Amperometric Biosensor based on Prussian Blue Nanoparticle-modified

25 26 Glucose-6-phosphate (G6P) plays an important role in carbohydrate metabolism of all living 27 organisms. Compared to the conventional analytical methods available for estimation of G6P, the 28 biosensors having relative simplicity, specificity, low-cost and fast response time are a promising 29 alternative. We have reported a G6P biosensor based on screen-printed electrode utilizing 30 Prussian Blue (PB) nanoparticles and enzymes, glucose-6-phosphate dehydrogenase and 31 glutathione reductase. The PB nanoparticles acted as a mediator and thereby enhanced the rate of 32 electron transfer in a bi-enzymatic reaction. The Fourier transform infrared spectroscopy 33 and energy-dispersive X-ray spectroscopy study confirmed the formation of PB, whereas, the 34 atomic forced microscopy revealed that PB nanoparticles were about 25-30 nm in diameter. 35 Various optimization studies, such as pH, enzyme and cofactor loading, etc. were conducted to 36 obtain maximum amperometric responses for G6P measurement. The developed G6P biosensor 37 showed a broad linear response in the range of 0.01-1.25 mM with a detection limit of 2.3 µM 38 and sensitivity of 63.3 µA/mM at a signal-to-noise ratio of 3 within 15 s at an applied working 39 potential of-100 mV. The proposed G6P biosensor also exhibited good stability, excellent anti-40 interference ability and worked well for serum samples.