Biosensors & bioelectronics

Publications in this journal

• Article: Preparation, characterization of Fe(3)O(4) at TiO(2) magnetic nanoparticles and their application for immunoassay of biomarker of exposure to organophosphorus pesticides.

  Xiao Zhang, Hongbo Wang, Chunming Yang, Dan Du, Yuehe Lin
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  ABSTRACT: Novel Fe(3)O(4) at TiO(2) magnetic nanoparticles were prepared and developed for a new nanoparticle-based immunosensor for electrochemical quantification of organophosphorylated butyrylcholinesterase (BChE) in plasma, a specific biomarker of exposure to organophosphorus (OP) agents. The Fe(3)O(4) at TiO(2) nanoparticles were synthesized by hydrolysis of tetrabutyltitanate on the surface of Fe(3)O(4) magnetic nanospheres, and characterized by attenuated total reflection Fourier-transform infrared spectra, transmission electron microscope and X-ray diffraction. The functional Fe(3)O(4) at TiO(2) nanoparticles were performed as capture antibody to selectively enrich phosphorylated moiety instead of phosphoserine antibody in the traditional sandwich immunoassays. The secondary recognition was performed by quantum dots (QDs)-tagged anti-BChE antibody (QDs-anti-BChE). With the help of a magnet, the resulting sandwich-like complex, Fe(3)O(4) at TiO(2)/OP-BChE/QDs-anti-BChE, was easily isolated from sample solutions and the released cadmium ions were detected on a disposable screen-printed electrode (SPE). The binding affinities were investigated by both surface plasmon resonance (SPR) and square wave voltammetry (SWV). This method not only avoids the drawback of unavailability of commercial OP-specific antibody but also amplifies detection signal by QDs-tags together with easy separation of samples by magnetic forces. The proposed immunosensor yields a linear response over a broad OP-BChE concentrations range from 0.02 to 10nM, with detection limit of 0.01nM. Moreover, the disposable nanoparticle-based immunosensor has been validated with human plasma samples. It offers a new method for rapid, sensitive, selective and inexpensive screening/evaluating exposure to OP pesticides and nerve agents.
  Biosensors & bioelectronics 10/2013;
• Article: Recent advances and challenges in the anode architecture and their modifications for the applications of microbial fuel cells.

  G Gnana Kumar, V G Sathiya Sarathi, Kee Suk Nahm
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  ABSTRACT: Microbial fuel cells (MFC), the ergonomic technology connects the liaison of fuel cell architecture and biological resources. Many viable applications like wastewater treatment, biosensors and bioremediation can be made possible with the help of MFCs. This technology is still at its toddler stage and immense works are still in progress to increase the volumetric energy density of MFCs. The overall performance of MFC depends on the cardinal part of the system; anode. A number of anode materials are currently in research to adjudge the better one in terms of the startup time, power output and durability. A wide range of possibilities are now currently available in the fabrication and modification of anode materials to substantially increase the power performances. This review adumbrates the significant requirements of anodes that are essential to be fulfilled, encompasses the aspiring research efforts which have been devoted so far in the anode modification and fabrication strategies to increase the power output, durability and compatibility of the anode interface with the inoculated microorganisms.
  Biosensors & bioelectronics 05/2013; 43:461-75.
• Article: Handy, rapid and multiplex detection of tumor markers based on encoded silica-hydrogel hybrid beads array chip.

  Zi-Xue Yang, Bao-An Chen, Heng Wang, Guo-Hua Xia, Jian Cheng, Xiao-Ping Pei, Fei Wang, Wen Bao
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  ABSTRACT: Malignant tumor has become the leading cause of death worldwide; however, multiplex detection technology could provide great assistance in large-scale population screening of diseases which could effectively reduce the mortality of malignant tumors. Here a microbeads array chip, which could be a perfect alternative method for the early screening, was developed. Silica-hydrogel hybrid bead (SHHB) with photonic encoding, which consists of both silica and hydrogel materials, was manufactured as the carrier of microbeads array for the first time. The SHHB has the advantages of the beads made of silica or hydrogel, but does not have their limitations. Reaction conditions of SHHBs array were optimized and then the fluorescent concentration curves of two widely-used tumor markers, human alpha fetoprotein and carcinoembryonic antigen, were constructed. The accuracy of SHHBs array has been proven according to the comparison between the results obtained by detecting 50 clinical samples with SHHBs array and chemiluminescence immunoassay. A cassette like chip device has also been developed to standardize operational processes and benefit automization in the next work. Hence it is concluded that SHHBs array chip is a handy, rapid and multiplex immunoassay technology, which could imply its practical application in clinical immunoassay in the near future.
  Biosensors & bioelectronics 04/2013; 48C:153-157.
• Article: Mechanism and enhancement of the surface stress caused by a small-molecule antigen and antibody binding.

  Shangquan Wu, Tiegui Nan, Changguo Xue, Teng Cheng, Hong Liu, Baomin Wang, Qingchuan Zhang, Xiaoping Wu
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  ABSTRACT: Generation of microcantilever bending from biochemical interactions can have wide applications, ranging from high-throughput molecular detection to bioactuation. However, the origin of the biochemically induced surface stress causing the bending is a subject of much scientific debate and interest. Unlike a compressive surface stress caused by biomacromolecule antigen and antibody binding, here we show that a small molecule antigen and antibody binding on the surface gives rise to a tensile stress. We propose that the tensile stress is induced by antibody conformational change which manifests itself as Fab arm motion that exposes the C1q binding site of the antibody due to antigen binding. A microcantilever immunosensor was developed for the detection of Chlorimuron-ethyl (CE). We found that antibodies with oriented immobilization induce a greater resultant surface stress than those with random immobilization. The length of linker between the surface and the antibody plays an important role on the stress transmission. The shorter the length, the greater the surface stress. These mechanism and principles will underpin the design of devices and coatings to significantly lower the small molecule detection limit and may also have an impact on our understanding of antigen and antibody binding.
  Biosensors & bioelectronics 04/2013; 48C:67-74.
• Article: Aptamer biosensor for label-free impedance spectroscopy detection of potassium ion based on DNA G-quadruplex conformation.

  Zhengbo Chen, Liang Chen, He Ma, Tong Zhou, Xiaoxiao Li
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  ABSTRACT: Herein, a label-free and highly sensitive electrochemical impedance spectroscopy (EIS) aptasensor for the detection of potassium ion (K(+)) was developed based on a conformational change in which a K(+)-stabilized single stranded DNA (ssDNA) with G-rich sequence was used as the recognition element. In the measurement of K(+) ions, the change in interfacial electron transfer resistance (Rct) of the sensor using a redox couple of [Fe(CN)6](3-/4-) as the probe was monitored. In the presence of K(+), the G-rich DNA folded into the G-quadruplex structure, and then K(+) can bind to the G-quadruplex structure, leading to an increase in the Rct. The Rct increased with K(+) concentration, and the plot of Rct against the logarithm of K(+) concentration is linear over the range from 0.1nM to 1mM with a detection limit of 0.1nM. Other metal ions, such as Ca(2+), Mg(2+), Na(+), Li(+), Al(3+), Zn(2+), Cu(2+), and Ni(2+) caused no notable interference on the detection of K(+). The scheme reported herein is applicable to the detection of other kinds of G-rich aptamer-binding chemicals and biomolecules.
  Biosensors & bioelectronics 04/2013; 48C:108-112.
• Article: A sensitive and selective chemosensor for GSSG detection based on the recovered fluorescence of NDPA-Fe3O4@SiO2-Cu(II) nanomaterial.

  Ya Ma, Baozhan Zheng, Yan Zhao, Hongyan Yuan, Yuqing Cai, Juan Du, Dan Xiao
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  ABSTRACT: A sensitive and selective sensor for oxidized glutathione (GSSG) detection based on the recovered fluorescence of naphthalimide-DPA (NDPA)-Fe3O4@SiO2-Cu(II) system is reported. NDPA-Fe3O4@SiO2 was characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR) and fluorophotometry. The fluorescence of NDPA-Fe3O4@SiO2 could be quenched by Cu(2+) due to the coordination of Cu(2+) with the tridentate receptor DPA. This coordination process reduced the electron-donating ability of the nitrogen atom in the DPA moiety, thus suppressing the internal charge transfer (ICT) process in NDPA-Fe3O4@SiO2. In the presence of GSSG, the fluorescence of NDPA-Fe3O4@SiO2-Cu(II) was recovered because of strong coordination of Cu(2+) with GSSG, which promoted the decomplexation between NDPA-Fe3O4@SiO2 and Cu(2+), and enhanced the ICT process. The NDPA-Fe3O4@SiO2-Cu(II) nanomaterial exhibited high sensitivity towards GSSG, and a good linear relationship was obtained from 5nM to 60μM. The limit of detection, based on a signal-to-noise ratio of 3, was 50pM. In addition, the presence of magnetic Fe3O4 nanoparticles (NPs) in NDPA-Fe3O4@SiO2 NPs would also facilitate the magnetic separation of NDPA-Fe3O4@SiO2 from the solution. Through the use of added internal standards, we successfully determined the concentration of GSSG in HEK 293 cell lysate to be 1.15μM by the prepared chemsensor NDPA-Fe3O4@SiO2-Cu(II). The proposed method is anticipated to fabricate other sensitive fluorescence sensors based on organic-inorganic hybrid magnetic nanoparticles.
  Biosensors & bioelectronics 04/2013; 48C:138-144.
• Article: A one-step, electrochemical biosensing strategy that is based on transport of signaling CdS nanoparticles controlled by biomolecules.

  Byoung Yeon Won, Sujeong Shin, Dae-Yeon Cho, Hyun Gyu Park
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  ABSTRACT: A novel, one-step electrochemical biosensing technique has been developed by utilizing a strategy in which a biomolecule controls transport of CdS-signaling nanoparticles to the surface of an electrode. The viability of this approach was explored using DNA as a model target biomolecule. The capture and signaling probes both contain nucleic acid sequences that are complementary to the target DNA. The detection chamber consists of a gold matrix modified with the capture probe on the bottom, a glassy carbon (GC) working electrode on the top, and a buffered electrolyte containing the signaling probe conjugated with the CdS nanoparticle. When target DNA is not present in the chamber, the CdS-signaling probe is freely transported to the GC electrode where CdS accumulates during the preconcentration step and undergoes electrochemical anodic stripping voltammetry (ASV) that subsequently generates a current signal during the following oxidative stripping step. On the other hand, target DNA present in the sample undergoes simultaneous hybridization to both the capture and signaling probes in a sandwich-like manner. This phenomenon leads to fixation of the CdS nanoparticles on the bottom of the chamber, thus preventing their electrochemical reduction on the GC electrode. As a result, the electrochemical signal is reduced in the presence of target DNA. Based on the reduction of the current signal, target DNA from C. trachomatis was successfully detected without the need for any complicated secondary procedures. This electrochemical one-step detection method could serve as a conceptually new technology enabling highly convenient biosensing that is applicable to point-of-care testing (POCT).
  Biosensors & bioelectronics 04/2013; 42:603-607.
• Article: Indoor allergen assessment quantified by a thin-layer electrochemical cell and magnetic beads.

  Ryoji Kurita, Hiroyuki Yanagisawa, Osamu Niwa
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  ABSTRACT: We report the electrochemical determination of mite allergen in real house dust by using a thin layer electrochemical flow cell and magnetic beads. Der p1, which is an allergen from Dermatophagoides pteronyssinus, was immunochemically sandwiched between two dispersed monoclonal antibodies; one was modified on the surface of magnetic beads and the other was modified with alkaline phosphatase. After washing the beads, a small volume of p-aminophenol phosphate (p-APP) was added to produce p-aminophenol (p-AP). And then the p-AP concentration was measured electrochemically with a homemade electrochemical cell. The Der p1 assay was completed within 30min and a low detection limit of 0.3ng/mL was achieved. This is because the diffusion distance of Der p1 and the detection antibody was reduced to 22.3μm by using dispersed magnetic beads. Only 10min was required to complete the entire immunoreaction, and 54% of the Der p1 was confirmed to have immunoreacted in only 1min of mixing. Furthermore, the p-APP volume could be reduced using the thin-layer electrochemical flow cell. This is advantageous in terms of concentrating p-AP, and provides a high signal-to-noise ratio measurement in a short time. We achieved a high correlation (r=0.967, p<0.001) between our assay and a conventional enzyme-linked immunosorbent assay (ELISA) for real house dust measurements.
  Biosensors & bioelectronics 04/2013; 48C:43-48.
• Article: An electrochemiluminescence aptasensor for thrombin using graphene oxide to immobilize the aptamer and the intercalated [Formula: see text] probe.

  Xiao-Yan Wang, Ai Gao, Cong-Cong Lu, Xi-Wen He, Xue-Bo Yin
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  ABSTRACT: The immobilization of aptamer and the introduction of signal molecule are two keys for the development of electrochemiluminescence (ECL) aptasensor. Herein, the immobilization strategy with graphene oxide (GO) and a functional oligonucleotide (FO) are used to develop a sensitive aptasensor with the detection of thrombin as a model. After GO is attached on glass carbon or gold electrodes through physical adsorption, the amino-tagged aptamer is immobilized on the electrode surface via an amide linkage between the amino group at the end of aptamer and the carboxyl groups on GO. The FO is designed to contain two parts: the complementary strand and an intermolecular duplex for the intercalation of [Formula: see text] as ECL probe. The hybridization between aptamer and its complementary part at FO achieves the introduction of [Formula: see text] probe onto the electrode surface for high ECL emission. The hybrid between aptamer and thrombin leads to the release of FO containing the intercalated [Formula: see text] probe. Correspondingly, the decreased ECL emission is used to quantify thrombin. The concentration-dependent response of thrombin is observed between 0.90pM and 226pM with a detection limit of 0.40pM. While GO is used to immobilize the aptamer with various electrodes, such as glass carbon electrode and gold electrode in this work, GO can also preconcentrate TPrA on its surface to improve the sensitivity. The well-designed label-free ECL aptasensor strategy can be easily extended to other targets via the selection of their aptamers.
  Biosensors & bioelectronics 04/2013; 48C:120-125.
• Article: An aptamer based surface plasmon resonance biosensor for the detection of bovine catalase in milk.

  Jon Ashley, Sam F Y Li
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  ABSTRACT: In this research, we report the development of an aptamer based SPR biosensor for the detection of catalase in milk samples with minimal sample preparation. A biotin tagged aptamer was immobilized onto a gold surface by affinity capture. A limit of detection (LOD) in the nanomolar range (20.5nM, RSD: 15.2%) was found and a dynamic range of 15-1000nM was established for catalase in buffer and the aptamer showed good specificity toward catalase. This biosensor has the potential to be used in the detection of catalase in milk samples, a key indicator of mastitis disease in milk.
  Biosensors & bioelectronics 04/2013; 48C:126-131.
• Article: A double signal amplification platform for ultrasensitive and simultaneous detection of ascorbic acid, dopamine, uric acid and acetaminophen based on a nanocomposite of ferrocene thiolate stabilized Fe3O4@Au nanoparticles with graphene sheet.

  Meiling Liu, Qiong Chen, Cailang Lai, Youyu Zhang, Jianhui Deng, Haitao Li, Shouzhuo Yao
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  ABSTRACT: A double signal amplification platform for ultrasensitive and simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (AC) was fabricated by a nanocomposite of ferrocene thiolate stabilized Fe3O4@Au nanoparticles with graphene sheet. The platform was constructed by coating a newly synthesized phenylethynyl ferrocene thiolate (Fc-SAc) modified Fe3O4@Au NPs coupling with graphene sheet/chitosan (GS-chitosan) on a glassy carbon electrode (GCE) surface. The Fe3O4@Au-S-Fc/GS-chitosan modified GCE exhibits a synergistic catalytic and amplification effect toward AA, DA, UA and AC oxidation. The oxidation peak currents of the four compounds on the electrode were linearly dependent on AA, DA, UA and AC concentrations in the ranges of 4-400μM, 0.5-50μM, 1-300μM and 0.3-250μM in the individual detection of each component, respectively. By simultaneously changing the concentrations of AA, DA, UA and AC, their electrochemical oxidation peaks appeared at -0.03, 0.15, 0.24 and 0.35V, and good linear current responses were obtained in the concentration ranges of 6-350, 0.5-50, 1-90 and 0.4-32μM with the detection limits of 1, 0.1, 0.2 and 0.05μM (S/N=3), respectively.
  Biosensors & bioelectronics 04/2013; 48C:75-81.
• Article: DNA stabilized silver nanoclusters for ratiometric and visual detection of Hg(2+) and its immobilization in hydrogels.

  James L Maclean, Kiyoshi Morishita, Juewen Liu
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  ABSTRACT: DNA oligomers are particularly interesting templates for making silver nanoclusters (AgNCs) as different emission colors can be obtained by varying the DNA sequence. Many AgNCs have been used as Hg(2+) sensors since Hg(2+) induces fluorescence quenching. From an analytical chemistry standpoint, however, these 'light off' sensors are undesirable. In this work, taking advantage of the fact that some AgNCs are not as effectively quenched by Hg(2+), we design a sensor with AgNCs containing two emission peaks. The red peak is strongly quenched by Hg(2+) while the green peak shows a concomitant increase, producing an orange-to-green visual fluorescence transformation. Using this AgNC, we demonstrate ratiometric detection with a detection limit of 4nM Hg(2+). This sensor is further immobilized in a hydrogel matrix and this gel is also capable of detecting Hg(2+) with a visual response.
  Biosensors & bioelectronics 04/2013; 48C:82-86.
• Article: Perovskite LaTiO3-Ag0.2 nanomaterials for nonenzymatic glucose sensor with high performance.

  Yin-Zhu Wang, Hui Zhong, Xiao-Mo Li, Fei-Fei Jia, Yi-Xiang Shi, Wei-Guang Zhang, Zhi-Peng Cheng, Li-Li Zhang, Ji-Kui Wang
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  ABSTRACT: In this paper, a nonenzymatic glucose biosensor based on perovskite LaTiO3-Ag0.2(LTA) modified electrode was presented. The morphology and the composition of the perovskite LaTiO3-Ag0.2 nanomaterials were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. The LaTiO3-Ag0.2(LTA) composite was investigated by electrochemical characterization using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimal conditions, CV and chronoamperometry (I-t) study revealed that, compared with the bare glassy carbon electrode (GCE), the modified electrode showed a remarkable increase in the efficiency of the electrocatalytic oxidation of glucose, starting at around +0.70V (vs. Ag/AgCl). The prepared sensor exhibited a high sensitivity of 784.14µAmM(-1)cm(-2), a low detection limit of 2.1×10(-7)M and a wide linear range from 2.5µM to 4mM (R=0.9997). More importantly, the LTA modified electrode was also relatively insensitive to commonly interfering species such as ascorbic acid (AA), uric acid (UA), dopamine (DA) in high potential. Moreover, the nonenzymatic sensor was applied to the determination of glucose in human serum samples and the results were in good agreement with clinical data. Electrodes modified with perovskite nanomaterials are highly promising for nonenzymatic electrochemical detection of glucose because of their high sensitivity, fast response, excellent stability and good reproducibility.
  Biosensors & bioelectronics 04/2013; 48C:56-60.
• Article: Fabrication of a highly sensitive adenosine aptasensor based on covalent attachment of aptamer onto chitosan-carbon nanotubes-ionic liquid nanocomposite.

  Faezeh Shahdost-Fard, Abdollah Salimi, Ensiyeh Sharifi, Aazam Korani
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  ABSTRACT: The present study describes the fabrication of a novel electrochemical aptasensor for the label-free determination of adenosine. The immobilization surface is prepared by the modification of a glassy carbon (GC) electrode with a robust nanocomposite containing multiwalled carbon nanotubes, ionic liquid and chitosan(MWCNTs-IL-CHIT). Amine-terminated 12-mer capture probe(ssDNA1) is covalently attached onto the nanocomposite using glutaraldehyde (GA) as the linking agent, a 32-mer adenosine-specific aptamer (ssDNA2) immobilized onto the electrode surface through hybridization with the ssDNA1 and methylene blue (MB) used as the redox probe.The peak current of MB decreased linearly with increasing adenosine concentration due to the formation of aptamer-adenosine complex and displacement of the aptamer from the modified electrode surface.The aptasensor showed alow detection limit of 150pM and high sensitivity of 0.67μAnM(-1) at a concentration range of up to 0.4μM.Through the control experiments performed by using some other nucleosides such as guanosine, cytidine and uridine, the excellent specificity of this sensor toward adenosine detection is demonstrated. The potential applicability of the aptasensor is successfully applied for measuring adenosine concentration in blood serum and drug formulation samples.The herein described methodology may hold great promise for fabrication of other aptasensors and immunosensors.
  Biosensors & bioelectronics 04/2013; 48C:100-107.
• Article: Construction of near-infrared photonic crystal glucose-sensing materials for ratiometric sensing of glucose in tears.

  Yumei Hu, Xiaomei Jiang, Laiying Zhang, Jiao Fan, Weitai Wu
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  ABSTRACT: Noninvasive monitoring of glucose in tears is highly desirable in tight glucose control. The polymerized crystalline colloidal array (PCCA) that can be incorporated into contact lens represents one of the most promising materials for noninvasive monitoring of glucose in tears. However, low sensitivity and slow time response of the PCCA reported in previous arts has limited its clinical utility. This paper presents a new PCCA, denoted as NIR-PCCA, comprising a CCA of glucose-responsive sub-micrometered poly(styrene-co-acrylamide-co-3-acrylamidophenylboronic acid) microgels embedded within a slightly positive charged hydrogel matrix of poly(acrylamide-co-2-(dimethylamino)ethyl acrylate). This newly designed NIR-PCCA can reflect near-infrared (NIR) light, whose intensity (at 1722nm) would decrease evidently with increasing glucose concentration over the physiologically relevant range in tears. The lowest glucose concentration reliably detectable was as low as ca. 6.1μg/dL. The characteristic response time τsensing was 22.1±0.2s when adding glucose to 7.5mg/dL, and the higher the glucose concentration is, the faster the time response. Such a rationally designed NIR-PCCA is well suited for ratiometric NIR sensing of tear glucose under physiological conditions, thereby likely to bring this promising glucose-sensing material to the forefront of analytical devices for diabetes.
  Biosensors & bioelectronics 04/2013; 48C:94-99.
• Article: A sensitive electrochemical DNA biosensor for specific detection of Enterobacteriaceae bacteria by Exonuclease III-assisted signal amplification.

  Caihui Luo, Hua Tang, Wei Cheng, Li Yan, Decai Zhang, Huangxian Ju, Shijia Ding
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  ABSTRACT: A specific and sensitive methodology was developed successfully for quantitative detection of Enterobacteriaceae bacteria by integrating Exonuclease III-assisted target recycling amplification with a simple electrochemical DNA biosensor. After target DNA hybridizes with capture DNA, Exonuclease III can selectively digest the capture DNA, which releases the target to undergo a new hybridization and cleavage cycle on sensor surface, leading to a successful target recycling. Finally, the left capture DNA is recognized by detection probe to produce the detectable signal, which decreases with the increasing target DNA concentration. Under the optimal conditions, the proposed strategy could detect target DNA down to 8.7fM with a linear range from 0.01pM to 1nM, showing high sensitivity. Meanwhile, the sensing strategy was successfully used for detection of Enterobacteriaceae bacteria down to 40CFUmL(-1) in milk samples. This strategy presented a simple, rapid and sensitive platform for Enterobacteriaceae bacteria detection and would become a versatile and powerful tool for food safety, biothreat detection and environmental monitoring.
  Biosensors & bioelectronics 04/2013; 48C:132-137.
• Article: Ionic liquid functionalized graphene/Au nanocomposites and its application for electrochemical immunosensor.

  Na Liu, Xia Chen, Zhanfang Ma
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  ABSTRACT: In this work, a new nanocomposite, which was composed of ionic liquid functionalized graphene sheet (IL-GS) loaded gold nanoparticles (AuNPs), was prepared. The IL-GS was directly synthesized by the electrochemical exfoliation of graphite in ionic liquid (IL). Due to the modification of the IL, IL-GS can not only be dispersed easily in aqueous solution to form a homogeneous colloidal suspension of individual sheet, but also exhibits an improved conductivity. Meanwhile, the loaded AuNPs on the nanocomposites can increase the specific surface area to capture a large amount of antibodies as well as improve the capability of electron transfer. The IL-GS-Au nanocomposites were successfully employed for the fabrication of a facile and sensitive electrochemical immunosensor. Carcinoembryonic antigen (CEA) was used as a model protein. The proposed immunosensor exhibits a wide linear detection range (LDR) from 1fgmL(-1) to 100ngmL(-1), and an ultralow limit of detection (LOD) of 0.1fgmL(-1) (S/N=3). In addition, for the detection of clinical serum samples, it is well consistent with the data determined by the developed immunoassay and ELISA, indicating that the immunosensor provides a possible application for the detection of CEA in clinical diagnostics.
  Biosensors & bioelectronics 04/2013; 48C:33-38.
• Article: Aptamer-based sensing for thrombin in red region via fluorescence resonant energy transfer between NaYF4:Yb,Er upconversion nanoparticles and gold nanorods.

  Hongqi Chen, Fei Yuan, Shaozhen Wang, Juan Xu, Yiyan Zhang, Lun Wang
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  ABSTRACT: In this work, we design a FRET system for sensitive and selective determination of thrombin in red region, in which NaYF4:Yb,Er upconversion nanoparticles (UCNPs) act as donor and gold nanorods (Au NRs) act as acceptor. NaYF4:Yb,Er UCNPs with a strong emission at 661nm were successfully synthesized by tuning the doped ions ratio. Carboxyl-functionalized NaYF4:Yb,Er UCNPs and Au NRs were then prepared and conjugated with the thrombin aptamers, respectively. The fluorescence emission band of NaYF4:Yb,Er UCNPs (λmax=661nm) highly overlaps with the absorption band of Au NRs(λmax=666nm), which benefits from the large tunability of the spectrum band of Au NRs. A FRET system was then formed when thrombin was added to the mixture of NaYF4:Yb,Er UCNPs and Au NRs, which were both modified thrombin aptamers. The fluorescence quenching efficiency of NaYF4:Yb,Er UCNPs was increased in a thrombin concentration-dependent manner, which built the principle of thrombin quantification. The linear range was 2.5-90nM in an aqueous buffer, and 3.75-112.5nM in spiked human serum samples for thrombin. It also demonstrates a high selectivity to other biological species due to the specific binding. The measurement of thrombin in human plasma is satisfying, suggesting that the FRET system is of practical value in a complex biological sample matrix in red region.
  Biosensors & bioelectronics 04/2013; 48C:19-25.
• Article: Fluorosurfactant-capped gold nanoparticles-based label-free colorimetric assay for Au(3+) with tunable dynamic range via a redox strategy.

  Bin Yang, Xiao-Bing Zhang, Wei-Na Liu, Rong Hu, Weihong Tan, Guo-Li Shen, Ru-Qin Yu
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  ABSTRACT: Gold nanoparticles-based colorimetric assay possesses several unique advantages, and has been applied for a wide range of targets, varying from nucleic acids to different metal ions. However, due to the lack of proper coordinating ligand, gold nanoparticles-based colorimetric sensing system for Au(3+) has not been developed so far. It is well-known that Au(3+) could induce the oxidation transition of thiol compounds to disulfide compounds. In this article, for the first time we converted such thiol masking reaction into colorimetric sensing system for label-free detection of Au(3+) via a target-controlled aggregation of nanoparticles strategy. In the new proposed sensing system, fluorosurfactant-capped gold nanoparticles were chosen as signal reporter units, while an Au(3+)-triggered oxidation of cysteine (Cys), which inhibited the aggregation of gold nanoparticles, acted as the recognition unit. By varying the amount of Cys, a tunable response range accompanied with different windows of color change could be obtained for Au(3+), illustrating the universality of the sensing system for Au(3+) samples with different sensitivity requirements. Under optimized condition, the proposed sensing system exhibits a high sensitivity towards Au(3+) with a detection limit of 50nM, which is lower than previously reported spectroscopic methods. It has also been applied for detection of Au(3+) in practical water samples with satisfactory result.
  Biosensors & bioelectronics 04/2013; 48C:1-5.