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Zafar H.,National University of Ireland | Enfield J.,National Biophotonics and Imaging Platform | O'Connell M.-L.,National Biophotonics and Imaging Platform | Ramsay B.,Dermatology Unit | And 3 more authors.
Skin Research and Technology | Year: 2014

Background/Purpose: Vascular abnormalities play an acute role in the pathogenesis of psoriasis. In order to characterize vascular involvement in psoriasis and its regular clinical assessment in vivo, non-invasive high speed imaging with high resolution and high sensitivity is needed. Methods: The correlation mapping optical coherence tomography (cmOCT) technique was used for in vivo microcirculation imaging of human forearm under normal and psoriatic conditions. The cmOCT technique developed by our group uses dense scanning OCT image acquisition and post-processing software based on correlation statistics. The frequency domain OCT system was used for imaging which acquires a 3D volume of 1024 × 1024 A-scans, each of 512 pixels deep in approximately 70 s. The cmOCT technique processes the resulting OCT volume within 116 s using a 7 × 7 kernel. Results: 3D structural and functional (microcirculation) maps of the healthy tissue and the psoriatic plaque were obtained using the cmOCT technique. The presented results indicate that cmOCT allows not only the identification of the microvessels, but also produces more detailed microvascular networks showing how the blood vessels relate to each other in healthy tissue and within the plaque. The microcirculation pattern within the plaque is totally different from the healthy tissue. The distinct changes are also observed in vessel density, tortuosity, and orientation. Conclusion: The cmOCT provides high sensitivity and imaging speed for in vivo microcirculation imaging within the human skin under normal and diseased conditions. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Source


Roy S.,National Biophotonics and Imaging Platform | Dixit C.K.,Dublin City University | Woolley R.,National Biophotonics and Imaging Platform | O'Kennedy R.,Dublin City University | McDonagh C.,National Biophotonics and Imaging Platform
Langmuir | Year: 2011

Fluorescence lifetime correlation spectroscopy (FLCS) is presented as a single-step label-free detection method for probing the amine silanization-driven spontaneous 3D self-assembly of freestanding gold nanoparticles (GNPs) in solution. Unlike the conventional methods of studying self-assembly, for example, UV-vis spectroscopy and electron microscopy, FLCS utilizes the intrinsic gold fluorescence. The significance of this approach is to amalgamate the measurement of optical and hydrodynamic size properties simultaneously to achieve a more coherent description of the self-assembly pathway. GNP self-assembly has two-stage kinetics. Electrostatic interaction drives the initial amine silanization, and this is followed by siloxane bond formation between hydrolyzed ethoxy groups of GNP-attached APTES, resulting in the formation of micrometer-sized superstructures. The self-assembly has resulted in a 5-fold increase in the fluorescence lifetime (FL), and the FLCS study has shown an 8- to 10-fold increase in the diffusion coefficient using the pure diffusion model. This result is consistent with the transmission electron microscopy (TEM) observation, which shows a few hundred fold increase in the diameter due to assembly formation by the GNPs. © 2011 American Chemical Society. Source


Roy S.,National Biophotonics and Imaging Platform | Dixit C.K.,Dublin City University | Woolley R.,National Biophotonics and Imaging Platform | MacCraith B.D.,National Biophotonics and Imaging Platform | And 2 more authors.
Langmuir | Year: 2010

This Article addresses the important issue of the characterization of surface functional groups for optical bioassay applications. We use a model system consisting of spherical dye-doped silica nanoparticles (NPs) that have been functionalized with amine groups whereby the encapsulated cyanine-based near-infrared dye fluorescence acts as a probe of the NP surface environment. This facilitates the identification of the optimum deposition parameters for the formation of a stable ordered amine monolayer and also elucidates the functionalization profile of the amine-silanization process. Specifically, we use a novel approach where the techniques of fluorescence correlation spectroscopy (FCS) and fluorescence lifetime measurement (FL) are used in conjunction with the more conventional analytical techniques of zeta potential measurement and Fourier transfer infrared spectroscopy (FTIR). The dynamics of the ordering of the amine layer in different stages of the reaction have been characterized by FTIR, FL, and FCS. The results indicate an optimum reaction time for the formation of a stable amine layer, which is optimized for further biomolecular conjugation, whereas extended reaction times lead to a disordered cross-linked layer. The results have been validated using an immunoglobulin (IgG) plate-based direct binding assay where the maximum number of IgG-conjugated aminated NPs were captured by immobilized anti-IgG antibodies for the NP sample corresponding to the optimized amine-silanization condition. Importantly, these results point to the potential of FCS and FL as useful analytical tools in diverse fields such as characterization of surface functionalization. © 2010 American Chemical Society. Source


Roy S.,National Biophotonics and Imaging Platform | Dixit C.K.,National Biophotonics and Imaging Platform | Manickam G.,Dublin City University | Daniels S.,Dublin City University | And 2 more authors.
Langmuir | Year: 2013

A fourth generation PAMAM dendrimer has been successfully employed for the development of a single step synthesis strategy for self-assembled Ag-Au nanohybrid structures. The surface plasmon resonance properties and the degree of self-assembly of the nanohybrid are strongly correlated with the stoichiometry of the metals which gives rise to enhanced plasmonic properties. The enhanced plasmonic response of the nanohybrids is modeled and is validated experimentally in a model HRP (horseradish peroxidise) bioassay carried out on an SPR-based biochip platform. © 2013 American Chemical Society. Source

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