Paper-Based Platform with an In Situ Molecularly Imprinted Polymer for β-Amyloid

Alzheimer’s disease (AD) is one of the most common forms of dementia affecting millions of people worldwide. Currently, an easy and effective form of diagnosis is missing, which significantly hinders a possible improvement of the patient’s quality of life. In this context, biosensors emerge as a future solution, opening the doors for preventive medicine and allowing the premature diagnosis of numerous pathologies. This work presents a pioneering biosensor that combines a bottom-up design approach using paper as a platform for the electrochemical recognition of peptide amyloid β-42 (Aβ-42), a biomarker for AD present in blood, associated with visible differences in the brain tissue and responsible for the formation of senile plaques. The sensor layer relies on a molecularly imprinted polymer as a biorecognition element, created on the carbon ink electrode’s surface by electropolymerizing a mixture of the target analyte (Aβ-42) and a monomer (O-phenylenediamine) at neutral pH 7.2. Next, the template molecule was removed from the polymeric network by enzymatic and acidic treatments. The vacant sites so obtained preserved the shape of the imprinted protein and were able to rebind the target analyte. Morphological and chemical analyses were performed in order to control the surface modification of the materials. The analytical performance of the biosensor was evaluated by an electroanalytical technique, namely, square wave voltammetry. For this purpose, the analytical response of the biosensor was tested with standard solutions ranging from 0.1 ng/mL to 1 μg/mL of Aβ-42. The linear response of the biosensor went down to 0.1 ng/mL. Overall, the developed biosensor offered numerous benefits, such as simplicity, low cost, reproducibility, fast response, and repeatability less than 10%. All together, these features may have a strong impact in the early detection of AD.The authors acknowledge funding from project PTDC/AAG-TEC/5400/2014, POCI-01-0145-FEDER-016637, POCI-01-0145-FEDER-007688, and UID/CTM/50025/2019 funded by European funds through FEDER (European Funding or Regional Development) via COMPETE2020—POCI (operational program for internationalization and competitively) by national funding through the National Foundation for Science and Technology, I.P. (FCT-MCTES). Additionally, they are grateful to the project IBEROS, Instituto de Bioingeniería en Red para el Envejecimiento Saludable, POCTEP/0245-BEROS-1-E, PROGRAMA INTERREG 2014-2020 funded through FEDER within the cooperation region of Galiza/Spain and North of Portugal. A.C.M. and F.T.C.M. gratefully acknowledges FCT-MCTES for the financial support (PhD grant reference SFRH/BD/115173/2016 intituled “Nanobiosensing platform based on MIP-SERS for breast cancer exosome characterization and detection” and Post-Doc grant reference SFRH/BPD/97891/2013 intituled “Biomedical devices for easier and quicker screening procedures of the Alzheimer’s). This work is part of the Master Thesis in Micro and Nanotechnology Engineering defended by Marta V. Pereira. at FCT NOVA titled “Fabrication of 3D electrodes for biosensor applications” in December 2018.