Formaldehyde-sensitive sensor based on recombinant formaldehyde dehydrogenase using capacitance versus voltage measurements

A new formaldehyde-selective biosensor was constructed using NAD+- and glutathione-dependent recombinant formaldehyde dehydrogenase as a bio-recognition element immobilised on the surface of Si/SiO2/Si3N4 structure. Sensor's response to formaldehyde was evaluated by capacitance measurements. The calibration curves obtained for formaldehyde concentration range from 10 μM to 20 mM showed a broad linear response with a sensitivity of 31 mV/decade and a detection limit about 10 μM. It has been shown that the output signal decreases with the increase of borate buffer concentration and the best sensitivity is observed in 2.5 mM borate buffer, pH 8.40. The response of the created formaldehyde-sensitive biosensor has also been examined in 2.5 mM Tris–HCl buffer, and the shift to the positive bias of the C(V) curves along with the potential axis has been observed, but the sensitivity of the biosensor in this buffer is decreased dramatically to the value of 2.4 mV/decade.