The binding assay device of the present invention provides a removable cassette with an array of parallel channels for receiving multiple samples for assay. The cassette generally comprises a substantially planar cassette base with open channels formed in its bottom surface and a pair of channel extensions extending from its top surface which contain closed channels corresponding to and in fluid communication with open channels. The closed channels are further provided with openings at their termini for introduction of test samples into the cassette. In an assembled device, the cassette is disposed between a base plate and a slotted cover plate adapted for receipt of the channel extensions of the cassette. A resilient cushioning pad placed between the cassette base and base plate improves interchannel sealing and reduces the volume of the base channels and samples needed. A removable manifold adapted for sealing engagement with a channel extension and in fluid communication with the channels of the cassette facilitates simultaneous flushing of the channels.
In assaying for a analyte, a membrane on which binding member specific for the analyte is immobilized is placed between the resilient pad and the open channelled bottom surface of the cassette base. After the plates have been fastened together to secure the membrane in place under the cassette, the channels of the cassette are filled with appropriate volumes of test samples and assay reagents under conditions allowing binding and/or signaling events to occur. The channels are then flushed to rinse away unbound materials. Additional reagents, indicators, or binding members can also be introduced into the channels to provide a detectable signal.