Ιατρικά Άρθρα

Δευτέρα 20 Φεβρουαρίου 2017

In situ-synthesized cadmium sulfide nanowire photosensor with a parylene passivation layer for chemiluminescent immunoassays

Publication date: 15 June 2017
Source:Biosensors and Bioelectronics, Volume 92
Author(s): Ju-Hee Im, Hong-Rae Kim, Byoung-Gi An, Young Wook Chang, Min-Jung Kang, Tae-Geol Lee, Jin Gyeng Son, Jae-Gwan Park, Jae-Chul Pyun
The direct in situ synthesis of cadmium sulfide (CdS) nanowires (NWs) was presented by direct synthesis of CdS NWs on the gold surface of an interdigitated electrode (IDE). In this work, we investigated the effect of a strong oxidant on the surfaces of the CdS NWs using X-ray photoelectron spectroscopy, transmission electron microscopy, and time-of-flight secondary ion mass spectrometry. We also fabricated a parylene-C film as a surface passivation layer for in situ-synthesized CdS NW photosensors and investigated the influence of the parylene-C passivation layer on the photoresponse during the coating of parylene-C under vacuum using a quartz crystal microbalance and a photoanalyzer. Finally, we used the in situ-synthesized CdS NW photosensor with the parylene-C passivation layer to detect the chemiluminescence of horseradish peroxidase and luminol and applied it to medical detection of carcinoembryonic antigen.

http://ift.tt/2lFKw7d

A magnetite/PMAA nanospheres-targeting SERS aptasensor for tetracycline sensing using mercapto molecules embedded core/shell nanoparticles for signal amplification

Publication date: 15 June 2017
Source:Biosensors and Bioelectronics, Volume 92
Author(s): Huanhuan Li, Quansheng Chen, Md. Mehedi Hassan, Xiaoxing Chen, Qin Ouyang, Zhiming Guo, Jiewen Zhao
Surface-enhanced Raman scattering (SERS) biosensors have promising potential in the field of antibiotics detection because of their ultrahigh detection sensitivity. This paper reports a rapid and sensitive SERS-based magnetic nanospheres-targeting strategy for sensing tetracycline (TTC) using aptamer-conjugated magnetite colloid nanocrystal clusters (MCNCs)-polymethacrylic acid (PMAA) magnetic nanospheres (MNs) as the recognition and the Au/PATP/SiO2 (APS) as the labels. Initially, MNs were fabricated and conjugated with the aptamers through condensation reaction. MNs possessed high saturation magnetization (Ms) value of 71.5emu/g and excellent biocompatibility, which facilitated the rapid and easy magnetic separation. Then, complementary DNA (cDNA) were loaded on the APS nanocarrier to produce a large amplification factor of Raman signals. The MNs-targeting aptasensor was thus fabricated by immobilizing the APS to the MNs' surfaces via the hybrid reaction between cDNA and aptamers. Sequel, TTC bound successfully to the aptamer upon its addition with the subsequent release of some cDNA-APS into the bulk solution. Under magnet attraction, the nanospheres were deposited together. Consequently, a display of strong SERS signals by supernatants of the resulting mixtures with increasing TTC concentrations was observed. The proposed aptasensor showed excellent performances for TTC detection along with wide linear range of 0.001–100ng/mL, low detection limit 0.001ng/mL, high sensitivity, and good selectivity to the general coexisted interferences.

http://ift.tt/2kT70NN

Direct and label-free influenza virus detection based on multisite binding to sialic acid receptors

Publication date: 15 June 2017
Source:Biosensors and Bioelectronics, Volume 92
Author(s): Yukichi Horiguchi, Tatsuro Goda, Akira Matsumoto, Hiroaki Takeuchi, Shoji Yamaoka, Yuji Miyahara
A system to discriminate human or avian influenza A remains a highly sought-after tool for prevention of influenza pandemics in humans. Selective binding of the influenza A viral hemagglutinin (HA) to specific sialic acid (SA) receptors (Neu5Acα(2-6)Gal in humans, Neu5Acα(2-3)Gal in birds) is determined by the genotype of the HA and neuraminidase (NA) segments, making it one of the key characteristics that distinguishes human or avian influenza A virus. Here we demonstrate the direct detection of whole H1N1 influenza A virus using 6′-sialyllactose (Neu5Acα(2-6)Galβ(1-4)Glc, 6SL)-immobilized gold electrodes as biosensing surfaces. The sensitivity was higher than that of conventional immunochromatographic technique (ICT) for influenza virus and not restricted by genetic drift. The label-free detection technology via direct attachment of a whole virus using a chemically modified electrode is a promising means to provide a simple and rapid diagnostic system for viral infections.

http://ift.tt/2lFD2B8

Tuning of the selectivity of fluorescent peptidyl bioprobe using aggregation induced emission for heavy metal ions by buffering agents in 100% aqueous solutions

Publication date: 15 June 2017
Source:Biosensors and Bioelectronics, Volume 92
Author(s): Lok Nath Neupane, Gi Won Hwang, Keun-Hyeung Lee
Smart fluorescent probes of which the detection of specific target molecules can be controlled are attracting remarkable interest. A fluorescent peptidyl bioprobe (1) was rationally synthesized by conjugating tetraphenylethylene, an aggregation-induced emission (AIE) fluorophore with a peptide receptor (AspHis) that acted as hard and intermediate bases. The selective detection of 1 for specific metal ion in 100% aqueous solutions was controlled by the buffering agents with the chelate effect without the change of pH. In distilled water and phosphate buffered aqueous solution at neutral pH, 1 exhibited a selective Off-On response to a soft metal ion, Hg²⁺ among test metal ions by 100-fold enhancement of the emission at 470nm. 1 showed a selective Off-On response (180-fold enhancement) to a hard metal ion, Al³⁺ ions among test metal ions in Tris buffered aqueous solution at neutral pH and Hexamine (hexamethylenetetramine) buffered aqueous solution at acidic pH. The detection limit of 0.46 ppb for Hg²⁺ and 2.26 ppb for Al³⁺ in each condition was lower than the maximum allowable level of the metal ions in drinking water by EPA. This research helps to understand how buffering agents participate in the complex formation and aggregation of fluorescent probes using an AIE process for the selective detection of specific metal ions in aqueous solutions.

http://ift.tt/2kT3v9O

Versatile transduction scheme based on electrolyte-gated organic field-effect transistor used as immunoassay readout system

Publication date: 15 June 2017
Source:Biosensors and Bioelectronics, Volume 92
Author(s): Benoît Piro, Dengjun Wang, Dihia Benaoudia, Alexandra Tibaldi, Guillaume Anquetin, Vincent Noël, Steeve Reisberg, Giorgio Mattana, Brianna Jackson
We report on an innovative heterogeneous bisphenol A (BPA) immunoassay based on an electrolyte-gated organic field-effect transistor whose organic semiconductor is poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) co-crystallized with an alkyl derivative of bisphenol A. A decrease of the transistor output current is first observed upon antibody specific binding onto the organic semiconductor. Upon bisphenol A addition, the competitive dissociation of the antibody from the semiconductor surface leads to an opposite increase of the output current. We present here a proof-of-concept for bisphenol A detection; the device could be readily adapted to other small organic molecules of interest and is a promising tool for simple, low-cost, portable and easy-to-use biosensors.

Graphical abstract

http://ift.tt/2lFNWa7

A novel turn-on fluorescent strategy for sensing ascorbic acid using graphene quantum dots as fluorescent probe

Publication date: 15 June 2017
Source:Biosensors and Bioelectronics, Volume 92
Author(s): Hua Liu, Weidan Na, Ziping Liu, Xueqian Chen, Xingguang Su
In this paper, a facile and rapid fluorescence turn-on assay for fluorescent detection of ascorbic acid (AA) was developed by using the orange emission graphene quantum dots (GQDs). In the presence of horse radish peroxidase (HRP) and hydrogen peroxide (H2O2), catechol can be oxidized by hydroxyl radicals and converted to o-benzoquinone, which can significantly quench the fluorescence of GQDs. However, when AA present in the system, it can consume part of H2O2 and hydroxyl radicals to inhibit the generation of o-benzoquinone, resulting in fluorescence recovery. Under the optimized experimental conditions, the fluorescence intensity was linearly correlated with the concentration of H2O2 in the range of 3.33–500µM with a detection limit of 1.2µM. The linear detection for AA was in the range from 1.11 to 300µM with a detection limit of 0.32µM. The proposed method was applied to the determination of AA in human serum samples with satisfactory results.

http://ift.tt/2lFD2kC

TiO2 nanowire arrays modified with a simultaneous “etching, doping and deposition” technique for ultrasensitive amperometric immunosensing

Publication date: 15 June 2017
Source:Biosensors and Bioelectronics, Volume 92
Author(s): Xiaoqiang Liu, Xiaohe Huo, Peipei Liu, Yunfei Tang, Jun Xu, Huangxian Ju
In this work, an ultrasensitive immunosensing scaffold was structured with TiO2 nanowire (TiNW) arrays modified with molybdenum (Mo) and MoS2 flakes by a triplex "etching, doping and deposition" technique. The triply modification of TiNW arrays improved their electron transfer, and the decoration of MoS2 flakes on TiNW arrays increased both the conductivity and the specific surface area of TiNW. Accordingly, the triply modified TiNW arrays provided a biocompatible microenviroment for the biomolecules and high specific surface area to load big amount of biomolecules. The immunosensor was prepared by immobilizing capture antibody on the scaffold surface with double amino-reactive crosslinker, and the tracing labels were prepared by immobilizing signal antibody and horseradish peroxidase molecules on cylinder-shaped TiO2 nanorods. After sandwich-type immunoreaction, the tracing labels were quantitatively captured on the immunosensor surface for the detection of carcinoembryonic antigen as a model analyte. This amperometric method showed a linear range of 0.001 and 150ngmL⁻¹ with a detection limit of 0.5pgmL⁻¹. This work provided a promising platform for sensitive amperometric immunosensing of protein biomarkers.

http://ift.tt/2kSTcCP