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The rational design and synthesis of an efficient bielectrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) by tuning the chemical composition, structure and the catalytic sites of the hybrid materials is always of a great challenge. In this work, an innovative strategy based on the highly active N,N′-carbonyldiimidazole (CDI) is described to one-pot synthesis of a novel precursor for bifunctional O2-electrocatalyst. The coordination of Co2+ with the in situ generated ligands imidazole and carbonate results in ultrafine cobalt carbonate (CoCO3)-involved cobalt-based zeolitic imidazole framework (CoCO3/Co-ZIF). Owing to the presence of ultrafine CoCO3, carbonization of CoCO3/Co-ZIF at 800 °C under N2 atmosphere endows the pyrolysis product with a special skeleton of carbon nanotube (CNT)-tipped end CoOx, multivalent CoOx wrapped in graphitic carbon layers. Thus, the resulting CoOx/Co-N-C exhibits the enhanced and durable ORR/OER performance in alkaline media, due to the fast electron and mass transfers. For ORR, a large limiting current density of 4.59 mA cm−2 can be obtained by CoOx/Co-N-C, which is comparable to that of Pt/C. For OER, it only needs an over potential of 1.65 V to achieve a current density of 10 mA cm−2, merely 30 mV behind IrO2 (1.62 V).

One of the greatest challenges that define the performance of a fibre optic biosensor (FOBS) is the immobilization of the bio-receptor molecules onto the surface of fibre optic. In this study, a photoinducible silane diazirine was developed as an effective crosslinker in the construction of a chemiluminescent immunosensor targeting a model E. coli analyte. After optimization, it has shown superior adaptability over traditional chemiluminescent ELISA and a commonly used glutaraldehyde chemical immobilization method in detection limit (6.44 * 102 CFU/ml) and dynamic range (6.44 *105 to 6.44 *108 CFU/ml, r2 = 0.98; 6.44 *102 to 6.44 *105, r2 = 0.92). The newly developed immobilization method has enhanced the function of FOBS as an affordable and dispatchable tool in the early warning monitoring of the putative presence of E. coli cells. It can be used either in individual sample screening or in continuous monitoring of the environment to indicate the need for further investigation. The diazirine crosslinking method can also be adopted in the immobilization of other protein-based bioentities thus expanding its real-world utility. NRF (Natl Research Foundation, S’pore)

In the quest of greater sensitivity and specificity of diagnostic systems, one continually searches for alternative DNA hybridization methods, enabling greater versatility and where possible field-enabled detection of target analytes. We present, herein, a hybrid molecular self-assembled scaffolded DNA origami entity, intimately immobilized via capture probes linked to aminopropyltriethoxysilane, onto a glass optical fiber end-face transducer, thus producing a novel biosensor. Immobilized DNA nanorobots with a switchable flap can then be actuated by a specific target DNA present in a sample, by exposing a hemin/G-quadruplex DNAzyme, which then catalyzes the generation of chemiluminescence, once the specific fiber probes are immersed in a luminol-based solution. Integrating organic nanorobots to inorganic fiber optics creates a hybrid system that we demonstrate as a proof-of-principle can be utilized in specific DNA sequence detection. This system has potential applications in a wide range of fields, including point-of-care diagnostics or cellular in vivo biosensing when using ultrathin fiber optic probes for research purposes.

Carbon nanotubes (CNTs) have emerged recently as superior adsorbent materials for the removal of recalcitrant pollutants. The potential of combining the sorption capability of CNTs with bacterial degradation for pollutant removal, however, necessitates further investigation of the mechanisms of CNTs’ toxicity towards bacterial cells. In this study, we used a panel of stress-responsive recombinant Escherichia coli bioluminescence bacterial strains to explore the possible mechanisms of toxicity of multiwalled carbon nanotubes (MWCNTs). The effects of MWCNTs on markers of oxidative stress, protein, DNA, and membrane damage enabled the exposition of some of the mechanisms of their antimicrobial properties. Using both a bioluminescence bioreporter panel and live/dead staining, we observed that membrane damage played a role in the toxicity of MWCNTs. A subsequent viability study using three strains of bacteria—two gram-negative (Escherichia coli, Pseudomonas aeruginosa) and one gram-positive (Bacillus subtilis)—showed significant MWCNT toxicity in hypotonic water and phosphate-buffered saline solution, compared with the MWCNT toxicity towards the same bacteria incubated in isotonic-rich media. Using a field-emission scanning electron microscope, we demonstrated that membrane damage is caused largely by MWCNTs trapping bacteria and piercing the cell walls. As a result of our observations, we propose integrating MWCNTs and bacteria degradation for pollutant removal in nutrient-rich media to minimize the toxicity effect of CNTs. NRF (Natl Research Foundation, S’pore) Accepted version

An easy, rapid and sensitive method for the detection of meat species is important to identify adulteration or fraudulent substitution in raw meats with undeclared species. We report herein the development of an optical fibre genosensor able to detect low level of pork (Sus Scrofa) meat in mixtures of minced meat obtained by an optimized and faster DNA extraction protocol. Our approach uses highly specific and sensitive DNA capture and secondary probes designed out of the mitochondrion genome of Sus Scrofa. Once DNA capture probes were immobilized on optical fibres, we demonstrate their putative application as genosensors in detecting Sus Scrofa DNA in purified samples obtained first using a commercial DNA extraction kit and thereafter using our improved extraction method. Furthermore, analysis of beef (Bos taurus) minced meat samples also show that the assay can determine 1% (w/w) of Sus Scrofa DNA. The sensitivity obtained by the optical fibre and the short time required for the results (about 2.5 h) indicate the usefulness of the system. We envision that this genosensor may serve as a diagnostic tool for food sample screening using a technology that is accurate, simple to perform and has the potential to be used in portable format.

In this study, composite calcium-alginate/carbon nanotubes/TiO2 beads were prepared and tested for their potential in the removal of bisphenol A (BPA) from aqueous solutions. The removal traits were inspected using a fixed-bed sorption column. By varying parameters such as bed height (15–20 cm), flow rate (2.0–6.0 mL.min−1) and inlet BPA concentration (10–30 mg.L−1) we assessed the removal capacity of these composites. The highest sorption capacity of 5.46 mg.g−1 was achieved at 10 mg.L−1 BPA concentration, 2.0 mL.min−1 flow rate and 20 cm bed height at saturation. Adams-Bohart, Yoon-Nelson and Dose-Response isotherm models were applied to evaluate the performance of the column at different inlet concentrations. The experimental data satisfactorily fit the Dose-Response model with high correlation (r2 > 0.97) across the breakthrough curve. Regeneration of the used adsorbent beads were performed by immersion in the desorption solvent followed by light irradiation. It was postulated that inclusion of TiO2 facilitates the desorbed pollutant degradation from the used adsorbent beads.

Mercury ion (Hg(2+)) is an extremely toxic ion, which will accumulate in human bodies and cause severe nervous system damage. Therefore, the sensitive and efficient monitoring of Hg(2+) in human bodies is of great importance. Upconversion nanoparticle (UCNPs) based nano probes exhibit no autofluorescence, deep penetration depth and chemical stability in biological samples, as well as a large anti-stokes shift. In this study, we have developed thiazole-derivative-functionalized UCNPs, and employed an upconversion emission intensity ratio of 540 nm to 803 nm (I540/I803) as a ratiometric signal to detect Hg(2+) in living cells showing excellent photo stability and high selectivity. Our nano probe was characterized using transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD). The low cytotoxicity of our probe was confirmed by an MTT assay and the UCL test in HeLa cells was carried out by confocal microscopy. Our results demonstrated that organic-dye-functionalized UCNPs should be a good strategy for detecting toxic metal ions when studying cellular biosystems.

A high performance impedimetric immunosensor for the dengue virus antibody detection is presented. The setup profits from the formation of controlled and reproducible carbon nanotube (CNT) deposits on electrodes. Their easy functionalization via electrogeneration of a polypyrrole-NHS (N-hydroxysuccinimido 11-(pyrrol-1-yl) undecanoate) film enables the immobilization of the Dengue Virus 2 NS1 glycoprotein, the receptor unit, on the porous CNT layer via covalent amide coupling to provide the necessary selectivity towards Dengue NS1 antibody. All building steps of this immunosensor and the performance of this system were monitored by impedance spectroscopy and cyclic voltammetry. The resulting impedimetric dengue biosensor was tested in bovine blood plasma in addition to conventional measurements under controlled environment. After optimization, this immunosensor shows a good linearity in a wide concentration range (10−13–10−5 g mL−1).

4-N,N′-dimethylamino-4′-N′-stilbenemaleamic acid (DASMA), a unique molecular photochrome probe that exhibits solubility and retains trans-cis photoisomerisation in a wide range of organic solvents and aqueous pH environments, was prepared, purified and chemically characterised. Absorption, fluorescence excitation and emission spectra and constant-illumination fluorescence decay were measured in acetonitrile, dimethyl sulfoxide, ethanol, propylene carbonate, and aqueous glycerol mixtures. The pseudo-first-order fluorescence decay rates were found to be strongly dependent on the medium viscosity. In addition, the molecule exhibited the pH-dependent fluorescence and photoisomerisation kinetics. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

International audience; Diagnostic systems that can deliver highly specific and sensitive detection of hepatitis A virus (HAV) in food and water are of particular interest in many fields including food safety, biosecurity and control of outbreaks. Our aim was the development of an electrochemical method based on DNA hybridization to detect HAV. A ssDNA probe specific for HAV (capture probe) was designed and tested on DNAs from various viral and bacterial samples using Nested-Reverse Transcription Polymerase Chain Reaction (nRT-PCR). To develop the electrochemical device, a disposable gold electrode was functionalized with the specific capture probe and tested on complementary ssDNA and on HAV cDNA. The DNA hybridization on the electrode was measured through the monitoring of the oxidative peak potential of the indicator tripropylamine by cyclic voltammetry. To prevent non-specific binding the gold surface was treated with 3% BSA before detection. High resolution atomic force microscopy (AFM) confirmed the efficiency of electrode functionalization and on-electrode hybridization. The proposed device showed a limit of detection of 0.65 pM for the complementary ssDNA and 6.94 fg/μL, for viral cDNA. For a comparison, nRT-PCR quantified the target HAV cDNA with a limit of detection of 6.4 fg/μL. The DNA-sensor developed can be adapted to a portable format to be adopted as an easy-to-use and low cost method for screening HAV in contaminated food and water. In addition, it can be useful for rapid control of HAV infections as it takes only a few minutes to provide the results.

An original impedimetric immunosensor was developed based on carbon nanotube (CNT) deposits with controlled thicknesses for enhanced electroactive surface areas leading to improved sensor performances. Cholera monitoring was chosen as the model immune system for this setup. These CNT deposits were characterized using confocal laser microscopy and electrochemical methods. To form the sensor device, the CNT deposits were functionalized via electrocoating of polypyrrole-nitrilotriacetic acid (poly(pyrrole-NTA)) followed by the formation of a Cu (II) complex with the NTA functions. The bioreceptor unit, cholera toxin B Subunit, modified with biotin, was then immobilized via coordination of the biotin groups with the NTA-Cu(II) complex. Each step of the formation of the immunosensor and the subsequent binding of the analyte antibody anti-cholera toxin were investigated with cyclic voltammetry and Electrochemical Impedance Spectroscopy. After optimization, the resulting impedimetric cholera sensor shows excellent reproducibility, increased sensitivities, a very satisfying detection limit of 10−13 g mL−1 and an exceptional linear range for anti-cholera detection of 8 orders of magnitude (10−13–10−5 g mL−1) and a sensitivity of 24.7 ± 0.4 Ω per order of magnitude.

An original interfacial hybrid cross-linker molecule combined electrochemical and photochemical properties by substitution of two functional groups, pyrene, and diazirine. The first group enables anchoring by strong π-stacking interaction or by electropolymerization onto multi-walled carbon nanotubes (MWCNT). The other photoreactive group allows the covalent link with biomolecules under long-wavelength UV illumination. Diazirine was chosen due to its ability to photogenerate high reactive radicals under UV irradiation. The photoreactivity of these immobilized nanostructured conductive surfaces was tested towards the covalent attachment of tyrosinase which is well known to oxidize a large range of phenolic compounds and its yield and availability was evaluated by amperometric measurements of catechol by using molecular dioxygen. The architecture exhibiting the best analytical characteristics obtained for catechol was then chosen to detect dopamine.

Hepatitis A virus (HAV) infection has caused substantial morbidity and economic losses to human society, presenting a major public health problem in many parts of the world. Despite the capability for low-concentration detection, current PCR-based techniques are limited by the requirement of specialized lab equipment, trained personnel and a relatively large time-commitment. The need for a prompt in-field quantitative identification of HAV in real samples has led us to develop a chemiluminescent fibre optic genosensor system. In this study, a two-probe sandwich-type hybridization process was implemented on the tip of a fibre optic with an area of 0.12mm2. After optimization of the probes and the working conditions, we showed that the biosensor was able to work for both cDNA and RNA with a relatively large signal/noise ratio and a good sensitivity. An excellent specificity was also confirmed by screening with a broad range of other pathogen samples. The nucleic acid probes method was validated by optimized PCR and qPCR, and may thus be used when field testing would be required.

There is a need by the European Commission (EC) regulations, as well as others, to reduce the in vivo toxicity tests made on animals. Conventional in vitro tests were designed for non-nanoparticle sized entities, and therefore do not necessarily assess the adverse impacts of engineered nanoparticles (ENPs) on humans. Life cycle assessment (LCA) is a widely used methodology for evaluating the environmental performance of products. Nevertheless, the application of LCA on ENPs is difficult because the characterization factors (CFs) of ENPs, as significant input parameters in LCA, remain a major unknown. It is a premise of this study to monitor the chemiluminescence (CL) spectra resulting from the reactive oxygen species (ROS) trigger made from the presence of copper nanoparticles (CuNPs) to porcine neutrophils in vitro, thereby enabling to calculate the porcine and human toxicity CFs. The framework of a scientific consensus model, USEtox model, is selected and the midpoint of CF is set as the inflammation of pig or human. Finally, the present study recommends human and porcine inflammation CFs of CuNPs in Europe to be 1.07 and 2.90 CTU (comparative toxic units) respectively. China Scholarship Council (CSC)

A novel Photochrome-Aptamer Switch Assay (PHASA) for the detection and quantification of small environmentally important molecules such as toxins, explosives, drugs and pollutants, which are difficult to detect using antibodies-based assays with high sensitivity and specificity, has been developed. The assay is based on the conjugation of a particular stilbene-analyte derivative to any aptamer of interest. A unique feature of the stilbene molecule is its reporting power via trans-cis photoisomerisation (from fluorescent trans-isomer to non-fluorescent cis-isomer) upon irradiation with the excitation light. The resulting fluorescence decay rate for the trans-isomer of the stilbene-analyte depends on viscosity and spatial freedom to rotate in the surrounding medium and can be used to indicate the presence of the analyte. Quantification of the assay is achieved by calibration of the fluorescence decay rate for the amount of the tested analyte. Two different formats of PHASA have been recently developed: direct conjugation and adaptive binding. New stilbene-maleimide derivatives used in the adaptive binding format have been prepared and characterised. They demonstrate effective binding to the model thiol compound and to the thiolated Malachite Green aptamer. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

The synthesis and electropolymerization of a pyrrolic concanavalin A derivative (pyrrole-Con A) onto a multiwalled carbon nanotube (MWCNT) deposit is reported. Glucose oxidase was then immobilized onto the MWCNT-poly(pyrrole-Con A) coating by affinity carbohydrate interactions with the polymerized Con A protein. The resulting enzyme electrode was applied to the amperometric detection of glucose exhibiting a high sensitivity of 36 mA cm(-2) mol(-1) L and a maximum current density of 350 μA cm(-2) .

In recent years, the potential application of carbon nanotubes (CNTs) as sorbent materials in wastewater treatment has garnered tremendous attention. Concerns that CNTs may be toxic to living organism, however, necessitate that the containment of CNTs to prevent their release into the environment in order to realize their practical application in wastewater treatment. In this study, we immobilized multi-walled carbon nanotubes (MWCNTs) within macro-calcium alginate beads. The composite beads were coated with an additional polysulfone (Psf) layer both to provide an external barrier to MWCNTs release into the effluent and also to improve the mechanical integrity of the beads. The hybrid beads were tested for their capacity to remove the bio-refractory endocrine disruptor compound bisphenol-A (BPA) using batch and packed bead column experiments. Maximum BPA removal was achieved at 22% MWCNTs, which was the dispersion limit of MWCNTs in our study. The adsorption of BPA followed Langmuir isotherm model with good correlation. The maximum adsorption capacity of the composite beads of dosage 4 g L−1 as obtained using the Langmuir model was 24.69 mg g−1. Addition of the Psf layer, together with MWCNTs, improved the bead compression performance by up to twelvefold at 40% compressive extension. This study showed that the hybrid alginate-Psf bead may serve as compartment for encapsulation of MWCNTs for removal of BPA. Improved compression performance introduced by addition of Psf layer could protect hybrid beads used, for example, in reactors subjected to extreme conditions such as high flow rates. Published version

Two methods for phenol determination based on the suppression of chemiluminescence (CL) produced upon HRP-catalysed oxidation of luminol were developed. One method used an enhanced CL reaction with 3-(10′-phenothiazinyl)-propane-1-sulfonate and 4-morpholinopyridine as primary and secondary enhancers, respectively, and another one is free of the enhancers. A comparison of the phenol assay with enhancers showed much higher sensitivity and lower LDL value than the assay without enhancers. In addition, the amount of HRP used in the assay with enhancers is 40 times less than in the assay without them. The study of the specificity of the developed assays demonstrated that in the assay without enhancers several phenol compounds, for instance, unsubstituted phenol, suppressed the CL intensity, whereas other phenols, such as 4-chlorophenol and 2,4-dichlorophenol, increased the light output. In contrast to that assay, in the assay with enhancers all tested phenols suppressed the CL intensity. Upon the analysis of phenols in the water plant effluents using the assay without the enhancers, a high matrix effect was observed. On the other hand, the analysis of the same effluents using the assay with enhancers did not show any matrix effect, and the recovery values from the spiked samples were found to be 92–96%.

It is important to design a functionalization scheme for carbon nanotubes that preserves their outstanding proprieties, while adding new proprieties, thereby enabling their integration in fuel cell applications. In the present work, we describe the production of a non-covalently attached network of porphyrins to multi-walled carbon nanotubes (MWCNT) sidewalls. The approach is based on π–π stacking interactions of pyrene-modified metalloporphyrins onto MWCNT sidewalls. Two configurations of MWCNT–porphyrin hybrid electrodes were both electrochemically characterized and tested under alkaline conditions. Pyrene-functionalized rhodium deuteroporphyrin (Rh(DP)pyr2), was used as an anode in the electrocatalytic oxidation of glucose and pyrene-functionalized tetracarboxyphenyl cobalt porphyrin (Co(TCPP)pyr4) was itself used as a cathode in the electrocatalytic reduction of oxygen. Both electrodes were integrated into a glucose fuel cell system leading to a maximum power output of 0.9(±0.10) mW cm−2. Compared to alternative system approaches, pyrene-modified porphyrin hybrid electrodes and their corresponding fuel cell devices exhibited higher activity, power output, and long term stability.

Most people spend a greater amount of time indoors rather than outdoors, so it follows that it's composition could directly affect occupants, thereby providing a new demand for sensors that will monitor indoor air pollution. In this paper, bioluminescent bacteria were used as bioreporters for the determination of air toxicity. Bacteria were immobilized in 96 well plates with matrices of different types and volumes, and exposed to a selection of model toxic compounds in air. TV1061 strain immobilized in alginate in wells of a microtiter plate showed the best response to a low concentration of chloroform (6.65 ppb), while US permission limits stands now at 50 ppm. This system was then adapted to the end face of a portable fiber optic biosensor, and we predict that one day it could be used as an air pollution alert system in an indoor environment.

Immunosensors are powerful analytical tools in clinical and veterinary diagnostics. This has led us to design a chemiluminescent immunosensor aimed at identifying anti-Brucella antibodies using optical fibers as the transducer. In order to develop the optimal transducer, to achieve an optimal chemical modification thereby allowing an optimal covalent binding of the protein receptor, several cleaning strategies and silane coupling agents were investigated. Brucella killed organisms were used as a model receptor for quantifying anti-Brucella IgG antibodies in a suspension compared to conventional colorimetric and chemiluminescent ELISA. A silane-benzophenone derivative was selected as the best performing silane coupling agent: the optical fiber immunosensor (OFIS) has showed the lowest limit of detection at 0.207 microg/ml, compared to 0.828 microg/ml and 0.414 microg/ml achieved by colorimetric and chemiluminescent ELISAs, respectively. These results, together with the additional advantages of rapidity, lower reagent volumes and moderate operating conditions, have set the grounds for further study in order to adapt this platform for on-site diagnostics of brucellosis disease markers.

A biosensor is a self-contained, bionic, integrated device that includes a biorecognition element that can respond in a concentration-dependent manner to a biochemical species. This article represents different possible methods of immobilizing biorecognition element used in fiber-optic-based biosensors. The method is chosen according to the analyte and the biorecognition element that will be used to sense it. In this review, two different approaches are represented: one using live organisms (based on bioluminescence) and one using immune reagents (based on chemiluminescence). Whole-cell fiber-optic biosensors have internal Bragg grating information with the potential to analyze samples without any additives in most cases. It includes a photon-counting system to measure a low-light response produced by markers of recognition elements. A flow-through, fiber-optic-based bacterial monitoring system for online monitoring of toxic pollutants in water has been developed. This monitoring system has proved to be a useful next step in the development of a simple online, realtime sensor for relevant human toxicants in flowing water.

Brucellosis is a worldwide distributed zoonotic re-emerging disease, causing abortions in domesticated animals and Malta fever in humans. Currently, the gold standard for confirmation of the existence of the causative agent genus Brucella is the isolation of the bacteria from body or liquid samples, whereas standard serological tests are used for diagnosis. The need for a rapid point of care identification of Brucella organisms has led us to develop a novel chemiluminescent optical fiber immunosensor. The immunosensor based on a conventional enzyme linked immunoassay (ELISA) technique was implemented on optical fibers and its performance was compared to the standard ELISA method. We show that depending on the detecting antibodies used specificity of the assay is achieved. Brucella cells presenting smooth-A O-chain determinant were detected at a minimal protein concentration of 1.098 ng/ml, correlating to 305 cfu/ml, while smooth-M O-chain cells, rough cells and two gram-negative bacteria other than Brucella sp. produced negative results, confirming the high specificity of the technique.

Several methodologies have been used in clinical chemistry for real-time assessment of NADPH oxidase primary product superoxide anion which dismutases to hydrogen peroxide. Among these methodologies, isoluminol chemiluminescence (CL) is considered to be one of the more sensitive and reliable techniques for the assessment of NADPH oxidase activity in neutrophils. The electrochemical technique was recently designed and also applied for real-time detection of NADPH oxidase activity in neutrophils but its reliability and sensitivity has not been investigated so far. In this study, isoluminol CL and electrochemical techniques were investigated and compared by monitoring the generation of superoxide and hydrogen peroxide in both PLB 985 cell line differentiated into neutrophil-like cells and human neutrophils. The electrochemical technique was shown to be as sensitive as that of CL and able to detect the reactive oxygen species (ROS) release of as low as 500 cells. Thus, the electrochemical technique could be used as an alternative to optical techniques for the evaluation of extracellular ROS in phagocyte cells.

We report that electropolymerization parameters (duration and voltage) modulate the properties and morphological structures of photoactive polymers which influence both the efficiency of bioreceptor attachment to the polymer surface, and the resulting biosensor assay performance. We have compared two biosensor technologies, optical and electrochemical, for the detection of anti-cholera toxin antibodies using our singular conductive optic fibers, albeit at this stage in separate experiments. Both biosensor systems were more sensitive than conventional detection and pave the way for the possibility to one day make simultaneous optical and electrochemical sensing using the same biosensor.

Graphene and graphene-like two-dimensional nanomaterials have aroused tremendous research interest in recent years due to their unique electronic, optical, and mechanical properties associated with their planar structure. Aptamers have exhibited many advantages as molecular recognition elements for sensing devices compared to traditional antibodies. The marriage of two-dimensional nanomaterials and aptamers has emerged many ingenious aptasensing strategies for applications in the fields of clinical diagnosis and food safety. This review highlights current advances in the development and application of two-dimensional nanomaterials-based aptasensors with the focus on two main signal-transducing mechanisms, i.e. electrochemical and optical. A special attention is paid to graphene, a one-atom thick layer of graphite with exceptional properties, representing a fastgrowing field of research. In view of the unique properties of two-dimensional nanostructures and their inherent advantages of synthetic aptamers, we expect that high-performance two-dimensional nanomaterials-based aptasensing devices will find extensive applications in environmental monitoring, biomedical diagnostics, and food safety. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

We describe herein the construction of a novel computerized multi-sample temperature-controlled luminometer for a fiber array-based biosensor to monitor circulating phagocyte activity. It can perform simultaneously integral measurements of chemiluminescence emitted from up to six samples containing less than 0.5 microl whole blood while the samples and detector do not change their position during the measurement cycle. The optical fibers in this luminometer are used as both light guides and solid phase sample holders. The latter feature of the instrument design simplifies the assessment process of both the extra-cellular and the intra-cellular parts of the phagocyte-emitted chemiluminescence using the same system. We describe some examples or proof of principle for the use of the biosensor. This new technology may find use in a wide range of analytical luminescence applications in biology, biophysics, biochemistry, toxicology and clinical medicine.

We describe herein a newly developed optical microbiosensor for the diagnosis of hepatitis C virus (HCV) by using a novel photoimmobilization methodology based on a photoactivable electrogenerated polymer film deposited upon surface-conductive fiber optics, which are then used to link a biological receptor to the fiber tip through light mediation. This fiber-optic electroconductive surface modification is done by the deposition of a thin layer of indium tin oxide on the silica surface of the fiber optics. Monomers are then electropolymerized onto the conductive metal oxide surface; thereafter, the fibers are immersed in a solution containing HCV-E2 envelope protein antigen and illuminated with UV light (wavelength approximately 345 nm). As a result of the photochemical reaction, a thin layer of the antigen becomes covalently bound to the benzophenone-modified surface. The photochemically modified fiber optics were tested as immunosensors for the detection of anti-E2 protein antibody analyte that was measured through chemiluminescence reaction. The biosensor was tested for sensitivity, specificity, and overall practicality. Our results suggest that the detection of anti-E2 antibodies with this microbiosensor may enhance significantly HCV serological standard testing especially among patients during dialysis, which were diagnosed as HCV negative, by standard immunological tests, but were known to carry the virus. If transformed into an easy to use procedure, this assay might be used in the future as an important clinical tool for HCV screening in blood banks.

We report herein a simple and effective way to photochemically immobilize biomolecules onto a fibre-optic silica surface. The system is based on a photoreactive benzophenone derivative that is bound to SiO2 surfaces of the optical fibre via a silane anchor. The benzophenone derivative was 4-allyloxybenzophenone, synthesized by standard procedures that were later used to synthesize the 4-(3′-chlorodimethylsilyl) propyloxybenzophenone and 4-(3′-dichloromethylsilyl) propyloxybenzophenone by regular hydrosilation procedures. After silanization with the benzophenone derivatives, the fibres were immersed in a cholera toxin B subunit solution and illuminated with UV light (wavelength > 345 nm). As a result of the photochemical reaction, a thin layer of the antigen was covalently bound to the benzophenone-modified surface. The photochemically modified fibre-optics were then tested as immunosensors in the detection of cholera anti-toxin antibody and revealed through chemiluminescence measurements. A secondary antibody labelled with horseradish peroxidase acted as the marker for the cholera toxin antibody. A photo-electronic set-up was designed specifically to monitor the signal. The immunosensor system was shown to be both specific and sensitive. The lowest rabbit serum titre detected was 1:1 700 000. Copyright © 2004 John Wiley & Sons, Ltd.

International audience; The cytotoxic effects of carbon-based nanomaterials are evaluated via the induction of luminescent genetically engineered Escherichia coli bacterial cells. Specifically, two engineered E. coli bacteria strains of DPD2794 and TV1061 were incubated with aqueous dispersion of three carbon allotropes (multi-wall carbon nanotubes (MWCNTs), graphene nanosheets and carbon black nanopowders) with different concentrations and the resulting bioluminescence was recorded at 30 °C and 25 °C, respectively. The corresponding optical density changes of bacterial cells in the presence of various carbon nanomaterials were recorded as well. Based on these results, E. coli DPD2794 bacterial induction responds to a greater degree than E. coli TV1061 bacteria when exposed to various carbon-based nanomaterials. Finally, the surface morphology of E. coli DPD2794 bacteria cells before and after carbon-based nanomaterials treatment was observed using a field emission scanning electron microscope (FESEM), from which morphological changes from the presence of carbon-based nanomaterials were observed and discussed.

Electrochemical and optical biosensors exist to monitor different fluids containing analytes of interest. Until today, these have been developed separately. Owing to the creation of new transducer configurations such as indium tin-coated glass fiber optics, these methods can now be used separately, in parallel and it is hoped that one day they will be able to be used simultaneously; thus, using the same probe to measure a single analyte using two different methods (electrochemical and optical) or two different analytes with either of the aforementioned methods sitting on the same probe. This article will highlight the importance, as well as the usefulness, of combining measurement methodologies in improving sensor response and sensitivity.

Conservation of water resources calls for ever stricter regulatory measures and better monitoring systems. Whole-cell bacterial sensors have been genetically engineered to react to target toxicants by the induction of a selected promoter and the subsequent production of bioluminescent light through a recombinant lux reporter. In order to create a one-step assay, we have designed a new, self-contained, disposable optical fiber sensor module and a customized photodetector system that integrates these microorganisms. A photon-counting photomultiplier tube-based instrument was constructed. Optical fiber tip cores were covered with adlayer films consisting of calcium alginate containing bioluminescent bacterial sensors of genotoxicants. Multiplying these steps thickened the adlayer in increments, increasing the number of bacterial reporters attached to the optical fiber transducer. These whole cell optrodes are responsive to external traces of DNA damaging agents such as mitomycin C. Light production was shown to be dose-dependent and proportional to the number of bacterial layers.

A novel single mode tapered optical fibre loop biochemical sensor based on fluorescence spectroscopy has been developed. The fundamental fibre mode propagates through the tapered portion of an optical fibre and generates an evanescent field which penetrates into the aqueous environment surrounding the fibre where the bio-recognition event occurs. A two-step assay was used, in which the analyte was labelled secondarily with a fluorescent dye, fluorescein isothiocyanate or tetramethyl rhodamine. When excited by the input argon ion laser light from the near end of the taper, generated fluorescence is coupled into the guided mode of the fibre and collected at the far end of the taper. Methods of making the sensor chemically reusable were investigated. The high sensitivity (75 pg/ml) of the single mode tapered loop device, combined with a simple immobilization protocol, provides a powerful tool for performing immunoassays.

We demonstrate the direct printing of proteins on a surface using a cantilevered nanopipette as the probe of a scanned probe microscope. Protein features as small as ∼200 nm were directly delivered through the ∼100 nm aperture of the nanopipette by simply contacting the probe with any surface. This allows for the direct connection of this methodology to standard separation techniques so that multiple proteins can be printed through one nanopipette at different locations in ambient conditions.

Ebolavirus, a member of the familyFiloviridae, causes high lethality in humans and nonhuman primates. Research focused on protection and therapy for Ebola virus infection has investigated the potential role of antibodies. Recent evidence suggests that antibodies can be effective in protection from lethal challenge with Ebola virus in nonhuman primates. However, despite these encouraging results, studies have not yet determined the optimal antibodies and composition of an antibody cocktail, if required, which might serve as a highly effective and efficient prophylactic. To better understand optimal antibodies and their targets, which might be important for protection from Ebola virus infection, we sought to determine the profile of viral protein-specific antibodies generated during a natural cycle of infection in humans. To this end, we characterized the profile of antibodies against individual viral proteins of Sudan Ebola virus (Gulu) in human survivors and nonsurvivors of the outbreak in Gulu, Uganda, in 2000-2001. We developed a unique chemiluminescence enzyme-linked immunosorbent assay (ELISA) for this purpose based on the full-length recombinant viral proteins NP, VP30, and VP40 and two recombinant forms of the viral glycoprotein (GP1-294and GP1-649) of Sudan Ebola virus (Gulu). Screening results revealed that the greatest immunoreactivity was directed to the viral proteins NP and GP1-649, followed by VP40. Comparison of positive immunoreactivity between the viral proteins NP, GP1-649, and VP40 demonstrated a high correlation of immunoreactivity between these viral proteins, which is also linked with survival. Overall, our studies of the profile of immunorecognition of antibodies against four viral proteins of Sudan Ebola virus in human survivors may facilitate development of effective monoclonal antibody cocktails in the future.

Food and beverage industries require rapid tests to limit economic losses and one way to do so is via molecular tests. In the present work, DNA capture and secondary probes, were designed to target the ITS (Internal Transcribed) sequences of Brettanomyces bruxellensis, a yeast responsible for the production of off flavours in both wine and beer. ITS1 and ITS2 were found to contain distinct regions with sufficient sequence divergence to make them suitable as specific identification target sites. The dot blot technique was used to determine the sensitivity and specificity of the capture probe. Both probes were, thereafter, adapted to construct an optical fibre genosensor, which produced neither false positives nor false negatives, and was both repeatable and faster with respect to traditional methods, the latter requiring at least one week to detect B. bruxellensis.

Endocrine disrupting compounds (EDCs) such as bisphenol A (BPA) and female hormone Estrone are especially prevalent in surface and waste-waters in nano-molar concentra tions and therefore, there is a need for sensitive analytical device for their monitoring. We have designed a miniature, low cost and fast surface plasmon resonance (SPR) imaging liquid sensor based on the angular interrogation using Kretsc hmann configuration with diverged incident monochromatic light. During this paper we present a surface plasmon resona nce imaging (SPRI) biosensor to detect EDCs such as BPA and estrone. A pattern of SPR line which is dark intensity line on bright area was reflected at angles range depending on the dielectric constant of the analye: Rabbit Anti-Estrone polyclonal IgG + Estrone 11-MUA attached to the silver or non-specific sensing of BPA in water with nanoprecision. For analyzing the SPR signals we used an efficient detection algorithm based on Radon Transform with less sensitivity to laser speckle noise and nonuniformity of the illumination. Keywords: Surface Plasmon Resonance (SPR) Imaging, biosensing , estrogenic disruptors, Bisphenol A, Estrone.

International audience; Infection with dengue virus has emerged as the most important vector-borne viral disease in tropical areas and it continues to expand geographically. The four serotypes of dengue virus (DENV) cause human disease and are transmitted by Aedes mosquitoes. A reliable diagnosis remains a crucial step towards the control of dengue disease in human populations. In this work, a new diagnostic tool was developed based on chemiluminescent optical fiber immunosensor (OFIS), for the detection of anti-DENV immunoglobulin M (IgM) in human serum samples. The immunoassay was based on a colorimetric IgM capture, enzyme-linked immunosorbent assay (MAC-ELISA), routinely used by the National Reference Center for arboviruses based in French Guiana. The detection of human anti-DENV IgM using colorimetric MAC-ELISA, chemiluminescent MAC-ELISA and chemiluminescent OFIS was compared. An internal panel of reference sera was used and 86 sera samples were screened. Compared to standard colorimetric MAC-ELISA, the chemiluminescent OFIS had a lower detection limit, 10 times lower than the chemiluminescent MAC-ELISA and 100 times lower than the colorimetric MAC-ELISA. Therefore the colorimetric and chemiluminescent MAC-ELISA's are more suitable for high and intermediate levels of anti-DENV IgM present in serum samples, whereas the chemiluminescent OFIS is also useful at low analyte concentration, with sensitivity and specificity of 98.1% and 87.0%, respectively. Taking into account the lower limit of detection and the high correlation between the established methods with the known panel, the OFIS technology reported here is reliable, simple to perform, fast, cost effective, and a field operable analytical tool.

Different whole cell fiber optic based biosensors have been developed to detect the total effect of a wide range of environmental pollutants, providing results within a very short period. These biosensors are usually built from three major components, the biorecognition element (whole-cells) intimately attached to a transducer (optic fiber) using a variety of techniques (adsorption, covalent binding, polymer trapping, etc). Even with a great progress in the field of biosensors, there is still a serious lack of commercial applications, capable of competing with traditional analytical tools.

Recurrent bacterial peritonitis is a major complication in peritoneal dialysis (PD) patients, which is associated with polymorphonuclear leukocyte (PMN) functional changes and can be assessed by a chemiluminescent (CL) reaction. We applied a new approach of a dynamic component chemiluminescence sensor for the assessment of functional states of PMNs in a luminol-amplified whole-blood system. This method is based on the evaluation of CL kinetic patterns of stimulated PMNs, while the parallel measurements of intracellular and extracellular production of reactive oxygen species (ROS) from the same sample can be conducted. Blood was drawn from diabetic and nondiabetic patients during follow-up, and during peritonitis. Healthy medical personnel served as the control group. Chemiluminescence curves were recorded and presented as a sum of three biological components. CL kinetic parameters were calculated, and functional states of PMNs were assessed. Data mining algorithms were used to build decision tree models that can distinguish between different clinical groups. The induced classification models were used afterward for differentiating and classifying new blind cases and demonstrated good correlation with medical diagnosis (84.6% predictive accuracy). In conclusion, this novel method shows a high predictive diagnostic value and may assist in detection of PD-associated clinical states.

Numerous efforts are made among the scientific community to develop serological diagnostic tools that could be cheap, fast and easy to perform but with comparable sensitivity to current bulky routine laboratory tests. Chemiluminescent optical fiber immunosensors are biosensors that can fit these expectations. These devices include an ELISA-type assay based on immobilized bioreceptors onto a surface of an optical fiber. Upon recognition of the target biomolecules, a chemiluminescent signal derived from an enzymatic reaction is captured by the fiber and transduced to a photon counting system. These immunosensors proved already to be very efficient for pathogens or tumor markers detection. Keywords: biosensor; immunosensor; optical fiber; chemiluminescence; photon counting systems

The article describes basics of approach to build a device dedicated to sensitive assessment of phagocyte activity in biological fluids. The unique place of phagocytosis in the innate immune system, the mechanisms, localization and factors of oxidative phagocyte activity as well as the techniques used to detect respiratory burst and localization are briefly reviewed. Sensor design combines simplicity and artifact -absence in whole blood system, simultaneous record and analysis of extra-cellular and intra-cellular luminescence, sensitivity and efficiency of signal capturing of optical fiber–photomultiplier detection system and the convenience of disposable sample holder. Keywords: sensor; blood; chemiluminescence; phagocyte; extracellular; intracellular; luminometer; fiber; disposable

This paper describes the development and evaluation of an optical fiber immunosensor (OFIS) for the detection of IgG antibody to Rift Valley fever virus (RVFV) in humans. The OFIS was based on a sandwich enzyme-linked immunosorbent assay (S-ELISA) format, whereby gamma-irradiated RVFV and control antigens were immobilized on the optical fiber surface coated with a mouse anti-RVFV antibody. Data sets derived from field-collected sera in Africa (n = 242) were dichotomized according to the results of a virus neutralization test. Compared to standard colorimetric S-ELISA, the OFIS technique was more sensitive in detecting smaller quantity of specific IgG to RVFV in human sera. At cut-off value selected at a 95% accuracy level by the two-graph receiver operating characteristic analysis, the OFIS diagnostic sensitivity was 97.22% and diagnostic specificity 98.86%. Our results demonstrate that the OFIS technology reported here is highly accurate, simple to perform and has the potential to be used in a portable format.

The surface-enhanced Raman scattering (SERS) technique was shown to be an effective molecular analytical tool due to its high sensitivity. Here, we propose to exploit soft UV assisted nanoimprint lithography (UV-NIL) for the development of a reproducible and highly-sensitive SERS biosensor. Soft lithography is known to be advantageous for biological applications since it is compatible with insulating supports and large-area samples. In the present investigations, soft UV-NIL is used for the fabrication of large-sized arrays of gold nanocylinders on glass which were shown to be highly sensitive and highly specific sensing surfaces, with a limit of detection measured down to 1 nM. Employing the UV-NIL SERS substrate enable working ranges of nanomolar to micromolar concentrations in regards to our model paclitaxel analyte.

We describe herein a newly developed optical immunosensor for detection of antibodies directed against antigens of the Ebola virus strains Zaire and Sudan. We employed a photo immobilization methodology based on a photoactivatable electrogenerated poly(pyrrole-benzophenone) film deposited upon an indium tin oxide (ITO) modified conductive surface fiber-optic. It was then linked to a biological receptor, Ebola virus antigen in this case, on the fiber tip through a light driven reaction. The photochemically modified optical fibers were tested as an immunosensor for detection of antibodies against Ebola virus, in animal and human sera, by use of a coupled chemiluminescent reaction. The immunosensor was tested for sensitivity, specificity, and compared to standard chemiluminescent ELISA under the same conditions. The analyte, anti-Ebola IgG, was detected at a low titer of 1:960,000 and 1:1,000,000 for subtypes Zaire and Sudan, respectively. While the same serum tested by ELISA was one order (24 times) less sensitive.

We report herein the development of an optical fiber based chemiluminescent immunosensor for detection of the native autoimmune response to GIPC-1, a PDZ containing protein involved in regulation of G-protein signaling. The recombinant protein GIPC-1 was expressed in bacteria, purified, refolded and conjugated to the tip of an optical fiber. A human monoclonal 27.B1 IgM isolated from a breast cancer patient, which targets the GIPC-1 protein, was used for calibration of the immunosensor and was detected down to a concentration of 30 pg/ml. We determined that the fiber-optic immunosensor had a detection limit 50 times lower than chemiluminescent ELISA, and approximately 500 times lower than colorimetric ELISA. In addition, sera from 11 ovarian cancer patients, 22 breast cancer patients and asymptomatic controls were tested for the presence of IgM anti-GIPC-1 autoantibodies in their serum using the two methods. The immunosensor assay detected 54% and 77% GIPC-1 positive sera within ovarian and breast cancer patients, respectively, as compared to chemiluminescent ELISA, which only detected 18% and 27%, respectively. We envision that this immunosensor may serve as a diagnostic tool for screening women for ovarian and breast cancer at an early stage, thus increasing their chance of survival.

The feasibility of creating nanometer scale depressions in biological substrates using active enzymes delivered with scanning probe microscopes has been previously demonstrated by us and other groups. Here we present a comprehensive study revealing the dependence of channels dimensions on the parameters of the "writing" process and provide a simple way to precisely control their dimensions. Such nanochannels may be used in nanofluidic biochip applications.

An ELISA-based optical fiber methodology developed for the detection of anti-West Nile virus IgG antibodies in serum was compared to standard colorimetric and chemiluminescent ELISA based on microtiter plates. Colorimetric ELISA was the least sensitive, especially at high titer dilutions. The fiber-optic immunosensor based on the same ELISA immunological rationale was the most sensitive technique.