Sustainable Copper Electrochemical Stripping onto a Paper-Based Substrate for Clinical Application

The electroanalyticalfield has exploited great advantages in usingpaper-based substrates, even if the word paper mightbe general. In fact, the mainly adopted paper-based substrates areoften chromatographic and office ones. They are characterized by thefollowing main features (and drawbacks): chromatographic paper iswell-established for storing reagents/treating samples, but the sensitivitycompared to traditional screen-printed ones is lower (due to porosity),while office paper represents a sustainable alternative to plastic(with similar sensitivity), but its porosity is not enough to loadreagents. To overcome the limitations that might arise due to theadoption of a type of individual paper-based substrate, herein, wedescribe for the first time the development of a two-dimensional mergedpaper-based device for electrochemical copper ion detection in serum.In this work, we report a novel configuration to produce an integratedall-in-one electrochemical device, in which no additional workingmedium has to be added by the end user and the sensitivity can betuned by rapid preconcentration on porous paper, with the advantageof making the platform adaptable to real matrix scenarios. The novelarchitecture has been obtained by combining office paper to screen-printa sustainable and robust electrochemical strip and a chromatographicdisk to (1) store the reagents, (2) collect real samples, and (3)preconcentrate the analyte of interest. The novel sensing platformhas allowed us to obtain a detection limit for copper ions down to4 ppb in all the solutions that have been investigated, namely, standardsolutions and serum, and a repeatability of ca. 10% has been obtained.Inductively coupled plasma-mass spectrometry measurements confirmedthe satisfactory correlation.

Automated summary

The electroanalytical field has made great progress in using paper-based substrates, but different types of paper substrates have their own characteristics and limitations. In this study, a novel two-dimensional merged paper-based device was developed for electrochemical copper ion detection in serum. This integrated device combined office paper, screen-printed electrochemical strips, and chromatographic disks to achieve an all-in-one electrochemical platform. The novel architecture allowed for sensitivity tuning and achieved a detection limit of 4 ppb for copper ions with a repeatability of approximately 10%.