Preparation and biological evaluation of photoluminescent carbonaceous nanospheres

Physicochemical characteristics that affect carbon dot safety: Lessons from a comprehensive study on a nanoparticle library

Carbon dots (CDs) are emerging nanomaterial in medicine and pharmacy. To explore the impact of physicochemical characteristics on their safety, we synthesized a library of 35 CDs exhibiting different size, charge, chemical composition and surface coating, using various starting materials (carbon source and passivation reagent) and carbonization procedures. The 35 CDs triggered different levels of viability loss when incubated with human macrophages at 3-200 µg/mL for 24 h. The smaller NPs (10-20 nm) were more toxic that larger ones (40-100 nm), whereas NPs that aggregated in culture medium were more toxic than dispersed ones. A positive correlation was found between CD charge or nitrogen content and toxicity. Furthermore, a greater toxicity was observed for CDs prepared from high molecular weight polyamines, suggesting a role of the CD global density of positive charges, rather than the charge at the CD surface, in the CD toxicity. At last, PEG decoration decreased the toxicity of cationic NPs. In conclusion, the size, aggregation in culture medium, charge, nitrogen content, nature of the passivation agent and synthesis procedure were found to influence CD toxicity, making it difficult to predict CD safety from a single characteristic.

Polyethylene glycol modification decreases the cardiac toxicity of carbonaceous dots in mouse and zebrafish models

AIM

Carbonaceous dots (CDs), which have been used for diagnosis, drug delivery and gene delivery, are accumulated in heart at high concentrations. To improve their biocompatibility, polyethylene glycol-modified CDs (PEG-CDs) were prepared. In this study we compared the cardiac toxicity of CDs and PEG-CDs in mouse and zebrafish models.

METHODS

Mice were intravenously treated with CDs (size: 4.9 nm, 5 mg·kg(-1)·d(-1)) or PEG-CDs (size: 8.3 nm, 5 mg·kg(-1)·d(-1)) for 21 d. Their blood biochemistry indices, ECG, and histological examination were examined for evaluation of cardiac toxicity. CDs or PEG-CDs was added in incubator of cmlc2 transgenic Zebrafish embryos at 6 hpf, and the shape and size of embryos' hearts were observed at 48 hpf using a fluorescent microscope. Furthermore, whole-mount in situ hybridization was used to examine the expression of early cardiac marker gene (clml2) at 48 hpf.

RESULTS

Administration of CDs or PEG-CDs in mice caused mild, but statistically insignificant reduction in serum creatine kinase (CK) and lactate dehydrogenase (LDH) levels detected at 7 d, which were returned to the respective control levels at 21 d. Neither CDs nor PEG-CDs caused significant changes in the morphology of heart cells. Administration of CDs, but not PEG-CDs, in mice caused marked increase of heart rate. Both CDs and PEG-CDs did not affect other ECG parameters. In the zebrafish embryos, addition of CDs (20 μg/mL) caused heart development delay, whereas addition of CDs (80 μg/mL) led to heart malformation. In contrast, PEG-CDs caused considerably small changes in heart development, which was consistent with the results from the in situ hybridization experiments.

CONCLUSION

CDs causes greater cardiac toxicity, especially regarding heart development. Polyethylene glycol modification can attenuate the cardiac toxicity of CDs.

Direct Solvent-Derived Polymer-Coated Nitrogen-Doped Carbon Nanodots with High Water Solubility for Targeted Fluorescence Imaging of Glioma

Cancer imaging requires biocompatible and bright contrast-agents with selective and high accumulation in the tumor region but low uptake in normal tissues. Herein, 1-methyl-2-pyrrolidinone (NMP)-derived polymer-coated nitrogen-doped carbon nanodots (pN-CNDs) with a particle size in the range of 5-15 nm are prepared by a facile direct solvothermal reaction. The as-prepared pN-CNDs exhibit stable and adjustable fluorescence and excellent water solubility. Results of a cell viability test (CCK-8) and histology analysis both demonstrate that the pN-CNDs have no obvious cytotoxicity. Most importantly, the pN-CNDs can expediently enter glioma cells in vitro and also mediate glioma fluorescence imaging in vivo with good contrast via elevated passive targeting.

Non-invasive imaging of breast cancer using RGDyK functionalized fluorescent carbonaceous nanospheres

RGD functionalized carbonaceous dots were prepared and utilized for non-invasive breast cancer imaging.

A facile hydrothermal approach towards photoluminescent carbon dots from amino acids

A facile one-pot method to fabricate photoluminescent carbon dots (CDs) was developed by the hydrothermal treatment of amino acids at mild temperatures. Derived from three different kinds of amino acids including serine, histidine, and cystine, the resultant CDs show uniform spherical morphology with the diameters in the range of ∼2.5-4.7nm. These amino acid derived CDs also manifest excellent photoluminescence behavior with the quantum yields (QYs) of ∼7.5% and high stability. More importantly, this method provides the opportunity to modify the sizes, structures, and photoluminescent behavior of CDs by the utilization of diversified amino acids with different structural characteristics.

A simple one-step method to prepare fluorescent carbon dots and their potential application in non-invasive glioma imaging

Fluorescent carbon dots (CD) possess impressive potential in bioimaging because of their low photobleaching, absence of optical blinking and good biocompatibility. However, their relatively short excitation/emission wavelengths restrict their application in in vivo imaging. In the present study, a kind of CD was prepared by a simple heat treatment method using glycine as the only precursor. The diameter of CD was lower than 5 nm, and the highest emission wavelength was 500 nm. However, at 600 nm, there was still a relatively strong fluorescent emission, suggesting CD could be used for in vivo imaging. Additionally, several experiments demonstrated that CD possessed good serum stability and low cytotoxicity. In vitro, CD could be taken up into C6 glioma cells in a time- and concentration-dependent manner, with both endosomes and mitochondria involved. In vivo, CD could be used for non-invasive glioma imaging because of its high accumulation in the glioma site of the brain, which was demonstrated by both in vivo imaging and ex vivo tissue imaging. Furthermore, the fluorescent distribution in tissue slices also showed CD distributed in glioma with high intensity, while with a low intensity in normal brain tissue. In conclusion, CD were prepared using a simple method with relatively long excitation and emission wavelengths and could be used for non-invasive glioma imaging.

Green chitosan-carbon dots nanocomposite hydrogel film with superior properties

In this work we report novel chitosan-carbon dots nanocomposite hydrogel films. A new green source "tea" was used as precursor for carbon dots (CDs). The electrostatic interaction of positive charge on chitosan and negative charge on CDs prepared from tea was used for the successful preparation of a stable and robust chitosan-carbon dots nanocomposite hydrogel film. The hydrogel films were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transformed infra-red spectroscopy (FTIR), scanning electron microscope (SEM), fluorescent microscopy, thermogravimetric analysis (TGA) and contact angle analysis. It was observed that chitosan-carbon dots hydrogel films are soft but tough with superior UV-visible blocking, swelling, thermal and mechanical properties in comparison to chitosan hydrogel film. Moreover chitosan-carbon dots films are more water repellent (hydrophobic) as indicated by their high contact angle values. Thus, fabrication of such green soft but tough biocompatible chitosan-carbon dots nanocomposite hydrogel films offers tremendous bio-medical and industrial applications.