Evaluation of detectable depth on SH-SAW biosensor using antibody, antigen, and secondary antibody complexes

A shear horizontal surface acoustic wave(SH-SAW) based sensor measures multiple physical quantities of liquid specimens at the same time. Taking advantage of this measurement feature, SH-SAW sensors have been applied to wide varieties of sensors. SH-SAW biosensor is a form of SH-SAW sensor applications. SH-SAW biosensor detects immunoreactions occurring on its sensing area as velocity and/or amplitude changes of SH-SAW. Besides, SH-SAW biosensor has a sensing property determined by depth of sensing area, which is called a viscous penetration depth. However, previous studies have neglected structures of measuring objects. In other words, mass of detecting objects concentrate on sensing area. In order to clarify sensing properties in height direction of SH-SAW biosensor, we measured two different size of proteins, one is a C-reactive protein, CRP, and the other is a conjugate of CRP antigen and anti-CRP antibody. The results of the experiments showed a different velocity-amplitude change ratio in each molecular size. As the amplitude change of SH-SAW shows viscosity of specimen, this is considered to be reflected size difference of molecule. This result is considered to be suggested a structure analysis potential of SH-SAW biosensor.