A capacitive biosensor for ultra-trace level urea determination based on nano-sized urea-imprinted polymer receptors coated on graphite electrode surface.

A novel urea biosensor based on capacitive detection was developed using nano-sized molecularly imprinted polymers (nano-MIP). The sensitive layer was created by casting a thin layer of poly (vinyl chloride) (PVC)/nano-MIP composite on a graphite electrode surface. Cyclic voltammetry and impedance spectroscopy were used to monitor the electrode surface modification. The insulating properties of the layer were studied in the presence of K3Fe(CN)6/K4Fe(CN)6 redox couple by AC impedance measurements. The proposed capacitive sensor exhibited good selectivity for urea, compared to the chemicals with high resemblance to urea. The repeatability of the senor was found to be satisfactory. Very wide dynamic linear range (1×10(-11)-1×10(-4)M) as well as an ultra-trace detection limit equal to 5 picomolar was obtained for the sensor. The relevant experiments indicated satisfactory repeatability and reproducibility for the developed sensor. The results from sample analysis confirmed the applicability of the MIP-based sensor to quantitative analysis of urea in real samples.