The fluorescent capillary fill device

Abstract

The fluorescent capillary fill device (FCFD) is an indirect optical immunosensor which consists of two sheets of glass held apart by a gap of capillary dimensions. Within the device are all the reagents needed to complete the assay, at least one of which is fluorescently labelled. Once the sample has entered the device, an immune complex, including an amount of the fluorophore label, rapidly forms on one of the surface of the device. Exploitation of the evanescent optical properties of the glass sheet used to fabricate the device enables the fluorophore bound immunologically to be discriminated from that which remains free (unbound) within the device. This allows the assay to be performed without the need for a wash and/or separation step. Both competitive and immunometric assays can be performed within the FCFD and the device will operate with a variety of untreated sample types (e.g., whole blood, serum, plasma, urine, saliva). A major technical challenge facing the development of immunosensors, the need to incorporate a reference/calibration system into the sensor, has been tackled and a reference system incorporated into the FCFD. The FCFD requires only simple instrumentation to interrogate bound fluorescence and, as its fabrication is based upon that of liquid-crystal displays, there is the possibility of developing a high-volume low-cost manufacturing process for its production. These factors, along with the ease of use of the device and the ability to incorporate a referencing system into it, result in the FCFD being an ideal immunosensor for decentralized testing.