Preliminary studies of the enhanced electrochemiluminescence of 2,3-diaminonaphthalene in the presence of specific metal ions

Electrochemiluminescence (ECL) of 200 ppm 2,3-diaminonaphthalene (2,3-DAN) was studied alone and in conjunction with 100 ppm of 34 different metal and non-metal ions and revealed three relatively intense ECL responses from interactions of 2,3-DAN with Au⁺, Fe⁺³ and V⁺⁵. ECL responses from Cr⁺⁶ or Ru⁺³ with 2,3-DAN were less intense, but noteworthy, as was the coloured fluorescent product of the non-metal ion Se⁺⁴ interaction with 2,3-DAN. Several intense 2,3-DAN–metal ion ECL reactions were studied in greater detail and revealed various titration curves with ionic detection limits in the low ppm range, using a fixed level (200 ppm) of 2,3-DAN. © 1998 John Wiley & Sons, Ltd.     

A perovskite-based electrochemiluminescence aptasensor for tetracycline screening

Tetracyclines are currently the most commonly used class of antibiotics, and their residue issue significantly impacts public health safety. In this study, a surface modification of perovskite with cetyltrimethylammonium bromide led to the generation of stable electrochemiluminescence (ECL) emitters in aqueous systems and improved the biocompatibility of perovskite. A perovskite quantum dot-based ECL sensing strategy was developed. Utilizing the corresponding aptamer of the antibiotics, strain displacement reactions were triggered, disrupting the ECL quenching system composed of perovskite and Ag nanoclusters (Ag NCs) on the electrode surface, generating a signal to achieve quantitative detection of several common tetracycline antibiotics. The perovskite quantum dot provided a strong and stable initial signal, while the efficient catalytic activity of the silver cluster enhanced the recognition sensitivity. Tetracycline, chlortetracycline, and oxytetracycline were used as examples to demonstrate the differentiation and quantitative detection through this method. In addition, the aptasensor exhibited analytical performance with the linear range (0.1–10 μM OTC) and good recovery rates of 94.7% to 101.6% in real samples. This approach has the potential to become a sensitive and practical approach for assessing antibiotic residues.     

Electrochemical analysis of the alanine phenylthiohydantoin derivative by cathodic stripping voltammetry

A square-wave cathodic stripping voltammetry method for alanine determination as its phenylthiohydantoin (PTH-alanine) derivative is developed. To this end, all the chemical and instrumental variables affecting the determination of PTH-alanine are optimized. From studies of the mechanisms governing the electrochemical response of PTH-alanine, it was concluded that it is an electrochemically irreversible system with a diffusive-adsorptive reduction phenomenon. Under optimal conditions, the variation of analytical signal (I_p) with PTH-alanine concentration is linear in the 2.4 × 10⁻⁸ − 4.8 × 10⁻⁷ M range, with a LOD of 1.2 × 10⁻⁸ M and a LOQ of 4.2 × 10⁻⁸ M, a RSD (%) less than 11%, and a E_r (%) less than 10%. The optimized method was applied to the determination of PTH-alanine obtained from a synthetic protein after Edman reaction and the results were corroborated by high-performance liquid chromatography with UV detection.     

A cell-free electrochemiluminescence assay for measuring beta1-integrin-ligand interactions

We have developed a cell-free assay for binding of solubilized beta1 integrins to their physiologically relevant ligands using an electrochemiluminescent detection method. The method utilizes ruthenium-conjugated monoclonal antibodies for detection of either purified integrins or, more conveniently, integrin-expressing cell lysates, which are captured on beads coated with extracellular matrix or vascular ligand proteins. For the interaction of alpha1beta1 integrin with collagen IV, a signal of 10-fold over background was generated with samples containing only 10 ng (0.05 pmol) of integrin. This interaction is cation-dependent and can be inhibited by blocking antibodies to the alpha1 subunit. The method was extended to studies of ligand binding by integrins alpha2beta1, alpha4beta1, alpha5beta1, and alpha6beta1. For each integrin-ligand pair, the specificity of the interaction was verified with neutralizing antibodies against the specific integrin. The specific binding signal correlated with the activating ability of the labeled antibody used for detection, although the ability of divalent cations (Mn2+, Mg2+, Ca2+) to support integrin-ligand binding varied dramatically among the various integrin-ligand pairs. The assay provides a simple method for investigating integrin-ligand interactions without avidity and/or signaling effects which can complicate conventional cell-based assay methods.     

Determination of bergenin based on the electrochemiluminescence quenching of tris(2,2′‐bipyridine)‐ruthenium(II)

Quenching effects of bergenin, based on the electrochemiluminescence (ECL) of the tris(2,2′‐bipyridyl)‐ruthenium(II) (Ru(bpy)₃²⁺)/tri‐n‐propylamine (TPrA) system in aqueous solution, is been described. The quenching behavior can be observed with a 100‐fold excess of bergenin over Ru(bpy)₃²⁺. In the presence of 0.1 m TPrA, the Stern–Volmer constant (K_SV) of the ECL quenching is as high as 1.16 × 10⁴ M^?1 for bergenin. The logarithmic plot of the inhibited ECL versus logarithmic plot of the concentration of bergenin was linear over the range 3.0 × 10^?6–1.0 × 10^?4 mol/L. The corresponding limit of detection was 6.0 × 10^?7 mol/L for bergenin (S/N = 3). In the mechanism of quenching it is believed that the competition of the active free radicals between Ru(bpy)₃²⁺/TPrA and bergenin was the key factor for the ECL inhibition of the system. Photoluminescence, cyclic voltammetry, coupled with bulk electrolysis, supports the supposition mechanism of the Ru(bpy)₃²⁺/TPrA–bergenin system. Copyright © 2015 John Wiley & Sons, Ltd.     

Target-cycling synchronized rolling circle amplification strategy for biosensing Helicobacter pylori DNA

Helicobacter pylori is closely linked to many gastric diseases such as gastric ulcers and duodenal ulcers. Therefore, biosensing H. pylori has attracted wide attention from both scientists and clinicians. Here, we proposed an electrochemiluminescence (ECL)-based platform that could sensitively detect H. pylori DNA. In this platform, a novel target-cycling synchronized rolling circle amplification was used for signal amplification. Silver nanoclusters (Ag NCs) were synthesized on the circle DNA products, embedding them with the ability to catalyze the electrochemical reduction of K₂S₂O₈, in turn resulting in rapid consumption of the ECL co-reactant near the working electrode, and leading to a decrease in the ECL emission intensity. In addition to its excellent stability and selectivity, the proposed strategy had a low detection limit of 10 pM, an indication that it can be beneficially applied to test biosamples. Furthermore, a biosensing chip was designed to improve the throughput and shed new light on large-scale clinical biosensing applications.     

Generation of free radicals and electrochemiluminescence from simple aromatic molecules in aqueous solutions.

Oxide-covered aluminium electrodes were used to demonstrate that aromatic compounds, such as the simple derivatives of benzene, can be electrochemically excited at cathodically pulse-polarized conductor/insulator/electrolyte (C/I/E) tunnel junction electrodes (e.g. oxide-covered aluminium electrodes). The primary cathodic process at these electrodes was a tunnel emission of hot electrons into an aqueous electrolyte solution. Fluorescence (FL) and electrochemiluminescence (ECL) spectra were compared and the dependence of the electrochemiluminescence on the concentrations of benzene, toluene, phenol, p-cresol and aniline were measured and detailed mechanisms for the present electrochemiluminescence are proposed.     

Influence of cathodic protection of mild steel on the growth of sulphate‐reducing bacteria at 35°C in marine sediments

In order to protect metallic structures from marine corrosion, cathodic protection using sacrificial anodes or impressed current is widely used. In aerated seawater steel is considered to be protected when a cathodic potential of — 800 mV/SCE (Saturated Calomel Electrode) is applied. However, in many cases, this potential must be lowered due to the presence and activity of microorganisms such as acid‐producing bacteria or sulphate‐reducing bacteria (SRB). SRB are obligate anaerobes using sulphate as an electron acceptor with resultant production of sulfides. Some SRB are able to use hydrogen as an electron donor causing thereby depolarization of steel surfaces.

An experiment was performed in marine sediments to determine the relationship between cathodically produced hydrogen and growth of SRB in marine sediments both at ambiant temperature (Therene, 1988) and at 35°C. Results concerning the latter experiments are reported here.

Analytical techniques included microbiological analyses, lipid biomarker studies and electrochemical measurements including AC impedance spectroscopy. Results indicated a change in the bacterial community structure both on the steel and sediment as a function of time and potential. The results also showed that cathodically‐produced hydrogen promoted the growth of SRB with the Desulfovibrio genus predominating.     

Indirect electrochemiluminescence detection of lysine and histidine separated by capillary electrophoresis based on charge displacement

Indirect electrochemiluminescence (ECL) detection was applied for the analysis of lysine (Lys) and histidine (His) separated by capillary electrophoresis (CE). With the most effective electrophoretic buffer system, which contained 15 mM phosphate buffer (pH = 5.8) and 0.5 mM Tripropylamine (TPA), fast separation of the two basic amino acids could be performed within 7 min. The linear ranges were 10–35 μM, 35–150 μM for Lys; and 5–35 μM, 35–150 μM for His. The detection limits (S/N = 3) were 0.3 μM for Lys and 1.0 μM for His, respectively. The proposed method was also successfully used for the determination of Lys in the oral pharmaceutical formulations. Copyright © 2012 John Wiley & Sons, Ltd.