Highly sensitive, stable and selective hydrogen peroxide amperometric biosensors based on peroxidases from different sources wired by Os-polymer : A comparative study

• A comparison was made between two plant peroxidases, cationic horseradish peroxidase (HRP) and anionic tobacco peroxidase (TOP), combined with a highly cationic osmium polymer [Os(4,4'-dimethyl-2,2'-bipyridine)2poly(N-vinylimidazole)10Cl]+2/+ ([Os(dmp)PVI]+/2+) to develop highly sensitive, stable and selective hydrogen peroxide biosensors. The two different plant peroxidases were individually immobilized onto graphite rod (G) electrodes by a three steps drop-casting procedure consisting of the subsequent deposition of an aqueous solution of ([Os(dmp)PVI]+/2+), followed by a solution of poly(ethyleneglycol) diglycidyl ether (PEGDGE), used as a cross linking agent and finally an aliquot of a solution of cationic HRP or anionic TOP to make HRP/PEGDGE/[Os(dmp)PVI]+/2+/G and TOP/PEGDGE/[Os(dmp)PVI]+/2+/G based electrodes, respectively. Electrochemical experiments were carried out to investigate the influence of the surface charge of the enzyme and the charge of the polymer on the efficiency of the electron transfer (ET) between the enzyme and the wiring redox polymer and the efficiency for electrocatalytic reduction of H2O2. In the case of HRP a decrease in the ET rate was observed due to the repulsion between this enzyme and the polymer, both positively charged, whereas with TOP there was an enhanced ET rate due to the attraction between the anionic enzyme and the cationic polymer. The effects of enzyme loading and pH were investigated. Both peroxidase modified electrodes exhibited a wide dynamic response range (1-500μM H2O2) and a low detection limit (0.3μM H2O2). The TOP based electrode showed a higher sensitivity (470nAμM-1 cm-2) compared to that of the HRP based electrode (300nAμM-1 cm-2) and an improved long-term stability (decrease in 17.3% upon 30days compared with 50% for HRP). Both enzyme electrodes showed a response time of 3s. The HRP based sensor was more sensitive to the presence of phenolic compounds acting as alternative electron donors, whereas the TOP based sensor was virtually interference free. Both HRP and TOP based electrodes were successfully tested in contact lens cleaning samples and real "spiked" samples from different sources such as tap water, milk and dairy products.

Ämnesord

NATURVETENSKAP  -- Kemi -- Analytisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Analytical Chemistry (hsv//eng)

Nyckelord

Electrical wiring

Horseradish peroxidase (HRP)

Hydrogen peroxide (HO)

Osmium redox polymer

Tobacco peroxidase (TOP)

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