The response of an acoustic wave homogeneous immunoassay to immune and non-immune solutions

The principle of operation of an acoustic wave homogeneous immunosensor (AWHI) is based on detecting a variation of the velocity of a bulk longitudinal acoustic wave caused by the reaction between antigen and antibody in a homogeneous solution. The measurement technique to measure velocity change is based on examining a variation of both the resonant frequency and the phase characteristic of the ultrasonic resonator. The AWHI sensor was tested with immune proteins human immunoglobulin G(IgG) as antigen and goat antibody to human IgG. Tested non-immune proteins were mock antigen and bovine serum albumin (BSA). The AWHI response to the non-immune proteins was different from the antigen antibody response. The AWHI responded with a reproducible signature to non immune proteins and the phase change was linear as a function of concentration. However, the sensor response to the immune solutions produced several different signatures. Some of these signatures were of an oscillatory character, and the phase change as a function of antigen concentration was scattered