Potentiometric Urea Biosensor Research Articles

Development of a Flexible Printed Circuit Board-Based Potentiometric Urea Biosensor Combined With Power Management Circuit Chip

Development of a Flexible Printed Circuit Board-Based Potentiometric Urea Biosensor Combined With Power Management Circuit Chip

The Stability Analysis of Potentiometric Urea Biosensor Under Microfluidic System and Remote Measurement

Stability is one of the most important characteristics of the potentiometric urea biosensors; however, it has rarely been discussed in previous literature. In this article, the stability of the potentiometric urea biosensor based on the urease-Ag NPs/RuO2 sensing film was studied. Using the voltage–time ( $V$ – $T$ ) measurement system, the stability was verified by analyzing the biosensor’s reproducibility, repeatability, long-term measurement, and effect of temperature. Based on the results of this study, the proposed potentiometric urea biosensor had good reproducibility [relative standard deviation (RSD) was 2.23%] and repeatability (RSD was 1.16%). The urease-Ag NPs/RuO2 sensing film still has 90% initial sensitivity after 15 days of storage at room temperature. Moreover, the proposed urea biosensor was integrated into the microfluidic system and the remote measurement system. The sensing characteristics of the potentiometric urea biosensor under different flow rates (1.4–7.0 $\mu \text{L}$ /min, 0–30 $\mu \text{L}$ /min) were studied. In the remote measurement, the average sensitivity was 45.75 mV/decade and the linearity was 0.986.

High stability potentiometric urea biosensor based on enzyme attached nanoparticles

Highly stable new urea biosensor was prepared by using poly(2-hydroxyethyl methacrylate-glycidyl methacrylate) nanoparticles, which was used as a nano-carrier for urease enzyme. The urea biosensor was prepared by an ammonium selective electrode along with the urease immobilized nanoparticles. Synthesized nanoparticles were characterized by SEM and attachment of the enzyme onto the nanoparticles was evaluated by EDX analysis. Potentiometric response of the biosensor was examined as a function of the different concentrations of urea solution, and linear concentration range of urea was demonstrated in the range of 0.01 mM-500 mM. The detection limit was also investigated and measured as 0.77 µM. Response time of the biosensor was also determined as 30 s. Repeatability of the urea biosensor system was found to be very high, and it was demonstrated that response of the urea sensor was protected by 95.7% at the end of the 170th reuse. This biosensor system protected 83% of its initial activity at the end of the 90 day storage. Additionally, interference profile of the urea biosensor was tested against the common interferents such as ascorbic acid (AA), uric acid (UR), glucose (GL) and sodium ions (Na+), and the response of these interfering agents was found to be as negligible. Also, applicability of the synthesized urea sensor for detection of urea from artificial human serum was demonstrated.

Development of urea biosensor using non-covalent complexes of urease with aldehyde derivative of PEG and analysis on serum samples

Non-covalent complexes of urease/polyethylene glycol (PEG)-aldehyde were synthesized using regular molar ratios of urease and PEG-aldehyde at room temperature. The physical properties of the non-covalent complexes were analyzed in order to investigate the impact of coupling ratio, temperature, pH, storage stability, and thermal stability. Urease activity was analyzed by UV–Vis spectrophotometer at 630 nm. The results showed that the strongest thermal resistance was obtained using nU/nPEG:1/1 (mg/mL) complex within all molar ratios tested. The enzymatic activity of nU/nPEG:1/1 complex doubled the activity of the free enzyme. Therefore, this complex was chosen to be used in the analyses. When coupled with PEG-aldehyde, urease exhibited improved activity between pH 4.0–9.0 and the optimum pH was found to be 7.0. The thermal inactivation results of the complex demonstrated that higher activity remained (40%) when compared with the free enzyme (10%) at 60 °C. The storage stability of the non-covalent complex was 4 weeks which was greater than the storage stability of the free enzyme. A kinetic model was suggested in order to reveal the mechanism of enzymatic conversion. Potentiometric urea biosensor was prepared using two different membranes: carboxylated poly vinyl chloride (PVC) and palmitic acid containing PVC. The potentiometric responses of both sensors were tested against pH and temperature and the best results were obtained at pH 7.0 and 20–30 °C. Also, selectivity of the suggested biosensors toward Na+, Li+ Ca2+, and K+ ions was evaluated and the reproducibility responses of the urea biosensors were measured with acceptable results.

Non-Enzymatic Urea Biosensor Based on Silver-Nickel Oxyhydroxide Nanorods Composite Electrode

Urea is an end-product of the metabolism of nitrogenous compounds, which can be detected in the blood as well as urine [1]. Ammonia catabolized by protein metabolism is converted into urea by liver and kidneys [2]. Consequently, the concentration of urea in the urine or blood is a suitable biomarker that monitors liver and kidney function. If a sensor platform can immediately determine the level of urea in the biological fluid, it will be valuable for many patients when estimating the concentration of urea in the blood. Investigation on urea biosensors has been mainly guided out the advancement of enzyme-based catalysts [3]. However, the limitations such as denaturation of enzyme and mobilization to the catalysts lead to the lack of stability. Consequently, the improvement of non-enzyme-based catalysts can work the constraints mentioned above, thereby allowing the progression of urea biosensors. Many non-enzymatic catalysts have been investigated to catch urea molecules, including noble metals, transition metals, and metal hydroxide [4]-[6]. With them, the Ni-based catalysts are the most encouraging suggestion, because it gives excellent electrocatalytic efficiency, biocompatibility, nontoxicity, and high electron transfer. [7]. Although nickel-based catalysts are admitted being an excellent facilitator for the urea electrooxidation, published investigations are few in the nickel-based catalysts for biosensor applications. The inadequacy of research in the biosensor area is related to the mechanism of nickel-based catalysts in alkaline medium. Ni(OH)2 (Ni2+) is electrochemically oxidized to NiOOH (Ni3+) before electrocatalytic urea oxidation. However, since the pH of human blood is neutral (7.35-7.45), it is necessary to develop catalysts as a biomarker for urea electrooxidation which does not depend on pH. Therefore, the nickel-based catalysts intrinsically involving Ni3+ ion will more efficiently improve the electrooxidation performance of the urea. In this study, A composite catalyst based on silver-nickel oxide hydroxide nanorods (Ag-NiOOH) was synthesized for non-enzymatic urea detection. The Ag-NiOOH was characterized by energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques. The morphology and the structure of the Ag-NiOOH were investigated using scanning electron microscopy. The Ag-NiOOH coated carbon paper was employed to fabricate a new electrochemical sensor for urea detection. The Ag-NiOOH/carbon paper electrode showed a very high sensitivity of 177 μAmM−1cm−2, a low detection limit of 5 μM and a response time of 1.5 s. Detailed discussion on the performance of Ag-NiOOH and the role of inherent Ni3+ ions as a catalyst in urea biosensor will be given. References Coll, Elisabeth, et al. "Serum cystatin C as a new marker for noninvasive estimation of glomerular filtration rate and as a marker for early renal impairment." American journal of kidney diseases 36.1 (2000): 29-34.Jakhar, Seema, et al. "Preparation, characterization and application of urease nanoparticles for construction of an improved potentiometric urea biosensor." Biosensors and Bioelectronics 100 (2018): 242-250.Liu, Baohong, et al. "Studies on a potentiometric urea biosensor based on an ammonia electrode and urease, immobilized on a γ-aluminum oxide matrix." Analytica chimica acta 341.2-3 (1997): 161-169.Boggs, Bryan et al. "Urea electrolysis: direct hydrogen production from urine." Chemical Communications 32 (2009): 4859-4861.Chen, Sheng, et al. "Size Fractionation of Two‐Dimensional Sub‐Nanometer Thin Manganese Dioxide Crystals towards Superior Urea Electrocatalytic Conversion." Angewandte Chemie International Edition 55.11 (2016): 3804-3808.Wu, Mao-Sung, et al. "Hydrothermal growth of vertically-aligned ordered mesoporous nickel oxide nanosheets on three-dimensional nickel framework for electrocatalytic oxidation of urea in alkaline medium." Journal of power sources 272 (2014): 711-718.Li, Chengchao, et al. "A novel amperometric biosensor based on NiO hollow nanospheres for biosensing glucose." Talanta 77.1 (2008): 455-459. Acknowledgement This work was supported by Agency for Defense Development (ADD) as global cooperative research for high performance and light weight bio-urine based fuel cell (UD160050BD) and the Ocean University of China-Auburn University (OUC-AU) Grants program.

RETRACTED ARTICLE: Effect of Urea on the Morphology of Fe3O4 Magnetic Nanoparticles and Their Application in Potentiometric Urea Biosensors

The effect of different concentrations of urea on the morphology of iron oxide (Fe3O4) magnetic nanoparticles was studied. Fe3O4 magnetic nanoparticles were fabricated by the coprecipitation method. The morphology, crystallinity, compositional purity, and emission characteristics were tested by the techniques of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Raman characterization. The drop-casting technique was successfully used to fabricate a potentiometric urea biosensor producing initially isopropanol and chitosan solution, consisting of Fe3O4 nanoparticles, on a glass fiber filter. To measure the developed biosensor’s voltage signal from the functionalized nanoparticles, a copper wire was utilized. The Fe3O4 nanoparticle surface functionalization was performed through the electrostatic immobilization of urease with the Fe3O4-chitosan (CH) nanobiocomposite. The presented urea biosensor measured a wide logarithmic range of urea concentration of 0.1–80 mM with a sensitivity of 42 mV/decade, and indicated a fast response time of approximately 12 s. The developed urea biosensor showed enhanced sensitivity, stability, reusability, and specificity. All experimental results demonstrate the application potential of the developed urea sensor for the monitoring of urea concentrations in human serum, drugs, and food industry-related samples.

Preparation, characterization and application of urease nanoparticles for construction of an improved potentiometric urea biosensor

The nanoparticles (NPs) aggregates of commercial urease from jack beans (Canavalia ensiformis) were prepared by desolvation and glutaraldehyde crosslinking and functionalized by cysteamine dihydrochloride. These enzyme nanoparticles (ENPs) were characterized by transmission electron microscopy (TEM), UV and Fourier transform infrared (FTIR) spectroscopy. The TEM images of urease NPs showed their size in the range, 18–100nm with an average of 51.2nm. The ENPs were more active and stable with a longer shelf life than native enzyme molecules. The ENPs were immobilized onto chitosan (CHIT) activated nitrocellulose (NC) membrane via glutaraldehyde coupling with 32.22% retention of initial activity of free ureaseNPs with a conjugation yield of 1.63mg/cm2. This NC membrane was mounted at the lower/sensitive end of the ammonium ion selective electrode (AISE) with O-ring and then electrode was connected to a digital pH meter to construct a potentiometric urea biosensor. The biosensor exhibited optimum response within 10s at pH 5.5and 40°C. The biosensor was employed for measurement of potentiometric determination of urea in sera of apparently healthy and persons suffering from kidney disorders. The biosensor displayed a low detection limit of 1µM/L with a wide working range of 2–80µM/L (0.002–0.08mM) and sensitivity of 23mV/decade. The analytical recovery of added urea in serum was 106.33%. The within and between-batch coefficient of variations (CVs) of present biosensor were 0.18% and 0.32% respectively. There was a good correlation (r = 0.99) between sera urea values obtained by reference method (Enzymic colorimetric kit method) and the present biosensor. The biosensor had negligible interference from Na+,K+,NH+4 and Ca2+ but Mg2+,Cu2+ and ascorbic acid but had slight interference, which was overcome by specific ion selective electrode. The ENPs bound NC membrane was used maximally 8–9 times per day over a period of 180 days, when stored in 0.01M sodium acetate buffer pH 5.5 at 4°C.

Non-Invasive Potentiometric Sensor for Measurement of Blood Urea in Human Subjects Using Reverse Iontophoresis

A Screen printed potentiometric urea biosensor is developed to monitor the blood urea level non-invasively using reverse iontophoresis (RI). The working electrode is screen printed using graphitic carbon paste, reference and RI electrodes are screen printed using silver/silver chloride (Ag/AgCl) paste. Urease enzyme is immobilized in the polypyrrole (PPy) matrix of the working electrode using optimized cyclic voltammetry parameters to obtain maximum sensor performance. Electrochemical and material characterizations conducted in the Screen Printed Reference Electrodes (SPRE) are examined to ensure their stability and retention of their properties. The developed screen printed sensors exhibited sensitivity of 35.07 mV/decade and showed liner response for the range, 10 μM to 5 mM with a correlation co-efficient of 0.995. Interference studies with KCl, NaCl and MgCl2 solutions are performed and it was found that sensor performance is unaffected due to interference ions. The urea sensor is further validated by conducting clinical investigations on 15 human subjects. A correlation is established between blood urea level and transdermal extracted urea level and the correlation co-efficient is found to be 0.391.

Potentiometric Urea Biosensor Based on a Urease‐Immobilized Polypyrrole

SummaryUrea is one of the metabolic products of protein metabolism. The accurate determination of urea is important in glomerular filtration rate determination, renal function testing, and other biomedical applications. This research presents a simple fabrication of potentiometric urea biosensor based on a urease‐immobilized polypyrrole (PPy). Thin film of PPy doped with hydroquinone monosulfonate (HQS) was electropolymerized on stainless steel supporting electrode. Urease was immobilized onto the PPy film by mean of physical adsorption. X‐ray photoelectron spectroscopy (XPS) was performed to confirm the existence of urease on PPy surface. The PPy film immobilized with urease activity of 200 U/mL showed the sensitivity of 43.4 ± 3.3 mV/pUrea (r2 > 0.99) in the urea concentration ranging from 0.5 to 10 mM (pUrea 2.0–3.3). The response time was less than 60 sec. The urease‐immobilized PPy film offers a great potential in the use of conducting PPy film as an effective transducer to convert physiochemical change into an electronic signal, enhancing in performance of the biosensor.

Screen Printed Potentiometric Sensor for Non-Invasive Measurement of Blood Urea in Human Subjects Using Reverse Iontophoresis

A screen printed potentiometric urea biosensor is developed to monitor blood urea level non-invasively using reverse iontophoresis. The extraction and sensing system consists of a reverse iontophoresis electrodes, a working electrode and a reference electrode. The working electrode is screen printed using graphitic carbon paste, reference and reverse iontophoresis electrodes are screen printed using silver/silver chloride (Ag/AgCl) paste. Urease enzyme is immobilized in the polypyrrole matrix on the working electrode using cyclic voltammetry. The electrochemical characterization and material characterization is conducted on screen printed electrode. The sensing range, sensitivity and eliminating interfering species shows that developed sensor has potential application in reverse ionophoresis (RI) sensing method. Developed urea sensor is validated by conducting clinical investigations on 10 human subjects. The correlation co-efficient is arrived between blood urea level and transdermal extracted urea level and it is found to be 0.391.

Non-Invasive Biosensor for Measurement of Blood Urea Level in Human Subjects Using Reverse Iontophoresis

A screen printed potentiometric urea biosensor is developed to monitor blood urea level non-invasively using reverse iontophoresis. The extraction and sensing system consists of a reverse iontophoresis electrode, a working electrode and a reference electrode. The working electrode is screen printed using graphitic carbon paste, reference and reverse iontophoresis electrodes are screen printed using silver/silver chloride (Ag/AgCl) paste. Urease enzyme is immobilized in the polypyrrole matrix on the working electrode using cyclic voltammetry, having potential window of -0.1 v to 0.8 v and scan rate of 50 mV/s for 5 deposition cycles. Scan rate and deposition cycles are optimized for cyclic voltammetry to immobilize the urease enzyme in polypyrrole matrix to obtain maximum sensor performance. The stability of screen printed reference electrode (SPRE) is probed with standard calomel electrode and found to be stable for more than 60 minutes. The enzyme leaching test on working electrode is conducted using indophenol method and confirms that there is no leaching of enzyme from the electrodes. Scanning Electron Micrograph (SEM) of deposited polyrrole shows that microstructured film is deposited on the working electrode. X-ray diffraction (XRD) and Raman spectroscopy are performed to analyze composition of deposited film and they confirm the presence of all mandatory functional groups of polypyrrole in the deposited film. Electrochemical active area is calculated through cyclic voltammetry and there is 55- 60% increase in electrochemical active area compared to bare graphitic carbon electrode due to the formation of polypyrrole microstructure on the working electrode. The developed screen printed sensors exhibited sensitivity of 35.07 mv/decade and showed liner response for the range, 10 μM to 5 mM with correlation co-efficient of 0.995. Interference studies with KCl, NaCl and MgCl solutions are performed and found that there are no significant changes in the sensor performance. These tests affirmed that the developed sensors are useful for conducting in-vivo studies to measure blood urea level non-invasively through reverse iontophoresis. Developed urea sensor is validated by conducting clinical investigations on 10 human subjects. The correlation co-efficient is arrived between blood urea level and transdermal extracted urea level and it is found to be 0.391. Figure 1

Cobalt oxide magnetic nanoparticles–chitosan nanocomposite based electrochemical urea biosensor

In this study, a potentiometric urea biosensor has been fabricated on glass filter paper through the immobilization of urease enzyme onto chitosan/cobalt oxide (CS/Co3O4) nanocomposite. A copper wire with diameter of 500 µm is attached with nanoparticles to extract the voltage output signal. The shape and dimensions of Co3O4 magnetic nanoparticles are investigated by scanning electron microscopy and the average diameter is approximately 80–100 nm. Structural quality of Co3O4 nanoparticles is confirmed from X-ray powder diffraction measurements, while the Raman spectroscopy has been used to understand the chemical bonding between different atoms. The magnetic measurement has confirmed that Co3O4 nanoparticles show ferromagnetic behavior, which could be attributed to the uncompensated surface spins and/or finite size effects. The ferromagnetic order of Co3O4 nanoparticles is raised with increasing the decomposition temperature. A physical adsorption method is adopted to immobilize the surface of CS/Co3O4 nanocomposite. Potentiometric sensitivity curve has been measured over the concentration range between 1 × 10−4 and 8 × 10−2 M of urea electrolyte solution revealing that the fabricated biosensor holds good sensing ability with a linear slope curve of ~45 mV/decade. In addition, the presented biosensor shows good reusability, selectivity, reproducibility and resistance against interferers along with the stable output response of ~12 s.

Potentiometric Urea Biosensor Based on an Immobilised Fullerene-Urease Bio-Conjugate

A novel method for the rapid modification of fullerene for subsequent enzyme attachment to create a potentiometric biosensor is presented. Urease was immobilized onto the modified fullerene nanomaterial. The modified fullerene-immobilized urease (C60-urease) bioconjugate has been confirmed to catalyze the hydrolysis of urea in solution. The biomaterial was then deposited on a screen-printed electrode containing a non-plasticized poly(n-butyl acrylate) (PnBA) membrane entrapped with a hydrogen ionophore. This pH-selective membrane is intended to function as a potentiometric urea biosensor with the deposition of C60-urease on the PnBA membrane. Various parameters for fullerene modification and urease immobilization were investigated. The optimal pH and concentration of the phosphate buffer for the urea biosensor were 7.0 and 0.5 mM, respectively. The linear response range of the biosensor was from 2.31 × 10−3 M to 8.28 × 10−5 M. The biosensor's sensitivity was 59.67 ± 0.91 mV/decade, which is close to the theoretical value. Common cations such as Na+, K+, Ca2+, Mg2+ and NH4+ showed no obvious interference with the urea biosensor's response. The use of a fullerene-urease bio-conjugate and an acrylic membrane with good adhesion prevented the leaching of urease enzyme and thus increased the stability of the urea biosensor for up to 140 days.

Analysis of Potential Applicability of the Potentiometric Urea Biosensor to Real Samples

Since the production and use of chemical products are performing a marked growth, the charge, for fast and efficient mechanisms of environmental pollution control and monitoring, has increased. This charge has been made even more present in the rural scenario, especially with regard to fertilizers and nitrogen compounds, which have a high pollution potential. Several methods are used to urea determination, but usually they require a pretreatment or they are unsuitable for monitoring in situ. For this reason, urea biosensor can be a fast and cost-effective analytical technique to be used in extensive monitoring programs. Urea enzyme sensors based on potentiometric detection of ammonium ion, ammonia gas and carbon dioxide have been reported. In this study, the potential applicability of the potentiometric urea biosensor to real samples has been studied. The biocomponent used was jack beans, Canavalia ensiformis, a vegetal tissue rich in urease. The vegetal tissue was immobilized on nylon net by glutaraldehyde in order to improve the enzyme stability and the lifetime of the urea biosensor. Moreover, an ammonium ion-selective electrode was been chosen as the transducer. The instrument was applied to commercial urea fertilizer solutions and an environmental sample, the sugar-cane vinasse. The linear concentration range calibration curve was 1–20 ppm urea with a response time of 15 min. Urea biosensor could be reused for 70 days and the response was more than 95 % reproducible. Moreover, the urea biosensor was tested in real samples with qualitative promising responses.

Potentiometric urea biosensor utilizing nanobiocomposite of chitosan-iron oxide magnetic nanoparticles

The iron oxide (Fe3O4) magnetic nanoparticles have been fabricated through a simple, cheap and reproducible approach. Scanning electron microscope, x-rays powder diffraction of the fabricated nanoparticles. Furthermore, the fabrication of potentiometric urea biosensor is carried out through drop casting the initially prepared isopropanol and chitosan solution, containing Fe3O4 nanoparticles, on the glass fiber filter with a diameter of 2 cm and a copper wire (of thickness −500 μm) has been utilized to extract the voltage signal from the functionalized nanoparticles. The functionalization of surface of the Fe3O4 nanoparticles is obtained by the electrostatically immobilization of urease onto the nanobiocomposite of the chitosan- Fe3O4 in order to enhance the sensitivity, specificity, stability and reusability of urea biosensor. Electrochemical detection procedure has been adopted to measure the potentiometric response over the wide logarithmic concentration range of the 0.1 mM to 80 mM. The Fe3O4 nanoparticles based urea biosensor depicts good sensitivity with ~42 mV per decade at room temperature. Durability of the biosensor could be considerably enhanced by applying a thin layer of the nafion. In addition, the reasonably stable output response of the biosensor has been found to be around 12 sec.

Immobilization of the urease on eggshell membrane and its application in biosensor

Eggshell membrane is a natural material, essentially made up of protein fibers having flexibility in the aqueous solution and possessing gas and water permeability. It is used as a biomembrane for immobilization of urease for the development of a potentiometric urea biosensor. Eggshell membrane was treated with polyethyleneimine (PEI) to impart polycation characteristics. Urease was immobilized on the PEI treated eggshell membrane through adsorption. SEM study was carried out to observe the changes in surface morphology after immobilization. FTIR study of membrane was carried out to observe the changes in IR spectra after immobilization of enzyme. Immobilized membrane was associated with ammonium ion selective electrode. Biosensor exhibited sigmoidal responses for the urea concentration range from 0.5 to 10mM. The response time of the biosensor was 120s. A single membrane was reused for 270 reactions without loss of activity. The urease–eggshell membranes were stable for 2months when stored in buffer even at room temperature.

Potentiometric urea biosensor based on poly(glycidylmethacrylate)-grafted iron oxide nanoparticles

Urease enzyme was covalently attached on the poly(glycidylmethacrylate) (PGMA)-grafted iron oxide nanoparticles on Au electrode for the fabrication of urea biosensor. The telomere of poly(glycidylmethacrylate) (PGMA) with a trimethoxysilyl terminal group was synthesized by telomerization of glycidylmethacrylate. Iron oxide nanoparticles were coated with telomere of poly(glycidylmethacrylate) in order to obtain good enzyme immobilization platform. The telomere and nanoparticles were characterized by using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA). The biosensor’s potentiometric response was measured as a function of urea concentration in phosphate buffer solution (10 mM, pH 7.5) and showed a linear range of 0.25–5.0 mM urea. The produced biosensor exhibited a good response time of ∼8 s and was stable for about two months. The basic features (optimum pH, optimum temperature, interference and storage stability) of the enzyme electrode were determined.

Structural Characterization of Graphene Nanosheets for Miniaturization of Potentiometric Urea Lipid Film Based Biosensors

AbstractThe present article describes a miniaturized potentiometric urea lipid film based biosensor on graphene nanosheets. Structural characterization of graphene nanosheets for miniaturization of potentiometric urea lipid film based biosensors have been studied through atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. UV‐Vis and Fourrier transform IR (FTIR) spectroscopy have been utilized to study the pre‐ and postconjugated surfaces of graphene nanosheets. The presented potentiometric urea biosensor exhibits good reproducibility, reusability, selectivity, rapid response times (∼4 s), long shelf life and high sensitivity of ca. 70 mV/decade over the urea logarithmic concentration range from 1×10−6 M to 1×10−3 M.

Potentiometric urea biosensor based on urease immobilized by an electrosynthesized poly( o-phenylenediamine) film with buffering capability

A simple and novel potentiometric biosensor for urea detection was prepared by employing an electrosynthesized polymer with buffering capability. It was obtained by deposition of a weighed amount of urease (Ur) at a glassy carbon (GC) electrode followed by immobilization by an electrosynthesized poly- o-phenylenediamine (PPD) film. An unconventional “upside-down” (UD) geometry was employed for the electrochemical cell. The response of GC/Ur/PPD sensor is linear with urea concentration in the range 10 μM to 1 mM (15 mV/mM, R 2 = 0.9999) due to buffering capability of PPD film, which represents a novel role of electrosynthesized polymers in their application to biosensors. At higher concentrations, the more common Nernstian response (28 mV/decade, R 2 = 0.9987) is observed. The sensor exhibits a sufficient sensitivity for practical determinations, rapid response and long term stability.

Development of Potentiometric Urea Biosensor For Clinical Purposes

This review summarizes the studies carried on the development of potentiometric urea biosensor in laboratory using urease from Cajanus cajan (local Arhar). The enzyme used was free without any immobilisation over matrix. The electrode used egg membrane or cellophane paper making ionic diffusion possible across the two solutions. Underlying the importance of this study is the fact that urea is toxic above certain concentrations in different biological samples and its continuous real time monitoring in clinical environments is of utmost importance. The conventional analytical techniques used, although precise is time- consuming and laboratory bound whereas biosensors have the advantages of ease of use, portability and the ability to furnish real time signals. © 2011 IGJPS. All rights reserved.