Interferometric biosensor for the detection of proteins driven by electrophoresis Duilio Didona and Dr Ruchi Gupta University of Birmingham, United Kingdom One of the main biomedical issues is to be able to obtain an early diagnosis, so that patients can be treated promptly and effectively. For this reason, point-of-care devices have been developed to perform quick and accurate blood analysis. Unfortunately, current sensors can either detect low concentrations of analytes or perform a quick sample analysis, not both. The purpose of this project is to determine if it is possible to combine gel electrophoresis and interferometry to realise a biosensor capable of detecting rapidly proteins at low concentration, so that it can be used as a point- of-care device for the detection of procalcitonin. Using electrophoresis is advantageous because it is possible to concentrate the proteins, separate them from the other molecules and move them quickly. The advantage of using hydrogel is that the antibodies have a 3D matrix they can attach to. Both natural and synthetic hydrogels have been investigated, obtaining so far better results with the natural. The optical system is composed of a laser, a beam expander, a cylindrical lens, a Fresnel biprism, two mirrors and a camera. The laser beam, after being expanded, is split into two beams by the Fresnel biprism and the cylindrical lens. Then, the beams are reflected by a mirror towards the two channels of the chip. Finally, the beams are reflected again by another mirror toward the camera, which will record the interference pattern. During the measurement, a software calculates the phase difference between the two channels, which is related to the change in refractive index caused by the analytes. Since it is possible to see the interference pattern of the whole channels, the device can also be used as an imaging tool.
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