A quantitative study of detection mechanism of a label-free impedance biosensor using ultrananocrystalline diamond microelectrode array (original) (raw)
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Analyst, 2007
The integration of biological molecules with semiconducting materials such as silicon and diamond has great potential for the development of new types of bioelectronic devices, such as biosensors and bioactuators. We have investigated the electrical properties of the antibodyantigen modified diamond and silicon surfaces using electrical impedance spectroscopy (EIS). Frequency dependent measurements at the open-circuit potential show: (a) significant changes in impedance at frequency .10 4 Hz when the surface immobilized IgG was exposed to anti-IgG, and (b) only little or no change when exposed to anti-IgM. Mott-Schottky measurements at high frequency (200 kHz) show that the impedance is dominated by the space charge layer of the semiconducting substrates. Silicon surfaces modified in a similar manner to the diamond surface are compared; n-type and p-type samples show complementary behavior, as expected for a field effect. We also show it is possible to directly observe antigen-antibody interaction at a fixed frequency in real time, and with no additional labeling.
Diamond Based Biosensors: Surface-Fluid Interaction Issues
Procedia Chemistry, 2012
The interaction of nanocrystalline (NCD) and microcrystalline (MCD) p-type semiconducting diamond surfaces with phosphate buffer saline (PBS), simulated body fluid (SBF) and bovine serum albumin (BSA) solutions under applied electric potentials is the main subject of this work. The effect of these fluids on the electrical resistivity of the diamond surface is evaluated. Furthermore, the interaction effects of these surfaces with BSA containing SBF solution during 30 days, is addressed. The electrical measurements have shown that the electrical current passing through the NCD samples is influenced by the fluid's ionic composition, whereas no variation was detected for the MCD samples. Both NCD and MCD surfaces favor the formation of a deposit layer after 30 days in contact with SBF+BSA solution. This deposit is mainly composed of Ca, P, Mg and O, containing also a significant concentration of BSA proteins.
Electroanalysis, 2003
Impedance spectroscopy is a rapidly developing electrochemical technique for the characterization of biomaterialfunctionalized electrodes and biocatalytic transformations at electrode surfaces, and specifically for the transduction of biosensing events at electrodes or field-effect transistor devices. The immobilization of biomaterials, e.g., enzymes, antigens/antibodies or DNA on electrodes or semiconductor surfaces alters the capacitance and interfacial electron transfer resistance of the conductive or semiconductive electrodes. Impedance spectroscopy allows analysis of interfacial changes originating from biorecognition events at electrode surfaces. Kinetics and mechanisms of electron transfer processes corresponding to biocatalytic reactions occurring at modified electrodes can be also derived from Faradaic impedance spectroscopy. Different immunosensors that use impedance measurements for the transduction of antigen-antibody complex formation on electronic transducers were developed. Similarly, DNA biosensors using impedance measurements as readout signals were developed. Amplified detection of the analyte DNA using Faradaic impedance spectroscopy was accomplished by the coupling of functionalized liposomes or by the association of biocatalytic conjugates to the sensing interface providing biocatalyzed precipitation of an insoluble product on the electrodes. The amplified detections of viral DNA and single-base mismatches in DNA were accomplished by similar methods. The changes of interfacial features of gate surfaces of field-effect transistors (FET) upon the formation of antigen-antibody complexes or assembly of protein arrays were probed by impedance measurements and specifically by transconductance measurements. Impedance spectroscopy was also applied to characterize enzymebased biosensors. The reconstitution of apo-enzymes on cofactor-functionalized electrodes and the formation of cofactor-enzyme affinity complexes on electrodes were probed by Faradaic impedance spectroscopy. Also biocatalyzed reactions occurring on electrode surfaces were analyzed by impedance spectroscopy. The theoretical background of the different methods and their practical applications in analytical procedures were outlined in this article.
Customized impedance spectroscopy device as possible sensor platform for biosensor applications
Physica Status Solidi (A) Applications and Materials
A new impedance spectroscopy unit is developed, fully customized to become a vital part of label free biosensor arrays with possible applications in DNA and protein sensing. Test measurements are conducted to explore the accuracy and specificity of the system, both under electronic lab conditions as well as under wet cell conditions with synthetic-diamond based sensor electrodes. The impedance of seven resistors was monitored for 17 h and a maximum error <0.02% was found. Furthermore, the impedance of PBS at different concentrations was monitored for 60 min per concentration and a different impedance for each concentration was detected. The impedance is also monitored for NaOH, PBS and nuclease free water at different temperatures with a total duration of 60 min per fluid. Systematically different impedances for each temperature per fluid were found and the temperature coefficients were determined. All test measurements lead to results well within specification.
Nanocrystalline diamond film for biosensor applications
Diamond and Related Materials, 2010
In this study, we have developed a novel capacitive biosensor based on interdigitated gold nanodiamond (GID-NCD) electrode for detection of C-reactive protein (CRP) antigen. CRP is one of the plasma proteins known as acute-phase proteins and its levels rise dramatically during inflammatory processes occurring in the body. It has been reported that CRP in serum can be used for risk assessment of cardiovascular diseases. The antibodies immobilization were confirmed by fourier transform spectroscopy (FTIR) and contact angle measurements. In this capacitive biosensor, nanocrystalline diamond acting as a dielectric layer between the electrodes. The CRP antigen detection was performed by capacitive/dielectric-constant measurements. Our results showed that the response of NCD-based capacitive-based biosensor for CRP antigen was dependent on both concentration (25-800 ng/ml) as well as frequency (50-350 MHz). Furthermore, using optimized conditions, the biosensors developed in this study can be potentially used for detection of elevated level of risk markers protein in suspected subjects for early diagnosis of disease.
Biosensors & bioelectronics, 2016
This paper reports a novel electrochemical impedance spectroscopy (EIS) biosensors that uses magnetic beads trapped in a microwell array to improve the sensitivity of conventional bead-based EIS (BEIS) biosensors. Unloading the previously measured beads by removing the magnetic bar enables the BEIS sensor to be used repeatedly by reloading it with new beads. Despite its recyclability, the sensitivity of conventional BEIS biosensors is so low that it has not attracted much attentions from the biosensor industry. We significantly improved the sensitivity of the BEIS system by introducing of a microwell array that contains two electrodes (a working electrode and a counter electrode) to concentrate the electric field on the surfaces of the beads. We confirmed that the performance of the BEIS sensor in a microwell array using an immunoassay of prostate specific antigen (PSA) in PBS buffer and human plasma. The experimental results showed that a low concentration of PSA (a few tens or hun...
Boron doped diamond thin films for the electrochemical detection of SARS-CoV-2 S1 protein
Diamond and Related Materials, 2021
Amidst a global pandemic, a precise and widely accessible rapid detection method is needed for accurate diagnosis and contact tracing. The lack of this technology was exposed through the outbreak of SARS-CoV-2 beginning in 2019. This study sets the foundation for the development of a boron doped diamond (BDD)based impedimetric sensor. While specifically developed for use in the detection of SARS-CoV-2, this technology uses principles that could be adapted to detect other viruses in the future. Boron doped polycrystalline diamond electrodes were functionalized with a biotin-streptavidin linker complex and biotinylated anti-SARS-CoV-2 S1 antibodies. Electrodes were then incubated with the S1 subunit of the SARS-CoV-2 spike surface protein, and an electrical response was recorded using the changes to the electrode's charge transfer resistance (R ct), measured through electrochemical impedance spectroscopy (EIS). Detectable changes in the R ct were observed after 5-min incubation periods with S1 subunit concentrations as low as 1 fg/mL. Incubation with Influenza-B Hemagglutinin protein resulted in minimal change to the R ct , indicating specificity of the BDD electrode for the S1 subunit of SARS-CoV-2. Detection of the S1 subunit in a complex (cell culture) medium was also demonstrated by modifying the EIS protocol to minimize the effects of sample matrix binding. BDD films of varying surface morphologies were investigated, and material characterization was used to give insight into the microstructure-performance relationship of the BDD sensing surface.