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Platelets are central in maintaining normal haemostasis and are responsible for the cessation of blood loss following vascular injury. Platelet adhesion, leading to thrombus formation, involves rapid and distinct morphological changes culminating in cell aggregation. Rapid and highly specific platelet diagnostic tests are currently being developed to enable monitoring of drug response in patients with cardiovascular diseases. For a diagnostic device to be effective it needs to be rapid and simple, requiring minimal user interaction and providing results with minimal delay. This study describes the development of a rapid, label free platform for assay platelet function and demonstrates its use to monitor the influence of anti-thrombotic drugs. A rapid, single-step cell purification surface immobilises platelets from whole blood onto a protein array at specific locations used to define the assay site. Morphological changes and cell aggregation properties of activated platelets are exploited and combined within a label free, rapid, dye displacement chamber to determine cell morphology. Stimulation-dependent changes in cell morphology are described using both high resolution AFM imaging and a dye displacement platform. [ABSTRACT FROM AUTHOR]

Critical limitation of nanoparticles (NP) is their aggregation after functionalisation and antibody cross-linking. We analysed the cause of this aggregation with respect to functionalities (carboxyls and amines) on the NP surface. We have devised a low cost novel method to reduce such aggregations during protein cross-linking and validated it by probing the platelet surface with platelet surface-specific anti-CD41 antibody conjugated NPs.

This article describes the synthesis and characterisation of fluorescent composite nanoparticles consisting of a silica core and a dextran shell. The silica core contains a rhodamine-based reference dye, which allows ratiometric measurements and the dextran shell is labelled with the Ca(2+)-sensitive dye Fluo-4. The nanoparticles have an average hydrodynamic diameter of 95 nm, good colloidal stability and show a 2.9-fold increase in fluorescence intensity upon binding to Ca(2+) ions. The apparent dissociation constant of K'(d) ≈ 520 nM is well suited for measurements in the physiological range.

This study focuses on the optimisation and characterisation of novel, ORganically MOdified SILicate (ORMOSIL)-based, hybrid sensor films for use in the detection of O(2) on a breath-by-breath basis in human health monitoring applications. The sensing principle is based on the luminescence quenching of the O(2)-sensitive ruthenium complex [Ru(ii)-tris(4,7-diphenyl-1,10-phenanthroline)], 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 O(2), 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 these films. Key parameters to be optimised include the O(2) sensitivity of the film and the film polarity, i.e. the degree of hydrophobicity. These parameters are directly linked to the precursors used. In this study a n-propyltriethoxysilane-derived O(2) sensor platform was selected as the optimum material for in-breath O(2) analysis due to its short response time, negligible humidity interference and suitable O(2) sensitivity in the relevant range in addition to its compatibility with a single-point calibration strategy.

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.

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.