Papers by Brian Maccraith
Cellular and Molecular Life Sciences, 2011
Nanoparticles (NPs) comprised of nanoengineered complexes are providing new opportunities for ena... more Nanoparticles (NPs) comprised of nanoengineered complexes are providing new opportunities for enabling targeted delivery of a range of therapeutics and combinations. A range of functionalities can be included within a nanoparticle complex, including surface chemistry that allows attachment of cell-specific ligands for targeted delivery, surface coatings to increase circulation times for enhanced bioavailability, specific materials on the surface or in the nanoparticle core that enable storage of a therapeutic cargo until the target site is reached, and materials sensitive to local or remote actuation cues that allow controlled delivery of therapeutics to the target cells. However, despite the potential benefits of NPs as smart drug delivery and diagnostic systems, much research is still required to evaluate potential toxicity issues related to the chemical properties of NP materials, as well as their size and shape. The need to validate each NP for safety and efficacy with each therapeutic compound or combination of therapeutics is an enormous challenge, which forces industry to focus mainly on those nanoparticle materials where data on safety and efficacy already exists, i.e., predominantly polymer NPs. However, the enhanced functionality affordable by inclusion of metallic materials as part of nanoengineered particles provides a wealth of new opportunity for innovation and new, more effective, and safer therapeutics for applications such as cancer and cardiovascular diseases, which require selective targeting of the therapeutic to maximize effectiveness while avoiding adverse effects on non-target tissues.
Analytica Chimica Acta, Jun 1, 2006
A sol-gel-based optical sensor for the measurement of relative humidity has been developed. It is... more A sol-gel-based optical sensor for the measurement of relative humidity has been developed. It is based on the changes in fluorescence intensity and/or lifetime of the ruthenium complex, ruthenium(II)diphenylphenanthroline-dipyridophenazinehexafluorophosphate. Sensitivity to relative humidity has been demonstrated over the range 0-100% relative humidity. This sensor has been developed for application in the field of indoor air-quality monitoring and displays a limit of detection of 0.35% relative humidity and a resolution of 1.13% over the concentration range of interest (0-50% relative humidity). The effects of varying process parameters on the sensor performance were studied along with the effects of cross-sensitivity to molecular oxygen.
The operation of an efficient cw thulium-doped fiber laser emitting at wavelength, lambda equals ... more The operation of an efficient cw thulium-doped fiber laser emitting at wavelength, lambda equals 2.31 micrometer is reported. The operation of the fiber laser is optimized with a view to producing a small and efficient laser source for optical absorption based gas sensing. A 2 mW output power combined with a high slope efficiency make this fiber laser a useful
Sol-Gel Technologies for Glass Producers and Users, 2004
J Sol Gel Sci Technol, 1994
Sol-gel silica thin films, produced by a dip-coating process, were impregnated with the complexes... more Sol-gel silica thin films, produced by a dip-coating process, were impregnated with the complexes Ru(bpy)a 2+ and Ru(Ph2phen)3 2+. For each complex ruthenium fluorescence was quenched in the presence of oxygen. Intensity and decay time Stern-Volmer plots were produced for both complexes. The optical decay times were analysed in terms of one quenched and one unquenched component, the latter arising from the fraction of complex molecules which are inaccessible to oxygen. All the data were consistent with the predominance of dynamic quenching in these systems. The feasibility of an oxygen sensor based on decay times was discussed.
This study focuses on the optimisation and characterisation of novel, ORganically MOdified SILica... more This study focuses on the optimisation and characterisation of novel, ORganically MOdified SILicate (ORMOSIL)-based, hybrid sensor films for use in the detection of O2 on a breath-bybreath basis in human health monitoring applications. The sensing principle is based on the luminescence quenching of the O2-sensitive ruthenium complex [Ru(II)-tris(4,7-diphenyl-1,10phenanthroline)], which has been entrapped in a porous sol–gel film. The detection method employed is that of phase fluorometry using blue LED excitation and photodiode detection. Candidate sensor films include those based on the organosilicon precursors, methyltriethoxysilane, ethyltriethoxysilane, n-propyltriethoxysilane and phenyltriethoxysilane. While it has been established previously by the authors that these films exhibit a stable, highly sensitive response to O2, this study focuses on selecting the material most suited for use in a breath monitor, based on the sensitivity, response time and humidity sensitivity of th...
Coordination Chemistry Reviews, 1999
... References. 1. (a) BD Macraith, C. McDonagh, G. O'Keeffe, TE Keyes, JG Vos. B. O'Ke... more ... References. 1. (a) BD Macraith, C. McDonagh, G. O'Keeffe, TE Keyes, JG Vos. B. O'Kelly, JFMcGilp, Analyst 118 (1993) 385. ... (b) J. Fan, HD Gaffney, J. Phys. Chem. 98 (1994) 13058. (c) B. Grass, O. Katz, J. Samuel, D. Avnir, M. Ottelenghi, J. Phys. Chem. 99 (1995) 14893. ...
Plasmonics, 2006
Abstract This paper reports on the enhancement of fluorescence that can result from the proximity... more Abstract This paper reports on the enhancement of fluorescence that can result from the proximity of fluorophores to metallic nanoparticles (NPs). This plasmonic enhancement, which is a result of the localized surface plasmon resonance at the metal surface, can be ...
Opto-Ireland 2002: Optics and Photonics Technologies and Applications, 2003
ABSTRACT An optical sensor system, which provides real-time process information during the curing... more ABSTRACT An optical sensor system, which provides real-time process information during the curing of DVD adhesive within the DVD manufacturing process, is reported. Incomplete or non-uniform curing of the adhesive in the centre of the disk can cause variation in layer thickness or create stresses, which may cause warping of the disk. The monitoring of adhesive cure is then of vital importance to manufacturers, particularly if this can be achieved in situ and within the production cycle time for disk manufacture. The operating principle of the sensor is the detection of changes in the infrared absorption spectrum of the adhesive as it cures. The use of infrared absorption in itself is not straightforward as the adhesive is sandwiched between two polycarbonate disks. One of these disks is completely opaque throughout the infrared due to the aluminium layer deposited on it and the other disk has a semi-reflective layer of a material such as silicon, gold or silver. The sensor employs a reflectance based interrogation technique, which uses the highly reflective aluminium coated surface of the DVD. The work described here deals principally with (i) definition of the specifications of the sensor system and the measurement methodology, (ii) development and optimization of a laboratory prototype sensor and (iii) design of an industrial prototype system. Results are presented from both prototype systems.
Chemical, Biochemical, and Environmental Fiber Sensors VIII, 1996
ABSTRACT
Thin Solid Films, 2006
We describe the synthesis and refractive index characterisation of four organo-siloxanes material... more We describe the synthesis and refractive index characterisation of four organo-siloxanes materials, applicable to the fabrication of photo-patternable channel waveguides. By combining aliphatic, aromatic and vinylic alkoxysilane precursors, organically modified silicates materials have been synthesised using the sol–gel process. Control of the refractive index was achieved through the variation of aliphatic and aromatic alkoxide content within the materials. It is
Integrated Optics and Photonic Integrated Circuits, 2004
There is a clear need for low cost, high performance and large-scale production of photonic chips... more There is a clear need for low cost, high performance and large-scale production of photonic chips. Network development requires more interconnecting components. A flexible and low-cost process using good quality material is necessary. The sol-gel process is a chemical method to fabricate glasses at ambient pressure and moderate temperature. The resulting material properties can be tuned depending on the precursors
Opto-Ireland 2005: Optical Sensing and Spectroscopy, 2005
We report the development of enhanced optical platforms for fluorescence-based biosensors. A prev... more We report the development of enhanced optical platforms for fluorescence-based biosensors. A previous analysis by us has shown that the emission of fluorescence in such a system is highly anisotropic and is preferentially emitted into the substrate over a well-defined angular range, with the result that the light is guided along the substrate via total internal reflection. However, conventional optical biosensors based on fluorescence detection typically employ a detector that is positioned either directly above or directly below the biochip. As a consequence, only a small fraction of the total emitted fluorescence is detected, which impacts adversely on sensor performance. The enhanced biosensor presented here is based on a novel, generic platform specifically designed to overcome the inherent limitations of planar substrates. The platform incorporates custom-designed optical elements, the purpose of which is to redirect the emitted fluorescence onto a detector positioned beneath the biochip. Platforms were fabricated using the polymer processing technique of microinjection moulding. In this paper we demonstrate the ability of this optical system to achieve a 80-fold luminescence capture enhancement. We also demonstrate its effectiveness as an enhanced biosensor platform by carrying out a proof of principle BSA/antiBSA competitive assay. This work has significant implications for the development of mass-producible, highly efficient optical biosensors.
The Analyst, 2005
This paper describes the development of a generic platform for enhanced, integrated optic sensors... more 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.
The Analyst, 2002
An optical sensor for the measurement of carbon dioxide in Modified Atmosphere Packaging (MAP) ap... more 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% CO 2 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.
Sensors and Actuators B: Chemical, 2009
We present an optical sol-gel-based pH sensor which compares well with the current state-of-the-a... more We present an optical sol-gel-based pH sensor which compares well with the current state-of-the-art in terms of the combination of resolution, stability, response time and leaching characteristics. The pHsensitive dye used is the fluorescent indicator 8-hydroxy-1,3,6-pyrene trisulfonic acid (HPTS) which has been ion-paired with hexadecyltrimethylammonium bromide (CTAB). The sol-gel matrix is a composite of the precursors 3-glycidoxypropyltrimethoxysilane (GPTMS) and ethyltriethoxysilane (ETEOS) in which the dye is completely physically entrapped with no leaching. A referenced excitation ratiometric sensor detection system is used which capitalises on the dual excitation bands of the dye. The sensor has a dynamic range from pH 5.0 to pH 8.0, a resolution of 0.02 pH units and exhibits excellent reproducibility, reversibility, temporal stability and a short response time of 12 s.
Journal of Non-Crystalline Solids, 1998
The effect of different processing parameters on the efficiency of entrapment of pH indicators in... more The effect of different processing parameters on the efficiency of entrapment of pH indicators in a sol-gel-derived silica film is reported. An evanescent wave absorption approach was used to monitor dopant-leaching from these films. The issues investigated include the effect on the rate of leaching of the water:alkoxide ratio, the pH of the leachant solution and the choice of silicon alkoxide. Results indicate that the most suitable sol-gel films in terms of leaching and response time are those prepared using tetraethoxysilane as precursor, acid catalysis and a water:alkoxide ratio of at least 4. Leaching is more pronounced for films used directly after preparation and varies for different pH environments. Implications of leaching for the long-term use of sol-gel based pH sensors are discussed. q 1998 Elsevier Science B.V.
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Papers by Brian Maccraith