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

An "on-off-on" fluorescent nanoprobe for recognition of chromium(VI) and ascorbic acid based on phosphorus/nitrogen dual-doped carbon quantum dot

Chromium (VI) [Cr(VI)] is a harsh environmental contaminates and has been proved to be highly toxic, carcinogenic and mutagenic. Therefore, developing an inexpensive, good selective and highly sensitive nanoprobe for the detection of Cr(VI) is in urgent demand. Recently, the highly fluorescent carbon quantum dots (CQDs) have been successfully utilized as efficient fluorescent nanoprobes for the detection of ions, pH and molecular substances. In this work, an "on-off" fluorescence phosphorus/nitrogen dual-doped CQDs (PNCQDs) probe was developed for the determination of Cr(VI) based on inner filter effect (IFE). The proposed PNCQDs nanoprobe shows its distinct merits of simplicity, convenience, fast implementation, good selectivity and high sensitivity towards Cr(VI), allowing its potential application in the determination of Cr(VI) in environment and biosystem. In addition, the chelation effect of the functional groups in reductant and Cr(VI), and the easy-conversion of Cr(VI) to reduced states (i.e. Cr(III) and Cr(0)) by reductants makes the minimization of IFE with a concomitant recovery of PNCQDs fluorescence possible. Hence, the PNCQDs/Cr(VI) hybrid was used as an "off-on" fluorescence probe for sensing ascorbic acid (AA), which is a model reductant. For the detection of Cr(VI), the linear range and the limit of detection achieved were 1.5-30 μmol/L and 23 nmol/L, respectively. For the detection of AA, the linear range and the limit of detection obtained were 5.0-200 μmol/L and 1.35 μmol/L, respectively. The as-constructed "on-off-on" PNCQDs fluorescent nanoprobe was successfully applied for detecting Cr(VI) and AA in biosystem. Furthermore, the as-constructed fluorescent sensing system was successfully applied to the analyses of AA in fresh fruits and in commercial fruit juices with satisfactory results.

Bacteria-derived fluorescent carbon dots for microbial live/dead differentiation

Microbial viability assessment plays a key role in many areas such as pathogen detection, infectious disease treatment and antimicrobial drug development. Many conventional viability dyes (such as propidium iodide, PI) used for differentiating live/dead microbes suffer from notable cytotoxicity, poor photostability and are of high cost. Thus their applications for accurate microbial viability determination are limited. Herein, for the first time we report the successful synthesis of fluorescent carbon dots (CDs) from bacteria via one-step hydrothermal carbonization. Benefiting from their highly negative surface charge (the zeta potential is as high as around -42 mV) and suitable size, the CDs can selectively stain dead microbial cells (bacteria and fungi) but not live ones. Importantly, compared to the widely used commercial dye PI, the developed CDs possess many great advantages including low cytotoxicity, multicolor imaging ability, excellent photostability and high selectivity. Moreover, because the synthetic method is simple, inexpensive and eco-friendly, this type of CD is suitable for large-scale production, making it an excellent candidate for microbial live/dead differentiation and viability assessment. The present work explores the feasibility of using bacteria to fabricate novel CDs and broadens the applications of CDs for biomedical applications.

N-Doped CDs–GP nanospheres as a drug delivery nanocarrier system with carbon dots and a fluorescent tracer

In this study, a carbon dots-genipin covalent conjugate (CDs–GP) was synthesized, characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and fluorescence spectroscopy (FL).

Development of N and S heteroatom co-doped stable dual emitting carbon ink in aqueous media for sensing applications

This manuscript describes a simple chemical route to synthesize nitrogen and sulfur co-doped highly fluorescent carbon nanomaterials with dual emission fluorescence properties. The fluorescence intensity of the (N,S)-CNPs has been found to be highly responsive towards Hg²⁺ ions and the pH of the solution.

Photoluminescent carbon dots derived from sugarcane molasses: synthesis, properties, and applications

Photoluminescent carbon dots derived from sugarcane molasses were investigatedviacellular imaging and sensing for Fe³⁺or sunset yellow. The underlying mechanism of fluorescence quenching in the C-dots/sunset yellow system was also studied.

Graphene oxide and adenosine triphosphate as a source for functionalized carbon dots with applications in pH-triggered drug delivery and cell imaging

A folate-functionalized carbon dot-based nanocarrier system has been successfully synthesized for cancer cell targeted drug delivery.

Hollow carbon nanospheres for targeted delivery of chemotherapeutics in breast cancer therapy

Functional hollow carbon nanospheres were prepared and antibody modified, which improved the targeted delivery of anti-tumor drug.

Uptake dynamics of graphene quantum dots into primary human blood cells following in vitro exposure

Human leukocytes obtained from samples of leukapheresis products of three healthy donors stimulated by granulocyte colony stimulating factor (G-CSF) were exposed to graphene quantum dots.

Folic acid-conjugated carbon dots as green fluorescent probes based on cellular targeting imaging for recognizing cancer cells

Green fluorescent CDs using the natural product dandelion as a carbon source were covalently conjugated with folate to differentiate cancer cells from normal cells.

pH-Sensitive N-doped carbon dots–heparin and doxorubicin drug delivery system: preparation and anticancer research

In this study, doxorubicin (DOX) hydrochloride as a model drug, N-doped carbon dots as a drug carrier, and heparin as an auxiliary medicine were selected to design and prepare a multi-functional drug delivery system with pH-triggered drug release.

Carbon Dot-Based Platform for Simultaneous Bacterial Distinguishment and Antibacterial Applications

In this work, we prepared quaternized carbon dots (CDs) with simultaneous antibacterial and bacterial differentiation capabilities using a simple carboxyl-amine reaction between lauryl betaine and amine-functionalized CDs. The obtained quaternized CDs have several fascinating properties/abilities: (1) A long fluorescence emission wavelength ensures the exceptional bacterial imaging capability, including the super-resolution imaging ability; (2) the polarity-sensitive fluorescence emission property leads to significantly enhanced fluorescence when the quaternized CDs interact with bacteria; (3) the presence of both hydrophobic hydrocarbon chains and positively charged quaternary ammonium groups makes the CDs selectively attach to Gram-positive bacteria, realizing the bacterial differentiation; (4) excellent antimicrobial activity is seen against Gram-positive bacteria with a minimum inhibitory concentration of 8 μg/mL for Staphylococcus aureus. Besides, the quaternized CDs are highly stable in various aqueous solutions and exhibit negligible cytotoxicity, suggesting that they hold great promise for clinical applications. Compared to the traditional Gram staining method, the selective Gram-positive bacterial imaging achieved by the quaternized CDs provides a much simpler and faster method for bacterial differentiation. In summary, by combining selective Gram-positive bacterial recognition, super-resolution imaging, and exceptional antibacterial activity into a single system, the quaternized CDs represent a novel kind of metal-free nanoparticle-based antibiotics for antibacterial application and a new type of reagent for efficient bacterial differentiation.

Synthesis of Dispersible Mesoporous Nitrogen-Doped Hollow Carbon Nanoplates with Uniform Hexagonal Morphologies for Supercapacitors

In this study, dispersible mesoporous nitrogen-doped hollow carbon nanoplates have been synthesized as a new anisotropic carbon nanostructure using gibbsite nanoplates as templates. The gibbsite-silica core-shell nanoplates were first prepared before the gibbsite core was etched away. Dopamine as carbon precursor was self-polymerized on the hollow silica nanoplates surface assisted by sonification, which not only favors a homogeneous polymer coating on the nanoplates but also prevents their aggregation during the polymerization. Individual silica-polydopamine core-shell nanoplates were immobilized in a silica gel in an insulated state via a silica nanocasting technique. After pyrolysis in a nanoconfine environment and elimination of silica, discrete and dispersible hollow carbon nanoplates are obtained. The resulted hollow carbon nanoplates bear uniform hexagonal morphology with specific surface area of 460 m²·g^-1 and fairly accessible small mesopores (∼3.8 nm). They show excellent colloidal stability in aqueous media and are applied as electrode materials for symmetric supercapacitors. When using polyvinylimidazolium-based nanoparticles as a binder in electrodes, the hollow carbon nanoplates present superior performance in parallel to polyvinylidene fluoride (PVDF) binder.