Browsing by Author "Marrazza, Giovanna"

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    Evaluation of an FIA Operated Amperometric Bacterial Biosensor, Based on Pseudomonas Putida F1 for the Detection of Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX)
    (Taylor and Francis, 2005) Rasinger, Josef D.; Marrazza, Giovanna; Briganti, Fabrizio; Scozzafava, Andrea; Mascini, Marco; Turner, Anthony P. F.
    Recently, the development and optimization of a flow injection analysis (FIA) operated bacterial biosensor based on the aerobic catabolism of Pseudomonas putida ML2 was reported in the literature (Lanyon et al. 2004, 2005). By adapting information from these reports, we investigated whether operating parameters and procedures of the benzene biosensor could be directly applied to a new system based on a different bacterial strain for the detection of the whole benzene, toluene, ethylbenzene, and xylenes range. Cells of the investigated bacterial strain, Pseudomonas putida F1, were immobilized between two cellulose acetate membranes and fixed onto a Clark dissolved oxygen electrode. The P. putida F1 aerobically degrades benzene, toluene, and ethylbenzene (BTE) (Cho et al. 2000). The BTE biosensor in kinetic mode FIA displayed a linear range of 0.02-0.14 mM benzene (response time: 5 min, base-line recovery time: 15 min), 0.05-0.2 mM toluene (response time: 8 min, baseline recovery time: 20 min), and 0.1-0.2 mM ethylbenzene (response time: 12 min, baseline recovery time: 30 min), respectively. Due to the differences in sensitivity, response, and baseline recovery times for BTE, it was possible to differentiate each compound in mixtures of these volatile organic compounds (VOCs). No response for xylenes could be obtained since they cannot be completely metabolized by this bacterial strain. However, it was reported that the range of compounds degradable by P. putida F1 can possibly be expanded by cultivating the cells on different carbon sources (Choi et al. 2003). The sensor showed good intra- and interassay reproducibility, and all obtained results were comparable with those reported in the literature. The demonstrated reproducibility and the simplicity and ease of use as well as the portability for in situ measurements indicates that the biosensor could be suitable as a reliable initial warning device for elevated BTE levels in indoor and outdoor environments.
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    New micro-and nano-technologies for biosensor development
    (Cranfield University, 2009) Berti, Francesca; Turner, Anthony P. F.; Marrazza, Giovanna
    Recent advances in micro- and nanotechnology have produced a number of new materials which exhibit exceptional potential for the design of novel sensing strategies and to enhance the analytical performance of biosensing systems. In this thesis three different types of miniaturisation pathways were investigated for electrochemical biosensing applications. Vertically aligned carbon nanotube thin films were designed and tested as platforms for DNA immobilisation and for the development of a model electrochemical genosensor. The sensor format involved the immobilisation of oligoucleotide probes onto the sensor surface, hybridisation with the target sequence and electrochemical detection of the duplex formation. By combining such an electrode platform with an enzyme labeling, a detection limit of oligonucleotide targets in the nanomolar range was achieved. A novel magnetic particle-based microfluidic sensor was also realised by integrating a microfluidic platform with a new analytical procedure based on the use of paramagnetic beads for the detection of real PCR samples. The hybridisation reaction was carried out on probe-modified beads in a flow-through format, thus enhancing the surface area-to-volume ratio and consequently the sensitivity. Moreover, the magnetic properties of the beads greatly facilitated the delivery and removal of reagents through the microfluidic channels. This format allowed the detection of nanomolar levels of double-stranded DNA sequences, with high reproducibility and fast time of analysis. Finally, polyaniline nanotubes arranged in an ordered structure directly on gold electrode surfaces were realised and employed to create a model molecularly imprinted (MIP) polymer -sensor for catechol detection. The advantages of using nanostructures in this particular biosensing application have been evaluated by comparing the analytical performance of the sensor with an analogous non-nanostructured MIP-sensor that we had previously developed. A significantly lower limit of detection (one order of magnitude) was achieved, thus demonstrating that the nanostructures enhanced the analytical performance of the sensor.