Peter Owens | University of Galway (original) (raw)
Papers by Peter Owens
Journal of Nanomedicine & Nanotechnology, 2014
Reported here is the use of novel nanogold based photosensitisers (nanosensitisers) as optical di... more Reported here is the use of novel nanogold based photosensitisers (nanosensitisers) as optical diagnostic probes and as potential photodynamic and photothermal cancer therapeutic agents using an in vitro cancer cell model. Such multimodal nanosensitisers were constructed by layering photosensitisers (Hypericin, Chlorin e6) onto multi-branched gold nanoparticles. Nanosensitisers were conjugated to tumour-specific antibodies to confer cancer-cell specificity. Both oral (SCC9) and breast cancer (MCF7) cell lines were cultured in vitro with various concentrations of nanosensitisers. Cellular uptake and intracellular localisation of nanosensitisers was assessed using darkfield contrast imaging, transmission electron microscopy and Raman spectroscopy imaging and quantified using confocal fluorescence microscopy. In addition to photodynamic diagnosis (PDD) efficacy, the photodynamic (PDT) and photothermal (PTT) therapeutic potential of these novel nanosensitisers was assessed. Treated cells were exposed to light of appropriate wavelength and fluence, and cytotoxicity was examined using the 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. It was observed that nanosensitisers were taken up by cells and internalized. While the intracellular target of nanosensitisers appeared to be cell type-dependent, they were found to localise preferentially to lysosomes and mitochondria. The nanosensitisers were shown to exert minimal dark toxicity, and significant photodynamic-mediated cell death was observed in the micromolar concentration range (p<0.05). Results from this study suggest a celltype and photosensitiser-type dependence on the rate of nanosensitiser cellular uptake and intracellular distribution. This has a direct effect on photodynamic therapeutic efficacy of nanosenitisers. Biocompatibility of these novel gold nanosensitisers in vitro was demonstrated and the potential of such novel nanosensitisers as multifunctional optical agents for cancer diagnosis and therapy was highlighted.
Biosensors, 2015
In this paper we describe a method for the determination of protein concentration using Surface E... more In this paper we describe a method for the determination of protein concentration using Surface Enhanced Raman Resonance Scattering (SERRS) immunoassays. We use two different Raman active linkers, 4-aminothiophenol and 6-mercaptopurine, to bind to a high sensitivity SERS substrate and investigate the influence of varying concentrations of p53 and EGFR on the Raman spectra. Perturbations in the spectra are due to the influence of protein-antibody binding on Raman linker molecules and are attributed to small changes in localised mechanical stress, which are enhanced by SERRS. These influences are greatest for peaks due to the C-S functional group and the Full Width Half Maximum (FWHM) was found to be inversely proportional to protein concentration.
Journal of Fluorescence, 2008
Journal of Biomedical Optics, 2016
To facilitate regular assessment of the microcirculation in-vivo, non-invasive imaging techniques... more To facilitate regular assessment of the microcirculation in-vivo, non-invasive imaging techniques such as nailfold capillaroscopy are required in clinics. Recently a correlation mapping technique has been applied to Optical Coherence Tomography (OCT) which extends the capabilities of OCT to microcirculation morphology imaging. This technique, known as cmOCT has been shown to extract parameters such as capillary density and vessel diameter, key clinical markers associated with early changes in microvascular diseases. However, OCT has limited spatial resolution in both the transverse and depth directions. Here, we extend this correlation mapping technique to other microscopy modalities, including confocal microscopy and take advantage of the higher spatial resolution offered by these modalities. The technique is achieved as a processing step on microscopy images and does not require any modification to the microscope hardware. Results are presented which show that this correlation mapping microscopy technique can extend the capabilities of conventional microscopy to enable mapping of vascular networks in-vivo with high spatial resolution in both the transverse and depth directions.
We have studied the low-temperature (133À298 K) fluorescence emission of crude petroleum oils usi... more We have studied the low-temperature (133À298 K) fluorescence emission of crude petroleum oils using a combination of steady-state and time-resolved measurements. This was done, first, to see if we could generate linear correlations between the oil composition information and the fluorescence measurements and, second, to better understand how static and dynamic quenching affect fluorescence emission. It was observed that the fluorescence intensity and the lifetime of the crude oils increased rapidly with decreasing temperature down to the freezing point, and then, they either remained constant or, surprisingly, began to decrease slightly. These changes could not be correlated accurately with the compositional data available. However, despite the very large variations in sample composition, it was found that these lifetimeÀtemperature changes followed simple Arrhenius and Eyring behavior. For the cold liquid phase, an Arrhenius model enabled the calculation of an intrinsic lifetime, the magnitude of which was inversely related to the degree of static quenching. The low values of the calculated activation energies (4.6À 19.2 kJ mol À1 ) implied that, in the liquid phase, nonradiative decay was primarily diffusion based quenching. At the lowest temperatures, when all samples have solidified, the lifetime data followed Eyring like behavior, giving typical enthalpy and entropy values of À1 kJ mol À1 and from À67 to À93 J K À1 mol À1 , respectively. The Eyring model was used to describe the nonradiative decay mechanism arising from the vibrational coupling from the fluorophores to the surrounding matrix. This modeling of the temperature dependence of the fluorescence lifetime has provided a clearer, quantitative picture of the fluorescence quenching processes in crude petroleum oils.
Journal of Nanomedicine & Nanotechnology, 2014
Reported here is the use of novel nanogold based photosensitisers (nanosensitisers) as optical di... more Reported here is the use of novel nanogold based photosensitisers (nanosensitisers) as optical diagnostic probes and as potential photodynamic and photothermal cancer therapeutic agents using an in vitro cancer cell model. Such multimodal nanosensitisers were constructed by layering photosensitisers (Hypericin, Chlorin e6) onto multi-branched gold nanoparticles. Nanosensitisers were conjugated to tumour-specific antibodies to confer cancer-cell specificity. Both oral (SCC9) and breast cancer (MCF7) cell lines were cultured in vitro with various concentrations of nanosensitisers. Cellular uptake and intracellular localisation of nanosensitisers was assessed using darkfield contrast imaging, transmission electron microscopy and Raman spectroscopy imaging and quantified using confocal fluorescence microscopy. In addition to photodynamic diagnosis (PDD) efficacy, the photodynamic (PDT) and photothermal (PTT) therapeutic potential of these novel nanosensitisers was assessed. Treated cells were exposed to light of appropriate wavelength and fluence, and cytotoxicity was examined using the 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. It was observed that nanosensitisers were taken up by cells and internalized. While the intracellular target of nanosensitisers appeared to be cell type-dependent, they were found to localise preferentially to lysosomes and mitochondria. The nanosensitisers were shown to exert minimal dark toxicity, and significant photodynamic-mediated cell death was observed in the micromolar concentration range (p<0.05). Results from this study suggest a celltype and photosensitiser-type dependence on the rate of nanosensitiser cellular uptake and intracellular distribution. This has a direct effect on photodynamic therapeutic efficacy of nanosenitisers. Biocompatibility of these novel gold nanosensitisers in vitro was demonstrated and the potential of such novel nanosensitisers as multifunctional optical agents for cancer diagnosis and therapy was highlighted.
Biosensors, 2015
In this paper we describe a method for the determination of protein concentration using Surface E... more In this paper we describe a method for the determination of protein concentration using Surface Enhanced Raman Resonance Scattering (SERRS) immunoassays. We use two different Raman active linkers, 4-aminothiophenol and 6-mercaptopurine, to bind to a high sensitivity SERS substrate and investigate the influence of varying concentrations of p53 and EGFR on the Raman spectra. Perturbations in the spectra are due to the influence of protein-antibody binding on Raman linker molecules and are attributed to small changes in localised mechanical stress, which are enhanced by SERRS. These influences are greatest for peaks due to the C-S functional group and the Full Width Half Maximum (FWHM) was found to be inversely proportional to protein concentration.
Journal of Fluorescence, 2008
Journal of Biomedical Optics, 2016
To facilitate regular assessment of the microcirculation in-vivo, non-invasive imaging techniques... more To facilitate regular assessment of the microcirculation in-vivo, non-invasive imaging techniques such as nailfold capillaroscopy are required in clinics. Recently a correlation mapping technique has been applied to Optical Coherence Tomography (OCT) which extends the capabilities of OCT to microcirculation morphology imaging. This technique, known as cmOCT has been shown to extract parameters such as capillary density and vessel diameter, key clinical markers associated with early changes in microvascular diseases. However, OCT has limited spatial resolution in both the transverse and depth directions. Here, we extend this correlation mapping technique to other microscopy modalities, including confocal microscopy and take advantage of the higher spatial resolution offered by these modalities. The technique is achieved as a processing step on microscopy images and does not require any modification to the microscope hardware. Results are presented which show that this correlation mapping microscopy technique can extend the capabilities of conventional microscopy to enable mapping of vascular networks in-vivo with high spatial resolution in both the transverse and depth directions.
We have studied the low-temperature (133À298 K) fluorescence emission of crude petroleum oils usi... more We have studied the low-temperature (133À298 K) fluorescence emission of crude petroleum oils using a combination of steady-state and time-resolved measurements. This was done, first, to see if we could generate linear correlations between the oil composition information and the fluorescence measurements and, second, to better understand how static and dynamic quenching affect fluorescence emission. It was observed that the fluorescence intensity and the lifetime of the crude oils increased rapidly with decreasing temperature down to the freezing point, and then, they either remained constant or, surprisingly, began to decrease slightly. These changes could not be correlated accurately with the compositional data available. However, despite the very large variations in sample composition, it was found that these lifetimeÀtemperature changes followed simple Arrhenius and Eyring behavior. For the cold liquid phase, an Arrhenius model enabled the calculation of an intrinsic lifetime, the magnitude of which was inversely related to the degree of static quenching. The low values of the calculated activation energies (4.6À 19.2 kJ mol À1 ) implied that, in the liquid phase, nonradiative decay was primarily diffusion based quenching. At the lowest temperatures, when all samples have solidified, the lifetime data followed Eyring like behavior, giving typical enthalpy and entropy values of À1 kJ mol À1 and from À67 to À93 J K À1 mol À1 , respectively. The Eyring model was used to describe the nonradiative decay mechanism arising from the vibrational coupling from the fluorophores to the surrounding matrix. This modeling of the temperature dependence of the fluorescence lifetime has provided a clearer, quantitative picture of the fluorescence quenching processes in crude petroleum oils.