http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:11386 An amperometric glucose biosensor was fabricated by entrapment of glucose oxidase in a composite matrix of silica sol-gel and polyvinyl alcohol physically layered on top of a Prussian blue-modified Pt electrode. This biosensor functions through the detection of hydrogen peroxide produced by the glucose oxidase-catalyzed oxidation of glucose at -0.05 V. The biosensor exhibited high selectivity, and a sensitivity of 3.41 μA/mM, due to a combination of electroreduction of H₂O₂ at the surface of the modified Pt electrode at low potential and a sympathetic microenvironment for enzyme immobilization provided by the silica sol-gel. The biosensor had a linear response to glucose over the range 5.0×10⁻⁵ to 2.5×10⁻³ M, with a response time of less than 8 sec. The detection limit of the biosensor is 4.0 μM, based on a signal-to-noise ratio of 3. The biosensor exhibits satisfactory long-term stability; 85% of its original activity was retained after 30 days of storage in phosphate buffer (pH 6.9; 0.1 M) at 4 °C. 2012-08-27T22:30:07.155Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:7474 A simple, polishable and renewable DNA biosensor was fabricated based on a zirconia modified carbon paste electrode. Zirconia was mixed with graphite powder and paraffin wax to produce the paste for the electrode, and response-optimized at 56% graphite powder, 19% ZrO₂ and 25% paraffin wax. An oligonucleotide probe with a terminal 5´-phosphate group was attached to the surface of the electrode via the strong affinity of zirconia for phosphate groups. DNA immobilization and hybridization were characterized by cyclic voltammetry and differential pulse voltammetry, using methylene blue as indicator. Examination of changes in response with complementary or non-complementary DNA sequences showed that the developed biosensor had a high selectivity and sensitivity towards hybridization detection (≤2×10⁻¹⁰ M complementary DNA detectable). The surface of the biosensor can be renewed quickly and reproducibly (signal RSD±4.6% for five successive renewals) by a simple polishing step. 2011-03-25T05:30:21.615Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:5642 A simple, disposable, and inexpensive electrochemical DNA biosensor based on a zirconia (ZrO₂) modified thin film screen-printed electrode (ZrO₂/SPE) has been developed. Short DNA sequences (21 monomer units) from the Escherichia coli pathogen, modified with a phosphate group at the 5′ end,were attached to the surface of the electrode through the affinity of the phosphate group for zirconia, to produce an effective DNA probe (ssDNA/ZrO₂/SPE). DNA immobilization and hybridization were characterized using differential pulse voltammetry by employing methylene blue as redox indicator. Target sequences hybridized with the probe resulted in a decrease of the reduction peak current of methylene blue intercalated into the probe. The response of a non-complementary sequence and a single base pair mismatch sequence were both clearly distinguished from that of a complementary sequence. The developed biosensor had a high selectivity and sensitivity towards hybridization detection (10⁻¹⁰M complementary DNA detectable). Making use of screen-printed technology, the fabrication of the biosensors exhibited satisfactory reproducibility, investigated by cyclic voltammetry and differential pulse voltammetry. The relative standard deviation was found to be <3.0% for six bare SPEs and six ssDNA-modified SPEs (ssDNA/ZrO₂/SPE) from a batch. 2010-04-27T04:38:55.281Z ]]>