Glucose sensor calibration curve

The blend of PVA with PEG- modified glucose oxidase could be used as glucose sensor characterized by the linearity of calibration curve in the range of concentration by 5 x 10"5 - 5 x 10"3 mol glucose L 1 [194],... 

Fig. 2.15 Theoretical (open points) and experimental (full points) calibration curve for glucose sensor for (a) 100% oxygen in 0.2 mM buffer, (b) 25% oxygen and 0.2 mM buffer, and (c) 100% oxygen and 1 mM buffer (adapted from Caras et al., 1985b, p. 1921)...

The calibration curves of the glucose sensor I are shown in Figure 6 and the linear range of the curves gradually decrease with decreasing of the oxygen tension from 21 to 5 %. 

Glucose sensors II and HI were prepared from the semipermeable membrane of PMSP, poly(1-trimethylsilyl-l-propyne), which has 4 times the oxygen permeability compared with that of FEP membrane. The response properties of sensor H, using a PMSP membrane with 25 Um diameter pinhole, were almost similer to that of the sensor I, so that their calibration curves were not presented in this paper. 

The calibration curves of the sensor IV, which was prepared with a PMSP membrane as an oxygen permeable membrane and an acetyl celulose(AC) membrane as a glucose semipermeable membrane, were shown in Figure 8. This AC membrane was cast by Manjikian s method and treated at a curing temperature of 85°C. The sensor ]V indicated a linear response up to 500 mg/dl of glucose concentration, even under 5 % of oxygen tension, and the output currents were hardly affected by oxygen tension. 

Figure 6. Calibration curves of glucose sensor I having glucose semipermeable FEPp membrane with 25 pm diameter pinhole.

Figure 7. Calibration curves of glucose sensor HI having glucose seraipermeable PMSPp( 1 ) membrane with 15ym diameter pinhole...

Figure 8. Calibration curves of glucose sensor ]y having a glucose semipermeable AC membrane. The AC membranes were cast using a solution of acetyl cellulose formamide aceton = 25 30 45 (wt %) and tempered at 85°C...

Figure 6. Effect of increased alkyl chain length on glucose sensor response glucose calibration curves for the ferrocene-modified poly(siloxane) / glucose oxidase / carbon paste electrodes at E = +300 mV (vs. SCE). The polymeric relay systems are indicated next to each curve, which is the mean result for four electrodes.

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. 

It is clear from these KMapp values, and from the glucose calibration curves, that the response of the sensors begins to deviate from linearity even at glucose concentrations below 10 mM (the response to glucose is expected to be strictly linear for concentrations approximately less than or equal to 0.1KMapp). We have previously... 

The effects of fouling were studied by obtaining glucose calibration curves for two ultramicrobiosensors, one without electropolymerized film, the other with poly(1,3-DAB). Both sensors were then placed in a solution containing 3% w/v bovine serum albumin, at temperature of 4°C, for 6 h. After 6 h, both sensors were again calibrated. 

The experiments were performed in batch mode with stirring. The sensor was placed in 20.00 mL of buffer in a three electrode configuration. The potential was applied (+150 mV vs SCE) and the response was allowed to reach baseline. The required amount of analyte was added to measure the response to electroactive interferents and to generate a glucose calibration curve. 

Fig. 12. Response curves and calibration curve of a glucose-sensitive FET sensor, (a) Response curves using continuous flow apparatus. An arrow indicates onset of analyte solution flow, [b) Response curve under homogeneous condition (see text for details). An arrow indicates addition of glucose, (c) Calibration curve using the flow apparatus. (Reproduced from Shiono et al. (9), with permission.)...

The response of the sensor peaked within 4 min and the calibration curve is applicable within the range of glucose concentrations in normal human serum. Another glucose sensor using sol-gel systems was based upon glucose oxidase in conjunction with a mediator compound (ferrocene or hexacyanoferrate) that transferred an electron to the enzyme [211], This system can be represented as... 

Figure 7.2. (a) Ferrocene-mediated glucose sensor (b) calibration curves recorded in N2, air, and 02-saturated solutions. 

Figure 4 Calibration curve of a glucose sensor with 1,2-DAB as the polymer film. Range 2-100mM glucose.

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. ... 

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