Studies on Carbon Mediated Paste Screen Printed Sensors for Blood Glucose Sensing Application

Ready to use screen printed glucose sensors are fabricated using Prussian Blue (PB) and Cobalt PhthaloCyanine (CoPC) mediated carbon paste as working electrodes. The reference and counter electrodes are screen printed using silver/silver chloride and graphitic carbon paste respectively. The stability of screen printed reference electrode (SPRE) is examined with standard calomel electrode and found to be stable for more than 60 minutes. Optimal operating voltage for PB and CoPC screen printed sensors as determined by hydrodynamic voltammetric technique are 0.3 V and -0.1 V respectively. The sensing response of fabricated sensors towards H₂O₂ is conducted. Amperometric sensing response of PB screen printed sensor to H₂O₂ has limit of detection (LOD) of 0.5 μM with sensitivity of 63.690 mAcm^-2/mM. Sensing response is found to be linear for the range, 1 to 4500 μM. While the CoPC screen printed sensor has LOD 0.05 μM with sensitivity of 56.66 mA cm^-2/mM to H₂O₂. The response is linear for the range, 0.1 to 7500 μM. Glucose oxidase is immobilized on the working electrodes by cross-linking method using Glutaraldehyde and Nafion. Electrochemical sensing responses of the fabricated sensors for glucose are studied. PB mediated glucose sensor exhibits a sensitivity of 5.60 mA cm^-2/mM with LOD of 7 μM. The response is observed to be linear for the range, 10 to1000 μM with linearity co-efficient of 0.9990. Sensitivity and LOD of CoPC mediated glucose sensor are found to be 5.224 mA cm^-2/mM and 70 μM respectively. The amperometeric response is linear for the range, 100 to 1500 μM with linearity co-efficient of 0.9973. Inference studies on the fabricated glucose sensors are conducted with species like uric acid and ascorbic acid. PB mediated sensors showed a completely interference-free behavior, while CoPC mediated sensors are influenced by uric acid and ascorbic acid due to higher operating voltage.  The sensing response of PB mediated glucose sensors is also studied in diluted human serum samples and the results are compared with values obtained by standard spectrometric method.  The correlation co-efficient is found to be 0.935 and hence the sensor has potential application in clinical diagnostics.