novel and green solid-state reaction and purified using a simple extraction process without additional chemical modifications. It is found that the boron dopants in the structure play a crucial role in the resultant lysosome-specific targeting property through borate esterification between boronic acid groups in the sample and diol structures in glycoproteins. This can be applied as a powerful tool for cell apoptosis, necrosis, and endosomal escape tracking. This work not only offers a new concept for targeted subcellular probe designs via chemical doping but also demonstrates the feasibility of these tools for analyzing complex cellular physiological activities.

Activating One/Two-Photon Excited Red Fluorescence on Carbon Dots: Emerging n→π Photon Transition Induced by Amino Protonation

Due to the complicated nature of carbon dots (CDs), fluorescence mechanism of red fluorescent CDs is still unrevealed and features highly controversial. Reliable and effective strategies for manipulating the red fluorescence of CDs are urgently needed. Herein, CDs with one-photon excited (622 nm, QYs ≈ 17%) and two-photon (629 nm) excited red fluorescence are prepared by acidifying o-phenylenediamine-based reaction sediments. Systematic analysis reveals that the protonation of amino groups increases the particle surface potential, disperse the bulk sediments into nano-scale CDs. In the meanwhile, amino protonation of pyridinic nitrogen (-N=) structure inserts numerous n orbital energy levels between the π → π* transition, narrows the gap distance for photon transition, and induces red fluorescence emission on CDs. Present research reveals an effective pathway to activate CDs reaction sediments and trigger red emission, thus may open a new avenue for developing CDs with ideal optical properties and promising application prospects.

Planted Graphene Quantum Dots for Targeted, Enhanced Tumor Imaging and Long-Term Visualization of Local Pharmacokinetics

While photoluminescent graphene quantum dots (GQDs) have long been considered very suitable for bioimaging owing to their protein-like size, superhigh photostability and in vivo long-term biosafety, their unique and crucial bioimaging applications in vivo remain unreachable. Herein, planted GQDs are presented as an excellent tool for in vivo fluorescent, sustainable and multimodality tumor bioimaging in various scenarios. The GQDs are in situ planted in the poly(ethylene glycol) (PEG) layer of PEGylated nanoparticles via a bottom-up molecular approach to obtain the NPs-GQDs-PEG nanocomposite. The planted GQDs show more than four times prolonged blood circulation and 7-8 times increased tumor accumulation than typical GQDs in vivo. After accessible specificity modification, the multifunctional NPs-GQDs-PEG provides targeted, multimodal molecular imaging for various tumor models in vitro or in vivo. Moreover, the highly photostable GQDs enable long-term, real-time visualization of the local pharmacokinetics of NPs in vivo. Planting GQDs in PEGylated nanomedicine offers a new strategy for broad in vivo biomedical applications of GQDs.

Bioengineered dual fluorescent carbon nano dots from Indian long pepper leaves for multifaceted environmental and health utilities

In this article, we present the synthesis of Piper longum leaves-derived ethanolic carbon dots (PLECDs) using the most simplistic environmentally friendly solvothermal carbonization method. The PLECDs fluoresced pink color with maximum emission at 670 nm at 397 nm excitation. Additionally, the dried PLECDs dissolved in water showed green fluorescence with higher emission at 452 nm at 370 nm excitation. The UV spectra showed peaks in the UV region (271.25 nm and 320.79 nm) and a noticeable tail in the visible region, signifying the efficient synthesis of nano-sized carbon particles and the Mie scattering effect. Various functional groups (-OH, -N-H, -C-H, -C = C, -C-N, and -C-O) were identified using Fourier transform infrared spectroscopy (FTIR). Its nanocrystalline property was revealed by the sharp peaks in the X-ray diffraction (XRD). High-resolution transmission electron microscopy (HRTEM) photomicrograph displayed a roughly spherical structure with a mean size of 2.835 nm. The energy dispersive X-ray (EDAX) and X-ray photoelectron spectroscopy (XPS) revealed the elemental abundance of C, O, and N. The high-performance thin-layer chromatography (HPTLC) fingerprint of PLECDs showed an altered pattern than its precursor (Piper longum leaves ethanolic extract or PLLEE). The PLECDs sensed Cu²⁺ selectively with a limit of detection (LOD) and limit of quantification (LOQ) of 0.063 μM and 0.193 μM, respectively. It showed excellent cytotoxicity toward MDA-MB-231 (human breast cancer), SiHa (human cervical carcinoma), and B16F10 (murine melanoma) cell lines with excellent in vitro bioimaging outcomes. It also has free radical scavenging activity. The PLECDs also showed outstanding bacterial biocompatibility, pH-dependent fluorescence stability, photostability, physicochemical stability, and thermal stability.

Specific Chemiluminescence Imaging and Enhanced Photodynamic Therapy of Bacterial Infections by Hemin-Modified Carbon Dots

Antibacterial photodynamic therapy (aPDT) is a promising antibiotics-alternative strategy for bacterial infectious diseases, which features broad-spectrum antibacterial activity with a low risk of inducing bacterial resistance. However, clinical applications of aPDT are still hindered by the hydrophobicity-caused inadequate photodynamic activity of conventional photosensitizers and the hypoxic microenvironment of bacterial infections. To address these problems, herein, a promising strategy is developed to achieve specific chemiluminescence (CL) imaging and enhanced PDT of bacterial infections using hemin-modified carbon dots (H-CDs). The H-CDs can be facilely prepared and exhibit favorable water solubility, augmented photodynamic activity, and unique peroxidase-mimicking capacity. Compared with the free CDs, the photodynamic efficacy of H-CDs is significantly augmented due to the increased electron-hole separation efficiency. Moreover, the peroxidase catalytic performance of H-CDs enables not only infection identification via bacterial infection microenvironment-responsive CL imaging but also oxygen self-supplied aPDT with hypoxia-relief-enhanced bacteria inactivation effects. Finally, the enhanced aPDT efficiencies of H-CDs are validated in both in vivo abscess and infected wound models. This work may provide an effective antibacterial platform for the selective imaging-guided treatment of bacterial infections.

Recent developments in carbon dots: a biomedical application perspective

Recently, newly developed carbon-based nanomaterials known as carbon dots (CDs) have generated significant interest in nanomedicine. However, current knowledge regarding CD research in the biomedical field is still lacking. An overview of the most recent development of CDs in biomedical research is given in this review article. Several crucial CD applications, such as biosensing, bioimaging, cancer therapy, and antibacterial applications, are highlighted. Finally, CD-based biomedicine's challenges and future potential are also highlighted to enrich biomedical researchers' knowledge about the potential of CDs and the need for overcoming various technical obstacles.

Bioinspired MoS2 Nanosheet-Modified Carbon Fibers for Synergetic Bacterial Elimination and Wound Disinfection

Bacterial infection is one of the most frequent wound complications and has become a major public health concern. Increasing resistance to antibiotics has been noted with these agents broadly used in wound management. It is an urgent demand to develop alternative antibacterial strategies with a reduced chance of resistance. Herein, a Nepenthes-mimicking nanosheet array of MoS₂ on carbon fibers (CF-MoS₂ ) is proposed to achieve dual bactericidal activities. First, the sharp edges of synthesized surfaces are capable of inducing physical disruption of cell membranes, demonstrating mechanical antibacterial activity like their natural counterparts. Second, in the presence of near-infrared light, bioinspired CF-MoS₂ nanosheets are able to cause the death of damaged bacteria owing to their inherent photothermal properties. Such dual-functional modes endow the surfaces with nearly 100% killing efficiency for highly concentrated Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore, their potential to be applied as wound dressings for photothermal treatment of infectious wounds is also investigated in vivo. Bioinspired CF-MoS₂ dressings show advantages of synergistic disinfection and efficient promotion of wound regeneration. It is foreseen that this high-performance and multifunctional CF-MoS₂ could afford a feasible broad-spectrum treatment for non-antibiotic disinfection.

Antibacterial Carbon Dots-Based Composites

The emergence and global spread of bacterial resistance to conventionally used antibiotics have highlighted the urgent need for new antimicrobial agents that might replace antibiotics. Currently, nanomaterials hold considerable promise as antimicrobial agents in anti-inflammatory therapy. Due to their distinctive functional physicochemical characteristics and exceptional biocompatibility, carbon dots (CDs)-based composites have attracted a lot of attention in the context of these antimicrobial nanomaterials. Here, a thorough assessment of current developments in the field of antimicrobial CDs-based composites is provided, starting with a brief explanation of the general synthesis procedures, categorization, and physicochemical characteristics of CDs-based composites. The many processes driving the antibacterial action of these composites are then thoroughly described, including physical destruction, oxidative stress, and the incorporation of antimicrobial agents. Finally, the obstacles that CDs-based composites now suffer in combating infectious diseases are outlined and investigated, along with the potential applications of antimicrobial CDs-based composites.

Microwave synthesis of blue emissive carbon dots from 5-sulpho anthranilic acid and 1,5-diphenyl carbazide for sensing of levocetirizine and niflumic acid

In this work, water soluble carbon dots (CDs) were synthesized by using 5- sulpho anthranilic acid (SAA) and 1,5-diphenylycarbazide (DPC) as precursors via microwave-assisted method and named as "SD-CDs". We studied the effect of SAA and DPC molar ratio (1:3, 2:2 and 3:1) for the preparation of blue fluorescent CDs, showing the best emission properties at molar 3:1 ratio of SAA and DPC. The as-prepared SD-CDs emit bright blue color under UV light at 365 nm, and exhibit emission peak at 392 nm when excited at 319 nm. The as-synthesized SD-CDs act as a fluorescent sensor for detection of levocetirizine and niflumic acid through the fluorescence "turn-on-off" mechanism. The developed probe exhibited good linearity in the concentrations (levocetirizine - 1.0-100 µM and niflumic acid - 0.5-100 µM) with detection limits of 3.92 nM and 0.19 µM for levocetirizine and niflumic acid, respectively. Importantly, the developed analytical method was successfully used for the detection of levocetirizine in tablets and niflumic acid in biofluids of human (serum, plasma and urine), showing good recoveries from 97 to 99 %. Thus, this SD-CDs-based fluorescence method has the potential for levocetirizine and niflumic acid assays in biological and pharmaceutical samples.

Glycyrrhizae radix et Rhizoma-Derived Carbon Dots and Their Effect on Menopause Syndrome in Ovariectomized Mice

With the extension of the human life span and the increasing pressure of women's work and life, menopause syndrome (MPS) refers to a problem that puzzles almost all women worldwide. Hormone replacement treatment (HRT) can effectively mitigate the symptoms but can also exert adverse effects to a certain extent. Glycyrrhizae radix et rhizome (GRR) is commonly made into a charcoal processed product, termed GRR Carbonisatas (GRRC), for use in traditional Chinese medicine (TCM). GRRC is widely used to treat MPS and other gynecological diseases. In this study, GRRC was prepared through pyrolysis. Subsequently, GRR-derived carbon dots (GRR-CDs) were purified through dialysis and characterized using transmission electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared, ultraviolet, fluorescence, X-ray photoelectron microscopy, and high-performance liquid chromatography. The effects of GRR-CDs on MPS were examined and confirmed using ovariectomized female mice models. The GRR-CDs ranged from 1.0 to 3.0 nm in diameter and with multiple surface chemical groups, as indicated by the results. GRR-CDs can elevate the estradiol (E2) level of healthy female mice. Moreover, GRR-CDs can alleviate MPS using the typical ovariectomized mice model, as confirmed by elevating the estradiol (E2) level and reducing the degree of follicle stimulating hormone (FSH) and luteinizing hormone (LH) and raising the degree of uterine atrophy. The results of this study suggested that GRR-CDs may be a potential clinical candidate for the treatment of MPS, which also provides a possibility for nanodrugs to treat hormonal diseases.

Investigation into Red Emission and Its Applications: Solvatochromic N-Doped Red Emissive Carbon Dots with Solvent Polarity Sensing and Solid-State Fluorescent Nanocomposite Thin Films

In this work, a NIR emitting dye, p-toluenesulfonate (IR-813) was explored as a model precursor to develop red emissive carbon dots (813-CD) with solvatochromic behavior with a red-shift observed with increasing solvent polarity. The 813-CDs produced had emission peaks at 610 and 698 nm, respectively, in water with blue shifts of emission as solvent polarity decreased. Subsequently, 813-CD was synthesized with increasing nitrogen content with polyethyleneimine (PEI) to elucidate the change in band gap energy. With increased nitrogen content, the CDs produced emissions as far as 776 nm. Additionally, a CD nanocomposite polyvinylpyrrolidone (PVP) film was synthesized to assess the phenomenon of solid-state fluorescence. Furthermore, the CDs were found to have electrochemical properties to be used as an additive doping agent for PVP film coatings.