Daixin Ye

An electrochemical sensor for simultaneous determination of ascorbic acid, dopamine, uric acid and tryptophan based on MWNTs bridged mesocellular graphene foam nanocomposite

A multi-walled carbon nanotubes (MWNTs) bridged mesocellular graphene foam (MGF) nanocomposite (MWNTs/MGF) modified glassy carbon electrode was fabricated and successfully used for simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (TRP). Comparing with pure MGF, MWNTs or MWNTs/GS (graphene sheets), MWNTs/MGF displayed higher catalytic activity and selectivity toward the oxidation of AA, DA, UA and TRP. Under the optimal conditions, MWCNs/MGF/GCE can simultaneously detect AA, DA, UA and TRP with high selectivity and sensitivity. The detection limits were 18.28 µmol L(-1), 0.06 µmol L(-1), 0.93 µmol L(-1) and 0.87 µmol L(-1), respectively. Moreover, the modified electrode exhibited excellent stability and reproducibility.

A novel nonenzymatic sensor based on CuO nanoneedle/graphene/carbon nanofiber modified electrode for probing glucose in saliva

Here, we report on a novel nonenzymatic amperometric glucose sensor based on CuO nanoneedle/graphene/carbon nanofiber modified electrode. The results of the scanning electron microscopy indicate that electronic network was formed through their direct binding with the graphene/carbon nanofiber, which leads to larger active surface areas and faster electron transfer for the glucose sensor. High electrocatalytic activity toward the oxidation of glucose was observed with a rapid response (<2 s), a low detection limit (0.1 µM), a wide and useful linear range (1-5.3 mM) as well as good stability and repeatability. Moreover, the common interfering species, such as ascorbic acid, uric acid, dopamine and so forth did not cause obvious interference. The sensor can also be used for quantification of glucose concentration in real saliva samples. Therefore, this work has demonstrated a simple and effective sensing platform for nonenzymatic detection of glucose.

Protein-inorganic hybrid nanoflowers as ultrasensitive electrochemical cytosensing Interfaces for evaluation of cell surface sialic acid

The identification of biocompatible nanomaterials with high conductivities as sensing interfaces is important in developing novel electrochemical cytosensors. We prepared a novel protein-inorganic nanomaterial-bovine serum albumin (BSA) incorporated Ag nanoflowers with three-dimensional porous architectures, using a simple biomimetic method. The BSA-incorporated Ag nanoflowers were modified on a glassy carbon electrode (GCE) surface and conjugated with a targeting lectin molecule, i.e., Sambucus nigra agglutinin (SNA), for sensing DLD-1 human colon cancer cells. The BSA-incorporated Ag nanoflowers were a suitable platform, and showed improved cell-immobilization capacity, and good biocompatibility, with retention of activity of the immobilized cells. These properties are attributed to the large surface area of the porous structure and the natural BSA layer acting as a biocompatible support. The attachment of DLD-1 cells to the GCE increased the electron-transfer resistance, with a good correlation with the logarithm of the concentration from 1.35×10(2) to 1.35×10(7) cells mL(-1), with a low detection limit of 40 cells mL(-1). Based on the affinity between SNA and sialic acid (SA), the UV-vis absorption spectrum of the one-step reaction between SA and acidic ninhydrin indicated that the average number of SA molecules on a single living DLD-1 cell surface was approximately 2.16×10(12). This proposed cytosensing strategy had good reproducibility, acceptable precision, and high specificity for SA-over-expressed cells, indicating that it has potential applications for the early monitoring of tumor cells and convenient evaluation of SA on living cells.

ZnO-Based Nanoplatforms for Labeling and Treatment of Mouse Tumors without Detectable Toxic Side Effects

ZnO quantum dots (QDs) were synthesized with polymer shells, coordinated with Gd(3+) ions and adsorbed doxorubicin (DOX) together to form a new kind of multifunctional ZnO-Gd-DOX nanoplatform. Such pH sensitive nanoplatforms were shown to release DOX to cancer cells in vitro and to mouse tumors in vivo, and reveal better specificity and lower toxicity than free DOX, and even better therapeutic efficacy than an FDA approved commercial DOX-loading drug DOX-Liposome Injection (DOXIL, NDA#050718). The ZnO-Gd-DOX nanoplatforms exhibited strong red fluorescence, which benefited the fluorescent imaging on live mice. Due to the special structure of ZnO-Gd-DOX nanoparticles, such nanoplatforms possessed a high longitudinal relaxivity r1 of 52.5 mM(-1) s(-1) at 0.55 T, which was superior to many other Gd(3+) based nanoparticles. Thus, both fluorescence labeling and magnetic resonance imaging could be applied simultaneously on the tumor bearing mice along with drug delivery. After 36 days of treatment on these mice, ZnO-Gd-DOX nanoparticles greatly inhibited the tumor growth without causing any appreciable abnormality in major organs. The most important merit of ZnO-Gd-DOX was that such a nanoplatform was biodegraded completely and showed no toxic side effects after H&E (hematoxylin and eosin) staining of tumor slices and ICP-AES (inductively coupled plasma atomic emission spectrometry) bioanalyses.

One-pot synthesis of Gd3+-functionalized gold nanoclusters for dual model (fluorescence/magnetic resonance) imaging

Multimodal imaging that aims to advance imaging by strategically combining existing technologies with uniquely designed probes has attracted great interest in recent years. Here, Gd3+-functionalized gold nanoclusters (Gd-AuNCs) were synthesized for dual model (fluorescence/magnetic resonance) imaging. We designed a cyclodecapeptide that contained one tyrosine and two cysteines for the synthesis, and it biomineralized gold nanoclusters and chelated Gd3+ ions at the same time. The Gd-AuNC probes emit an intense red fluorescence under UV light, while exhibiting a high longitudinal relaxivity of 41.5 ± 2.5 mM-1 s-1 and a low r2/r1 ratio of 1.2 at 0.55 T. The versatility of the probes for dual model imaging has been demonstrated by means of cellular imaging and in vivo T1-weighted MRI. Thanks to the optimal size of the nanocluster, it can freely circulate in the blood pool without significant accumulation in the liver and spleen, but with a long circulation half-life (t1/2) of ∼128 min. Moreover, the nanoclusters can be noticeably excreted from the body within a period of 24 h through renal clearance, making it attractive for in vivo multimodal imaging.

Facile preparation of N-doped mesocellular graphene foam from sludge flocs for highly efficient oxygen reduction reaction

The use of environmental waste products as materials for the production of energy is an extremely attractive prospect for both economic and social development. Sludge flocs (SFs) are environmental waste products that are difficult to handle. We used these SFs as a source of carbon and nitrogen for the preparation of N-doped mesocellular graphene foam (SF-NMGF) via a simple one-step pyrolysis method. The particular composition and structure of the SFs meant that the resultant SF-NMGF had a large Brunauer–Emmett–Teller surface area and consisted of a graphitic framework surrounded by ultrathin nanosheets. The material contained foam-like mesopores with a size centred at about 15 nm and the N was incorporated homogeneously with a high percentage (40.5 at%) of graphitic-N. As a result of these unique properties, the SF-NMGF had an excellent electrocatalytic activity with 4e when used as a metal-free catalyst for the oxygen reduction reaction (ORR). Specifically, the prepared SF-NMGF catalyst exhibited a high diffusion-limited current, superior durability and better immunity towards methanol crossover for the ORR in alkaline solution than a commercial 20 wt% Pt/C catalyst. The synthesis of the SF-NMGF can be scaled up at low cost, which will be beneficial for both sludge handling and the development of materials for the ORR.

Electrocatalysis of both oxygen reduction and water oxidation using a cost-effective three-dimensional MnO2/graphene/carbon nanotube

The electrochemical oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are of great interest since they are involved in energy conversion between fuel and electricity. Here, we developed a bifunctional MnO2/graphene/carbon nanotube that is free of noble metals and that could be a promising candidate electrocatalyst for these oxygen reduction and evolution reactions. It was shown to be able to act as an efficient cathode catalyst for the ORR, having a positive half-wave potential that differs by only ∼55 mV from that of commercial Pt/C, and a high cathodic current density that is comparable to that of the Pt/C catalyst. Moreover, the hybrid exhibited superior durability with nearly no decay in ORR activity even after 10 000 s of continuous operation in 0.1 M KOH, while Pt/C shows a 20% decrease in the activity. Most importantly, the hybrid was also shown to be highly active for the OER. These observations show this hybrid to be a high-performance non-precious metal-based bi-catalyst for both the ORR and OER.

Ratiometric Fluorescent Silicon Quantum Dots–Ce6 Complex Probe for the Live Cell Imaging of Highly Reactive Oxygen Species

The monitoring of reactive oxygen species (ROS) in living cells remains challenging because of the complexity, short half-life, and autofluorescence of biological samples. In this work, we designed a ratiometric fluorescent probe for the detection and imaging of ROS, which was constructed from silicon quantum dots (Si QDs) with chlorin e6 (Ce6) through electrostatic attraction and showed well-resolved dual fluorescence emission signals (490 and 660 nm). Sensitive and selective biosensing of hydroxyl radical (•OH) was demonstrated on the basis of fluorescence quenching of the Si QDs and Ce6 as an internal reference to avoid environmental interference, with a detection limit of ∼0.97 μM. The endogenous release of •OH was also monitored and imaged in living cells.