Shu-Zhen Tan

Preliminary Recognition of c-Myc Gene Protein Using an Optical Biosensor with Gold Colloid Nanoparticles Based on Localized Surface Plasmon Resonance

Abstract The gold colloidal nanoparticles with a diameter of 24 ± 0.2 nm were prepared, characterized by ultraviolet–visible (UV-vis), transmission electron microscopy (TEM), and cyclic voltammetry, and assembled on a gold plate substrate for constructing an optical nanobiosensor. The nanosensor exhibited distinct optical properties of localized surface plasmon resonance (LSPR), which could be used for recognition of oncogene biomolecules such as the c-Myc (3C7) antibody protein. The LSPR nanobiosensor has also been successfully applied to determination of a pCMV-Myc mammalian expression vector, one kind of DNA plasmids with a linear response range of 6.2–20.0 ng/µL and a detection limit of 2.4 ng/µL.

A novel fluorescence sensor based on covalent immobilization of 3-amino-9-ethylcarbazole by using silver nanoparticles as bridges and carriers

A novel technique of covalent immobilization of indicator dyes in the preparation of fluorescence sensors is developed. Silver nanoparticles are used as bridges and carriers for anchoring indicator dyes. 3-amino-9-ethylcarbazole (AEC) was employed as an example of indicator dyes with terminal amino groups and covalently immobilized onto the outmost surface of a quartz glass slide. First, the glass slide was functionalized by (3-mercaptopropyl) trimethoxysilane (MPS) to form a thiol-terminated self-assembled monolayer, where silver nanoparticles were strongly bound to the surface through covalent bonding. Then, 16-mercaptohexadecanoic acid (MHDA) was self-assembled to bring carboxylic groups onto the surface of silver nanoparticles. A further activation by using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) converted the carboxylic groups into succinimide esters. Finally, the active succinimide esters on the surface of silver nanoparticles were reacted with AEC. Thus, AEC was covalently bound to the glass slide and an AEC-immobilized sensor was obtained. The sensor exhibited very satisfactory reproducibility and reversibility, rapid response and no dye-leaching. Rutin can quench the fluorescence intensity of the sensor and be measured by using the sensor. The linear response of the sensor to rutin covers the range from 2.0 x 10(-6) to 1.5 x 10(-4) molL(-1) with a detection limit of 8.0 x 10(-7) molL(-1). The proposed technique may be feasible to the covalent immobilization of other dyes with primary amino groups.

Multi-wall carbon nanotubes film used for determination of salbutamol sulfate

A multi-walled carbon nanotubes (MWNTs) film modified glassy carbon electrode (GCE) has been fabricated and showed potent electrocatalytic activity toward the electrochemical oxidation of salbutamol sulfate in phosphate buffer solution (pH=7.4). The linear dependence between the oxidation peak current of salbutamol sulfate and its concentration was observed in the range from 5.0 – 25 µmol/L with a detection limit of 1.0 µmol/L. The electrode possessed a nice recovery of 97.2 – 104.4% with good reproducibility and stability for detection of salbutamol sulfate aerosol samples, indicating that it was a feasible method for determination of salbutamol sulfate in actually pharmaceutical samples.

Label-Free and Simple G-quadruplex-based Turn-Off Fluorescence Assay for the Detection of Kanamycin

ABSTRACT We have developed a label-free and turn-off fluorescence assay for the determination of kanamycin. The detection system consists of an aptamer for specifically recognizing kanamycin and two auxiliary probes functionalized with two GGG repeats at the 3′ or 5′ ends for signal reporting. Two probes both hybridize with the aptamer and then their G-rich sequences combine to form a G-quadruplex. When thioflavin T, a fluorophore, is bound to the G-quadruplex, the fluorescence intensity of the solution dramatically increases. Upon the addition of the kanamycin, the aptamer–kanamycin binding inhibits the hybridization of two probes and aptamer, and restrains the GGG repeats from getting closer to form the G-quadruplex structure, resulting a significant decrease in the fluorescence intensity. The proposed aptamer-based fluorescent sensing platform showed a linear relationship with the concentration of kanamycin from 0.6 to 20.0 nM. The detection limit was determined to be 0.33 nM. The sensing platform provides resistance to interferences from other antibiotics and can be used to efficiently recognize kanamycin in real samples.

Novel optical nanobiosensor assembled with silver nanoparticles on gold surface

A novel optical biosensor with gold surface bound silver nanoparticles has been constructed for detection of bio-molecules like antigen, antibody protein and DNA plasmid, which exhibited distinct optical properties of localized surface plasmon resonance (LSPR). The silver colloidal nanoparticles were prepared by using sodium borohydride reduction of silver nitrate and characterized by using UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), and cyclic voltammetry (CV), indicating that the silver colloidals were pure, sphere-shaped and narrow-dispersed size distribution with a diameter of 10 ± 0.5 nm. The silver nanoparticles were well assembled on the gold surface. It caused 3.08 nm of red shift in the peak wavelength (λmax) of LSPR spectrum for the nanosensor exposed to c-Myc (3C7) mouse monoclonal IgG and 3.36 nm of red shift to the corresponding antibody by the immuno-reaction subsequently. The LSPR nanobiosensor has been successfully applied to recognition of a DNA plasmid of pCMV-Myc Mammalian Expression Vector.

Biosensing with Localized Surface Plasmon Resonance Based on Cap-Shaped Gold Nano-Particles

In this paper, the optical biosensors based on cap- shaped gold nano-particles have been constructed by evaporating gold on polystyrene and silica microspheres to form Au caps, which show a novel localized surface plasmon resonance (LSPR). The gold surface on silica spheres modified with a carboxymethyl dextran layer was used for sensing of anti-avidin D with a detection limit of 5.0 nmolldrL-1 and a sensitivity of 3.4 times 10-3 nmldrLldrnmol-1, which was based on surface-bound avidin molecule. Furthermore, a double stranded DNA (dsDNA) with a binding site of hexa sequence AGGTCA for a nuclear receptor, retinoid X receptor beta (RXRbeta), has been successfully immobilized on gold surface via a specific interaction between biotin moiety and streptavidin, and applied to selective recognition of small molecule nuclear ligands like 9-cis retinoic acid.

An Immunosensing System Using Stilbene Glycoside as a Fluorogenic Substrate for an Enzymatic Reaction Model

A natural product, stilbene glycoside (2,3,5,4′-tetrahydroxy-diphenylethylene-2-O-glucoside, TBG), has been evaluated for the first time as a potential substrate for horseradish peroxidase (HRP)-catalyzed fluorogenic reactions. The properties of TBG as a fluorogenic substrate for HRP and its application in a fluorometric enzyme-linked immunosensing system were compared with commercially available substrates such as p-hydroxyphenylpropionic acid (pHPPA), chavicol and Amplex red using Brucella melitensis antibody (BrAb) as a model analyte. The immunosensing body based on HRP-BrAb was constructed by dispersing graphite, BrAg and paraffin wax at room temperature. In a competitive immunoassay procedure, the BrAb competed with HRP-BrAb to react with the immobilized BrAg. In the enzymatic reaction, the binding HRP-BrAb on the sensing body surface can catalyze the polymerization reaction of TBG by H2O2 forming fluorescent dimers and causing an increase in fluorescence intensity. TBG showed comparable ability for HRP detection and its enzyme-linked immunosensing reaction system, in a linear detection ranging of 3.5×10−8∼7.6×10−6g/L and with a detection limit of 1.7×10−9 g/L. The immobilized biocomposite surface could be regenerated with excellent reproducibility (RSD=3.8%) by simply polishing with an alumina paper. The proposed immunosensing system has been used to determine the BrAb in rabbit serum samples with satisfactory results.

Preliminary exploration on bilingual instruction mode and orientation based on internationalization

Bilingual instruction, an educational experiment and reform, integrates language teaching and learning with subject teaching and learning, aiming to improve both language proficiency and academic achievement. This paper tries to explore bilingual instruction orientation as well as feasible instruction models and strategies. Attention is also paid to the problems arising in bilingual instruction. As bilingual instruction is still an ongoing experiment, more efforts and researches should be made to perfect it.