A novel amperometric biosensor based on ZnO nanoparticles-modified carbon paste electrode for determination of glucose in human serum

Figures & data

Figure 1. Cyclic voltammograms of bare and ZnONPs modified carbon paste electrodes in 0.1 M pH 7.0 PBS in absence (a, c) and presence (b, d) of 1.0 mM H₂O₂ at scan rate of 50 mV s^{− 1}.

Figure 2. Effect of GOx unit on sensitivity of ZnONPs modified carbon paste enzyme electrode (0.1 M pH 7.0 PBS at + 0.4 V vs. Ag/AgCl).

Figure 3. Effect of pH value on sensitivity of ZnONPs modified carbon paste enzyme electrode (0.1 M pH 7.0 PBS at + 0.4 V vs. Ag/AgCl).

Figure 4. Effect of temperature on the sensitivity of ZnONPs modified carbon paste enzyme electrode (0.1 M pH 7.0 PBS at + 0.4 V vs. Ag/AgCl).

Figure 5. Effect of glucose concentration on amperometric response of ZnONPs modified carbon paste enzyme electrode, inset: linear working ranges plots (0.1 M pH 7.0 PBS at + 0.4 V vs. Ag/AgCl).

Figure 6. Substrate concentration/current response vs. substrate concentration plot (Hanes-Woolf plot).

Table I. Reusability and reproducibility for ZnONPs modified carbon paste enzyme electrode.

Sensitivities (μA/mM)
For reusability*	For reproducibility*
1.402	1.308
1.421	1.441
1.339	1.393
1.368	1.426
1.306	–
%RSD = 3.307	%RSD = 4.273

*The results have been given sensitivities of five measurements for reusability and four different electrodes for reproducibility. Relative standard deviations were calculated for both of them.

Figure 7. Storage stability of ZnONPs modified carbon paste enzyme electrode stored at 4°C (The applied potential + 0.4 V vs. Ag/AgCl).

Table II. Effects of interferences on glucose response.

Interfering species	Concentration^a (mM)	Interference^b (%)
L-Ascorbic acid	0.1	8.94
Creatinine	0.1	4.05
Urea	0.8	4.83
Uric acid	0.05	5.69

^aThe electrochemical cell concentration of interfering species.

^b% interference = (Ix − I0)/I0 × %100; I0: The amperometric response of buffer solution containing 0.1 mM glucose solution, Ix:: The amperometric response of buffer solution containing 0.1 mM glucose and interfering species with above concentration.

Table III. The determination of glucose levels in human serum samples.

	Glucose concentration (mg/dL)
Serum samples	Determined by proposed biosensor*	Provided by the hospital
1	87.8 ± 0.6	88
2	104.7 ± 3.0	101
3	386.4 ± 7.5	388

*The results have been given average of three measurements.