Fu-Chun Gong

A selective artemisinin-sensor using metalloporphyrin as a recognition element entrapped in the Au-nanoparticles-chitosan modified electrodes.

An amperometric artemisinin (ARN) sensor based on the supramolecular recognition of glycosylated metalloporphyrin, which is included in the Au-nanoparticles-chitosan film coated on the glass carbon electrodes, was developed. For the improvement of the selectivity of artemisinin detection, 5,10,15,20-tetrakis[2-(2,3,4,6-tetraacetyl-beta-d-glucopyranosyl)-1-O-phenyl]porphyrin (T(o-glu)PPH) metal complex [FeT(o-glu)PPCl] was synthesized and employed as a ARN-sensitive and -selective material in the amperometric sensors. The proposed [FeT(o-glu)PPCl]/Au-nanoparticles modified electrodes showed excellent selectivity and sensitivity toward ARN with respect to a number of interferents and exhibited stable current response, which can be attributed to the coordination of ARN with the [FeT(o-glu)PPCl] in the electrodes. The calibration graph obtained with the proposed sensor was linear over the range of 1.8x10(-7)-1.7x10(-9)moll(-1), with a detection limit of 1.7x10(-9)moll(-1) for ARN. Significant advantages of the proposed procedure over the conventional reductive electrochemical methods are the selective detection and the relatively low applied potential requirement of the ARN-sensor. The prepared sensor is applied for the determination of ARN in plant samples and the results agreed with the values obtained by the pharmacopoeia method.

A specific nanoprobe for cysteine based on nitrogen-rich fluorescent quantum dots combined with Cu2+

As a new member of the carbon quantum-dot family, fluorescent nitrogen-rich quantum dots (NRQDs) were prepared by a mixed solvothermal method using 2-azidoimidazole and aqueous ammonia as reactants. These NRQDs are rich in nitrogen up to 40.2%, which are endowed with high fluorescence quantum yield, good photostability, water-solubility and favourable biocompatibility. We further explored the use of NRQDs combined with Cu2+ as a nanoprobe for sensing fluorescently of cysteine (Cys) in complex biological samples. In this sensing system, the fluorescence is significantly quenched via energy transfer from NRQDs to Cu2+ for the coordination of amino-containing groups with Cu2+. The strong affinity between Cu 2+ and Cys leads to the formation of Cu2+-Cys complexes and cause the detachment of Cu2+ from the surface of NRQDs, thus the fluorescence of NRQDs recover. This nanoprobe allows analysis of Cys by modulating the switch of the fluorescence of NRQDs with a detection limit of 5.3nM. As expected, the proposed NRQDs-Cu2+complex-based nanoprobes were successfully applied for the determination of Cys in human serum and plasma samples with recoveries ranging from 97.2% to 105.7%. The probe ensemble was also successfully applied to imaging of Cys in living cells with satisfactory results, which shows strong potential for clinical diagnosis.

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.

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.

Corrosion Behaviors on Polycrystalline Gold Substrates in Self‐Assembled Processes of Alkanethiol Monolayers

Abstract The adsorption response behaviors with n‐alkanethiol self‐assembled monolayers (SAMs) formed on the surface of polycrystalline gold grains have been investigated in nitrogen and oxygen saturated tetrahydrofuran (THF) solutions by using in situ quartz crystal microbalance (QCM) and atomic force microscopy (AFM). Comparing with frequency‐decreased process in the nitrogen saturated solution, the response behavior shows a frequency increased process in the oxygen saturated solution, indicating that the gold corrosion is accompanied to occur in the self‐assembled process of organothiol that is due to the thiol induction and oxygen oxidation. In the presence of thiol and oxygen, the corrosion effect is stronger than the adsorption effect of organothiols, such as n‐dodecanethiol molecules on gold, which causes gold loss from the QCM surface, made evident from the observation of many corrosive defects or holes produced on the surface of gold grains by AFM image. Furthermore, the kinetic behavior on the corrosion rate of gold dissolved in the organothiol solution with time has been examined. The maximum quantity of gold dissolved into the thiol solution can be calculated to be approximately 8.7×1013 Au atoms cm−2 from the QCM data during the strong corrosion process in the oxygen saturated solution. The corresponding gold corrosion rates at fast and slow stages can be estimated to be 9.2×1011 and 5.4×1010 Au atoms cm−2 s−1, respectively. The surface coverage of SAMs increases from 3.2 to 31.2%, while the gold loss decreases from about 6 to 0.6% of an Au monolayer in the self‐assembled process.

Intrinsically fluorescent and highly functionalized polymer nanoparticles as probes for the detection of zinc and pyrophosphate ions in rabbit serum samples

Intrinsically fluorescent polymer nanoparticles (F-PNPs) were synthetized from 2-hydroxy-5-methylisophthalaldehyde and melamine by solvothermal method. F-PNPs can emit strong yellow green fluorescence at 542 nm without the conjugation to any external fluorescent agent and surface modification. Owing to the abundant amino and hydroxyl groups on their surface, the F-PNPs possess multiple binding sites, good biocompatibility and excellent water-solubility. Addition of Zn2+ to the F-PNPs solution resulted in a blue shift (Δλ=40 nm) with obvious enhancement in the fluorescence intensity at 502 nm; while there was negligible change in the presence of other metal ions. The subsequent treatment with pyrophosphate (PPi) can cause fluorescence recovery of F-PNPs by pulling the Zn2+ out of the coordination cavity of F-PNPs-Zn2+ nanocomposites. No interference was observed from other anions and nucleotides, making the F-PNPs-Zn2+ ensembles highly sensitive and selective nanoprobes for PPi. The detection limit is 2.75 × 10-8 M/L and 7.63 × 10-8 M/L for Zn2+ and PPi, respectively. The proposed nanoprobes were then used for detecting the recovery of Zn2+ and PPi in rabbit serum samples, which were found to be 99.4-104.2% and 98.6-104.7%, respectively. The present strategy for the fabrication of nanoparticles may offer a new sight for the preparation of polymer nanostructures. The F-FNPs based probes can provide an accurate method for the detection of Zn2+ and PPi in serum samples.