Novel role of folate (vitamin B9) released by fermenting bacteria under Human Intestine like environment.

The anaerobic region of the gastrointestinal (GI) tract has been replicated in the anaerobic chamber of a microbial fuel cell (MFC). Electroactive biomolecules released by the facultative anaerobes (Providencia rettgeri) under anoxic conditions have been studied for their potential role for redox balance. MALDI study reveals the presence of vitamin B9 (folate), 6-methylpterin, para-aminobenzoic acid (PABA) and pteroic acid called pterin pool. ATR-FTIR studies further confirm the presence of the aromatic ring and side chains of folate, 6-methylpterin and PABA groups. The photoluminescence spectra of the pool exhibit the maximum emission at 420, 425, 440, and 445 nm when excited by 310, 325, 350, and 365 nm wavelengths (day 20 sample) highlighting the presence of tunable bands. The cyclic voltammetric studies indicate the active participation of pterin pool molecules in the transfer of electrons with redox potentials at - 0.2 V and - 0.4 V for p-aminobenzoate and pterin groups, respectively. In addition, it is observed that under prolonged conditions of continuous oxidative stress (> 20 days), quinonoid tetrahydrofolate is formed, leading to temporary storage of charge. The results of the present study may potentially be useful in designing effective therapeutic strategies for the management of various GI diseases by promoting or blocking folate receptors.

Fabrication of a Molecularly Imprinted Nano-Interface-Based Electrochemical Biosensor for the Detection of CagA Virulence Factors of H. pylori.

H. pylori is responsible for several stomach-related diseases including gastric cancer. The main virulence factor responsible for its establishment in human gastric cells is known as CagA. Therefore, in this study, we have fabricated a highly sensitive MIP-based electrochemical biosensor for the detection of CagA. For this, an rGO and gold-coated, screen-printed electrode sensing platform was designed to provide a surface for the immobilization of a CagA-specific, molecularly imprinted polymer; then it was characterized electrochemically. Interestingly, molecular dynamics simulations were studied to optimize the MIP prepolymerization system, resulting in a well-matched, optimized molar ratio within the experiment. A low binding energy upon template removal indicates the capability of MIP to recognize the CagA antigen through a strong binding affinity. Under the optimized electrochemical experimental conditions, the fabricated CagA-MIP/Au/rGO@SPE sensor exhibited high sensitivity (0.275 µA ng-1 mL-1) and a very low limit of detection (0.05 ng mL-1) in a linear range of 0.05-50 ng mL-1. The influence of other possible interferents in analytical response has also been observed with the successful determination of the CagA antigen.

Detection of biomolecules in dielectric modulated double metal below ferroelectric layer FET with improved sensitivity.

In this work, we examined the double metal below ferroelectric layer FET that is double metal below negative capacitance field-effect transistor (DM-below-NCFET) for biosensing application and change in nanocavity gap with biomolecules as protein, ChOx (cholesterol oxidase), streptavidin, and uricase. For measuring the electrical characteristic and neutral biosensing such as threshold voltage, switching ratio (Ion/Ioff) of the device which is higher than one without molecules by 1.52 times, sensitivity of protein enhanced by 1.11 over without biomolecule, limit of detection of protein is higher by 1.012 times over without molecule, shift in potential have been researched for cavity length 10 nm. The biosensor indicated improved sensitivity for biomolecules with the rise in their dielectric parameter. Moreover, modulation of the length of the gap of cavity was too examined, exposing that its increment (from 8 to 12 nm) altogether upgraded the sensitivity of the proposed biosensor. Visual TCAD (Technology Computer-Aided Design) software is used for simulating all results. In general, the consequences of this examination represent that such DM-below-NCFET biosensors can display extreme sensitivity (1.11) at small drain voltage (0.4 V), empowering their utilization for biosensor applications to analyze different infections which involve low power, extreme density, and enhanced speed.

A Chemosensor Based on Gold Nanoparticles and Dithiothreitol (DTT) for Acrylamide Electroanalysis.

Rapid and simple electroanalysis of acrylamide (ACR) was feasible by a gold electrode modified with gold nanoparticles (AuNPs) and dithiothreitol (DTT) with enhanced detection sensitivity and selectivity. The roughness of bare gold (Au) increased from 0.03 µm to 0.04 µm when it was decorated with AuNPs. The self-assembly between DTT and AuNPs resulted in a surface roughness of 0.09 µm. The DTT oxidation occurred at +0.92 V. The Au/AuNPs/DTT surface exhibited a surface roughness of 0.24 µm after its exposure to ACR with repeated analysis. SEM imaging illustrated the formation of a polymer layer on the Au/AuNPs/DTT surface. Surface plasmon resonance analysis confirmed the presence of AuNPs and DTT on the gold electrode and the binding of ACR to the electrode's active surface area. The peak area obtained by differential pulse voltammetry was inversely proportional to the ACR concentrations. The limit of detection (LOD) and the limit of quantitation (LOQ) were estimated to be 3.11 × 10-9 M and 1 × 10-8 M, respectively, with wide linearity ranging from 1 × 10-8 M to 1 × 10-3 M. The estimated levels of ACR in potato chips and coffee samples by the sensor were in agreement with those of high-performance liquid chromatography.

Exploring Providencia rettgeri for application to eco-friendly paper based microbial fuel cell.

We report results of the studies relating to improved stability (40 days) of small sized microbial fuel cell (MFC) fabricated using agarose embedded paper-based proton exchange membrane. A fermentative bacterium Providencia rettgeri was isolated from rotten potato slurry and identified by 16S rRNA sequencing. The electroactivity of the bacteria was monitored via chronoamperometric and cyclic voltammetric studies using a three-electrode system which indicated the presence of bacterial redox mediator. The Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) and UV-Vis absorption spectroscopy provided the evidence that Providencia rettgeri synthesized folate (vitamin B9) during fermentation that was found to act for the first time as a redox mediator in an MFC. The paper based designed MFC fed with Providencia rettgeri yielded open circuit voltage of 787.9 mV with power and current density of 5.02 W/m3 and 11.26 A/m3, respectively when measured across 10 kΩ. The microbial re-chargeable battery comprising of an assembly of parallelly aligned four units of MFCs when connected in series (total 16 MFCs), generated 1.5 V that was used for powering a red-light emitting device (LED).

An impedimetric biosensor based on electrophoretically assembled ZnO nanorods and carboxylated graphene nanoflakes on an indium tin oxide electrode for detection of the DNA of Escherichia coli O157:H7.

Aminopropyltrimethoxysilane (APTMS)-functionalized zinc oxide (ZnO) nanorods and carboxylated graphene nanoflakes (c-GNF) were used in a composite that was electrophoretically deposited on an indium tin oxide (ITO) coated glass substrate. The modified ITO electrodes were characterized using various microscopic and spectroscopic techniques which confirm the deposition of the APTMS-ZnO/c-GNF composite. The electrodes have been used for the covalent immobilization of an Escherichia coli O157:H7 (E. coli)-specific DNA prob. Impedimetric studies revealed that the gene sensor displays linear response in a wide range of target DNA concentration (10-16 M to 10-6 M) with a detection limit of 0.1 fM. The studies on the cross-reactivity to other water-borne pathogens show that the bioelectrode is highly specific. Graphical abstractSchematic illustration for fabrication of nucleic acid biosensor for E. coli DNA detection using an ITO electrode modified with siloxane-functionalized zinc oxide (ZnO) nanorods and carboxylated graphene nanoflakes (c-GNFs).

Effect of Brownian motion on reduced agglomeration of nanostructured metal oxide towards development of efficient cancer biosensor.

We report results of the studies relating to fabrication of nanostructured metal oxide (NMO) based cancer biosensor. With the help of 2D electroactive reduced graphene oxide (RGO), we successfully inhibited the Brownian motion of NMO that led to reduced agglomeration of NMO. The nanostructured hafnium oxide (nHfO2) was used as a model NMO. The reduced agglomeration of nHfO2 was achieved through controlled hydrothermal synthesis and investigated via nanoparticles tracking analysis (NTA). X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM) techniques were used for phase identification as well as morphological analysis of the synthesized nanohybrid (nHfO2@RGO) material. The 3-aminopropyl triethoxysilane (APTES) was used for the functionalization of nHfO2@RGO and electrophoretic deposition (EPD) technique was used for its deposition onto ITO coated glass electrode. Further, antibodies of cancer biomarker (anti-CYFRA-21-1) were immobilized via EDC-NHS chemistry and Bovine serum albumin (BSA) was used for blocking of the non-specific binding sites. The electrochemical response studies of fabricated immunoelectrode (BSA/anti-CYFRA-21-1/APTES/nHfO2@RGO/ITO) revealed higher sensitivity (18.24µAmLng-1), wide linear detection range (0 to 30ngmL-1), with remarkable lower detection limit (0.16ngmL-1). The obtained results showed good agreement with the concentration of CYFRA-21-1 obtained through enzyme linked immunosorbent assay (ELISA) in saliva samples of oral cancer patients.

Controlled deposition of functionalized silica coated zinc oxide nano-assemblies at the air/water interface for blood cancer detection.

We report results of the studies relating to controlled deposition of the amino-functionalized silica-coated zinc oxide (Am-Si@ZnO) nano-assemblies onto an indium tin oxide (ITO) coated glass substrate using Langmuir-Blodgett (LB) technique. The monolayers have been deposited by transferring the spread solution of Am-Si@ZnO stearic acid prepared in chloroform at the air-water interface, at optimized pressure (16 mN/m), concentration (10 mg/ml) and temperature (23 °C). The high-resolution transmission electron microscopic studies of the Am-Si@ZnO nanocomposite reveal that the nanoparticles have a microscopic structure comprising of hexagonal assemblies of ZnO with typical dimensions of 30 nm. The surface morphology of the LB multilayer observed by scanning electron microscopy shows uniform surface of the Am-Si@ZnO film in the nanometer range (<80 nm). These electrodes have been utilized for chronic myelogenous leukemia (CML) detection by covalently immobilizing the amino-terminated oligonucleotide probe sequence via glutaraldehyde as a crosslinker. The response studies of these fabricated electrodes carried out using electrochemical impedance spectroscopy show that this Am-Si@ZnO LB film based nucleic acid sensor exhibits a linear response to complementary DNA (10(-6)-10(-16) M) with a detection limit of 1 × 10(-16) M. This fabricated platform is validated with clinical samples of CML positive patients and the results demonstrate its immense potential for clinical diagnosis.

Quantum dot monolayer for surface plasmon resonance signal enhancement and DNA hybridization detection.

We report results of studies relating to the fabrication of a surface plasmon resonance (SPR)-based nucleic acid sensor for quantification of DNA sequence specific to chronic myelogeneous leukemia (CML). The SPR disk surface has been modified with octadecanethiol self-assembled monolayer followed by deposition of the tri-n-octylphosphine oxide capped cadmium selenide quantum dots (QD) Langmuir monolayer. The deposition is performed via Langmuir-Blodgett (LB) technique. For the sensor chip preparation, covalent immobilization of the thiol-terminated DNA probe sequence (pDNA) using displacement reaction is accomplished. This integrated SPR chip has been used to detect target complementary DNA concentration by monitoring the change in coupling angle via hybridization. It is revealed that this biosensor exhibits high sensitivity (0.7859 m(0)pM(-1)) towards complementary DNA and can be used to detect it in the concentration range, 180 pM to 5 pM with detection limit as 4.21 pM. The results of kinetic studies yield the values of hybridization and dissociation rate constants as 9.6 × 10(4) M(-1) s(-1) and 2.3 × 10(-2) s(-1), respectively, with the equilibrium constant for hybridization as 4.2 × 10(6) M(-1).

Nanostructured zirconia decorated reduced graphene oxide based efficient biosensing platform for non-invasive oral cancer detection.

We report results of the studies relating to fabrication of a non-invasive, label-free and an efficient biosensing platform for detection of the oral cancer biomarker (CYFRA-21-1). One step hydrothermal process was used for uniform decoration of nanostructured zirconia (average particle size 13 nm) on reduced graphene oxide (ZrO2-RGO) to avoid coagulation of the zirconia nanoparticles and to obtain enhanced electrochemical performance of ZrO2-RGO nanocomposite based biosensor. Further, ZrO2-RGO has been functionalized using 3-aminopropyl triethoxy saline (APTES) and electrophoretically deposited on the indium tin oxide coated glass substrate at a low DC potential.The APTES/ZrO2-RGO/ITO electrode exhibits improved heterogeneous electron transfer (more than two times) with respect to that of the APTES/ZrO2/ITO electrode indicating faster electron transfer kinetics. The -NH2 containing APTES/ZrO2-RGO/ITO platform is further biofunctionalized with anti-CYFRA-21-1. The structural and morphological investigations of the ZrO2-RGO based biosensing platform have been accomplished using X-ray diffraction (XRD), electrochemical, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FT-IR) studies. This immunosensor exhibits a wider linear detection range (2-22 ng mL(-1)), excellent sensitivity (0.756 µA mL ng(-1)) and a remarkable lower detection limit of 0.122 ng mL(-1). The observed results have been validated via enzyme linked immunosorbent assay (ELISA).

Anti-epidermal growth factor receptor conjugated mesoporous zinc oxide nanofibers for breast cancer diagnostics.

We report the fabrication of an efficient, label-free, selective and highly reproducible immunosensor with unprecedented sensitivity (femto-molar) to detect a breast cancer biomarker for early diagnostics. Mesoporous zinc oxide nanofibers (ZnOnFs) are synthesized by electrospinning technique with a fiber diameter in the range of 50-150 nm. Fragments of ZnOnFs are electrophoretically deposited on an indium tin oxide glass substrate and conjugated via covalent or electrostatic interactions with a biomarker (anti-ErbB2; epidermal growth factor receptor 2). Oxygen plasma treatment of the carbon doped ZnOnFs generates functional groups (-COOH, -OH, etc.) that are effective for the conjugation of anti-ErbB2. ZnOnFs without plasma treatment that conjugate via electrostatic interactions were also tested for comparison. Label-free detection of the breast cancer biomarker by this point-of-care device is achieved by an electrochemical impedance technique that has high sensitivity (7.76 kΩ µM(-1)) and can detect 1 fM (4.34 × 10(-5) ng mL(-1)) concentration. The excellent impedimetric response of this immunosensor provides a fast detection (128 s) in a wide detection test range (1.0 fM-0.5 µM). The oxy-plasma treated ZnOnF immunoelectrode shows a higher association constant (404.8 kM(-1) s(-1)) indicating a higher affinity towards the ErbB2 antigen compared to the untreated ZnOnF immunoelectrode (165.6 kM(-1) s(-1)). This sensor is about an order of magnitude more sensitive than the best demonstrated in the literature based on different nanomaterials and about three orders of magnitude better than the ELISA standard for breast cancer biomarker detection. This proposed point-of-care cancer diagnostic offers several advantages, such as higher stability, rapid monitoring, simplicity, cost-effectiveness, etc., and should prove to be useful for the detection of other bio- and cancer markers.

Biofunctionalized Nanostructured Zirconia for Biomedical Application: A Smart Approach for Oral Cancer Detection.

Results of the studies are reported relating to application of the silanized nanostructured zirconia, electrophoretically deposited onto indium tin oxide (ITO) coated glass for covalent immobilization of the monoclonal antibodies (anti-CYFRA-21-1). This biosensing platform has been utilized for a simple, efficient, noninvasive, and label-free detection of oral cancer via cyclic voltammetry technique. The results of electrochemical response studies conducted on bovine serum albumin (BSA)/anti-CYFRA-21-1/3-aminopropyl triethoxy silane (APTES)/ZrO2/ITO immunoelectrode reveal that this immunoelectrode can be used to measure CYFRA-21-1 (oral cancer biomarker) concentration in saliva samples, with a high sensitivity of 2.2 mA mL ng-1, a linear detection range of 2-16 ng mL-1, and stability of six weeks. The results of these studies have been validated via enzyme-linked immunosorbent assay.

Lipid-lipid interactions in aminated reduced graphene oxide interface for biosensing application.

A label-free biosensor based on antiapolipoprotein B 100 functionalized-aminated reduced graphene oxide interface has been fabricated for detection of low density lipoprotein (LDL or lipid) cholesterol. The aminated reduced graphene oxide (NH2-rGO) based electrode surface is covalently functionalized with antiapolipoprotein B 100 (AAB or lipid) using EDC/NHS coupling chemistry. The lipid-lipid interactions at the NH2-rGO electrode surface have been investigated using electrochemical impedance spectroscopic technique. The structural and morphological investigations of NH2-rGO based immunosensor have been accomplished via transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, UV-visible, and electrochemical techniques. The impedimetric response of the proposed immunosensor shows excellent sensitivity (612 Ω mg(-1) dL cm(-2)), a response time of 250 s, and a low detection limit of 5 mg/dL of LDL molecules. The association, dissociation, and equilibrium rate constants for this immunoelectrode are found to be 1.66 M(-1) s(-1), 0.6 s(-1), and 2.77 M(-1), respectively. The long-term stability and excellent reproducibility of the proposed immunosensor indicates a suitable platform for detection of LDL or lipid molecules. This immunosensor provides an efficient platform for analysis of the antigen-antibody interactions of lipid molecules.

Quantum dots self assembly based interface for blood cancer detection.

Results of the studies related to fabrication of sensitive electrochemical biosensor using an interface based on quantum dots (QDs) self-assembly is reported. The QDs assembly is sought to provide improved fundamental characteristics to the electrode interface in terms of electroactive surface area, diffusion coefficient, and electron transfer kinetics. This QDs modified electrode has been utilized to serve as a transducer surface for covalent immobilization of chronic myelogenous leukemia (CML) specific probe oligonucleotide, designed from the BCR-ABL fusion gene. The electrochemical characteristics of this biosensor toward various designed synthetic oligonucleotides reveal a significant enhancement in its mismatch discrimination capability compared to the biosensing assay without QDs under similar experimental conditions. The sensing characteristics of this biosensor offer a potential for detection of target oligonucleotide at a concentration as low as 1.0 pM. Furthermore, the PCR-amplified CML-positive patient samples with various BCR-ABL transcript ratios can be electrochemically distinguished from healthy samples, indicating promising application of the QDs based biosensor for clinical investigations.

Cationic poly(lactic-co-glycolic acid) iron oxide microspheres for nucleic acid detection.

Herein, we envisage the possibility of preparing stable cationic poly(lactic-co-glycolic acid) (PLGA) microspheres encapsulating the iron oxide nanoparticles (IONPs; 8-12 nm). The IONPs are incorporated into PLGA in organic phase followed by microsphere formation and chitosan coating in aqueous medium via nano-emulsion technique. The average size of the microspheres, as determined by dynamic light scattering are about 310 nm, while the zeta potential for the composite remains near 35 mV at pH 4.0. These microspheres are electrophoretically deposited onto indium tin oxide (ITO)-coated glass substrate used as cathode and parallel platinum plate as the counter electrode. This platform is utilized to fabricate a DNA biosensor, by immobilizing a probe sequence specific to Escherichia coli. The bioelectrode shows a surface-controlled electrode reaction with the electron transfer coefficient (α) of 0.64 and charge transfer rate constant (k(s)) of 61.73 s(-1). Under the optimal conditions, this biosensor shows a detection limit of 8.7 × 10(-14) M and is found to retain about 81% of the initial activity after 9 cycles of use.

Fundamentals and application of ordered molecular assemblies to affinity biosensing.

Organization of biomolecules in two/three dimensional assemblies has recently aroused much interest in nanobiotechnology. In this context, the development of techniques for controlling spatial arrangement and orientation of the desired molecules to generate highly-ordered nanostructures in the form of a mono/multi layer is considered highly significant. The studies of monolayer films to date have focused on three distinct methods of preparation: (i) the Langmuir-Blodgett (LB) technique, involving the transfer of a monolayer assembled at the gas-liquid interface; (ii) self-assembly at the liquid-solid interface, based on spontaneous adsorption of desired molecules from a solution directly onto a solid surface; and (iii) Layer-by-layer (LBL) self-assembly at a liquid-solid interface, based on inter-layer electrostatic attractions for fabrication of multilayers. A variety of monolayers have been utilized to fabricate biomolecular electronic devices including biosensors. The composition of a monolayer based matrix has been found to influence the activity(ies) of biomolecule(s). We present comprehensive and critical analysis of ordered molecular assemblies formed by LB and self-assembly with potential applications to affinity biosensing. This critical review on fundamentals and application of ordered molecular assemblies to affinity biosensing is likely to benefit researchers working in this as well as related fields of research (401 references).

Self-assembled monolayer based impedimetric platform for food borne mycotoxin detection.

A self-assembled monolayer (SAM) of 11-amino-1-undecanethiol (AUT) has been fabricated onto a gold (Au) substrate to co-immobilize anti-ochratoxin-A antibodies (AO-IgGs) and bovine serum albumin (BSA) to detect food borne mycotoxin [i.e., ochratoxin-A (OTA)]. AUT/Au electrode, AO-IgGs/AUT/Au immunoelectrode and BSA/IgGs/AUT/Au immunoelectrode have been characterized using scanning electron microscopy (SEM) and electrochemical studies such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Electrochemical studies reveal that the AUT-SAM with NH2 groups provide favorable conditions to immobilize AO-IgGs with better orientation, resulting in enhanced electron transport to obtain improved sensing characteristics. The EIS response studies of the BSA/AO-IgGs/AUT/Au immunoelectrode obtained as a function of OTA concentration reveal that the value of the charge transfer resistance (RCT) increases with increased OTA concentration. The BSA/AO-IgGs/AUT/Au immunoelectrode exhibits linearity over 0.5-6.0 ng/dl, detection limit of 0.08 ng/dl using 3σb/m criteria, response time of 30 s and sensitivity of ∼36.83 Ω/ng dl(-1) cm(-2) with a regression coefficient of 0.999. Attempts have been made to monitor the change in RCT of BSA/AO-IgGs/AUT/Au immunoelectrode on addition of coffee samples.

Preparation, characterization and application of polyaniline nanospheres to biosensing.

Polyaniline nanospheres (PANI-NS) prepared by morphological transformation of micelle polymerized camphorsulfonic acid (CSA) doped polyaniline nanotubes (PANI-NT) in the presence of ethylene glycol (EG) have been characterized by X-ray diffraction, atomic force microscopy, transmission electron microscopy, scanning electron microscopy, Fourier transform infra-red and UV-Visible spectroscopy. A PANI-NS (60-80 nm) film deposited onto an indium-tin-oxide (ITO) coated glass plate by the solution casting method has been utilized for covalent immobilization of biomolecules (cholesterol oxidase (ChOx)) viaN-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) chemistry for fabrication of a cholesterol biosensor. The ChOx/PANI-NS/ITO bioelectrode detects cholesterol in the concentration range of 25 to 500 mg dL(-1) with sensitivity of 1.3 x 10(-3) mA mg(-1) dL and regression coefficient of 0.98. Further, this PANI-NS based bioelectrode shows fast response time (10 s), low Michaelis-Menten constant (2.5 mM) and shelf-life of 12 weeks. The spherical nanostructure observed in the final morphology of the PANI-NS film is attributed to hydrogen bonding interactions between PANI-NT and EG.

Polyaniline/carbon nanotubes platform for sexually transmitted disease detection.

Polyaniline/carbon nanotubes composite (PANI-CNT) electrochemically deposited onto indium-tin-oxide (ITO) coated glass plate has been utilized for Neisseria gonorrhoeae detection by immobilizing 5'-amino-labeled Neisseria gonorrhoeae probe (aDNA) using glutaraldehyde as a cross-linker. PANI-CNT/ITO and aDNA-Glu-PANI-CNT/ITO electrodes have been characterized using scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). This bioelectrode can be used to detect N. gonorrhoeae using methylene blue (MB) as redox indicator with response time of 60 s and stability of about 75 days when stored under refrigerated conditions. DPV studies reveal that this bioelectrode can detect complementary DNA concentration from 1 x 10(-6) M to 1 x 10(-17) M with detection limit of 1.2 x 10(-17) M. Further, this bioelectrode (aDNA-Glu-PANI-CNT/ITO) exhibits specificity toward N. gonorrhoeae species and shows negative response with non-Neisseria gonorrhoeae Neisseria species (NgNS) and other gram negative bacteria (GNB).

A nanostructured cerium oxide film-based immunosensor for mycotoxin detection.

Rabbit-immunoglobulin antibodies (r-IgGs) and bovine serum albumin (BSA) have been immobilized onto sol-gel-derived nanostructured cerium oxide (nanoCeO(2)) film fabricated onto an indium-tin-oxide (ITO) coated glass plate to detect ochratoxin-A (OTA). Broad reflection planes obtained in x-ray diffraction (XRD) patterns reveal the formation of CeO(2) nanostructures. Electrochemical studies reveal that nanoCeO(2) particles provide an increased electroactive surface area for loading of r-IgGs with desired orientation, resulting in enhanced electron communication between r-IgGs and electrode. BSA/r-IgGs/nano CeO(2)/ITO immunoelectrode exhibits improved characteristics such as linear range (0.5-6 ng dl(-1)), low detection limit (0.25 ng dl(-1)), fast response time (30 s) and high sensitivity (1.27 microA ng(-1) dl(-1) cm(-2)). The high value of the association constant (K(a), 0.9 x 10(11) l mol(-1)) indicates the high affinity of the BSA/r-IgGs/nanoCeO(2)/ITO immunoelectrode to OTA.