| 18656667 |
Demkiv O, Smutok O, Paryzhak S, Gayda G, Sultanov Y, Guschin D, Shkil H, Schuhmann W, Gonchar M: Reagentless amperometric formaldehyde-selective biosensors based on the recombinant yeast formaldehyde dehydrogenase. Talanta. 2008 Aug 15;76(4):837-46. Epub 2008 Apr 24.
Novel formaldehyde-selective amperometric biosensors were developed based on NAD (+)- and glutathione-dependent formaldehyde dehydrogenase isolated from a gene-engineered strain of the methylotrophic yeast Hansenula polymorpha. Electron transfer between the immobilized enzyme and a platinized graphite electrode was established using a number of different low-molecular free-diffusing redox mediators or positively charged cathodic electrodeposition paints modified with Os-bis-N,N-(2,2'-bipyridil)-chloride ([Os (bpy)(2) Cl]) complexes. Among five tested Os-containing redox polymers of different chemical structure and properties, complexes of osmium-modified poly (4-vinylpyridine) with molecular mass of about 60 kDa containing diaminopropyl groups were selected. The positively charged cathodic paint exhibited the best electron-transfer characteristics. Moreover, the polymer layers simultaneously served as a matrix for keeping the negatively charged low-molecular cofactors, glutathione and NAD (+), in the bioactive layer. Additionally, covering the enzyme/polymer layer with a negatively charged Nafion membrane significantly decreased cofactors leakage and simultaneously enhanced the sensor' stability. The developed sensors revealed a high selectivity to formaldehyde (FA) and a low cross-sensitivity to other substances (such as, e.g. butyraldehyde, propionaldehyde, acetaldehyde, methylglyoxal). The maximum current value was 34.2+/-0.72 microA/mm (2) (3.05 mm diameter electrode) and the apparent Michaelis-Menten constant (K (M)(app)) derived from the FA calibration curves was 120+/-5mM with a linear detection range for FA up to 20mM. The best observed sensitivity for reagentless sensor was 1.8 nA microM (-1) (358 Am (-2) M (-1)). The developed sensors had a good operational and storage stability. The laboratory prototype of the sensor was applied for FA testing in some real samples of pharmaceutical (formidron), disinfectant (descoton forte) and industrial product (formalin). A good correlation was revealed between the concentration values measured using the developed FdDH-based sensor, an enzymatic method and standard chemical methods of FA determination. |
12(0,0,2,2) |