Yang-Wei Lin

Fluorescence detection of lead(II) ions through their induced catalytic activity of DNAzymes.

We have developed a fluorescence approach for the highly selective and sensitive detection of Pb(2+) ions using AGRO100, a G-quadruplex DNAzyme. The sensing strategy is based on Pb(2+) ions inducing increased DNAzyme activity of AGRO100 in the presence of hemin, which acts as a cofactor to catalyze H(2)O(2)-mediated oxidation of Amplex UltraRed (AUR). A test of eight aptamers of various sequences for the detection of Pb(2+) ions revealed that AGRO100 performed the best in terms of sensitivity. The AGRO100-AUR probe exhibited high selectivity (>100-fold) toward Pb(2+) ions over other tested metal ions. The fluorescence intensity (excitation/emission maxima, ca. 561/592 nm) of the AUR product was proportional to the concentration of Pb(2+) ions over the range 0-1000 nM, with a linear correlation (R(2) = 0.98). For 5 mM Tris-acetate (pH 7.4) solutions in the presence and absence of 100 mM NaCl, the AGRO100-AUR probe provided limits of detection (signal-to-noise ratio = 3) for Pb(2+) ions of 1.0 and 0.4 nM, respectively. We validated the practicality of the use of the AGRO100-AUR probe for the determination of the concentrations of Pb(2+) ions in soil samples. This approach allows the determination of the concentrations of Pb(2+) ions with simplicity, selectivity, and sensitivity.

Catalytic gold nanoparticles for fluorescent detection of mercury(II) and lead(II) ions

In this study, we developed a fluorescence assay for the highly sensitive and selective detection of Hg(2+) and Pb(2+) ions using a gold nanoparticle (Au NP)-based probe. The Hg-Au and Pb-Au alloys that formed on the Au NP surfaces allowed the Au NPs to exhibit peroxidase-mimicking catalytic activity in the H(2)O(2)-mediated oxidation of Amplex UltraRed (AUR). The fluorescence of the AUR oxidation product increased upon increasing the concentration of either Hg(2+) or Pb(2+) ions. By controlling the pH values of 5mM tris-acetate buffers at 7.0 and 9.0, this H(2)O(2)-AUR-Au NP probe detected Hg(2+) and Pb(2+) ions, respectively, both with limits of detection (signal-to-noise ratio: 3) of 4.0 nM. The fluorescence intensity of the AUR oxidation product was proportional to the concentrations of Hg(2+) and Pb(2+) ions over ranges 0.05-1 μM (R(2)=0.993) and 0.05-5 μM (R(2)=0.996), respectively. The H(2)O(2)-AUR-Au NP probe was highly selective for Hg(2+) (>100-fold) and Pb(2+) (>300-fold) ions in the presence of other tested metal ions. We validated the practicality of this simple, selective, and sensitive H(2)O(2)-AUR-Au NP probe through determination of the concentrations of Hg(2+) and Pb(2+) ions in a lake water sample and of Pb(2+) ions in a blood sample. To the best of our knowledge, this system is the first example of Au NPs being used as enzyme-mimics for the fluorescence detection of Hg(2+) and Pb(2+) ions.

Photo-assisted synthesis of highly fluorescent ZnSe(S) quantum dots in aqueous solution

This paper describes the synthesis of highly water-soluble and fluorescent ZnSe(S)-alloyed quantum dots (QDs). We used zinc perchlorate hexahydrate, sodium hydrogen selenide as precursors and mercaptopropionic acid as stabilizer to synthesize ZnSe QDs in aqueous solution at 160 °C for 9 h. The as-prepared ZnSe QDs possess a quantum yield (QY) of 8.1% and high trapped emission. After UV irradiation using a 100 W Hg–Xe lamp for 0.5 h, ZnSe(S) QDs having a QY of 19.0% are formed from ZnSe QDs. However, aggregation of ZnSe(S) QDs under longer UV irradiation (> 0.5 h) takes place, leading to instability and irreproducibility. To overcome this, additional thiol compounds (mercaptopropionic acid, mercaptosuccinic acid, 11-mercaptoundecanoic acid, and thioglycolic acid) were separately added to ZnSe QD solutions during UV irradiation. UV irradiation and oxygen accelerate the release of S2− from the thiol compounds, leading to the formation of ZnSe(S) QDs. Among the thiol compounds, mercaptosuccinic acid is the most suitable in terms of stability and photoluminescence intensity. We suggest that the size and functional group of the thiol compounds play an important role in determining the optical properties and stability of ZnSe(S) QDs. The as-prepared ZnSe(S) QDs fluoresce strongly (QY up to 44.0%) at 407 nm with a narrow bandwidth (W1/2 < 25 nm) when excited at 325 nm.

A simple strategy for improving the energy conversion of multilayered CdTe quantum dot-sensitized solar cells†

In this paper we describe the preparation of CdTe quantum dot-sensitized solar cells (QDSSCs). We coated FTO substrates with 21 nm-diameter TiO2nanoparticles (NPs) and then immersed the system in poly(dimethyldiallylammonium chloride) (PDDA) solution under ambient conditions. The treated substrates were then subjected to 3 nm-diameter CdTe NP solution at 100 °C for various periods of times. To increase the degree of deposition and to obtain CdTe QDs of various sizes, we performed the coating of the CdTe QDs through three heating cycles for 24, 12, or 6 h. The as-prepared (TiO2)3-PDDA-(QDCdTe)3-FTO electrodes were then used to fabricate (TiO2)3-PDDA-(QDCdTe)3-FTO QDSSCs employing 1-ethyl-3-methylimidazolium thiocyanate incorporating 1.0 M LiI and 0.1 M I2 as electrolytes. The heating treatment allows the QDSSCs to harvest energy at a higher efficiency in the visible region of solar light. As a result, the as-prepared QDSSCs feature a high energy conversion efficiency (η = 2.02%) and a high open-circuit photovoltage (Voc = 850 mV) at 100% sunlight (AM1.5, 100 mW/cm2).

Nanomaterial-Based Surface-Assisted Laser Desorption/Ionization Mass Spectrometry of Peptides and Proteins

We have investigated six nanomaterials for their applicability as surfaces for the analyses of peptides and proteins using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). Gold nanoparticles (NPs) were useful nanomateriais for small analytes (e.g., glutathione); Pt nanosponges and Fe3O4 NPs were efficient nanomaterials for proteins, with an upper detectable mass limit of ca. 25 kDa. Nanomateriais have several advantages over organic matrices, including lower limits of detection for small analytes and lower batch-to-batch variations (fewer problems associated with “sweet spois”), when used in laser desorption/ionization mass spectrometry.

Fluorescence detection of mercury(II) and lead(II) ions using aptamer/reporter conjugates

We have developed a fluorescence technique for the detection of Hg(2+) and Pb(2+) ions using polythymine (T(33))/benzothiazolium-4-quinolinium dimer derivative (TOTO-3) and polyguanine (G(33))/terbium ions (Tb(3+)) conjugates, respectively. Hg(2+) ions induce T(33) to form folded structures, leading to increased fluorescence of the T(33)/TOTO-3 conjugates. Because Pb(2+) ions compete with Tb(3+) ions to form complexes with G(33), the extent of formation of the G(33)-Tb(3+) complexes decreases upon increasing the Pb(2+) concentration, leading to decreased fluorescence at 545 nm when excited at 290 nm. To minimize interference from Hg(2+) ions during the detection of Pb(2+) ions, we conducted two-step fluorescence measurements; prior to addition of the G(33)/Tb(3+) probe, we recorded the fluorescence of a mixture of the T(33)/TOTO-3 conjugates and Hg(2+) ions. The fluorescence signal obtained was linear with respect to the Hg(2+) concentration over the range 25.0-500 nM (R(2)=0.99); for Pb(2+) ions, it was linear over the range 3.0-50 nM (R(2)=0.98). The limits of detection (at a signal-to-noise ratio of 3) for Hg(2+) and Pb(2+) ions were 10.0 and 1.0 nM, respectively. Relative to other techniques for the detection of Hg(2+) and Pb(2+) ions in soil and water samples, our present approach is simpler, faster, and more cost-effective.

Detection of proteins and protein-ligand complexes using HgTe nanostructure matrixes in surface-assisted laser desorption/ionization mass spectrometry.

We have analyzed peptides, proteins, and protein-drug complexes through surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using HgTe nanostructures as matrixes. We investigated the effects of several parameters, including the concentration of the HgTe nanostructures, the pH of the buffer, and the concentration of salt, on the performance of this system. When HgTe nanostructures are used as matrixes, [M + H](+) ions were the dominant signals. Relative to other commonly used nanomaterials, HgTe nanostructures provided lower background signals from metal clusters, fewer fragment ions, less interference from alkali-adducted analyte ions, and a higher mass range (up to 150,000 Da). The present approach provides limits of detection for angiotensin I and bovine serum albumin of 200 pM and 14 nM, respectively, with great reproducibility (RSD: <25%). We validated the applicability of this method through the detections of (i) the recombinant proteins that were transformed in E. coli, (ii) the specific complex between bovine serum albumin and l-tryptophan, and (iii) a carbonic anhydrase-acetazolamide complex. Our results suggest that this novel and simple SALDI-MS approach using HgTe nanostructures as matrixes might open several new ways for proteomics and the analysis of drug-protein complexes.

Laser-induced fluorescence technique for DNA and proteins separated by capillary electrophoresis

Recent developments in capillary electrophoresis (CE) in conjunction with laser-induced fluorescence (LIF) using long-wavelength (maximum excitation wavelength>500 nm) dyes are reviewed. These dyes are particularly of interest when conducting the analyses of biopolymers by CE-LIF using He-Ne lasers. These systems are benefited from low background, low costs, easy maintenance, and compactness. Derivatizations of DNA and proteins with fluorescent or nonfluorescent chemicals can be carried out prior to, during, or after separations. With the advantages of sensitivity, rapidity, and high efficiency, the applications of CE-LIF to the analysis of polymerase chain reaction products, DNA sequencing, trace analysis of proteins, and single cell analysis have been presented.

Analysis of double-stranded DNA by microchip capillary electrophoresis using polymer solutions containing gold nanoparticles.

The impact of gold nanoparticles (GNPs) on the microchip electrophoretic separation of double-stranded (ds) DNA using poly(ethylene oxide) (PEO) is described. Coating of the 75-microm separation channel on a poly(methyl methacrylate) (PMMA) plate in sequence with poly(vinyl pyrrolidone), PEO, and 13-nm GNPs is effective to improve reproducibility and resolution. In this study, we have also found that adding 13-nm GNPs to 1.5% PEO is extremely important to achieve high resolution and reproducibility for DNA separation. In terms of the stability of the GNPs, 100 mM glycine-citrate buffer at pH 9.2 is a good buffer system for preparing 1.5% PEO. The separation of DNA markers V and VI ranging in size from 8 to 2176 base pairs has been demonstrated using the three-layer-coated PMMA microdevice filled with 1.5% PEO containing the GNPs. Using these conditions, the analysis of the polymerase chain reaction products of UGT1A7 was complete in 7 min, with the relative standard deviation values of the peak heights and migration times less than 2.3% and 2.0%, respectively. In conjunction with stepwise changes of the concentrations of ethidium bromide (0.5 and 5 microg/ml), this method allows improved resolution and sensitivity for DNA markers V and VI.

DNA functionalized gold nanoparticles for bioanalysis

Gold nanoparticles (Au NPs) have become one of the most interesting sensing materials because of their unique size- and shape-dependent optical properties, high extinction coefficients, and super-quenching capability. Au NPs that are bioconjugated with DNA (DNA-Au NPs) have been demonstrated for selective and sensitive detection of analytes such as mercury(ii) ions, platelet-derived growth factor (PDGF), and adenosine triphosphate (ATP). This review focuses on approaches using DNA-Au NPs for colorimetric, fluorescent, and scattering detection of biopolymers and small solutes. We highlight the important roles that the size and concentration of Au NPs, the length and sequence of DNA, the nature of the capping agents, and the ionic strength and pH of solution play in determining the specificity and sensitivity of the nanosensors for the analytes. The advantages and disadvantages of different detection methods for sensing of interesting analytes using DNA-Au NPs will be discussed.