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Biosensor based on DNA hybridization holds great potential to get higher sensitivity as the optimal DNA hybridization efficiency can be achieved by controlling the distribution and orientation of probe strands on the transducer surface. In this work, an innovative strategy is reported to tap the sensitivity potential of current electrochemiluminescence (ECL) biosensing system by dispersedly anchoring the DNA beacons on the gold nanoparticles (GNPs) array which was electrodeposited on the glassy carbon electrode surface, rather than simply sprawling the coil-like strands onto planar gold surface. The strategy was developed by designing a "signal-on" ECL biosensing switch fabricated on the GNPs nanopatterned electrode surface for enhanced ultra-sensitivity detection of Hg(2+). A 57-mer hairpin-DNA labeled with ferrocene as ECL quencher and a 13-mer DNA labeled with Ru(bpy)3(2+) as reporter were hybridized to construct the signal generator in off-state. A 31-mer thymine (T)-rich capture-DNA was introduced to form T-T mismatches with the loop sequence of the hairpin-DNA in the presence of Hg(2+) and induce the stem-loop open, meanwhile the ECL "signal-on" was triggered. The peak sensitivity with the lowest detection limit of 0.1 nM was achieved with the optimal GNPs number density while exorbitant GNPs deposition resulted in sensitivity deterioration for the biosensor. We expect the present strategy could lead the renovation of the existing probe-immobilized ECL genosensor design to get an even higher sensitivity in ultralow level of target detection such as the identification of genetic diseases and disorders in basic research and clinical application., (Copyright © 2013 Elsevier B.V. All rights reserved.)

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., (Copyright © 2012 Elsevier B.V. All rights reserved.)

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., (Copyright © 2012 Elsevier B.V. All rights reserved.)

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., (Copyright © 2012 Elsevier B.V. All rights reserved.)

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., (Copyright © 2012 Elsevier B.V. All rights reserved.)

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., (2010 Elsevier B.V. All rights reserved.)