A Novel Conductometric Urea Biosensor with Improved Analytical Characteristic Based on Recombinant Urease Adsorbed on Nanoparticle of Silicalite

Development of a conductometric biosensor for the urea detection has been reported. It was created using a non-typical method of the recombinant urease immobilization via adsorption on nanoporous particles of silicalite. 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, and high reproducibility (RSD = 5.1 %). The linear range of urea determination by using the biosensor was 0.05–15 mM, and a lower limit of urea detection was 20 μM. The bioselective element was found to be stable for 19 days. The characteristics of recombinant urease-based biomembranes, such as dependence of responses on the protein and ion concentrations, were investigated. It is shown that the developed biosensor can be successfully used for the urea analysis during renal dialysis

Development of a New Biosensor by Adsorption of Creatinine Deiminase on Monolayers of Micro- and Nanoscale Zeolites

This work is dedicated to the development of creatinine-sensitive biosensor consisting of pH-sensitive field-effect transistor (pH-FET) and creatinine deiminase (CD) immobilized with various types of zeolites, in particular, silicalite, zeolite beta (BEA) and nanobeta, and BEA zeolites, modified with gold nanoparticles and ions. For comparison, the traditional method of CD immobilization in saturated glutaraldehyde (GA) vapor was used. To modify pH-FET with zeolites, a monolayer method of deposition was applied. All basic analytical characteristics of the developed biosensors were compared: linear range of creatinine determination, time of response and regeneration, minimum limit of detection, and response reproducibility within a single biosensor; the calibration curves were plotted. It is shown that the use of zeolites of different types as adsorbents in the development of creatinine-sensitive biosensors resulted in a decrease of time of response and regeneration, an increase in sensitivity of the bioselective element to creatinine, and improvement in reproducibility of preparation of various biosensors, as compared with the method of covalent cross-linking in GA vapor

Hybrid sol–gel coatings for corrosion protection of galvanized steel in simulated concrete pore solution

The aim of this experimental research was to study the electrochemical behavior of organic– inorganic hybrid (OIH) coatings for corrosion protection of hot-dip galvanized steel (HDGS) in the first instants of immersion in simulated concrete pore solution (SCPS) (pH > 12.5). The electrochemical performance of the OIH coatings was assessed by electrochemical impedance spectroscopy, potentiodynamic polarization curves, macrocell current density, and polarization resistance. The OIH coatings were prepared via the sol–gel method and were deposited on HDGS surfaces by dip-coating using one or three dip steps. The electrochemical results obtained for HDGS samples coated with OIH matrices in SCPS showed higher corrosion resistance than bare HDGS; as the molecular weight (MW) of Jeffamine increased the barrier protection of the coating decreased. The lowest protection efficiency was found for HDGS samples synthesized with oligopolymers with an MW of 2000. Coatings produced with an oligopolymer of 230 MW conferred the highest protection. The surface morphology of the OIH coatings deposited on HDGS surfaces was studied by atomic force microscopy. The results show that the roughness of the OIH films depends on the MW of Jeffamine and on the number of dip-coating steps used. Thermogravimetry results show that the Jeffamine MW affected the thermal properties of the prepared OIH samples. The prepared OIH materials are thermally stable within the range of 20–80 C.The authors would like to gratefully acknowledge the financial support from Fundacao para a Ciencia e Tecnologia (FCT) for the PhD grant SFRH/BD/62601/2009 and EU COST action MP1202: HINT-"Rational design of hybrid organic-inorganic interfaces: the next step towards functional materials.''info:eu-repo/semantics/publishedVersio