(293d) Multiple Biomarker Detection Using SH-SAW Resonator Array

The specific detection of multiple biomarkers to assess disease state is critical before starting any treatment protocol. Though surface acoustic wave sensors have been successfully used to detect biomarkers and antigens, implementation has been limited to serial detection of typically one biomarker at a time. For simultaneous biomarker detection, we have developed a shear-horizontal surface acoustic wave (SH-SAW) array that uses six resonators each operating at 408 MHz. Each channel uses two-port resonators operating on 36º YX lithium tantalate (36º Y LTO) for use in fluidic environments. Crucial to this work was the development of a fluidic interface that permits surface bio-activation yet is easy to assemble while maintaining sufficient quality factor (Q) of the entire sensor assembly. The second major contribution is the development of a custom oscillator circuit that monitors the frequency shift of each channel simultaneously while minimizing channel cross-talk.

Motivation

To date nearly all SHSAW biosensors are configured as delay-lines for biological detection applications [1,2]. A major obstacle for acoustic biosensors is reducing attenuation due to viscous and capacitive loading as this impacts overall sensitivity. A major difference between delay-line devices and resonators is that even with high insertion loss the phase response is often preserved in delay-line devices whereas resonators cease to operate. For this reason SHSAW resonators must maintain a high Q with low acoustic loss packaging. In contrast to our previous work which used a four channel SHSAW array delay-line device [3], resonators offer the advantage of higher sensitivity, smaller package with multiple channels, oscillator based measurements, and high reproducibility. For use as commercial sensors, resonators offer greater advantages due to their superior reproducibility.

Early detection of ovarian cancer is imperative to ensure the patient's likelihood of survival. At this time a lack of early symptoms and the absence of a reliable screening test results in 70% of women being diagnosed after the cancer has spread beyond the ovary. Currently there are tests that screen for a single biomarker, CA-125. However, the current methods have proven to be unreliable and inaccurate. For example, increased serum levels of CA-125 are found in only half of the patients diagnosed with stage I ovarian cancer. The discovery of three novel biomarkers combined with the ability to simultaneously test them with the SH-SAW resonator array device, will be invaluable in establishing a definitive, reliable, accurate and economical test for early stage ovarian cancer.

References

1. Tamarin, O., S. "Real time device for biosensing: Design of a bacteriophage model using love acoustic waves." Biosensors and Bioelectronics 18: 755-763, 2003.

2. A. Malavé, U. Schlecht, T. M. A.Gronewold, M. Perpeet, and M. Tewes, "Lithium tantalate surface acoustic wave sensors for bio-analytical applications," IEEE Sensors, pp. 604-607, 2006.

3. D. W. Branch and T. L. Edwards, "Love Wave Acoustic Array Biosensor Platform for Autonomous Detection," in IEEE Intern. Ultrasonics Sym. New York, NY, 2008, pp. 260-263.