Herein, the construction of a novel, low-cost and disposable electrochemical sensor is presented by using recyclable material as an alternative with bucky paper (BP) as an electrode material. The polyethyleneterephthalate (PET) obtained from a drinking bottle was used as sensing platform. The CO2 laser were used for producing sensing substrate and the desired three electrode pattern of BP. This was attached on the PET substrate using double side tape. The lamination process was used to define the geometric area and for insulating the electrode. The determination of Xanthine (Xn) and Uric Acid (UA) were carried out as a proof of concept with unmodified BP surface. The electrochemical behaviour of Xn and UA were studied using cyclic voltammetry (CV), differential pulse voltammetry (DPV). The anodic peak for Xn and UA were observed at 0.4 V and 0.2 V respectively. The calibration curve for Xn and UA were obtained in the linear range 10 µM -500 µM and 50 µM - 1000 µM respectively. The LOD obtained for Xn and UA was 6 µM and 22.5 µM respectively. Finally, the proposed method was applied for determination of Xn and UA in human serum sample with good selectivity and high sensitivity.

In recent times,extensive research isbeing carried out for the development of simple, low-cost point-of-care microfluidic platforms for electroanalytical applications. Microfluidic devices (μFDs) are very attractive in the field of clinical, food and environmental analysis owing to their advantages over conventional method likeless reagent consumption and rapid analysis[1-3].Polymerand paper stands out to be most potential substrate for fabricating such devices that require being in contact with bodily fluid such as blood, serum and urine depending upon their biocompatibility, flexibility and ease-of-use [4-5]. The integration of such disposable μFDs with electrochemical analysis gives new capabilities and functionalities that enables detection of several compounds with high accuracy. Polymersubstrates are known for its transparency, flexibility, non-absorbent and toughness properties. Screen-printing has become popular for disposable electrochemical sensor to prepare carbon conductive pathway [6].For printing, the carbon structures are well dispersed in liquid, and variousink parameters, like density, viscosity and surface tension, need to be carefully evaluated.Even though screen printed electrode (SPE) offers high performance and reliability but the high electrical resistance, produced due to the polymer binders, leads to non-uniform electrode surface and affect the performance of the device[7]. Owing to this limitation, use of carbon/graphene paper as a simple alternative to develop disposable electrochemical sensor. However, mechanical transfer of carbon/ graphene layer to the flexible substrate is an essential step towards a simple transfer technique. Herein, a novelrealization of disposable electrochemical sensor is presented by using recyclable polymer material as an alternative to produce low-cost electrochemical sensor with buckypaper (BP) as an electrode material. The polyethyleneterephthalate(PET) obtained from drinking bottle were used as sensing platform.BP is a flexible self-supporting material of entangled assembles of multi-walled carbon nanotube with outstanding electrochemical, mechanical and piezoresistive properties leading to broad range of application in lithium-ion batteries, fuel cells and Solar cells. The CO2 laser was used for producing sensing substrate and desired three electrode pattern of BP, and was attached on the PET substrate using double side tape. The lamination process was used to define the geometric area and for insulating the electrode. The determination of Xanthine(Xn) and Uric Acid (UA) were chosen as a proof of concept with unmodified BPsurface.Xn and UA are produced during purine metabolism wherein Xn is an intermediate product whileUA is a final product present in tissues and bodily fluids like urine and blood. Xn produces final purine metabolite, leads to abnormality in UA level which is responsible for various diseases symptoms. The electrochemical behaviour of Xn and UA were studied using cyclicvoltammetry (CV), differential pulse voltammetry(DPV) and chronoamperometery (CA) The anodic peak for Xn and UA were observed at 0.4 V and 0.12 V.The calibration curve for Xn and UA were obtained in the linear range 30µM- 500µM and 50 µM- 1000µM respectively by CV. The limit of detection (LOD) obtained for Xn and UA was 23µM and 38µM respectively. Finally, the proposed method was applied for simultaneous determination of Xn and UA in human serum sample with good selectivity and high sensitivity. The disposable micro-electrochemical sensor provides a new approach for the fabrication of new sensing platform and has broad range of application for simultaneous detection of various analyte forpoint-of-care analysis. References [1]‘Beebe, David J., Glennys A. Mensing, and Glenn M. Walker. "Physics and applications of microfluidics in biology." Annual review of biomedical engineering 4.1 (2002): 261-286. [2]Nilghaz, Azadeh, et al. "Flexible microfluidic cloth-based analytical devices using a low-cost wax patterning technique." Lab on a Chip 12.1 (2012): 209-218.. [3]Salve, Mary, et al. "Greenly synthesized silver nanoparticles for supercapacitor and electrochemical sensing applications in a 3D printed microfluidic platform." Microchemical Journal 157 (2020): 104973. [4]Songjaroen, Temsiri, et al. "Blood separation on microfluidic paper-based analytical devices." Lab on a Chip 12.18 (2012): 3392-3398. [5]Hou, Guanglei, et al. "Ultratrace detection of glucose with enzyme-functionalized single nanochannels." Journal of Materials Chemistry A 2.45 (2014): 19131-19135. [6]Mettakoonpitak, Jaruwan, et al. "Electrochemistry on paper‐based analytical devices: a review." Electroanalysis 28.7 (2016): 1420-1436. [7]Adkins, Jaclyn A., and Charles S. Henry."Electrochemical detection in paper-based analytical devices using microwire electrodes." Analytica chimicaacta 891 (2015): 247-254. Figure 1

Herein, a novel, low-cost and disposable electrochemical sensor is presented by using recycled base material polyethyleneterephthalate (PET) obtained from a disposable drinking water bottle as a sensing platform. Bucky paper (BP) was used as a working electrode material. The CO2 laser was used for fabricating sensing substrate and the desired three electrode pattern of BP. This was attached on the PET substrate using a double sided tape. The lamination process was used to define the geometric area and for insulating the electrode. The determination of Xanthine (Xn) and Uric Acid (UA) were carried out as a proof of concept with unmodified BP surface. The electrochemical behavior of Xn and UA was studied using a cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometery (CA). The calibration curve for Xn and UA were obtained in the linear range 10 μM−500 μM and 50 μM−1000 μM respectively using and CA. The LOD obtained for Xn and UA was 6 μM and 22.5 μM respectively. Finally, the proposed method was applied for determination of Xn and UA in human serum sample with good selectivity and high sensitivity.