Glucose sensor linear response range

Table 1 Linear response range and response time of glucose sensors with various glucose semipermeable membranes...

The linear response range of the glucose sensors can be estimated from a Michaelis-Menten analysis of the glucose calibration curves. The apparent Michaelis-Menten constant KMapp can be determined from the electrochemical Eadie-Hofstee form of the Michaelis-Menten equation, i = i - KMapp(i/C), where i is the steady-state current, i is the maximum current, and C is the glucose concentration. A plot of i versus i/C (an electrochemical Eadie-Hofstee plot) produces a straight line, and provides both KMapp (-slope) and i (y-intercept). The apparent Michaelis-Menten constant characterizes the enzyme electrode, not the enzyme itself. It provides a measure of the substrate concentration range over which the electrode response is approximately linear. A summary of the KMapp values obtained from this analysis is shown in Table I. 

The linear response range of sensors was estimated from a Adichaelis-Menten analysis of the glucose calibration curves in Figure 4. The apparent Nfichaelis-Menten constant Kj pp can be determined from the electrochemical Eadie-Hofstee form of the Michaelis-Menten equation. ... 

Sensors should always be evaluated in vitro. While this is clearly not a substitute for in vivo testing, it is easier to diagnose fundamental problems without the complications that the biological milieu introduces. Furthermore, if they do not work reliably in vitro, they will not work in vivo. In addition to the linear dynamic range mentioned above, stability and reproducibility of characteristics in sensor production are very important. Linearity can be characterized by comparing the sensitivities (slope of the dose/response curve) at 5 and 15 mM glucose, assuming that they should not deviate by more than 10%. Stability can be measured in several different ways. Sensors can be stored dry and at room temperature between periodic sensitivity checks. This tends to... 

A miniaturized planar amperometric glucose sensor has been created on Sapphire substrates. Thin film titanium-gold electrodes are covered with an enzyme layer which is patterned by a lift-off technique [66]. This sensor exhibits a fast response time of 30 seconds but the linear measuring range is poor. 

The direct electron transfer between GOD and an electrochemically pretreated platinum electrode has been studied by Durliat and Comtat (1984). Spectroelectrochemical investigations showed that GOD was quantitatively reduced at the electrode. A GOD solution (100 pmol/1) was entrapped in a reaction chamber of 0.04 mm thickness in front of the electrode by a dialysis membrane. The electrode was pretreated by cyclic sweeping between -700 mV and +900 mV for 8 h. In anaerobic solution this sensor responded to glucose at a potential of +450 mV with a response time of 6 min and a linear concentration range between 0.01 and 7 mmol/1. 

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