Figures & data
Figure 1. Schematic representation of HIV electrochemical detection on chitosan/Fe3O4 SPE, using MB as an intercalator (Reuse with permission from Elsevier) (Dai Tran et al. Citation2011).
![Figure 1. Schematic representation of HIV electrochemical detection on chitosan/Fe3O4 SPE, using MB as an intercalator (Reuse with permission from Elsevier) (Dai Tran et al. Citation2011).](/cms/asset/f52be109-674c-4204-983a-e83bcf914bd8/ianb_a_1282494_f0001_c.jpg)
Figure 2. Quantitative detection of different target DNA concentrations by SWV is shown (Reuse with permission from Elsevier) (Dai Tran et al. Citation2011).
![Figure 2. Quantitative detection of different target DNA concentrations by SWV is shown (Reuse with permission from Elsevier) (Dai Tran et al. Citation2011).](/cms/asset/60d1d496-8947-4511-8b75-185703317781/ianb_a_1282494_f0002_c.jpg)
Figure 3. (Left) Cyclic voltammogram of different concentration of HIV-1 VLPs after immobilization of fragmented antibody (a) 600 fg/mL, (b) 3 pg/mL, (c) 15 pg/mL, (d) 75 pg/mL, and (e) 375 pg/m, respectively and (Right) linear plot of anodic current peak as a function of HIV-1 VLPs range from 600 fg/mL to 375 pg/mL (R = 0.958) (Reuse with permission from Elsevier) (Lee et al. Citation2013).
![Figure 3. (Left) Cyclic voltammogram of different concentration of HIV-1 VLPs after immobilization of fragmented antibody (a) 600 fg/mL, (b) 3 pg/mL, (c) 15 pg/mL, (d) 75 pg/mL, and (e) 375 pg/m, respectively and (Right) linear plot of anodic current peak as a function of HIV-1 VLPs range from 600 fg/mL to 375 pg/mL (R = 0.958) (Reuse with permission from Elsevier) (Lee et al. Citation2013).](/cms/asset/ff6d678b-67f6-44c4-8e7d-df332834f795/ianb_a_1282494_f0003_c.jpg)
Figure 4. Impedimetric responses of AuNRs sensor with deferiprone and without deferiprone were shown (Reuse with permission from Elsevier) (Narang et al. Citation2015).
![Figure 4. Impedimetric responses of AuNRs sensor with deferiprone and without deferiprone were shown (Reuse with permission from Elsevier) (Narang et al. Citation2015).](/cms/asset/e598df08-dad6-4185-b72e-62d5673f7dd6/ianb_a_1282494_f0004_c.jpg)
Figure 5. (A) Schematic representation of the enzyme-free and label-free ultrasensitive electrochemical DNA biosensor based on long-range self-assembled DNA nanostructures. (B) DPV responses of the gold electrode modified with various oligonucleotides: (a) CP, (b) CP + TD, (c) CP + AP1 + AP2, (d) CP + TD + AP1, and (e) CP + TD + AP1 + AP2. The concentration of TD is 10 pM. The concentrations of AP1 and AP2 are both 1 μM (Reprinted with permission from American Chemical Society) (Chen et al. Citation2012).
![Figure 5. (A) Schematic representation of the enzyme-free and label-free ultrasensitive electrochemical DNA biosensor based on long-range self-assembled DNA nanostructures. (B) DPV responses of the gold electrode modified with various oligonucleotides: (a) CP, (b) CP + TD, (c) CP + AP1 + AP2, (d) CP + TD + AP1, and (e) CP + TD + AP1 + AP2. The concentration of TD is 10 pM. The concentrations of AP1 and AP2 are both 1 μM (Reprinted with permission from American Chemical Society) (Chen et al. Citation2012).](/cms/asset/41cf0836-6f4f-4334-a79f-50a4b3a82ede/ianb_a_1282494_f0005_c.jpg)
Figure 6. A layer of PPy film was electrodeposited on the platinum electrode surface, and then the Au–Ag nanocomposite was bonded directly onto the surface of PPy, which is a layer of polycation. Finally, mercapto oligonucleotide was self-assembled onto the Au–Ag nanocomposite surface.
![Figure 6. A layer of PPy film was electrodeposited on the platinum electrode surface, and then the Au–Ag nanocomposite was bonded directly onto the surface of PPy, which is a layer of polycation. Finally, mercapto oligonucleotide was self-assembled onto the Au–Ag nanocomposite surface.](/cms/asset/9e1b84eb-eaf2-4c58-9664-1bf84d91835d/ianb_a_1282494_f0006_c.jpg)
Figure 7. Schematic representation of preparation of immunosensor array and detection strategy by sandwich-type immunoassay (electrochemical voltammetry analysis) is shown. firstly, the immunosensors were fabricated by layer-by-layer coating MWCNTs, Si-HRP, Chitosan, glutaraldehyde composite on the working electrode; after that, the immunosensors were incubated with primary antibody 1 (Ab1); secondly, the primary Ab1 on the immunosensors were biorecognition with the corresponding antigens Ag; and thirdly, the immunocomplex-coated Ag were reacted with second antibodies labeled with TH/GO (Reprinted with permission from American Chemical Society) (Fang et al. Citation2015).
![Figure 7. Schematic representation of preparation of immunosensor array and detection strategy by sandwich-type immunoassay (electrochemical voltammetry analysis) is shown. firstly, the immunosensors were fabricated by layer-by-layer coating MWCNTs, Si-HRP, Chitosan, glutaraldehyde composite on the working electrode; after that, the immunosensors were incubated with primary antibody 1 (Ab1); secondly, the primary Ab1 on the immunosensors were biorecognition with the corresponding antigens Ag; and thirdly, the immunocomplex-coated Ag were reacted with second antibodies labeled with TH/GO (Reprinted with permission from American Chemical Society) (Fang et al. Citation2015).](/cms/asset/79940575-fffb-456f-afb8-3994c0f213d3/ianb_a_1282494_f0007_c.jpg)
Figure 8. DPV of SWCNT/AuNP modified gold electrodes modified with Fc-pepstatin conjugate in the presence of different concentrations of HIV-1 PR at: (a) 0 pM, (b) 5 pM, (c) 10 pM, (d) 100 pM, and (e) 1000 pM. Ag/AgCl was used as the reference electrode at 100 mV/s. The assay buffer consisted of 0.1 M sodium acetate, 2 M NaClO4, 1 mM EDTA, 1 mM DTT, 10% DMSO, pH 7.4. The E of the Fc/Fc+ couple under the experimental conditions is 448 (5) mV (Reprinted with permission from Taylor & Francis) (Mahmoud and Luong Citation2010).
![Figure 8. DPV of SWCNT/AuNP modified gold electrodes modified with Fc-pepstatin conjugate in the presence of different concentrations of HIV-1 PR at: (a) 0 pM, (b) 5 pM, (c) 10 pM, (d) 100 pM, and (e) 1000 pM. Ag/AgCl was used as the reference electrode at 100 mV/s. The assay buffer consisted of 0.1 M sodium acetate, 2 M NaClO4, 1 mM EDTA, 1 mM DTT, 10% DMSO, pH 7.4. The E of the Fc/Fc+ couple under the experimental conditions is 448 (5) mV (Reprinted with permission from Taylor & Francis) (Mahmoud and Luong Citation2010).](/cms/asset/c7275c38-4359-4933-83a1-64918dafbc48/ianb_a_1282494_f0008_b.jpg)
Figure 9. Schematic illustration protocol of the preparation of ferrocene- pepstatin conjugate/thiolated SWCNT and AuNP modified electrodes and their use for detecting HIV-1 protease and the subsequent assay of HIV-1 protease inhibitors. (Reproduced by permission of The American Chemical Society) (Mahmoud and Luong Citation2008).
![Figure 9. Schematic illustration protocol of the preparation of ferrocene- pepstatin conjugate/thiolated SWCNT and AuNP modified electrodes and their use for detecting HIV-1 protease and the subsequent assay of HIV-1 protease inhibitors. (Reproduced by permission of The American Chemical Society) (Mahmoud and Luong Citation2008).](/cms/asset/dbd4f1d2-6152-4b1b-b1c3-e98fdd536c87/ianb_a_1282494_f0009_c.jpg)
Figure 10. Demonstrated of the fabrication and detection procedure of the immunosensor (by permission from the authors (Gan et al. Citation2013)).
![Figure 10. Demonstrated of the fabrication and detection procedure of the immunosensor (by permission from the authors (Gan et al. Citation2013)).](/cms/asset/7628424b-e0df-4a17-8865-f80f0fbc0591/ianb_a_1282494_f0010_c.jpg)
Figure 11. Schematic illustration of principle of immunosensor using VSNEA. (Left) The VSNEA fabricated and coated by Au. (Center) Artificial peptide sequences attached on Au-coated VSNEA by covalent interaction. (Right) RNAs attached to peptides and current path is blocked reducing Fe(CN)63-/4- redox reaction (Lee et al. Citation2016).
![Figure 11. Schematic illustration of principle of immunosensor using VSNEA. (Left) The VSNEA fabricated and coated by Au. (Center) Artificial peptide sequences attached on Au-coated VSNEA by covalent interaction. (Right) RNAs attached to peptides and current path is blocked reducing Fe(CN)63-/4- redox reaction (Lee et al. Citation2016).](/cms/asset/fc82c515-a859-431f-b10e-037412e3d8b9/ianb_a_1282494_f0011_c.jpg)
Table 1. Some of the studies listed based on electrochemical detection methods.