DNA Sensor with a Dipyridophenazine Complex of Osmium(II) as an Electrochemical Probe

Maruyama, Kenichi; Mishima, Yuji; Minagawa, Keiji; Motonaka, Junko

doi:10.1021/ac011148j

Cited by 71 publications

(47 citation statements)

References 37 publications

(47 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The most promising indicators are the metal complexes containing the dipyrido[3,2-a :2 0 ,3 0 -c]phenazine (dppz) ligand, which have been found to intercalate into DNA with high affinity (K = 10 6 -10 7 M À1 ) due to its extended aromatic structure [29,34]. Not surprisingly, sensitive DNA assays have been reported using Ru-and Os-dppz complexes as either electrochemical or fluorescent probe [30,31,35].…”

Section: Introductionmentioning

confidence: 99%

A new chemically amplified electrochemical system for the detection of biological affinity reactions: direct and competitive biotin assay

Guo

Yang²

2005

Analyst

View full text Add to dashboard Cite

A newly developed chemically amplified electrochemical detection system was applied to the quantitation of DNA in solution. The system employed Ru(bpy) 2 dppz (bpy = 2,2 0 -bipyridine, dppz = dipyrido[3,2-a :2 0 ,3 0 -c]phenazine), a high-affinity DNA intercalator, as the electrochemical indicator, oxalate as the sacrificial electron donor to chemically amplify the electrochemical signal, and tin-doped indium oxide as the working electrode to suppress background current. Intercalation of Ru(bpy) 2 dppz into calf thymus DNA in solution led to a reduction in the oxalate-amplified electrochemical current as compared to a DNA-free solution. The degree of reduction was a function of the concentration of DNA, thus forming the basis for DNA detection. To illustrate the advantages of the new system, a direct comparison was made between amplified (with oxalate) and non-amplified (without oxalate) DNA detection. In the presence of 100 mM oxalate, anodic current of Ru(bpy) 2 dppz was amplified by more than 60 folds, resulting in substantial improvement in signal-to-background ratio. Furthermore, as the DNA concentration was increased, the amplified current decayed much faster than the non-amplified signal, giving rise to higher detection sensitivity. The steeper decay was attributed to slower redox reaction between DNA-intercalated Ru(bpy) 2 dppz and oxalate, as the negatively charged phosphate groups on DNA repelled the anions. Effect of ionic strength was investigated to provide support for the interpretation. As expected, the decay of the amplified response with increasing concentration of DNA became less steep when more NaCl was added into the solution. The opposite effect was observed when tri-propylamine, a cationic electron donor, was used instead of oxalate. With an optimized concentration of 30 mM oxalate and 5 lM Ru(bpy) 2 dppz, calf thymus DNA of as low as 1 pM was detected in solution, which was close to the detection limit of some fluorescence measurements.

show abstract

Section: Introductionmentioning

confidence: 99%

A new chemically amplified electrochemical system for the detection of biological affinity reactions: direct and competitive biotin assay

Guo

Yang²

2005

Analyst

View full text Add to dashboard Cite

show abstract

“…Detection of DNA has also been accomplished using electroactive labels either covalently or noncovalently attached to DNA, such as [21]. A detection limit of 1 fmol and 160 pg mL À1 was achieved, respectively.…”

mentioning

confidence: 99%

Determination of Surface-Immobilized Double-Stranded DNA Using a Metallointercalator and Catalytic Voltammetry

2006

View full text Add to dashboard Cite

Abstract. DNA films immobilized on an indium tin oxide (ITO) electrode surface were detected and determined employing a high-affinity intercalator, Ru(bpy) 2 (dppz) 2þ (bpy ¼ 2,2 0 -bipyridine, dppz ¼ dipyrido[3,2-a:2 0 ,3 0 -c]phenazine), as a redox indicator, and oxalate as a sacrificial electron donor in solution to chemically amplify the voltammetric signal of the indicator. Nucleic acids were immobilized on ITO by layer-by-layer electrostatic adsorption, using avidin as the first layer and nucleic acid as the second layer. In quartz crystal microbalance (QCM) measurements on an avidin-coated gold surface, the amount of adsorption from a 200 mg mL À1 nucleic acid solution was found to be 3.2 ng mm À2 for both double-stranded (ds-) and single-stranded (ss-) calf-thymus DNA as well as polycytidylic acid (Poly-C). After binding with Ru(bpy) 2 (dppz) 2þ (Ru-dppz), voltammetry of the ds-DNA film on ITO was carried out in an indicator-free phosphate buffer. An anodic peak at about 1.15 V was observed, and it was assigned to Ru-dppz oxidation. When measured in an oxalate buffer, however, a catalytic current was observed due to the oxidation of oxalate by electrochemically generated Ru(bpy) 2 (dppz) 3þ , resulting in a 120-fold increase in the signal. Since oxalate itself produces a very low oxidation current on ITO, catalytic voltammetry produces about a 14-fold improvement in the signal-to-blank ratio over the nonamplified determination. As a result, ds-DNA adsorbed from 20 ng mL À1 solution could be detected, which was estimated by QCM to be 160 pg mm À2 on the surface. The catalytic current of ds-DNA was substantially higher than that of ss-DNA and poly-C, indicative of selective binding of the redox indicator to ds-DNA. The results serve as a basis for the catalytic voltammetric detection of DNA hybridization in future work.

show abstract

“…Their oxidation potential is high enough to oxidize Tyr, and can be finetuned easily by changing the ligands [100,101]. ITO was selected as the working electrode because it has a wide potential window (up to 2 V), and the background current from direct Tyr oxidation is very low.…”

Section: Basic Work: Electrocatalytic Oxidation Of Tyrosinementioning

confidence: 99%

Electrocatalytic oxidation of tyrosines shows signal enhancement in label-free protein biosensors

Wei

Famouri

Guo

2012

TrAC Trends in Analytical Chemistry

View full text Add to dashboard Cite

Label-free electrochemical (EC) protein biosensors that derive electrical signal from redox-active amino acid (AA) residues can avoid disruption of delicate protein structures, and thus provide a great opportunity to reveal valid information about protein functions. However, the challenge is that such a signal is usually very limited due to the sluggish EC reaction of free AAs on most common electrodes and slow electron-transfer rates from the deeply-buried AA residues in a protein to the electrode. Signal enhancement therefore becomes crucial. We first survey recent progress in this area.We present a signal-enhancing system that relies on the electrocatalytic oxidation of tyrosine mediated by osmium bipyridine or phenoxazine complexes. We describe several applications of label-free protein EC biosensors based on this detection principle for the analysis of protein functions, including the monitoring of protein-conformation change, study of ligand/protein binding, and detection of protein oxidative damage and protein phosphorylation.We describe related works on protein-function analysis using other signal-enhancing methods. The results suggest that labelfree EC protein biosensors are suitable for the rapid survey of protein functions due to their fast response, ease of integration, cost effectiveness and convenience. Proof-of-concept work on the application of our system is paving the way for bio-analytical detections and protein-function analysis in future work. ª

show abstract

DNA Sensor with a Dipyridophenazine Complex of Osmium(II) as an Electrochemical Probe

Cited by 71 publications

References 37 publications

A new chemically amplified electrochemical system for the detection of biological affinity reactions: direct and competitive biotin assay

A new chemically amplified electrochemical system for the detection of biological affinity reactions: direct and competitive biotin assay

Determination of Surface-Immobilized Double-Stranded DNA Using a Metallointercalator and Catalytic Voltammetry

Electrocatalytic oxidation of tyrosines shows signal enhancement in label-free protein biosensors

Contact Info

Product

Resources

About