Figure 1 illustrates the FET-based biosensor structure and the measurement system, showing the connection diagram of the instrumentation amplifier AD620.Figure 1.Schematic illustration of the FET-based else biosensor measurement system showing the connection diagram of the instrumentation amplifier AD620 used as unity gain buffer.3.?Results and Discussion3.1. Glucose ResponseThe enzyme immobilization process is an important step in biosensor fabrication since the enzyme cannot be lixiviate from the support. Inhibitors,Modulators,Libraries GA is an extensively used cross-linking Inhibitors,Modulators,Libraries agent in enzyme immobilization processes in combination with BSA. Figure 2 displays the typical response of the PPI/NiTsPc-GOx FET-based biosensor and the influence of the BSA on the output signal.
Inhibitors,Modulators,Libraries A response time��defined as the time necessary to reach 90% of the steady-state response [12]��of about 7 min can be estimated. This time appears to be slightly lower for the biosensor without BSA due to the faster ionic diffusion, as the presence of BSA may make the H+ diffusion difficult. Inhibitors,Modulators,Libraries On the other hand, the presence of BSA allows greater exposure of the enzyme active sites, since they are not used in the cross-linking process, enhancing the enzyme activity and thus improving the biosensor signal.Figure 2.Response of PPI/NiTsPc-GOx FET-based biosensor with (black line) and without (red line) the presence of BSA in the process of enzyme immobilization to detect 0.5 mM of glucose. Measurement conditions: buffer solution 10 mM, pH 7.5.The dependence of the voltage response versus glucose concentration (analytical curve) is shown in Figure 3.
The linear range is up to 0.4 mM with detection limit of 0.027 mM determined in the linear region of the biosensor calibration curve according to the literature [13].Figure 3.Analytical curve of the PPI/NiTsPc-GOx FET-based biosensor. Measurement conditions: buffer solution 10 mM, pH 7.5The greatest obstacle in the development of FET-based Anacetrapib glucose biosensors is their dynamic range limitation due to the low oxygen concentration of real blood samples. Although at first a sensitivity of up to 1 mM seems to be out of the range of interest, which is about 4�C7 mM for real blood samples, our sensor is able to detect diluted human serum samples as suggested in the literature [14].
Using such a strategy, the sensors proposed here coul
The accurate measurement of NH4+ ion in an aquatic environment is of significant interest in environmental biological studies and the environmental evaluation following website of water since it is known to be toxic for aquatic organisms. In this sense, several methods have been proposed, most of them involving ion chromatography [1�C3], potentiometry [4,5] or flow injection systems [6�C11].Most of the ion chromatography procedures proposed for its determination involve elaborate pre-column derivatization in some kind of matrix. Mori et al.