Zhanguang Chen

An aptamer based resonance light scattering assay of prostate specific antigen

Prostate specific antigen (PSA) is a valuable tumor marker for prostate cancer screening. In this work, a novel and sensitive resonance light scattering (RLS) spectral assay of PSA was proposed based on PSA aptamer modified gold nanoparticles (AuNPs). The sulfhydryl modified single-strand aptamer could interact with AuNPs, which made the AuNPs stable in high concentration of salt. In pH 7.0 BR buffer solution, the highly selective combination of PSA and AuNPs-labeling aptamer resulted in the aggregation of AuNPs which showed high RLS intensity. Under the optimal conditions, the magnitude of enhanced RLS intensity (ΔI(RLS)) was proportional to the concentration of PSA in the range from 0.13 to 110 ng/mL, with a detection limit (LOD, 3σ) of 0.032 ng/mL. This developed RLS assay as well as a commercially available enzyme-linked immunosorbent assay (ELISA) kit was successfully applied to the detection of PSA in 15 serum samples, and an excellent correlation of the levels of PSA measured was obtained. This is the first report of the aptamer based RLS assay for PSA and it is also a significant application of instrumental analysis technique.

Rapid and sensitive determination of proteins by enhanced resonance light scattering spectroscopy of sodium lauroyl glutamate.

A rapid and sensitive method for the determination of proteins is proposed based on the measurements of the enhanced resonance light scattering (RLS) spectroscopy of sodium lauroyl glutamate (SLG). Under the optimum conditions, the interaction between SLG and proteins occurred rapidly, resulting in greatly enhanced RLS intensity with the maximum peak located at 394nm. It was found that the enhanced RLS intensities were in proportion to the concentrations of proteins in the range of 0.01-3.1mugml(-1) depending on the kind of proteins. The detection limits were below 6ngml(-1). Compared with some other methods for the determination of proteins, this method shows high sensitivity, low detection limit and simplicity. This is an inexpensive, simple and fast one-step procedure which requires only measuring the RLS intensities. Human serum samples were determined with satisfactory results.

A novel electrochemiluminescence ethanol biosensor based on tris(2,2′-bipyridine) ruthenium (II) and alcohol dehydrogenase immobilized in graphene/bovine serum albumin composite film

We developed a novel electrochemiluminescence (ECL) ethanol biosensor based on Ru(bpy)(3)(2+) and alcohol dehydrogenase (ADH) immobilized by graphene/bovine serum albumin composite film. The graphene film was directly formed on a glassy carbon electrode surface via an in situ reduction of graphene oxide (GO) and Ru(bpy)(3)(2+) was immobilized during its formation. The graphene film acted as both a decorating agent for immobilization of Ru(bpy)(3)(2+) and a matrix to immobilize bovine serum albumin (BSA), meanwhile BSA not only acted as a reductant to reduce GO, but also provided a friendly environment for ADH immobilization. Furthermore, ADH was separated from Ru(bpy)(3)(2+) by the electron-conductive graphene/BSA composite film to retain its enzymatic activity. The experimental results indicated that the biosensor had excellent electrochemical activity, ECL response to ethanol and stability. Such a design of Ru(bpy)(3)(2+)-graphene/BSA film to modify electrode holds a great promise as a new biocompatible platform for the development of enzyme-based ECL biosensors.

Screening DNA-targeted anticancer drug in vitro based on the drug-conjugated DNA by resonance light scattering technique.

A sensitive and reliable assay has been developed to directly screen DNA-targeted anticancer drugs in vitro via using resonance light scattering (RLS) technique. The results of experiments displayed that the increment of RLS intensity was directly proportional to the antitumor effect of anticancer drugs. Through the RLS spectra, the activities of four drugs have been demonstrated as mitoxantrone (MIT)>epirarubicin (EPI)>daunorubicin (DAU)>adriamycin (ADM). However, to further verify the activities of the above four drugs, binding constant (k) for each of them has been calculated by RLS technique as follows: k(RLS) (MIT, 8.75 x 10(5) L mol(-1))>k(RLS) (EPI, 6.58 x 10(5) L mol(-1))>k(RLS) (DAU, 4.79 x 10(5) L mol(-1))>k(RLS) (ADM, 3.82 x 10(5) L mol(-1)). Also, this RLS assay result was validated by seasoned vitro screening methods for anticancer drugs. In all, the proposed RLS is not only a simple, sensitive, objective and straightforward method, but also it is an unprecedented assay for primarily screening DNA-targeted anticancer drugs.

A fluorescence switch sensor for 6-mercaptopurine detection based on gold nanoparticles stabilized by biomacromolecule.

It is of great significance to develop a simple and powerful assay of 6-mercaptopurine (6-MP) because of its serious side effect and variable activity with the plasma concentration. In this contribution, a fluorescence switch sensor for trace amount detection of 6-MP was successfully developed based on the fluorescent gold nanoparticles stabilized by macromolecules. With the turn-off and on of the fluorescence signal at 640 nm of the analytical system, the selectivity of the present assay was largely improved. Trace amount of 6-MP could be detected in the linear range 1.0×10(-7) M-1.2×10(-4) M with a detection limit 1.98×10(-8) M. Under a UV lamp, the color change with the variation of the 6-MP concentration could be seen clearly by naked eyes. The sensitivity and selectivity are several-fold greater than other methods. And also it proved to be able to detect trace amount of 6-MP in real samples. The present assay largely improved the application of spectral methods in quantitative analysis of 6-MP.

Screen anticancer drug in vitro using resonance light scattering technique.

An in vitro screening model using resonance light scattering (RLS) technique with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reagent as the reactive probe to target cancer cell was firstly developed. In this model, MTT was reduced by viable cancer cells to produce a purple formazan. Cell viability was proportional to the number of formazan induced strong light scattering signal. The inhibition rate of anticancer drug was found to vary inversely with the H(22)-MTT system RLS intensity. So it was intuitive to see the sequence of the tumor suppressive activity of six anticancer drugs without data processing by RLS/MTT screening spectra. Compared with the traditional MTT method, this method has high sensitivity, low detection limit and quite intuitive screening results which were identical to those obtained from the MTT colorimetric assay.

Determination of dextrin based on its self-aggregation by resonance light scattering technique

A novel free-probe assay of dextrin was established based on the resonance light scattering (RLS) enhancement in aqueous solution due to the self-aggregation of dextrin. The RLS intensity was well proportional to the concentration of dextrin over the wide range 0.2-14microg mL(-1) and a detection limit 0.02microg mL(-1) was obtained in the optimum conditions. The effect factors such as pH, buffer medium, holding time, ionic strength and temperature were studied in detail. Little or no interference was presented in the detection when adding coexisting substances including various metal ions and some saccharine in the solution. The assay proposed owns the advantages of easy operation, rapidity, sensitivity and practicability. Three synthetic samples and three kinds of medicine samples were analyzed with satisfactory results.

A novel curcumin assay with the metal ion Cu (II) as a simple probe by resonance light scattering technique.

A fantastic resonance light scattering (RLS) enhancement phenomenon was found when the interaction between the metal ion Cu (II) and a natural antioxidant curcumin (C(21)H(20)O(6)) occurred in certain conditions. Based on this phenomenon, a novel and convenient assay of curcumin was developed and successfully applied on the determination of curcumin in human urine samples. This assay applied the RLS technique with a common metal ion Cu (II) as the spectral probe. In the pH range of 6.5-7.5, the interaction between Cu (II) and curcumin occurred and the weak RLS intensity of Cu (II) was greatly enhanced by curcumin. The maximum peak was located at 538.5 nm. Under the optimum conditions, the enhanced RLS intensity was proportional to the concentration of curcumin ranging from 0.4 to 60 microg ml(-1) with the detection limit of 0.07 microg ml(-1). The synthetic and human urine samples were determined satisfactorily. Good recoveries (98.8-102.5%) were obtained in the determination of urine samples, which proved that the assay proposed was reliable and applicable in the determination of curcumin in body fluid. In this work, the RLS and fluorescence spectral characteristics of the chemicals, the optimum conditions of the reaction and the influencing factors were investigated.

Alizarin red S/copper ion-based ensemble for fluorescence turn on detection of glutathione with tunable dynamic range

In this study, a new type of rapid, high sensitive and selective fluorescence turn-on assay for detection of glutathione using an Alizarin Red S/copper ion ensemble is developed. This assay is based on the highly specific interaction between the glutathione and the copper ions and the strong fluorescence Alizarin Red S probe in a competition assay format. The system is simple in design, fast in operation and is more convenient and promising than other methods. The novel strategy eliminated the separation process, chemical modifications, and sophisticated instrumentations. The detection and discrimination process can be seen with the naked eye and can be easily adapted to automated high-throughput screening. The assay has high sensitivity and selectivity for glutathione. The detection limit is 2.3 nM, it is lower than or at least comparable to previous methods. The dynamic range of the sensor can be tuned simply by adjusting the concentration of copper ions. Importantly, the protocol offers high selectivity for the determination of glutathione among amino acids found in proteins, as well as in serum samples. The assay shows great potential for practical application as a disease-associated biomarker and it will be needed to satisfy the great demand of amino acid determination in the fields such as biochemistry, pharmaceuticals, and clinical analysis.

Protein-templated gold nanoclusters based sensor for off–on detection of ciprofloxacin with a high selectivity

In this contribution, bovine serum albumin stabilized gold nanoclusters as novel fluorescent probes were successfully utilized for the detection of ciprofloxacin for the first time. Our prepared gold nanoclusters exhibited strong emission with peak maximum at 635 nm. Cu(2+) was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of ciprofloxacin caused the fluorescence intensity restoration of the Cu(2+)-gold nanoclusters system. The increase in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by ciprofloxacin allows the sensitive detection of ciprofloxacin in the range of 0.4 ng mL(-1) to 50 ng mL(-1). The detection limit for ciprofloxacin is 0.3 ng mL(-1) at a signal-to-noise ratio of 3. The present sensor for ciprofloxacin detection possesses a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results.