Combined Paper-Based Substrates for Electrochemical Detection of Copper Ions in Serum

The electroanalytical field has exploited great advantages in using paper-based substrates, even if the word “paper” might be general. In fact, the mainly adopted paper-based substrates are often chromatographic and office ones. They are characterized by main features (and drawbacks): chromatographic paper is well-established for storing reagents/treating samples but the sensitivity compared to traditional screen-printed is lower (due to porosity), while office paper represents a sustainable alternative to plastic (with similar sensitivity) but its porosity is not enough to load reagents. To overcome the limitations that might arise due to the adoption of a type of individual paper-based substrate, herein we describe for the first time, the development of a 2D merged paper-based devices for electrochemical copper ions detection in serum. In this work we report a novel configuration to produce an integrated all-in-one electrochemical device, in which no additional working media has to be added by the end user and the sensitivity can be tuned by rapid pre-concentration on porous paper, with the advantage of making the platform adaptable to real matrix scenario. The novel architecture has been obtained by combining office paper to screen-print a sustainable and robust electrochemical strip, the printed electrochemical strips and chromatographic one to 1) store the reagents, 2) collect real sample and 3) pre-concentrate the analyte of interest. The novel sensing platform has allowed to obtain a detection limit for copper ions down to 5 ppb in all the solutions that have been interrogated, namely standard solution and serum, and a repeatability of ca. 10% has been obtained.