Highly sensitive disposable test strips for sweat chloride detection using silver nanoparticles decorated reduced graphene oxide

The quantification of chloride ions in sweat by a point-of-care test system is a useful strategy in the early screening of cystic fibrosis. In this context, silver nanoparticles decorated reduced graphene oxide were synthesized by one-pot reduction method in this work. This reaction in situ produces silver nanoparticles spread across thin sheets of rGO with high surface area. This helps in the electrochemical detection of chloride ions by conversion of silver to silver chloride and formation of a thin layer of silver chloride on the surface of nanocomposite. The validity of this strategy has been demonstrated by voltammetric analysis of chloride ions using the screen-printed Ag-rGO nanocomposite. For electrodes tested in buffer, the sensitivity was 37.66 +/- 0.99 mA (log mM)- 1 cm- 2 with a high selectivity and detection range from 30 to 400 mM chloride concentration. The lower detection limit is 1.02 mM (S/N = 3), and the relative standard deviation (RSD) of sensor response is 4.77 %. Disposable sensor test strips fabricated with screen printing of the catalyst followed by layer by layer array of electrolyte and hydrophilic membrane shows a sensitivity of 165.2 +/- 4.3 mu A mM- 1 cm- 2, a linear detection range upto 210 mM, and a LOD of 2.46 +/- 0.06 mu M. The quantification of the developed sensor strips were confirmed by comparing the values from clinical laboratories. This finding confirms the potentiality of the developed method and its possible application in the rapid and easy-to-use point-of-care devices. Notable advantages of the Ag-rGO nanocomposite is its reversibility due to the regeneration of fresh silver nanoparticles on the rGO surface and increased electrochemical response. This feature realizes a high stability even at multiple trials with a RSD of 2.63 % and long-time storage tested upto 3 months. Using this superior performance, the developed sensor test strip demonstrates a disposable, non-invasive, reproducible, reversible, highly selective, and sensitive monitoring of chloride ions.