A reagent-free paper-based sensor embedded in a 3D printing device for cholinesterase activity measurement in serum

Herein, we report a first example of a rapid and easy to use paper-based printed sensor embedded in a 3D printing device to measure the butyrylcholinesterase activity in serum samples. The innovative device relies on a paper-based sensor fabricated using wax printing and screen-printing technologies, combined with a printed holder made by stereolithography using 3D printing technology. To measure the butyrylcholinesterase activity, butyrylthiocholine was used as enzymatic substrate and the by-product thiocholine was detected with a paper-based electrochemical sensor modified with a Carbon Black and Prussian Blue nanocomposite. The presence of this nanocomposite allowed to perform the butyrylcholinesterase activity measurement at low applied potential (+ 300 mV vs. Ag/AgCl pseudoreference), since it is able to electrocatalyse the thiocholine oxidation, overcoming the fouling problem occurring at a bare electrode. To obtain a reagent free sensor, butyrylthiocholine was loaded on the filter paper for are liable stand-alone measurement, requiring only the sample addition. This device, after the calibration with standard solutions, was tested in serum samples, achieving a linear range up to 12 UI/mL and a detection limit of 0.5 IU/mL. To evaluate the accuracy of the device, recovery studies were performed in serum samples, demonstrating the suitability as a point of care for screening analysis of BChE activity measurement, taking into account that the normal value range is comprised between 5.9 and 13.2 IU/mL. (C) 2017 Elsevier B.V. All rights reserved.