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

Publication . Pereira, Marta V.; Marques, Ana C.; Oliveira, Daniela; Martins, Rodrigo; Moreira, Felismina; Sales, Maria Goreti Ferreira; Fortunato, Elvira

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.

2020-05Journal article

Open access

Homemade 3-carbon electrode system for electrochemical sensing: Application to microRNA detection

Publication . Carneiro, Mariana C.C.G.; Moreira, Felismina T.C.; Dutra, Rosa A.F.; Fernandes, Rúben; Sales, M. Goreti F.

The homemade production of carbon screen-printed electrodes (C-SPEs) with a three‑carbon electrode system is reported, along with its application in electrochemical sensing. It is highlighted herein as main novelty that a simple carbon ink may be employed in the preparation of the 3-electrode system, including the pseudo-reference electrode, thereby avoiding the addition of silver or other suitable metal and simplify the construction of such devices, reducing costs and time. Screen-printed technology was employed to produce the 3-electrodes and the corresponding electrical paths. This was achieved by the manual application of a commercial carbon ink into a polyvinyl chloride (PVC) substrate allowing the production of > 20 SPEs. The optimization of the SPE assembly was made by univariate mode, until the best electrical features of the electrode-solution interface were achieved. Several electrochemical techniques were used for this purpose, namely cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). Raman Spectroscopy and Thermogravimetric Analysis (TGA) were also used for materials and electrode surface characterization. The usefulness of such devices was tested by modifying the working electrode with a sensing layer for microRNA-107, a potential biomarker in Alzheimer's Disease (AD). For this purpose, the surface was functionalized with carboxylic groups, activated by carbodiimide reaction and bound to a suitable oligonucleotide probe containing the complementary sequence. Finally, the microRNA-107 sequence hybridized with its probe, proving the efficiency of the C-SPEs in electrochemical sensing. Overall, this study brings into light the possibility of preparing simple homemade electrodes with a 3‑carbon electrode system that stands out by the low cost, disposability and versatility of the presented platform, holding a great potential for application in point-of-care devices using electrochemical sensing.

2018Journal article

Open access