Highly sensitive and rapid gas biosensor for formaldehyde based on an enzymatic cycling system

Abstract

An enzymatic cycling system for detecting formaldehyde in water and indoor environments has been developed. The system is based on both the dehydrogenation of formaldehyde and the reduction of nicotinamide adenine dinucleotide (NAD +) in the presence of formaldehyde dehydrogenase. NADH generated in the reaction then reduces 4-[3-(2-methoxy-4-nitrophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-l,3-benzene disulfonate sodium salt (WST-8) to yellow WST-8 formazan in the presence of enzyme diaphorase. The quantity of formaldehyde can be detected by the color change resulting from the formation of WST-8 formazan. The assay solution was optimized with respect to the pH, type of buffer, and enzyme and WST-8 concentrations. The limit of detection for formaldehyde in water was found to be 10 ppb after 3 min. The assay solution also displayed a highly selective response to formaldehyde over other pollutant gases present in indoor air. In addition, formaldehyde gas was detected after bubbling prepared formaldehyde/air mixtures with known formaldehyde concentrations in assay solutions. The limit of detection for formaldehyde gas was 1.5 ppb after 5 min. This system can quickly and accurately detect low concentration of formaldehyde in water and gas.

Analytical chemistry of carbonyl compounds in indoor air

“…A diaphorase enzyme then transfers NADH and a colorless tetrazolium salt into NAD + and a colored formazan derivative. A further development of this method was published by Monkawa et al , 75 who used the water soluble tetrazolium salt WST-8. In principle, it is also possible to determine the formaldehyde concentration by means of absorption measurements, although optical comparison has prevailed in the quick tests for reasons of simplicity.…”

High-Tech and Nature-Made Nanocomposites and Their Applications in the Field of Sensors and Biosensors for Gas Detection

“…As seen before, formaldehyde is often the target gas for detection, since its presence in work environments, even at low concentrations, can cause long-lasting damage to workers. A two-enzyme cycle system has been proposed for its detection [ 83 ]. The first enzyme is formaldehyde dehydrogenase which, in the presence of coenzyme NAD + , produces formic acid and coenzyme NADH.…”

Crystal structure of thermostable acetaldehyde dehydrogenase from the hyperthermophilic archaeon Sulfolobus tokodaii

“…Thermostable ALDHs can be used as biosensors for the detection of these aldehydes. A biosensor for formaldehyde has been developed using a thermostable ALDH which exhibits high activity towards formaldehyde (Monkawa et al, 2015). However, there have been no reports of a biosensor for acetaldehyde using a thermostable ALDH.…”