Article

Controlled Carbon Nanotube layers for Impedimetric Immunosensors: High performance label free detection and quantification of Anti-Cholera Toxin antibody

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Abstract

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.

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... For example, culture method can take up to 8 days to get the results while, according to literature [4], cholera kills within 12 to 24 h if not treated. There are many other methods such as enzyme-linked immunosorbent assay [5], polymerase chain reaction (PCR) [6,7], and electrochemical methods [8][9][10][11][12][13][14][15]. Of all the aforementioned techniques, electrochemistry gives excellent promise for fast detection, simplicity, sensitivity, selectivity, and ability to miniaturize the process for the development of hand-held point-of-care diagnostic devices. ...
... Thus, several researchers have reported several electrode platforms for the immobilization of cholera immunosensors. These electrode platforms include graphene [8], liposomes and poly(3,4ethylenedioxythiophene)-coated carbon nanotubes [9], dendrimers integrated with gold nanoparticles [10], zinc oxide [11], polyacrylonitrile (PAN) nanofibres [12], copper (II) complex with polypyrrole-nitrilotriacetic acid on carbon nanotubes [13], carbon nanofibres (CNF) [14], and onionlike carbon modified with PAN (OLC-PAN) [15]. In electrochemistry, to be redox-active, a material must be able to lose or gain electrons (i.e., conducting), while a redox-inactive (or redox-silent) material is insulating. ...
... Bovine serum albumin (BSA) is an important protein which is popularly used to block non-specific sites in the immunosensing platforms [9][10][11][12][13][14][15][16][17]. In electrochemical immunosensors, the sensing mechanism is generally dominated by capacitance (i.e., non-Faradaic detection) due to the redox-inactivity of the electrode platform upon which the antibody or antigen is immobilized. ...
Article
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This work investigates how bovine serum albumin (BSA), a commonly used protein in the fabrication of electrochemical immunosensors, can impact on the sensitivity of detection when integrated with antibody (Ab) pre-encapsulated with (i) insulating polyacrylonitrile (PAN) fibre (i.e., GCE-PAN-Ab-BSA immunosensor) or (ii) conducting PAN-grafted iron (II) phthalocyanine (FePc) (i.e., GCE-PAN@FePc-Ab-BSA immunosensor), using Vibrio cholerae toxin as a case study bioanalyte. Both immunosensors show different charge-transfer kinetics that strongly impact on their immunosensitive detection. From the electrochemical data, GCE-PAN-Ab-BSA is more insulating with the presence of BSA, while the GCE-PAN@FePc-Ab-BSA is more conducting with BSA. The CV of the GCE-PAN-Ab-BSA is dominated by radial diffusion process, while that of the GCE-PAN@FePc-Ab-BSA is planar diffusion process. The behaviour of GCE-PAN@FePc-Ab-BSA has been associated with the facile coordination of BSA and FePc that permits co-operative charge-transport of the redox probe, while that of the GCE-PAN-Ab-BSA is related to the interaction-induced PAN-BSA insulating state that suppresses charge-transport. As a consequence of these different interaction processes, GCE-PAN-Ab-BSA immunosensor provides higher electroanalytical performance for the detection of Vibrio cholerae toxin (with sensitivity of 16.12 Ω/log [VCT, g/mL] and limit of detection (LoD) of 3.20 × 10⁻¹³ g/mL compared to those of the GCE-PAN@FePc-Ab-BSA (4.16 Ω/log (VCT, g mL⁻¹) and 2.00 × 10⁻¹² g/mL). The study confirms the need for a thorough understanding of the physico-chemistries of the electrode platforms for the construction of immunosensors. Although this work is on immunosensors for cholera infection, it may well apply to other immunosensors. Graphical Abstract
... Label-free and single-immunoreaction biosensors have been reported using electrode substrates nanostructured with PPI-AuNP nanocomposite [81], PANnf's [82], ZnO NPs [83], CNTs [84] and CNFs [85] for Vibrio cholerae [82] and its characteristic toxins [81,82,85] or antibodies [84]. Although all these immunosensors exhibit good analytical characteristics in terms of sensitivity and selectivity, none has been applied to the analysis of real samples. ...
... Label-free and single-immunoreaction biosensors have been reported using electrode substrates nanostructured with PPI-AuNP nanocomposite [81], PANnf's [82], ZnO NPs [83], CNTs [84] and CNFs [85] for Vibrio cholerae [82] and its characteristic toxins [81,82,85] or antibodies [84]. Although all these immunosensors exhibit good analytical characteristics in terms of sensitivity and selectivity, none has been applied to the analysis of real samples. ...
Article
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The excellent capabilities demonstrated over the last few years by electrochemical affinity biosensors should be largely attributed to their coupling with particular nanostructures including dendrimers, DNA-based nanoskeletons, molecular imprinted polymers, metal-organic frameworks, nanozymes and magnetic and mesoporous silica nanoparticles. This review article aims to give, by highlighting representative methods reported in the last 5 years, an updated and general overview of the main improvements that the use of such well-ordered nanomaterials as electrode modifiers or advanced labels confer to electrochemical affinity biosensors in terms of sensitivity, selectivity, stability, conductivity and biocompatibility focused on food and environmental applications, less covered in the literature than clinics. A wide variety of bioreceptors (antibodies, DNAs, aptamers, lectins, mast cells, DNAzymes), affinity reactions (single, sandwich, competitive and displacement) and detection strategies (label-free or label-based using mainly natural but also artificial enzymes), whose performance is substantially improved when used in conjunction with nanostructured systems, are critically discussed together with the great diversity of molecular targets that nanostructured affinity biosensors are able to quantify using quite simple protocols in a wide variety of matrices and with the sensitivity required by legislation. The large number of possibilities and the versatility of these approaches, the main challenges to face in order to achieve other pursued capabilities (development of antifouling, continuous operation, wash-, calibration- and reagents-free devices, regulatory or Association of Official Analytical Chemists, AOAC, approval) and decisive future actions to achieve the commercialization and acceptance of these devices in our daily routine are also noted at the end.
... Solution processing of CNT-based films, therefore, offers great potential for the cost-effective preparation of devices such as flexible electrodes, supercapacitors, biosensors, and biofuel cells [23][24][25][26]. For the construction of bioelectrodes, the simple drop-casting of CNTs from aqueous and non-aqueous suspensions represents the most commonly employed method [7,27]. ...
... Solution processing of CNT-based films, therefore, offers great potential for the cost-effective preparation of devices such as flexible electrodes, supercapacitors, biosensors, and biofuel cells [23][24][25][26]. For the construction of bioelectrodes, the simple drop-casting of CNTs from aqueous and nonaqueous suspensions represents the most commonly employed method [7,27]. ...
Article
Full-text available
We report a simple, versatile, and rapid method for the fabrication of optically-transparent large-area carbon nanotube (CNT) films via flotation assembly. After solvent-induced assembly, floating films were transferred to a flat supporting substrate to form conductive and transparent CNT film electrodes. The resulting electrodes, with uniform 40 ± 20 nm multi-walled CNT (MWCNT) layers, were characterized by electrochemical and microscopy methods. The flotation method does not require specialized thin-film instrumentation and avoids the need for surfactants and pre-oxidized CNTs which can hamper electrochemical performance. A proof-of-concept nanostructured bioelectrode demonstrating high sensitivity for glucose was developed with an electropolymerized poly(pyrene-adamantane) layer for host–guest immobilization of active β-cyclodextrin tagged GOx enzymes. The polymer provides pyrene groups for cross-linking to CNTs and pendant adamantane groups for binding the β-cyclodextrin groups of the tagged enzyme. This demonstration offers a new approach for the preparation of stable and transparent CNT film electrodes with attractive electrochemical properties towards future photobio- and bio-electrochemical fuel cells, electrochemical sensors, and electroanalysis.
... Because of the WHO's goal to increase the global capacity to monitor and control the major epidemics and pandemic threats, sensitive, rapid, and predictable detection of specific antibodies by biosensors has become particularly important for clinical serodiagnosis [3,5,6,55,[82][83][84][85][86][87][88][89][90]. ...
... Using the specific antigen as an MRE and CNTs to enhance the electric properties, electrical changes could be measured at antibody concentration as low as 6~50 pg L −1 , and as high as~70 µg L −1 . Recently, another EIS-based immunosensor was also developed based on CNTs deposits [83]. The bioreceptor unit, biotin-modified cholera toxin B subunit, was immobilized with the nitrilotriacetic acid-Cu(II) complex. ...
Article
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Biosensors for proteins have shown attractive advantages compared to traditional techniques in clinical laboratory diagnosis. In virtue of modern fabrication modes and detection techniques, various immunosensing platforms have been reported on basis of the specific recognition between antigen-antibody pairs. In addition to profit from the development of nanotechnology and molecular biology, diverse fabrication and signal amplification strategies have been designed for detection of protein antigens, which has led to great achievements in fast quantitative and simultaneous testing with extremely high sensitivity and specificity. Besides antigens, determination of antibodies also possesses great significance for clinical laboratory diagnosis. In this review, we will categorize recent immunosensors for proteins by different detection techniques. The basic conception of detection techniques, sensing mechanisms, and the relevant signal amplification strategies are introduced. Since antibodies and antigens have an equal position to each other in immunosensing, all biosensing strategies for antigens can be extended to antibodies under appropriate optimizations. Biosensors for antibodies are summarized, focusing on potential applications in clinical laboratory diagnosis, such as a series of biomarkers for infectious diseases and autoimmune diseases, and an evaluation of vaccine immunity. The excellent performances of these biosensors provide a prospective space for future antibody-detection-based disease serodiagnosis.
... Afterwards, the GCE (∅ ¼ 3 mm) were modified with multi walled carbon nanotubes (CNT). A film of controlled thickness and presenting a good surface homogeneity was deposited on GCE as described in our previous work [31]. The film obtained by this method had a thickness of 4 mm which was checked each time by confocal laser microscopy. ...
... The characteristics of the carbon nanotube film in terms of thickness, roughness, and conductivity are presented in our previous work [31]. There, the films show a very good reproducibility at a thickness of 4.0 mm with a roughness of ±0.8 mm and a conductivity of 1.01 S cm À1 . ...
Article
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).
... Based on these properties, CNTs have now been considered to solve the above problems. They often are used as a promising kind of material incorporated into immunosensors in different ways such as biorecognition elements, carriers, as well as reaction supporters [1][2][3]. ...
... Based on polypyrrole-nitrilotriacetic acid (pp-NTA) and Cu 2+ / MWCNTs composite, Palomar et al. reported an impedimetric immunoassay to detect anti-cholera toxin antibody using electrochemical impedance spectroscopy (EIS) as transduction technique [3]. CNTs were functionalized via electrocoating of pp-NTA followed by the formation of a Cu 2+ complex with the NTA functions. ...
Article
Full-text available
This review (with 126 references) summarizes the progress that has been made in the use of carbon nanotubes (CNTs) in immunoassays and immunosensors. Following an introduction into the field, a first large section covers functional group-modified CNTs as carriers for antibodies (with subsections on CNTs modified with amino, carboxy and by various other materials). The next section treats CNTs coupled with inorganic or organic materials as active components (with the use of nanoparticles such as Fe3O4, ZnO, gold) or with indium tin oxide (ITO), NiCoBP, ionic liquids, TiO2 nanosheets, metal clusters; chitosan, polystyrene, polydopamine, graphene, or enzymes. Another section discusses the synergistic effects of CNTs with metals, metal ions, and organic/inorganic materials. Several Tables are presented that give an overview on the wealth of methods and materials. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Schematic presentation of the roles of carbon nanotubes (CNTs) in immunosensors and immunoassays. (I) Functional group-modified CNTs as carriers for antibody; (II) CNTs coupled with metal or organic materials as active component; and (III) Synergistic effects of CNTs with other materials to improve the parameters of immunosensors.
... However, they used sol-gel or drop-casting processes for the modification of the electrode by nanotubes. These techniques may suffer from a lack of control over the properties of the nanostructure formed and new methods have since been developed to allow a better control over the MWCNTs layer production [15]. Therefore the combination of these materials for the detection of complex targets of interest with a well-controlled nanostructure remains to be studied. ...
... Afterwards, the electrodes were rinsed in ethanol for 10 min and then rinsed 10 m in water before being dried with N 2 . Following this procedure, the GE was modified with MWCNTs according to a process presented in our previous work [15]. The first step consists of suspending MWCNTs in H 2 O (5 mg/L). ...
Article
Full-text available
A homemade gold electrode is modified with a carbon nanotubes/gold nanoparticles nanocomposite to perform selective and sensitive electrochemical detection of dengue toxin. This nanostructured composite offers a large specific surface and a reactive interface allowing the immobilization of biological material. Dengue antibodies are immobilized on gold nanoparticles via covalent bonding for dengue toxin detection. The porous tridimensional network of carbon nanotubes and gold nanoparticles enhances the electrochemical signal and the overall performance of the sensor. After optimization, the system exhibits a high sensitivity of − 0.44 ± 0.01 μA per decade with wide linear range between 1 × 10⁻¹² and 1 × 10⁻⁶ g/mL at a working potential of 0.22 V vs Ag/AgCl. The extremely low detection limit (3 × 10⁻¹³ g/mL) ranks this immunosensor as one of the most efficient reported in the literature for the detection of recombinant viral dengue virus 2 NS1. This biosensor also offers good selectivity, characterized by a low response to various non-specific targets and assays in human serum. The outstanding performances and the reproducibility of the system place the biosensor developed among the best candidates for future medical applications and for early diagnosis of dengue fever. Graphical abstract
... These systems were modified with polypyrrole-nitrilotriacetic acid (poly(pyrrole-NTA)) and Cu (II) complex to produce sensor devices. With great sensitivity and easy reproducibility, the cholera sensor showed a promising linear detection range from 10 −13 -10 −5 g mL −1 with a LOD of 10 −13 g mL −1 , which could be a potential sensing platform to detect cholera in the environment [229]. ...
Article
Full-text available
After the COVID-19 pandemic, the development of an accurate diagnosis and monitoring of diseases became a more important issue. In order to fabricate high-performance and sensitive biosensors, many researchers and scientists have used many kinds of nanomaterials such as metal nanoparticles (NPs), metal oxide NPs, quantum dots (QDs), and carbon nanomaterials including graphene and carbon nanotubes (CNTs). Among them, CNTs have been considered important biosensing channel candidates due to their excellent physical properties such as high electrical conductivity, strong mechanical properties, plasmonic properties, and so on. Thus, in this review, CNT-based biosensing systems are introduced and various sensing approaches such as electrochemical, optical, and electrical methods are reported. Moreover, such biosensing platforms showed excellent sensitivity and high selectivity against not only viruses but also virus DNA structures. So, based on the amazing potential of CNTs-based biosensing systems, healthcare and public health can be significantly improved.
... The porous electronic (4) detection of the recognition event. Source: Reproduced from Reference [2]. Reproduced with permission of Elsevier. ...
Article
Nanotechnology is increasingly important in electroanalytical chemistry for the development of attractive biosensing strategies. The analytical performance of electrochemical biosensors can be greatly improved by integration of nanomaterials into their construction. In this sense, carbon nanomaterials play a major role. The use of smart carbon nanomaterials for designing novel electrochemical biosensing systems involves well‐known carbon nanotubes (CNTs) and graphene, as well as other recently emerged carbon nanoforms such as carbon nanohorns, fullerene (C60), graphene quantum dots, and carbon nanoparticles. The great interest in the use of these carbon nanomaterials to construct electrochemical biosensors relies on the exceptional properties of carbon nanomaterials such as large surface area, excellent biological compatibility, relatively ease functionalization and, in some cases, intrinsic electrochemistry. In order to show to both familiar and non‐expert readers the great potentiality of carbon nanostructures and their hybrid materials in electrochemical biosensing, this Chapter outlines the state‐of‐art, current challenges and future perspectives in this field. An updated overview of the carbon nanomaterials employed as electrode modifiers and advanced labels, acting both as carriers for signal elements and electrochemical tracers, in connection with electrochemical affinity biosensors applied to clinical analysis is provided in the chapter.
... However, it is now possible to synthesize these elements in laboratories [19]. Their applications may include detection of proteins [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37], viruses [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56], antibodies [57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74], DNA [75][76][77][78][79][80][81][82][83][84][85][86][87][88][89], drugs [90][91][92][93][94][95][96][97][98][99][100], pesticides [101][102][103][104][105][106][107][108][109][110][111][112][113][114][115][116][117][118][119] and other low molecular weight compounds [120][121][122][123]. ...
... Immunosensors are the sensing platforms based on the specific antigen−antibody binding event. They are commendably established standard biosensing techniques used in clinical disease diagnosis, food safety monitoring, and environmental pollution analysis [208][209][210][211][212]. The recent development of immunoassay methods mostly focused on simplification and automation of the assay procedures, decreasing assay times, increasing sensing sensitivity, and low-volume analysis [213]. ...
Article
This review summarizes the synthesis of gold (Au) and Au-based nanomaterials and their recent advances of application in electrochemical small-molecule sensors, DNA sensors and immunosensors. Au nanoparticles with various shape and size have been synthesized by using physical, chemical, biological, electrochemical and seeding growth methods. In order to broaden the applications and improve the functionality of Au nanoparticles, numerous Au-based nanocomposite materials have been developed, including bimetallic nanoparticles, metal oxide-gold, polymer-gold, carbon nanotube-gold and graphene/graphene oxide-gold nanocomposites. Finally, the application of Au nanoparticles and Au-based nanocomposite materials in electrochemical sensors and their analytical performance were discussed.
... The as-developed biosensor reached a linear-dependent concentration response in the range from 0.1 pg/mL to 0.1 µg/mL, with a LOD of 0.1 pg/mL [53]. Sánchez-Tirado E. et al. developed an immunosensor for the determination of transforming growth factor β1 (TGF-β1) cytokine based on CNT bioconjugates, as shown in Figure 3III. ...
Article
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Nanobioconjugates are hybrid materials that result from the coalescence of biomolecules and nanomaterials. They have emerged as a strategy to amplify the signal response in the biosensor field with the potential to enhance the sensitivity and detection limits of analytical assays. This critical review collects a myriad of strategies for the development of nanobioconjugates based on the conjugation of proteins, antibodies, carbohydrates, and DNA/RNA with noble metals, quantum dots, carbon- and magnetic-based nanomaterials, polymers, and complexes. It first discusses nanobioconjugates assembly and characterization to focus on the strategies to amplify a biorecognition event in biosensing, including molecular-, enzymatic-, and electroactive complex-based approaches. It provides some examples, current challenges, and future perspectives of nanobioconjugates for the amplification of signals in electrochemical biosensing.
... Considering that early detection of cholera is a major challenge and constitutes one of the reasons for mortality [4,5], there has always been the need to develop techniques that will allow for low-cost and quick detection. Today, some of the techniques for the detection of cholera include the conventional culture method [6], enzyme-linked immunosorbent assays (ELISA) [7], polymerase chain reaction (PCR) [8], conductive fiber-optic immunosensor [9], and electrochemical techniques [10][11][12][13][14]. Some of the literature methods are still characterized with several disadvantages. ...
Article
Full-text available
This work describes the use of electrospun onion-like carbon-polyacrylonitrile fibre (OLC-PAN) hybrids as an efficient electrode platform for electrochemical immunosensor for Vibrio cholerae Toxin in water samples. First, the OLC-PAN nanohybrid was obtained by electrospinning technique. The immunosensor was constructed by covalent integration of the Vibrio cholerae antibody (Ab) on OLC-PAN hybrid-based glassy carbon electrode. The electrochemical detection of the antigen (Ag) of the Vibrio cholerae present in water samples was studied using the square wave voltammetry (SWV). The OLC-PAN-based electrode, unlike those of the individual components (OLC and PAN), showed excellent electrochemical sensing properties: as ultralow detection limit (LoD ≈ 2.5 × 10⁻¹⁷ g mL⁻¹) and quantification limit (LoQ ≈ 3 × 10⁻¹⁵ g mL⁻¹) and wide linear concentration range (10⁻¹³ – 10⁻⁵ g mL⁻¹). The OLC-PAN-based electrochemical immunosensor was used to test for real water samples suspected to be infected with cholera, and successfully validated with both the gold-standard culture method and the polymerase chain reaction (PCR) technique. The PCR method showed poor sensitivity (LoD ≈ 5.0 × 10⁻⁷ g mL⁻¹) compared with the SWV, proving the extremely high sensitivity and low-cost advantages of the electrochemical techniques over the conventional PCR. This work reveals the unique synergy between OLC and PAN that can be harnessed for potential development of high-performance electrochemical immunosensors for cholera disease in resource-limited communities.
... With film transfer acting as the bridge between production and application, it currently presents a major challenge for successful commercialization of CNTs [22]. Solution processing of CNT-based films, therefore, offers great potential for the cost-effective preparation of devices such as flexible electrodes, supercapacitors, biosensors, and biofuel cells [23][24][25][26]. For the construction of bioelectrodes, the simple drop-casting of CNTs from aqueous and nonaqueous suspensions represents the most commonly employed method [7,27]. ...
Chapter
This book chapter describes the recent advances in the design of novel materials for enzymatic fuel cells. Energy conversion using biologic catalysts became a steady growing research field for supplying nomad or implantable devices due to the high specifity for the substrates and the high efficiency of redox enzymes. The constant issue, however, is the electric connection of the enzymatic redox centre to the electrode to obtain a high efficient biofuel cell. Among many advantages, nanotechnology have been offering exciting tools to achieve efficient interfacing between redox enzymes and electrical circuitry, while providing high active surfaces. We briefly introduce the principles that govern the production of electrical energy from biofuels using a biofuel cell. We focus our discussion on nanomaterials that have realized the efficient immobilization and wiring of enzymes, in particular carbon nanotubes, inorganic and polymer nanoparticles. We highlight the successfull use of these advanced materials in the engineering of enzyme electrodes and the design of novel miniaturized biofuel cell setups.
... In the past decades, immunosensor or immunoassay, particularly electrochemical immunosensor, has drawn great interest for highly sensitive and selective sensing of biomarkers owing to its simplicity, low cost, and high sensitivity [3][4][5][6][7][8][9][10]. The operation principle of electrochemical immunosensor for detecting tumor markers is based on the transduction of electrochemical signals by changes in charge transfer resistance originating from the specific antigen-antibody recognition, leading to a direct readout. Among various electrochemical immunosensors, impedimetric immunosensor has drawn great attention in biosensor improvement areas owing to its fast analysis and easy detection [11][12][13][14][15][16]. ...
Article
Full-text available
A novel impedimetric immunosensor was fabricated for the determination of carcino-embryonic antigen (CEA) using conductive and adhesive gold/polypyrrole-polydopamine nanocomposite as an immobilization matrix. A polypyrrole-polydopamine complex (PPy-PDA) was first prepared by the polymerization of pyrrole and dopamine, which was then blended with chloroauric acid solution (HAuCl4). The in situ reduction of AuCl4⁻ ions to gold nanoparticles (Au NPs) by polydopamine leads to the successful preparation of gold/polypyrrole-polydopamine nanocomposites (Au/PPy-PDA). The obtained Au/PPy-PDA nanocomposite not only provides a highly biocompatible and stable matrix for loading antibody, but also accelerate the electron transfer process owing to the conductive PPy as well as encapsulated Au NPs, which is quite suitable to be applied as high-efficiency immunoassay platform. CEA antibody (CEA-Ab) was efficiently loaded on Au/PPy-PDA film, and a label-free impedimetric immunosensor was successfully constructed. Under optimal conditions, a wide linear range (0.001–500 ng mL⁻¹) and low detection limit (0.2 pg mL⁻¹) was demonstrated for the detection of CEA. Furthermore, the proposed CEA immunosensor exhibited high specificity, excellent reproducibility, and stability, providing an experimental evidence for early diagnosis of cancer. Accurate detection of CEA in human serum samples was also exhibited.
... Editor's Choice F 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 of electrochemical devices such as biofuel cells, supercapacitors, or biosensors. [1][2][3][4] Thanks to an increased surface area, nanomaterials such as carbon nanotubes, graphene, [5][6][7][8][9][10][11][12][13] semi-conductor quantum dots, [14,15] have significantly increased the power density of biofuel cells and capacitors as well as the analytical performance of biosensors in terms of sensitivity and detection limit. In addition, metallic nanoparticles [16][17][18] have aroused great interest in the elaboration of electrode materials due to their physical and chemical properties such as high surface/volume ratio and relatively high electrical conductivity. ...
Article
Glyconanoparticles (GNPs) made by self-assembly of carbohydrate-based polystyrene-block-β-cyclodextrin copolymer are used as a building block for the design of nanostructured biomaterials of electrode. The firm immobilization of GNPs is carried out on electrochemically generated polymer, poly(pyrrole-adamantane), and copolymer, poly(pyrrole-adamantane)/poly(pyrrole-lactobionamide) via host–guest interactions between adamantane and β-cyclodextrin. The ability of GNPs for the specific anchoring of biological macromolecules is investigated using glucose oxidase enzyme modified by adamantane groups as a protein model (GOx-Ad). The immobilization of GOx-Ad is carried out by incubation of an aqueous enzyme solution on a coating of GNPs adsorbed on a platinum electrode. The presence of immobilized GOx-Ad is evaluated in aqueous glucose solution by potentiostating the underlying platinum electrode at 0.7 V/SCE for the electro-oxidation of H2O2 generated by the enzyme. The analytical performance of the bioelectrodes for the detection of glucose is compared to control electrodes prepared without GNPs or without electropolymerized films. The better permeability of copolymer compared to polymer and the possibility to elaborate two alternating layers of GNPs and GOx-Ad are clearly observed. The best amperometric response is recorded with a multilayered bioelectrode displaying a wide linear range linear range of the calibration curve: 68 µmol L⁻¹ to 0.1 mol L⁻¹.
... Both traditional techniques and emerging biosensor technologies for cholera were reviewed in 2016 [127]. The majority of approaches detect either DNA [128][129][130][131][132], toxin [127,[133][134][135], or antibody [136] (these latter two not applying to waterborne testing), with only a few studies detecting the bacteria themselves. ...
Chapter
Biosensors are devices that comprise a target recognition element, which is biological, coupled with a mechanism of signal transduction. The function of a biosensor is to convert a biological recognition event into a detectable signal by the action of the transducer and signal conditioning circuitry, thereby providing selective quantitative or semiquantitative analytical information. Common recognition elements include enzymes, antibodies, DNA, or even whole cells. These elements bind either cells and cell fragments or nucleic acids, or amplification products from molecular methods present in the solution. This chapter will focus on biosensors, which capture whole pathogens, rather than, for example the amplification products of molecular methods, which will be covered in Chapter 8.
... The target cholera toxin was coordinated with Cu 2+ to be linked to the anti-cholera Ab and detected by EIS with Fe(CN) 6 3− as a redox probe. The biosensor reached a linear-dependent concentration-response, with a LOD of 0.1 pg mL −1 (Palomar et al., 2017). ...
Chapter
Biosensing platforms with signal amplification have proven to be an innovative tool of potential use in several applications in the environment, industrial, security and biomedical fields. Signal amplification allows the detection of specific biomarkers and target analytes with high sensitivity at low detection limits. This book chapter collects a variety of strategies for the development of biosensors with amplified signals, focused mainly in the biomedical field, including biosensors based on bioaffinity and biocatalytic reactions in the light of electrochemical, optic, piezometric and magnetoelastic biosensors. It critically discusses the advantages and disadvantages and challenges and opportunities associated with the reviewed formats.
Article
Considerable biocompatibility, prospect of engineering the surface as per the deliberated application, and high accuracy of the results have driven the development of carbon nano tubes (CNTs) based biosensors. Enzyme catalyzed reactions occur under immensely milder physiological environments with high substrate specificity that minimizes the formation of side-products. Enzyme Immobilization represents the space-localization, or physical confinement of the enzymes that restrains their catalytic activity and improves their recyclability. The present article aims to provide a comprehensive record of the enzyme immobilization on the engineered CNTs, and their subsequent applications for the detection of various analytes. In addition, the recent advances in the functionalization techniques for enzyme-less detection of analytes on modified CNTs, their commercialization aspects and associated challenges is discussed.
Thesis
Le but principal de ces travaux de thèse fut la conception et la réalisation de biocapteurs par utilisation de méthodes de transduction sans marquage, comme la spectroscopie d’impédance électrochimique (EIS), pour la détection de cible d’intérêts. Pour cela, différentes architectures moléculaires, spécifiques à la molécule d’intérêt ciblée, ont été développées afin de permettre la transduction du signal issu de la reconnaissance entre le biorécepteur et son substrat, et conduire ainsi à la détection de la cible.Les systèmes mis au point reposent sur l’intégration de nanomatériaux, tels que les nanotubes de carbones ou le disulfure de tungstène, pour assurer l'immobilisation de l'entité biospécifique à la surface du capteur. L’intérêt de ces matériaux est multiple puisqu’ils permettent une très forte augmentation de la surface spécifique du système et sont également mis à contribution lors de la fonctionnalisation de la surface de l’électrode. Un des grands défis rencontré dans le développement des biocapteurs étant la stratégie d'immobilisation de l'entité biospécifique sur la surface du capteur.Ces travaux se sont donc dans un premier temps intéressés à la réalisation et à la caractérisation de films minces de ces nanomatériaux ainsi qu’à leur transfert à la surface d’une électrode. Dans ce contexte, le but est de concevoir des bioarchitectures poreuses à base de polymères fonctionnels électrogénérés autour des nanostructures de carbone permettant la pénétration de grandes biomolécules comme des anticorps pour développer des immunocapteurs de haute performance.La seconde partie de ce travail s’est donc orientée vers la conception de biocapteurs par utilisation de ces différents matériaux. La fiabilité du procédé de la construction de ces nanostructures poreuses a été validée par la conception de systèmes immunologiques pour la détection de l’anticorps de l’antitoxine du choléra et l’anticorps de la toxine de la dengue.Enfin, un dernier biocapteur enzymatique, s’appuyant sur l’utilisation de nano-bâtonnets de disulfure de tungstène, a été développé. Ce dernier permet la détection de deux molécules d’intérêts, à savoir le catéchol et la dopamine, par utilisation de la polyphénol oxydase.
Article
Viral pathogens are a serious health threat around the world, particularly in resource limited settings, where current sensing approaches are often insufficient and slow, compounding the spread and burden of these pathogens. Here, we describe a la-bel-free, point-of-care approach towards detection of virus particles, based on a microfluidic paper-based analytical device with integrated microwire Au electrodes. The device is initially characterized through capturing of streptavidin modified na-noparticles by biotin-modified microwires. An order of magnitude improvement in detection limits is achieved through use of a microfluidic device over a classical static paper-based device, due to enhanced mass transport and capturing of particles on the modified electrodes. Electrochemical impedance spectroscopy detection of West Nile virus particles was carried out using an antibody functionalized Au microwires, achieving a detection limit of 10.2 particles in 50 μL of cell culture media. No increase in signal is found on addition of an excess of a non-specific target (Sindbis). This detection motif is significantly cheaper (~$1 per test) and faster (~30 min) than current methods, while achieving the desired selectivity and sensitivity. This sensing motif represents a general platform for trace detection of a wide range of biological pathogens.
Thesis
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This thesis explores two ways to enhance the performance of an electrochemical affinity biosensor for the detection of dengue anti-NS1 antibodies. The first goal was to improve the limit of detection and sensitivity of biosensors using microstructuration of the transducer. Based on finite element modelling, an optimal range of the microcone geometric parameters was defined. After construction, the microcone-covered electrodes were characterised using cyclic voltammetry and scanning electron microscopy. At the end of the optimisation process, glucose biosensors were fabricated to demonstrate the increased performance gains of an amperometric biosensing platform. Finally, in order to validate the interest of the microcones for an affinity biosensor, a label-free impedimetric immunosensor allowing the quantification of the cholera toxin B-subunit was studied as a model before performing an immunosensor of interest for dengue antibodies. The immunosensors were made on two types of electrodes: microcone-coated electrodes and interdigitated electrodes. A second goal was to improve the shelf-life of lateral-flow biosensors by microencapsulating labelled biomolecules, mandatory for competitive detection. For this purpose, low-cost polymer microcapsules have been developed. Methylene blue and an enzyme, glucose oxidase, were encapsulated in a dry state. Their release was followed by UV-visible spectroscopy and/or electrochemistry after breaking the microcapsules by mechanical action and/or with ultrasonic agitation.
Article
Herein, a label-free electrochemical immunosensor based on differential pulse voltammetry (DPV) and amperometric i-t curve (i-t) dual-mode analysis is proposed for early quantitative detection of procalcitonin (PCT). Due to the advantages of high chemical stability and biocompatibility, graphite carbon nitride (g-C3N4) was adopted as a high-capacity sensing interface to carry signal indicators. As an effective indicator of chronoamperometry, nickel cobalt sulfide (NiCo2S4) was uniformly dispersed on the surface of g-C3N4 through in-situ hydrothermal synthesis, which not only promotes the activation of bimetallic activity, but also effectively prevents the aggregation of NiCo2S4. At the same time, in order to establish a dual-mode analysis platform to improve accuracy and sensitivity, highly conductive carbon nanotubes (CNTs) were hybridized with composite materials to load Ag nanoparticles (Ag NPs), which have excellent oxidizing properties and are used as indicators of DPV. On account of this advanced sensing strategy, a wide linear response (DPV: 0.05 ng mL-1-50 ng mL-1 and i-t: 1.00 pg mL-1-10.00 ng mL-1) and a low detection limit (DPV: 16.70 pg mL-1 and i-t: 0.33 pg mL-1) are demonstrated. The immunosensor synthesized by this method has good stability and sensitivity, which could be applied in clinical diagnosis and treatment.
Thesis
Cette thèse explore deux voies d’amélioration des performances d'un biocapteur électrochimique d'affinité pour la détection des anticorps anti-NS1 de la dengue.La première volonté est l'amélioration de la limite de détection et de la sensibilité des biocapteurs par microstructuration du transducteur. Une modélisation basée sur les éléments finis a permis de définir la gamme optimale des paramètres géométriques des microplots. Après construction, les électrodes recouvertes de microplots ont été caractérisées par voltampérométrie cyclique et par microscopie électronique à balayage. A l'issue de l'optimisation, des biocapteurs à glucose ont été construits afin de démontrer l'accroissement des performances d’un biocapteur ampérométrique. Enfin, dans le but de valider l'intérêt des microplots pour un biocapteur d'affinité, un modèle d'immunocapteur impédance métrique sans marquage permettant la quantification de l'anticorps de la sous-unité B de la toxine du choléra est étudié avant de procéder à la réalisation d'un immunocapteur d'intérêt pour l'anticorps de la dengue. Ils sont réalisés sur deux types d'électrodes : les électrodes recouvertes de microplots et des électrodes interdigitées.La seconde volonté est l'amélioration de la longévité du stockage des biocapteurs à flux latéral par microencapsulation des biomolécules marquées, nécessaires à la détection par compétition. Pour cela, des microcapsules de polymère, fabriquées à faible coût, sont développées. Le bleu de méthylène et l'enzyme glucose oxydase ont été encapsulées sous forme sèche. Leur relargage a été suivi par spectrophotométrie UV-Visible et/ou par électrochimie après cassure des microcapsules par action mécanique et/ou par ultrasons.
Article
WS2 nanotubes functionalized with carboxylic acid functions (WS2-COOH) were used for improved immobilization of the enzyme tyrosinase in order to form an electrochemical biosensor towards catechol and dopamine. The nanotubes were deposited on glassy carbon electrodes using a dispersion-filtration-transfer procedure to assure the reproducibility of the deposits. After the electrochemical and morphological characterization of these WS2-COOH nanotubes deposits, the formed biosensors showed very satisfying performances towards catechol detection with a linear range between 0.6 – 70 µmol L-1 and a sensitivity of 10.7 ± 0.2 mA L mol-1. The apparent Michaelis Menthen constant of this system is slightly lower than the KM value of tyrosinase in solution reflecting an excellent accessibility of the active site of the enzyme combined with a good mass transport of the target molecule through the deposit. For dopamine detection, we observed an accumulation of this substrate due to electrostatic interactions between the dopamine’s amine function and the carboxylic acid groups of the nanotubes. This led to improved signal capture at low dopamine concentrations. With a linear range between 0.5 – 10 µmol L-1 and 10 – 40 µmol L-1, and respective sensitivities of 6.2 ± 0.7 mA L mol-1 and 3.4 ± 0.4 mA L mol-1, the overall sensor performances are in the average of comparable results using carbon nanotubes. Nonetheless, the simplified handling of these nanotubes and their reduced environmental impact make these WS2-COOH nanotubes a promising nanomaterial for biosensing applications.
Article
In this study, a high-performance anti-fouling coating based on poly adenine (polyAn) as well as a highly specific cluster of differentiation 20 (CD20) epitope mimetic peptide (CN14) were employed to synergistically construct a facile biosensor for the rapid and sensitive determination of rituximab in lymphoma patients' plasma. The well-designed and optimized polyAn coating displayed excellent stability, hydrophilicity, thanks to its intrinsic affinity with gold surface and thoroughly exposed hydrophilic phosphate groups. Moreover, the proposed strategy avoids the necessity to modify binding groups (e.g. thiol), making it more facile, repeatable and efficient. When dealing with complex clinical plasma samples, the polyAn coating demonstrated better anti-fouling performance and lower background signal in comparison with mercaptan and bovine serum albumin coatings. The dissociation constant (~60 nM) between CN14 and rituximab was measured by microscale thermophoresis and their binding mechanism was further explained using computer simulation. The constructed GE/CN14/polyA20 biosensor displayed satisfactory performance with detection limit of 35.26 ng/mL. Finally, the proposed biosensor was successfully applied for rapidly determining rituximab in lymphoma patients' plasma, and exhibited comparable accuracy to the commercial ELISA, but has advantages including a shorter detection time, wider detection range and lower cost. It's worth noting that the anti-fouling polyAn coating can be tailored according to the surface property of sensing interface and can be easily expanded to other gold electrode related biosensors.
Article
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An electrochemical immunosensor for Vibrio cholerae toxin (VCT) has been developed using electrospun carbon nanofibers (CNFs) as the electrode platform. To fabricate the immunosensor, the anti-cholera toxin antibody (Ab) was covalently immobilized on the electrode platforms using the carbodiimide chemistry for the amide bond formation. Every step of the formation of the immunosensor and the subsequent binding of the VCT subunit antigen (Ag) was electrochemically interrogated. The immunosensor gave excellent reproducibility and sensitivities: limits of detection (ca. 1.2 × 10–13 g mL–1), limits of quantification (ca. 1.3 × 10–13 g mL–1), and a wide linear range for the anti-cholera detection of 8 orders of magnitude (10–13 to 10–5 g mL–1). One of the key findings was the enhanced sensitivity of the VCT detection using aged rather than the freshly prepared redox probe, described here as Redox Probe Aging-Induced Sensitivity Enhancement (“Redox-PrAISE”). The Redox-PrAISE was found more useful in the real application of these immunosensors, showing comparable or even better sensitivity for eight real cholera-infested water samples than the conventional clinical culture method. This immunosensor shows promise for the potential development of point-of-care diagnosis of VCT. Importantly, this study highlights the importance of considering the nature of the redox probe on the electrochemical sensing conditions when designing impedimetric immunosensors.
Article
This work presents an effective strategy for the well-oriented immobilization of antibodies in which boronic acid is directly attached to the surface and with no need of the long and flexible spacer. A magnetic graphene nanoribbon-boronic acid-based immunosensor was developed and tested for the impedimetric detection of lymphoma cancer cells, a blood cancer biomarker. Magnetic graphene nanoribbons (MGNRs) were modified with boronic acid (BA) to create a supporting matrix that is utilized by immobilizing anti-CD20 antibodies with good orientation. The prepared biosensing layer (MGNR/BA/Ab) with well-oriented antibodies was premixed into whole blood samples to interact with lymphoma cancer cell receptors. In the presence of target cell receptors, an immunocomplex was formed between anti-CD20 antibodies and lymphoma cancer cell receptors. Then, the biosensing layer was magnetically collected on a screen-printed carbon electrode (SPCE) and placed in a homemade electrochemical cell configuration to measure impedimetric signals. The fabrication steps of the immunosensor were characterized by various techniques, such as resonance light scattering, fluorescence, electrochemical impedance spectroscopy, and cyclic voltammetry. The assay is highly sensitive: the calculated limit of detection of lymphoma cancer cells was as low as 38 cells/mL, and the detection was linear from 100 to 1000000 cells/mL. The specificity of the immunosensor is also very high, and there is no interference effect with several potential interferents, such as the breast cancer (MCF-7), human embryonic kidney (HEK293) and leukemia (HL-60 and KCL-22) cell lines. The performance of the immunosensor for lymphoma cancer cells in clinical blood samples is consistent with that of commercial flow cytometric assays.
Article
Glycan-recognizing toxins play a significant role in the etiology of many diseases afflicting humanity. The carbohydrate recognition domains of these toxins play essential roles in the virulence of many microbial organisms with multiple modes of action, from promoting pore formation to facilitating the entry of toxic enzymatic subunits into the host cell. Carbohydrate-binding domains with an affinity for specific glycan-based receptors can also be exploited for various applications, including detecting glycobiomarkers, as drug delivery systems, and new generation biopharmaceutical products and devices (e.g. glycoselective capture of tumor-derived exosomes). Therefore, understanding how to efficiently express and purify recombinant toxins and their carbohydrate-binding domains can enable opportunities for the formulation of innovative biopharmaceuticals that can improve human health. Here, we provide an overview of carbohydrate-binding toxins in the context of biotechnological innovation. We review 1) structural characteristics concerning the toxins' mode of action; 2) applications and therapeutic design with a particular emphasis on exploiting carbohydrate-binding toxins for production of anti-tumor biopharmaceuticals; discuss 3) possible ways to manufacture those molecules at a bioreactor scale using microbial expression systems, and 4) their purification using their affinity for glycans.
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Abstract In this work an impedimetric immunosensor based on affinity immobilization method of a biotin labelled anti-human IgG antibody, used as a model system, was reported. The experimental procedure involves the growth of a self-assembled monolayer of a thiol (cysteamine) carrying terminal amine groups on gold electrodes. Glutarardehyde, a homobifunctional cross-linker, was used as a coupling reagent for the covalent linking of avidin to the amine groups of cysteamine. The attachment of the biotin labeled antibodies (anti-Human IgG) to the subsequent modified gold electrode was achieved by affinity interactions tacking advantage of the strong avidin-biotin bridge. The stepwise assembly process of the electrode was interrogated by means of cyclic voltammetry, electrochemical impedance spectroscopy and contact angle measurements. The response of the antibody modified electrode to their target antigens was investigated in the presence of BSA (bovin serum albumin) in order to alleviate non-specific adsorption problems. A proposed electrical model was used to analyse the experimental data. The resulting immunosensor has a linear dynamic range of 100 - 900 ng·ml−1 of antigen and a detection limit of 100 ng·ml−1.
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Six types of commercially available multiwall carbon nanotube soot were obtained and prepared into buckypapers by pellet pressing and by filtration into a paper. These samples were evaluated with respect to thickness, compressibility and electrical conductivity. DC conductivity results by two-point and four-point (van der Pauw) measurement methods as a function of preparation parameters are presented. Topology was investigated qualitatively by way of scanning electron microscopy and helium ion microscopy and from this, some generalizations about the nanotube structural properties and manufacturing technique with respect to conductivity are given.
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A biosensor device is defined by its biological, or bioinspired receptor unit with unique specificities toward corresponding analytes. These analytes are often of biological origin like DNAs of bacteria or viruses, or proteins which are generated from the immune system (antibodies, antigens) of infected or contaminated living organisms. Such analytes can also be simple molecules like glucose or pollutants when a biological receptor unit with particular specificity is available. One of many other challenges in biosensor development is the efficient signal capture of the biological recognition event (transduction). Such transducers translate the interaction of the analyte with the biological element into electrochemical, electrochemiluminescent, magnetic, gravimetric, or optical signals. In order to increase sensitivities and to lower detection limits down to even individual molecules, nanomaterials are promising candidates due to the possibility to immobilize an enhanced quantity of bioreceptor units at reduced volumes and even to act itself as transduction element. Among such nanomaterials, gold nanoparticles, semi-conductor quantum dots, polymer nanoparticles, carbon nanotubes, nanodiamonds, and graphene are intensively studied. Due to the vast evolution of this research field, this review summarizes in a non-exhaustive way the advantages of nanomaterials by focusing on nano-objects which provide further beneficial properties than "just" an enhanced surface area.
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A sensitive and stable label-free electrochemical impedance immunosensor for the detection of Salmonella typhimurium was developed by immobilising anti-Salmonella antibodies onto the gold nanoparticles and poly(amidoamine)-multiwalled carbon nanotubes-chitosan nanocomposite film modified glassy carbon electrode (AuNPs/PAMAM-MWCNT-Chi/GCE). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to verify the stepwise assembly of the immunosensor. Co-addition of MWCNT, PAMAM and AuNPs greatly enhanced the sensitivity of the immunosensor. The immobilisation of antibodies and the binding of Salmonella cells to the modified electrode increased the electron-transfer resistance (Ret), which was directly measured with EIS using [Fe(CN)6](3-/4-) as a redox probe. A linear relationship of Ret and Salmonella concentration was obtained in the Salmonella concentration range of 1.0×10(3) to 1.0×10(7)CFUmL(-1) with a detection limit of 5.0×10(2)CFUmL(-1). Additionally, the proposed method was successfully applied to determine S. typhimurium content in milk samples with satisfactory results.
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A novel vertically aligned carbon nanotube based electrical cell impedance sensing biosensor (CNT-ECIS) was demonstrated for the first time as a more rapid, sensitive and specific device for the detection of cancer cells. This biosensor is based on the fast entrapment of cancer cells on vertically aligned carbon nanotube arrays and leads to mechanical and electrical interactions between CNT tips and entrapped cell membranes, changing the impedance of the biosensor. CNT-ECIS was fabricated through a photolithography process on Ni/SiO(2)/Si layers. Carbon nanotube arrays have been grown on 9 nm thick patterned Ni microelectrodes by DC-PECVD. SW48 colon cancer cells were passed over the surface of CNT covered electrodes to be specifically entrapped on elastic nanotube beams. CNT arrays act as both adhesive and conductive agents and impedance changes occurred as fast as 30 s (for whole entrapment and signaling processes). CNT-ECIS detected the cancer cells with the concentration as low as 4000 cells cm(-2) on its surface and a sensitivity of 1.7 × 10(-3)Ω cm(2). Time and cell efficiency factor (TEF and CEF) parameters were defined which describe the sensor's rapidness and resolution, respectively. TEF and CEF of CNT-ECIS were much higher than other cell based electrical biosensors which are compared in this paper.
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Electrochemical biosensors combine the sensitivity of electroanalytical methods with the inherent bioselectivity of the biological component. The biological component in the sensor recognizes its analyte resulting in a catalytic or binding event that ultimately produces an electrical signal monitored by a transducer that is proportional to analyte concentration. Some of these sensor devices have reached the commercial stage and are routinely used in clinical, environmental, industrial, and agricultural applications. The two classes of electrochemical biosensors, biocatalytic devices and affinity sensors, will be discussed in this critical review to provide an accessible introduction to electrochemical biosensors for any scientist (110 references).
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Cholera toxin was obtained in pure form by fractionation on two phosphocellulose columns successively. Cholera toxin and choleragenoid were quantitatively and selectively adsorbed to the first column in 10 mM phosphate buffer, pH 7.0, and were subsequently eluted with buffer of high ionic strength. The toxin was then separated from choleragenoid on the second column by chromatography at pH 8.3. The toxin obtained was highly active and pure as judged by electrophoresis, isoelectric focusing, and various immunological and chemical tests. Pure choleragenoid was by-product of the procedure. The A1 chain of the toxin was obtained in pure form by treating phosphocellulose-bound toxin with urea and a reducing agent. The anionic A1 peptide was thereby released, leaving a complex of the B and A2 chains (A25B) bound to the resin. The latter was then eluted and further purified to obtain nontoxic antigen. The overall yields of cholera toxin and choleragenoid were increased two- to threefold by the use of hypertoxinogenic mutants of Vibrio cholerae.
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We describe a simple process for the fabrication of ultrathin, transparent, optically homogeneous, electrically conducting films of pure single-walled carbon nanotubes and the transfer of those films to various substrates. For equivalent sheet resistance, the films exhibit optical transmittance comparable to that of commercial indium tin oxide in the visible spectrum, but far superior transmittance in the technologically relevant 2- to 5-micrometer infrared spectral band. These characteristics indicate broad applicability of the films for electrical coupling in photonic devices. In an example application, the films are used to construct an electric field–activated optical modulator, which constitutes an optical analog to the nanotube-based field effect transistor.
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We demonstrate herein a newly developed photoelectrochemical immunosensor for the determination of anti-cholera toxin antibody by using a photosensitive biotinylated polypyrrole film. The latter was generated by electro-oxidation of a biotinylated tris(bipyridyl) ruthenium(II) complex bearing pyrrole groups. The photoexcitation of this modified electrode potentiostated at 0.5 V vs SCE, in the presence of an oxidative quencher, pentaaminechloro cobalt(III) chloride (15 mM), led to a cathodic photocurrent. As a result of the affinity interactions, a layer of biotinylated cholera toxin was firmly bound to the functionalized polypyrrole film via avidin bridges. The resulting modified electrodes were tested as immunosensors for the detection of the corresponding antibody from 0 to 200 microg mL(-)(1). The antibody concentration was measured through the decrease in photocurrent intensity resulting from its specific binding onto the polymeric coating, the detection limit being 0.5 microg mL(-)(1).
Article
At present cholera remains a major public health problem. It is an acute worldwide diarrheal disease caused by the bacterium Vibrio cholerae. It affects in particular developing countries where people get infected by ingesting contaminated water and food. In this review, both internationally recognized conventional methods and new technologies in development for V. cholerae detection are reviewed. Currently, culture methods are the "gold standard" in cholera detection. Molecular techniques have a better sensitivity, but they require specific and expensive equipment. There is a need for fast, reliable, easy to use, sensitive, specific systems to use in the field during outbreaks as well as in the laboratory. Several prototype devices have been developed, but their sensitivity and specificity are low. To overcome these problems biosensors could become an attractive and efficient alternative, but they still have to be subjected to some modifications and improvements for their use in the field.
Article
Carbon nanotubes (CNTs) have been widely recognized and used for controlled drug delivery and in various other fields due to their unique properties and distinct advantages. Both single-walled carbon nanotubes (SWCNTs) and multiwalled (MWCNTs) carbon nanotubes are used and/or studied for potential applications in medical, energy, textile, composite, and other areas. Since CNTs are chemically inert and are insoluble in water or other organic solvents, they are functionalized or modified to carry payloads or interact with biological molecules. CNTs have been preferably functionalized with proteins because CNTs are predominantly used for medical applications such as delivery of drugs, DNA and genes, and also for biosensing. Extensive studies have been conducted to understand the interactions, cytotoxicity, and potential applications of protein functionalized CNTs but contradicting results have been published on the cytotoxicity of the functionalized CNTs. This paper provides a brief review of CNTs functionalized with proteins, methods used to functionalize the CNTs, and their potential applications.
Article
Iron particle impurities of HiPCO® single-walled carbon nanotubes (SWCNTs) are treated as undesirable moieties and considerable times and efforts is allocated towards research and development to reduce their amount in HiPCO® SWCNTs. Taking advantage of this impurity, 3D nanostructured scaffolds are built via layer by layer (LBL) deposition of HiPCO® SWCNTs and magnetic nanoparticles which are retained via magnetic interaction with the iron particle impurities during the scaffold formation. The resulting scaffold has an inhomogeneous structure with large vacancies that can further be reinforced by electrogeneration of a functional polymer film to enable the immobilization of bioreceptor units for biosensing. Magnetic nanoparticles of different sizes are used to adjust the pore sizes within the scaffolds in order to determine the optimal particle size for their application as highly sensitive immunosensors. Scaffolds made of the magnetic nanoparticles with in average 500 nm sizes led to a sensitivity of 88 μA μg−1 mL cm−2 equivalent to a detection limit of 10 ng mL−1 for cholera antitoxin. This is by far the highest sensitivity for anti-CT immunosensors compared to amperometric transduction or ELISA.
Article
Carbon nanotube (CNT) based biosensors are recognized to be a next generation building block for ultra-sensitive and ultra-fast biosensing systems. This article provides an overview on the recent expansion of research in the field of CNT-based biosensors. We start by first introducing the material structures and properties of CNTs. The basic and some new developed synthetic methods of CNTs are presented. This is followed by a collection of working principle and performance of different CNT-based biosensors. The roles and the processing methods of functionalized CNTs are summarized. After that, some of the practical applications and concerns in the field are addressed. What is more, the scientific and technological challenges in the field are discussed at the end of this review.
Article
Impedance spectroscopy transduction combined with the immunosensor technology has been used for the determination of atrazine, a herbicide The sensor electrode was based on the immobilization of anti-atrazine antibody by affinity binding onto a polypyrrole film N-substituted by nitrilotriacetic acid NTA electrogenerated on a gold electrode. The poly NTA film was previously modified by the coordination of Cu2 ions by the chelating NTA centers. The anti-atrazine antibody Fab fragment K47 modified with histidine-tag was then anchored by affinity interactions between the histidine-tag and the coordinated Cu2. Cyclic voltammetry experiments confirm that the antibody immobilization and the resulting immunosensor were applied to the impedimetric detection of atrazine without reagent and labelling step. The immunoreaction of atrazine on the attached anti-atrazine antibody directly triggers an increase in the charge transfer resistance proportional to the atrazine concentration, allowing the detection of extremely low atrazine concentration, namely 10pgmL−1.
Article
The present study details work done at the National Public Health Laboratory in Haiti (LNSP), comparing the results of a cholera rapid diagnostic test (RDT) with culture-based methods. As of October 21, 2011, 644 specimens were tested by both RDT and culture-based method at the LNSP. The sensitivity and specificity of RDT were 95% and 80%, respectively, with a positive predictive value of 89% and negative predictive value of 91%. In resource-limited settings, the RDT has good utility and should be considered as part of the laboratory testing algorithm.
Article
Electrical double-layer capacitance measurements of six solid metal electrodes, platinum gold, copper, iron, nickel and silver, in aqueous solutions of potassium chloride, bromide, iodide, nitrate and sodium sulphate were carried out with an impedance bridge, under high purity conditions. The constant capacitance obtained with these metal/solution interfaces are interpreted on the basis of Devanathan's model of the electrical double laeyr as due to the solvent contribution only, uninfluenced by specific adsorption effects in the potential range investigated.
Article
This review is based on the Theophilus Redwood Medal and Award lectures, delivered to Royal Society of Chemistry meetings in the UK and Ireland in 2012, and presents a personal overview of the field of biosensors. The biosensors industry is now worth billions of United States dollars, the topic attracts the attention of national initiatives across the world and tens of thousands of papers have been published in the area. This plethora of information is condensed into a concise account of the key achievements to date. The reasons for success are examined, some of the more exciting emerging technologies are highlighted and the author speculates on the importance of biosensors as a ubiquitous technology of the future for health and the maintenance of wellbeing.
Article
This review addresses recent advances in carbon-nanotubes (CNT) based electrochemical biosensors. The unique chemical and physical properties of CNT have paved the way to new and improved sensing devices, in general, and electrochemical biosensors, in particular. CNT-based electrochemical transducers offer substantial improvements in the performance of amperometric enzyme electrodes, immunosensors and nucleic-acid sensing devices. The greatly enhanced electrochemical reactivity of hydrogen peroxide and NADH at CNT-modified electrodes makes these nanomaterials extremely attractive for numerous oxidase-and dehydrogenase-based amperometric biosensors. Aligned CNT "forests" can act as molecular wires to allow efficient electron transfer between the underlying electrode and the redox centers of enzymes. Bioaffinity devices utilizing enzyme tags can greatly benefit from the enhanced response of the biocatalytic-reaction product at the CNT transducer and from CNT amplification platforms carrying multiple tags. Common designs of CNT-based biosensors are discussed, along with practical examples of such devices. The successful realization of CNT-based biosensors requires proper control of their chemical and physical properties, as well as their functionalization and surface immobilization.
Article
Impedance spectroscopy is a rapidly developing electrochemical technique for the characterization of biomaterial-functionalized 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 enzyme-based 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.
Article
The adsorption of β-CN (193–209) peptide onto a carbon electrode was investigated for various charges of the surface by recording over time the variations of the double layer capacitance Cd during peptide adsorption. In earlier work [M. Mullet et al., J. Membrane Sci. 128 (1997) 243] we showed that this experimental variation satisfies a two exponential law, which is consistent with a two-step irreversible adsorption process. The first step was attributed to the adsorption reaction itself and the second to a change in the conformation of the adsorbed molecules.The rate of the first step of the adsorption and the area of the electrode surface in close contact with β-CN (193–209) peptide display a maximum in the vicinity of the potential of zero charge. Such results indicate that hydrophobic interactions are dominant in β-CN (193–209) peptide adsorption onto carbon. We also suggest that interfacial water properties are involved in β-CN (193–209) peptide adsorption. In fact, the existence of a charge at the carbon interface may destructure water molecules induced in hydrophobic hydration and consequently decrease hydrophobic interactions.
Article
Here we examine how heterogeneous protein adsorption arises from multivalent interactions with a seemingly homogeneous functional surface. During adsorption, some arrangement of functional groups on the protein (e.g., charged or hydrophobic amino-acid residues or specific ligand binding sites) interacts with complementary sites distributed on the adsorbent surface. The protein will show the highest affinity for the surface arrangements which best match its own distribution of functional sites, resulting in a distribution of binding energies. To support this interpretation, we show that changing the density of affinity ligands on a surface (immobilized metal ions) is equivalent to changing the number of target groups on a protein (surface histidines). We also report that reversible protein adsorption obeys the Temkin isotherm and propose that model as a practical framework for describing the behavior of proteins adsorbing via multivalent interactions onto surfaces densely derivatized with a random distribution of binding functionalities. This result has important implications for the design of separations materials and the interpretation of biological recognition phenomena.
Article
The construction of amperometric immunosensors to cholera antitoxin immunoglobulins were shown to have improved sensitivity when the cholera toxin B subunit biorecognition entity was linked to an electrogenerated biotinylated polypyrrole film copolymerized with pyrrole-lactobionamide monomer. The copolymer exhibits greater film permeability than biotinylated polypyrrolic or polyphenolic films for the permeation of electroactive species. Hence, when the presence of the HRP marker of the immunoassay was determined using hydroquinone, the production of electroactive quinone was shown to permeate faster to the electrode, thus providing a faster response time.
Article
This short review is focused on recent advances in the combination of conducting polymers and SWCNTs for the fabrication of electrochemical biosensors. The different properties of conducting polymers and SWCNTs are discussed in respect of their use in immobilizing and wiring biomolecules on electrode surfaces. We further describe the functionalization techniques used in the fabrication of these devices and their associated biosensing performances.
Article
Highly sensitive, label-free biodetection methods have applications in both the fundamental research and healthcare diagnostics arenas. Therefore, the development of new transduction methods and the improvement of the existing methods will significantly impact these areas. A brief overview of the different types of biosensors and the critical parameters governing their performance will be given. Additionally, a more in-depth discussion of optical devices, surface functionalization methods to increase device specificity, and fluidic techniques to improve sample delivery will be reviewed.
Article
Electrical impedance properties of different type of carbon nanotubes based bulk electrodes have been investigated to develop chemical and biosensors. The bulk composite electrodes were fabricated with single-wall and multi-wall carbon nanotubes involving ionic conducting host polymer, Nafion, by using traditional solution-casting techniques. Under the various amounts of buffer solution, resistance and capacitance of the electrodes were measured with LCR meter and their characteristics due to ionic conducting host polymer were investigated by means of electrokinetic analysis. The capacitance values showed drastic change while the resistances only changed within few percent ranges. Electrical impedance measurement provided rapid and simple sensing mechanism to develop chemical sensor and biosensors with bulk nano electrodes.
Article
An ultrahigh performance impedimetric DNA sensor is presented showing detection limits in the femtomolar range. This electrochemical setup was constructed initially by electrogeneration of poly(11-pyrrol-1-yl-undecanoic acid N(alpha'),N(alpha)-bis(carboxymethyl)-L-lysine amide) (poly(pyrrole-NTA)) film. The latter was then modified by the coordination of Cu(2+) ions onto the chelating NTA centers followed by the immobilization of the ssHIV-DNA previously modified by a polyhistidine tag by affinity binding. The immobilization of the DNA probe and hybridization with the complementary target ssHIV-DNA were investigated using fluorescence microscopy and quantified with quartz crystal microbalance experiments leading to DNA probe and duplex coverage of 1.7 x 10(-11) and 7.7 x 10(-12) mol cm(-2), respectively. The duplex formation was corroborated by amperometric measurements through the duplex labeling by a glucose oxidase. In the presence of hydroquinone as redox indicator, the DNA sensor was applied to the impedimetric detection of target DNA without a labeling step. A linear quantification of the HIV DNA target was carried out in the range 10(-15) to 10(-8) mol L(-1).
Article
This paper describes the construction of an impedimetric immunosensor for the label-free detection of ciprofloxacin, an antibiotic belonging to synthetic fluoroquinolones. A poly(pyrrole-N-hydroxysuccinimide) film was electrogenerated onto electrodes and then used for the reagentless covalent binding of a fluoroquinolone model bearing an amino group. The resulting electrodes were utilized to immobilize a layer of anticiprofloxacin antibody onto the polymer surface by immunoreaction. In presence of ciprofloxacin, the antibody was displaced in solution inducing marked changes in the impedance of the sensor electrodes. These phenomena were detected and characterized by electrochemical impedance spectroscopy allowing the selective detection of extremely low ciprofloxacin concentration, namely, 1 x 10(-12) g mL(-1) or 3 pmol L(-1). Sensors exposed to ciprofloxacin showed a decrease in the sum of the interfacial resistances with the increase in ciprofloxacin concentration from 1 x 10(-12) to 1 x 10(-6) g mL(-1).
Article
A polyaniline nanofibers (PAN(nano))/carbon paste electrode (CPE) was prepared via dopping PAN(nano) in the carbon paste. The nanogold (Au(nano)) and carbon nanotubes (CNT) composite nanoparticles were bound on the surface of the PAN(nano)/CPE. The immobilization and hybridization of the DNA probe on the Au(nano)-CNT/PAN(nano) films were investigated with differential pulse voltammetry (DPV) and cyclic voltammetry (CV) using methylene blue (MB) as indicator, and electrochemical impedance spectroscopy (EIS) using [Fe(CN)(6)](3-/4-) as redox probe. The voltammetric peak currents of MB increased dramatically owing to the immobilization of the probe DNA on the Au(nano)-CNT/PAN(nano) films, and then decreased obviously owing to the hybridization of the DNA probe with the complementary single-stranded DNA (cDNA). The electron transfer resistance (R(et)) of the electrode surface increased after the immobilization of the probe DNA on the Au(nano)-CNT/PAN(nano) films and rose further after the hybridization of the probe DNA. The remarkable difference between the R(et) value at the DNA-immobilized electrode and that at the hybridized electrode could be used for the label-free EIS detection of the target DNA. The loading of the DNA probe on Au(nano)-CNT/PAN(nano) films was greatly enhanced and the sensitivity for the target DNA detection was markedly improved. The sequence-specific DNA of phosphinothricin acetyltransferase (PAT) gene and the polymerase chain reaction (PCR) amplification of nopaline synthase (NOS) gene from transgenically modified beans were determined with this label-free EIS DNA detection method. The dynamic range for detecting the PAT gene sequence was from 1.0 x 10(-12)mol/L to 1.0 x 10(-6)mol/L with a detection limit of 5.6 x 10(-13)mol/L.
Article
The adsorption of fibrinogen on to platinum and carbon and of albumin on to carbon was investigated for various changes of the surface by recording the variations of the double-layer capacitance of the electrochemical interface during adsorption, as a function of time. The rate of the second step of the adsorption decreased with increasing negative charge on to platinum but was charge-independent on to carbon. In contrast, on both surfaces, the rate of the first step and the area of the electrode surface in close contact with adsorbed proteins were both found to increase with increasing negative charge of the surface, although at pH 7.4 albumin and fibrinogen are negatively charged. The hypothesis of ion coadsorption inside the proteic layer has been proposed to account for this result.
Article
The research on our flow-injection, label-free, non-faradaic impedimetric immunosensor for interferon-gamma (IFN-gamma) has been extended. The sensor is prepared by immobilization of anti-IFN-gamma antibodies on a self-assembled monolayer (SAM) of acetylcysteine, deposited on polycrystalline gold. A multi-frequency impedance method is described, which allows time-resolved measurement of Nyquist plots. To these plots, an equivalent circuit was fitted, which is discussed in terms of a two-layer structure (inner and outer layer) of the interfacial region. Because binding of IFN-gamma mainly causes a decrease of Q (a constant-phase element), this element is considered as the outer layer. Several aspects of the impedimetric sensor response are studied, including the dependence on detection frequency, target concentration and applied dc potential. For quantitative detection of IFN-gamma, an optimum of the signal-to-noise (S/N) ratio of the out-of-phase impedance component (Z'') was found at about 100 Hz. At a dc-potential of +0.2 V versus a saturated calomel reference electrode, the sensor response is higher than at 0.0 V. Logarithmic dose-response curves of IFN-gamma in the concentration range of 10(-18) to 10(-9) M were obtained using two procedures: by successive injections over a single electrode, and by using freshly prepared electrodes for each measurement. Using the latter method, the repeatability is impaired. The need for in situ complementary techniques for a correct interpretation of the studied parameters is discussed.
Article
Carbon nanotubes (CNTs) exhibit a unique combination of excellent mechanical, electrical and electrochemical properties, which has stimulated increasing interest in the application of CNTs as components in (bio)sensors. This review highlights various design methodologies for CNT-based biosensors and their employment for the detection of a number of biomolecules. In addition, recent developments in the fields of CNT-based chemiresistors and chemically sensitive field-effect transistors are presented. After a critical discussion of the factors that currently limit the practical use of CNT-based biosensors, the review concludes with an outline of potential future applications for CNTs in biology and medicine.
Article
Magnetoimpedance (MI) changes due to surface modification of the sensitive element caused by human urine, were studied with the aim of creating a robust biosensor working on a principle of electrochemical magnetoimpedance spectroscopy. A biosensor prototype with an as-quenched amorphous ribbon sensitive element was designed and calibrated for a frequency range of 0.5-10 MHz at a current intensity of 60 mA. Measurements as a function of the exposure time were made both in a regime where chemical surface modification and MI measurements were separated as well as in a regime where they were done simultaneously. The MI variation was explained by the change of the surface magnetic anisotropy. It was shown that the magnetoimpedance effect can be successfully employed as a new option to probe the electric features of the Fe(5)Co(70)Si(15)B(10) amorphous ribbon magnetic electrode surface modified by human urine.
Article
Impedance spectroscopy approaches combined with the immunosensor technology have been used for the determination of trace amounts of ciprofloxacin antibiotic belonging to the fluoroquinolone family. The sensor electrode was based on the immobilization of anti-ciprofloxacin antibodies by chemical binding onto a poly(pyrrole-NHS) film electrogenerated on a solid gold substrate. The electrode surface was modified by electropolymerization of pyrrole-NHS, antibody grafting and ciprofloxacin immunoreaction. The sensitive steps of surface modification, cyclic voltammetry (CV) and atomic force microscopy (AFM) imaging have been used for electrode surface characterization. The immunoreaction of ciprofloxacin on the grafted anti-ciprofloxacin antibody directly triggers a signal via impedance spectroscopy measurements which allows the detection of extremely low concentration of 10 pg/ml ciprofloxacin.
Article
Impedance biosensors are a class of electrical biosensors that show promise for point-of-care and other applications due to low cost, ease of miniaturization, and label-free operation. Unlabeled DNA and protein targets can be detected by monitoring changes in surface impedance when a target molecule binds to an immobilized probe. The affinity capture step leads to challenges shared by all label-free affinity biosensors; these challenges are discussed along with others unique to impedance readout. Various possible mechanisms for impedance change upon target binding are discussed. We critically summarize accomplishments of past label-free impedance biosensors and identify areas for future research.