Carbon dots: The next generation platform for biomedical applications

Aggregation induced emission "Turn on" ultra-low detection of anti-inflammatory drug flufenamic acid in human urine samples by carbon dots derived from bamboo stem waste

Carbon dot-based fluorescence sensors have attracted research interest for the selective determination of anti-inflammatory drugs in biological fluids and environments. The overdose and accumulation of anti-inflammatory drugs in tissues can cause chronic side effects including abdominal pain, and renal damage. Herein, we report a new fluorescent probe, bamboo stem waste-derived carbon dots (BS-CDs) for highly sensitive detection of Flufenamic acid (FA), a hazardous anti-inflammatory drug. The UV-vis absorption spectra of BS-CDs show a redshifted absorption peak at 283 nm upon the addition of FA suggesting strong binding interaction between BS-CDs and FA molecule. The BS-CDs showed a fluorescence enhancement (∼2-fold) detection for FA (400 μM) in the linear concentration range (0.40 → 0.65 μM) with a limit of detection (LoD; 17 nM) and binding constant (Ka = 1.33 × 10-3 M-1). The time-resolved fluorescence decay analysis showed that the average lifetime of BS-CDs has slightly changed (4.42 → 4.67 ns) by the interaction with FA through the aggregation-induced emission (AIE) process. The interference, pH, and effect of time results suggest that BS-CDs are highly selective probes for FA detection and do not show any interference involvement during FA detection. The confirmation of the structure and morphology changes of BS-CDs after interaction with FA was carried out by XRD, FESEM, HRTEM, FTIR, and Raman spectroscopy. The practicability of the BS-CDs probe was proved by the detection of FA in human urine samples with recovery of 103-109 %. This suggests that the proposed BS-CDs-based 'turn-on' sensor could be used to determine the FA in biological fluids.

Carbon dots: synthesis, sensing mechanisms, and potential applications as promising materials for glucose sensors

The disruption of glucose (Glu) metabolism in the human body can lead to conditions such as diabetes and hyperglycemia. Therefore, accurately determining Glu levels is crucial for clinical diagnosis and other applications. Carbon dots (CDs) are a novel category of carbon nanomaterials that exhibit outstanding optical properties, excellent biocompatibility, high water solubility, low production costs, and straightforward synthesis. Recently, researchers have developed various carbon dot sensors for fast and real-time Glu monitoring. In this context, we provide a comprehensive introduction to Glu and CDs for the first time. We categorize the synthetic methods for CDs and the sensing mechanisms, further classifying the applications of carbon dot probes into single-probe sensing, ratiometric sensing, and visual detection. Finally, we discuss the future development needs for CD-based Glu sensors. This review aims to offer insights into advancing Glu sensors and modern medical treatments.

Engineering carbon-based nanomaterials for the delivery of platinum compounds: An innovative cancer disarming frontier

Carbon-based nanomaterials have been frequently used as one of the most advanced and fascinating nanocarriers for drug delivery applications due to their unique physicochemical properties. Varying types of carbon nanomaterials (CNMs) including carbon nanotubes, graphene, graphene oxides, carbon nanohorns, fullerenes, carbon nanodots, and carbon nanodiamonds are promising candidates for designing novel systems to deliver platinum compounds. CNMs modification with various moieties renders vast bio-applications in the area of targeted and organelle-specific cancer therapy. This review featured an updated and concise summarizations of various types of CNMs, their synthesis, advantages and disadvantages including potential bio-toxicity for biomedical applications. The therapeutic utility of CNMs and their efficacy have been noticed and for the first time, this review addressed CNMs-focused applications on the delivery of platinum-derivatives to the cancer site. Collectively, the contents of this review will assist researchers to focus on the possible fabrication, bio-functionalization and designing methods of CNMs to the further development of their future biomedical implementations.

Improving the mechanical property of silk by feeding silkworm with chiral carbon dots

The influence of chiral materials on organisms is crucial. However, there is little research on the impact of chiral carbon dots (CDs), a kind of typical chiral materials, on biology. Herein, chiral CDs (L-/D-CDs) were synthesized using the thermal polymerization method from citric acid and chiral cysteine. The effect of chiral CDs on silkworms was explored through feeding silkworms with chiral CDs. The breaking strength of silk fibers (667.9 MPa) in D-CDs group exhibit a 71.4 % increase compared with control-silk (389.5 MPa), while the breaking strength of silk fibers in L-CDs group increases by 51.6 %. In addition, Fourier transform infrared spectra display CDs can prevent the transformation from random coil/α-helix structures to β-sheet structures. Furthermore, D-CDs group exhibit the highest percentage of four primary amino acids (glycine, alanine, serine, and tyrosine) relative to the total amino acids in silkworm hemolymph. This percentage is elevated by 70.5 % compared to the control group, thereby furnishing an ample supply of raw materials for the synthesis of silk proteins. In contrast, L-CDs group exhibit increase by 39.3 %. Our work provides new ideas and approaches for studying the effects of chiral materials on living organisms.

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

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

Synergistic Anticancer Effects by Enhancing the G-Quadruplex Binding of Nickel(II) Salphen Complexes through Coupling with S-Doped Carbon Nanodots

In recent decades, researchers have focused on developing less toxic and more precise cancer therapies. Carbon nanodots (CDs) are among the most promising technologies due to their high biocompatibility, tunable fluorescence, and ability to facilitate photothermal and photodynamic therapy. This study explores the synthesis and characterization of two CDs conjugated with Salphen metal complexes, namely, CDs-PEG-M1 and CDs-PEG-M2, through Sonogashira coupling. Their interaction with G-quadruplex DNA structures (G4s), motifs largely involved in cancer development, was evaluated using various spectroscopic techniques. The results indicate that CDs-PEG-M1 exhibits greater effectiveness in stabilizing G4 structures compared to the metal complex alone or nonfunctionalized CDs. This enhanced stabilization suggests that CDs-PEG-M1 could reduce the concentration of the metal complex needed for potential antitumor applications, thereby minimizing side effects on nontarget tissues. When tested on breast cancer models (MDA-MB-231 as a triple-negative model and MCF-7 as a HER-2 positive model) and on a healthy cell line (HDFa), the CDs-PEG-M1 conjugate reduced cell viability in a concentration- and time-dependent manner, showing greater potency and selectivity against cancer cells compared to virgin CDs and the free M1 complex. This synergistic anticancer effect, driven by the interaction with G4 structures and reactive oxygen species production, underscores the potential of CDs-PEG-M1 as a targeted nanotheranostic tool.

Aptamer-functionalized Fe3O4/MWCNTs@Mo-CDs nanozyme for rapid colorimetric detection toward Escherichia coli

The pathogenic bacteria induced foodborne disease has been detrimental to public health worldwide. Herein, the peroxidase (POD)-like Fe3O4/MWCNTs@Mo-CDs (FMMC) nanozyme was applied for the detection of Escherichia coli (E. coli). The E. coli aptamer was conjugated with the surface of the FMMC, which effectively enhanced the POD-like activity attributing to the higher affinity to the substrate, and then specific capture of E. coli in food matrices, leading to the reduction of POD-like activity. Therefore, a robust and facile colorimetric aptasensor was developed for detecting E. coli with a wide linear range of 101-106 CFU/mL, low LOQ of 101 CFU/mL and LOD of 0.978 CFU/mL. The aptasensor demonstrated the satisfied selectivity for E. coli compared to the other strains. This method possessed the potential application for fast in situ screening of foodborne pathogens in food products.

Surface modification of carbon dots with cyclodextrins as potential biocompatible photoluminescent delivery/bioimaging nanoplatform

BACKGROUND

Cyclodextrins are a well-established system which form inclusion complexes with many guest molecules. This property can be easily exploited to develop drug delivery systems. Additionally, carbon dots (CD) are a low-toxic photoluminescent product which have been used as luminescent tags. The combination of cyclodextrins and carbon dots allows obtaining a new nanoplatform, a biocompatible material, with both capabilities, increasing as well the internalization by the cells of the CD, induced by the cyclodextrins.

RESULTS

In the present work, we have modified the surface of carbon dots obtained from citric acid and glutathione with β and γ cyclodextrins. After a morphological and spectroscopic characterization, we concluded that the luminescence quantum yield and absorption molar coefficient of the derivatized and unmodified carbon dots was the same. These findings, together with the spectroscopic detection of active cyclodextrins, those bond to the CD able to interact with a guest molecule, allowed determination of the ratios: cyclodextrins/CD, active cyclodextrins/CD and an estimation of the CD molecular mass. Furthermore, the biocompatibility of the new materials was evaluated through cytotoxicity and cell-penetrance assays revealing that the materials were non cytotoxic up to 0.1 mg/mL. Moreover, the biocompatible developed nanoplatform penetrates in the cells maintaining the material's intrinsic fluorescence, thus constituting an adequate photoluminescent-tag with high-contrast for in vitro cell imaging.

SIGNIFICANCE

This work provides a new and easy method to combine cyclodextrins and carbon dots into a biocompatible material which can be used as nanoplatform both as drug delivery system and as photoluminescent tag in cell imaging. Likewise, this paper shows how to characterize the number of cyclodextrins and active cyclodextrins per CD, having an average stoichiometric relation of 1:1 for guest molecule - CD. Additionally, the minimum molecular mass of the unmodified CD was indirectly obtained, yielding about 1.6-1.9 kDa.

Interface properties of nanostructured carbon-coated biological implants: an overview

The interfaces between medical implants and living tissues are of great complexity because of the simultaneous occurrence of a wide variety of phenomena. The engineering of implant surfaces represents a crucial challenge in material science, but the further improvement of implant properties remains a critical task. It can be achieved through several processes. Among them, the production of specialized coatings based on carbon-based materials stands very promising. The use of carbon coatings allows one to simultaneously fine-tune tribological, mechanical, and chemical properties. Here, we review applications of nanostructured carbon coatings (nanodiamonds, carbon nanotubes, and graphene-related materials) for the improvement of the overall properties of medical implants. We are focusing on biological interactions, improved corrosion resistance, and overall mechanical properties, trying to provide a complete overview within the field.

Metal-doped carbon dots for biomedical applications: From design to implementation

Carbon dots (CDs), as a new kind of fluorescent nanomaterials, show great potential for application in several fields due to their unique nano-size effect, easy surface functionalization, controllable photoluminescence, and excellent biocompatibility. Conventional preparation methods for CDs typically involve top-down and bottom-up approaches. Doping is a major step forward in CDs design methodology. Chemical doping includes both non-metal and metal doping, in which non-metal doping is an effective strategy for modulating the fluorescence properties of CDs and improving photocatalytic performance in several areas. In recent years, Metal-doped CDs have aroused the interest of academics as a promising nano-doping technique. This approach has led to improvements in the physicochemical and optical properties of CDs by altering their electron density distribution and bandgap capacity. Additionally, the issues of metal toxicity and utilization have been addressed to a large extent. In this review, we categorize metals into two major groups: transition group metals and rare-earth group metals, and an overview of recent advances in biomedical applications of these two categories, respectively. Meanwhile, the prospects and the challenges of metal-doped CDs for biomedical applications are reviewed and concluded. The aim of this paper is to break through the existing deficiencies of metal-doped CDs and fully exploit their potential. I believe that this review will broaden the insight into the synthesis and biomedical applications of metal-doped CDs.

Recent advances in waste-derived carbon dots and their nanocomposites for environmental remediation and biological applications

The surging demand for eco-friendly nanomaterial synthesis has spurred the emergence of green approaches for synthesizing carbon dots (CDs). These methods utilized natural carbon sources, such as different kind of waste for CDs synthesis, underscoring their significance in waste management and circular economy initiatives. Furthermore, the properties of CDs can be tailored by their functionalization with different materials, enabling their versatile utilization in diverse scientific domains. In this regard, the current study delves into an in-depth review of recent advances in the green/sustainable fabrication of carbon dots nanocomposites (CDNCs) with metal/metal oxides and polymers within the timeframe of 2019-2023. It begins by categorizing different types of CDs, analyzing their associated nanocomposites with mechanistic insights. The primary focus is on green synthesis methods, particularly those that employ waste materials. Furthermore, we also discussed the applications of these CDs in both environmental and biological fields by covering areas such as catalysis, photocatalysis, heavy metal ion sensing, antimicrobial, and bioimaging with in-depth underlying mechanisms. At last, the review highlights the significant challenges with future directions. These include the pursuit of cost-effective green precursors, the advancement of streamlined one-step synthesis techniques, and their efficient utilization for diverse applications. Therefore, this review provides valuable insights for researchers seeking to enhance the functionality and sustainability of CDNCs by highlighting their potential to address environmental and biological challenges.

A carbon dots-MnO2 nanosheet-based turn-on pseudochemodosimeter as low-cost probe for selective detection of hazardous mercury ion contaminations in water

Mercury is a highly hazardous element due to its profound toxicity and wide abundance in the environment. Despite the availability of various fluorimetric detection tools for Hg2+, including organic fluorophores and aptasensors, they often suffer from shortcomings like the utilization of expensive chemicals and toxic organic solvents, multi-step synthesis, sometimes with poor selectivity and low sensitivity. Whereas, biomass-derived fluorophores, such as carbon dots (CDs), present themselves as cost-effective and environmentally benign alternatives that exhibit comparable efficacy. Herein, we report a reaction-driven sensing assembly based on CDs, MnO2 nanosheets, and hydroquinone monothiocarbonate (HQTC) for the detection of Hg2+ ions, which relies on the formation of a CDs-MnO2 FRET-conjugate, resulting in the quenching of the intrinsic fluorescence of CDs. In a pseudochemodosimetric approach, the thiophilic nature of mercury was utilized for in-situ generation of the reducing species, hydroquinone from HQTC, resulting in the reduction of MnO2 nanosheets, the release of fluorescent CDs back to the solution. The low limit of detection (LOD) was achieved as 2 ppb (0.01 μM). The probe worked efficiently in real water samples like sea, river with good recovery of spiked Hg2+ and in some Indian ayurvedic medicines as well. Furthermore, solid-phase detection with sodium alginate beads demonstrated the ability of this cost-effective sensing assembly for onsite detection of Hg2+ ions.

One-pot Synthesis of High-performance Green-emitting Carbon Dots for Cd2+ Sensing and Anti-counterfeiting Applications

This study presents a facile one-pot solvothermal synthesis of high-performance green fluorescent carbon dots (G-CDs) using o-phenylenediamine and ethylenediamine as precursors. The G-CDs show excellent optical, temporal, and chemical stability. Notably, they exhibit the highest quantum yield of 24.2% in ethanol and a strong green emission peaking at 546 nm under 440-490 nm excitation. In addition, G-CDs have outstanding salt resistance and multi-solvent compatibility. Due to its bright photoluminescence, G-CDs can be used as a secure ink for anti-counterfeiting. More remarkably, Cd2+ ions can efficiently quench the fluorescence of G-CDs with a detection limit of 0.152 µmol/L, enabling accurate quantification of Cd2+ in water systems. The simple synthesis of high-performance G-CDs expands their applicability in sensing and bioimaging.

Rapid Quantitative Detection for Nitrofurantoin Based on Nitrogen-Doped Highly Photoluminescent Carbon Dots

Nitrogen-doped carbon dots (NCD) with high fluorescence retention and good stability were successfully fabricated using citric acid and urea via a facile and eco-friendly one-step microwave method, which exhibited superior specificity for detection of nitrofurantoin (NFT). Upon the addition of NFT, the fluorescence intensity of NCD at 450 nm was significantly decreased. Besides, a satisfactory linear relationship between the fluorescence quenching efficiency and concentrations of NFT was obtained. Especially, NCD was qualitatively and quantitatively applied for detection NFT in milk and meat extract samples with a high recovery rate. Consequently, it was suggested that the detection method had potential application in the specific detection of NFT, offering a novel approach for veterinary drug residue detection.

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.

The art of simplicity: Water-soluble porphyrin-like carbon dots self-assemble into mesmerizing red glow

In this new study, we present an intriguing development in the field of theranostics: the simplistic self-assembly of red-emissive amphiphilic porphyrin-like carbon dots (P-CDs). By harnessing their exceptional photophysical properties, we have revealed a strong candidate as the ideal photosensitizer (PS) for applications, particularly in the realm of imaging. Spanning a remarkable size average between 1-4 nm, these particles exhibit both highly stable and unparalleled emission characteristics between 650 and 715 nm in water in comparison to current carbon dots (CDs) available. Lastly, these CDs were fairly non-toxic when tested against normal human cell lines as well as were found to have favorable imaging capabilities in zebrafish embryo.

Fluorescent carbon dots synthesized by waste wind turbine blade for photocatalytic degradation

Developing novel waste recycling strategies has become a feasible solution to overcome environmental pollution. In this work, a method of using waste wind turbine blade (WTB) as a carbon source to synthesize blue fluorescent carbon dots (B-CDs) by hydrothermal treatment is proposed. B-CDs are spherical and have an average particle size of 5.2 nm. The surface is rich in C-O, C=O, -CH3 , and N-H bond functional groups, containing five elements: C, O, N, Si, and Ca. The optimal emission wavelength of B-CDs is 463 nm, corresponding to an excitation wavelength of 380 nm. Notably, a relatively high quantum yield of 29.9% and a utilization rate of 40% were obtained. In addition, B-CDs can serve as a photocatalyst to degrade methylene blue dye, with a degradation efficiency of 64% under 40-min irradiation conditions. The presence of holes has a significant influence on the degradation process.

Preparation of Chiral Carbon Quantum Dots and its Application

Chiral carbon quantum dots (cCQDs) , as a new type of carbon nano-functional material with tunable emission wavelength, superior photostability, low toxicity, biocompatibility and chirality, are playing an increasingly important role in the fields of chemistry, biology and medicine. This paper reviews the preparation methods (one-step and two-step), optical properties (UV, fluorescence, chirality) and applications in chiral catalysis, chiral recognition, targeted imaging as well as other fields, while lists some of the issues and challenges in the research of chiral carbon quantum dots. Finally, due to its good fluorescence and other properties, it is expected that chiral carbon quantum dots will have broad commercial prospects in future applications.

One-step hydrothermal preparation of chiral carbon quantum dots and enantioselective sensing of glutamine enantiomeric isomers

A novel method for chiral identification of glutamine enantiomers based on chiral carbon quantum dots (cCQDs) fluorescent probes. cCQDs were prepared using a one-step hydrothermal method with L-tryptophan as the carbon source and chiral source, producing spherical nanoparticles exhibiting a blue colour luminescence. The fluorescence intensity (F) of cCQDs was enhanced or quenched following the addition of chiral enantiomeric glutamine (L/D-Gln), and therefore cCQDs, as a fluorescence probe, could be used for enantioselective sensing of the L/D-Gln. The fluorescence enhancement value (∆FE ) exhibited good linearity with L-Gln concentration in the range 0.23-10.00 mM, and the limit of detection was 0.14 mM. The fluorescence quenching value (∆FQ ) showed a good linear relationship with D-Gln concentration in the range 0.29-10.00 mM, and the detection limit was 0.18 mM. The mechanism of fluorescence enhancement/quenching was explored by molecular modelling and the type of quenching. The method was applied to the determination of L-Gln content in real samples, and the recovery rate was satisfactory. This study provided a novel approach for the synthesis of cCQDs and the recognition of amino acid enantiomers.

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.

Potential Efficacy of Herbal Medicine-Derived Carbon Dots in the Treatment of Diseases: From Mechanism to Clinic

Carbon dots (CDs), a crucial component of nanomaterials, are zero-dimensional nanomaterials with carbon as the backbone structure and smaller than 10 nm. Due to their beneficial characteristics, they are widely used in biomedical fields such as biosensors, drug delivery, bio-imaging, and interactions with DNA. Interestingly, a novel type of carbon dot, generated by using herbal medicines as synthetic raw materials, has emerged as the most recent incomer in the family of CDs with the extensive growth in the number of materials selected for carbon dots synthesis. Herbal medicine-derived carbon dots (HM-CDs) have been employed in the biomedical industry, and are rapidly emerging as "modern nanomaterials" due to their unique structures and exceptional capabilities. Emerging trends suggest that their specific properties can be used in bleeding disorders, gastrointestinal disorders, inflammation-related diseases, and other common intractable diseases including cancer, menopausal syndrome, central nervous system disorders, and pain of various forms and causes. In addition, HM-CDs have been found to have organ-protective and antioxidant properties, as evidenced by extensive studies. This research provides a more comprehensive understanding of the biomedical applications of HM-CDs for the aforementioned disorders and investigates the intrinsic pharmacological activities and mechanisms of these HM-CDs to further advance their clinical applications.

Carbon dots and their interactions with recognition molecules for enhanced nucleic acid detection

Carbon Dots (C-dots) have exceptional fluorescence and incident wavelength alteration capabilities because of their π-π* electron transitions between the surface-trapped charges. They have clear, considerate and cost-effective applications in the domain of bio-sensing, optical imaging, medical diagnostics, fluorescence chemotherapy, forensics, and environmentology. Advances in the production process of C-dots can change their optical and chemical characteristics, allowing them to interact with a variety of chemicals and ions that can be exploited for the DNA detection in point-of-care devices. In the current scenario of pathogenic disease prevention, metagenomics and industrial processes, alternative genetic material identification is critical. This review focuses on the existing carbon dots-based DNA detection technologies and their interactions with other components such as metallic salts, dyes, and biological chemicals based on their surface charge distribution (positive or negative) employed in the DNA diagnostic devices and biosensors with their operating mechanism regarding their target component. These intriguing scientific discoveries and technologies will be extensively examined to translate them into real-world solutions which will have a significant societal and economic impact on overall well-being and innovation.

Turning food waste into value-added carbon dots for sustainable food packaging application: A review

Carbon dots (CDs) are a recent addition to the nanocarbon family, encompassing both crystalline and amorphous phases. They have sparked significant research interest due to their unique electrical and optical properties, remarkable biocompatibility, outstanding mechanical characteristics, customizable surface chemistry, and negligible cytotoxicity. Their current applications are mainly limited to flexible photonic and biomedical devices, but they have also garnered attention for their potential use in intelligent packaging. The conversion of food waste into CDs further contributes to the concept of the circular economy. It provides a comprehensive overview of emerging green technologies, energy-saving reactions, and cost-effective starting materials involved in the synthesis of CDs. It also highlights the unique properties of biomass-derived CDs, focusing on their structural performance, cellular toxicity, and functional characteristics. The application of CDs in the food industry, including food packaging, is summarized in a concise manner. This paper sheds light on the current challenges and prospects of utilizing CDs in the packaging industry. It aims to provide researchers with a roadmap to tailor the properties of CDs to suit specific applications in the food industry, particularly in food packaging.

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.

Green synthesis of gardenia seeds-based carbon dots for bacterial imaging and antioxidant activity in aqueous and oil samples

In this work, luminescent carbon dots with gardenia seeds as carbon precursors (GCDs) were synthesized using a one-step mild pyrolysis process and were then used as probes for imaging of bacterial (Escherichia coli). The GCDs showed a strong emission at 430 nm when excited at 370 nm. The relative fluorescence quantum yield of GCDs was found to be 1.13% in an aqueous medium. Rapid internalization of the GCDs by bacteria was confirmed by three colors (blue, green, and yellow) images that were obtained using confocal fluorescence microscopy. In addition, GCDs were noted to exhibit potent scavenging activities against DPPH˙, ˙OH, and ˙O2- free radicals. GCDs were also assayed as antioxidants in an oil sample by volumetric determination of the peroxide value. Thus, GCDs exhibited good antioxidant properties both in aqueous and oil media. In addition, a free fatty acid quantification kit in the presence of GCDs showed enhanced fluorescence detection of palmitic acid with a remarkably good limit of detection of 0.08 μM, which is lower than that in the absence of GCDs (0.76 μM). The proposed fluorescence method was then successfully used to determine the concentration of palmitic acid spiked in milk powder samples, with spiked recoveries of 82.6-109.6% and relative standard deviations of 0.9-4.6%.

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.

Carbon dots: Types, preparation, and their boosted antibacterial activity by photoactivation. Current status and future perspectives

Carbon dots (CDs) correspond to carbon-based materials (CBM) with sizes usually below 10 nm. These nanomaterials exhibit attractive properties such us low toxicity, good stability, and high conductivity, which have promoted their thorough study over the past two decades. The current review describes four types of CDs: carbon quantum dots (CQDs), graphene quantum dots (GQDs), carbon nanodots (CNDs), and carbonized polymers dots (CPDs), together with the state of the art of the main routes for their preparation, either by "top-down" or "bottom-up" approaches. Moreover, among the various usages of CDs within biomedicine, we have focused on their application as a novel class of broad-spectrum antibacterial agents, concretely, owing their photoactivation capability that triggers an enhanced antibacterial property. Our work presents the recent advances in this field addressing CDs, their composites and hybrids, applied as photosensitizers (PS), and photothermal agents (PA) within antibacterial strategies such as photodynamic therapy (PDT), photothermal therapy (PTT), and synchronic PDT/PTT. Furthermore, we discuss the prospects for the possible future development of large-scale preparation of CDs, and the potential for these nanomaterials to be employed in applications to combat other pathogens harmful to human health. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Chitosan/Starch-Based Active Packaging Film with N, P-Doped Carbon Dots for Meat Packaging

Nitrogen, phosphorus-doped green-tea-derived carbon dots (NP-CDs) incorporated chitosan/starch (Chi/St) based multifunctional nanocomposite films were prepared. FE-SEM images verified a homogeneous distribution of CDs with minimum aggregation in the fabricated films. Incorporating NP-CDs led to enhanced UV-light blocking (93.1% of UV-A and ∼99.7% of UV-B) without significantly affecting the films' water transparency and water vapor permeability. Besides, incorporating NP-CDs into the Chi/St films enhanced antioxidant activity (98.0% for ABTS and 71.4% for DPPH) and displayed strong antibacterial activity against L. monocytogenes, E. coli, and S. aureus. Wrapping the meat in the prepared film and storing it at 20 °C has been shown to reduce bacterial growth (less than 2.5 Log CFU/g after 48 h) without significantly altering the actual color of the wrapped meat. The Chi/St film loaded with NP-CD has high potential as an active packaging material to ensure safety and extend the shelf life of meat products.

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.

Metal-doped carbon dots as robust nanomaterials for the monitoring and degradation of water pollutants

The contamination of the environment by domestic and industrial discharges is a relevant and persistent problem that needs novel solutions. Innovations in the detection, adsorption, and removal or in-situ degradation of toxic components are urgently required. Various effective techniques and materials have been proposed to address this problem, in which carbon dots (CDs) stand out because of their unique properties and low-cost and abundant nature. Their combination with different metals results in the enhancement of their innate properties. Metal-doped CDs have shown excellent results and competitive advantages in recent times. Considering the above useful critiques and CDs notable potentialities, this review discusses different approaches in detail to sense, adsorb, and photodegrade different pollutants in water samples. It was found that altering the electronic structure of CDs via metal doping has a great potential to enhance the optical, electrical, chemical, and magnetic capabilities of CDs, which in turn is beneficial for wastewater treatment.

Fighting Non-Small Lung Cancer Cells Using Optimal Functionalization of Targeted Carbon Quantum Dots Derived from Natural Sources Might Provide Potential Therapeutic and Cancer Bio Image Strategies

Non-small cell lung cancer (NSCLC) is an important sub-type of lung cancer associated with poor diagnosis and therapy. Innovative multi-functional systems are urgently needed to overcome the invasiveness of NSCLC. Carbon quantum dots (CQDs) derived from natural sources have received interest for their potential in medical bio-imaging due to their unique properties, which are characterized by their water solubility, biocompatibility, simple synthesis, and low cytotoxicity. In the current study, ethylene-diamine doped CQDs enhanced their cytotoxicity (98 ± 0.4%, 97 ± 0.38%, 95.8 ± 0.15%, 86 ± 0.15%, 12.5 ± 0.14%) compared to CQDs alone (99 ± 0.2%, 98 ± 1.7%, 96 ± 0.8%, 93 ± 0.38%, 91 ± 1.3%) at serial concentrations (0.1, 1, 10, 100, 1000 μg/mL). In order to increase their location in a specific tumor site, folic acid was used to raise their functional folate recognition. The apoptotic feature of A549 lung cells exposed to N-CQDs and FA-NCQDs was characterized by a light orange-red color under fluorescence microscopy. Additionally, much nuclear fragmentation and condensation were seen. Flow cytometry results showed that the percentage of cells in late apoptosis and necrosis increased significantly in treated cells to (19.7 ± 0.03%), (27.6 ± 0.06%) compared to untreated cells (4.6 ± 0.02%), (3.5 ± 0.02%), respectively. Additionally, cell cycle arrest showed a strong reduction in cell numbers in the S phase (14 ± 0.9%) compared to untreated cells (29 ± 0.5%). Caspase-3 levels were increased significantly in A549 exposed to N-CQDs (2.67 ± 0.2 ng/mL) and FA-NCQDs (3.43 ± 0.05 ng/mL) compared to untreated cells (0.34 ± 0.04 ng/mL). The functionalization of CQDs derived from natural sources has proven their potential application to fight off non-small lung cancer.

Biowaste-Derived Carbon Dots: A Perspective on Biomedical Potentials

Today, sustainable and natural resources including biowastes have been considered attractive starting materials for the fabrication of biocompatible and biodegradable carbon dots (CDs) due to the benefits of availability, low cost, biorenewability, and environmentally benign attributes. These carbonaceous nanomaterials have been widely explored in the field of sensing/imaging, optoelectronics, photocatalysis, drug/gene delivery, tissue engineering, regenerative medicine, and cancer theranostics. Designing multifunctional biowaste-derived CDs with a high efficacy-to-toxicity ratio for sustained and targeted drug delivery, along with imaging potentials, opens a new window of opportunity toward theranostic applications. However, crucial challenges regarding the absorption/emission wavelength, up-conversion emission/multiphoton fluorescence mechanisms, and phosphorescence of these CDs still need to be addressed to attain the maximum functionality and efficacy. Future studies ought to focus on optimizing the synthesis techniques/conditions, evaluating the influence of nucleation/growth process on structures/properties, controlling their morphology/size, and finding the photoluminescence mechanisms. Reproducibility of synthesis techniques is another critically important factor that needs to be addressed in the future. Herein, the recent developments related to the biowaste-derived CDs with respect to their biomedical applications are deliberated, focusing on important challenges and future perspectives.

Carbon Nanodots from an In Silico Perspective

Carbon nanodots (CNDs) are the latest and most shining rising stars among photoluminescent (PL) nanomaterials. These carbon-based surface-passivated nanostructures compete with other related PL materials, including traditional semiconductor quantum dots and organic dyes, with a long list of benefits and emerging applications. Advantages of CNDs include tunable inherent optical properties and high photostability, rich possibilities for surface functionalization and doping, dispersibility, low toxicity, and viable synthesis (top-down and bottom-up) from organic materials. CNDs can be applied to biomedicine including imaging and sensing, drug-delivery, photodynamic therapy, photocatalysis but also to energy harvesting in solar cells and as LEDs. More applications are reported continuously, making this already a research field of its own. Understanding of the properties of CNDs requires one to go to the levels of electrons, atoms, molecules, and nanostructures at different scales using modern molecular modeling and to correlate it tightly with experiments. This review highlights different in silico techniques and studies, from quantum chemistry to the mesoscale, with particular reference to carbon nanodots, carbonaceous nanoparticles whose structural and photophysical properties are not fully elucidated. The role of experimental investigation is also presented. Hereby, we hope to encourage the reader to investigate CNDs and to apply virtual chemistry to obtain further insights needed to customize these amazing systems for novel prospective applications.

Aristolochic Acid Nephropathy: A Novel Suppression Strategy of Carbon Dots Derived from Astragali Radix Carbonisata

Despite strict restrictions on the use of aristolochic acids (AAs)-containing merchandise or drugs in many countries, a substantial amounts of occurrences aristolochic acid nephropathy (AAN) had been accounted worldwide. Clinically, there is no effective incurable therapy regimen to reverse the progression of AAN. Although carbon dots have shown surprising bioactivity, research on the acute kidney injury caused by AAs is lacking. Here, a novel biomass-carbon dots from Astragali Radix (AR) as precursors was synthesized through one-step pyrolysis treatment. The ARC-carbon dots (ARC-CDs) was demonstrated in detail for its inhibitory effect on aristolochic acid nephropathy in a mice model. The indexes of inflammatory cytokines as well as oxidative stress were significantly reduced by the ARC-CDs in kidney tissue cells. Additionally, the ARC-CDs administration resulted in a large decrease in positive apoptotic cells according to TUNEL labeling and western blotting, which may be connected to the ARC-CDs’ modulation of the protein in the Akt/Mdm2/p53 signaling pathway. These findings show that ARC-CDs have remarkable anti-inflammatory, antioxidant, and anti-apoptotic capabilities against acute kidney injury spurred by aristolochic acids via the AKT/Mdm2/p53 signaling pathway.

Cationic Carbon Nanoparticles Induce Inflammasome-Dependent Pyroptosis in Macrophages via Lysosomal Dysfunction

Carbon nanomaterials, including carbon dots (CDs), form a growing family of engineered nanoparticles (NPs) with widespread applications. As the rapid expansion of nanotechnologies raises safety concerns, interaction of NPs with the immune system is receiving a lot of attention. Recent studies have reported that engineered NPs may induce macrophage death by pyroptosis. Therefore, this study investigated whether cationic CDs induce pyroptosis in human macrophages and assessed the role of inflammasome and lysosome in this process. Cationic CDs were synthetized by microwave-assisted pyrolysis of citric acid and high molecular weight branched polyethyleneimine. The NPs evoked a dose-dependent viability loss in THP-1-derived macrophages. A cell leakage, an increase in IL-1β secretion and an activation of caspase-1 were also observed in response to the NPs. Inhibition of caspase-1 decreased CD-induced cell leakage and IL-1β secretion, while restoring cell viability. Besides, CDs triggered swelling and loss of integrity of lysosome, and inhibition of the lysosomal enzyme cathepsin B decreased CD-induced IL-1β secretion. Thus, our data provide evidence that cationic CDs induce inflammasome-dependent pyroptosis in macrophages via lysosomal dysfunction.

Design, Synthesis, and Application of Carbon Dots With Synergistic Antibacterial Activity

The diversity of bacteria and their ability to acquire drug resistance lead to many challenges in traditional antibacterial methods. Photothermal therapies that convert light energy into localized physical heat to kill target microorganisms do not induce resistance and provide an alternative for antibacterial treatment. However, many photothermal materials cannot specifically target bacteria, which can lead to thermal damage to normal tissues, thus seriously affecting their biological applications. Here, we designed and synthesized bacteria-affinitive photothermal carbon dots (BAPTCDs) targeting MurD ligase that catalyzes the synthesis of peptidoglycan (PG) in bacteria. BAPTCDs presented specific recognition ability and excellent photothermal properties. BAPTCDs can bind to bacteria very tightly due to their chiral structure and inhibit enzyme activity by competing with D-glutamic acid to bind to MurD ligases, thus inhibiting the synthesis of bacterial walls. It also improves the accuracy of bacteria treatment by laser irradiation. Through the synergy of biochemical and physical effects, the material offers outstanding antibacterial effects and potentially contributes to tackling the spread of antibiotic resistance and facilitation of antibiotic stewardship.

Photoluminescent carbon dots (PCDs) from sour apple: a biocompatible nanomaterial for preventing UHMWPE wear-particle induced osteolysis via modulating Chemerin/ChemR23 and SIRT1 signaling pathway and its bioimaging application

Photoluminescent nanomaterials have been widely employed in several biological applications both in vitro and in vivo. For the first time, we report a novel application of sour apple-derived photoluminescent carbon dots (PCDs) for reducing ultra-high molecular weight polyethylene (UHMWPE) wear particle-induced osteolysis using mouse calvarial model. Generally, aseptic prosthetic loosening seems to be a significant postoperative problem for artificial joints replacement, which is mainly contributed by UHMWPE-induced osteolysis. Hence, inhibiting osteoclastic bone-resorption could minimize UHMWPE-induced osteolysis for implant loosening. Prior to osteolysis studies, the prepared sour apple-derived PCDs were employed for bioimaging application. As expected, the prepared PCDs effectively inhibited the UHMWPE particle-induced osteoclastogenesis in vitro. The PCDs treatment effectively inhibited the UHMWPE-induced osteoclast differentiation, F-actin ring pattern, and bone resorption in vitro. Also, the PCDs reduced the UHMWPE-induced ROS stress as well as the expression level of pro-inflammatory cytokines, including TNF-α, IL-1, IL-6, and IL-8. Further, the qPCR and western blot results hypothesized that PCDs inhibited the UHMWPE wear particle-induced osteolysis through suppressing chemerin/ChemR23 signaling and NFATc1 pathway, along with upregulation of SIRT1 expression. Overall, these findings suggest that the synthesized PCDs could be a potential therapeutic material for minimizing UHMWPE particle-induced periprosthetic osteolysis to avoid postoperative complications.

A Brief Review of Carbon Dots-Silica Nanoparticles Synthesis and their Potential Use as Biosensing and Theragnostic Applications

Carbon dots (CDs) are carbon nanoparticles with sizes below 10 nm and have attracted attention due to their relatively low toxicity, great biocompatibility, water solubility, facile synthesis, and exceptional photoluminescence properties. Accordingly, CDs have been widely exploited in different sensing and biomedical applications, for example, metal sensing, catalysis, biosensing, bioimaging, drug and gene delivery, and theragnostic applications. Similarly, the well-known properties of silica, such as facile surface functionalization, good biocompatibility, high surface area, and tunable pore volume, have allowed the loading of diverse inorganic and organic moieties and nanoparticles, creating complex hybrid nanostructures that exploit distinct properties (optical, magnetic, metallic, mesoporous, etc.) for sensing, biosensing, bioimaging, diagnosis, and gene and drug delivery. In this context, CDs have been successfully grafted into diverse silica nanostructures through various synthesis methods (e.g., solgel chemistry, inverse microemulsion, surfactant templating, and molecular imprinting technology (MIT)), imparting hybrid nanostructures with multimodal properties for distinct objectives. This review discusses the recently employed synthesis methods for CDs and silica nanoparticles and their typical applications. Then, we focus on combined synthesis techniques of CD-silica nanostructures and their promising biosensing operations. Finally, we overview the most recent potential applications of these materials as innovative smart hybrid nanocarriers and theragnostic agents for the nanomedical field.

Application of non-metal nanoparticles, as a novel approach, for improving the stability of blood products: 2011-2021

Despite the importance of the proper quality of blood products for safe transfusion, conventional methods for preparation and their preservation, they lack significant stability. Non-metal nanoparticles with particular features may overcome these challenges. This review study for the first time provided a comprehensive vision of the interaction of non-metal nanoparticles with each blood product (red blood cells, platelets and plasma proteins). The findings of this review on the most effective nanoparticle for improving the stability of RBCs indicate that graphene quantum dots and nanodiamonds show compatibility with RBCs. For increasing the stability of platelet products, silica nanoparticles exhibited a suppressive impact on platelet aggregation. Pristine graphene also shows compatibility with platelets. For better stability of plasma products, graphene oxide was indicated to preserve free human serum albumin from thermal shocks at low ionic strength. For increased stability of Factor VIII, mesoporous silica nanoparticles with large pores exhibit the superb quality of recovered proteins. Furthermore, 3.2 nm quantum dots exhibited anticoagulant effects. As the best promising nanoparticles for immunoglobulin stability, graphene quantum dots showed compatibility with γ-globulins. Overall, this review recommends further research on the mentioned nanoparticles as the most potential candidates for enhancing the stability and storage of blood components.

Chiral carbon dots: synthesis, optical properties, and emerging applications

Carbon dots are luminescent carbonaceous nanoparticles that can be endowed with chiral properties, making them particularly interesting for biomedical applications due to their low cytotoxicity and facile synthesis. In recent years, synthetic efforts leading to chiral carbon dots with other attractive optical properties such as two-photon absorption and circularly polarized light emission have flourished. We start this review by introducing examples of molecular chirality and its origins and providing a summary of chiroptical spectroscopy used for its characterization. Then approaches used to induce chirality in nanomaterials are reviewed. In the main part of this review we focus on chiral carbon dots, introducing their fabrication techniques such as bottom-up and top-down chemical syntheses, their morphology, and optical/chiroptical properties. We then consider emerging applications of chiral carbon dots in sensing, bioimaging, and catalysis, and conclude this review with a summary and future challenges.

Carbon dots: a novel platform for biomedical applications

Carbon dots (CDs) are a recently synthesised class of carbon-based nanostructures known as zero-dimensional (0D) nanomaterials, which have drawn a great deal of attention owing to their distinctive features, which encompass optical properties (e.g., photoluminescence), ease of passivation, low cost, simple synthetic route, accessibility of precursors and other properties. These newly synthesised nano-sized materials can replace traditional semiconductor quantum dots, which exhibit significant toxicity drawbacks and higher cost. It is demonstrated that their involvement in diverse areas of chemical and bio-sensing, bio-imaging, drug delivery, photocatalysis, electrocatalysis and light-emitting devices consider them as flawless and potential candidates for biomedical application. In this review, we provide a classification of CDs within their extended families, an overview of the different methods of CDs preparation, especially from natural sources, i.e., environmentally friendly and their unique photoluminescence properties, thoroughly describing the peculiar aspects of their applications in the biomedical field, where we think they will thrive as the next generation of quantum emitters. We believe that this review covers a niche that was not reviewed by other similar publications.

Multifunctional carbon quantum dots as a theranostic nanomedicine for fluorescence imaging-guided glutathione depletion to improve chemodynamic therapy

To minimize unwanted reactions with high concentrations of reduced glutathione (GSH) in the tumor microenvironment (TME) during chemodynamic therapy (CDT), a simple and effective strategy was developed to fabricate a TME stimuli-responsive theranostic nanomedicine (Fe-CD) for fluorescence imaging-guided GSH depletion and cancer therapy by combining fluorescent imaging carbon dots (CD) and Fe(III). Introducing Fe(III) into Fe-CD not only quenched the fluorescence of CD while reacting with and consuming intracellular GSH for fluorescence imaging of the depletion of GSH but also provided a source of metal ions to generate more abundant hydroxyl radicals (•OH) with hydrogen peroxide (H₂O₂) through the Fenton reaction to improve CDT. Fe-CD showed promising •OH generation under H₂O₂ to effectively degrade methylene blue in vitro and obviously activate the green fluorescence of the reactive oxygen species (ROS) probe in cells. Benefiting from the fluorescence enhancement in response to TME stimulation, Fe-CD greatly enhanced CDT cytotoxicity while monitoring successful GSH depletion by fluorescence imaging. Fe-CD has the potential to act as a theranostic nanomedicine for fluorescence imaging-guided GSH depletion to amplify CDT.

Ultra-bright carbon quantum dots for rapid cell staining

A schematic illustration of the synthesis of G-CDs and cell imaging under one-photon and two-photon conditions.

In Vivo Biodistribution, Clearance, and Biocompatibility of Multiple Carbon Dots Containing Nanoparticles for Biomedical Application

Current research on the use of carbon dots for various biological systems mainly focuses on the single carbon dots, while particles that contain multiple carbon dots have scarcely been investigated. Here, we assessed multiple carbon dots-crosslinked polyethyleneimine nanoparticles (CDs@PEI) for their in vivo biodistribution, clearance, biocompatibility, and cellular uptake. The in vivo studies demonstrate three unique features of the CDs@PEI nanoparticles: (1) the nanoparticles possess tumor-targeting ability with steady and prolonged retention time in the tumor region. (2) The nanoparticles show hepatobiliary excretion and are clear from the intestine in feces. (3) The nanoparticles have much better biocompatibility than the polyethyleneimine passivated single carbon dots (PEI-CD). We also found that pegylated CDs@PEI nanoparticles can be effectively taken up by the cells, which the confocal laser scanning microscope can image under different excitation wavelengths (at 405, 488, and 800 nm). These prior studies provide invaluable information and new opportunities for this new type of intrinsic photoluminescence nanoparticles in carbon dot-based biomedical applications.

Herbal medicine derived carbon dots: synthesis and applications in therapeutics, bioimaging and sensing

Since the number of raw material selections for the synthesis of carbon dots (CDs) has grown extensively, herbal medicine as a precursor receives an increasing amount of attention. Compared with other biomass precursors, CDs derived from herbal medicine (HM-CDs) have become the most recent incomer in the family of CDs. In recent ten years, a great many studies have revealed that HM-CDs tend to be good at theranostics without drug loading. However, the relevant development and research results are not systematically reviewed. Herein, the origin and history of HM-CDs are outlined, especially their functional performances in medical diagnosis and treatment. Besides, we sort out the herbal medicine precursors, and analyze the primary synthetic methods and the key characteristics. In terms of the applications of HM-CDs, medical therapeutics, ion and molecular detection, bioimaging, as well as pH sensing are summarized. Finally, we discuss the crucial challenges and future prospects.