An optical biosensor for rapid and label-free detection of cells

We report a broadly applicable optical method for rapid and label-free detection of as few as 45 cells. In this method, bacterial cells are detected by measuring the amount of laser light transmitted through a small glass well functionalized with antibodies which specifically recognize and capture the cells. The described approach is simple, rapid, economical, and promising for portable and high-throughput detection of a wide variety of pathogenic and infectious cells.     

Electrochemical sensor for estriol hormone detection in biological and environmental samples

A stable conducting film for sensing using reduced graphene oxide (RGO), gold nanoparticles (GNPs), and potato starch (PS) is proposed. The characterization of the nanomaterials was obtained by ultraviolet and visible spectroscopy, dynamic light scattering, zeta potential, Fourier transform infrared spectroscopy, atomic force microscopy, and cyclic voltammetry. The voltammetric behavior of the RGO-GNPs-PS/GCE electrodes was studied in the presence of estriol and the results showed a high anodic peak current at 0.64 V. Under optimal conditions, an analytical curve was obtained, in which the anodic peak estriol was linear in the range from 1.5 to 22 μmol L^?1, with a detection limit of 0.48 μmol L^?1. The modified electrodes were applied for determination of estriol in environmental and biological samples. The proposed electrode was used for estriol determination in water and urine samples, which presented a recovery range from 92.1 to 106%, showing that RGO-GNPs-PS/GCE is a viable alternative for the detection of estriol and can be attractive for several electrochemical applications.     

A molecular light switch Ru complex and quantum dots for the label-free, aptamer-based detection of thrombin

A simple, label-free method for the detection of thrombin has been developed based on the conformational transition of aptamer in the presence of the target by using a molecular light switch, Ru polypyridine complex, and quantum dots as novel fluorescence probes in aqueous solution.     

New detection modality for label-free quantification of DNA in biological samples via superparamagnetic bead aggregation

Combining DNA and superparamagnetic beads in a rotating magnetic field produces multiparticle aggregates that are visually striking, enabling label-free optical detection and quantification of DNA at levels in the picogram per microliter range. DNA in biological samples can be quantified directly by simple analysis of optical images of microfluidic wells placed on a magnetic stirrer without prior DNA purification. Aggregation results from DNA/bead interactions driven either by the presence of a chaotrope (a nonspecific trigger for aggregation) or by hybridization with oligonucleotides on functionalized beads (sequence-specific). This paper demonstrates quantification of DNA with sensitivity comparable to that of the best currently available fluorometric assays. The robustness and sensitivity of the method enable a wide range of applications, illustrated here by counting eukaryotic cells. Using widely available and inexpensive benchtop hardware, the approach provides a highly accessible low-tech microscale alternative to more expensive DNA detection and cell counting techniques.     

An aptamer-based signal-on and multiplexed sensing platform for one-spot simultaneous electronic detection of proteins and small molecules

One-spot signal-on and simultaneous electronic detection of lysozyme and adenosine is achieved based on target-induced release of aptamers and back-filling hybridization of the resulting single stranded DNAs with redox-tags conjugated aptamers.     

Electrogenerated chemiluminescence aptamer-based biosensor for the determination of cocaine

A novel electrogenerated chemiluminescence aptamer-based (ECL-AB) biosensor for the determination of a small molecule drug is designed employing cocaine-binding aptamer as molecular recognition element for cocaine as a model analyte and ruthenium complex served as an ECL label. A 5′-terminal cocaine-binding aptamer with the ECL label at 3′-terminal of the aptamer was utilized as an ECL probe. The ECL-AB biosensors were fabricated by immobilizing the ECL probe onto a gold electrode surface via thiol-Au interactions. An enhanced ECL signal is generated upon recognition of the target cocaine, attributed to a change in the conformation of the ECL probe from random coil-like configuration on the probe-modified film to three-way junction structure, in close proximity to the sensor interface. The integrated ECL intensity versus the concentration of cocaine was linear in the range from 5.0 × 10⁻⁹ to 3.0 × 10⁻⁷ M. The detection limit was 1.0 × 10⁻⁹ M. This work demonstrates that the combination of a highly binding aptamer to analyte with a highly sensitive ECL technique to design ECL-AB biosensor is a great promising approach for the determination of small molecule drugs.     

Potentiometric detection in UPLC as an easy alternative to determine cocaine in biological samples

The analytical methods which are often used for the determination of cocaine in complex biological matrices are a prescreening immunoassay and confirmation by chromatography combined with mass spectrometry. We suggest an ultra‐high‐pressure liquid chromatography combined with a potentiometric detector, as a fast and practical method to detect and quantify cocaine in biological samples. An adsorption/desorption model was used to investigate the usefulness of the potentiometric detector to determine cocaine in complex matrices. Detection limits of 6.3 ng mL^?1 were obtained in plasma and urine, which is below the maximum residue limit (MRL) of 25 ng mL^?1. A set of seven plasma samples and 10 urine samples were classified identically by both methods as exceeding the MRL or being inferior to it. The results obtained with the UPLC/potentiometric detection method were compared with the results obtained with the UPLC/MS method for samples spiked with varying cocaine concentrations. The intraclass correlation coefficient was 0.997 for serum (n =7) and 0.977 for urine (n =8). As liquid chromatography is an established technique, and as potentiometry is very simple and cost‐effective in terms of equipment, we believe that this method is potentially easy, inexpensive, fast and reliable. Copyright © 2014 John Wiley & Sons, Ltd.     

An RNA aptamer-based electrochemical biosensor for detection of theophylline in serum

An electrochemical RNA aptamer-based biosensor for rapid and label-free detection of the bronchodilator theophylline was developed. The 5'-disulfide-functionalized end of the RNA aptamer sequence was immobilized on a gold electrode, and the 3'-amino-functionalized end was conjugated with a ferrocene (Fc) redox probe. Upon binding of theophylline the aptamer switches conformation from an open unfolded state to a closed hairpin-type conformation, resulting in the increased electron-transfer efficiency between Fc and the electrode. The electrochemical response, which was measured by differential pulse voltammetry, reaches saturation within a few minutes after addition of theophylline, and the dynamic range for detecting theophylline is 0.2-10 muM. The electrode displays an inhibited response when applied directly in serum samples treated with RNase inhibitors; however a full response to the theophylline serum concentration was obtained by transferring the electrode to blank serum-free buffer solutions. It was demonstrated that theophylline is detected with high selectivity in the presence of caffeine and theobromine.     

An immunochromatographic assay for rapid and simultaneous detection of levonorgestrel and methylprednisolone in water samples

Synthetic contraceptive levonorgestrel (LNG) and glucocorticoid methylprednisolone (MP) residues are eventually discarded to environmental water system and function as environmental hormones, displaying potential risk to humans and ecosystems, thus there is an urgent need for fast, sensitive and simultaneous detection of these compounds in water samples. In this study, a competitive immunochromatographic assay (ICA) using colloidal gold-labeled polyclonal antibodies as probes for rapid and simultaneous detection of LNG and MP in water samples was developed. The visual detection limits of LNG and MP in water samples were 10 ng/mL. The detection process could be completed within 10 min. There was no cross-reactivity of the ICA with other seven compounds. The strips could be stored at 4℃ for 10 weeks without significant loss of activity. The assay is a suitable tool for rapid and semiquantitative detection of LNG and MP in water samples on site.     

Evanescent wave infrared chemical sensor possessing a sulfonated sensing phase for the selective detection of arginine in biological fluids

This paper describes a new infrared (IR) sensing scheme for the determination of arginine (Arg). In this method, the surface of an IR evanescent wave sensing element was modified with sulfonic acid groups to selectively interact with Arg through specific interactions with its guanidine moiety. The sulfonated sensing phase was prepared using a two-layer modification approach. To demonstrate that this assembly could be used for selective infrared sensing, a large number of amino acids were subjected to analysis. Although the sulfonate groups on the surface of the sensing element did interact selectively with the guanidine groups of Arg species, lysine and histidine units caused some interference; this problem could be minimized because of the unique IR absorption bands of the guanidine moiety of Arg. To optimize the detection conditions, we studied the effects of both the pH and the composition of the polymer. The most intense signal was obtained at pH 9. We observed different adsorption rates for the detection of Arg at different values of pH, which we attribute to changes in the accessibility of the analytes to the pore structures of the sensing phase. The composition of the base polymer was also optimized; 60% PVBC (w/w) provided a water-stable, sensitive phase for the detection of Arg in aqueous solution. Under the optimized conditions, we obtained a linear range of detection up to 0.1 mM with a detection limit of ca. 5 μM.     

Silver nanoparticle based label-free colorimetric immunosensor for rapid detection of neurogenin 1

Neurogenin 1 (ngn1), with the functions of controlling the differentiation of neurons, determining specific neuronal subtype, and inhibiting glial differentiation, is quantitatively detected for the first time. By using specifically modified silver nanoparticles (AgNP) as the signaling element, a label-free, rapid and sensitive colorimetric immunoassay for the synthetic peptide fragment of ngn1 (amino acid sequence: AQDDEQERRRRRGRTR) is reported. The detection procedure is based on an anti-aggregation mechanism, by which ngn1 inhibits the aggregation of the probe in the presence of salt (NaClO(4)). The anti-ngn1 antibody conjugated AgNP (denoted as AgNP-Ab) is negatively charged, and mono-binding of the like-charged ngn1 to the probe will increase the surface charge density, hence enhancing the interparticular electrostatic repulsion. Along with the increase of ngn1 concentration, the color of the solution varies from red to yellow, thereby developing a feasible approach for the detection of ngn1. Using a UV/vis spectrophotometer, this assay exhibits a linear response range of two orders of magnitude, from 50 to 800 ng mL(-1), and a detection limit of 30 ng mL(-1). On the basis of these qualities, the antibody-conjugated AgNP may become a useful tool for point-of-care diagnosis of ngn1 and such a method offers a new insight on the detection of the analogous antigen fragment as well.     

高灵敏光学和电化学适配体传感器在真菌毒素快速检测中的研究进展

高灵敏的生物传感器在痕量真菌毒素污染的快速检测中备受关注.适配体除具有与抗体类似的高选择性外,还具有可体外合成和易修饰等独特优势,已成为现阶段生物传感器中常用的识别元件.随着指数富集的配体系统进化(SELEX)技术的发展,筛选获得的真菌毒素适配体越来越多,为不同真菌毒素的检测提供了基础条件,而适配体结合现代新型纳米材料...     

生物样品中有毒重金属的快速检测与脱除技术研究进展

重金属在工业生产和生活实践中应用广泛,由其引发的中毒案件和事故时有发生。为了及时预防和治疗重金属中毒,亟需探究建立简便、快速的生物样品中重金属检测与脱除方法。然而由于生物样品的基质较为复杂,检测前通常需要繁琐的样品处理。近年来,固体进样等一系列技术迅速发展,在生物样品的快速直接分析中展现出巨大的应用潜力。本文详细评述了适用于生物样品中重金属的快速检测方法,总结了常用的生物体内重金属脱除技术,并对当前研究中的不足以及进一步的发展做了简要展望。