World Congress on Biosensors 2014

World Congress on Biosensors 2014
Biosensors 2014

Wednesday, 9 May 2012


A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:

Neuroscience goes on a chip

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Aung K. Soe, Saeid Nahavandi, Khashayar Khoshmanesh
Advances in microelectronics, microfluidics, polymers and microfabrication have enabled the creation of disposable lab-on-a-chips (LOCs) as the new tools for neuroscience research. The LOCs have been applied for a wide range of neurobiology studies, including cellular and molecular biochemical experimentations, morphological observations and electrophysiological investigations. The integration of miniaturised components leads to analytical instrumentations with unprecedented automation, speed of analysis, and flexibility. These features make LOCs capable enough to replace their bulky and expensive bench-top counterparts. LOCs can be useful for genomic, proteomic, epigenomic, peptidomic, connectomic and electrophysiological studies and also as effective tools for reductionist neuroscientists. Moreover, they can be applied at higher level studies such as developmental neurobiology and behavioural investigations. This work provides an in-depth review of LOC platforms for neuroscience research. First, we review the essential bench-top neuroscience instrumentation as per their functions and features. Next, we present LOC counterparts for those bench-top instrumentations. Finally, we offer perspectives on persistent challenges and our perception of opportunities based on LOC instrumentations in neuroscience research.

Implantable enzyme amperometric biosensors

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Christian N. Kotanen, Francis Gabriel Moussy, Sandro Carrara, Anthony Guiseppi-Elie
The implantable enzyme amperometric biosensor continues as the dominant in vivo format for the detection, monitoring and reporting of biochemical analytes related to a wide range of pathologies. Widely used in animal studies, there is increasing emphasis on their use in diabetes care and management, the management of trauma-associated hemorrhage and in critical care monitoring by intensivists in the ICU. These frontier opportunities demand continuous indwelling performance for up to several years, well in excess of the currently approved seven days. This review outlines the many challenges to successful deployment of chronically implantable amperometric enzyme biosensors and emphasizes the emerging technological approaches in their continued development. The foreign body response plays a prominent role in implantable biotransducer failure. Topics considering the approaches to mitigate the inflammatory response, use of biomimetic chemistries, nanostructured topographies, drug eluting constructs, and tissue-to-device interface modulus matching are reviewed. Similarly, factors that influence biotransducer performance such as enzyme stability, substrate interference, mediator selection and calibration are reviewed. For the biosensor system, the opportunities and challenges of integration, guided by footprint requirements, the limitations of mixed signal electronics, and power requirements, has produced three systems approaches. The potential is great. However, integration along the multiple length scales needed to address fundamental issues and integration across the diverse disciplines needed to achieve success of these highly integrated systems, continues to be a challenge in the development and deployment of implantable amperometric enzyme biosensor systems.

A strategy for high-throughput screening of ligands suitable for molecular imprinting of proteins

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Stefan Eppler, Tim Schröder, Jürgen Friedle, Simone Michl, Werner Dangel, Boris Mizaikoff
For facilitating the identification of appropriate functionalities that may serve as a binding motif of functional monomers, a selection strategy based on high-throughput screening of the binding properties of readily available sorbent materials has been developed. Thereby, the affinity of such ligands to the protein of interest may be rapidly determined. From these studies, it is anticipated that ligand functionalities will be derived, which may lead to advanced selection and design of dedicated functional monomers suitable for decorating the surface of a scavenger material. Thus, specific binding of the target protein of interest should be enabled even in complex solutions such as e.g., biotechnologically relevant cell lysates. In the present contribution, an automated screening method for studying ligand interactions of selected sorbent materials with pepsin – a protein of the protease family – was developed. Aqueous buffer solutions containing pepsin at known constant concentration were pipetted through an array of miniaturized chromatographic solid phase extraction (SPE) columns containing a variety of sorbent materials, and the eluted solutions were analyzed by UV/vis spectroscopy. The established screening protocol was validated against resin materials of known interaction with pepsin. Finally, the developed screening strategy was adapted for a robot system enabling high-throughput screening for a wide variety of sorbent materials and ligand functionalities in a fully automated approach. The obtained results clearly indicate that the established screening routine provides valuable data for characterizing resin-immobilized ligands, and their affinity toward pepsin.

A host–guest-recognition-based electrochemical aptasensor for thrombin detection

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Hao Fan, Hui Li, Qingjiang Wang, Pingang He, Yuzhi Fang
A sensitive electrochemical aptasensor for thrombin detection is presented based on the host-guest recognition technique. In this sensing protocol, a 15 based thrombin aptamer (ab. TBA) was dually labeled with a thiol at its 3′ end and a 4-((4-(dimethylamino)phenyl)azo) benzoic acid (dabcyl) at its 5′ end, respectively, which was previously immobilized on one Au electrode surface by AuS bond and used as the thrombin probe during the protein sensing procedure. One special electrochemical marker was prepared by modifying CdS nanoparticle with β-cyclodextrins (ab. CdS-CDs), which employed as electrochemical signal provider and would conjunct with the thrombin probe modified electrode through the host–guest recognition of CDs to dabcyl. In the absence of thrombin, the probe adopted linear structure to conjunct with CdS-CDs. In present of thrombin, the TBA bond with thrombin and transformed into its special G-quarter structure, which forced CdS-CDs into the solution. Therefore, the target-TBA binding event can be sensitively transduced via detecting the electrochemical oxidation current signal of Cd of CdS nanoparticles in the solution. Using this method, as low as 4.6pM thrombin had been detected.

Piezoelectrically driven vertical cavity acoustic transducers for the convective transport and rapid detection of DNA and protein binding to DNA microarrays with SPR imaging—A parametric study

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Yuka Okabe, Yulin Chen, Rishi Purohit, Robert M. Corn, Abraham P. Lee
Mixing within the microdomain is limited because convective mixing cannot be achieved since diffusion dominates as the main form of transport. Hence microassays can take on the order of 1 to 72h, without the aid of a passive or active mixer to shorten the time of transport of a target molecule to a probe (Lai et al., 2004). Liu et al. (2002, 2003) developed a low cost cavitation microstreaming based mixer which is easy to implement and use, but no comprehensive study has been done to optimize such a mixer for various applications. We present a study of the effects of various frequencies and cavity parameters on mixing using dye and surface based assays with protein, DNA, and nanoparticles to obtain an optimum mixing frequency and configuration for a wide range of assay applications. We present a novel method to monitor real time binding using surface plasmon resonance imaging (SPRI) coupled with a vertical cavity acoustic transducer (VCAT) micromixer for various biomolecule surface assays. The combination of VCAT and SPRI allows assay signal saturation within one minute while conserving reagent volume. The kinetic rate constant for adsorption (k a) and desorption (k d) as well as the limit of detection (LOD) of 5nM for the DNA duplex formation are reported using this VCAT micromixer.

Label-free detection of bacterial RNA using polydiacetylene-based biochip

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Moo-Kyung Park, Kyung-Woo Kim, Dong June Ahn, Min-Kyu Oh
We developed a simple and effective polydiacetylene-based, label-free multiplex DNA chip for the detection of various pathogenic microorganisms. A novel immobilization method of PDA vesicles on glass slides was exploited using α-cyclodextrin (α-CD). The surface topography of the efficiently immobilized PDA vesicles was confirmed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Then, oligonucleotides complementary to rRNAs of three pathogenic bacteria were conjugated to the PDA vesicles. Finally, crude lysate of pathogenic bacteria was applied to the PDA biochip. The pathogenic bacteria were specifically detected by DNA–RNA hybridization in an hour. The new PDA sensor was effective in detecting multiple pathogenic bacteria easily and accurately without rigorous purification, amplification, and labeling of their genetic components.

An integrated microfluidic system for rapid screening of alpha-fetoprotein-specific aptamers

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Chao-Jyun Huang, Hsin-I. Lin, Shu-Chu Shiesh, Gwo-Bin Lee
The systematic evolution of ligands by exponential enrichment (SELEX) is a screening technique that involves the progressive selection of highly specific ligands via repeated rounds of partition and amplification from a large random pool of nucleic acid sequences. The products of this selection process are called aptamers and are either short single-stranded deoxyribonucleic acid (ssDNA) or ribonucleic acid (RNA) molecules with a high binding affinity to a large variety of target analytes. However, SELEX is a lengthy, labor-intensive, iterative process requiring multiple rounds of extraction and polymerase chain reaction (PCR) amplification. In order to address these problems, this study presents a new integrated microfluidic system consisting of a magnetic bead-based microfluidic SELEX chip and a competitive assay chip to automate the aptamer screening process. More importantly, the selected ssDNA sequences were confirmed to have a high affinity and specificity to the target molecules, using the developed competitive assay chip. With this approach, an aptamer specific to alpha-fetoprotein (AFP), which is a biomarker for liver cancers, has been successfully selected. The screened aptamer was used as a recognition molecule for AFP and has a linear detection range from 12.5 to 800ng/mL, which was suitable for rapid clinical applications.

Detection of estradiol at an electrochemical immunosensor with a Cu UPD|DTBP–Protein G scaffold

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Xiaoqiang Liu, Xinhai Wang, Jiamei Zhang, Heqing Feng, Xiuhua Liu, Danny K.Y. Wong
A copper monolayer was formed on a gold electrode surface via underpotential deposition (UPD) method to construct a Cu UPD|DTBP–Protein G immunosensor for the sensitive detection of 17β-estradiol. Copper UPD monolayer can minimize the non-specific adsorption of biological molecules on the immunosensor surface and enhance the binding efficiency between immunosensor surface and thiolated Protein G. The crosslinker DTBP (Dimethyl 3,3′-dithiobispropionimidate·2HCl) has strong ability to immobilize Protein G molecules on the electrode surface and the immobilized Protein G provides an orientation-controlled binding of antibodies. A monolayer of propanethiol was firstly self-assembled on the gold electrode surface, and a copper monolayer was deposited via UPD on the propanethiol modified electrode. Propanethiol monolayer helps to stabilize the copper monolayer by pushing the formation and stripping potentials of the copper UPD monolayer outside the potential range in which copper monolayer can be damaged easily by oxygen in air. A droplet DTBP–Protein G was then applied on the modified electrode surface followed by the immobilization of estradiol antibody. Finally, a competitive immunoassay was conducted between estradiol–BSA (bovine serum albumin) conjugate and free estradiol for the limited binding sites of estradiol antibody. Square wave voltammetry (SWV) was employed to monitor the electrochemical reduction current of ferrocenemethanol and the SWV current decreased with the increase of estradiol–BSA conjugate concentration at the immunosensor surface. Calibration of immunosensors in waste water samples spiked with 17β-estradiol yielded a linear response up to ∼2200pgmL−1, a sensitivity of 3.20μA/pgmL−1 and a detection limit of 12pgmL−1. The favorable characteristics of the immunosensors such as high selectivity, sensitivity and low detection limit can be attributed to the Cu UPD|DTBP–Protein G scaffold.

Layer-by-layer assembly of chemical reduced graphene and carbon nanotubes for sensitive electrochemical immunoassay

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Yan Liu, Yang Liu, Hongbin Feng, Yongmin Wu, Lokesh Joshi, Xiangqun Zeng, Jinghong Li
In this work, uniform and stable multi-walled carbon nanotubes (MWCT) and chemically reduced graphene (GR) composite electrode interface was fabricated by using layer-by-layer assembly method. The performances of these GR–MWCT assembled electrode interfaces were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). It was demonstrated that the assembled composite film significantly improved the interfacial electron transfer rate compared with that of GR or MWCT modified electrode. Based on the GR–MWCT assembled interface, a sandwich-type electrochemical immunosensor was constructed using human IgG as a model target. In this assay, human IgG was fixed as the target antigen, the HRP-conjugated IgG as the probing antibody and hydroquinone as the electron mediator. The detection limit of the immunosensor was 0.2ngmL−1 (signal-to-noise ratio of 3). A good linear relationship between the current signals and the concentrations of Human IgG was achieved from 1ngmL−1 to 500ngmL−1. Moreover, this electrochemical immunosensor exhibited excellent selectivity, stability and reproducibility, and can be used to accurately detect IgG concentration in human serum samples. The results suggest that the electrochemical immunosensor based on GR–MWCT assembled composite will be promising in the point-of-care diagnostics application of clinical screening of multiple diseases.

Comparison of three genetically modified Escherichia coli biosensor strains for amperometric tetracycline measurement

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Wenfeng Song, Neil Pasco, Ravi Gooneratne, Richard J. Weld
Three separate genetic strategies, based upon the induced expression of three different genes (lacZ, selA and nuoA) were tested to provide the SciTox assay with sensitive and specific detection of the antibiotic tetracycline (Tet). All three strategies relied on gene induction from the Tn10 tetA promoter. Both lacZ and nuoA biosensors responded specifically and sensitively to sub-inhibitory concentrations of Tet. However, the selA-based assay was not sensitive enough to detect Tet in the SciTox assay. The detection limits for Tet of the lacZ and nuoA biosensor strains were 0.11μgml−1 and 0.0026μgml−1, respectively, and their linear ranges were 0.1–1μgml−1 and 0–0.01μgml−1, respectively. While lacZ has previously been used as a reporter gene in an amperometric bioassay, nuoA is a novel and more sensitive reporter gene. This is the first report in which a respiratory gene was used as a reporter gene in an amperometric biosensor. The results indicate that this approach can produce a highly sensitive detection system. In order to test whether the new system could be used to detect other chemicals, the nuoA gene was re-engineered to be driven by the copper-inducible copA promoter. Using this strain, the SciTox assay was found to be able to specifically detect copper and silver ions.

Electrocatalytic oxidation and voltammetric determination of levodopa in the presence of carbidopa at the surface of a nanostructure based electrochemical sensor

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Mohammad Mazloum-Ardakani, Zahra Taleat, Alireza Khoshroo, Hadi Beitollahi, Hossein Dehghani
In the present paper, the use of a carbon paste electrode modified by meso-tetrakis(3-methylphenyl) cobalt porphyrin (CP) and TiO2 nanoparticles for the determination of levodopa (LD) and carbidopa (CD) was described. Initially, cyclic voltammetry was used to investigate the redox properties of this modified electrode at various scan rates. Next, the mediated oxidation of LD at the modified electrode was described. At the optimum pH of 7.0, the oxidation of LD occurs at a potential about 150mV less positive than that of an unmodified carbon paste electrode. Based on differential pulse voltammetry (DPV), the oxidation of LD exhibited a dynamic range between 0.1 and 100.0μM and a detection limit (3σ) of 69±2nM. DPV was used for simultaneous determination of LD and CD at the modified electrode, and quantitation of LD and CD in some real samples (such as tablets of Parkin-C Fort and Madopar, water, urine, and human blood serum) by the standard addition method.

Ultrasensitive detection of adrenocorticotropin hormone (ACTH) using disposable phenylboronic-modified electrochemical immunosensors

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
María Moreno-Guzmán, Irene Ojeda, Reynaldo Villalonga, Araceli González-Cortés, Paloma Yáñez-Sedeño, José M. Pingarrón
This work reports for the first time an electrochemical immunosensor for the determination of adrenocorticotropin hormone (ACTH). The immunoelectrode design involves the use of amino phenylboronic acid for the oriented immobilization of anti-ACTH antibodies onto screen-printed carbon modified electrode surfaces. A competitive immunoassay between the antigen and the biotinylated hormone for the binding sites of the immobilized antibody was performed. The electroanalytical response was generated by using alkaline phosphatase-labelled streptavidin and 1-naphtyl phosphate as the enzyme substrate. The electrochemical oxidation of the enzyme reaction product, 1-naphtol, measured by differential pulse voltammetry was employed to monitor the affinity reaction. Under the optimized working conditions, an extremely low detection limit of 18pg/L was obtained. Cross-reactivity was evaluated against other hormones (cortisol, estradiol, testosterone, progesterone, hGH and prolactin) and the obtained results demonstrated an excellent selectivity. The developed immunosensor was applied to a human serum sample containing a certified amount of ACTH with good results.

Development of real-time assays for impedance-based detection of microbial double-stranded DNA targets: Optimization and data analysis

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Andrei L. Ghindilis, Maria W. Smith, Dean S. Messing, Vena N. Haynes, George B. Middleton, Kevin R. Schwarzkopf, Carmen E. Campbell, Changqing Zhan, Bruce Ulrich, Michael J. Frasier, Paul J. Schuele, David R. Evans, Ibrahim Sezan, John W. Hartzell, Holly M. Simon
A real-time, label free assay was developed for microbial detection, utilizing double-stranded DNA targets and employing the next generation of an impedimetric sensor array platform designed by Sharp Laboratories of America (SLA). Real-time curves of the impedimetric signal response were obtained at fixed frequency and voltage for target binding to oligonucleotide probes attached to the sensor array surface. Kinetic parameters of these curves were analyzed by the integrated data analysis package for signal quantification. Non-specific binding presented a major challenge for assay development, and required assay optimization. For this, differences were maximized between binding curve kinetic parameters for probes binding to complementary targets versus non-target controls. Variables manipulated for assay optimization included target concentration, hybridization temperature, buffer concentration, and the use of surfactants. Our results showed that (i) different target–probe combinations required optimization of specific sets of variables; (ii) for each assay condition, the optimum range was relatively narrow, and had to be determined empirically; and (iii) outside of the optimum range, the assay could not distinguish between specific and non-specific binding. For each target–probe combination evaluated, conditions resulting in good separation between specific and non-specific binding signals were established, generating high confidence in the SLA impedimetric dsDNA assay results.

Impact of immobilization support on colorimetric microarrays performances

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Gaelle C. Le Goff, Benjamin P. Corgier, Céline A. Mandon, Gabriel De Crozals, Carole Chaix, Loïc J. Blum, Christophe A. Marquette
We report here a comparison of support materials for colorimetric hybridization assays on microarrays. Four surfaces with various chemistries and architectures (roughness and porosity) were evaluated: (i) bare and (ii) activated polystyrene surfaces classically used for ELISA; (iii) a double-sided adhesive support; and (iv) a porous nitrocellulose/cellulose acetate membrane. Each substrate was functionalized with a microarray of probes and subjected to an enzymatic colorimetric DNA hybridization test. Tests were carried out in a 96-well assembly suitable for automated high-throughput analysis. Colorimetry results, microscopy observations and a chemiluminescence study showed that the test efficiency not only depends on the surface probe density but that the capacity of the material to retain the colored enzymatic product is also a critical parameter. All parameters being considered, the adhesive coated surface proposes the best surface properties for efficient colorimetric microarrays.

Bioactivity of horseradish peroxidase entrapped in silica nanospheres

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Xiaodong Cao, Jiachao Yu, Zhiqiang Zhang, Songqin Liu
Interest in the fabrication of micro/nanoreactors for evaluation of the function of biomolecules in biological processes, enzymatic reaction kinetics occurring inside the nanospace is rapidly increasing. With a simple reverse-micelle microemulsion method, horseradish peroxidase (HRP), a model biomolecule, was herein skillfully confined in silica nanoshells (HRP@SiO2) and its biocatalytical behaviors were investigated in detail. Spectroscopic measurements showed that the entrapped HRP molecules retained their native structure and had high enzymatic activity toward 3,3′,5,5′-tetramethylbenzidine (TMB) with Michaelis constant (K m) of 3.02×10−5 molL−1. The entrapped HRP displayed a good direct electron transfer behavior and sensitive electrocatalytic response toward the reduction of H2O2, which could be enhanced using thionine and o-phenylenediamine (o-PD) as electron mediators. When using thionine as mediator, the mass transport between the substrates in electrolyte and HRP confined in silica nanospheres through the mesoporous tunnels was slower than that of o-PD, which slowed down the electron transfer between heme in HRP in the confined nanospace and the electrode, and resulted in low sensitivity to H2O2 with thionine as mediator when compared to o-PD.

Electrically contacted enzyme based on dual hairpin DNA structure and its application for amplified detection of Hg2+

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Guangfeng Wang, Hao Huang, Xiaojun Zhang, Lun Wang
In the present study, based on a dual hairpin DNA structure, a novel system of electrically contacted enzyme and its signal amplification for ultrasensitive detection of Hg2+ was demonstrated. In the presence of Hg2+, with the interaction of thymine–Hg2+–thymine (T–Hg2+–T), DNA sequence dully labeled with ferrocene (Fc) at 5′ end and horseradish peroxidase (HRP) at 3′ end, hybridized to the capture probe and formed the dual hairpin structure on the electrode. Fc unit acts as a relay that electrically contacts HRP with the electrode and activates the bioelectrocatalyzed reduction of H2O2. And based on the bioelectrocatalyzed signal amplification of the presented system, Hg2+ could be quantitatively detected in the range of 10−10–10−6 M with a low detection limit of 52pM. And it also demonstrated excellent selectivity against other interferential metal ions.

A nano-sized Au electrode fabricated using lithographic technology for electrochemical detection of dopamine

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Yue Zhao, Shu-Hong Li, Jian Chu, You-Peng Chen, Wen-Wei Li, Han-Qing Yu, Gang Liu, Yang-Chao Tian, Ying Xiong
One big challenge of fabricating nanosensors for spatially resolved electrochemical detection of neurochemicals, such as dopamine (DA), is the difficulty to assembly nanometer-scale patternable and integrated sensors. In this work we develop a novel approach to precisely manufacture nano-Au-electrode (NAE) using lithographic fabrication technique, and characterize the NAE for DA detection. A negative photoresist, SU-8, is used as a substrate and protection layer for the 127-nm Au active sensing layer. The cross surface morphology and thickness of the Au layer are imaged by scanning electron microscopy and an interference microscopy. This NAE could be precisely controlled, repeatedly fabricated and conveniently renewed for several times. The electrochemical sensitivity and selectivity of the NAE towards DA detection are significantly higher than those of a standard Au thin-film electrode. This work demonstrates that the NAE could be used as an attractive means for electrochemically sensing and recording DA.

A G-quadruplex based label-free fluorescent biosensor for lead ion

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Liangqia Guo, Dandan Nie, Chunyan Qiu, Qishan Zheng, Haiyan Wu, Peirong Ye, Yanli Hao, FengFu Fu, Guonan Chen
Many Pb2+ biosensors based on Pb2+-specific RNA-cleaving DNAzyme have been developed in the past years. However, many of them have limited practical use because of high cost (e.g., enzymes), complicated processing and the use of unstable molecules (e.g., RNA). In this study, a novel label-free fluorescent biosensor for Pb2+ was proposed based on Pb2+-induced allosteric G-quadruplex (PS2.M). In the presence of K+, N-methyl mesoporphyrin IX (NMM) could bind to K+-stabilized G-quadruplexes, giving rise to high fluorescence. On addition of Pb2+, Pb2+ competitively binded to K+-stabilized G-quadruplexes to form more compact DNA folds. The Pb2+-stabilized G-quadruplexes did not bind to NMM, which resulted in fluorescence decrease. This allowed us to utilize PS2.M for quantitative analysis of Pb2+ using the NMM–G-quadruplex system by convenient “mix-and-detect” protocol. The fluorescence emission ratio (F 0/F) showed a good linear response toward Pb2+ over the range from 5.0nM to 1.0μM with a limit of detection of 1.0nM. This proposed biosensor was simple and cost efficiency in design and in operation with high sensitivity and selectivity. We validated the practicality of this biosensor for the determination of Pb2+ in lake water samples.

A study of electrochemical biosensor for analysis of three-dimensional (3D) cell culture

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Se Hoon Jeong, Dong Woo Lee, Sanghyo Kim, Jhingook Kim, Bosung Ku
Cell culture has a fundamental role not only in regenerative medicine but also in biotechnology, pharmacology, impacting both drug discovery and manufacturing. Although cell culture has been generally developed for only two-dimensional (2D) culture systems, three-dimensional (3D) culture is being spotlighted as the means to mimic in vivo cellular conditions. In this study, a method for cytotoxicity assay using an electrochemical biosensor applying 3D cell culture is presented. In order to strengthen the advantage of a 3D cell culture, the experimental condition of gelation between several types of sol–gels (alginate, collagen, matrigel) and cancer cells can be optimized to make a 3D cell structure on the electrode, which will show the reproducibility of electrical measurement for long-term monitoring. Moreover, cytotoxicity test results applying this method showed IC50 value of A549 lung cancer cells to erlotinib. Thus, this study evaluates the feasibility of application of the electrochemical biosensor for 3D cell culture to cytotoxicity assay for investigation of 3D cell response to drug compounds.

TiO2/MWNTs nanocomposites-based electrochemical strategy for label-free assay of casein kinase II activity and inhibition

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Xiaoxiao He, Zhifeng Chen, Yonghong Wang, Kemin Wang, Jing Su, Genping Yan
In this paper, a novel label-free electrochemical strategy has been developed for assay of casein kinase II (CK2) activity and inhibition using TiO2/MWNTs nanocomposites. This detection system takes advantage of specific binding of the phosphate groups with TiO2 nanoparticles and fast electron transfer rate of MWNTs. In this strategy, the synthesized TiO2/MWNTs nanocomposite was firstly deposited on the surface of a glassy carbon electrode (GCE). The presence of MWNTs not only increased the surface area of the electrode but also promoted electron-transfer reaction. In the presence of CK2, the kinase reaction resulted in the phosphorylation of peptide substrates. The phosphorylated peptides were subsequently captured to the surface of GCE modified with TiO2/MWNTs nanocomposite through specific binding of the phosphate groups with TiO2 nanoparticles. Then the access of redox probe [Fe(CN)6]3−/4− to electrode surface was blocked. As a result, the decrease peak currents were related to the concentrations of the CK2, providing a sensing mechanism for monitoring peptides phosphorylation. The electrochemical strategy can be employed to assay CK2 activity with a low detection limit of 0.07U/mL. The linear range of the assay for CK2 was 0–0.5U/mL. Furthermore, the interferences experiments of PKA and inhibition of CK2 have been also studied by using this strategy.

Bilirubin oxidase from Bacillus pumilus: A promising enzyme for the elaboration of efficient cathodes in biofuel cells

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Fabien Durand, Christian Hauge Kjaergaard, Emmanuel Suraniti, Sébastien Gounel, Ryan G. Hadt, Edward I. Solomon, Nicolas Mano
A CotA multicopper oxidase (MCO) from Bacillus pumilus, previously identified as a laccase, has been studied and characterized as a new bacterial bilirubin oxidase (BOD). The 59kDa protein containing four coppers, was successfully over-expressed in Escherichia coli and purified to homogeneity in one step. This 509 amino-acid enzyme, having 67% and 26% sequence identity with CotA from Bacillus subtilis and BOD from Myrothecium verrucaria, respectively, shows higher turnover activity towards bilirubin compared to other bacterial MCOs. The current density for O2 reduction, when immobilized in a redox hydrogel, is only 12% smaller than the current obtained with Trachyderma tsunodae BOD. Under continuous electrocatalysis, an electrode modified with the new BOD is more stable, and has a higher tolerance towards NaCl, than a T. tsunodae BOD modified electrode. This makes BOD from B. pumilus an attractive new candidate for application in biofuel cells (BFCs) and biosensors.

An enzymatic immunoassay microfluidics integrated with membrane valves for microsphere retention and reagent mixing

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Li Ren, Jian-Chun Wang, Wenming Liu, Qin Tu, Rui Liu, Xueqin Wang, Juan Xu, Yaolei Wang, Yanrong Zhang, Li Li, Jinyi Wang
The present study presents a new microfluidic device integrated with pneumatic microvalves and a membrane mixer for enzyme-based immunoassay of acute myocardial infarction (AMI) biomarkers, namely, myoglobin, and heart-type fatty acid binding protein (H-FABP). Superparamagnetic microspheres with carboxyl groups on their surfaces were used as antibody solid carriers. A membrane mixer consisting of four ψ-type membrane valves was assembled under the reaction chamber for on-chip performing microsphere trapping and reagent mixing. The entire immunoassay process, including microsphere capture, reagent input, mixing, and subsequent reaction, was accomplished on the device either automatically or manually. The post-reaction substrate resultant was analyzed using a microplate reader. The results show that the average absorbance value is correlated with the concentration of cardiac markers, in agreement with the results obtained using a conventional microsphere-based immunoassay; this indicated that the proposed on-chip immunoassay protocol could be used to detect both myoglobin and H-FABP. The minimum detectable concentration is 5ng/mL for myoglobin and 1ng/mL for H-FABP.

Small-size biofuel cell on paper

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Lingling Zhang, Ming Zhou, Dan Wen, Lu Bai, Baohua Lou, Shaojun Dong
In this work, we demonstrated a novel paper-based mediator-less and compartment-less biofuel cell (BFC) with small size (1.5cm×1.5cm). Ionic liquid functionalized carbon nanotubes (CNTs-IL) nanocomposite was used as support for both stably confining the anodic biocatalyst (i.e., NAD+-dependent glucose dehydrogenase, GDH) for glucose electrooxidation and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., bilirubin oxidase, BOD) for O2 electroreduction. Such BFC provided a simple approach to fabricate low-cost and portable power devices on small-size paper, which can harvest energy from a wide range of commercial beverages containing glucose (e.g., Nescafe instant coffee, Maidong vitamin water, Watermelon fresh juice, and Minute Maid grape juice). These made the low-cost paper-based biodevice potential for broad energy applications.

A novel approach to determining the affinity of protein–carbohydrate interactions employing adherent cancer cells grown on a biosensor surface

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Diluka Peiris, Anatoliy Markiv, G. Paul Curley, Miriam V. Dwek
The development of biological agents for the treatment of solid tumours is an area of considerable activity. We are pursuing carbohydrate-binding proteins (lectins) in a strategy aimed at targeting cancer-associated changes in glycosylation. To evaluate lectin–cancer cell interactions we developed a novel cell biosensor in which binding events take place at the cell surface, more closely mimicking an in vivo system. Metastatic, SW620, and non-metastatic, SW480, colorectal cancer cells were grown on the surface of a tissue-culture compatible polystyrene coated biosensor chip and housed in a quartz crystal microbalance (QCM) apparatus, the kinetics of binding of a diverse range of lectins was evaluated. The lectin Helix pomatia agglutinin (HPA) has been shown to bind aggressive metastatic cancer and was produced in recombinant form (His- and RFP-tagged). The affinity of HPA was in the nanomolar range to the metastatic SW620 cells but was only in the micromolar range to the non-metastatic SW480. Overall, the dissociation constant (K D ) of the lectins tested in the new cell biosensor system was an order of magnitude lower (nanomolar range) than has generally been reported with systems such as QCM/SPR. This new cell-biosensor enables molecular interactions to be studied in a more relevant environment. An intrinsic problem with developing new biological therapies is the difficulty in determining the affinity with which proteins will interact with intact cell surfaces. This methodology will be of interest to researchers developing new biological approaches for targeting cell surfaces in a wide range of diseases, including cancer.

Label-free reflectometric interference microchip biosensor based on nanoporous alumina for detection of circulating tumour cells

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Tushar Kumeria, Mahaveer D. Kurkuri, Kerrilyn R. Diener, Luke Parkinson, Dusan Losic
In this report, a label-free reflectometric interference spectroscopy (RIfS) based microchip biosensor for the detection of circulating tumour cells (CTCs) is demonstrated. Highly ordered nanoporous anodic aluminium oxide (AAO) fabricated by electrochemical anodization of aluminium foil was used as the RIfS sensing platform. Biotinylated anti-EpCAM antibody that specifically binds to human cancer cells of epithelial origin such as pancreatic cancer cells (PANC-1) was covalently attached to the AAO surface through multiple surface functionalization steps. Whole blood or phosphate buffer saline spiked with low numbers of pancreatic cancer cells were successfully detected by specially designed microfluidic device incorporating an AAO RIfS sensor, without labour intensive fluorescence labelling and/or pre-enhancement process. Our results show that the developed device is capable of selectively detecting of cancer cells, within a concentrations range of 1000–100,000cells/mL, with a detection limit of <1000cells/mL, a response time of <5min and sample volume of 50μL of. The presented RIfS method shows considerable promise for translation to a rapid and cost-effective point-of-care diagnostic device for the detection of CTCs in patients with metastatic cancer.

Functional protease assay using liquid crystals as a signal reporter

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Chih-Hsin Chen, Kun-Lin Yang
We report a functional protease assay in which liquid crystals (LCs) are used as signal reporters to transduce the test results into optical signals. In this assay, an oligopeptide substrate (CLSELDDRADALQAGASQFESSAAKLKRKYWWKNLK) is used as a probe. This oligopeptide can be cleaved by α-chymotrypsin at multiple locations and become smaller fragments after the cleavage. When the original oligopeptide is immobilized on a solid surface, its long flexible oligopeptide chain is able to influence the orientation of a thin layer of LC supported on the surface, as is evident as a bright spot on the surface. In contrast, when the shorter oligopeptide fragments are immobilized on the same surface, their shorter, less flexible chains cannot disrupt the orientation of LC, and a dark spot is observed. On the basis of the dark or bright signal from LC, α-chymotrypsin in buffer solution or complex media such as chicken broth can be detected by using the naked eye. However, when the incubation time is 3h, the limit of detection (LOD) for α-chymotrypsin in buffer solution is 50ng/mL, whereas that in chicken broth is only 500ng/mL. Unlike traditional antibody-based assays which show little difference between active and inactive α-chymotrypsin, only active protease can be detected in this assay. This study shows the potential utility of LCs for detecting functional proteases with good specificity and sensitivity.

Investigation of DNA damage treated with perfluorooctane sulfonate (PFOS) on ZrO2/DDAB active nano-order film

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Liping Lu, Laihui Xu, Tianfang Kang, Shuiyuan Cheng
The interactions between DNA and small molecules with planar heterocyclic structure were indicated in previous researches. This study investigated the interactions between PFOS with linear chain structure and DNA. A new phenomenon of DNA damage due to PFOS using electrochemistry technique was proved. The data was obtained on a modified glassy carbon electrode, on which didodecyldimethylammonium bromide (DDAB), ZrO2 and calf thymus DNA were immobilized layer-by-layer. Electrochemical response of DNA damage caused by PFOS was detected by differential pulse voltammetry (DPV) using methylene blue (MB) as electro-active indicator. The current of MB attenuated obviously after DNA/ZrO2/DDAB/GCE were incubated in PFOS. The shift of MB reduction peak potential indicates that PFOS is bound with DNA in groove probably by the first step of hydrophobic interaction and then the second step of intercalation into the base of DNA. X-ray photoelectron spectroscopic (XPS) was used to elucidate in detail the intercalation of PFOS into DNA and the formation of hydrogen bond between PFOS and DNA base. Electrochemical quartz crystal microbalance (EQCM) proved the formation of adducts of DNA and PFOS. Moreover, electrochemical impedance spectroscopy (EIS) indicates that the PFOS influence DNA structure and attenuate DNA charge transport. These results demonstrate that PFOS intercalated into DNA do induce DNA base damage.

Anti-epithelial cell adhesion molecule monoclonal antibody conjugated fluorescent nanoparticle biosensor for sensitive detection of colon cancer cells

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Liang Tao, Kui Zhang, Yuanjie Sun, Boquan Jin, Zhujun Zhang, Kun Yang
In this paper, a sensitive and selective sensor for detecting colon cancer cells based on nanoparticle covalent modified anti-human epithelial cell adhesion molecule (EpCAM) antibody is developed. The transmission electron microscope (TEM) images showed that the nanoparticle and functionalized nanoparticle had good decentrality for application. The NaIO4 oxidation method, which was used as oxidizing antibody for immobilization of conjugating antibody on the silica-coated fluorescent nanoparticles, maintained the activities of antibodies very well. The fluorescence microscopy imaging and flow cytometer (FCM) experiments demonstrated that the nanosensor could increase the signal intensity obviously and distinguish three kinds of target cells (colo205, sw480 and NCM460) well. The membrane and nuclear staining showed the distribution and abundance of EpCAM in cells’ membrane. It also provides a possibility to quantify special membrane proteins on different regions of cells’ surface. At the end, the result of detecting a simple sample proved that colo205 cells were selected by anti-EpCAM antibody nanosensors in this environment, and made a good foundation for subsequent research.

Nanographene-based tyrosinase biosensor for rapid detection of bisphenol A

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Lidong Wu, Dehui Deng, Jing Jin, Xianbo Lu, Jiping Chen
Hydrophilic nanographene (NGP) prepared by ball milling of graphite was used as the support to construct a novel tyrosinase biosensor for determination of bisphenol A (BPA). The performances of the nanographene-based tyrosinase biosensor were systematically compared with those of multiwall carbon nanotubes (MWNTs) modified tyrosinase biosensors. The results indicated that the nanographene-based tyrosinase biosensor provided significant advantages over MWNTs-based tyrosinase biosensor in term of response, repeatability, background current and limit of detection (LOD), which could be attributed to its larger specific surface area and unique hierarchical tyrosinase-NGP nanostructures. The nanographene-based tyrosinase biosensor displayed superior analytical performance over a linear range from 100nmolL−1 to 2000nmolL−1, with LOD of 33nmolL−1 and sensitivity of 3108.4mAcm−2 M−1. The biosensor was further used for detecting BPA (leaching from different vessels) in tap water, and the accuracy of the results was validated by high performance liquid chromatography (HPLC). The nanographene-based tyrosinase biosensor proved to be a promising and reliable tool for rapid detection of BPA leached from polycarbonate plastic products and for on-site rapid analysis of emergency pollution affairs of BPA.

Real-time analysis of the carbohydrates on cell surfaces using a QCM biosensor: a lectin-based approach

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Zhichao Pei, Julien Saint-Guirons, Camilla Käck, Björn Ingemarsson, Teodor Aastrup
A novel approach to the study of molecular interactions on the surface of mammalian cells using a QCM biosensor was developed. For this study, an epidermoid carcinoma cell line (A-431) and a breast adenocarcinoma cell line (MDA-MB-468) were immobilized onto polystyrene-coated quartz crystals. The binding and dissociation between the lectin Con A and the cells as well as the inhibition of the binding by monosaccharides were monitored in real time and provided an insight into the complex avidic recognition of cell glycoconjugates. The real-time lectin screening of a range of lectins, including Con A, DBA, PNA and UEA-I, enabled the accurate study of the glycosylation changes between cells, such as changes associated with cancer progression and development. Furthermore, the kinetic parameters of the interaction of Con A with MDA-MB-468 cells were studied. This application provides investigators in the field of glycobiology with a novel tool to study cell surface glycosylation and may also have impacts on drug discovery.

Quantitative biomolecular sensing station based on magnetoresistive patterned arrays

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
D. Serrate, J.M. De Teresa, C. Marquina, J. Marzo, D. Saurel, F.A. Cardoso, S. Cardoso, P.P. Freitas, M.R. Ibarra
The combination of magnetoresistive sensors and magnetic labeling of bioanalytes, which are selectively captured by their complementary antibody in the proximity of the sensor is a powerful method in order to attain truly quantitative immunological assays. In this paper we present a technical solution to exploit the existing spin valve technology to readout magnetic signals of bio-functionalized magnetic nanoparticles. The method is simple and reliable, and it is based on a discrete scan of lateral flow strips with a precise control of the contact force between sensor and sample. It is shown that the signal of the sensor is proportional to the local magnetization produced by the nanoparticles in a wide range of concentrations, and the sensitivity thresholds in both calibration samples and real immunorecognition assays of human chorionic gonadotropin hormone are well below the visual inspection limit (5.5ng/ml). Furthermore the sample scanning approach and the reduced dimensions of the sensors provide unprecedented spatial resolution of the nanoparticle distribution across the supporting nitrocellulose strip, therefore enabling on-stick control references and multi-analyte capability.

Optical diagnosis of laryngeal cancer using high wavenumber Raman spectroscopy

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Kan Lin, David Lau Pang Cheng, Zhiwei Huang
We report the implementation of the transnasal image-guided high wavenumber (HW) Raman spectroscopy to differentiate tumor from normal laryngeal tissue at endoscopy. A rapid-acquisition Raman spectroscopy system coupled with a miniaturized fiber-optic Raman probe was utilized to realize real-time HW Raman (2800–3020cm−1) measurements in the larynx. A total of 94 HW Raman spectra (22 normal sites, 72 tumor sites) were acquired from 39 patients who underwent laryngoscopic screening. Significant differences in Raman intensities of prominent Raman bands at 2845, 2880 and 2920cm−1 (CH2 stretching of lipids), and 2940cm−1 (CH3 stretching of proteins) were observed between normal and cancer laryngeal tissue. The diagnostic algorithms based on principal components analysis (PCA) and linear discriminant analysis (LDA) together with the leave-one subject-out, cross-validation method on HW Raman spectra yielded a diagnostic sensitivity of 90.3% (65/72) and specificity of 90.9% (20/22) for laryngeal cancer identification. This study demonstrates that HW Raman spectroscopy has the potential for the noninvasive, real-time diagnosis and detection of laryngeal cancer at the molecular level.

Multiplexed detection of cardiac biomarkers in serum with nanowire arrays using readout ASIC

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Guo-Jun Zhang, Kevin Tshun Chuan Chai, Henry Zhan Hong Luo, Joon Min Huang, Ignatius Guang Kai Tay, Andy Eu-Jin Lim, Minkyu Je
Early detection of cardiac biomarkers for diagnosis of heart attack is the key to saving lives. Conventional method of detection like the enzyme-linked immunosorbent assay (ELISA) is time consuming and low in sensitivity. Here, we present a label-free detection system consisting of an array of silicon nanowire sensors and an interface readout application specific integrated circuit (ASIC). This system provides a rapid solution that is highly sensitive and is able to perform direct simultaneous-multiplexed detection of cardiac biomarkers in serum. Nanowire sensor arrays were demonstrated to have the required selectivity and sensitivity to perform multiplexed detection of 100fg/ml troponin T, creatine kinase MM, and creatine kinase MB in serum. A good correlation between measurements from a probe station and the readout ASIC was obtained. Our detection system is expected to address the existing limitations in cardiac health management that are currently imposed by the conventional testing platform, and opens up possibilities in the development of a miniaturized device for point-of-care diagnostic applications.

Detection of p53 gene point mutation using sequence-specific molecularly imprinted PoPD electrode

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Ashutosh Tiwari, Swapneel R. Deshpande, Hisatoshi Kobayashi, Anthony P.F. Turner
An amperometric sequence-specific molecularly imprinted single-stranded oligodeoxyribonucleotide (ss-ODN) biosensor was fabricated and characterised in this study. Using ss-ODN as the template and o-phenylenediamine as the functional monomer, the ODN biosensor was fabricated by an electropolymerisation process on an indium-tin oxide (ITO) coated glass substrate. The template ss-ODN was washed out of the ss-ODN/poly(o-phenylenediamine)(PoPD)/ITO electrode using sterilised basic ethanol-water. The resulting ss-ODN imprinted PoPD/ITO electrode was characterised using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The amperometric responses, i.e., Δi as a function of the target ss-ODN concentration was studied. The biosensor using ss-ODN imprinted PoPD/ITO as the working electrode showed a linear Δ current response to the target ss-ODN concentration within the range of 0.01–300fM. The biosensor showed a sensitivity of 0.62μA/fM, with a response time of 14s. The present novel molecularly imprinted ss-ODN biosensor could greatly benefit in terms of cost-effectiveness, storage stability, ultra sensitivity and selectivity together with the potential for improved commercial genetic sensors.

Sensitive immobilization-free electrochemical DNA sensor based on isothermal circular strand displacement polymerization reaction

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Feng Xuan, Xiaoteng Luo, I-Ming Hsing
A highly sensitive electrochemical DNA sensor that requires no probe immobilization has been developed based on a target recycling mechanism utilizing a DNA polymerase with a strand displacement activity. The electrochemical detection is realized by taking advantage of the difference in diffusivity between a free ferrocene-labeled peptide nucleic acid (Fc-PNA) and a Fc-PNA hybridized with a complementary DNA, while the DNA polymerase-assisted target recycling leads to signal generation and amplification. The hybridization of the target DNA opens up a stem-loop template DNA with the Fc-PNA hybridized to its extruded 5′ end and allows a DNA primer to anneal and be extended by the DNA polymerase, which results in sequential displacement of the target DNA and the Fc-PNA from the template DNA. The displaced target DNA will hybridize with another template DNA, triggering another round of primer extension and strand displacement. The released Fc-PNA, due to its neutral backbone, has much higher diffusivity towards a negatively charged electrode, compared to that when it is hybridized with a negatively charged DNA. Therefore, a significantly enhanced signal of Fc can be observed. The outstanding sensitivity and simplicity make this approach a promising candidate for next-generation electrochemical DNA sensing technologies.

Biofunctionalization of nanoparticle assisted mass spectrometry as biosensors for rapid detection of plant associated bacteria

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Faheem Ahmad, Mansoor A. Siddiqui, Olubukola O. Babalola, Hui-Fen Wu
This study is based on the application of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) as biosensor to detect the plant associated bacteria (PAB) isolates from rhizospheric soil and root. The rapid bacterial detection via on particle ionization/enrichment technique using IgG functionalized Pt NPs (IgG-Pt NPs) assisted MALDI-TOF MS was successfully used to explore two PAB isolates, namely, Bacillus thuringiensis and B. subtilis from rhizospheric soil and roots of carrot plant. When these bacteria are used as bioformulations in agricultural as well as biotechnological applications, the plant growth promotion of economic crops was observed especially when the crops grow in less fertilize soil regions. This study proved that even at low concentrations, bacteria can also be directly detected without morphological, molecular and biochemical test. The current applied technique is simple, rapid and highly sensitive. Besides, it could be widely used for the detection of beneficially important PAB isolates in environmental samples.

Preparation of photolithographically patterned inverse opal hydrogel microstructures and its application to protein patterning

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Yeongmin Lee, Sangphil Park, Sang Won Han, Tae Geuk Lim, Won-Gun Koh
Protein pattern has played an important role in biosensors, bioMEMS, tissue engineering, fundamental studies of cell biology, and basic proteomics research. Here, we developed a straightforward and effective protein patterning technique using macroporous poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel micropatterns as a three-dimensional (3D) template for protein immobilization. Micropatterns of macroporous hydrogels with inverse opal structures were prepared on poly(ethylene glycol) (PEG)-coated silicon substrates by combining a colloidal crystal templating method with photopatterning. The resultant inverse opal hydrogel (IOH) micropatterns were modified with 3-aminopropyltriethoxysilane using the hydroxyl groups in PHEMA for the covalent immobilization of proteins. Proteins were selectively immobilized only on the hydrogel micropatterns, while the PEG regions served as an effective barrier to protein adsorption. Because of their highly ordered and interconnected 3D macroporous structures and large internal surface areas, protein loading in the IOH micropattern was about six times greater than that on a non-porous hydrogel micropattern, which consequently improved the protein activity. The porosity of the hydrogel micropatterns could be controlled using different sizes of colloidal nanoparticles, and using smaller nanoparticles produced hydrogel micropatterns with higher protein loading capacities and activities. To demonstrate the potential use of IOH micropatterns in biosensor systems, biotin was micropatterned on the hydrogels and the specific binding of streptavidin was successfully assayed using IOH micropatterns with better fluorescence signals and sensitivity than that of the corresponding non-porous hydrogel micropatterns.

Graphene/quantum dot bionanoconjugates as signal amplifiers in stripping voltammetric detection of EpCAM biomarkers

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Muhammad J.A. Shiddiky, Sakandar Rauf, Prakash H. Kithva, Matt Trau
A sensitive electrochemical immunosensor for the detection of epithelial cell adhesion molecule (EpCAM) antigen, a common marker for tumors of epithelial origin, employing bionanoconjugates as signal-transduction labels has been developed. The bionanoconjugates were fabricated by carboxylation of the two-dimensional graphene oxide nanosheets (GRs) and immobilizing streptavidin and amine-functionalized CdSe quantum dots (QDs) on carboxylated GRs via carbodiimide coupling chemistry, followed by the immunoreaction with the biotinylated secondary antibodies. Since carboxylated GRs have a higher density of active sites, it allows a large number of CdSe QDs to be immobilized onto the surface of the bionanoconjugates, and hence, enhance the sensitivity of the immunosensor. The method enabled detection limits of 100fg/mL and 1pg/mL (based on the S/N=3) in PBS buffer and serum samples, respectively, using anodic stripping voltammetric readout. The immunosensor showed a good selectivity, reproducibility, and long-storage stability, and may become a promising technique for the early detection of tumor biomarker in clinical/biological samples.

A highly sensitive, label-free gene sensor based on a single conducting polymer nanowire

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Bhuvaneswari Kannan, David E. Williams, Cosmin Laslau, Jadranka Travas-Sejdic
A prerequisite for exploiting sensing devices based on semiconductor nanowires is ultra-sensitive and selective direct electrical detection of biological and chemical species. Here, we constructed a transducer based on copolymer of poly(3,4,-ethylenedioxythiophene) (PEDOT) and carboxylic group functionalised PEDOT single nanowire in between gold electrodes, followed by covalent attachment of amino-modified probe oligonucleotide. The target ODNs specific to Homo sapiens Breast and ovarian cancer cells were detected at femtomolar concentration and incorporation of negative controls (non-complementary ODN) were clearly discriminated by the sensor. The ex situ measurements were performed by using two terminal device setup and the changes in the interface of the nanowire associated with the association or dissociation of ODNs were measured as change in resistance. In addition, in situ measurements were performed by utilizing scanning ion conductance microscopy to measure the change in resistance of probe modified nanowire upon addition of different concentration of target ODNs in presence of relevant buffer. The constructed, nano sensor showed highly sensitive concentration dependent resistance change.

Self-stacked submersible microbial fuel cell (SSMFC) for improved remote power generation from lake sediments

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Yifeng Zhang, Irini Angelidaki
Electric energy can be harvested from aquatic sediments by utilizing microbial fuel cells (MFCs). A main challenge of this application is the limited voltage output. In this study, an innovative self-stacked submersible MFC (SSMFC) was developed to improve the voltage generation from lake sediments. The SSMFC successfully produced a maximum power density of 294mW/m2 and had an open circuit voltage (OCV) of 1.12V. However, voltage reversal was observed in one cell at high current density. Investigation on the cause for voltage reversal revealed that voltage reversal was occurring only when low external resistance (≤400Ω in this study) was applied. In addition, the internal resistance and OCV were the most important parameters for predicting which cell unit had the highest probability to undergo voltage reversal. Use of a capacitor was found to be an effective way to prevent voltage reversal and at the same time store power. These results provide new insight into the development of effective MFC system, capable of extracting energy and promoting bioremediation of organic pollutants from sediments.

Oligopeptides functionalized surface plasmon resonance biosensors for detecting thiacloprid and imidacloprid

09 May 2012, 09:30:10
Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 35, Issue 1
Xiaokang Ding, Wei Zhang, Dan Cheng, Jianzhong He, Kun-Lin Yang
By using phage display library, we identified two highly specific oligopeptide sequences RKRIRRMMPRPS and RNRHTHLRTRPR for binding neonicotinoids such as thiacloprid and imidacloprid. The former shows high affinity for thiacloprid whereas the latter shows high affinity for imidacloprid. Surprisingly, cross binding is minimal despite the similarity of the two molecules. To develop a neonicotinoid biosensor, these two oligopeptides are synthesized and immobilized on the surface of a surface plasmon resonance (SPR) chip with a bare-gold surface. This oligopeptide functionalized SPR biosensor can rapidly detect thiacloprid and imidacloprid in buffer solutions in a real-time manner. The limit of detection (LOD) for thiacloprid and imidacloprid is 1.2μM and 0.9μM, respectively. 

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