Dai-Wen Pang

Electrochemical tuning of luminescent carbon nanodots: from preparation to luminescence mechanism.

The size of C-nanodots can be electrochemically tuned by changing the applied potential during their preparation. The higher the applied potential, the smaller the resulting C-nanodots. Moreover, the surface oxidation degree of the C-nanodots can also be electrochemically tuned. The red-shift of emission independent of the size provides an insight into the luminescence mechanism of C-nanodots.

Photoluminescence-Tunable Carbon Nanodots: Surface-State Energy-Gap Tuning

The photoluminescence of carbon nanodots (C-dots) can be tuned by changing their surface chemistry or size because the photoluminescence is a function of the surface-state electronic transitions. Increasing the degree of surface oxidation leads to a narrowing of the energy gap of the surface; meanwhile, larger C-dots with an extensive π-electron system, which can couple with surface electronic states, can also lead to a narrowing of the energy gap of the surface states.

Ultrasmall Near-Infrared Ag2Se Quantum Dots with Tunable Fluorescence for in Vivo Imaging

A strategy is presented that involes coupling Na(2)SeO(3) reduction with the binding of silver ions and alanine in a quasi-biosystem to obtain ultrasmall, near-infrared Ag(2)Se quantum dots (QDs) with tunable fluorescence at 90 °C in aqueous solution. This strategy avoids high temperatures, high pressures, and organic solvents so that water-dispersible sub-3 nm Ag(2)Se QDs can be directly obtained. The photoluminescence of the Ag(2)Se QDs was size-dependent over a wavelength range from 700 to 820 nm, corresponding to sizes from 1.5 ± 0.4 to 2.4 ± 0.5 nm, with good monodispersity. The Ag(2)Se QDs are less cytotoxic than other nanomaterials used for similar applications. Furthermore, the NIR fluorescence of the Ag(2)Se QDs could penetrate through the abdominal cavity of a living nude mouse and could be detected on its back side, demonstrating the potential applications of these less toxic NIR Ag(2)Se QDs in bioimaging.

Functionalized CdSe quantum dots as selective silver ion chemodosimeter

CdSe quantum dots (QDs) have been prepared and modified with mercaptoacetic acid. They are water-soluble and biocompatible. To improve their fluorescence intensity and stability in water solution, bovine serum albumin (BSA) was absorbed onto their surface. Based on the quench of fluorescence signals of the functionalized CdSe QDs in the 543 nm wavelength and enhancement of them in the 570-700 nm wavelength range by Ag(I) ions at pH 5.0, a simple, rapid and specific method for Ag(I) determination was proposed. In comparison with single organic fluorophores, these nanoparticles are brighter, more stable against photobleaching, and do not suffer from blinking. Under the optimum conditions, the response is linearly proportional to the concentration of Ag(I) between 4.0 x 10(-7) and 1.5 x 10(-5) mol L(-1), and the limit of detection is 7.0 x 10(-8) mol L(-1). The mechanism of reaction is also discussed.

Fluorescent-magnetic-biotargeting multifunctional nanobioprobes for detecting and isolating multiple types of tumor cells.

Fluorescent-magnetic-biotargeting multifunctional nanobioprobes (FMBMNs) have attracted great attention in recent years due to their increasing, important applications in biomedical research, clinical diagnosis, and biomedicine. We have previously developed such nanobioprobes for the detection and isolation of a single kind of tumor cells. Detection and isolation of multiple tumor markers or tumor cells from complex samples sensitively and with high efficiency is critical for the early diagnosis of tumors, especially malignant tumors or cancers, which will improve clinical diagnosis outcomes and help to select effective treatment approaches. Here, we expanded the application of the monoclonal antibody (mAb)-coupled FMBMNs for multiplexed assays. Multiple types of cancer cells, such as leukemia cells and prostate cancer cells, were detected and collected from mixed samples within 25 min by using a magnet and an ordinary fluorescence microscope. The capture efficiencies of mAb-coupled FMBMNs for the above-mentioned two types of cells were 96% and 97%, respectively. Furthermore, by using the mAb-coupled FMBMNs, specific and sensitive detection and rapid separation of a small number of spiked leukemia cells and prostate cancer cells in a large population of cultured normal cells (about 0.01% were tumor cells) were achieved simply and inexpensively without any sample pretreatment before cell analysis. Therefore, mAb-coupled multicolor FMBMNs may be used for very sensitive detection and rapid isolation of multiple cancer cells in biomedical research and medical diagnostics.

Quantum dots-based immunofluorescence technology for the quantitative determination of HER2 expression in breast cancer

HER2 detection is important for breast cancer (BC) treatment and prognosis, but the detection methods currently used have some disadvantages. Quantum dots (QDs)-based probes provide a potentially important new method for HER2 detection in clinical practice. This potential is examined in this paper. A QDs HER2 probe kit and QDs image acquisition and analysis software were developed and applied to 94 clinical samples of BC. Compared to conventional immunohistochemistry techniques, this method provided a superior accurate and sensitive method for the detection of HER2 in clinical breast cancer diagnosis.

The biocompatibility of quantum dot probes used for the targeted imaging of hepatocellular carcinoma metastasis

Semiconductor quantum dots (QDs) have several photo-physical advantages over organic dyes making them good markers in biomedical application. We used CdSe/ZnS QDs with maximum emission wavelength of 590nm (QD590) linked to alpha-fetoprotein (AFP) monoclonal antibody (Ab) to detect AFP in cytoplasm of human hepatocellular carcinoma (HCC) cell line HCCLM6. For the in vivo studies, we used QD-AFP-Ab probes for targeted imaging of human HCC xenograft growing in nude mice by injecting them into the tail vein. In addition, the cytotoxicity in vitro, the acute toxicity in vivo, the hemodynamics and tissue distribution of these probes were also investigated. The results in vitro and in vivo indicate that our QD-based probes have good stability, specificity and biocompatibility for ultrasensitive fluorescence imaging of molecular targets in our liver cancer model system.

Modification of glassy carbon and gold electrodes with DNA

The modification of glassy carbon and gold electrodes with DNA by adsorption or covalent immobilization in a mono- or submonolayer has been investigated using the couple Co(bpy)3+2+3 as an indicator. It has been found that when the solution containing double stranded or single stranded DNA is evaporated to dryness, dehydrated DNA molecules can be irreversibly adsorbed on the surfaces of glassy carbon electrodes, in an amount close to that of the saturated adsorptive monolayer. The DNA-adsorbed layer on glassy carbon electrodes is unstable to bases, but stable to 1 M HCl solution. The adsorption of DNA on the electrodes can be evaluated from the increase in the peak current, the decrease in the value of ΔEp, and the negative shift in the value of Eo′ for the Co(bpy)3+2+3 couple. DNA is very strongly adsorbed on the oxidized surfaces of glassy carbon electrodes, and the adsorptive layer is very stable towards heating. The covalent immobilization of DNA directly onto the electrode surfaces is impossible due to considerable steric hindrance; but if the active groups (sites) on the electrode surfaces are elongated with other suitable molecules, the covalent immobilization of DNA becomes possible on the electrode surfaces. The quantity of covalently immobilized DNA at the electrodes reported in the paper is about 31% of the saturated monolayer.

Shifting and non-shifting fluorescence emitted by carbon nanodots

The shifting and non-shifting fluorescence at varied excitations are observed on carbon nanodots prepared by electro-oxidizing carbon paste electrodes with different compositions. The emissions are proposed to be mainly attributed to the surface states rising from surface oxidation of carbon nanodots.

Near-Infrared Electrogenerated Chemiluminescence of Ultrasmall Ag2Se Quantum Dots for the Detection of Dopamine

The near-infrared (NIR) electrogenerated chemiluminescence (ECL) of water-dispersed Ag(2)Se quantum dots (QDs) with ultrasmall size was presented for the first time. The Ag(2)Se QDs have shown a strong and efficient cathodic ECL signal with K(2)S(2)O(8) as coreactant on the glassy carbon electrode (GCE) in aqueous solution. The ECL spectrum exhibited a peak at 695 nm, consistent with the peak in photoluminescence (PL) spectrum of the Ag(2)Se QDs solution, indicating that the Ag(2)Se QDs had no deep surface traps. Dopamine was chosen as a model analyte to study the potential of Ag(2)Se QDs in the ECL analytical application. The ECL signal of Ag(2)Se QDs can also be used for the detection of the dopamine concentration in the practical drug (dopamine hydrochloride injection) containing several adjuvants such as edetate disodium, sodium bisulfite, sodium chloride and so on. The Ag(2)Se QDs could be a promising candidate emitter of ECL biosensors in the future due to their fantastic features, such as ultrasmall size, low toxicity, good water solubility, and near infrared (NIR) fluorescent emission.