In this work, we developed a new amperometric biosensor for glutamate detection using a typical method of glutamate oxidase (GlOx) immobilization via adsorption on silicalite particles. The disc ...platinum electrode (
d
= 0.4 mm) was used as the amperometric sensor. The procedure of biosensor preparation was optimized. The main parameters of modifying amperometric transducers with a silicalite layer were determined along with the procedure of GlOx adsorption on this layer. The biosensors based on GlOx adsorbed on silicalite demonstrated high sensitivity to glutamate. The linear range of detection was from 2.5 to 450 μM, and the limit of glutamate detection was 1 μM. It was shown that the proposed biosensors were characterized by good response reproducibility during hours of continuous work and operational stability for several days. The developed biosensors could be applied for determination of glutamate in real samples.
In the work, different types of zeolites were used for the development of enzyme-based electrochemical biosensors. Zeolites were added to the biorecognition elements of the biosensors and served as ...additional components of the biomembranes or adsorbents for enzymes. Three types of biosensors (conductometric, amperometric and potentiometric) were studied. The developed biosensors were compared with the similar biosensors without zeolites. The biosensors contained the following enzymes: urease, glucose oxidase, glutamate oxidase, and acetylcholinesterase and were intended for the detection of urea, glucose, glutamate, and acetylcholine, respectively. Construction of the biosensors using the adsorption of enzymes on zeolites has several advantages: simplicity, good reproducibility, quickness, absence of toxic compounds. These benefits are particularly important for the standardization and further mass production of the biosensors. Furthermore, a biosensor for the sucrose determination contained a three-enzyme system (invertase/mutatorase/glucose oxidase), immobilized by a combination of adsorption on silicalite and cross-linking via glutaraldehyde; such combined immobilization demonstrated better results as compared with adsorption or cross-linking separately. The analysis of urea and sucrose concentrations in the real samples was carried out. The results, obtained with biosensors, had high correlation with the results of traditional analytical methods, thus the developed biosensors are promising for practical applications.
Highly sensitive conductometric urea biosensors were developed by exploiting the successful combination of ammonium-sieving and ion exchange properties of clinoptilolite, with a unique biorecognition ...capacity of urease. To optimize the performance of urea biosensors based on clinoptilolite, the dependences of their analytical signals on pH, buffer capacity and ionic strength of phosphate buffer solution (PBS) were studied. Optimum pH for urea biosensors was found within the range of pH 6.0–7.0. The dependences of biosensors responses on buffer capacity and ionic strength of PBS were of the same profile as those obtained for the urea biosensor which was not modified with clinoptilolite.
Analytical characteristics of urea biosensors based on clinoptilolite were evaluated by determination of the sensitivity, linear and dynamic ranges, detection limit, the apparent Michaelis–Menten constant and the response time. The optimum features in terms of sensitivity, dynamic range, and detection limit (20.36
μS/mM, 0–64
mM, and 10
−6
M, respectively) were found for the urea biosensor, based on a primary layer of clinoptilolite followed by a secondary layer of urease and clinoptilolite in a single bioselective membrane. The apparent Michaelis–Menten constants
K
m
for the developed urea biosensors based on clinoptilolite varied from 2.73 to 5.67
mM. These values differed significantly from the value of
K
m
for the urea biosensor which was not modified with zeolite (1.89
mM). All types of zeolite-modified biosensors showed high operational and storage stability.
► Combination of zeolite ammonium-sieving property together with biorecognition provided by urease increases the sensitivity of urea detection. ► Urea biosensor based on a layer of clinoptilolite shows the optimum analytical characteristics. ► Zeolite-based biosensor presents 87% of its initial activity after 5 months.
Aim. Optimization of a new method of enzyme immobilization for amperometric biosensor creation. Methods. The amperometric biosensor with glucose oxidase immobilized on zeolites as bioselective ...elements and platinum disk electrode as transducers of biochemical signal into the electric one was used in the work. Results. The biosensors based on glucose oxidase adsorbed on zeolites were characterized by a higher sensitivity to glucose and a better inter-reproducibility. The best analytical characteristics were obtained for the biosensors based on nano beta zeolite. It has been found that an increase in the amount of zeolite on the surface of amperometric transducer may change such biosensor parameters as sensitivity to the substrate and duration of the analysis. Conclusions. The proposed method of enzyme immobilization by adsorption on zeolites is shown to be quite promising in the development of amperometric biosensors and therefore should be further investigated.
Aim. Improvement of analytical characteristics of an enzyme biosensor based on new inexpensive perspective stainless steel electrodes using silicalite nanoparticles. Methods. Conductometric enzyme ...biosensor was used. Results. Three methods of glucose oxidase (GOx) immobilization were studied and compared: GOx adsorption on silicalite modified electrodes (GOx-SME); cross-linking by glutaraldehyde without silicalite (GOx-GA); GOx adsorption on SME along with cross-linking by glutaraldehyde (GOx-SME-GA). The GOx-SME-GA biosensors based on stainless steel electrodes were characterized by 12–25-fold higher sensitivity comparing with other biosensors. The developed GOx-SME-GA biosensors were characterized by good reproducibility of glucose biosensors construction (relative standard deviation (RSD) – 18 %), improved signal reproducibility (RSD of glucose determination was 7 %) and good storage stability (29 % loss of activity after 18 days). Conclusions. The method of enzyme immobilization using silicalite together with GA cross-linking sufficiently enhances the enzyme adsorption on the stainless steel electrodes and improves the analytical parameters of biosensors. This method is found to be promising for further creation of other enzyme biosensors.
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