Optical emission biosensing using magnetic beads with a fast aggregation time

An assay method for target molecules in a sample using optical emission from magnetic beads, comprising:

• a) preparing the magnetic beads so, if excited, reporter molecules connected to the beads produce optical emission as a consequence of contact between the beads, the reporter molecules, and target molecules in the sample;
• b) providing the prepared magnetic beads in a solution in a container, with one or more magnets producing a magnetic field inside the container that causes the beads to aggregate into a clump inside the container in less than 30 seconds;
• c) exciting the optical emission from the reporter molecules connected to the magnetic beads in the clump;
• and
• d) measuring the optical emission from the reporter molecules connected to the magnetic beads in the clump.

A system for measuring an optical emission signal from a quantity of magnetic beads in an assay of target molecules in a sample, comprising:

• a) a container configured for holding the magnetic beads in a volume of a solution;
• b) one or more magnets adjacent to the container, the magnets producing a magnetic field with a field gradient in the volume of solution that attracts the beads to form a clump at a bottom inner surface of the container adjacent to at least one of the magnets;
• c) detection optics and a light sensing device that receives and measures the optical emission signal from the clump of magnetic beads;
• and
• d) a recording device that outputs and/or stores data of the optical emission signal;
• wherein the one or more magnets are located below the container, and a dot product of the magnetic field and the field gradient, at a top of the volume of the solution directly above the one or more magnets is at least 0.05 teslas squared per meter.