Browsing by Author "Carneiro, Liliana P.T."
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- Employing bacteria machinery for antibiotic detection: Using DNA gyrase for ciprofloxacin detectionPublication . Cardoso, Ana Rita; Carneiro, Liliana P.T.; Cabral-Miranda, Gustavo; Bachmann, Martin F.; Sales, Maria Goreti FerreiraThis work describes a new successful approach for designing biosensors that detect antibiotics. It makes use of a biomimetic strategy, by employing the biochemical target of a given antibiotic as its biorecognition element. This principle was tested herein for quinolones, which target DNA gyrase in bacteria. Ciprofloxacin (CIPRO) was tested as a representative antibiotic from the quinolone group; the sensitivity of biosensor to this group was confirmed by checking the response to another quinolone antibiotic (norfloxacin, NOR) and to a non-quinolone antibiotic (ampicillin, AMP). The biorecognition element used was DNA gyrase attached by ionic interactions to a carbon support, on a working electrode on common screen-printed electrodes (SPEs). The response against antibiotics was tested for increasing concentrations of CIPRO, NOR or AMP, and following the subsequent electrical changes by electrochemical impedance spectroscopy. The DNAgyrase biosensor showed sensitive responses for CIPRO and NOR, for concentrations down to 3.02 nM and 30.2 nM, respectively, with a very wide response range for CRIPRO, up to 30.2 µM. Its response was also confirmed selective for quinolones, when compared to its response against AMP. Further comparison to an immunosensor of similar design (adding antibodies instead of DNA gyrase) was made, revealing favourable features for the new biomimetic biosensor with 1.52 nM of limit of detection (LOD). Overall, the new approach presented herein is simple and effective for antibiotic detection, displaying a selective response against a given antibiotic group. The use of bacterial machinery as biorecognition element in biosensors may also provide a valuable tool to study the mechanism of action in bacterial cells of new drugs. This is especially important in the development of new drugs to fight bacterial resistance.
- A passive direct methanol fuel cell as transducer of an electrochemical sensor, applied to the detection of carcinoembryonic antigenPublication . Carneiro, Liliana P.T.; Ferreira, Nádia S.; Tavares, Ana P.M.; Pinto, Alexandra M.F.R.; Mendes, Adélio; Sales, Maria Goreti FerreiraThis work describes an electrochemical sensor with a biomimetic plastic antibody film for carcinoembryonic antigen (CEA, an important biomarker in colorectal cancer), integrated in the electrical circuit of a direct methanol fuel cell (DMFC), working in passive mode and used herein as power supply and signal transducer. In detail, the sensing layer for CEA consisted of a Fluorine-doped Tin Oxide (FTO) conductive glass substrate – connected to the negative pole side of the DMFC – with a conductive poly (3,4-ethylenedioxythiophene) (PEDOT) layer and a polypyrrol (PPy) molecularly-imprinted polymer (MIP), assembled in-situ. This sensing element is then closed using a cover FTO-glass, hold in place with a clip, connected to the positive side of the DMFC. When compared with control DMFCs, the power curves of DMFC/Sensor integrated system showed decreased power values due to the MIP layer interfaced in the electrical circuit, also displaying high stability signals. The DMFC/Sensor was further calibrated at room temperature, in different medium (buffer, a synthetic physiological fluid model and Cormay® serum), showing linear responses over a wide concentration range, with a limit of detection of 0.08 ng/mL. The DMFC/Sensor presented sensitive data, with linear responses from 0.1 ng/mL to 100 μg/mL and operating well in the presence of human serum. Overall, the results obtained evidenced the possibility of using a DMFC as a transducing element in an electrochemical sensor, confirming the sensitive and selective readings of the bio (sensing) imprinted film. This integration paves the way towards fully autonomous electrochemical devices, in which the integration of the sensor inside the fuel cell may be a subsequent direction.