A silicon-based ultrasonic immunoassay for detection of breast cancer antigens

The authors report on a silicon-based immunosensor package that has direct application to the diagnostic detection of a breast cancer antigen in the sera of breast cancer patients. The authors couple the flexural plate wave (FPW) gravimetric sensor (S.W. WenzeI, R.M. White, IEEE Trans. Electron Devices 35 (1988) 735-743) with a novel mass-amplifying label that increases sensor signal level (a shift of resonant frequency) from that of previous acoustic immunoassays, in which frequency shifts were due solely to the weight of the immunoglobulins. The use of a gravimetric immunoassay with a mass-amplifying label provides an alternative to radioimmunoassay, eliminating the need for radioactive labels that require costly disposal. In addition to gravimetric sensing, the FPW device is also capable of providing a source of ultrasonic agitation, which results in localized mixing near the active immunoglobulin binding area of the device. The authors have observed increased antibody binding using ultrasonic agitation during immunoglobulin incubation periods. Consequently, with ultrasonic agitation, the authors are able to reduce the length of time necessary to complete the immunoassay and also affect the amount of antibody binding. (C) 1998 Elsevier Science S.A. All rights reserved.