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A highly sensitive and selective electrogenerated chemiluminescence (ECL) biosensor was developed for the determination of matrix metalloproteinase 3 (MMP-3) in serum via the target-induced cleavage of an oligopeptide. One ECL probe (named as Ir-peptide) was synthesized by covalently linking a new cyclometalated iridium(III) complex ([(3-pba)2Ir(bpy-COOH)](PF6)) (3-pba = 3-(2-pyridyl) benzaldehyde, bpy-COOH = 4′-methyl-2,2′-bipyridine-4-carboxylic acid) with an oligopeptide (CGVPLSLTMGKGGK). An ECL biosensor was fabricated by firstly casting Nafion and gold nanoparticles (AuNPs) on a glassy carbon electrode and then self-assembling both of the ECL probes, 6-mercapto-1-hexanol and zwitterionic peptide, on the electrode surface, from which the AuNPs could be used to amplify the ECL signal and Ir-peptide could serve as an ECL probe to detect the MMP-3. Thanks to the MMP-3-induced cleavage of the oligopeptide contributing to the decrease in ECL intensity and the amplification of the ECL signal using AuNPs, the ECL biosensor could selectively and sensitively quantify MMP-3 in the concentration range of 10–150 ng·mL−1 and with both a limit of quantification (26.7 ng·mL−1) and a limit of detection (8.0 ng·mL−1) via one-step recognition. In addition, the developed ECL biosensor showed good performance in the quantization of MMP-3 in serum samples, with a recovery of 92.6% ± 2.8%–105.6% ± 5.0%. An increased level of MMP-3 was found in the serum of rheumatoid arthritis patients compared with that of healthy people. This work provides a sensitive and selective biosensing method for the detection of MMP-3 in human serum, which is promising in the identification of patients with rheumatoid arthritis. [ABSTRACT FROM AUTHOR]

Multi-analyte real-time interrogation of cellular activity allows for the potential discovery of novel insights into disease. In this report, the addition of electrochemical biosensors to a previously developed platform utilizing Au microfabricated electrodes was explored. Glucose oxidase was immobilized at the electrode surface with an osmium redox polymer, using hand-casting and electrodeposition techniques, allowing for the first comparison of deposition techniques at a Au microfabricated array. This preliminary work is the first step toward the goal of creating a multi-analyte array for cellular analysis. [ABSTRACT FROM AUTHOR]

Abstract: An amperometric third-generation hydrogen peroxide biosensor was designed by immobilizing hemoglobin (Hb) on a glassy carbon electrode modified with multiwall carbon nanotubes (MWNT). The direct electron transfer of the Hb immobilized on the MWNT-modified electrode was observed. The formal potential of the immobilized Hb was −0.241V versus Ag/AgCl (3M NaCl) and the heterogeneous electron transfer rate constant was 0.58s−1 in a 0.20M acetate buffer solution (pH 5.4). The immobilized Hb exhibited excellent electrocatalytic activity to reduce hydrogen peroxide in the absence and presence of oxygen, which facilitated designing an amperometric third-generation biosensor for hydrogen peroxide. In the presence of oxygen, the response to hydrogen peroxide of the designed biosensor at a potential of −0.35V was linear in the concentration range from 6.0×10−6 to 6.0×10−3 M, and the detection limit was 1.2×10−6 M. The relative standard deviation was 2.4% for nine successive assays at 1.0×10−5 M hydrogen peroxide. The designed biosensor was applied to the determination of hydrogen peroxide in pharmaceutical injections with high sensitivity and rapid response. [Copyright &y& Elsevier]

A label-free electrochemical impedance spectroscopy (EIS) biosensor for highly sensitive detection of cardiac troponin I (TnI) as a model target was developed by employing gold nanoparticle (GNPs) modified glassy carbon electrode (GCE) as a base electrode. A special peptide (CFYSHSFHENWPS) was used as molecular recognition probe. GNPs were firstly electrochemically deposited onto the surface of GCE and polyethylene glycol was then used to block any remaining sites of the surface of GCE. The biosensor was fabricated by thiol self-assembling the peptide probe onto the surface of gold nanoparticles and finally blocking any remaining sites of the surface of GNPs using 6-mercapto-1-hexanol. A suitable equivalent electrical circuit consisting of parallel double Randles circuit with phase angle elements greatly fits the experiment electrochemical cell. Upon the binding of TnI, the charge transfer resistance (R ct ) of the biosensor was logarithmically direct proportional to the concentration of TnI in the range from 15.5 pg/mL to 1.55 ng/mL with a detection limit of 3.4 pg/mL. It was found that GNPs modified GCE as a platform for the immobilization of the peptide can greatly reduce the background EIS signal and enhance the EIS response to the target. This biosensor has been used for assay of real serum sample with satisfactory results. This work demonstrates that GNPs modified GCE for the immobilization of molecular recognition element is promising platform for the development of label-free electrochemical biosensors for the determination of special proteins. [ABSTRACT FROM AUTHOR]

Two electrogenerated chemiluminescence (ECL) biosensors for selective and sensitive detection of Escherichia coli O157:H7 were first designed by employing the antimicrobial peptide Magainin I as a biological recognition element and the ruthenium complex (Ru1) as an ECL label. In a direct format, the biosensor (I) was fabricated by self-assembling the Ru1-labeled peptide taken as a capture and signal probe onto the gold electrode surface. This system showed that the decreased ECL intensity was logarithmically proportional to the concentration of E. coli O157:H7 in the range of 1.0 × 10 3 –5.0 × 10 5 CFU/mL, with a detection limit of 2.3 × 10 2 CFU/mL. In a sandwich format, the biosensor (II) was fabricated by self-assembling the modified Magainin I taken as capture probe onto the gold electrode surface. After E. coli O157:H7 was captured by the capture probe on the biosensor (II) and then bound with the Ru1-labeled peptide as the signal probe, the increased ECL intensity was logarithmically proportional to the concentration of E. coli from 5.0 × 10 2 CFU/mL to 5.0 × 10 5 CFU/mL, with a detection limit of 1.2 × 10 2 CFU/mL. Importantly, the designed ECL biosensors showed a satisfactory selectivity in discriminating the gram-negative E. coli O157:H7 from gram-positive bacteria, and pathogenic from nonpathogenic E. coli . The strategy of using a Ru1-labeled peptide as a capture/signal probe is a promising approach to designing ECL biosensors for highly sensitive and rapid detection of E. coli O157:H7; this approach could be extended to the design of ECL biosensors for other desired bacteria as well. [ABSTRACT FROM AUTHOR]

A highly selective and sensitive electrogenerated chemiluminescence (ECL) biosensor for the detection of prostate PC-3 cancer cells was designed using a prostate specific antibody as a capture probe and ruthenium complex-labelled wheat germ agglutinin as a signal probe. The ECL biosensor was fabricated by covalently immobilising the capture probe on a graphene oxide-coated glassy carbon electrode. Target PC-3 cells were selectively captured on the surface of the biosensor, and then, the signal probe was bound with the captured PC-3 cells to form a sandwich. In the presence of tripropylamine, the ECL intensity of the sandwich biosensor was logarithmically directly proportion to the concentration of PC-3 cells over a range from 7.0 × 10 2 to 3.0 × 10 4 cells mL −1 , with a detection limit of 2.6 × 10 2 cells mL −1 . The ECL biosensor was also applied to detect prostate specific antigen with a detection limit of 0.1 ng mL −1 . The high selectivity of the biosensor was demonstrated in comparison with that of a lectin-based biosensor. The strategy developed in this study may be a promising approach and could be extended to the design of ECL biosensors for highly sensitive and selective detection of other cancer-related cells or cancer biomarkers using different probes. [ABSTRACT FROM AUTHOR]

Abstract: A label-free electrochemical impedance spectroscopy (EIS) biosensor for the sensitive determination and discrimination of alpha-fetoprotein (AFP) was developed by employing wheat-germ agglutinin (WGA) lectin as molecular recognition element. The EIS biosensor was fabricated by adsorbing carboxyl-functionalized single-wall carbon nanotubes (SWNTs) onto a screen-printed carbon electrode (SPCE) and subsequently covalently coupling WGA onto the surface of the SWNTs-modified electrode. Upon binding of AFP to the biosensor, the electron transfer resistance was increased and the increase in the electron transfer resistance was linearly proportional to the logarithm of the concentration of AFP in the range from 1 to 100ng/L with a detection limit of 0.1ng/L. It was found that the employment of SWNTs as immobilization platform could reduce the background and enhance the EIS response. Moreover, the lectin-based biosensor array fabricated with different lectins was used to evaluate the glycan expression of AFP N-glycan and discriminate AFP between healthy and cancer patients serum samples. This work demonstrates that the employment of carbon nanotubes as immobilization platform and lectin as molecular recognition element in biosensor array is a promising approach for the determination and discrimination of glycoproteins for cancer diagnosis. The strategy proposed in this work could further be used for high-throughput, label-free profiling of the glycan expression of cancer-related glycoproteins and to develop methods for cancer diagnosis in the early stages. [Copyright &y& Elsevier]

Abstract: A novel electrogenerated chemiluminescence peptide-based (ECL-PB) biosensor for highly sensitive and selective determination of prostate-specific antigen (PSA) was developed. A helix peptide (CHSSKLQK) was served as a molecular recognition element and ruthenium bis(2,2′-bipyridine) (2,2′-bipyridine-4,4′-dicarboxylic acid)-N-hydroxysuccinimide ester (Ru(bpy)2(dcbpy)NHS) was used as an ECL label. The helix peptide was labeled with the ECL label at NH2-containing lysine and utilized as ECL probe (Ru-peptide). The ECL-PB biosensor was fabricated by immobilizing the ECL probe onto a gold electrode surface via self-assembling technique through a thiol-containing cysteine at the end of the peptide. The principle of ECL measurement is based on the specific proteolytic cleavage event of Ru-peptide on the gold electrode surface in the presence of PSA, resulting in a decrease of ECL signal. The decreased ECL intensity was directly linear to the concentration of PSA in the range from 1.0×10−10 g/mL to 8.0×10−9 g/mL with a detection limit of 3.8×10−11 g/mL. This work demonstrates that the direct transduction of peptide cleavage events into an ECL signal provides a simple and sensitive method for detecting target protein. [Copyright &y& Elsevier]

Abstract: A novel electrogenerated chemiluminescence (ECL) biosensor for highly sensitive detection of Escherichia coli (E. coli) was first developed by employing Concanavalin A (Con A) as a biological recognition element and bis(2,2′-bipyridine)-4′-methyl-4-carboxybipyridine ruthenium (II) (Ru1) complex as the detector. The ECL biosensor was fabricated by adsorbing carboxyl-functionalised single-wall carbon nanotubes (SWNTs) onto a paraffin-impregnated graphite electrode and further covalently coupling the Ru1–Con A probe onto the surface of the SWNT-modified electrode. Upon the binding of E. coli O157:H7 (as a model target), the biosensor showed a decreased ECL intensity in the presence of tri-n-propylamine (TPrA), which was in logarithmically direct proportion to the concentration of E. coli over a range from 5.0×102 to 5.0×105 cells/mL. The detection limit of this sensor was 127cells/mL. Additionally, the ECL biosensor also showed satisfactory selectivity in discriminating gram-negative E. coli from gram-positive bacteria. The strategy developed in this study may be a promising approach and could be extended to the design of ECL biosensors for highly sensitive and rapid detection of other desired bacteria. [Copyright &y& Elsevier]

Abstract: A novel electrogenerated chemiluminescence (ECL) biosensor for highly sensitive and selective detection of mercury ion was developed on the basis of mercury-specific oligonucleotide (MSO) served as a molecular recognition element and the ruthenium(II) complex (Ru1) as an ECL emitting species. The biosensor was fabricated on a glassy carbon electrode coated with a thin layer of single wall carbon nanotubes, where the ECL probe, NH2-(CH2)6-oligo(ethylene oxide)6-MSO↔Dend-Ru1, was covalently attached. The Dend-Ru1 pendant was prepared by covalent coupling Ru1 with the 4th generation polyamidoamine dendrimer (Dend), in which each dendrimer contained 35 Ru1 units so that a large amplification of ECL signal was obtained. Upon binding of Hg2+ to thymine (T) bases of the MSO, the T–Hg–T structure was formed, and the MSO changed from its linear shape to a “hairpin” configuration. Consequently, the Dend-Ru1 approached the electrode surface resulting in the increase of anodic ECL signal in the presence of the ECL coreactant tri-n-propylamine. The reported biosensor showed a high reproducibility and possessed long-term storage stability (92.3% initial ECL recovery over 30 day''s storage). An extremely low detection limit of 2.4pM and a large dynamic range of 7.0pM to 50nM Hg2+ were obtained. An apparent binding constant of 1.6×109 M−1 between Hg2+ and the MSO was estimated using an ECL based extended Langmuir isotherm approach involving multilayer adsorption. Determination of Hg2+ contents in real water samples was conducted and the data were consistent with the results from cold vapor atomic fluorescence spectroscopy. [Copyright &y& Elsevier]

Abstract: A highly reproducible and sensitive signal-on electrogenerated chemiluminescence (ECL) biosensor based on the DNAzyme for the determination of lead ion was developed. The ECL biosensor was fabricated by covalently coupling 5′-amino-DNAzyme-tagged with ruthenium bis (2,2′-bipyridine) (2,2′-bipyridine-4,4′-dicarboxylic acid)-ethylenediamine (Ru1-17E′) onto the surface of graphite electrode modified with 4-aminobenzoic acid, and then a DNA substrate with a ribonucleotide adenosine hybridized with Ru1-17E′ on the electrode. Upon binding of Pb2+ to the Ru1-17E′ to form a complex which catalyzed the cleavage of the DNA substrate, the double-stranded DNA was dissociated and thus led to a high ECL signal. The signal linearly increases with the concentration of Pb2+ in the range from 5.0 to 80pM with a detection limit of 1.4pM and a relative standard derivation of 2.3%. This work demonstrates that using DNAzyme tagged with ruthenium complex as an ECL probe and covalently coupling method for the fabrication of the ECL biosensor with high sensitivity, good stability and significant regeneration ability is promising approach. [Copyright &y& Elsevier]

Abstract: A label-free and sensitive faradic impedance spectroscopy (FIS) aptasensor based on target-induced aptamer displacement was developed for the determination of lysozyme as a model system. The aptasensor was fabricated by self-assembling the partial complementary single strand DNA (pcDNA)–lysozyme binding aptamer (LBA) duplex on the surface of a gold electrode. To measure lysozyme, the change in interfacial electron transfer resistance of the aptasensor using a redox couple of [Fe(CN)6]3−/4− as the probe was monitored. The introduction of target lysozyme induced the displacement of the LBA from the pcDNA–LBA duplex on the electrode into the solution, decreasing the electron transfer resistance of the aptasensor. The decrease in the FIS signal is linear with the concentration of lysozyme in the range from 0.2nM to 4.0nM, with a detection limit of 0.07nM. The fabricated aptasensor shows a high sensitivity, good selectivity and satisfactory regeneration. This work demonstrates that a high sensitivity of the fabricated aptasensor can be obtained using a relatively short pcDNA. This work also demonstrates that the target-induced aptamer displacement strategy is promising in the design of an electrochemical aptasensor for the determination of lysozyme with good selectivity and high sensitivity. [Copyright &y& Elsevier]

Abstract: A novel electrogenerated chemiluminescence aptamer-based (ECL-AB) biosensor for the determination of a small molecule drug is designed employing cocaine-binding aptamer as molecular recognition element for cocaine as a model analyte and ruthenium complex served as an ECL label. A 5′-terminal cocaine-binding aptamer with the ECL label at 3′-terminal of the aptamer was utilized as an ECL probe. The ECL-AB biosensors were fabricated by immobilizing the ECL probe onto a gold electrode surface via thiol-Au interactions. An enhanced ECL signal is generated upon recognition of the target cocaine, attributed to a change in the conformation of the ECL probe from random coil-like configuration on the probe-modified film to three-way junction structure, in close proximity to the sensor interface. The integrated ECL intensity versus the concentration of cocaine was linear in the range from 5.0×10−9 to 3.0×10−7 M. The detection limit was 1.0×10−9 M. This work demonstrates that the combination of a highly binding aptamer to analyte with a highly sensitive ECL technique to design ECL-AB biosensor is a great promising approach for the determination of small molecule drugs. [Copyright &y& Elsevier]