Study of zeolite influence on analytical characteristics of urea biosensor based on ion-selective field-effect transistors

A possibility of the creation of potentiometric biosensor by adsorption of enzyme urease on zeolite was investigated. Several variants of zeolites (nano beta, calcinated nano beta, silicalite, and nano L) were chosen for experiments. The surface of pH-sensitive field-effect transistors was modified with particles of zeolites, and then the enzyme was adsorbed. As a control, we used the method of enzyme immobilization in glutaraldehyde vapour (without zeolites). It was shown that all used zeolites can serve as adsorbents (with different effectiveness). The biosensors obtained by urease adsorption on zeolites were characterized by good analytical parameters (signal reproducibility, linear range, detection limit and the minimal drift factor of a baseline). In this work, it was shown that modification of the surface of pH-sensitive field-effect transistors with zeolites can improve some characteristics of biosensors

Bina İçi Yönlendirme Sistemlerinde Kullanılan En Kısa Yol Algoritmalarının Afet ve Acil Durum Yönetimi Açısından Değerlendirilmesi

Mimari açıdan karmaşık ve içinde fazla sayıda insanın bulunacağı şekilde tasarlanan ofis veya eğitim binaları gibi yapılarda, herhangi bir doğal afette ve/veya acil durumda büyük ölçekte can kayıpları ve yaralanmalar yaşanabilmektedir. Ayrıca, bir afet/acil durum sonrasında değişen bina koşulları ardışık afetleri ve/veya tehlikeleri (örneğin deprem sonrası çıkan yangınlar) tetikleyebilmektedir. Etkin bir bina içi yönlendirme sistemi, afetlerde/acil durumlarda yaşanan problemleri en aza indirgeyerek can kayıplarını azaltmada kritik bir öneme sahiptir. Bina içi yönlendirmede amaç, bina içersinde bulunan kişilerin, afetlerden/acil durumlardan ve tetiklenebilecek ardışık tehlikelerden en az etkilenecek şekilde en kısa yoldan güvenli bölgelere yönlendirilmeleridir. Bu amaçla bina içi yönlendirme sistemlerinde en kısa yol (EKY) algoritmaları kullanılmaktadır. Literatürde, araştırmacıların yönlendirme sistemlerini oluştururken hangi EKY algoritmasını tercih etmeleri gerektiği yönünde bir boşluk bulunmaktadır. Bu çalışma bulgularının, bina içi yönlendirme sistemi geliştirme çalışmalarında en uygun algoritmanın seçimine kılavuzluk etmesi hedeflenmektedir. Literatürdeki bina içi yönlendirme çalışmaları araştırılarak en sık kullanılan EKY algoritmalarının afet sonrası oluşan yeni yapı koşullarında kısa yol belirlemedeki performansları incelenmiştir. Yönlendirme sistemlerinde kullanılacak olan EKY algoritmalarının sağlamaları gereken özellikler belirlenen altı adet ölçüt ışığında afet/acil durum yönetimi bakış açısıyla kıyaslaması yapılmıştır. Ayrıca, afetlerde/acil durumlarda kullanılabilecek bina içi yönlendirme sistemlerinden beklenenleri en uygun şekilde sağlayan EKY algoritması üzerine tartışma ve öneriler sunulmuştur

Elaboration of Urease Adsorption on Silicalite for Biosensor Creation

A possibility of efficient urease adsorption on silicalite for the purpose of biosensor creation was investigated. The procedure of urease adsorption on silicalite is notable for such advantages as simple and fast performance and non-use of toxic or auxiliary compounds. Optimal conditions for modifying transducer surfaces with silicalite and subsequent urease adsorption on these surfaces were selected. The working parameters of the created biosensor were optimized. The developed biosensor with adsorbed urease was characterized by good intra-reproducibility (RSD 4.5?%), improved inter-reproducibility (RSD of urea determination is 9?%) and operational stability (less than 10?% loss of activity after 10 days). Besides, the developed method for enzyme adsorption on silicalite was compared with the traditional methods of urease immobilization in biosensorics. Working conditions of the produced biosensor (pH and ionic strength) were shown to be close to those of the biosensor based on urease immobilized in GA vapor. For these reasons, it was concluded that the method of enzyme adsorption on silicalite is well-suited for biosensor standardization aimed at its further manufacture

Biosensors Based on Nano-Gold/Zeolite-Modified Ion Selective Field-Effect Transistors for Creatinine Detection

The combination of advantages of using zeolites and gold nanoparticles were aimed to be used for the first time to improve the characteristic properties of ion selective field-effect transistor (ISFET)-based creatinine biosensors. The biosensors with covalently cross-linked creatinine deiminase using glutaraldehyde (GA) were used as a control group, and the effect of different types of zeolites on biosensor responses was investigated in detail by using silicalite, zeolite beta (BEA), nano-sized zeolite beta (Nano BEA) and zeolite BEA including gold nanoparticle (BEA-Gold). The presence of gold nanoparticles was investigated by ICP, STEM-EDX and XPS analysis. The chosen zeolite types allowed investigating the effect of aluminium in the zeolite framework, particle size and the presence of gold nanoparticles in the zeolitic framework

Influence of Composition of Zeolite/Enzyme Nanobiocomposites on Analytical Characteristics of Urea Biosensor Based on Ion-Selective Field-Effect Transistors

Zeolite/enzyme nanobiocomposites of different compositions were tested in this work for the improvement of biosensor analytical characteristics. The bioselective element based on urease immobilized by cross-linking with glutaraldehyde was used as a model. The working characteristics of biosensors based on various zeolite/enzyme nanocomposites were examined and compared with those of urease-based biosensors. An optimal concentration of zeolytes beta (BEA) in bioselective elements is determined to be 1.5%. It ensures as wide linear range of measurement without remarkable loss in biosensor sensitivity to urea. The BEA zeolite-based biosensors were shown to have better working parameters in comparison with those based on zeolites A (LTA). A decrease in biosensor sensitivity to heavy metal ions was demonstrated for all zeolites used, which testifies to probable increase in stability of urea measurement in real environmental samples

Conductometric enzyme biosensors based on natural zeolite clinoptilolite for urea determination

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

Application of enzyme/zeolite sensor for urea analysis in serum

Urea biosensor based on zeolite-adsorbed urease was applied for analysis of blood serum samples. It should be noted, that this biosensor has a number of advantages, such as simple and fast performance, the absence of toxic compounds during biosensor preparation, high reproducibility and repeatability (RSD = 9% and 4%, respectively). The linear range of urea determination by using the biosensor was 0.003-0.75 mM, and the limit of urea detection was 3 mu M. The method of standard addition was used for analysis of serum samples with 500-fold dilution. Total time of analysis was 10 min. Good reproducibility of urea determination in real samples was demonstrated (RSD = 10%). Biosensor results were verified by using a common method of urea determination (diacetyl monoxime reaction). It was shown that by using this biosensor distinguishing healthy people from people with renal dysfunction becomes easier

Direct evidence of advantage of using nanosized zeolite Beta for ISFET-based biosensor construction

Analytical characteristics of urease- and butyrylcholinesterase (BuChE)-based ion sensitive field-effect transistor (ISFET) biosensors were investigated by the incorporation of zeolite Beta nanoparticles with varying Si/Al ratios. The results obtained by the zeolite-modified ISFET transducers suggested that the Si/Al ratio strongly influenced the biosensor performances due to the electrostatic interactions among enzyme, substrate, and zeolite surface as well as the nature of the enzymatic reaction. Using relatively small nanoparticles (62.7 +/- 10, 76.2 +/- 10, and 77.1 +/- 10 nm) rather than larger particles, that are widely used in the literature, allow us to produce more homogenous products which will give more control over the quantity of materials used on the electrode surface and ability to change solely Si/Al ratio without changing other parameters such as particle size, pore volume, and surface area. This should enable the investigation of the individual effect of changing acidic and electronic nature of this material on the biosensor characteristics. According to our results, high biosensor sensitivity is evident on nanosize and submicron size particles, with the former resulting in higher performance. The sensitivity of biosensors modified by zeolite particles is higher than that to the protein for both types of biosensors. Most significantly, our results show that the performance of constructed ISFET-type biosensors strongly depends on Si/Al ratio of employed zeolite Beta nanoparticles as well as the type of enzymatic reaction employed. All fabricated biosensors demonstrated high signal reproducibility and stability for both BuChE and urease

Application of silicalite-modified electrode for the development of sucrose biosensor with improved characteristics

The application of silicalite for improvement of working characteristics of conductometric enzyme biosensors for determination of sucrose was studied in this research. Biosensors based on different types of silicalite-modified electrodes were studied and compared according to their analytical characteristics. Polyethylenimine/glutaraldehyde/silicalite-modified biosensors showed higher sensitivity compared with others type of biosensors. Moreover, the polyethylenimine/glutaraldehyde/silicalite sucrose biosensors were characterized by high selectivity and signal reproducibility (relative standard deviation (RSD) = 2.78% for glucose measurements and RSD = 3.2% for sucrose measurements). Proposed biosensors were used for determination of sucrose in different samples of beverages. The obtained results had good correlation with results obtained by HPLC. Thus, polyethylenimine/glutaraldehyde/ silicalite-modified biosensors have shown perspective characteristics for the development of effective conductometric enzyme biosensors