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Title: An optical biosensor and immunoassay framework suitable for on-site measurement of progesterone concentration in bovine milk
Author: Ghadar, Arash
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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This PhD provides a novel design for a fluorescence-based biosensor and the associated immunoassay framework. It offers a solution for measuring progesterone concentration in bovine milk that can be used as an integral part of a dairy farm’s reproductive management, with a direct impact on the farm profitability. A cow needs to give birth in regular intervals in order to produce a healthy amount of milk. A high pregnancy rate requires an accurate estimate of the onset of oestrus to achieve an effective insemination and therefore a high conception rate. Progesterone concentration in bovine milk reaches a minimum at around 2 ng/ml, approximately 72 hours before oestrus, a characteristic that can be used to detect the onset of oestrus. The majority of methods currently employed for progesterone measurement require expensive laboratory-based instruments and time-consuming preparation stages. This thesis, however sets out the case for the design of a portable commercially-viable biosensor, capable of measuring progesterone concentration on-site at dairy farms. The proposed solution features a unique adaptive offset cancellation mechanism, which compensates for the effect of varying background LED light and provides a wide dynamic range. The design eliminates the need for the expensive optical components such as lens, collimator and dichroic mirror. Furthermore, the innovative design of the casing substantially reduces the effect of background light on the detector circuit, whilst improves the fluorescent excitation within the sample and subsequent detection by the sensor. This thesis also provides a novel framework for a competitive homogeneous immunoassay based on Fluorescence Resonance Energy Transfer (FRET). Three specific immunoassay procedures are proposed, offering a trade off on hardware cost versus running cost as well as procedural and algorithmic complexity. Following a thorough analysis of the hardware design and immunoassay framework and the optimisation of the key system parameters, a prototype biosensor was developed. Numerous experiments were carried out and the performance was verified against CLARIOstar spectrofluorometer. The outcome demonstrates the effectiveness of the immunoassay framework and the ability of the biosensor to measure fluorophore concentration with an accuracy of ±250 pM, which is suitable for detecting the onset of oestrus.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QP Physiology