Browsing by Author "Marques, Ana C."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Paper-based (bio)sensor for label-free detection of 3-nitrotyrosine in human urine samples using molecular imprinted polymerPublication . Martins, Gabriela V.; Marques, Ana C.; Fortunato, Elvira; Sales, Maria Goreti FerreiraOver the last years, paper technology has been widely spread as a more affordable, sustainable and reliable support material to be incorporated in the design of point-of-care (POC) diagnostic devices. However, the single work employing a paper-based device for 3-nitrotyrosine (3-NT), a relevant biomarker for oxidative stress (OS) that is a major origin for many diseases, is incapable of reading successfully complex samples because every species that oxidizes before ~0.75 V will also contribute to the final response. Thus, the introduction of a selective element was made into this set-up by including a molecularly-imprinted polymer (MIP) tailored in-situ. Herein, a novel MIP for 3-NT was assembled directly on a paper platform, made conductive with carbon ink and suitable for an electrochemical transduction. The biomimetic material was produced by electropolymerization of phenol after optimizing several experimental parameters, such a scan-rate, number of cycles, range of potential applied, monomer and template concentrations. Under optimal conditions, the label-free sensor was able to respond to 3-NT from 500 nM to 1 mM, yielding a limit of detection of 22.3 nM. Finally, the applicability of the (bio)sensor was tested by performing calibration assays in human urine samples and a good performance was obtained in terms of sensitivity, selectivity and reproducibility. Overall, the attributes of the herein described sensing approach can be compared to a very limited number of other electrochemical devices, that are still using a conventional three electrode system, making this paper-sustained device the first electrochemical (bio)sensor with potential to become a portable and low-cost diagnostic tool for 3-NT. In general, the incorporation of molecular imprinting technology coupled to electrochemical transduction enabled the fabrication of suitable smart sensors for wide screening approaches.
- Paper-Based Platform with an In Situ Molecularly Imprinted Polymer for β-AmyloidPublication . Pereira, Marta V.; Marques, Ana C.; Oliveira, Daniela; Martins, Rodrigo; Moreira, Felismina; Sales, Maria Goreti Ferreira; Fortunato, ElviraAlzheimer’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.
- Passive direct methanol fuel cells acting as fully autonomous electrochemical biosensors: Application to sarcosine detectionPublication . Silva Ferreira, Nadia; Carneiro, Liliana P.T; Viezzer, Christian; Almeida, Maria J.T.; Marques, Ana C.; Pinto, Alexandra M.F.R.; Fortunato, Elvira; Ferreira Sales, Maria GoretiThis work describes an innovative electrochemical biosensor that advances its autonomy toward an equipment-free design. The biosensor is powered by a passive direct methanol fuel cell (DMFC) and signals the response via an electrochromic display. Briefly, the anode side of the DMFC power source was modified with a biosensor layer developed using molecularly imprinted polymer (MIP) technology to detect sarcosine (an amino acid derivative that is a potential cancer biomarker). The biosensor layer was anchored on the surface of the anode carbon electrode (carbon black with Pt/Ru, 40:20). This was done by bulk radical polymerization with acrylamide, bis-acrylamide, and vinyl phosphonic acid. This layer selectively interacted with sarcosine when integrated into the passive DMFC (single or multiple, in a stack of 4), which acted as a transducer element in a concentration-dependent process. Serial assembly of a stack of hybrid DMFC/biosensor devices triggered an external electrochromic cell (EC) that produced a colour change. Calibrations showed a concentration-dependent sarcosine response from 3.2 to 2000 µM, which is compatible with the concentration of sarcosine in the blood of prostate cancer patients. The final DMFC/biosensor-EC platform showed a colour change perceptible to the naked eye in the presence of increasing sarcosine concentrations. This colour change was controlled by the DMFC operation, making this approach a self-controlled and self-signalling device. Overall, this approach is a proof-of-concept for a fully autonomous biosensor powered by a chemical fuel. This simple and low-cost approach offers the potential to be deployed anywhere and is particularly suitable for point-of-care (POC) analysis.