Capture, purification, and release of biological substances using a surface coating

A microfluidic chip for selectively enriching rare cells, the microfluidic chip comprising a substrate and a surface coating for capturing rare cells, wherein the surface coating comprises:

• (i) a bioactive composition which selectively binds to the rare cells, wherein the bioactive composition comprises an antibody;
• and
• (ii) a non-fouling composition that reduces binding of non-specific cells or adsorption of serum proteins compared to a surface coating lacking the non-fouling composition, wherein the non-fouling composition comprises a lipid layer;
• and
• wherein the antibody is non-covalently associated with the non-fouling composition.

A method of collecting rare cells from a biological sample, the method comprising:

• (a) contacting the biological sample to a microfluidic chip comprising a substrate and a surface coating for the capturing rare cells, wherein the surface coating comprises:
• (i) a bioactive composition which selectively binds to the rare cells, wherein the bioactive composition comprises an antibody;
• and
• (ii) a non-fouling composition that reduces binding of non-specific cells or adsorption of serum proteins compared to a surface coating lacking the non-fouling composition;
• (b) binding the rare cells to the antibody;
• (c) flowing a buffer at shear stress of from about 2.5 dyne/cm2 to about 12 dyne/cm2 through the microfluidic chip, thereby releasing non-specific cells from the non-fouling layer without releasing the rare cells bound to antibody from the microfluidic chip, wherein the antibody remains non-covalently associated with the non-fouling lipid layer;
• and
• (d) flowing a buffer at shear stress at least 50 dyne/cm2 through the microfluidic chip, thereby releasing the rare cells and the bioactive composition or the surface coating from the substrate.