Biocompatible Carbon Dots Research Articles

Tunable KLa(MoO4)2:Eu3+@CDs composite materials for white LED and multi-mode information encryption technology

The composite of biocompatible carbon dots (CDs) and lanthanide-based luminescent materials have high research value as a promising multifunctional material, which are ideally suited to information encryption and white LED. However, the aggregation-induced quenching of CDs in the solid state still troubles the synthesis of CDs with other solid luminescent materials. Herein, a facile strategy to fabricate polychromatic nanoplatform KLa(MoO4)2: Eu3+@CDs by encapsulating CDs on the surface of KLM: Eu3+ with silicon shell is reported, in which the aggregation-induced quenching of CDs is avoided. Due to the overlapping of Eu-O charge transfer band with CDs excitation band, the red luminescence of Eu3+ ions and the blue fluorescence of can be emitted simultaneously under 395 nm excitation. By changing the proportion of KLa(MoO4)2: Eu3+ in KLa(MoO4)2: Eu3+@CDs, the mixture can emit "warm", "neutral", and "cold" white light, which can realize people's demand for indoor lighting requirements. Furthermore, a multi-mode information encryption by selectively triggering the luminescence of CDs or Eu3+ ions is also designed. All the results suggest that KLa(MoO4)2: Eu3+@CDs have excellent luminescence properties that can be further investigated and applied in the field of white LEDs and information encryption.

Biocompatible Ruthenium Single-Atom Catalyst for Cascade Enzyme-Mimicking Therapy.

Rationally constructing single-atom enzymes (SAEs) with superior activity, robust stability, and good biocompatibility is crucial for tumor therapy but still remains a substantial challenge. In this work, we adopt biocompatible carbon dots as the carrier material to load Ru single atoms, achieving Ru SAEs with superior multiple enzyme-like activity and stability. Ru SAEs behave as oxidase, peroxidase, and glutathione oxidase mimics to synchronously catalyze the generation of reactive oxygen species (ROS) and the depletion of glutathione, thus amplifying the ROS damage and finally causing the death of cancer cells. Notably, Ru SAEs exhibit excellent peroxidase-like activity with a specific activity of 7.5 U/mg, which surpasses most of the reported SAEs and is 20 times higher than that of Ru/C. Theoretical results reveal that the electrons of the Ru 4d orbital in Ru SAEs are transferred to O atoms in H2O2 and then efficiently activate H2O2 to produce •OH. Our work may provide some inspiration for the design of SAEs for cancer therapy.

Carbon dots: Discovery, structure, fluorescent properties, and applications

Abstract Nanotechnology has become one of the most important topics since the beginning of the twenty-first century in numerous fields including drug synthesis and delivery, environmental protection, electronics manufacture, and astronomy due to their nanoscale particles and their properties. The traditional semi-quantum dots are replaced by a new category of fluorescent carbon nanomaterials. Carbon dots (CDs) have been explored in the last few years for their simple synthetic accession, good bio-consonance, and several revelation applications. This review explains the fluorescent properties of CDs in brief, giving also a background on CDs discovery, structure, and composition, as well as on nanocomposites, green synthesis, and their applications. Resources conservation can be achieved by using recycled substances for sustainable development which lead to a new technology. Fluorescent CDs synthesized from food wastes like bananas, orange peel waste, sugarcane bagasse, Trapa bispinosa peels, bread, and jaggery have several applications such as sensing, drug delivery, gene transfer, biological imaging, and food safety. In this study, we concentrate on CDs greener methods to prepare effective and biocompatible CDs.

Controllable Synthesis of Biocompatible Fluorescent Carbon Dots From Cellulose Hydrogel for the Specific Detection of Hg2.

Heavy metal ions overload can seriously harm human health. Simple and effective strategies for the specific detection of heavy metal ions are of great important. In this work, using different pretreatment methods, a series of carbon dots (CDs) with different particle sizes and doped with varying amounts of elements (O, N, S) were prepared based on the natural polymer, cellulose hydrogel. The CDs exhibit excellent fluorescence and biocompatibility. When the particle size decreased from 8.72 to 2.11 nm, the fluorescence quantum yield increased from 0.029 to 0.183. In addition, doping with elements (N) also effectively enhanced the fluorescent performance of the CDs. The fluorescence of the CDs, especially for the smallest, CD-4a, was significantly quenched in the presence of the heavy metal ion, Hg2+. Thus, CD-4a may be used as a fluorescence sensor for the detection of Hg2+. The fluorescence intensity of CD-4a exhibited a two-stage, concentration-dependent fluorescence response in the range 0.2–10 and 10–100 μmol/L Hg2+, with each stage having different slopes; the detection limit was 0.2 μM. More importantly, even in the presence of interfering metal ions, the detection of Hg2+ using the CDs-4a remained stable. Therefore, these biocompatible CDs may serve as a promising candidate for the specific detection of Hg2+.

Modulating the physicochemical and biological properties of carbon dots synthesised from plastic waste for effective sensing of E. coli

The reliable means for the quick recognition of pathogenic bacteria for disease prevention has acquired a considerable significance among researchers for human wellbeing. The purpose of current study is to fabricate highly photo-luminescent and biocompatible carbon dots (CQDs) from single used plastic waste such as poly bags, cups and bottles for selective sensing of E. coli. The formed small sized spherical CQDs have possessed high water solubility with excellent photo stable nature. The detailed fluorescence emission studies of CQDs have illustrated the overview of different types of surface defects and emissive states in formed particles. In addition, the specific role of prepared CQDs with bio-compatible nature has been thoroughly checked on hemolysis of red blood cells by employing in-vitro blood compatibility assay. A combination of anticoagulant and thrombolytic activity of CQDs with anti-oxidative activities from reactive oxygen species (ROS) generation were found to be responsible for the biocompatibility of formed CQDs. The effective in vitro stability toward histidine, cysteine, bovine serum albumin (BSA), human serum albumin (HSA) and saline supported the biocompatibility of formed particles as a function of different concentrations of CQDs. The optimized fluorescence properties with high surface to volume ratio of CQDs have provided a better alternative for “turn-off” fluorescence detection of E. coil in aqueous media with limit of detection down to 108 CFU/mL estimated by using standard colony-counting method. The as prepared nanosensor provided easy fabrication with fast response, high sensitivity and selectivity in real water samples which might be necessary for detecting pathogenic agents. In addition, the current work has provided the large overview in blood compatibility and anti-oxidative potential of prepared CQDs and giving useful information for preparing blood–compatible nanoparticles with enhanced bacterial discrimination ability.

Biogenic approach for fabricating biocompatible carbon dots and their application in colorimetric and fluorometric sensing of lead ion

The rapid growth in the industrial and urban sector has filled enormous stress on environment. The exponential use of chemicals especially metal ions has raised the pollution index and affected the health of living beings. Therefore, it is highly essential need to monitor and remove these metal ion toxins by the advanced materials which itself non-lethal, bio-congenial and easily workable with high selectivity and sensitivity. To solve these issues, the current study proposed the efficient utilization of Pearl Millet seeds into value-added carbon dots (C-dots) via using simple thermal treatment. Engaging agricultural product as a starting precursor for C-dots synthesis made the process economically more viable. The basic structural properties (size ∼ 4–5 nm, shape ∼ spherical, and crystalline nature) were assessed through HRTEM, PXRD, FTIR and EDX analysis. The optical and luminescence properties were appraised by investigating the variation in the absorbance and emission intensity as a function of pH (2–12) and excitation wavelength (245 nm–305 nm). The developed strategy has provided the better control over the aqueous solubility, quantum yield (52%) and optical properties of C-dots. The high loading amounts of C-dots ranging from 100 to 5000 mg/L has produced a significant enhancement in the biocompatibility rate of C-dots against bacterial strains, fungus, algae, chromosomal compatibility on Allium cepa and seeds germination activity of Vigna radiate. The strong fluorescence emission and optical properties of as prepared C-dots made them efficient for selective and sensitive detection of Pb2+ ion (detection limit = 0.18 nM) from waste water via using colorimetric, UV–vis. absorption and fluorescence based sensory methods. The development sensor performed well in water obtained from different natural resources with 90% average recovery rate. These findings would make the economically feasible C-dots as an effective material for wastewater treatment via overcoming the barriers of low selectivity and advanced the implementation of the process on large scale. Furthermore, the usage of biowaste as starting precursor offers a solution for ecological burdens while synchronically reducing the pernicious effect of the waste on the ecosystem and cleans up the environment.

Biocompatible carbon dots with low-saturation-intensity and high-photobleaching-resistance for STED nanoscopy imaging of the nucleolus and tunneling nanotubes in living cells

Many kinds of nanoparticles and organic dyes as fluorescent probes have been used in the stimulated emission depletion (STED) nanoscopy. Due to high toxicity, photobleaching and non-water solubility, these fluorescent probes are hard to apply in living cell imaging. Here, we report a new fluorescence carbon dots (FNCDs) with high photoluminescence quantum yield (56%), low toxicity, anti-photobleaching and good water-solubility that suitable for live-cell imaging can be obtained by doping fluorine element. Moreover, the FNCDs can stain the nucleolus and tunneling nanotubes (TNTs) in the living cell. More importantly, for STED nanoscopy imaging, the FNCDs effectively depleted background signals and improved imaging resolution. Furthermore, the lateral resolution of single FNCDs size under the STED nanoscopy is up to 22.1 nm for FNCDs deposited on a glass slide was obtained. And because of their good water dispersibility, the higher resolution of single FNCDs size in the nucleolus of a living cell can be up to 19.7 nm. After the image optimization steps, the fine fluorescence images of TNTs diameter with ca. 75 nm resolution is obtained living cell, yielding a threefold enhancement compared with that in confocal imaging. Additionally, the FNCDs show excellent photobleaching resistance after 1,000 scan cycles in the STED model. All results show that FNCDs have significant potential for application in STED nanoscopy.

Blue-fluorescent and biocompatible carbon dots derived from abundant low-quality coals

Coal is one of the most abundant natural carbonaceous materials. This paper reports a novel oxidative chemical method for the synthesis of high-value carbon dots (CDs) from cheap and abundant low-quality high‑sulfur coals for use in high-end applications. These CDs were synthesized by using wet-chemical ultrasonic stimulation-induced process which is environmentally facile and less drastic compared to other chemical methods of production of CDs. The sizes of the synthesized CDs from different types of coal samples were estimated to be in the range of 1–4 nm, 1–6 nm, 2–5 nm, and 10–30 nm. The quantum yield (QY) of the CDs was determined and it was found to be around 3–14%. For high-end field application, the CDs were further tested for toxicity and were reported to be safe for environmental and biological applications. The cell image analysis under the fluorescence microscope further indicated that the synthesized CDs could be used as a promising bio-compatible material for optical-imaging as well as bio-imaging. The CDs showed promising fluorescent sensing property and can be utilized as a good probe for silver ion detection/sensing. The CDs is also found to be a promising reagent for silver nanoparticles synthesis. The results provide a new avenue for large-scale synthesis of CDs.

Biocompatible carbon dots derived from κ-carrageenan and phenyl boronic acid for dual modality sensing platform of sugar and its anti-diabetic drug release behavior.

Detection of sugar by enzymatic assay has been suffering from costly, time-taking, instable and denaturation of glucose oxidase. Recently, chemosensors that have affinity towards boronate became the hot topic in the domain of monosaccharide detection. In this work, a novel strategy was addressed to fabricate carbon dots (C-dots) from linear sulfated polysaccharides κ- carrageenan and phenyl boronic acid for nonenzymatic monosaccharide (glucose) detection. The boronic acid group anchored C-dots surface can form assembly by covalently bonded with the cis-diol moiety of the glucose which caused fluorescence quenching of the C-dots. The inert surface nature of the luminescent C-dots enables them to sense as low as 1.7 μM glucose without the interference of other biomolecules. The proposed sensing system was successfully applied for assay of glucose in blood serum. Interestingly, these C-dots were used as a nano vehicle for delivery of anti-diabetic drug Metformin. Good biocompatibility results were found with MTT and hemolysis assay. Owing to its simplicity and effectiveness, the as-prepared C-dots offered great promise for blood sugar diagnosis and treatment.

Hydroxyl functionalized carbon dots with strong radical scavenging ability promote cell proliferation

Bioactivity of carbon dots (CDs) has received much attention, in which, the effects on cell proliferation and viability are more crucial for tissue engineering and regeneration. In this study, we report the fabrication of a biocompatible carbon dots with rich hydroxyl groups (CDs-OH) by a one-step hydrothermal treatment from phloroglucinol and phenol. The as-prepared CDs-OH possess strong fluorescence, excellent photostability and low cytotoxicity. We also show that the CDs-OH could scavenge free radical groups. As free radical scavenger, the CDs-OH is proved to exhibit explicit capability to stimulate cell proliferation, which depends on the hydroxyl groups content in CDs-OH. These properties promise the potential use of CDs-OH in medical fields, especially tissue engineering and regeneration.

Multipurpose sensing applications of biocompatible radish-derived carbon dots as Cu2+ and acetic acid vapor sensors.

A recent trend in the preparation of carbon dots, optically unique nanomaterials, revolves around the use of readily-available, low-cost natural resources as precursors and their multipurpose applications. In this work, a hydrothermal method for preparing biocompatible carbon dots from radish was developed. The carbon dots were then tested for sensing of Cu2+ and acetic acid vapor. The carbon dots exhibited blue emission under UV illumination with, a quantum yield of 15%. The fluorescence emission was selectively quenched when Cu2+ ions were added, giving a detection limit of 0.16 μM. A paper-based fluorescent sensor was fabricated and shown to sense Cu2+ with a limit of detection of 6.8 μM. The carbon dots were able to determine the Cu2+ concentration in real water samples, with excellent recovery and reliability. The carbon dots were also used as the sensing material in an optical electronic nose, and tested for real-time detection of acetic acid vapor. Using principal component analysis, different ratios of acetic acid to methanol in solution were successfully identified with a detection limit of 15.5%. The acetic acid concentration in a real vinegar sample was also accurately determined. Our results demonstrated that label-free carbon dots derived from readily available radish can be simply used as versatile probes, giving them potential uses in multipurpose sensing applications.

Synthesis of biocompatible carbon dots from yogurt and gas vapor sensing

Carbon dots are fascinating nanomaterials due to their low cost, straightforward preparation, unique optical properties, and biocompatibility. In this work, carbon dots were prepared from yogurt using pyrolysis method. The carbon dots were characterized using UV-visible spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. The carbon dots were applied for detecting formic acid vapor using electronic nose system. Furthermore, the biocompatibility of carbon dots were investigated to show their potentials for biomedical applications. Based on these research, carbon dots from yogurt were multifunctional fluorescent nanomaterials for various applications.

Highly biocompatible yogurt-derived carbon dots as multipurpose sensors for detection of formic acid vapor and metal ions

Carbon dots are fascinating nanomaterials given their straightforward synthesis, unique optical properties, sensing capabilities, and biocompatibility. In this work, biocompatible carbon dots were prepared from yogurt using a two-step pyrolysis/hydrothermal method. The dots were spherical in shape with an average size of 4.7 nm. They showed blue emission under UV illumination with a quantum yield of 1.5%. Their photoluminescence was stable over three months and in both strong buffer solutions and highly concentrated salt solutions. The optical absorption and photoluminescence properties of the dots were employed for vapor and metal ion sensing, respectively. For the first time, the carbon dots were integrated into an optical electronic nose, and used for the detection of formic acid vapor at room temperature. Sensing was based on monitoring the optical transmission through a carbon dot film upon exposure to vapor, and the results were confirmed by UV–visible spectroscopy. The carbon dot-integrated electronic nose was able to distinguish vapor from formic acid/water solutions at different concentrations, with a detection limit of 7.3% v/v. The sensitivity of the dots to metal ions was tested by measuring the photoluminescence emission intensity at different excitation wavelengths. Principal component analysis was used to differentiate between the ions. The results suggested that interactions between carbon dots and metals ions occurred at a range of binding sites. The biocompability of the dots was demonstrated to be excellent. The study identified carbon dots produced from yogurt as multipurpose fluorescent nanomaterials with potential sensing and biomedical applications.

Mercury (II) detection by water-soluble photoluminescent ultra-small carbon dots synthesized from cherry tomatoes

Mercury ions have been considered highly toxic to human health. What would be great is to develop the ionic probes without any toxicities themselves. Here, we report a friendly, highly sensitive mercury (II) ionic probe, water-soluble photoluminescence carbon dots which were synthesized by simply hydrothermal treatment of fresh cherry tomatoes without adding any other reagents. The ultra-small (<1 nm) carbon dots show robust excitation-depended photoluminescence under a wide pH range (4–10) or a strong ionic strength of up to 1 M, and the detection limit of mercury (II) has been determined as low as 18 nM. We envision such water-soluble, biocompatible carbon dots that could be applied to biolabeling, bio-imaging, and biosensing fields.

Biocompatible Carbon Dots Clusters with Tunable Sizes for Bioimaging Application

Carbon dots (Cdots) have been widely applied in labeling cellular or subcellular targets with high resolution due to their small sizes and benign biocompatibility. However, their use for in vivo application suffered from the rapid renal clearance due to their tiny size (c.a. [Formula: see text]6[Formula: see text]nm in diameter). To overcome the drawback, we herein report a sonication assisted method for the preparation of Cdots clusters with tunable sizes. Pluronic F127 was used as the carrier to form the clusters and the feeding ratio of the Cdots to F127 was varied in order to tune the sizes of clusters. The clusters were also successfully demonstrated in cell imaging applications with high brightness. Together with their low cytotoxicity, the clusters are potential for bioimaging applications. Hence, this work provides a convenient engineering strategy to prepare Cdots clusters with tunable sizes for bioimaging applications.

Controlled delivery of dopamine hydrochloride using surface modified carbon dots for neuro diseases

Delivery of therapeutic agents using water-soluble, highly biocompatible Carbon dots (C-dots) is an efficient strategy to control drug release under physiological milieu. Dopamine hydrochloride (DA), the most important inotropic vasopressor agent used in neurological diseases. In our study DA is anchored to water-soluble carbon dots for controlled release under mimicked in vitro physiological conditions. The tenure of the DA release at pH 7.4 was greatly extended to 60h for C-dots–DA, in comparison with the control DA alone. The statistical calculation was used to comprehend the release pattern of the DA, which exhibited the pattern of Hixson–Crowell model of release. In order to understand the impact of the C-dots–DA conjugate under physiological conditions, Neuro 2A cells were taken under consideration. The conjugate C-dots–DA was found to be biocompatible against Neuro 2A cells. The survival rate was found to be 74% at maximum concentration of 9μgmL−1. In vivo toxicity was studied using thin section of tissues after staining with Hematoxyline and Eosin Yellow (H&E). As per microscopic observations, conjugates did not inflict any anatomical distortions or hostile effects on tissues. Body weight of mice was also taken into consideration after injecting 20μgmL−1 of nano-conjugates via tail vein. The impact of nano-conjugate on body weight was found to be negligible after 45 days of observation.

Fluorescent detection of Mucin 1 protein based on aptamer functionalized biocompatible carbon dots and graphene oxide

An ultrasensitive aptasensor for the detection of Mucin 1 (MUC1) protein based on fluorescence resonance energy transfer (FRET) between carbon dots (CDs) and graphene oxide (GO) is reported herein.

Super-resolution fluorescence imaging of biocompatible carbon dots.

Carbon Dots (CDs) are a new promising type of small (5 nm), biocompatible and multicolor luminescent nanoparticle. Here, we demonstrate super-resolution imaging of CDs at the nanoscale through STimulated Emission Depletion (STED) microscopy. In addition, we report the application of STED for detection of CD localization in both fixed and living cells, achieving a spatial resolution down to 30 nm, far below the diffraction limit, showing great promise for high resolution visualization of cellular dynamics.

Preparation of highly luminescent and biocompatible carbon dots using a new extraction method

C dots (CDs) are among the most promising emerging fluorescent labels for biological imaging and sensing. A facile new synthesis method was developed using common organic solvents for fabricating CDs from candle soot. The common organic solvents were used as extractants and the obtained CDs have a narrow size distribution with average diameters of about 3.4 nm for ethylene glycol, 3.5 nm for ethanol, and 3.4 nm for n-butanol. This approach is simpler, easier, and more effective than other methods currently used for CD fabrication. The obtained CDs had a high quantum yield (38 %), tunable emission and are water-soluble. The mechanism for the luminescence of the CDs was investigated and the results indicate that the ability of the solvent to disperse the CDs plays a very important role in the photoluminescence of these CDs. The type of organic solvent and the surface groups on the CDs also influenced the optical properties of the CDs. Different emissive traps are shown to play the major role in the luminescence of the carbon materials. An in vitro hemolysis assay was performed and showed that the CDs are biocompatible.

Luminescent Carbon Dot-Gated Nanovehicles for pH-Triggered Intracellular Controlled Release and Imaging

In this paper, the use of biocompatible carbon dots (C-Dots) as caps on the surface of mesoporous silica nanoparticles (MSPs) for the design of intelligent on-demand molecular delivery and cell imaging system is described. These C-Dots-attached MSPs exhibited low cytotoxicity toward the cells and strong luminescence both in vitro and in vivo. A further loading of anticancer drug (DOX) endowed the fluorescent material with therapeutic functions. It was found that changing the pH to mildly acidic condition at physiological temperature caused the dissociation of the C-Dots@MSPs complex and release of a large number of DOX from the nanospheres. Moreover, the DOX-loaded nanocomposites exhibited a remarkably enhanced efficiency in killing cancer cells. The endocytosis and the efficient drug release properties of the system were confirmed by luminescence microscopy. Overall, we believe that the well-designed C-Dots@MSPs nanocomposites are promising for a simultaneous bioimaging and drug delivery system, which show more potential for clinical application.