University of California, Davis Department of Mechanical and Aeronautical Engineering Professor Dosi Dosev, Vishal Talwar, Mikaela Nichkova and Ian Kennedy developed a microchannel-magneto-immunoassay. A single microchannel is combined with external electromagnets for performing a fast immunoassay within a very small volume. Magnetic/luminescent Europium nanoparticles serve as carriers for the antibodies and as internal luminescent standard.
According to U.S. Patent Application 20090227044, the immunoreaction is accelerated by applying alternating magnetic field by means of the external electromagnets, thus inducing oscillation of the particles and achieving better diffusion during the incubation steps. Using the electromagnets the particles are held into the channel for washing and luminescence detection steps. The luminescence of the particles serves as an internal calibration for the assay and helps to avoid experimental error from particle loss.
An immunoassay is a biochemical test that measures the concentration of a substance in a biological liquid, typically serum or urine, using the reaction of an antibody or antibodies to its antigen. The assay takes advantage of the specific binding of an antibody to its antigen. Monoclonal antibodies are often used as they only usually bind to one site of a particular molecule, and therefore provide a more specific and accurate test, which is less easily confused by the presence of other molecules. The antibodies picked must have a high affinity for the antigen (if there is antigen available, a very high proportion of it must bind to the antibody).
Europium containing nanoparticles have been used previously as labels for time-resolved bioassays. The research team found that natural or untreated Eu2O3 particles are insoluble in water but are easily dissolved by acid during activation and conjugation, losing their desirable optical properties. Coating the particles by silanization protected the particle from being dissolved by acid, and provided useful functional groups for biological conjugation. Passive absorption of proteins is an alternative for surface functionalization that they also recently explored.
The derivatized nanoparticle compositions retain the optical properties of the native particles and enable the efficient and low-cost use of these nanoparticles to label and optionally separate or purify biological and other materials. The luminescence of the particles serves as an internal calibration for the assay and helps to avoid experimental error from particle loss
The assay device consists of using a single microchannel combined with external electromagnets for performing a fast immunoassay within a very small volume. Magnetic/luminescent nanoparticles provide an internal luminescent standard. A binding reaction is accelerated by applying an alternating magnetic field by alternately energizing electromagnets external to a microchannel, thus inducing oscillation and/or agitation of the particles and achieving better diffusion during incubation. Using the electromagnets, the particles are held in the channel for washing and luminescence detection steps. The luminescence of the particles serves as an internal calibration for the assay and helps to avoid experimental error from particle loss.
Also described is the synthesis and the properties of magnetic/luminescent core/shell particles, including magnetic cores of iron oxide doped with cobalt and neodymium (NdCoFe2O3) that are encapsulated in luminescent shells of europium-doped gadolinium oxide (EuGd2O3). Cobalt and neodymium were shown to improve the magnetic properties of iron oxides. In addition, doping of Eu ions into the Gd2O3 matrix gives unique luminescent properties. The manufacturing methods employ flame spray pyrolysis as a cost-effective, high throughput and versatile synthesis method, allowing a variety of doped materials to be obtained.
