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- Fuel cells operating as an immunosensor for cancer biomarker screeningPublication . Ferreira, Nadia S.; Carneiro, Liliana P.T; Pinto, Alexandra M.F.R.; Sales, M. Goreti F.This work presents the first integration of antibodies into one of the electrodes of a passive direct methanol fuel cell (DMFC) to create an autonomous immunosensor for cancer antigen 15–3 (CA15-3). The anode of the fuel cell was first made of carbon cloth with carbon black, platinum and ruthenium nanoparticles and then modified with anti-CA15-3, while the cathode was made of carbon cloth with carbon black and platinum nanoparticles. This hybrid DMFC (hDMFC), which works as an immunosensor, was fed with dilute methanol to generate a concentration-dependent current. The hDMFC device was calibrated in different media (buffer and serum), by incubating increasing concentrations of CA15-3 standard solutions, ranging from 47 to 750 U/mL. The linear response ranged from 188 to 563 U/mL, and the limit of detection (LoD) was 39.8 U/mL. The selectivity of the biosensor was also evaluated with competing cancer biomarkers, such as carcinoembryonic antigen (CEA), and cancer antigen 125 (CA-125), as well as with other compounds normally present in blood plasma (ascorbic acid, glucose, uric acid and urea), adjusted to the normal range of concentrations in serum. The results obtained indicate good selectivity of the immunosensor in the fuel cell. In general, the immunosensor showed a good response considering its integration into a passive DMFC. It is a good sensor for point-of-care (PoC) diagnosis because it has a good performance in human serum and, most importantly, it pursues electrical autonomy.
- An all-in-one approach for self-powered sensing: A methanol fuel cell modified with a molecularly imprinted polymer for cancer biomarker detectionPublication . Carneiro, Liliana P.T; Pinto, Alexandra M.F.R.; Mendes, Adélio; Ferreira Sales, Maria GoretiThis work describes the development of an innovative electrochemical biosensor comprehending a passive direct methanol fuel cell (DMFC) assembly, modified by a layer of a molecularly imprinted polymer (MIP) on a carbon fabric anode electrode containing Pt/Ru nanoparticles. This MIP film was prepared from poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) obtained by in situ electropolymerization of the corresponding monomers on the anode electrode surface. This MIP film is designed to detect an important cancer biomarker- carcinoembryonic antigen (CEA). This innovative, all-in-one device works in a simple way. First, CEA is incubated on the anode container of the fuel cell, then methanol is added, followed by the response evaluation (polarization curves determination). As CEA selectively interacts with the MIP film, it blocks the methanol's access to the Pt catalyst, remains specific bonded, and interferes with the subsequent polarization curves of the DMFC. Polarization curves obtained in the presence of standard solutions prepared in buffer and human serum confirmed linear responses of log CEA concentration ranging from 30 to 30 000 ng/mL in both media. The biosensor DMFC showed a sensitive response with a detection limit of 4.41 ng/mL when an aqueous 0.05 M methanol solution was used as fuel. When methanol was replaced by an ethanol solution of the same concentration (using the same setup developed for the DMFC), the lower detection limit of 3.52 ng/mL was obtained. Overall, the obtained results show that methanol/ethanol fuel cells operating without flow-through can be successfully used for the fabrication of self-powered biosensors. The novel biosensor concept presented here is simple, inexpensive, and effective, and can be further developed to meet point-of-care requirements.
- 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.