Paper-based electrochemical sensor with a commercial glucose meter to determine L-cysteine by graphene electrode and Ag-doped silica nanoporous SBA-16

This paper demonstrates the development and efficiency of a portable paper-based electrochemical sensor for determining amperometric L-cysteine levels with a personal glucometer (PGM). An electrochemical microfluidic paper-based analytical device (EmPAD) was designed as a glucometer test strip. For the fabrication of the EmPADs, chromatography paper was used as the substrate. A wax pencil was used to create a hydrophobic wall and hydrophilic channels. Also, graphene ink, Ag ink, and carbon ink were used to make the reference electrode and the working electrode by a screen printed method. (3-Aminopropyl) triethoxysilane (APTES)-SBA-16 was synthesized and characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), and scanning electron microscopy (SEM) techniques. The (APTES)-SBA-16 was added to the hydrophilic part to increase hydrophilicity. Ag/SBA-16 was added to modify the graphene electrode. The modified electrode exhibited good catalytic activity to oxidize L-cysteine. Our test strip made with a glucose meter and an amperometric readout is affordable and easy to use for in situ cysteine measurement at the point of care. The linear range of the calibration curve and the detection limit (S/N=3) was between 0.1 to 250 mu M and 0.02 mu M. The recoveries for the human urine samples analysis were in the range of 96%-110% for Cys. [GRAPHICS] .