TRIS-buffered saline (TBS, 10X), with 0.5% Tween 20 is used as a wash buffer and for sample preparation in general immunoassay applications, Tween 20 reduces nonspecific binding and protein:protein interactions.TBS is often used for diluting secondary antibodies or streptavidin-AP conjugate. TBS-Tween 20 is often used for washing steps.