Multifunctional carbon dots with near-infrared absorption and emission for targeted delivery of anticancer drugs, tumor tissue imaging and chemo/photothermal synergistic therapy.

Cancer therapy faces considerable challenges related to improving treatment efficiency and overcoming damage to healthy cells. To address these concerns, a strategy for tumor microenvironment-induced cancer imaging/drug release and synergistic chemo-photothermal therapy (chemo/PTT) is proposed in this study. Carbon dots with near-infrared (NIR) absorption and emission, referred to as RCDs, were first prepared and covalently coupled with a Pt(iv) prodrug to form a complex, referred to as RCD-Pt(iv). The surface of the prepared complex was then coated with the polyethylene glycol-chitosan-2,3-dimethylmaleic anhydride polymer (PEG-CS-DA) to obtain a tumor-targeted multifunctional nanoprobe (RCD-Pt(iv)/PEG-CS-DA). When the nanoprobe RCD-Pt(iv)/PEG-CS-DA entered the tumor cells, the acidic environment of the tumor cells allowed rapid PEG-CS-DA hydrolysis and RCD-Pt(iv) release. High levels of glutathione (GSH) in cancer cells reduced Pt(iv) to Pt(ii) and released the RCDs, resulting in cancer tissue imaging and targeted Pt(ii) release. Meanwhile, Pt(ii) collected in the tumor tissues could realize targeted chemotherapy, and the RCDs in the tumor tissues absorbed light energy under NIR light irradiation to produce a large amount of heat to quickly eliminate cancer cells. Thus, cancer tissue imaging/targeted drug release and synergistic chemo/PTT were achieved simultaneously.

Leek-derived codoped carbon dots as efficient fluorescent probes for dichlorvos sensitive detection and cell multicolor imaging.

A biomass nitrogen and sulfur codoped carbon dots (NS-Cdots) was prepared by a simple and clean hydrothermal method using leek, and was employed as efficient fluorescent probes for sensitive detection of organophosphorus pesticides (OPs). The leek-derived NS-Cdots emitted blue fluorescence, but was quenched by H2O2. Due to acetylcholinesterase/choline oxidase-based cascade enzymatic reaction that produces H2O2 and the inhibition effect of OPs on acetylcholinesterase activity, a NS-Cdots-based fluorescence "off-on" method to detect OPs-dichlorvos (DDVP) was developed. More sensitivity and wider linear detection range were achieved from 1.0 × 10-9 to 1.0 × 10-3 M (limit of detection = 5.0 × 10-10 M). This developed method was applied to the detection of DDVP in Chinese cabbage successfully. The average recoveries were in the range of 96.0~104.0% with a relative standard deviation of less than 3.3%. In addition, the NS-Cdots fluorescent probes were also employed successfully in multicolor imaging of living cells, manifesting that the NS-Cdots fluorescent probes have great application potential in agricultural and biomedical fields. Graphical Abstract.

P,N Codoped carbon dots as an efficient "off-on" fluorescent probe for lipoic acid detection and its cellular dual-color imaging.

A facile single hydrothermal method was developed to synthetize P,N codoped carbon dots (P,N/CDs), which show strong and stable fluorescence, good water solubility, low toxicity and good biocompatibility. Hence, a novel and efficient "off-on" P,N/CDs fluorescent probe was developed for the highly sensitive detection of lipoic acid (LA) for the first time. The fluorescence of the P,N/CDs was quenched by Cu2+ forming a P,N/CDs-Cu2+ complex, which acted as the "off" process, but Cu2+ could be removed by LA, due to stronger chelating between LA and Cu2+, forming a more stable complex, which recovered the fluorescence of the P,N/CDs, in order to achieve the "on" process. Under optimal conditions, the concentration of LA and the increased fluorescence intensity of the P,N/CDs-Cu2+ complex displayed a good linear relationship within the range of 0.05-28 µM, with a detection limit (S/N = 3) of 0.02 µM. The established "off-on" fluorescent probe was successfully applied to the analysis of LA in urine samples. The average recoveries were in the range of 98.3-101.5%, with a relative standard deviations of less than 3.1%. In addition, the P,N/CDs were also successfully applied to cellular dual-color imaging of live T24 cells. The results show that the P,N/CDs have great application potential in clinical diagnosis, bioassay and bioimaging. Graphical abstract.

Photoluminescence light-up detection of zinc ion and imaging in living cells based on the aggregation induced emission enhancement of glutathione-capped copper nanoclusters.

In this work, we prepared glutathione (GSH)-capped copper nanoclusters (Cu NCs) with red emission by simply adjusting the pH of GSH/Cu2+ mixture at room temperature. A photoluminescence light-up method for detecting Zn2+ was then developed based on the aggregation induced emission enhancement of GSH-capped Cu NCs. Zn2+ could trigger the aggregation of Cu NCs, inducing the enhancement of luminescence and the increase of absolute quantum yield from 1.3% to 6.2%. GSH-capped Cu NCs and the formed aggregates were characterized, and the possible mechanism was also discussed. The prepared GSH-capped Cu NCs exhibited a fast response towards Zn2+ and a wider detection range from 4.68 to 2240µM. The detection limit (1.17µM) is much lower than that of the World Health Organization permitted in drinking water. Furthermore, taking advantages of the low cytotoxicity, large Stokes shift, red emission and light-up detection mode, we explored the use of the prepared GSH-capped Cu NCs in the imaging of Zn2+ in living cells. The developed luminescence light-up nanoprobe may hold the potentials for Zn2+-related drinking water safety and biological applications.

Simultaneous determination of phenylurea herbicides in yam by capillary electrophoresis with electrochemiluminescence detection.

A method of capillary electrophoresis (CE) coupled with electrochemiluminescence (ECL) detection has been applied to detect three major phenylurea herbicides (monuron, monolinuron and diuron) simultaneously. The effects of yam sample preparation, injection voltage and time, detection potential, detection buffer concentration and pH, Ru(bpy)3(2+) concentration, separation buffer type, separation buffer pH and concentration, separation voltage were investigated in detail. Under optimum conditions, a good baseline separation and highly sensitive detection for monuron, monolinuron and diuron were achieved. The ECL intensity (I) was in proportion to three analytes concentration (ρ) in the range of 0.1-10,000 µg/L for monuron (r≥0.9993), 0.1-18,000 µg/L for monolinuron (r≥0.9995) and 0.1-20,000 µg/L for diuron (r≥0.9997). The detection limits for monuron, monolinuron and diuron were 0.05, 0.04 and 0.01 µg/L (S/N=3), respectively. The developed method was successfully applied for the analysis of monuron, monolinuron and diuron residues in yam simultaneously. The average recoveries are in the ranges of 90.0-99.2% with relative standard deviations less than 3.2%. The limits of detection of the proposed method were 0.010 µg/kg for monuron, 0.008 µg/kg for monolinuron and diuron in yam.

Determination of 5-hydroxytryptamine in serum by electrochemiluminescence detection with the aid of capillary electrophoresis.

A rapid, sensitive and simple electrochemiluminescence method for the determination of 5-hydroxytryptamine (5-HT) using capillary electrophoresis was proposed. The experimental parameters, including the detection potential, the concentration of Ru(bpy)(3)(2+), the concentration and pH of phosphate buffer for separation and detection, the injection voltage and time and the separation voltage on the determination of 5-HT, were optimized. Under the optimized conditions, the linear concentration range for 5-HT was 3.5 × 10(-9) -5.1 × 10(-3) mol/L, with a detection limit of 5 × 10(-10) mol/L. The relative standard deviations (RSDs) of the ECL intensity and the migration times for six continuous injections of 1.0 µmol/L 5-HT were 2.48% and 1.3%, respectively. The method was successfully applied to 5-HT assay in samples of human serum in 5 min and the extraction recoveries with spiked serum samples were over 94.4%.