Phosphorus and Nitrogen Dual-Doped Hollow Carbon Dot as a Nanocarrier for Doxorubicin Delivery and Biological Imaging

The Low Toxicity of Graphene Quantum Dots is Reflected by Marginal Gene Expression Changes of Primary Human Hematopoietic Stem Cells

Graphene quantum dots (GQDs) are a promising next generation nanomaterial with manifold biomedical applications. For real world applications, comprehensive studies on their influence on the functionality of primary human cells are mandatory. Here, we report the effects of GQDs on the transcriptome of CD34+ hematopoietic stem cells after an incubation time of 36 hours. Of the 20 800 recorded gene expressions, only one, namely the selenoprotein W, 1, is changed by the GQDs in direct comparison to CD34+ hematopoietic stem cells cultivated without GQDs. Only a meta analysis reveals that the expression of 1171 genes is weakly affected, taking into account the more prominent changes just by the cell culture. Eight corresponding, weakly affected signaling pathways are identified, which include, but are not limited to, the triggering of apoptosis. These results suggest that GQDs with sizes in the range of a few nanometers hardly influence the CD34+ cells on the transcriptome level after 36 h of incubation, thereby demonstrating their high usability for in vivo studies, such as fluorescence labeling or delivery protocols, without strong effects on the functional status of the cells.

Carbon Dots for In Vivo Bioimaging and Theranostics

Carbon dots (CDs), a kind of carbon material discovered accidentally, exhibit unexpected advantages in fluorescence imaging/sensing such as photostability, biocompatibility, and low toxicity. For emerging theranostics, an interdiscipline created by integrating therapy and diagnostics, CDs are good candidates when they are combined with targeted chemo/gene/photodynamic/photothermal therapeutic moieties. Here, the development of CDs in nanomedicine is reviewed from their use as original imaging agents and/or drug carriers to multifunctional theranostic systems. Finally, the challenges and prospects of the next-generation of CD-based theranostics for clinical applications are also discussed.

Self-assembling of graphene oxide on carbon quantum dot loaded liposomes

This paper describes the design of stimuli-sensitive theranostic nanoparticles, composed of reduced graphene oxide (rGO) self-assembled on thermosensitive liposomes encapsulated doxorubicin (DOX) and carbon quantum dot (CQD) (CQD-DOX-rGO-Tlip). The rGO-Tlip particles have been observed to be flower-shaped objects. The thermoresponsive and theranostic potential of CQD-DOX-rGO-Tlips have been studied using differential scanning calorimetry (DSC), ultraviolet visible spectroscopy (UV-Vis), Raman spectroscopy and photoluminescent assays. The chemo-photothermal potential of rGO-Tlip on MD-MB-231 cells during NIR laser irradiation has been examined using MTT assay. Also, the ability of rGO-Tlip to be taken up by MD-MB-231 cells has been studied using confocal microscopy and flowcytometry. The results indicate that CQD-DOX-rGO-Tlips achieve a synergistic effect between photothermal therapy and chemotherapy for cancer treatment. Furthermore, online monitoring drug release is accomplished by studying the emission intensity of CQD while DOX released.

Carbon quantum dots doped with phosphorus and nitrogen are a viable fluorescent nanoprobe for determination and cellular imaging of vitamin B12 and cobalt(II)

Phosphorus and nitrogen dually-doped carbon quantum dots (PN-CQDs) were prepared from sucrose, 85% phosphoric acid and 1,2-ethylenediamine as the sources for carbon, phosphorus and nitrogen, respectively. The PN-CQDs possess good water solubility and favorable biocompatibility. The excitation/emission peaks are at 365/451 nm, but bright blue, green, or red emissions are found depending on whether the excitation wavelengths of the laser are set to 408 nm, 488 nm, or 543 nm, respectively. Fluorescence is quenched by both vitamin B₁₂ (VB₁₂) and Co(II) by a combination of inner filter effect and static quenching. The PN-CQDs are shown to be useful nanoprobes for determination of VB₁₂ and Co(II). Response to VB₁₂ is linear in the range of 2.0-31 μM. The response to Co(II) is linear in two ranges, viz. from 1.7-12 μM and from 28 to 141 μM. The limit of detection of VB₁₂ and Co(II) are 3.0 nM and 29.4 nM, respectively. The nanoprobe was successfully applied to the analyses of VB₁₂ in drug samples and of Co(II) in spiked water samples, and it gave satisfactory results. The nanoprobe was also applied to the determination of VB₁₂ and Co(II) in human hepatocarcinoma cells (type SMMC7721), human pulmonary epithelial cells (type BEAS-2B), human adenocarcinoma cells (type A549), and human pheochromocytoma cells (type PC12), respectively. Graphical abstract Schematic presentation of the quenching of the fluorescence of phosphorus and nitrogen dually-doped carbon quantum dots (PN-CQDs) by vitamin B₁₂ (VB₁₂) and Co(II).

Pheophytin Derived Near-Infrared-Light Responsive Carbon Dot Assembly as a New Phototheranotic Agent for Bioimaging and Photodynamic Therapy

Carbon dots (CDs), a kind of phototheranostic agent with the capability of simultaneous bioimaging and phototherapy [i.e., photodynamic therapy (PDT) or photothermal therapy (PTT)], have received considerable attention because of their remarkable properties, including flexibility for surface modification, high biocompatibility, low toxicity and photo-induced activity for malignant tumor cells. Among numerous carbon sources, it has been found that natural biomass are good candidates for the preparation of CD phototheranostic agents. In this study, pheophytin, a type of Mg-free chlorophyll derivative and also a natural product with low toxicity, was used as a raw carbon source for the synthesis of CDs by using a microwave method. The obtained hydrophobic CDs exhibited a maximum near-infrared (NIR) emission peak at approximately 680 nm, and high singlet oxygen (¹ O₂ ) generation with a quantum yield of 0.62. The self-assembled CDs from the as-prepared CDs with DSPE-mPEG2000 retained efficient ¹ O₂ generation. The obtained carbon dot assembly was not only an efficient fluorescence (FL) imaging agent but also a smart PDT agent. Our studies indicated that the obtained hydrophilic CD assembly holds great potential as a new phototheranostic agent for cancer therapy. This work provides a new route for synthesis of CDs and proposes a readily available candidate for tumor treatment.

A label-free nano-probe for sequential and quantitative determination of Cr(VI) and ascorbic acid in real samples based on S and N dual-doped carbon dots

A fluorescent sulfur and nitrogen dual-doped carbon dots (S,N-CDs) was prepared by a simple and one-step acid-base neutralization and exothermic carbonization method. Hexavalent chromium (Cr(VI)) could effectively quench the fluorescence of S,N-CDs based on inner filter effect (IFE) and dynamic quenching, whereas ascorbic acid (AA) could recover the fluorescence of S,N-CDs/Cr(VI) because of IFE weakening. So an "on-off-on" and label-free nano-probe consecutive determination of Cr(VI) and AA was constructed. This nano-probe system demonstrated excellent selectivity and sensitivity to Cr(VI) and AA with linear range of 0.065-198 μmol/L (3.38-10,296 μg/L) and 6.6-892 μmol/L (1.16-157 mg/L), respectively. Meanwhile, the as-prepared S,N-CDs possess low toxicity and could be used for multi-color cell imaging in SMMC 7721 cells. More importantly, this nano-probe was successfully employed for detection of Cr(VI) in tap water and AA in food samples. In view of its simple detection condition, rapid response, wide linear range, low detection limit and inexpensive instrument, the as-constructed nano-probe system could have a wide range of potential application, including water quality monitoring and evaluation, food inspection and testing and biomedical analysis.

Biconcave Carbon Nanodisks for Enhanced Drug Accumulation and Chemo-Photothermal Tumor Therapy

It is considered a significant challenge to construct nanocarriers that have high drug loading capacity and can overcome physiological barriers to deliver efficacious amounts of drugs to solid tumors. Here, the development of a safe, biconcave carbon nanodisk to address this challenge for treating breast cancer is reported. The nanodisk demonstrates fluorescent imaging capability, an exceedingly high loading capacity (947.8 mg g-1 , 94.78 wt%) for doxorubicin (DOX), and pH-responsive drug release. It exhibits a higher uptake rate by tumor cells and greater accumulation in tumors in a mouse model than its carbon nanosphere counterpart. In addition, the nanodisk absorbs and transforms near-infrared (NIR) light to heat, which enables simultaneous NIR-responsive drug release for chemotherapy and generation of thermal energy for tumor cell destruction. Notably, this NIR-activated dual therapy demonstrates a near complete suppression of tumor growth in a mouse model of triple-negative breast cancer when DOX-loaded nanodisks are administered systemically.

Biomolecule-derived quantum dots for sustainable optoelectronics

The diverse chemical functionalities and wide availability of biomolecules make them essential and cost-effective resources for the fabrication of zero-dimensional quantum dots (QDs, also known as bio-dots) with extraordinary properties, such as high photoluminescence quantum yield, tunable emission, photo and chemical stability, excellent aqueous solubility, scalability, and biocompatibility. The additional advantages of scalability, tunable optical features and presence of heteroatoms make them suitable alternatives to conventional metal-based semiconductor QDs in the field of bioimaging, biosensing, drug delivery, solar cells, photocatalysis, and light-emitting devices. Furthermore, a recent focus of the scientific community has been on QD-based sustainable optoelectronics due to the primary concern of partially mitigating the current energy demand without affecting the environment. Hence, it is noteworthy to focus on the sustainable optoelectronic applications of biomolecule-derived QDs, which have tunable optical features, biocompatibility and the scope of scalability. This review addresses the recent advances in the synthesis, properties, and optoelectronic applications of biomolecule-derived QDs (especially, carbon- and graphene-based QDs (C-QDs and G-QDs, respectively)) and discloses their merits and disadvantages, challenges and future prospects in the field of sustainable optoelectronics. In brief, the current review focuses on two major issues: (i) the advantages of two families of carbon nanomaterials (i.e. C-QDs and G-QDs) derived from biomolecules of various categories, for instance (a) plant extracts including fruits, flowers, leaves, seeds, peels, and vegetables; (b) simple sugars and polysaccharides; (c) different amino acids and proteins; (d) nucleic acids, bacteria and fungi; and (e) biomasses and their waste and (ii) their applications as light-emitting diodes (LEDs), display systems, solar cells, photocatalysts and photo detectors. This review will not only bring a new paradigm towards the construction of advanced, sustainable and environment-friendly optoelectronic devices using natural resources and waste, but also provides critical insights to inspire researchers ranging from material chemists and chemical engineers to biotechnologists to search for exciting developments of this field and consequently make an advance step towards future bio-optoelectronics.

The advanced role of carbon quantum dots in nanomedical applications

Carbon quantum dots (CQDs) have emerged as a potential material in the diverse fields of biomedical applications due to their numerous advantageous properties including fluorescence, water solubility, biocompatibility, low toxicity, small size and ease of modification, inexpensive scale-up production, and versatile conjugation with other nanoparticles. Thus, CQDs became a preferable choice in various biomedical applications such as nanocarriers for drugs, therapeutic genes, photosensitizers, and antibacterial molecules. Further, their potentials have also been verified in multifunctional diagnostic platforms, cellular and bacterial bio-imaging, development of theranostics nanomedicine, etc. This review provides a concise insight into the progress and evolution in the field of CQD research with respect to methods/materials available in bio-imaging, theranostics, cancer/gene therapy, diagnostics, etc. Further, our discussion is extended to explore the role of CQDs in nanomedicine which is considered to be the future of biomedicine. This study will thus help biomedical researchers in tapping the potential of CQDs to overcome various existing technological challenges.

High drug-loading system of hollow carbon dots-doxorubicin: preparation, in vitro release and pH-targeted research

Hollow carbon dots (HCDs), as drug carriers, and doxorubicin (DOX), as a model drug, were selected to prepare a HCDs-DOX-loading system. First, HCDs were prepared by a hydrothermal method and characterized by transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and nuclear magnetic resonance (¹³C NMR), UV-vis absorption, Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopies (XPS). The HCDs were then used to load DOX. The drug-loading system of HCDs-DOX was characterized by zeta potential measurements, and UV-vis absorption and fluorescence spectroscopies. We then studied the drug loading, formation mechanism, cytotoxicity, in vitro release and pH-targeted properties. HCDs-DOX was found to have a high drug (DOX)-loading ratio (∼42.9%) and better sustained pH targeted-release and lower cytotoxicity than those of DOX. In the HCDs-DOX system, interactions between the HCDs and DOX were electrostatic resulting in the formation of -N[double bond, length as m-dash]C-via the coupling of -NH₂ (on HCDs) and -C[double bond, length as m-dash]O (on DOX). In vitro release of HCDs-DOX conformed to the Weibull model and Fick diffusion, consistent with that of free DOX. We report, for the first time, that the: (i) functional groups on the HCD surfaces (not their hollow structure) play a key role in drug loading; (ii) the carrier (HCDs) did not change the in vitro release model or mechanism of DOX before and after loading by the HCDs.

Selective Labeling and Growth Inhibition of Pseudomonas aeruginosa by Aminoguanidine Carbon Dots

Pseudomonas aeruginosa is a highly virulent bacterium, particularly associated with the spread of multidrug resistance. Here we show that carbon dots (C-dots), synthesized from aminoguanidine and citric acid precursors, can selectively stain and inhibit the growth of P. aeruginosa strains. The aminoguanidine-C-dots were shown both to target P. aeruginosa bacterial cells and also to inhibit biofilm formation by the bacteria. Mechanistic analysis points to interactions between aminoguanidine residues on the C-dots' surface and P. aeruginosa lipopolysaccharide moieties as the likely determinants for both antibacterial and labeling activities. Indeed, the application of biomimetic membrane assays reveals that LPS-promoted insertion and bilayer permeation constitute the primary factors in the anti- P. aeruginosa effect of the aminoguanidine-C-dots. The aminoguanidine C-dots are easy to prepare in large quantities and are inexpensive and biocompatible and thus may be employed as a useful vehicle for selective staining and antibacterial activity against P. aeruginosa.

A di-functional and label-free carbon-based chem-nanosensor for real-time monitoring of pH fluctuation and quantitative determining of Curcumin

A nitrogen and sulfur dual-doped carbon nanodots (N,S-CNDs) sample was fabricated by an one-step hydrothermal treatment of acid fuchsin. The obtained N,S-CNDs possess yellow fluorescent, excellent water solubility, high fluorescence stability and religious biocompatibility, which can be used as a di-functional and label-free chem-nanosensor for the determination of pH and curcumin (Cur). When the pH is decreased from 8.0 to 4.4, the N,S-CNDs reveals an extraordinary emission escalation at emission wavelength (λ_em) of 543 nm, and the pK_a value of the N,S-CNDs was calculated as 6.06. The N,S-CNDs displays a favourable linear relationship in the physiological pH range of 5.0-7.4, which is meaningful for the research of near-neutral cytosolic pH. Furthermore, the laser scanning confocal microscopic images of intracellular distribution and the determination of pH in HeLa cells were successfully carried out, implying that the N,S-CNDs possess excellent cell membrane permeability and are capable of being further applied to real-time pH fluctuations monitoring in live cells with negligible autofluorescence. More importantly, the fluorescence of N,S-CNDs may be dramatically quenched by Cur via a combination of electrostatic and hydrogen-bond interaction and fluorescence inner filter effect (FIFE). The limit of detection is as low as 81 nmol/L Cur, and the linearity range is 0.5-20 μmol/L Cur. Ultimately, a satisfactory result was obtained when applying the as-constructed fluorescent chem-nanosensing system for the analyses of Cur in practical samples.

Image-guided cancer therapy using aptamer-functionalized cross-linked magnetic-responsive Fe3O4@carbon nanoparticles

The excellent anticancer effect of combined differential cancer therapies has been observed in the last few decades. Efficient theragnostic nanoparticles (NPs) for malignancy treatment have received considerable research attention and widely investigated today. This study presents our results on the development of aptamer-functionalized Fe₃O₄@carbon@doxorubicin NPs (Apt-Fe₃O₄@C@DOX) and their application in the synergetic chemo-photothermal therapy (PTT) of cancer. The Apt-Fe₃O₄@C@DOX NPs displayed high photothermal conversion efficiency and extensive pH/heat-induced drug release. In vitro (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium) bromide experiments indicated that the combined chemo-PTT is much more toxic toward lung adenocarcinoma cells (A549) than PTT or chemotherapy alone. In addition, the Apt-Fe₃O₄@C@DOX NPs demonstrated decreasing contrast enhancement of magnetic resonance (MR) signals, which means they may be potentially applied as a contrast agent and serve as a critical component of T₂-weighted MR imaging of tumor tissues. Taking the results together, the Apt-Fe₃O₄@C@DOX NPs show great potential for cancer therapy.

Photoluminescence enhancement via microwave irradiation of carbon quantum dots derived from solvothermal synthesis of l-arginine

Photoluminescence enhancement of carbon quantum dots was achieved via solvothermal synthesis followed by microwave irradiation.

Design of dual drug-loaded dendrimer/carbon dot nanohybrids for fluorescence imaging and enhanced chemotherapy of cancer cells

Dual drug-loaded dendrimer/CD nanohybrids can be developed for fluorescence imaging and enhanced chemotherapy of cancer cells.

Co2+ detection, cell imaging, and temperature sensing based on excitation-independent green-fluorescent N-doped carbon dots

Green-fluorescent N-doped carbon dots (N-CDs) have been successfully fabricated using hydrothermal treatment of tyrosine and urea.

Non-Metal-Heteroatom-Doped Carbon Dots: Synthesis and Properties

Carbon dots (CDs) are new materials with applications in bioimaging, optical devices, catalysis, and many other fields. Their advantages, such as ease of large-scale preparation, low-costing precursors, highly tunable photoluminescence, satisfactory biocompatibility, and photostability against photobleaching, make them competitive alternatives to conventional semiconductor-based quantum dots and organic dyes. To overwhelm other luminescent materials in applications, their functionalities still need to be improved in spite of the abovementioned advantages. In recent years, it has been proven that heteroatom doping is an effective approach to improve the optical and electronic performance of CDs by tuning their carbon skeleton matrices and chemical structures. In this review, the development of non-metal-heteroatom-doped CDs, including heteroatom categories, preparation methods, and physicochemical properties, are discussed. Progressive trends in heteroatom-doped CDs are also discussed at the end of this review.

Ultrafast and Energy-saving Synthesis of Nitrogen and Chlorine Co-doped Carbon Nanodots via Neutralization Heat for Selective Detection of Cr(VI) in Aqueous Phase

In this work, it is presented for the first time that nitrogen and chlorine co-doped carbon nanodots (N,Cl-CDs) were synthesized by simply mixing glucose, concentrated hydrochloric acid (HCl), and 1,2-ethylenediamine (EDA). No external heat was employed; the neutralization reaction served as the heat source. The glucose served as the carbon source while EDA and HCl were the N and Cl dopants, respectively. The fluorescence of N,Cl-CDs was adequately quenched by hexavalent chromium Cr(VI) based on a combination of dynamic quenching and inner filter effect (IFE). Accordingly, an efficient N,Cl-CDs-based fluorescence probe was established for sensitive and selective detection of Cr(VI). The proposed fluorescence sensor provides a linear recognition range for Cr(VI) determination from 3 to 40 µM with a limit of detection (LOD) of 0.28 µM (14.6 µg/L). The proposed fluorescence method was successfully utilized to detect Cr(VI) in different water samples with satisfactory results. The spike recoveries vary from 97.01% to 103.89% with relative standard deviations (RSDs) of less than 0.82%. This work highlights the development of a simple, ultrafast, and energy-saving one-step synthetic route to fabricate N,Cl-CDs for highly selective and sensitive detection of Cr(VI) in real water samples. It is anticipated that the proposed fluorescence method could be further explored and widely used for Cr(VI) detection in the environmental industry.

Synthesis of ginsenoside Re-based carbon dots applied for bioimaging and effective inhibition of cancer cells

BACKGROUND

Fluorescent carbon-based nanomaterials have promising properties such as biosensing, cell imaging, tracing and drug delivery. However, carbon dots (CDs) with specific inherent biological functions have not been investigated. Ginsenosides are the components with multiple bioactivities found in plants of the genus Panax, which have attracted a lot of attention for their anticancer effect.

MATERIALS AND METHODS

In this study, we prepared a kind of novel photoluminescent CDs from ginsenoside Re by one-step hydrothermal synthesis method. The conventional methods including transmission electron microscopy, Fourier transform infrared spectroscopy, HPLC and fluorescence spectrum were used for characterization of CDs. In vitro anticancer effect was investigated by cytotoxicity assay, flow cytometry and Western blot analysis.

RESULTS

The as-prepared Re-CDs had an average diameter of 4.6±0.6 nm and excellent luminescent properties. Cellular uptake of Re-CDs was facilitated by their tiny nanosize, with evidence of their bright excitation-dependent fluorescent images. Compared with ginsenoside Re, the Re-CDs showed greater inhibition efficiency of cancer cell proliferation, with lower toxicity to the normal cells. The anticancer activity of Re-CDs was suggested to be associated with the generation of large amount of ROS and the caspase-3 related cell apoptosis.

CONCLUSION

Hopefully, the dual functional Re-CDs, which could both exhibit bioimaging and anticancer effect, are expected to have great potential in future clinical applications.

A label-free and ultrasensitive electrochemical aptasensor for lead(ii) using a N,P dual-doped carbon dot-chitosan composite as a signal-enhancing platform and thionine as a signaling molecule

Herein, a label-free and ultrasensitive electrochemical aptasensor for the determination of lead(ii) (Pb2+) was described. It was based on the application of a N,P dual-doped carbon dot-chitosan (N,P-CD-CS) composite as the signal molecule carrier and an aptamer (APT) as the specific binding probe for Pb2+ that were self-assembled on the surface of a gold electrode (GE). 6-Mercapto-1-hexanol (MCH) was used to block the nonspecific binding sites, and the electro-active molecule thionine (THi) was used as the signaling probe. The differential pulse voltammetry (DPV) response of THi at a rather low working potential of -0.17 V (vs. Ag/AgCl) was used to detect Pb2+. The electrochemical performances of the resulting modified electrode were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Under optimal experimental conditions, the modified electrode exhibited excellent DPV response depending on the concentration of Pb2+ in the 0.01 nM to 10 nM range. The limit of detection was 3.8 pM (at S/N = 3). The modified electrode displayed good reproducibility and excellent stability. It was successfully applied for the determination of Pb2+ in real water samples.

Nitrogen-doped carbon nanodots for bioimaging and delivery of paclitaxel

Carbon nanodots (CNDs) hold great potential in imaging and drug delivery applications. In this study, nitrogen-doped CNDs (NCNDs) were coupled to the anticancer agent paclitaxel (PTX) through a labile ester bond. NCNDs showed excellent cell viability and endowed the NCND-PTX conjugate with good water solubility. The hybrid integrates the optical properties of the nanodots with the anticancer function of the drug into a single unit. Cytotoxicity was evaluated in breast, cervix, lung, and prostate cancer cell lines by the MTT assay while the cellular uptake was monitored using confocal microscopy. NCND-PTX induced apoptosis in cancer cells exhibiting slightly better anticancer activity compared to the drug alone. Moreover, the course of the NCND-PTX interaction with cancer cells was monitored using an xCELLigence system. The NCND-based conjugate represents a promising platform for bioimaging and drug delivery.

Carbon Dots from Sugars and Ascorbic Acid: Role of the Precursors on Morphology, Properties, Toxicity, and Drug Uptake

There is the need for reproducible, simple, high-yielding synthetic protocols aimed at obtaining carbon dots (CDs) with controlled fluorescence, photothermal and photochemical behavior, surface properties, biocompatibility, tumor targeting ability, drug absorption biodistribution, and tumor uptake. This Letter describes a systematic study on the effect of glucose, fructose, and ascorbic acid as starting materials for the preparation of highly luminescent CDs, characterized by a blue emission. Their composition and morphology are investigated by titration of OH surface groups, spectroscopic techniques, and high-resolution transmission electron microscopy (HR-TEM), and their toxicity was tested toward HeLa cells. CDs made using fructose were toxic, while those made from glucose and ascorbic acid showed good biocompatibility. The reproducible and simple synthetic procedure yields luminescent biomass-derived CDs for combined cancer therapy and diagnostics. Their doxorubicin (DOX) drug uptake was measured by spectrofluorimetry, indicating a crucial role of the morphologies of the CDs in controlling DOX loading. The glucose derived CDs showed up to 28% w/w of DOX loading.

Facile Synthesis of Fluorescent Hyper-Cross-Linked β-Cyclodextrin-Carbon Quantum Dot Hybrid Nanosponges for Tumor Theranostic Application with Enhanced Antitumor Efficacy

Fluorescent hyper-cross-linked β-cyclodextrin-carbon quantum dot (β-CD-CQD) hybrid nanosponges of about 200 nm with excellent biocompatibility and strong bright blue fluorescence excited at 365 nm with a high photoluminescence quantum yield (PLQY) of 38.0% were synthesized for tumor theranostic application by facile condensation polymerization of carbon quantum dots (CQDs) with β-cyclodextrin (β-CD) at a feeding ratio of 1:5. The DOX@β-CD-CQD theranostic nanomedicine, around 300 nm with DOX-loading capacity of 39.5% by loading doxorubicin (DOX) via host-guest complexation, showed a pH responsive controlled release and released DOX in the simulated tumor microenvironment in a sustained release mode, owing to the formation constant in the supramolecular complexation of DOX with the β-CD units in the β-CD-CQD nanosponges. The proposed DOX@β-CD-CQD theranostic nanomedicine could be internalized into HepG2 cells, and the released DOX was accumulated into the cell nuclei, demonstrating an antitumor efficacy more enhanced than that of the free drug.

Highly passivated phosphorous and nitrogen co-doped carbon quantum dots and fluorometric assay for detection of copper ions

Carbon quantum dots are becoming powerful fluorophore materials for metal ion analysis. Here, highly passivated green phosphorous and nitrogen co-doped carbon quantum dots (C-dots) were prepared using low-temperature carbonization route. Strong green fluorescence emission around 490 nm and excitation wavelength independent C-dots were obtained. Morphological, surface, and optical properties of the C-dots were characterized. Fluorescence emission of C-dots was quenched selectively by copper ions and restored by adding copper chelators, such as EDTA and sulfide ions. Thus, C-dots were successfully used for direct determination of copper ions. Detection limit as low as 1.5 nM (s/n = 3) was achieved for copper ions. Such a low detection limit is very significant for metal analysis using our proposed facile method and low-cost substrates. Experimental results showed that the prepared C-dots demonstrated high sensitivity and selectivity for Cu²⁺ ion detection and the method is robust and rugged. Graphical abstract ᅟ.

Conversion of Carbon Dots from Fluorescence to Ultralong Room-Temperature Phosphorescence by Heating for Security Applications

Stimuli-responsive optical materials have received tremendous interest in the last several decades due to their numerous promising applications. Here, fluorescence emissive polymer carbon dots (F-CDs), prepared with a simple heating treatment from ethylenediamine and phosphoric acid, are found to produce unexpected ultralong room-temperature phosphorescence (URTP), which lasts for about 10 s with a lifetime of 1.39 s. This is the first example to achieve the conversion of a fluorescence material to URTP by means of an external heating stimulus. Further investigations reveal that the doping of N and P elements and self-immobilization of the excited triplet species are likely mainly responsible for the observed URTP after the heating treatment, due to the facilitation of the intersystem crossing and formation of more compact cores for effective intraparticle hydrogen bonds, respectively. Importantly, this study also demonstrates the potential for aqueous dispersion of the F-CDs as an advanced security ink for information encryption and anticounterfeiting; this is a feature that has not been reported before. This study is believed to open possibilities to extend stimuli-responsive optical materials to rarely exploited phosphorescence-relevant systems and applications, and also to provide a novel strategy to easily prepare URTP materials.

Nitrogen and phosphorus dual-doped carbon dots as a label-free sensor for Curcumin determination in real sample and cellular imaging

A nitrogen and phosphorus dual-doped carbon dots (NP-Cdots) was fastly synthesized with glucose as the carbon source, 1,2-ethylenediamine as N-dopant and concentrated phosphoric acid as P-dopant. The as-synthesized NP-Cdots was utilized as a label-free sensor for determination of Curcumin (Cur). The proposed NP-Cdots-based fluorescence sensor was applied for sensitive detection of Cur in aqueous solution, achieving a linear range of 0.5-20 µmol/L and a detection limit of 58 nmol/L (21.37 ng/mL). The common amino acids and other drugs do not interfere with the detection of Cur, providing good selectivity. The constructed sensor was successfully applied to the determination of Cur in drinking water and the food samples with satisfactory results and the RSDs and recoveries were 0.08-5.39% and 95.2-105.2%, respectively. More importantly, the as-prepared NP-Cdots was used as effective fluorescent agent for cellular imaging without noticeable cytotoxicity. The proposed sensor is simple and practical, illustrating that the potential application of NP-Cdots for biosensing, food monitoring and cellular labeling and imaging.

Magnetofluorescent Carbon Quantum Dot Decorated Multiwalled Carbon Nanotubes for Dual-Modal Targeted Imaging in Chemo-Photothermal Synergistic Therapy

Magnetofluorescent nanoparticles with diagnostic and therapeutic functions show great promise in nanomedicine. Here, we report the magnetofluorescent carbon nanotubes (CNTs)/doxorubicin (DOX) nanocomposites and their functions act in synergetic chemo-photothermal synergistic therapy (Chemo/PTT) in cancer excision. Magnetofluorescent CNTs conjugated with a folic acid (FA-GdN@CQDs-MWCNTs) were targets for dual-modal fluorescence (FL)/magnetic resonance (MR) imaging. Experiments in vitro and in vivo identified FA-GdN@CQDs-MWCNTs with low toxicity, and good biocompatibility. Moreover, FA-GdN@CQDs-MWCNTs whose release can be fostered by pH and NIR light dual-stimuli had been proved to be available for loading DOX. Following nuclear translocations, FA-GdN@CQDs-MWCNTs were engineered to deliver DOX that targeted the nuclei. In vivo experiment indicates that the Chemo/PTT, as compared with the respective single treatment, can significantly control tumor growth. In addition, Chemo/PTT was not shown to render any appreciable toxicity. These findings suggest that the FA-GdN@CQDs-MWCNTs/DOX could function as a multifunctional platform for simultaneous FL/MR imaging, PTT therapy, and drug delivery.

N,S,P Co-Doped Carbon Nanodot Fabricated from Waste Microorganism and Its Application for Label-Free Recognition of Manganese(VII) and l-Ascorbic Acid and AND Logic Gate Operation

A novel fluorescent probe based on N,S,P codoped carbon nanodots (N,S,P-CND_Sac) is very simple and quickly fabricated by a one-step hydrothermal pyrolysis of Saccharomyces cerevisiae and utilized for label-free and "on-off-on" sequential detection of manganese(VII) and l-ascorbic acid (l-AA). The fluorescence of N,S,P-CND_Sac can be effectively quenched by Mn(VII) based on an inner filter effect (IFE) and recovered upon the addition of l-AA due to the easy conversion of Mn(VII) to reduced states (i.e., Mn(IV), Mn(II), and Mn(0)) by l-AA. This probe exhibited favorable selectivity and sensitivity toward Mn(VII) and l-AA with detection limits of 50 nmol/L and 1.2 μmol/L, respectively. Simultaneously, an "AND" logic gate based on the as-fabricated N,S,P-CND_Sac has been constructed. Also, the as-proposed fluorescent probe was extended to detect Mn(VII) and l-AA in biosystems. Furthermore, the as-constructed fluorescent probe system was successfully applied to the analyses of Mn(VII) in tap water, Fenhe River water, and medicinal herb samples with satisfactory results. The proposed method is simple and easily accessible, demonstrating the great potential of N,S,P-CND_Sac in biosensing, disease diagnosis, cellular labeling, and environmental monitoring.

Ultrasmall and photostable nanotheranostic agents based on carbon quantum dots passivated with polyamine-containing organosilane molecules

In this work, we demonstrate that ultrasmall, photostable and multifunctional carbon quantum dots (or carbon dots, CDs) passivated with polyamine-containing organosilane molecules can realize simultaneous cell imaging and anticancer drug delivery. The presence of abundant surface amine groups makes these CDs be able to covalently link with the anticancer drug, doxorubicin (DOX), with an extremely high drug loading capacity (62.8%), while the surface hydroxyl groups ensure the good water-dispersibility of the CDs-DOX. Besides the use as a drug carrier, the fluorescent CDs also enable the dynamic tracing of the drug release process. When the CDs-DOX complexes were internalized by the human breast cancer cells (MCF-7), DOX could gradually detach from the surface of CDs and enter into the cell nucleus, while the CDs themselves still resided in the cytoplasm. In addition, the in vivo experiments showed that the CDs-DOX complexes exhibited a better tumor inhibition performance than free DOX molecules, which may be ascribed to the prolonged drug accumulation in tumor tissues. Furthermore, the as-synthesized CDs also exhibited negligible cytotoxicity/systemic side effects, and could successfully illuminate mammalian, bacterial and fungal cells, making them good candidates as not only drug delivery vehicles but also universal cell imaging reagents. The present work may have implications for the fabrication of functional carbon-based nanomaterials and foster the development of carbon dots as novel nanotheranostics for various biomedical applications.

Nitrogen-doped carbon dots as a fluorescent probe for the highly sensitive detection of Ag+ and cell imaging

An easy hydrothermal synthesis strategy was applied to synthesize green-yellow emitting nitrogen-doped carbon dots (N-CDs) using 1,2-diaminobenzene as the carbon source, and dicyandiamide as the dopant. The nitrogen-doped CDs resulted in improvement in the electronic characteristics and surface chemical activities. N-CDs exhibited bright fluorescence emission and could response to Ag⁺ selectively and sensitively. Other ions produced nearly no interference. A N-CDs based fluorescent probe was then applied to sensitively determine Ag⁺ with a detection limit of 5 × 10^-8  mol/L. The method was applied to the determination of Ag⁺ dissolved in water. Finally, negligibly cytotoxic, excellently biocompatibile, and highly fluorescent carbon dots were applied for HepG2 cell imaging and the quenched fluorescence by adding Ag⁺ , which indicated its potential applications.

Doxorubicin-loaded environmentally friendly carbon dots as a novel drug delivery system for nucleus targeted cancer therapy

Chemotherapy is widely applied against various kinds of carcinoma. Generally, chemotherapeutic agents, such as Doxorubicin (DOX), Paclitaxel (PTX), 5-Fluorouracil (5-FU), Methotrexate (MTX), and Vinblastine (VLB) are combined with a view to maximizing their efficacy. Unfortunately, chemotherapeutics are indiscriminate and also kill normal healthy cells, resulting in serious side effects. This non-productive and destructive distribution of chemotherapeutics is regarded as one of the largest problems associated with chemotherapy. Recently, the application of carbon dots (CDs) in cancer therapy has attracted considerable attention due to their attractive properties, such as biocompatibility and low toxicity. We report herein on the fabrication of CD-DOX antitumor drug complexes, from the combination of CDs and DOX, with a view to providing a novel and efficient strategy for cancer treatment. CDs were synthesized by hydrothermal treatment of milk, a simple and environmentally friendly synthetic process. DOX was conjugated to the CDs through electrostatic interactions via the multiple surface CD functional groups. The CD-DOX complexes exhibited pH-dependent DOX release behavior. A cytotoxicity study demonstrated that the CDs were non-cytotoxic in the range of concentrations used. Compared to free DOX, the CD-DOX complexes were significantly more destructive to the adenoid cystic carcinoma cell line (ACC-2), but exhibited lower toxicity to a mouse fibroblast cell line (L929). Confocal microscopy and flow cytometry confirmed that CD-DOX complexes increased cancer therapy efficiency through the localization of a much higher quantity of drugs in the nuclei of tumor cells and induced a higher rate of apoptosis in ACC-2 cells, compared to DOX alone.