Carbon Electrodes Modified with Ruthenium Metallodendrimer Multilayers for the Mediated Oxidation of Methionine and Insulin at Physiological pH

Abstract

A pentaerythritol-based metallodendrimer with ruthenium(II) terpyridine units, Ru(II)Den, catalyzed the oxidation of L-methionine and insulin at pH 7.0. The Ru(II)Den was immobilized on a carbon surface through layer-by-layer electrostatic deposition; the negatively charged polymer, poly(styrene sulfonate), was its counterpart. These bilayers were assembled on a glassy carbon electrode that was first modified by deposition of a layer of the conjugate base of sulfanilic acid and then with quaternized poly(4-vinylpyridine). Reversible voltammetry for the Ru(II/III) redox couple was observed, the current for which increased linearly with layer number, n, of Ru(II)Den up to n = 12. Cyclic voltammetry was used to demonstrate the mediation of L-methionine oxidation by a Ru(II)Den-containing multilayer assembly. Flow injection amperometric determination of insulin at pH 7.0 at this modified electrode yielded a calibration curve with the following characteristics: linear dynamic range, 6 nM-0.4 microM; sensitivity, 225 nA microM(-1); detection limit (k = 3 criterion), 2 nM. Of particular importance was that the sensitivity was proportional to the number of Ru(II)Den layers.

Electrocatalytic Oxidation of Sulfur Containing Amino Acids at Renewable Ni‐Powder Doped Carbon Ceramic Electrode: Application to Amperometric Detection L‐Cystine, L‐Cysteine and L‐Methionine

“…The linear concentration range, sensitivity and detection limit for l-methionine and lcysteine determination were 2 -90 mM, 5.6 mA/mM, 2 mM and 2 -75 mM, 8.1 mA/mM and 0.2 mM, respectively. These analytical parameters are comparable or better than results that reported for analytical determination of selected analytes at the surface of different modified electrodes such as, carbon composite and glassy carbon electrodes modified with Ru(II) metallodendrimer [14,15], dirhodium-substituted polyoxometalate anchored in a xerogel based composite [16] and colloid-gold cysteamine modified carbon paste electrode [17]. The Ni powder doped CCE imparts higher stability onto amperometric measurements of disulfides and l-methionine.…”

“…Although many modified electrodes have been used for detection of thiols, but few of them showed significant electrocatalytic activity for disulfides and l-methionine. Carbon composite and glassy carbon electrodes modified with Ru(II) metallodendrimer [14,15], dirhodium-substituted polyoxometalate anchored in a xerogel based composite [16], colloid-gold cysteamine modified carbon paste electrode [17] have been used for electrocatalytic oxidation and determination of l-cystine and l-methionine. Mercuryplated copper electrode, glassy carbon electrode modified with CePtCl 6 and platinum electrode modified with poly methyl violet have been used for electrocatalytic reduction of l-cystine, sulfur derivatives and sulfur oxoanions [18 -20].…”

A multiwalled carbon nanotube/dihydropyran composite film electrode for insulin detection in a microphysiometer chamber

“…A ruthenium dioxide/cyanoruthenate film on a carbon fiber microelectrode was later utilized at pH 7.4 to monitor chemical secretion by single β cells in response to stimulation with glucose, tolbutamide, and potassium [21]. Redox mediators and electrocatalysts such as ruthenium oxide [22], ruthenium metallodendrimer [23], and iridium oxide [24] layers have been shown to promote the oxidation of insulin at physiological pH and have been used in amperometric detection and quantization of insulin. However, iridium oxide sensors have the disadvantages of pH sensitivity resulting from the proton mediated nature of electron transfer and also the slow nature of proton transport within the film that delays the electrode response [25]; ruthenium oxide and ruthenium metallodendrimer films have mixed redox states leading to complex electron transfer kinetics, with the electrochemical behavior of ruthenium oxide varying between crystal faces [26].…”

Biosensors for Cancer Biomarkers

“…This is both non-specific bindings to blocked Zhuo et al, 2005, in press) and to use of TB as a mediator and H 2 O 2 as a result of reduction feature makes the system more sensitive (Yang et al, 1998;Zhang et al, 2005). Radical cation method was used SAA to bond on GCE electrode (Cheng et al, 2001, Liu et al, 2000Downard and Mohamed, 1999) to the PSAA / GCE modified electrode forming. Sulfonate groups of the modified electrode has been created with TB treatment.…”