Description

The system composes of two parts:wet chemical reagents in the assays vial where the immunoreactions take place, and an analytical instrument, the VetReader, for quantification and measuring. The reagent is a two-site heterogeneous immunoassay, with a solid phase consisting of silica microparticles coated with target-specific antibodies. This is used as the solid phase. See figure 1.

The liquid phase consists of a sample buffer with magnetic nanoparticles which has also been coated with target-specific antibodies. These magnetic particles are colloidal, which means that they are small enough to stay in the solution, thus they do not sediment. The magnetic particles are used as the detector. See figure 2.

When the sample containing the target biological substance, i.e. the "marker", is placed into the reagent vial and the contents are mixed, the targeted marker will be captured by the target-specific antibodies on the silica surface. Target-specific antibodies on the magnetic nanoparticles will detect the marker bound to the silica surfaces in a sandwich-binding format. An immune-complex is formed. See figure 3.

The reagent vial is placed in the LifeAssays® VetReader and the instrument waits for the reaction to be completed before measuring the test result. During this time, the larger and heavier silica particles will sediment through normal gravity to the bottom of the reagent vial, forming a solid phase pellet. This pellet will now consist of both silica particles and a immuno complex of silica-coated-magnetic particles. The pellet will contain magnetic particles “fished” out from the fluid and will possess magnetic properties. See figure 4.

These magnetic properties are measured quantitatively with the internal coil in the LifeAssays® VetReader detecting the inductance. The change in inductance is proportional to the amount of magnetic material present in the pellet, and in turn shows how much of the selected marker that has been bound in the silica-coated-magnetic particle complex.

The internal coil measures the inductance 5 times by pushing the reagents vial in and out of the instrument,creating a “zero” value to use as a comparison each time the vial is lifted out of the instrument. An average raw signal value is created and sent to the “one computer chip” where the calculation takes place. The chip contains all analytic specific data and the self-executable calculation algorithm to calculate the test result in mg/L and displayed on the LifeAssays^® VetReader.