# Electrochemical Paper-Based Analytical Device (e-PAD) Using Immobilized Prussian Blue and Antibodies for the Diagnosis of Leishmania

## TL;DR

A low-cost paper-based device was developed for diagnosing Leishmania, a neglected disease, using electrochemical detection of antigens.

## Contribution

A novel e-PAD device using Prussian Blue and antibodies for Leishmania antigen detection was developed and tested.

## Key findings

- The e-PAD device demonstrated good reproducibility (RSD = 5.12%) and selectivity in detecting Leishmania antigens.
- The device uses a sandwich immunoassay with antibodies and Prussian Blue for electrochemical detection.
- The e-PAD is cost-effective and suitable for rapid diagnosis in underserved regions.

## Abstract

Leishmaniasis is
a neglected disease prevalent in remote
and economically
disadvantaged regions. Its diagnosis can be achieved through various
methods, with electroanalysis emerging as an excellent alternative
for antigen detection due to its simplicity, sensitivity, and cost-effectiveness.
Herein, a qualitative electrochemical paper-based analytical device
(e-PAD) using unmodified screen-printed electrodes for the immunoassay
of Leishmania amazonensis antigens
has been developed. The detection is based on a sandwich-type assembly,
utilizing two biological elements, one for capture and one for detection,
with the target antigen sandwiched between them. Antibodies against Leishmania amazonensis and Prussian blue, serving
as a redox mediator, were immobilized on the paper substrate. A synthetic
peptide was employed as the target to demonstrate the proof-of-concept
performance of the device. The formation of the immunocomplex was
confirmed using horseradish peroxidase (HRP)-labeled antibodies, enabling
the detection of antigen/antibody complexes in the presence of hydrogen
peroxide via multiple pulse amperometry (MPA). The immunoassay exhibited
good reproducibility (RSD = 5.12%) and selectivity when tested with
positive and negative samples. Additionally, the ease of use and low
cost of e-PAD enhance its accessibility, making it a valuable tool
for the rapid and reliable diagnosis of neglected diseases. This reinforces
its relevance as a practical solution in public health, particularly
in underserved regions.