Abstract: Candidates for biological activity are screened in capsules, each capsule containing a candidate, a target (which may be a molecular species or a biological cell or multiple copies of such a species or cell), and an intelligent substance. The target is one with which a successful candidate will interact to evoke a particular response in the target, and the intelligent substance is one that undergoes a transformation as a result of the response, the transformation being detectable by observation of the capsule itself. The candidate and the target are isolated from each other in the capsule until a designated point in time thereby enabling the operator to control the time interval between exposure of the target to the candidate and the observation of the capsule to determine whether or not a successful interaction has occurred and the transformation has taken place.

Abstract: An assay for determining the presence of a threshold concentration of an analyte in a sample comprises first reacting the sample with an amount of anti-analyte selected to reduce the free analyte to a marginally detectable concentration. The sample is then contacted with anti-analyte immobilized on a test region or indicator zone on a solid phase, whereby the residual free analyte may be bound. The binding of free analyte to immobilized anti-analyte is detected by a variety of techniques to indicate the presence of the threshold concentration. By employing limited amounts of anti-analyte on the solid phase, the change between maximum binding of label and no binding of label will be responsive to very small changes in the analyte concentration originally present in the sample.

Abstract: A sample applicator for use in performing immunoassays comprises a tube defining an internal lumen and having a filter matrix at one end thereof. Sample is drawn into the applicator tube, either using a vacuum bulb or an automated assay device. The sample is filtered as it enters the tube, and is again filtered as it discharged from the tube in the opposite flow direction. By removing particulates from the liquid sample, assay performance can be greatly improved. The applicator may also comprise a reagent dispersed within a permeable matrix, which is useful for introducing reagent to a sample or other liquid assay component. As a liquid assay component is drawn into the applicator tube, the reagent is reconstituted by and mixed with the liquid, thereby reducing the number of steps required for the assay.