Sol–gel-immobilized Tris(2,2′-bipyridyl)ruthenium(II) electrogenerated chemiluminescence sensor for high-performance liquid chromatography

Tris(2,2'-bipyridyl)ruthenium (II) complex as a universal reagent for the fabrication of heterogeneous electrochemiluminescence platforms and its recent analytical applications

In recent years, electrochemiluminescence (ECL) has received enormous attention and has emerged as one of the most successful tools in the field of analytical science. Compared with homogeneous ECL, the heterogeneous (or solid-state) ECL has enhanced the rate of the electron transfer kinetics and offers rapid response time, which is highly beneficial in point-of-care and clinical applications. In ECL, the luminophore is the key element, which dictates the overall performance of the ECL-based sensors in various analytical applications. Tris(2,2'-bipyridyl)ruthenium (II) complex, Ru(bpy)32+, is a coordination compound, which is the gold-standard luminophore in ECL. It has played a key role in translating ECL from a "laboratory curiosity" to a commercial analytical instrument for diagnosis. The aim of the present review is to provide the principles of ECL and classical reaction mechanisms-particularly involving the heterogeneous Ru(bpy)32+/co-reactant ECL systems, as well as the fabrication methods and its importance over solution-phase Ru(bpy)32+ ECL. Then, we discussed the emerging technology in solid-state Ru(bpy)32+ ECL-sensing platforms and their recent potential analytical applications such as in immunoassay sensors, DNA sensors, aptasensors, bio-imaging, latent fingerprint detection, point-of-care testing, and detection of non-biomolecules. Finally, we also briefly cover the recent advances in solid-state Ru(bpy)32+ ECL coupled with the hyphenated techniques.

Quantum dots: from fluorescence to chemiluminescence, bioluminescence, electrochemiluminescence, and electrochemistry

During the past decade, nanotechnology has become one of the major forces driving basic and applied research. As a novel class of inorganic fluorochromes, research into quantum dots (QDs) has become one of the fastest growing fields of nanotechnology today. QDs are made of a semiconductor material with tunable physical dimensions as well as unique optoelectronic properties, and have attracted multidisciplinary research efforts to further their potential bioanalytical applications. Recently, numerous optical properties of QDs, such as narrow emission band peaks, broad absorption spectra, intense signals, and remarkable resistance to photobleaching, have made them biocompatible and sensitive for biological assays. In this review, we give an overview of these exciting materials and describe their potential, especially in biomolecules analysis, including fluorescence detection, chemiluminescence detection, bioluminescence detection, electrochemiluminescence detection, and electrochemical detection. Finally, conclusions are made, including highlighting some critical challenges remaining and a perspective of how this field can be expected to develop in the future.

Electrogenerated chemiluminescence detector based on Ru(bpy)3(2+) immobilized in cation exchange resin for high-performance liquid chromatography: An approach to stable detection

In this work, an electrogenerated chemiluminescence (ECL) detector with improved stability was developed for high-performance liquid chromatography (HPLC) detection of hydrochlorothiazide (HCTZ). The detector was prepared by packing cation exchanged resin particles in a glass tube, followed by inserting Pt wires (working electrode) in this tube and sealing. The leakage of Ru(bpy)3(2+) from the resin was compensated by adding a small amount of Ru(bpy)3(2+) in the mobile phase. Factors affected the performance of the proposed ECL detector were investigated. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of HCTZ in the range of 5.0 × 10(-8) g mL(-1)-2.5 × 10(-5) g mL(-1) and the detection limit was 2.0 × 10(-8) g mL(-1) (S/N=3). Application of the detector to the analysis of HCTZ in human serum proved feasible.

Applications of tris(2,2'-bipyridyl)ruthenium(II) in electrochemiluminescence

Electrochemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3)(2+)] has received considerable interest over broad applications due to its remarkably high sensitivity and extremely wide dynamic range. After a brief introduction of the ECL of Ru(bpy)(3)(2+), an overview of our recent research on enhanced ECL, fabrication of solid-state ECL sensors, analytical application of an effective bioassay, and alignment of ECL with capillary electrophoresis (CE) and microchip CE is discussed in detail. Finally, we conclude with a look at the future challenges and prospects of the development of ECL.

Electrochemiluminescence based on quantum dots and their analytical application

This review presents a general description of the electrochemiluminescence (ECL) related to quantum dots (QDs) and their analytical application. It briefly overviews the synthetic route of quantum dots. The basic mechanisms are given for QDs ECL behavior. Finally, new developments and improvements of its application in inorganic substance analysis, organics analysis, immunoassay and aptasensing assay are discussed.

Selective growth of Ag nanodewdrops on Au nanostructures: a new type of bimetallic heterostructure

A new type of bimetallic Au-Ag heterostructured material was prepared by a selective growing strategy of a Ag nanodewdrop on the petal tip of a Au flower using an electrochemical method. The whole process was strictly controlled by forming the reactive tip of the flower petal and passivating the facet along the body of the metal petal using poly(vinyl pyrrolidone) (PVP) coating film. The formed Au-Ag heterostructured flowers (HSFs) were observed to be about 2 microm in diameter and have the Ag particles of about 50 nm settled on the tips of Au petals. The Au-Ag HSFs were found to display the superior properties on the surface-enhanced Raman scattering (SERS). The presence of Ag nanodewdrops could also facilitate the oxidation of Ru(bpy)3(2+) complex in electrogenerated chemiluminescence (ECL) measurements and dramatically enhance the emission intensity. The features of Au-Ag HSFs can promise a new type of heterogeneous bimetallic alloy material for the potential applications in chemical and biological sensors.

Nanostructured materials for electrochemiluminescence (ECL)-based detection methods: recent advances and future perspectives

This review presents a general picture of the last advances and developments (2003-2008) related to novel nanostructured materials for electrochemiluminescence-based biosensors using. It briefly covers the basic mechanisms of ECL detection, and the recent developments in fabrication of solid-state ECL sensors using nanostructured materials such as carbon nanotubes, metal nanoparticles, quantum dots, thin films of metallopolymers and of inorganic metal complexes. Finally, challenges and perspectives of the use of such materials for biomedical diagnostics are discussed.

Developments and Applications of Electrogenerated Chemiluminescence Sensors Based on Micro- and Nanomaterials

A variety of recent developments and applications of electrogenerated chemiluminescence (ECL) for sensors are described. While tris(2,2′-bipyridyl)-ruthenium(II) and luminol have dominated and continue to pervade the field of ECL-based sensors, recent work has focused on use of these lumophores with micro- and nanomaterials. It has also extended to inherently luminescent nanomaterials, such as quantum dots. Sensor configurations including microelectrode arrays and microfluidics are reviewed and, with the recent trend toward increased use of nanomaterials, special attention has been given to sensors which include thin films, nanoparticles and nanotubes. Applications of ECL labels and examples of label-free sensing that incorporate nanomaterials are also discussed.

On-line coupling of solid-phase extraction, derivatization reaction and spectrophotometry by sequential injection analysis: Application to trifluoperazine assay in human urine

INTRODUCTION

This study deals with a new methodology of on-line solid-phase extraction (SPE), derivatization reaction and spectrophotometric measurement utilizing sequential injection analysis (SIA) technique. The method was applied for the assay of trifluoperazine in human urine.

METHODS

An SPE procedure was automated to perform sample clean-up, extraction and preconcentration into a homemade microcolumn connected to a SIA manifold. Unlike previous SIA methods, a simple SIA manifold included one syringe pump and one multi-position valve was constructed. This offered simplicity and rapidity to the proposed method (sampling frequency 11 sample h(-1)). Spectrophotometric measurement was based on a fast oxidation of trifluoperazine by Ce(IV) in sulfuric acidic media resulting in a spectrophotometrically detectable chromophore measured at wavelength 500 nm. The SPE procedure was optimized by the univariate method while the derivatization reaction and spectrophotometric measurement were optimized by multivariate methods.

RESULTS

The method was linear in a range of 70-200 ng ml(-1) and accurate with a recovery of 92.7%. Relative standard deviation of repeatability (n=10 in a day) and intermediate precision (n=5 over a week) did not exceed 4.3% indicating satisfactory precision. The limits of detection and quantification were 18.2 and 55.2 ng ml(-1), respectively. The sensitivity of the method was improved by the preconcentration, the use of extended pathlength in the detection device and the optimization of absorbance measurement. The method is selective in the presence of chlordiazepoxide, which is sometimes taken in combination with trifluoperazine.

DISCUSSION

The method is suitable for the application of overdose and therapeutic drug monitoring in human urine.

Determination of trimethylamine in fish by capillary electrophoresis with electrogenerated tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection

A capillary electrophoresis with electrogenerated chemiluminescence (CE-ECL) method for the determination of trimethylamine (TMA) in fish was studied. In the presence of TMA, ECL from the reaction of analyte and in situ generated tris(2,2'-bipyridyl)ruthenium(III) [Ru(bpy)(3) (3+)] at electrode surface could be produced. The ECL detection was performed using a Pt working electrode biased at 1.23 V (vs. Ag/AgCl) potential in a 10 mmol/L sodium borate buffer solution, pH 9.2, containing 3 mmol/L Ru(bpy)(3) (2+). A linear calibration curve (correlation coefficient = 0.9996) was obtained in the range 8 x 10(-5)-4 x 10(-8) mol/L for TMA concentration. Recoveries obtained were in the range 98.78-101.46%. The method was successfully applied for the assay of TMA in fish, in combination with solid phase extraction (SPE) disks for sample clean-up and enrichment.

A novel alcohol dehydrogenase biosensor based on solid-state electrogenerated chemiluminescence by assembling dehydrogenase to Ru(bpy)32+–Au nanoparticles aggregates

Based on electrogenerated chemiluminescence (ECL), a novel method for fabrication of alcohol dehydrogenase (ADH) biosensor by self-assembling ADH to Ru(bpy)(3)(2+)-AuNPs aggregates (Ru-AuNPs) on indium tin oxide (ITO) electrode surface has been developed. Positively charged Ru(bpy)(3)(2+) could be immobilized stably on the electrode surface with negatively charged AuNPs in the form of aggregate via electrostatic interaction. On the other hand, AuNPs are favourable candidates for the immobilization of enzymes because amine groups and cysteine residues in the enzymes are known to bind strongly with AuNPs. Moreover, AuNPs can act as tiny conduction centers to facilitate the transfer of electrons. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate, and it displayed wide linear range, high sensitivity and good stability.

Chemiluminescence Detection of Five-membered Heteroaromatic Compounds Using Electrogenerated Tris(2,2'-bipyridine)-ruthenium(III)

Heteroaromatic compounds, such as 2,5-dimethylthiophene, 2,5-dimethylpyrrole, and 2,5-dimethylfuran, were found to act as reducing agents for the tris(2,2'-bipyridine)ruthenium(III), Ru(bpy)3(3+), chemiluminescent reaction. In order to characterize the chemiluminescent reaction of Ru(bpy)3(3+) with heteroaromatic compounds, we have investigated various mono-, di-, and tri-heteroaromatic compounds. The pi-electron density and stability of aromatic rings influence the chemiluminescent efficiency of the reaction. Above all, 2,5-dimethylthiophene produced strong chemiluminescence under acidic conditions. In addition, we confirmed that the rate of the chemiluminescent reaction of Ru(bpy)3(3+) with 2,5-dimethylthiophene is very fast.

Electrogenerated chemiluminescence biosensor based on Ru(bpy)32+ and dehydrogenase immobilized in sol–gel/chitosan/poly(sodium 4-styrene sulfonate) composite material

A new electrogenerated chemiluminescence biosensor was fabricated by immobilizing ECL reagent Ru(bpy)3(2+) and alcohol dehydrogenase in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) (PSS) organically modified composite material. The component PSS was used to immobilize ECL reagent Ru(bpy)3(2+) by ion-exchange, while the addition of chitosan was to prevent the cracking of conventional sol-gel-derived glasses and provide biocompatible microenvironment for alcohol dehydrogenase. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate and it was much simpler than previous double-layer design. The detection limit was 9.3 x 10(-6) M for alcohol (S/N=3) with a linear range from 2.79 x 10(-5) to 5.78 x 10(-2) M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.

Tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence

This paper critically reviews analytical applications of the chemiluminescence from tris(2,2'-bipyridyl)ruthenium(II) and related compounds published in the open literature between mid-1998 and October 2005. Following the introduction, which summarises the reaction chemistry and reagent generation, the review divides into three major sections that focus on: (i) the techniques that utilise this type of detection chemistry, (ii) the range of analytes that can be determined, and (iii) analogues and derivatives of tris(2,2'-bipyridyl)ruthenium(II).