DNA-based Electrochemical Biosensor for Imipramine Detection

AbstractThe main aim of our research was development of a novel selective electrochemical method for imipramine (IMI) detection. This substance enable to interact with DNA and it is also electrochemically active. Two major groups of electrochemical sensors were used in the experiments with bare gold electrodes and DNA-modified. Determination of imipramine by means of non-modified electrodes was not selective and limit of detection was shifted towards higher concentrations of IMI. The sensitivity of mixed and mono-GC sequence DNA-modified electrodes was much higher than for the bare gold ones

Electrical characterization of ISFETs, Journal of Telecommunications and Information Technology, 2007, nr 3

Methodology of electrical characterization of ISFETs has been described. It is based on a three-stage approach. First, electrical measurements of ISFET-like MOSFETs and extraction of basic parameters of the MOSFET compact model are performed. Next, mapping of the ISFET channel conductances and a number of other characteristic parameters is carried out using a semi-automatic testing setup. Finally, ISFET sensitivity to solution pH is evaluated. The methodology is applied to characterize ISFETs fabricated in the Institute of Electron Technology (IET)

Optimization of Urea-EnFET Based on Ta2O5 Layer with Post Annealing

In this study, the urea-enzymatic field effect transistors (EnFETs) were investigated based on pH-ion sensitive field effect transistors (ISFETs) with tantalum pentoxide (Ta2O5) sensing membranes. In addition, a post N2 annealing was used to improve the sensing properties. At first, the pH sensitivity, hysteresis, drift, and light induced drift of the ISFETs were evaluated. After the covalent bonding process and urease immobilization, the urea sensitivity of the EnFETs were also investigated and compared with the conventional Si3N4 sensing layer. The ISFETs and EnFETs with annealed Ta2O5 sensing membranes showed the best responses, including the highest pH sensitivity (56.9 mV/pH, from pH 2 to pH 12) and also corresponded to the highest urea sensitivity (61 mV/pCurea, from 1 mM to 7.5 mM). Besides, the non-ideal factors of pH hysteresis, time drift, and light induced drift of the annealed samples were also lower than the controlled Ta2O5 and Si3N4 sensing membranes

Surface Modification for Microreactor Fabrication

In this paper, methods of surface modification of different supports, i.e. glass andpolymeric beads for enzyme immobilisation are described. The developed method ofenzyme immobilisation is based on Schiff’s base formation between the amino groups onthe enzyme surface and the aldehyde groups on the chemically modified surface of thesupports. The surface of silicon modified by APTS and GOPS with immobilised enzymewas characterised by atomic force microscopy (AFM), time-of-flight secondary ion massspectroscopy (ToF-SIMS) and infrared spectroscopy (FTIR). The supports withimmobilised enzyme (urease) were also tested in combination with microreactors fabricatedin silicon and Perspex, operating in a flow-through system. For microreactors filled withurease immobilised on glass beads (Sigma) and on polymeric beads (PAN), a very high andstable signal (pH change) was obtained. The developed method of urease immobilisationcan be stated to be very effective

pH-based Detection of Phenylalnine by Potentiometric and Colorimetric Methods

In this paper, methods of sample preparation for potentiometric measurement ofphenylalanine are presented. Basing on the spectrophotometric measurements ofphenylalanine, the concentrations of reagents of the enzymatic reaction (10 mM L-Phe,0,4 mM NAD+ , 2U L-PheDH) were determined. Then, the absorption spectrum of thereaction product, NADH, was monitored (maximum peak at 340 nm). The results obtainedby the spectrophotometric method were compared with the results obtained by thecolourimetry, using pH indicators. The above-mentioned two methods will be used asreferences for potentiometric measurements of phenylalanine concentration

Semiconductor chemical and biochemical sensors

Abstract In this paper, problems related to the fabrication of semiconductor (bio)chemical sensors and microreactors, including modification of the surface of different materials (semiconductors, dielectric materials, polymers) to create a sensing membrane on the transducer's surface and immobilise bioreceptors namely enzymes are discussed

Comparison of Gold Nanoparticles Deposition Methods and Their Influence on Electrochemical and Adsorption Properties of Titanium Dioxide Nanotubes

The increasing interest of attachment of gold nanoparticles (AuNPs) on titanium dioxide nanotubes (TNTs) has been devoted to obtaining tremendous properties suitable for biosensor applications. Achieving precise control of the attachment and shape of AuNPs by methods described in the literature are far from satisfactory. This work shows the comparison of physical adsorption (PA), cyclic voltammetry (CV) and chronoamperometry (CA) methods and the parameters of these methods on TNTs properties. The structural, chemical, phase and electrochemical characterizations of TNTs, Au/TNTs, AuNPs/TNTs are carried out using scanning electron microscopy (SEM), electrochemical impedance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The use of PA methods does not allow the deposition of AuNPs on TNTs. CV allows easily obtaining spherical nanoparticles, for which the diameter increases from 20.3 ± 2.9 nm to 182.3 ± 51.7 nm as a concentration of tetrachloroauric acid solution increase from 0.1 mM to 10 mM. Increasing the AuNPs deposition time in the CA method increases the amount of gold, but the AuNPs diameter does not change (35.0 ± 5 nm). Importantly, the CA method also causes the dissolution of the nanotubes layer from 1000 ± 10.0 nm to 823 ± 15.3 nm. Modification of titanium dioxide nanotubes with gold nanoparticles improved the electron transfer and increased the corrosion resistance, as well as promoted the protein adsorption. Importantly, after the deposition of bovine serum albumin, an almost 5.5-fold (324%) increase in real impedance, compared to TNTs (59%) was observed. We found that the Au nanoparticles—especially those with smaller diameter—promoted the stability of bovine serum albumin binding to the TNTs platform. It confirms that the modification of TNTs with gold nanoparticles allows the development of the best platform for biosensing applications

Fabrication of Electrochemical Biosensor Based on Titanium Dioxide Nanotubes and Silver Nanoparticles for Heat Shock Protein 70 Detection

This paper presents the fabrication methodology of an electrochemical biosensor for the detection of heat shock protein 70 (HSP70) as a potential tumor marker with high diagnostic sensitivity. The sensor substrate was a composite based on titanium dioxide nanotubes (TNTs) and silver nanoparticles (AgNPs) produced directly on TNTs by electrodeposition, to which anti-HSP70 antibodies were attached by covalent functionalization. This manuscript contains a detailed description of the production, modification, and the complete characteristics of the material used as a biosensor platform. As-formed TNTs, annealed TNTs, and the final sensor platform—AgNPs/TNTs, were tested using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction analysis (XRD). In addition, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) of these substrates were used to assess the influence of TNTs modification on their electrochemical characteristics. The EIS technique was used to monitor the functionalization steps of the AgNPs/TNTs electrode and the interaction between anti-HSP70 and HSP70. The produced composite was characterized by high purity, and electrical conductivity improved more than twice compared to unmodified TNTs. The linear detection range of HSP70 of the developed biosensor was in the concentration range from 0.1 to 100 ng/mL