Li-Ping Jiang

One-pot synthesis of aptamer-functionalized silver nanoclusters for cell-type-specific imaging.

As an emerging category of fluorescent metal nanoclusters, oligonucleotide-templated silver nanoclusters (Ag NCs) have attracted a lot of interest and have shown wide application in biorelated disciplines. However, the weak fluorescence emission and poor permeability to cell membranes tethered further intracellular applications of Ag NCs. AS1411 is an antiproliferative G-rich phosphodiester oligonucleotide and currently an anticancer agent under phase II clinical trials. Herein, we present a strategy to synthesize AS1411-functionalized Ag NCs with excellent fluorescence through a facile one-pot process. Confocal laser scanning microscopy and Z-axis scanning confirmed that the AS1411-functionalized Ag NCs could be internalized into MCF-7 human breast cancer cells and were able to specifically stain nuclei with red color. To our surprise, 3-[4,5-dimethylthiazol-z-yl]-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated the Ag NCs were cytocompatible and showed better inhibition effects than pure AS1411 on MCF-7 human breast cancer cells. In addition, a universal design of the oligonucleotide scaffold for synthesis of Ag NCs was extended to other aptamers, such as Sgc8c and mucin 1 aptamer. Due to the facile synthesis procedure and capability of specific target recognition, this fluorescent platform will potentially broaden the applications of Ag NCs in biosensing and biological imaging.

Graphene–CdS Nanocomposites: Facile One‐Step Synthesis and Enhanced Photoelectrochemical Cytosensing

Graphene-CdS (GR-CdS) nanocomposites were prepared in a one-step synthesis in aqueous solution. The synthetic approach was simple and fast, and it may be extended for the synthesis of other GR-metal-sulfide nanocomposites. The as-prepared GR-CdS nanocomposite films inherited the excellent electron-transport properties of GR. In addition, the heteronanostructure of the GR-CdS nanocomposites facilitated the spatial separation of the charge carriers, thus resulting in enhanced photocurrent intensity, which makes it a promising candidate for photoelectrochemical applications. This strategy was used for the fabrication of an advanced photoelectrochemical cytosensor, based on these GR-CdS nanocomposites, by using a layer-by-layer assembly process. This photoelectrochemical cytosensor showed a good photoelectronic effect and cell-capture ability, and had a wide linear range and low detection limit for Hela cells. The as-synthesized GR-CdS nanocomposites exhibited obviously enhanced photovoltaic properties, which could be an efficient platform for many other high-performance photovoltaic devices.

Ultrasensitive Multianalyte Electrochemical Immunoassay Based on Metal Ion Functionalized Titanium Phosphate Nanospheres

A novel multianalyte electrochemical immunoassay was developed for ultrasensitive detection of human cardiopathy biomarkers cardiac troponin I (cTnI) and human heart-type fatty-acid-binding protein (FABP) using metal ion functionalized titanium phosphate nanospheres (TiP-metal ion) as labels. The metal ions could be detected directly through square wave voltammetry (SWV) without metal preconcentration, and the distinct voltammetric peaks had a close relationship with each sandwich-type immunoreaction. The position and size of the peaks reflected the identity and level of the corresponding antigen. The large amount of metal ions loading on the TiP nanospheres greatly amplified the detection signals, and the good biocompatibility of graphene nanoribbons (GONRs) retained good stability for the sandwich-type immunoassay. The proposed immunoassay exhibited high sensitivity and selectivity for the detection of cTnI and FABP. The linear relationships between electrochemical signals and the concentrations of cTnI and FABP were obtained in the range of 0.05 pg/mL-50 ng/mL and 0.05 pg/mL-50 ng/mL, respectively. The detection limits of cTnI and HIgG were 1 and 3 fg/mL (S/N = 3), respectively. Moreover, the immunoassay accurately detected the concentrations of cTnI and FABP in human serum samples, which were demonstrated to have excellent correlations with the standard enzyme linked immunosorbent assay (ELISA) method. The results suggested that the electrochemical immunoassay would be promising in the point-of-care diagnostics application of clinical screening of acute myocardial infarction (AMI) biomarkers.

Electrochemical immunosensor of tumor necrosis factor α based on alkaline phosphatase functionalized nanospheres.

A novel immunosensor for sensitive detection of tumor necrosis factor α was reported. First of all, gold nanoparticles were uniformly assembled on the surface of poly (styrene-acrylic acid) nanospheres, which was used as the matrix to conjugate alkaline phosphatase (ALP). And then, the obtained composite was used as multi-enzyme functionalized label for immunoassay. Biocompatible polyaniline doped with poly (acrylic acid) was electro-polymerized at the glass carbon electrode to construct the matrix for the immobilization of antibody TNF-α. After the sandwich immunoreaction, the labeled ALP was used to hydrolyze α-naphthyl phosphate to produce the electroactive α-naphthol, which could be amperometrically detected. The results showed that the electrochemical signals were proportional to the logarithm of the antigen concentration in the range of 0.02-200.00 ng/mL with the detection limit of 0.01 ng/mL. The developed immunoassay showed high sensitivity, acceptable stability and reproducibility, which might have potentially broad applications in protein diagnostics and bioassay.

Preparation and Electrochemistry of Hydrous Ruthenium Oxide/Active Carbon Electrode Materials for Supercapacitor

Amorphous hydrous ruthenium oxide/active carbon (RuO 2 .xH 2 O/C) powders were prepared by a simple procedure based on the sol-gel process. The precursor was obtained hy mixing an aqueous solution of RuCl 3 and active carhon powders at pH 7. When annealing the precursor at 150°C for 7-9.5 h, the RuO 2 .xH 2 O/C powders obtained had the highest specific capacitance. Transmission electron microscopy photographs showed that the RuO 2 .xH 2 O primary particles were about 10-15 nm diam. They adhered to form large porous secondary particles. A modeling capacitor was made with electrodes comprised of RuO 2 .xH 2 O/C powder and 30% H 2 SO 4 electrolyte. At 10-20 wt % ruthenium in the electrodes, the specific capacitance remained almost unchanged at 243 F/g, which included both the electric double-layer capacitance associated with the high surface area of active carbon and redox capacitance associated with ruthenium oxide. About 52% of the RuO 2 in the RuO 2 .xH 2 O/C powders was utilized. More than 50% of the capacitance in the electrode with 12. 1% ruthenium was due to the formation of the double layer, but for the electrode with 21.1% ruthenium, the capacitance attributed to the double layer dropped to 16.8% of the total capacitance. When the electrodes contained ruthenium from 35 wt % to pure RuO 2 .xH 2 O, the specific capacitance increased from 350 to 715 F/g. The specific capacitance was proportional to the mass of the ruthenium in the electrodes. This enabled the specific capacitance to be controlled by changing the mass ratio of RuCl 3 to active carbon in the preparation. Physical properties of the material and electrochemical characteristics of electrodes are also reported along with the capacitor performance.

Near infrared sensing based on fluorescence resonance energy transfer between Mn:CdTe quantum dots and Au nanorods.

A novel sensing system based on the near infrared (NIR) fluorescence resonance energy transfer (FRET) between Mn:CdTe quantum dots (Qdots) and Au nanorods (AuNRs) was established for the detection of human IgG. The NIR-emitting Qdots linked with goat anti-human IgG (Mn:CdTe-Ab1) and AuNRs linked with rabbit anti-human IgG (AuNRs-Ab2) acted as fluorescence donors and acceptors, respectively. FRET occurred by human IgG with the specific antigen-antibody interaction. And human IgG was detected based on the modulation in FRET efficiency. The calibration graph was linear over the range of 0.05-2.5 microM of human IgG under optimal conditions. The proposed sensing system can decrease the interference of biomolecules in NIR region and increase FRET efficiency in optimizing the spectral overlap of AuNRs with Mn:CdTe Qdots. This method has great potential for multiplex assay with different donor-acceptor pairs.

Highly sensitive photoelectrochemical assay for DNA methyltransferase activity and inhibitor screening by exciton energy transfer coupled with enzyme cleavage biosensing strategy

Highly sensitive DNA methyltransferase (MTase) activity and inhibitor screening photoelectrochemical (PEC) assay was developed based on the exciton energy transfer (EET) effect coupled with site-specific cleavage of restriction endonuclease (HpaII). The assay was designed by integrating the Au nanoparticles (NPs) labeled probe DNA (pDNA-Au) with CdSe quantum dots (QDs). The strong EET effect between Au NPs and CdSe QDs resulted in the dramatic decrease of photocurrent signal. The pDNA carried a sensing region for specifically recognizing target DNA (tDNA) and hybridizing with it to form a DNA duplex. With the site-specific cleavage of HpaII, the DNA duplex could be cleaved and Au NPs would be released, which broke the EET and resulted in the restoration of photocurrent signal. However, when the DNA duplex was methylated by M.SssI MTase, this cleavage of HpaII was blocked, and therefore the unbroken EET effect kept the lower photocurrent signal. That was, the restored photocurrent was inversely proportional to the MTase activity. Based on this strategy, the PEC assay could determine as low as ~0.0042 U/mL of M.SssI MTase with a linear range from 0.01 to 150 U/mL. In addition, the assay could be used for the screening of the inhibitors of MTase. This PEC assay provides a promising platform for monitoring the activity and inhibition of DNA MTase, and thus shows a great potential in cancer diagnostics and anti-cancer drugs discovery.

High-Efficient Energy Funneling Based on Electrochemiluminescence Resonance Energy Transfer in Graded-Gap Quantum Dots Bilayers for Immunoassay

A surprising electrochemiluminescence (ECL) enhancement effect in graded-gap CdSeTe@ZnS-SiO2 quantum dot (QD) bilayers was observed and used to create an ultrasensitive immunoassay. CdSeTe@ZnS-SiO2 QDs of two different sizes were used as a donor-acceptor pair, owing to their tunable energy and low biotoxicity. The graded-gap CdSeTe@ZnS-SiO2 QD bilayers were fabricated by layer-by-layer assembly of differently sized CdSeTe@ZnS-SiO2 QDs on a glutaraldehyde-activated electrode. Benefiting from a short interlayer distance and perfect spectral overlap in the graded-gap QD bilayers, highly efficient ECL resonance energy transfer (ECLRET)-based energy funneling was observed, wherein excitons from trapped states could be effectively recycled. Consequently, the observed ECL enhancement for the bilayers was more than four times greater than that observed for reference samples. The graded-gap QD bilayers were utilized in an ECL biosensor for the detection of carcinoembryonic antigen (CEA). The proposed method featured a detection limit of 0.4 pg mL(-1) CEA with a linear calibration range from 1 pg mL(-1) to 200 ng mL(-1). This method represents a novel approach for versatile detection of biomolecules in research and clinical applications.

Manganese-Doped ZnSe Quantum Dots as a Probe for Time-Resolved Fluorescence Detection of 5-Fluorouracil

Quantum dots (QDs) are generally used for the conventional fluorescence detection. However, it is difficult for the QDs to be applied in time-resolved fluorometry due to their short-lived emission. In this paper, high-quality Mn-doped ZnSe QDs with long-lived emission were prepared using a green and rapid microwave-assisted synthetic approach in aqueous solution. Fluorescence lifetime of the Mn-doped ZnSe QDs was extended as long as 400 μs, which was 10,000 times higher than that of conventional QDs such as CdS, CdSe, and CdTe. The QDs exhibited an excellent photostability over 35 h under continuous irradiation at 260 nm. Capped with mercaptopropionic acid (MPA), the Mn-doped ZnSe QDs were used for the time-resolved fluorescence detection of 5-fluorouracil (5-FU) with the detection limit of 128 nM. The relative standard deviation for seven independent measurements of 1.5 μM 5-FU was 3.8%, and the recovery ranged from 93% to 106%. The results revealed that the Mn-doped ZnSe QDs could be a good candidate as a luminescence probe for highly sensitive time-resolved fluorometry.

Gold nanoparticle-assembled capsules and their application as hydrogen peroxide biosensor based on hemoglobin

Gold nanoparticle-assembled capsules (GNACs) with controllable size and tunable morphology were fabricated through a simple two-step mixing procedure. Cationic polyelectrolyte was first induced to self-assemble into spherical aggregates in the presence of multivalent anions. Then, the aggregates served as an effective template for the self-assembly of gold nanoparticles to form size-controllable capsules. By adjusting the quantity of gold nanoparticles, capsules with various morphologies could be obtained. Because of their unique nanoporous features, the capsules with intact shells were further used to load hemoglobin (Hb) for the fabrication of a novel H(2)O(2) biosensor. The results of UV-vis spectroscopy and cyclic voltammetry indicated that the capsules provided a suitable matrix for the immobilization of Hb. Additionally, the resulting biosensor showed a high affinity and good catalytic activity to H(2)O(2). With the advantages of the large surface area, good conductivity and biocompatibility, the GNACs can offer a promising platform for the development of biosensors. Moreover, on the basis of the capsule structure, this material may also be expected to apply in some fields such as drug delivery, medical diagnostics and bio-encapsulation.