At the core of the AgPlus technology are the reagents for the electrochemical immunoassay. The assay chemistry utilises silver nano-particles as its signalling system. The use of silver nano-particles as the signalling system brings greater benefit as detection limits are much improved while sample volumes required for analysis are reduced. The analyte capture method is based on an “immune complex” being formed in exactly the same manner as in any immunoassay. These reduced sample volumes alongside the improved detection limits has allowed for easier miniaturisation of the system, while giving fully quantitative sample analysis. It is this basic feature that makes the AgPlus technology so universally adaptable.
The assay uses silver nanoparticles as the signalling method to quantify the reactions. The measurement system used is based on anodic stripping voltammetry, which gives the reduced sample volume requirements while increasing assay sensitivity over other measurement methods.
A simple graphical overview of the electroanalytical process in measuring the silver nano-particle. The silver nano-particles form a charged aggregate due to the presence of ammonium thiocyanate. This is attracted to the electrode under a positive potential. The silver nano-particle at the electrode is converted to silver ions. The silver ions are measured electro-analytically giving rise to a measurable peak, the area of the peak is proportional to the concentration of molecule being measured
Magnetic beads and silver nanoparticles are coated with a monoclonal (or polyclonal) antibody against the target analyte. The sample is mixed with the antibody-coated particles and incubated during which time complexes form. After incubation magnets are activated in the test strip that pulls the complexes formed away from the reaction chamber and the unwanted materials within the incubation chamber to the measurement zone. Once in the measurement area, the silver nanoparticles are cleaved, drawn down to the sensor and measured. The amount of silver particles is directly proportional to the amount of analyte in the sample.