Julian Moger - Academia.edu (original) (raw)

Papers by Julian Moger

Optics in the Life Sciences, 2015

Journal of Physics D: Applied Physics, 2005

In this paper we investigate the effect of multiple scattering on Doppler optical coherence tomog... more In this paper we investigate the effect of multiple scattering on Doppler optical coherence tomography (DOCT) images of model blood vessels embedded in a medium with optical properties similar to those of the human dermis. Furthermore, we quantify the deviation of the acquired velocity profiles from that known to exist within a glass capillary at various depths within the scattering media. A flow phantom consisting of a glass tube containing whole blood flowing under laminar conditions submerged in a variable depth of Intralipid was used to simulate a blood vessel within the cutaneous microcirculation. DOCT images and velocity profiles of the tube acquired at various depths within the Intralipid are compared with those obtained from the same tube in a non-scattering medium with the same refractive index.

The Analyst, Jan 16, 2018

Vibrational spectroscopies, based on infrared absorption and/or Raman scattering provide a detail... more Vibrational spectroscopies, based on infrared absorption and/or Raman scattering provide a detailed fingerprint of a material, based on the chemical content. Diagnostic and prognostic tools based on these technologies have the potential to revolutionise our clinical systems leading to improved patient outcome, more efficient public services and significant economic savings. However, despite these strong drivers, there are many fundamental scientific and technological challenges which have limited the implementation of this technology in the clinical arena, although recent years have seen significant progress in addressing these challenges. This review examines (i) the state of the art of clinical applications of infrared absorption and Raman spectroscopy, and (ii) the outstanding challenges, and progress towards translation, highlighting specific examples in the areas of in vivo, ex vivo and in vitro applications. In addition, the requirements of instrumentation suitable for use in ...

Journal of Structural Biology, 2010

A network of circumferentially oriented collagen fibrils exists in the periphery of the human cor... more A network of circumferentially oriented collagen fibrils exists in the periphery of the human cornea, and is thought to be pivotal in maintaining corneal biomechanical stability and curvature. However, it is unknown whether or not this key structural arrangement predominates throughout the entire corneal thickness or exists as a discrete feature at a particular tissue depth; or if it incorporates any elastic fibres and how, with respect to tissue depth, the circumcorneal annulus integrates with the orthogonally arranged collagen of the central cornea. To address these issues we performed a three-dimensional investigation of fibrous collagen and elastin architecture in the peripheral and central human cornea using synchrotron X-ray scattering and non-linear microscopy. This showed that the network of collagen fibrils circumscribing the human cornea is located in the posterior one-third of the tissue and is interlaced with significant numbers of mature elastic fibres which mirror the alignment of the collagen. The orthogonal arrangement of collagen in the central cornea is also mainly restricted to the posterior stromal layers. This information will aid the development of corneal biomechanical models aimed at explaining how normal corneal curvature is sustained and further predicting the outcome of surgical procedures.

Phase-resolved Doppler optical coherence tomography is a recently reported technique for simultan... more Phase-resolved Doppler optical coherence tomography is a recently reported technique for simultaneously imaging tissue structure and blood with high velocity resolution. The optical set-up consists of a fibre-based Michelson interferometer with a 1300nm superluminescent diode in the source arm. The output power is 0.6mW with a bandwidth of 50nm. The reference arm contains a grating-based Fourier domain rapid-scanning delay line with an electro-optic phase modulator to provide a stable reference frequency (800kHz). Ten axial scans sampled, at 400Hz, from the same location are processed to generate structural and velocity data from the reconstructed phase information derived from a Hilbert transform. The sample arm probe focuses light from the fibre into the tissue, producing a beam spot of diameter approximately 20micrometers . The probe is mounted on a linear translation stage, which generates a lateral step of 10micrometers between groups of ten axial scans. The Doppler shift in each pixel is calculated from the average phase shift over the ten sequential scans at each location. The acquisition time for a 100x100 pixel image is approximately 5s. We demonstrate the systems ability to image in-vivo changes in skin perfusion, induced by standard non-invasive physiological techniques.

Optics Express, 2008

Metal oxide nanomaterials are being used for an increasing number of commercial applications, suc... more Metal oxide nanomaterials are being used for an increasing number of commercial applications, such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and as drug delivery vehicles. The effects of these nanoparticles on the physiology of animals and in the environment are largely unknown and their potential associated health risks are currently a topic of hot debate. Information regarding the entry route of nanoparticles into exposed organisms and their subsequent localization within tissues and cells in the body are essential for understanding their biological impact. However, there is currently no imaging modality available that can simultaneously image these nanoparticles and the surrounding tissues without disturbing the biological structure. Due to their large nonlinear optical susceptibilities, which are enhanced by two-photon electronic resonance, metal oxides are efficient sources of coherent anti-Stokes Raman Scattering (CARS). We show that CARS microscopy can provide localization of metal oxide nanoparticles within biological structures at the cellular level. Nanoparticles of 20 - 70 nm in size were imaged within the fish gill; a structure that is a primary site of pollutant uptake into fish from the aquatic environment.

Environmental Chemistry, 2010

Environmental context. The production and application of engineered nanoparticles is rapidly incr... more Environmental context. The production and application of engineered nanoparticles is rapidly increasing, and development of suitable models for screening nanoparticles for possible toxic effects is essential to protect aquatic organisms and support the sustainable development of the nanotechnology industry. Here, the suitability of isolated rainbow trout hepatocytes was assessed for high through-put toxicity screening of nanoparticles and for studying uptake of nanoparticles into cells.

Environmental Science & Technology, 2010

Environmental Pollution, 2010

This study explores the hypothesis that nano-TiO 2 and single walled nanotubes (SWNT) can cause s... more This study explores the hypothesis that nano-TiO 2 and single walled nanotubes (SWNT) can cause sublethal impacts to Arenicola marina exposed through natural sediments.

Optics Express, 2008

Metal oxide nanomaterials are being used for an increasing number of commercial applications, suc... more Metal oxide nanomaterials are being used for an increasing number of commercial applications, such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and as drug delivery vehicles. The effects of these nanoparticles on the physiology of animals and in the environment are largely unknown and their potential associated health risks are currently a topic of hot debate. Information regarding the entry route of nanoparticles into exposed organisms and their subsequent localization within tissues and cells in the body are essential for understanding their biological impact. However, there is currently no imaging modality available that can simultaneously image these nanoparticles and the surrounding tissues without disturbing the biological structure. Due to their large nonlinear optical susceptibilities, which are enhanced by two-photon electronic resonance, metal oxides are efficient sources of coherent anti-Stokes Raman Scattering (CARS). We show that CARS microscopy can provide localization of metal oxide nanoparticles within biological structures at the cellular level. Nanoparticles of 20 - 70 nm in size were imaged within the fish gill; a structure that is a primary site of pollutant uptake into fish from the aquatic environment.

We investigate the effect of multiple scattering upon Doppler optical coherence tomography images... more We investigate the effect of multiple scattering upon Doppler optical coherence tomography images of model blood vessels immersed in a fluuid with similar optical properties to those of the human dermis. Furthermore, we quantify the deviation of the acquired velocity profiles from that known to exist within the glass capillary at various depths within the scattering media. A flow phantom consisting of a glass tube containing whole blood flowing under laminar conditions submerged in a variable depth of Intralipid was used to simulate a blood vessel within the cutaneous microcirculation. Doppler optical coherence tomography images and velocity profiles of the tube acquired at various depths within the Intralipid are compared to those obtained from the same tube in a non-scattering media with the same refractive index.

Surface-enhanced Raman scattering (SERS) has received a great deal interest as an analytical tool... more Surface-enhanced Raman scattering (SERS) has received a great deal interest as an analytical tool due to its potential for obtaining Raman signals from single molecules. Many methods for preparing SERS-active substrate have been reported. These range from nano-particle based methods, which lack reproducibility, to highly reproducible nano-arrays requiring time consuming and costly preparation. We show that highly reproducible SERS can be achieved by applying a metallic coating to the brightly coloured regions of the graphium weiskei butterfly wing. Electron microscopy reveals the wing exhibit nanostructures with comparable dimensions to the roughness scale of SERS substrates. SERS measurements performed on wings coated with 60 nm of silver display enhancement factors of approximately 10 7 with no apparent background contribution from the wing. To demonstrate effectiveness and reproducibility the substrate is coated with a monoclonal antibody.

Journal of Biomedical Optics, 2004

Blood, being a suspension of deformable red cells suspended in plasma, displays flow dynamics con... more Blood, being a suspension of deformable red cells suspended in plasma, displays flow dynamics considerably more complicated than those of an ideal Newtonian fluid. Flow dynamics in blood capillaries of a few hundred micrometers in diameter are investigated using Doppler optical coherence tomography (DOCT) and Doppler amplitude optical coherence tomography (DAOCT), a novel extension of DOCT. Velocity profiles and concentration distributions of normal and rigidified in vitro red blood cell suspensions are shown to vary as functions of mean flow velocity, cell concentration, and cell rigidity. Deviation from the parabolic velocity profile expected for Pouseille flow is observed for both rigid and normal cells at low flow rates. Axial red cell migration both toward and away from the tube axis is observed for both rigid and normal cells as a function of flow velocity. Good agreement is found between our measurements, and theoretical expectations.

Journal of Anatomy, 2009

A combination of two-photon fluorescence (TPF), second harmonic generation (SHG) and coherent ant... more A combination of two-photon fluorescence (TPF), second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) imaging has been used to investigate the elastin fibre network in healthy equine articular cartilage from the metacarpophalangeal joint. The elastin fibres were identified using their intrinsic two-photon fluorescence and immuno-staining was used to confirm the identity of these fibres. SHG was used to reveal the collagen matrix and the collagen fibre orientations were determined from their SHG polarization sensitivity, while CARS was used to clearly delineate the cell boundaries. Extensive elastin fibre networks were found in all the joint regions investigated. The elastin was found predominantly in the superficial zone (upper 50 μm) and was aligned parallel to the articular surface. Elastin was also detected in the pericellular matrix surrounding the superficial chondrocytes; however, individual fibres could not be resolved in this region. Variations in the density and organization of the fibres were observed in different regions on the joint surface.

Biochimica Et Biophysica Acta-general Subjects, 2007

We investigate the feasibility of colloid-based surface enhanced Raman scattering (SERS) as a hig... more We investigate the feasibility of colloid-based surface enhanced Raman scattering (SERS) as a highly sensitive technique for detecting peptide phosphorylation at serine and tyrosine residues. Using the recently reported drop-coating deposition Raman method we validate our SERS spectra against normal Raman spectra that would otherwise be unobtainable at such low concentrations. Compared with existing techniques for quantifying peptide phosphorylation, such as high-performance liquid chromatography (HPLC), the short scanning and processing time associated with SERS makes it an attractive alternative for near-real-time measurement at sub micro-molar concentrations. Following pre-processing by Savistky-Golay second derivative (SGSD), the degree of phosphorylation of synthetic peptides is determined using multivariate spectral classification, interval partial least squares (iPLS). Furthermore, our results show that the technique is robust to interference from complex proteins and other phosphorylated compounds present at concentrations typically found in a screening assay.

We report on the use of phase-resolved DOCT to measure oscillatory flow in a rigid glass capillar... more We report on the use of phase-resolved DOCT to measure oscillatory flow in a rigid glass capillary. Experimental measurements are obtained in which a sinusoidal pressure gradient generates a sinusoidal varying flow of a scattering liquid (Intralipid-20%) in a 660 micron i.d. glass tube. Dynamic flow profiles are measured and compared with the analytical theory due to Womersley. Reasonable agreement is found for one half of the flow profile (-ve velocities) but the agreement is less good for the +ve velocities. Possible reasons for the discrepancy are discussed. The study indicates the usefulness of DOCT for studying fluid flow dynamics.

Flow dynamics in blood vessels of a few hundred microns in diameter were investigated using Doppl... more Flow dynamics in blood vessels of a few hundred microns in diameter were investigated using Doppler optical coherence tomography (DOCT) and Doppler Amplitude optical coherence tomography (DAOCT), a novel extension of DOCT. The motivation behind this work is discussed, followed by a brief explanation of the theory underlying the motion of blood cells in small conduits and blood vessels. Preliminary results are presented and compared to the predictions expected from theory. All significant findings are analysed along with their importance to microvascular research.

Journal of Biomedical Optics, 2008

Second harmonic generation (SHG) and two-photon fluorescence (TPF) microscopy is used to image th... more Second harmonic generation (SHG) and two-photon fluorescence (TPF) microscopy is used to image the intercellular and pericellular matrix in normal and degenerate equine articular cartilage. The polarization sensitivity of SHG can be used directly to determine fiber orientation in the superficial 10 to 20 microm of tissue, and images of the ratio of intensities taken with two orthogonal polarization states reveal small scale variations in the collagen fiber organization that have not previously been reported. The signal from greater depths is influenced by the birefringence and biattenuance of the overlying tissue. An assessment of these effects is developed, based on the analysis of changes in TPF polarization with depth, and the approach is validated in tendon where composition is independent of depth. The analysis places an upper bound on the biattenuance of tendon of 2.65 x 10(-4). Normal cartilage reveals a consistent pattern of variation in fibril orientation with depth. In lesions, the pattern is severely disrupted and there are changes in the pericellular matrix, even at the periphery where the tissue appears microscopically normal. Quantification of polarization sensitivity changes with depth in cartilage will require detailed numerical models, but in the meantime, multiphoton microscopy provides sensitive indications of matrix changes in cartilage degeneration.

We investigate the effect of multiple scattering upon Doppler optical coherence tomography images... more We investigate the effect of multiple scattering upon Doppler optical coherence tomography images of model blood vessels immersed in a fluuid with similar optical properties to those of the human dermis. Furthermore, we quantify the deviation of the acquired velocity profiles from that known to exist within the glass capillary at various depths within the scattering media. A flow phantom consisting of a glass tube containing whole blood flowing under laminar conditions submerged in a variable depth of Intralipid was used to simulate a blood vessel within the cutaneous microcirculation. Doppler optical coherence tomography images and velocity profiles of the tube acquired at various depths within the Intralipid are compared to those obtained from the same tube in a non-scattering media with the same refractive index.

Journal of Anatomy, 2010

This study employed nonlinear microscopy on fresh, unstained and unfixed collecting lymphatic ves... more This study employed nonlinear microscopy on fresh, unstained and unfixed collecting lymphatic vessels to determine the wall structure and its relationships to the mechanical properties of the tissue. Fresh bovine mesenteric collecting lymphatic vessels were mounted in a vessel bath and imaged under different luminal pressures (0–30 cmH2O pressure head), and longitudinal tensions. The entire wall thickness was imaged, using two-photon fluorescence to visualize elastin, second harmonic generation to image the collagen, and coherent anti-Stokes Raman scattering to image the cell membrane. The adventitial fat cells were coupled to the wall within the elastin-rich network of fibres. The medial smooth muscle cells were too densely packed to resolve the boundaries of individual cells in en face images, but in tissue sections their appearance was consistent with electron microscopic data. Two distinct populations of collagen fibre were revealed. Large fibre (15–25 μm diameter) bundles were present in the inner media and small fibres (2–5 μm diameter) were distributed throughout the wall. The responses to longitudinal tension and luminal pressure indicated that the larger fibres resist the longitudinal strain and the smaller oppose pressure forces. Individual elastin fibres were of uniform thickness (1–3 μm) and interwove amongst themselves and between the collagen fibres. The network was probably too sparse directly to support mechanical loads and we speculate that its main function is to maintain the organization of collagen bundles during recovery from contraction.

Optics in the Life Sciences, 2015

Journal of Physics D: Applied Physics, 2005

In this paper we investigate the effect of multiple scattering on Doppler optical coherence tomog... more In this paper we investigate the effect of multiple scattering on Doppler optical coherence tomography (DOCT) images of model blood vessels embedded in a medium with optical properties similar to those of the human dermis. Furthermore, we quantify the deviation of the acquired velocity profiles from that known to exist within a glass capillary at various depths within the scattering media. A flow phantom consisting of a glass tube containing whole blood flowing under laminar conditions submerged in a variable depth of Intralipid was used to simulate a blood vessel within the cutaneous microcirculation. DOCT images and velocity profiles of the tube acquired at various depths within the Intralipid are compared with those obtained from the same tube in a non-scattering medium with the same refractive index.

The Analyst, Jan 16, 2018

Vibrational spectroscopies, based on infrared absorption and/or Raman scattering provide a detail... more Vibrational spectroscopies, based on infrared absorption and/or Raman scattering provide a detailed fingerprint of a material, based on the chemical content. Diagnostic and prognostic tools based on these technologies have the potential to revolutionise our clinical systems leading to improved patient outcome, more efficient public services and significant economic savings. However, despite these strong drivers, there are many fundamental scientific and technological challenges which have limited the implementation of this technology in the clinical arena, although recent years have seen significant progress in addressing these challenges. This review examines (i) the state of the art of clinical applications of infrared absorption and Raman spectroscopy, and (ii) the outstanding challenges, and progress towards translation, highlighting specific examples in the areas of in vivo, ex vivo and in vitro applications. In addition, the requirements of instrumentation suitable for use in ...

Journal of Structural Biology, 2010

A network of circumferentially oriented collagen fibrils exists in the periphery of the human cor... more A network of circumferentially oriented collagen fibrils exists in the periphery of the human cornea, and is thought to be pivotal in maintaining corneal biomechanical stability and curvature. However, it is unknown whether or not this key structural arrangement predominates throughout the entire corneal thickness or exists as a discrete feature at a particular tissue depth; or if it incorporates any elastic fibres and how, with respect to tissue depth, the circumcorneal annulus integrates with the orthogonally arranged collagen of the central cornea. To address these issues we performed a three-dimensional investigation of fibrous collagen and elastin architecture in the peripheral and central human cornea using synchrotron X-ray scattering and non-linear microscopy. This showed that the network of collagen fibrils circumscribing the human cornea is located in the posterior one-third of the tissue and is interlaced with significant numbers of mature elastic fibres which mirror the alignment of the collagen. The orthogonal arrangement of collagen in the central cornea is also mainly restricted to the posterior stromal layers. This information will aid the development of corneal biomechanical models aimed at explaining how normal corneal curvature is sustained and further predicting the outcome of surgical procedures.

Phase-resolved Doppler optical coherence tomography is a recently reported technique for simultan... more Phase-resolved Doppler optical coherence tomography is a recently reported technique for simultaneously imaging tissue structure and blood with high velocity resolution. The optical set-up consists of a fibre-based Michelson interferometer with a 1300nm superluminescent diode in the source arm. The output power is 0.6mW with a bandwidth of 50nm. The reference arm contains a grating-based Fourier domain rapid-scanning delay line with an electro-optic phase modulator to provide a stable reference frequency (800kHz). Ten axial scans sampled, at 400Hz, from the same location are processed to generate structural and velocity data from the reconstructed phase information derived from a Hilbert transform. The sample arm probe focuses light from the fibre into the tissue, producing a beam spot of diameter approximately 20micrometers . The probe is mounted on a linear translation stage, which generates a lateral step of 10micrometers between groups of ten axial scans. The Doppler shift in each pixel is calculated from the average phase shift over the ten sequential scans at each location. The acquisition time for a 100x100 pixel image is approximately 5s. We demonstrate the systems ability to image in-vivo changes in skin perfusion, induced by standard non-invasive physiological techniques.

Optics Express, 2008

Metal oxide nanomaterials are being used for an increasing number of commercial applications, suc... more Metal oxide nanomaterials are being used for an increasing number of commercial applications, such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and as drug delivery vehicles. The effects of these nanoparticles on the physiology of animals and in the environment are largely unknown and their potential associated health risks are currently a topic of hot debate. Information regarding the entry route of nanoparticles into exposed organisms and their subsequent localization within tissues and cells in the body are essential for understanding their biological impact. However, there is currently no imaging modality available that can simultaneously image these nanoparticles and the surrounding tissues without disturbing the biological structure. Due to their large nonlinear optical susceptibilities, which are enhanced by two-photon electronic resonance, metal oxides are efficient sources of coherent anti-Stokes Raman Scattering (CARS). We show that CARS microscopy can provide localization of metal oxide nanoparticles within biological structures at the cellular level. Nanoparticles of 20 - 70 nm in size were imaged within the fish gill; a structure that is a primary site of pollutant uptake into fish from the aquatic environment.

Environmental Chemistry, 2010

Environmental context. The production and application of engineered nanoparticles is rapidly incr... more Environmental context. The production and application of engineered nanoparticles is rapidly increasing, and development of suitable models for screening nanoparticles for possible toxic effects is essential to protect aquatic organisms and support the sustainable development of the nanotechnology industry. Here, the suitability of isolated rainbow trout hepatocytes was assessed for high through-put toxicity screening of nanoparticles and for studying uptake of nanoparticles into cells.

Environmental Science & Technology, 2010

Environmental Pollution, 2010

This study explores the hypothesis that nano-TiO 2 and single walled nanotubes (SWNT) can cause s... more This study explores the hypothesis that nano-TiO 2 and single walled nanotubes (SWNT) can cause sublethal impacts to Arenicola marina exposed through natural sediments.

Optics Express, 2008

Metal oxide nanomaterials are being used for an increasing number of commercial applications, suc... more Metal oxide nanomaterials are being used for an increasing number of commercial applications, such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and as drug delivery vehicles. The effects of these nanoparticles on the physiology of animals and in the environment are largely unknown and their potential associated health risks are currently a topic of hot debate. Information regarding the entry route of nanoparticles into exposed organisms and their subsequent localization within tissues and cells in the body are essential for understanding their biological impact. However, there is currently no imaging modality available that can simultaneously image these nanoparticles and the surrounding tissues without disturbing the biological structure. Due to their large nonlinear optical susceptibilities, which are enhanced by two-photon electronic resonance, metal oxides are efficient sources of coherent anti-Stokes Raman Scattering (CARS). We show that CARS microscopy can provide localization of metal oxide nanoparticles within biological structures at the cellular level. Nanoparticles of 20 - 70 nm in size were imaged within the fish gill; a structure that is a primary site of pollutant uptake into fish from the aquatic environment.

We investigate the effect of multiple scattering upon Doppler optical coherence tomography images... more We investigate the effect of multiple scattering upon Doppler optical coherence tomography images of model blood vessels immersed in a fluuid with similar optical properties to those of the human dermis. Furthermore, we quantify the deviation of the acquired velocity profiles from that known to exist within the glass capillary at various depths within the scattering media. A flow phantom consisting of a glass tube containing whole blood flowing under laminar conditions submerged in a variable depth of Intralipid was used to simulate a blood vessel within the cutaneous microcirculation. Doppler optical coherence tomography images and velocity profiles of the tube acquired at various depths within the Intralipid are compared to those obtained from the same tube in a non-scattering media with the same refractive index.

Surface-enhanced Raman scattering (SERS) has received a great deal interest as an analytical tool... more Surface-enhanced Raman scattering (SERS) has received a great deal interest as an analytical tool due to its potential for obtaining Raman signals from single molecules. Many methods for preparing SERS-active substrate have been reported. These range from nano-particle based methods, which lack reproducibility, to highly reproducible nano-arrays requiring time consuming and costly preparation. We show that highly reproducible SERS can be achieved by applying a metallic coating to the brightly coloured regions of the graphium weiskei butterfly wing. Electron microscopy reveals the wing exhibit nanostructures with comparable dimensions to the roughness scale of SERS substrates. SERS measurements performed on wings coated with 60 nm of silver display enhancement factors of approximately 10 7 with no apparent background contribution from the wing. To demonstrate effectiveness and reproducibility the substrate is coated with a monoclonal antibody.

Journal of Biomedical Optics, 2004

Blood, being a suspension of deformable red cells suspended in plasma, displays flow dynamics con... more Blood, being a suspension of deformable red cells suspended in plasma, displays flow dynamics considerably more complicated than those of an ideal Newtonian fluid. Flow dynamics in blood capillaries of a few hundred micrometers in diameter are investigated using Doppler optical coherence tomography (DOCT) and Doppler amplitude optical coherence tomography (DAOCT), a novel extension of DOCT. Velocity profiles and concentration distributions of normal and rigidified in vitro red blood cell suspensions are shown to vary as functions of mean flow velocity, cell concentration, and cell rigidity. Deviation from the parabolic velocity profile expected for Pouseille flow is observed for both rigid and normal cells at low flow rates. Axial red cell migration both toward and away from the tube axis is observed for both rigid and normal cells as a function of flow velocity. Good agreement is found between our measurements, and theoretical expectations.

Journal of Anatomy, 2009

A combination of two-photon fluorescence (TPF), second harmonic generation (SHG) and coherent ant... more A combination of two-photon fluorescence (TPF), second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) imaging has been used to investigate the elastin fibre network in healthy equine articular cartilage from the metacarpophalangeal joint. The elastin fibres were identified using their intrinsic two-photon fluorescence and immuno-staining was used to confirm the identity of these fibres. SHG was used to reveal the collagen matrix and the collagen fibre orientations were determined from their SHG polarization sensitivity, while CARS was used to clearly delineate the cell boundaries. Extensive elastin fibre networks were found in all the joint regions investigated. The elastin was found predominantly in the superficial zone (upper 50 μm) and was aligned parallel to the articular surface. Elastin was also detected in the pericellular matrix surrounding the superficial chondrocytes; however, individual fibres could not be resolved in this region. Variations in the density and organization of the fibres were observed in different regions on the joint surface.

Biochimica Et Biophysica Acta-general Subjects, 2007

We investigate the feasibility of colloid-based surface enhanced Raman scattering (SERS) as a hig... more We investigate the feasibility of colloid-based surface enhanced Raman scattering (SERS) as a highly sensitive technique for detecting peptide phosphorylation at serine and tyrosine residues. Using the recently reported drop-coating deposition Raman method we validate our SERS spectra against normal Raman spectra that would otherwise be unobtainable at such low concentrations. Compared with existing techniques for quantifying peptide phosphorylation, such as high-performance liquid chromatography (HPLC), the short scanning and processing time associated with SERS makes it an attractive alternative for near-real-time measurement at sub micro-molar concentrations. Following pre-processing by Savistky-Golay second derivative (SGSD), the degree of phosphorylation of synthetic peptides is determined using multivariate spectral classification, interval partial least squares (iPLS). Furthermore, our results show that the technique is robust to interference from complex proteins and other phosphorylated compounds present at concentrations typically found in a screening assay.

We report on the use of phase-resolved DOCT to measure oscillatory flow in a rigid glass capillar... more We report on the use of phase-resolved DOCT to measure oscillatory flow in a rigid glass capillary. Experimental measurements are obtained in which a sinusoidal pressure gradient generates a sinusoidal varying flow of a scattering liquid (Intralipid-20%) in a 660 micron i.d. glass tube. Dynamic flow profiles are measured and compared with the analytical theory due to Womersley. Reasonable agreement is found for one half of the flow profile (-ve velocities) but the agreement is less good for the +ve velocities. Possible reasons for the discrepancy are discussed. The study indicates the usefulness of DOCT for studying fluid flow dynamics.

Flow dynamics in blood vessels of a few hundred microns in diameter were investigated using Doppl... more Flow dynamics in blood vessels of a few hundred microns in diameter were investigated using Doppler optical coherence tomography (DOCT) and Doppler Amplitude optical coherence tomography (DAOCT), a novel extension of DOCT. The motivation behind this work is discussed, followed by a brief explanation of the theory underlying the motion of blood cells in small conduits and blood vessels. Preliminary results are presented and compared to the predictions expected from theory. All significant findings are analysed along with their importance to microvascular research.

Journal of Biomedical Optics, 2008

Second harmonic generation (SHG) and two-photon fluorescence (TPF) microscopy is used to image th... more Second harmonic generation (SHG) and two-photon fluorescence (TPF) microscopy is used to image the intercellular and pericellular matrix in normal and degenerate equine articular cartilage. The polarization sensitivity of SHG can be used directly to determine fiber orientation in the superficial 10 to 20 microm of tissue, and images of the ratio of intensities taken with two orthogonal polarization states reveal small scale variations in the collagen fiber organization that have not previously been reported. The signal from greater depths is influenced by the birefringence and biattenuance of the overlying tissue. An assessment of these effects is developed, based on the analysis of changes in TPF polarization with depth, and the approach is validated in tendon where composition is independent of depth. The analysis places an upper bound on the biattenuance of tendon of 2.65 x 10(-4). Normal cartilage reveals a consistent pattern of variation in fibril orientation with depth. In lesions, the pattern is severely disrupted and there are changes in the pericellular matrix, even at the periphery where the tissue appears microscopically normal. Quantification of polarization sensitivity changes with depth in cartilage will require detailed numerical models, but in the meantime, multiphoton microscopy provides sensitive indications of matrix changes in cartilage degeneration.

We investigate the effect of multiple scattering upon Doppler optical coherence tomography images... more We investigate the effect of multiple scattering upon Doppler optical coherence tomography images of model blood vessels immersed in a fluuid with similar optical properties to those of the human dermis. Furthermore, we quantify the deviation of the acquired velocity profiles from that known to exist within the glass capillary at various depths within the scattering media. A flow phantom consisting of a glass tube containing whole blood flowing under laminar conditions submerged in a variable depth of Intralipid was used to simulate a blood vessel within the cutaneous microcirculation. Doppler optical coherence tomography images and velocity profiles of the tube acquired at various depths within the Intralipid are compared to those obtained from the same tube in a non-scattering media with the same refractive index.

Journal of Anatomy, 2010

This study employed nonlinear microscopy on fresh, unstained and unfixed collecting lymphatic ves... more This study employed nonlinear microscopy on fresh, unstained and unfixed collecting lymphatic vessels to determine the wall structure and its relationships to the mechanical properties of the tissue. Fresh bovine mesenteric collecting lymphatic vessels were mounted in a vessel bath and imaged under different luminal pressures (0–30 cmH2O pressure head), and longitudinal tensions. The entire wall thickness was imaged, using two-photon fluorescence to visualize elastin, second harmonic generation to image the collagen, and coherent anti-Stokes Raman scattering to image the cell membrane. The adventitial fat cells were coupled to the wall within the elastin-rich network of fibres. The medial smooth muscle cells were too densely packed to resolve the boundaries of individual cells in en face images, but in tissue sections their appearance was consistent with electron microscopic data. Two distinct populations of collagen fibre were revealed. Large fibre (15–25 μm diameter) bundles were present in the inner media and small fibres (2–5 μm diameter) were distributed throughout the wall. The responses to longitudinal tension and luminal pressure indicated that the larger fibres resist the longitudinal strain and the smaller oppose pressure forces. Individual elastin fibres were of uniform thickness (1–3 μm) and interwove amongst themselves and between the collagen fibres. The network was probably too sparse directly to support mechanical loads and we speculate that its main function is to maintain the organization of collagen bundles during recovery from contraction.