A Urea Biosensor from Stacked Sol-Gel Films with Immobilized Nile Blue Chromoionophore and Urease Enzyme

Abstract

An optical urea biosensor was fabricated by stacking several layers of sol-gel films. The stacking of the sol-gel films allowed the immobilization of a Nile Blue chromoionophore (ETH 5294) and urease enzyme separately without the need of any chemical attachment procedure. The absorbance response of the biosensor was monitored at 550 nm, i.e. the deprotonation of the chromoionophore. This multi-layer sol-gel film format enabled higher enzyme loading in the biosensor to be achieved. The urea optical biosensor constructed from three layers of sol-gel films that contained urease demonstrated a much wider linear response range of up to 100 mM urea when compared with biosensors that constructed from 1-2 layers of films. Analysis of urea in urine samples with this optical urea biosensor yielded results similar to that determined by a spectrophotometric method using the reagent p-dimethylaminobenzaldehyde (R 2 = 0.982, n = 6). The average recovery of urea from urine samples using this urea biosensor is approximately 103%.

Application of Electrochemical Biosensors in Clinical Diagnosis

“…The deprotonation of the chromoionophore was monitored as the absorbance response of the biosensor at 550 nm. Results were in good agreement with those obtained by a spectrophotometric method using the reagent p‐ dimethylaminobenzaldehyde . Vostiar et al.…”

New Urea Biosensor Based on Urease Enzyme Obtained from Helycobacter pylori

“…Where Cs is the concentration of urea determined by the each biosensor and C is the actual concentration of urea added [30].…”

Nile Blue chromoionophore-doped kappa-carrageenan for a novel reflectometric urea biosensor

“…Urea detection in urine as a real sample can be determined after being tested by UV-vis as a standard method with monitoring at 420 nm via 4- Mix 2 mL of working solution into cuvette and 2 mL DMAB solution to each and let it react for 10 min at room temperature. By choosing the DMAB method, we obtain a simpler, quicker and more accurate measurement for detection the content of urea in the urine sample [18,21]. A urine sample was collected from a healthy volunteer and diluted 10-fold with 0.05 M PBS (pH 7.0).…”

“…A number of reagent dyes have been reported for purposes such as the indirect measurement of urea, among others, the Nessler reagent [17], p-dimethylaminobenzaldehyde (DMAB) [18], diacetylmonoxime [19] and phenolphthalein [20]. The immobilized NB chromoionophore in acrylic microspheres and sol-gel films have been previously used as reagent phases for the development of optical urea biosensors via reflectometry and UV-vis spectrophotometry methods, respectively [14,21]. However, the linear detection range and the lower detection limit of urea were not conformed to the physiological range of urea in human fluids.…”