Microscale diffusion immunoassay

A device for determining the presence or concentration of sample analyte particles in a medium comprising:

• (a) a laminar flow channel for contacting a first medium containing analyte particles with a second medium containing binding particles for binding to said analyte particles in adjacent laminar flow;
• (b) wherein in operation said analyte particles in said first medium diffuse into said second medium or said binding particles in said second medium diffuse into the first medium containing said analyte particles;
• and
• (c) means for detecting the presence or concentration of diffused particles.

A device for detecting the presence of at least first and second analyte particles in a first fluid comprising:

• (a) first inlet means for conducting a first fluid comprising said first and second analyte particles into a laminar flow channel;
• (b) second inlet means for conducting a second fluid comprising first and second binding particles for said first and second analyte particles, respectively, into said laminar flow channel;
• (c) a laminar flow channel in fluid communication with said first and second inlet means, comprising said first and second fluids in adjacent laminar flow, said flow channel having a length sufficient to allow said first analyte particles to diffuse into said second fluid and bind with said first binding particles to form first complexes;
• and to allow said second analyte particles to diffuse into said second fluid and bind with said second binding particles to form second complexes;
• and
• (d) means for detecting the presence of said first and second complexes.

A device for separating first and second analyte particles of similar size contained in a first fluid, in a diffusion separator, said device comprising:

• (a) a flow channel comprising a second fluid containing at least first and second binding particles for said first and second analyte particles, respectively, said first binding particles having a higher diffusion coefficient than said second binding particles, with said first analyte particles diffusing into said second fluid to bind with said first binding particles to form first complexes and said second analyte particles diffusing into said second fluid to bind with said second binding particles to form second complexes;
• (b) a first inlet into said channel on a first side of said channel, said first inlet containing said first fluid;
• (c) a second inlet on the second side of said flow channel containing an acceptor stream;
• (d) a first outlet on the second side of said flow channel downstream from said second inlet containing a stream predominantly comprising said first complexes;
• and
• (e) a second outlet on the second side of said flow channel downstream from said first outlet containing a stream containing said first and second complexes.