Ultrasensitive Biosensing on the Zepto-Molar Level

Detection of analytes on the zepto-molar (10^-^2^1M) level has been achieved using a field-effect bio-detector. By applying a gating voltage to enzymes immobilized on the working electrode of the detector, amplification of the biocatalytic current was observed. The amplification is attributed to the modification of the tunnel barrier between the enzyme and the electrode by the gating voltage-induced electric field which exists at the solution-electrode interface. The detection was demonstrated with the glucose oxidase (GOx)-glucose and alcohol dehydrogenase (ADH)-ethanol biocatalytic systems. Glucose at zepto-molar level was detected with zepto-molar detection resolution. Equivalently, 30 glucose molecules present in the sample were detected and the detection system responded distinctively to the incremental change in the number of glucose molecules in unit of 30 molecules. The enzyme\u27s biospecificity was also preserved in the presence of the applied field. We present possible processes that could give rise to the electrical charges required to produce the observed current level

Field-Effect Amperometric Immuno-Detection of Protein Biomarker

The field-effect enzymatic detection technique has been applied to the amperometric immunoassay of the cancer biomarker, carcinoma antigen 125 (CA 125). The detection adopted a reagentless approach, in which the analyte, CA 125, was immobilized on the detecting electrode, which was modified using carbon nanotubes, and the detection signal was obtained by measuring the reduction peak current of the enzyme that was used to label the antibody. A gating voltage was applied to the detecting electrode, inducing increase in the signal current and therefore providing amplification of the detection signal. The voltage-controlled signal amplification of the detection system has increased the sensitivity and lowered the detection limit of the system. A detection limit of 0.9U/ml was obtained in the work

Ultrasensitive Biosensing on the Zepto-Molar Level

Detection of analytes on the zepto-molar (10^-^2^1M) level has been achieved using a field-effect bio-detector. By applying a gating voltage to enzymes immobilized on the working electrode of the detector, amplification of the biocatalytic current was observed. The amplification is attributed to the modification of the tunnel barrier between the enzyme and the electrode by the gating voltage-induced electric field which exists at the solution-electrode interface. The detection was demonstrated with the glucose oxidase (GOx)-glucose and alcohol dehydrogenase (ADH)-ethanol biocatalytic systems. Glucose at zepto-molar level was detected with zepto-molar detection resolution. Equivalently, 30 glucose molecules present in the sample were detected and the detection system responded distinctively to the incremental change in the number of glucose molecules in unit of 30 molecules. The enzyme\u27s biospecificity was also preserved in the presence of the applied field. We present possible processes that could give rise to the electrical charges required to produce the observed current level

Detection of prostate specific antigen in serum at the femto-gram per milliliter level using the intrinsic amplification of a field-effect enzymatic immuno-sensing system

Ultrasensitive detection of prostate specific antigen (PSA) has been achieved by applying the field-effectenzymatic detection (FEED) technique to the sandwich immuno-sensing technique. The voltage-controlled intrinsic amplification provided by FEED enabled the detection of PSA contained in serumon the femto-gram/mL level. Two electrochemical approaches used to obtain the amperometric detec-tion signal resulted in similar detection limits and sensitivities. The lowest PSA detection limit achievedwas 27 fg mL-1. The high selectivity of the detection system was reflected in the fact that PSA detectionwas successful on the fg mL-1level, where biological substances other than PSA had a 1-million-foldhigher concentration. Electron transfer through the immunological sandwich nanostructure has beenobserved in the detection of biomarkers. However, our results showed that electron transfer through thenanostructure could be controlled using an external voltage, leading to an ultralow detection limit for PSA

Detection of prostate specific antigen in serum at the femto-gram per milliliter level using the intrinsic amplification of a field-effect enzymatic immuno-sensing system

Ultrasensitive detection of prostate specific antigen (PSA) has been achieved by applying the field-effectenzymatic detection (FEED) technique to the sandwich immuno-sensing technique. The voltage-controlled intrinsic amplification provided by FEED enabled the detection of PSA contained in serumon the femto-gram/mL level. Two electrochemical approaches used to obtain the amperometric detec-tion signal resulted in similar detection limits and sensitivities. The lowest PSA detection limit achievedwas 27 fg mL-1. The high selectivity of the detection system was reflected in the fact that PSA detectionwas successful on the fg mL-1level, where biological substances other than PSA had a 1-million-foldhigher concentration. Electron transfer through the immunological sandwich nanostructure has beenobserved in the detection of biomarkers. However, our results showed that electron transfer through thenanostructure could be controlled using an external voltage, leading to an ultralow detection limit for PSA

Mirror of Atiyah flop in symplectic geometry and stability conditions

We study the mirror operation of the Atiyah flop in symplectic geometry. We formulate the operation for a symplectic manifold with a Lagrangian fibration. Furthermore we construct geometric stability conditions on the derived Fukaya category of the deformed conifold and study the action of the mirror Atiyah flop on these stability conditions.Comment: v2: 45 pages, 18 figures; revised expositio

Mediator-less immunodetection with voltage-controlled intrinsic amplification for ultrasensitive and rapid detection of microorganism pathogens

A mediator-less immunodetection method for microorganisms is realized by incorporating the newly developed field-effect enzymatic detection (FEED) technique with the conventional electrochemical immunosensing approach. The gating voltage of FEED facilitates the transduction of electrical signal through the bulky immune complex so that the detection does not rely on the use of mediators or other diffusional substances. The voltage-controlled intrinsic amplification provided by the detection system allows detection in low-concentration samples without target pre-enrichment, leading to ultrasensitive and rapid detection. The detection approach is demonstrated with E. coliO157:H7, a model microorganism, in milk with an estimated detection limit of 20 CFU mL−1 (where CFU is a colony-forming unit) without performing sample pre-enrichment and centrifugation of sample followed by the resuspension of the pellet in a buffer solution, resulting in a significantly shortened assay time of 67 min. Optimizing the gating voltage resulted in the detection of 12 CFU mL−1 of the bacterium in milk. The novel detection approach can be used as a detection platform for ultrasensitive, specific and rapid detection of microorganism pathogens

Preserved Enzymatic Activity of Glucose Oxidase Immobilized on Unmodified Electrodes for Glucose Detection

Glucose sensing electrodes have been realized by immobilizing glucose oxidase (GOx) on unmodified edge plane of highly oriented pyrolytic graphite (epHOPG) and the native oxide of heavily doped silicon (SiO2/Si). Both kinds of electrode show direct interfacial electron transfer due to the redox process of the immobilized GOx. The measured formal potential of the redox process agrees with that of the native enzyme, suggesting that the immobilized GOx has retained its enzymatic activity. The electron transfer rates of the GOx immobilized electrode are 2s−1 for GOx/epHOPG electrode and 7.9s−1 for GOx/SiO2/Si electrode, which are greater than those for which GOx is immobilized on modified electrodes, probably due to the fact that the enzyme makes direct contact to electrode surface. The preservation of the enzymatic activity of the immobilized GOx has been confirmed by observing the response of the GOx/epHOPG and GOx/SiO2/Si electrodes to glucose with a detection limit of 0.050mM. The response signals the catalyzed oxidation of glucose and, therefore, confirms that the immobilized GOx retained its enzymatic activity. The properties of the electrode as a glucose sensor are presented

Preserved Enzymatic Activity of Glucose Oxidase Immobilized on Unmodified Electrodes for Glucose Detection

Glucose sensing electrodes have been realized by immobilizing glucose oxidase (GOx) on unmodified edge plane of highly oriented pyrolytic graphite (epHOPG) and the native oxide of heavily doped silicon (SiO2/Si). Both kinds of electrode show direct interfacial electron transfer due to the redox process of the immobilized GOx. The measured formal potential of the redox process agrees with that of the native enzyme, suggesting that the immobilized GOx has retained its enzymatic activity. The electron transfer rates of the GOx immobilized electrode are 2s−1 for GOx/epHOPG electrode and 7.9s−1 for GOx/SiO2/Si electrode, which are greater than those for which GOx is immobilized on modified electrodes, probably due to the fact that the enzyme makes direct contact to electrode surface. The preservation of the enzymatic activity of the immobilized GOx has been confirmed by observing the response of the GOx/epHOPG and GOx/SiO2/Si electrodes to glucose with a detection limit of 0.050mM. The response signals the catalyzed oxidation of glucose and, therefore, confirms that the immobilized GOx retained its enzymatic activity. The properties of the electrode as a glucose sensor are presented