Toward an Optofluidic gene Sensor based on Fluorescence Enhancement in a Hollow Bottle Microresonator

My thesis work was carried out at the Optoelectronic Research Centre (ORC) in the United Kingdom. [...]
In first chapter the widely used method for detection of nucleic acids strings, known as hybridization, is presented with the explanation of the basics of the nucleic acids biology.
The optical approach exploited in this work requires an understanding of the concept of fluorescence that is the physical effect that provides the signal and is explained in chapter 2.
Chapter 3 is dedicated to the state of the art in biosensing, illustrating basics, requirements and several possible approaches, focussing on optofluidic biosensors.
The state of the art specifically relevant for the optical resonator device used in this work is described in chapter 4 after summarizing its physics principle.
Materials exploited in this work came from many disciplines and are listed in chapter 5, in addition to the chemical methods employed for the research and the optical scheme used for measurements.
The experimental work is reported in chapter 6 where the functionalization of the device with the bioreceptor and the characterization of the performance of the transducer are described in detail.
The project, due to its multidisciplinary characteristic, was continued within the Inte-grated Photonic Devices Group that traditionally exploited mainly planar photonic de-vices, for various applications included diagnostics in medicine, but, more recently, also integrated microsphere resonators fabricated with fibre technologies. The project meets the demand of small integrated biological sensors which could eliminate the lengthy and hard laboratory work traditionally required to perform gene detection. For these devices, the biochemical functionalization of the device is the first aspect to consider, which con-fer to the optical device its specificity, i.e., the way to interact with biological entities. For optical methods the sensitivity and speed is considerably enhanced respect to elec-trochemical approaches; moreover, optical detection can be integrated with a capillary fabricated with fibre technology that provides the advantages of microfluidics. For bio-logical measurements, optics offers different approaches. In particular, label-free meth-ods are very interesting since do not require the use of any marker and achieve among the best sensitivity in biosensing. Unfortunately, the label-free technique was found not suitable for the fluidic device considered and it was necessary to consider the use of flu-orescent markers. A characterization of the device was carried out in order to verify the principle of optical transduction: it was aimed to the spatial and spectral visualization of the resonances by the excitation of specific fluorophores.