Jilie Kong

Luminescent carbon quantum dots and their application in cell imaging

A facile hydrothermal method was used to synthesize luminescent carbon dots from single-walled carbon nanotubes (SWNTs). Then 4,7,10-trioxa-1,13-tridecanediamine (TTDDA) was grafted onto the carbon dots to increase their water solubility and luminescent properties. The as-prepared carbon dots were characterized by UV-Vis absorption, infrared (IR), Raman, fluorescence, and transmission electron microscopy (TEM). The results confirmed that these carbon dots were monodispersed in water and emitted bright yellow fluorescence. The surface modified carbon dots were used to label biological cells, and the images obtained by a laser scanning confocal microscope showed that the carbon dots were gradually taken up by HeLa cells. The cytotoxicity of such carbon dots toward HeLa cells was very low, for 24 h the LC50 was over 5 mg mL−1.

Bio-electrocatalysis of NADH and ethanol based on graphene sheets modified electrodes.

Characterization and application of graphene sheets modified glassy carbon electrodes (graphene/GC) have been presented for the electrochemical bio-sensing. A probe molecule, potassium ferricyanide is employed to study the electrochemical response at the graphene/GC electrode, which shows better electron transfer than graphite modified (graphite/GC) and bare glassy carbon (GC) electrodes. Based on the highly enhanced electrochemical activity of NADH, alcohol dehydrogenase (ADH) is immobilized on the graphene modified electrode and displays a more desirable analytical performance in the detection of ethanol, compared with graphite/GC or GC based bio-electrodes. It also exhibits good performance of ethanol detection in the real samples. From the results of electrochemical investigation, graphene sheets with a favorable electrochemical activity could be an advanced carbon electrode materials for the design of electrochemical sensors and biosensors.

Gold Nanoparticle Assembly Microfluidic Reactor for Efficient On-line Proteolysis

A microchip reactor coated with a gold nanoparticle network entrapping trypsin was designed for the efficient on-line proteolysis of low level proteins and complex extracts originating from mouse macrophages. The nanostructured surface coating was assembled via a layer-by-layer electrostatic binding of poly(diallyldimethylammonium chloride) and gold nanoparticles. The assembly process was monitored by UV-visible spectroscopy, atomic force microscopy, and quartz crystal microbalance. The controlled adsorption of trypsin was theoretically studied on the basis of the Langmuir isotherm model, and the fitted Γmax and K values were estimated to be 1.2 × 10−7 mol/m2 and 4.1 × 105 m−1, respectively. An enzymatic kinetics assay confirmed that trypsin, which was entrapped in the biocompatible gold nanoparticle network with a high loading capacity, preserved its bioactivity. The maximum proteolytic rate of the adsorbed trypsin was 400 mm/(min·μg). Trace amounts of proteins down to femtomole per analysis were digested using the microchip reactor, and the resulting tryptic products were identified by MALDI-TOF MS/MS. The protein mixtures extracted from the mouse macrophages were efficiently identified by on-line digestion and LC-ESI-MS/MS analysis.

ZnO@silica core–shell nanoparticles with remarkable luminescence and stability in cell imaging

Monodispersed silica-coated ZnO nanoparticles were successfully synthesized and modified with hydrophilic amino groups on the surfaces. The emission colour of the as-prepared ZnO nanoparticles could be tuned by adjusting the reactant ratio and the reaction time. The resulting particles were stable in water, phosphate buffer saline and cell culture medium. Their aqueous solutions had high quantum yields of 53.8%, 48.7% and 33.5%, corresponding to blue, green and yellow emitting ZnO@silica nanoparticles respectively. And the cytotoxicity (24 hours LC50 for Hela cells) of these three samples was 315, 374 and 241 μg mL−1 respectively. The cytotoxicity data and the cellular uptake kinetics experiments confirmed the safety of all these ZnO@silica nanoparticles under visible light, while under UV light of 365 nm the yellow emitting ZnO@silica was fatal to Hela cells because it released plenty of reactive oxygen species.

TiO2‐Modified Macroporous Silica Foams for Advanced Enrichment of Multi‐Phosphorylated Peptides

Enriching peptides: Novel TiO(2)-modified macroporous materials (Ti-MOSF, see figure) have been synthesized with high surface area, large pore volume, and functional surfaces that are rich in coordinatively unsaturated Ti(IV) species, which can be applied in the specific extraction of phosphopeptides and which show a preferential capture of multi-phosphorylated peptides with low detection limits and high selectivity.

Nitrogen-doped carbon dots derived from polyvinyl pyrrolidone and their multicolor cell imaging

Nitrogen-doped carbon dots (N-CDs) with a high quantum yield of 19.6% were prepared by calcining polyvinyl pyrrolidone (PVP, K-30), and then modified with 4,7,10-trioxa-1,13-tridecanediamine. The as-prepared N-CDs exhibited excitation-dependent and pH-sensitive photoluminescence. Transmission electron microscopy and Raman spectra demonstrated the graphitic structure of the N-CDs. Fourier transform infrared spectroscopy and x-ray diffraction studies revealed successful passivation and the presence of hydrophilic groups on the surface. Importantly, such modified quantum dots acted as good multicolor cell imaging probes due to their excellent fluorescent properties, low cytotoxicity and fine dispersity.

MALDI In-Source Photooxidation Reactions for Online Peptide Tagging†

F o r MALDI-MS analysis , thephotoelectrode is coated with the sample and a matrixoverlayer (a -cyano-4-hydroxycinnamic acid ; CHCA) isadded to assist light-energy absorption and protonation ofthe sample . One advantage of the photoelectrode-modifiedplate is that it enables the determination of the oxidation orreduction products of a given molecule . If this oxidation/reduction induces fragmentation of the analytes , the photo-electrode generates in-source decay upon irradiation. Alter -natively ,the oxidation/reduction products may in turn furtherreact with other molecules , and all the products of theseelectron-transfer chain reactions can be directly studied bymass spectrometry .T o illustrate this principle ,w e use the addition reaction ofoxidized hydroquinone on cysteine-containing peptides ,which has previously been demonstrated with electrosprayionization.

Bicontinuous gyroidal mesoporous carbon matrix for facilitating protein electrochemical and bioelectrocatalytic performances

A strategy of protein-entrapment in bicontinuous gyroidal mesoporous carbon (BGMC) nanocomposite films is described. Herein, the quasi-reversible electron transfer of redox proteins (such as glucose oxidase and myoglobin) is probed and the associated biocatalytic activity is revealed. The apparent heterogeneous electron transfer rate constant of the immobilized glucose oxidase is up to 9.4 s(-1), much larger than those in carbon nanotubes and some conventional mesoporous carbons. The BGMC based glucose biosensor enables the determination of glucose at a potential of 0.6 V (vs. SCE). Its detection limit is 1.0×10(-5) M (signal-to-noise ratio, S/N=3), the linear response is up to 7.49 mM and the detection sensitivity is 52.5 nA mM(-1) Furthermore, a series of BGMCs with different pore sizes is designed and synthesized using sucrose or phenol formaldehyde resin to study the influences of pore sizes and carbon sources on the immobilization of redox proteins and on the heterogeneous electron transfer.