Dipolar ruthenium(II) ammine complexes as electron transfer mediators of amperometric glucose sensors

Evaluation of the Oxo‐bridged Dinuclear Ruthenium Ammine Complex as Redox Mediator in an Electrochemical Biosensor

“…The calibration curve (see Figure 4(B)) was linear in the glucose concentration range between 2.52 10 À5 and 1.00 10 À4 mol L À1 and can be represented by the equation( DI (mA) = 3.77x10 À2 + 8.30 10 À4 [Glucose] (mmol L À1 )w ith al inear correlationc oefficient R = 0.9976a nd the limitorder detection (LOD) was 9.63 mmol L À1 .T he standard www.electroanalysis.wiley-vch.de deviationf or six successived eterminations of glucose was 4.4%. Furthermore,t he repeatability inter-day (five different electrodes) wasa lso evaluatedf or a5 .0 10 À5 molL À1 glucose solutioni n0 .1 mol L À1 acetate-buffer solution.R SD of 3.78% was obtained, indicating ah igh repeatability of the electrode fabrication.T he performance of the developedb iosensor wasc ompared with that of other glucose biosensors.T able 1s hows the analytical parameters (operating potential and sensitivity)o f electroanalytical methods usingd ifferent mediators that have been reported for the glucose biosensors.W ec an conclude that the mediator showed good results, confirming the efficiencyo ft his voltammetric biosensor for the detectiono fglucose [13,14,[31][32][33][34][35].…”

“…Consequently,t he choice of the mediator of electron-transfer is certainly important to achieve ah igh sensitivity and selectivity of glucose biosensors.R uthenium complexes offer great advantages compared to complexes of osmium for example,d ue to their lower cost and higher reactivity with GOx [29].M oreover, the low redox potential of the mediator minimizes the oxidation of endogenous species,s uch as ascorbic acid and urica cid [30]. Ther edox potentials recordedb yr uthenium dinuclear polypyridyl oxo-complex [(bpy) 2 (NH 3 )Ru III (m-O)Ru III (NH 3 )(bpy) 2 ] 4 + were morep ositive than thoseo f FAD/FADH 2 (À0.41 V vs. SCE at pH = 7.0) present in the enzyme active center [13,21],t he mediation reaction is considered thermodynamically possible (GOx red (FADH 2 ) + 2Ru(IV)!GOx ox (FAD) + 2Ru(III) + 2H + ). Theo xo-bridged dinuclear ruthenium amine complex can be considered to be ag ood electron-transfer mediator at the observed redox potential (0.13 V vs. SCE).…”

“…glucoseb yt he central metallic cations of the complexi mmobilized in the polymeric film. Nakabayashi and coworkers [13,21] describedt he operation mechanism of the biosensor as ar eactionb etween the analyte and biosensor that is similar to an electrochemical-chemical mechanism in three steps (two chemical and one electrochemical). Thei nitial step is the chemicalo re nzymatic step (biocatalysis), where the glucose oxidasee nzyme specifically converts glucose to gluconolactone,w hich spontaneously hydrolyzes to gluconica cid, with concomitant reduction of O 2 to hydrogen peroxide.T his oxidation reactioni sa ccompanied by the reduction of the flavin adenine dinucleotide (FAD)c ofactor.…”

“…Paulo A. Raymundo-Pereira, [a, b] Ana C. V. Mascarenhas, [a] and Marcos F. S. Te ixeira* [a] 1Introduction Ther edox properties of ruthenium polynuclear oxo-complex have been studied with special attention to the stability of the oxidation states of the metallic cation,a nd many studies are based on qualitative molecular orbital interaction schemes dp (metal) Àpp (ligand) [1][2][3][4].T hese polynuclear oxoc omplexes exhibit electront ransfer processes with multiple steps that result in ah igh stability in different oxidation states and the ability to exchange charges between metallic cations.N otably,awide rangeo fd inuclear ruthenium complexes have been chemically and/or electrochemically studied [5,6].T he complexes [(bpy) 2 5 Ru III ÀOÀ Ru IV (NH 3 ) 4 ÀO-Ru III (NH 3 ) 5 ] 6 + are examples that have been intensively studied by Meyers [7,8] and Kanekos groups [ 9,10],r espectively.T hese complexes were investigated for their ability to catalyse water oxidation in an artificial photosynthetic system [11] and electrocatalytic processes [12].I na ddition, ruthenium dinuclear oxo-complexes can be used as artificial electron-transfer mediators in biosensors [13].H owever,t he ruthenium dinuclear oxo-complex [(bpy) 2 (NH 3 )Ru III (m-O)Ru III (NH 3 )(bpy) 2 ]-(ClO 4 ) 4 has not been studied to date as ar edox mediator in the development of glucoseb iosensors.…”

“…Theu se of artificialr edox mediators allows the flow of electrons from the redox enzyme to the surface of the electrode center, decreasing redox potential and ideally preventing interference by electro-oxidizable species such as ascorbic acid, therefore,i ncreasing the selectivity and sensitivity of the (bio)sensor [14].T he determinationo f the optimal redox mediator for the production of ab iosensor is extremely important for its efficiency.Amedia-tor should be selected that possesses alowerr edox potential than the othere lectrochemically active interfering compounds present in the sample.F urthermore,ahigh electrochemical constant is very desirable,which is important to ensure that the response of the biosensor is not limited by the kinetics of electrodes or by oxygen interference [15].A ni deal mediator is also characterized by reversible kinetics,ahigh chemical stabilityi nb oth reduced and oxidized forms and unreactivity with oxygen [13].T od ate,s everal transition-metalc omplexes such as iron [16][17][18],o smium [19,20] have been investigateda s redox mediators and are the most used, but ruthenium complexes can also be used, due to their higher reactivity with glucose oxidase (GOx) [13,21].…”