Biomedical subjects

Brian D MacCraith

Publications and source records attributed to Brian D MacCraith.

4 recordsLinked to original sources

PubMed2004

Development of an integrated optic oxygen sensor using a novel, generic platform.

This paper describes the development of a generic platform for enhanced, integrated optic sensors based on fluorescence detection. The platform employs a novel optical configuration in order to achieve enhanced performance and has inherent multianalyte detection capability. The sensor element comprises a multimode ridge waveguide that has been patterned with an analyte-sensitive fluorescent spot, which is excited directly using a LED. The platform was applied to the detection of gaseous oxygen as a proof of principle. The sol-gel-derived sensor spots were doped with an oxygen-sensitive fluorescent dichlororuthenium dye complex and intensity-based calibration data were generated from the oxygen-dependent waveguide output. The sensor achieved a LOD of 0.62% and a resolution of less than 0.96% gaseous oxygen, which compares favourably with a similar, recently reported system. This device highlights the combination of inexpensive rapid prototyping techniques and a dedicated sensor enhancement strategy that together facilitate the production of an effective prototype sensor platform.

Journal Article↗

PubMed2004

Development of a micro-fluidic manifold for copper monitoring utilising chemiluminescence detection.

The progressive development of a micro-fluidic manifold for the chemiluminescent detection of copper in water samples, based on the measurement of light emitted from the Cu(ii) catalysed oxidation of 1,10-phenanthroline by hydrogen peroxide, is reported. Micro-fluidic manifolds were designed and manufactured from polymethylmethacrylate (PMMA) using three micro-fabrication techniques, namely hot embossing, laser ablation and direct micro-milling. The final laser ablated design incorporated a reagent mixing channel of dimensions 7.3 cm in length and 250 x 250 microm in width and depth (triangular cross section), and a detection channel of 2.1 cm in length and 250 x 250 microm in width and depth (total approx. volume of between 16 to 22 microL). Optimised reagents conditions were found to be 0.07 mM 1,10-phenanthroline, containing 0.10 M cetyltrimethylammonium bromide and 0.075 M sodium hydroxide (reagent 1 delivered at 0.025 mL min(-1)) and 5% hydrogen peroxide (reagent 2 delivered at 0.025 mL min(-1)). The sample stream was mixed with reagent 1 in the mixing channel and subsequently mixed with reagent 2 at the start of the detection channel. The laser ablated manifold was found to give a linear response (R(2) = 0.998) over the concentration ranges 0-150 microg L(-1) and be reproducible (% RSD = 3.4 for five repeat injections of a 75 microg L(-1) std). Detection limits for Cu(ii) were found to be 20 microg L(-1). Selectivity was investigated using a copper selective mini-chelating column, which showed common cations found in drinking waters did not cause interference with the detection of Cu(ii). Finally the optimised system was successfully used for trace Cu(ii) determinations in a standard reference freshwater sample (SRM 1640).

Catalysis↗

PubMed2002

Optimization of absorption-based optical chemical sensors that employ a single-reflection configuration.

An optimization strategy for a generic absorption-based optical chemical sensor that employs a single-reflection planar configuration is reported. A theoretical model describing the sensor sensitivity is presented and verified experimentally. It is shown that optimum sensitivity is not achieved with an evanescent-wave sensing technique but with a configuration in which the interrogating light propagates within the sensing layer. Moreover, an optimization strategy based on identification of an optimized reflection angle is described. This analysis provides an optimization strategy that is extendable to multimode waveguide platforms. The predictions of the model are used in the design of a prototype LED-based sensor system. The performance of this system is examined, and the results are compared with alternative absorption-based sensor configurations.

Journal Article↗

PubMed2002

Sol-gel based optical carbon dioxide sensor employing dual luminophore referencing for application in food packaging technology.

An optical sensor for the measurement of carbon dioxide in Modified Atmosphere Packaging (MAP) applications has been developed. It is based on the fluorescent pH indicator 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) immobilised in a hydrophobic organically modified silica (ormosil) matrix. Cetyltrimethylammonium hydroxide was used as an internal buffer system. Fluorescence is measured in the phase domain by means of the Dual Luminophore Referencing (DLR) sensing scheme which provides many of the advantages of lifetime-based fluorometric sensors and makes it compatible with established optical oxygen sensor technology. The long-term stability of the sensor membranes has been investigated. The sensor displays 13.5 degrees phase shift between 0 and 100% CO2 with a resolution of better than 1% and a limit of detection of 0.08%. Oxygen cross-sensitivity is minimised (0.6% quenching in air) by immobilising the reference luminophore in polymer nano-beads. Cross-sensitivity towards chloride and pH was found to be negligible. Temperature effects were studied, and a linear Arrhenius correlation between ln k and 1/T was found. The sensor is stable over a period of at least seven months and its output is in excellent agreement with a standard reference method for carbon dioxide analysis.

Carbon Dioxide↗