Mechanisms of interaction in acoustic plate mode immunosensors

Acoustic plate mode (APM) sensors have been used to detect immunochemical reactions in on-line measurements. In order to determine the exact mechanisms of interaction involved and to enhance reproducibility, both metallized and non-metallized devices have been investigated. The metallization is found to reduce total frequency shifts by 40–50%, an effect which must be attributed to either acoustoelectric interaction with the protein layer or different mass sensitivities for the different surface boundary conditions. In spite of the lower frequency shifts, metallized sensors may be advantageous for detecting biochemical reactions in ionic solutions because spurious signals are found to be effectively eliminated.