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Lateral flow biosensors
In a lateral flow test, magnetic nanoparticles functionalized with particular antigens attach to biomolecular targets and flow through capillaries in a membrane substrate (Milipore). The membrane has test and control fringes where particular antibody probes have been immobilized. The strength of the fringe field at the test bars indicates the presence of the particular biomolecular targets in the initial solution. Two systems are being developed in collaboration with U. Zaragossa, In the first, the stripe is placed on a plastic wheel, it is brought in contact with the MR sensor surface, and by displacing the wheel over the sensor, the test fringe signals are measured. This device has been fabricated at INESC MN and is under test at U.Zaragossa. A second device under design consists of a stripe reader, similar to a tape head reader. Fig.8 shows a typical lateral flow assay, where ABs are immobilized on test and control sites, and the target biomolecule migrates through the membrane till it finds the immobilized probes. The grey fringes shown in the bottom left figure correspond to immobilized magnetic nanoparticles.
Fig.8 Schematics of a typical lateral flow assay. The bottom left shows the control and test fringes where magnetic nanoparticles are immobilized. A MR sensor then reads thje fringe field created by these labels.