Keywords: silver nanoparticles, point of care
Summary:The demand for quantitative Point of Care (PoC) testing is increasing, driven by the need to access results faster for improved patient safety, satisfaction and clinical outcomes across a variety of settings which cannot be achieved by existing systems. To meet these needs, AgPlus Diagnostics Limited (AgPlus) have developed a diagnostic platform technology that will deliver against the demanding market requirements of a true quantitative PoC product for use across a wide range of clinical applications. The AgPlus system uses our patented electrochemical immunoassay with silver nanoparticles as its detection system. The use of this signalling system has allowed us to achieve high assay sensitivity while maintaining small sample volumes. A further advantage of the chemistry is the low power consumption when compared to other detection methods allowing for the development of a battery powered, portable system. 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 Previously unknown was the fact that ammonium thiocyanate forms a charged monolayer around the silver nano-particle. This monolayer allows it to be migrated to the electrode on the assay chip, where it is simply converted into silver ions, letting a quantitative measurement be made. This method, developed by AgPlus, stops the need to use harsh corrosive chemicals for the generation of metal ions for the measurements which previous electroanalytical metallo-immunoassay required. Alongside the development of the assay system, AgPlus is developing a handheld reader. The reader is being developed to fully control the running of the assay and its analysis. Once the sample has been added to the assay cartridge and inserted into the reader, the reader takes over the running of the assay. This includes the actuation of the fluids for the wash step and the ammonium thiocyanate for the reduction of the silver nanoparticles. No user intervention is required until the assay has been completed, where all that is required is the removal of the assay cartridge from the reader for disposal. The technology, developed for OEM Business-to-Business solutions will deliver a client customised assay system for rapid diagnostics. The platform can be used across multiple applications and sectors, critically where faster diagnostic results will enable users to make decisions, with confidence, in minutes not hours or days.