Shear horizontal SAW biosensor on langasite

Pathogenic microbial agents can be introduced into food, water supplies, or atmosphere as a result of accidents, pollution, or terrorist activity. Sensitive and selective sensors are urgently needed to detect minute quantities of pathogens rapidly and accurately. SH SAW devices provide opportunities for the design of microbial sensing platforms that function in liquid media, where most other SAW modes fail. A SH SAW delay line device was designed and fabricated on a novel LGS SH orientation. The biosensor measurements were carried out using a network analyzer S-parameter and impedance characterization. A specialized flow through system was developed to perform liquid phase biological testing on the SH SAW device. Sensitivity to biomolecule binding in physiological solutions was tested by sequential binding of specific protein species to the modified sensing surface. A self-assembling monolayer of cysteamine was formed on the gold sensing region of the delay line and the resulting terminal amine moieties reacted with alkyl NHS-biotin to produce a biotin-rich sensor surface. The biotinylated sensor was then exposed sequentially to biotin-binding Neutravidin, biotin-modified rabbit IgG, and goat anti-rabbit IgG antibody. As each protein was bound sequentially to the sensing surface, marked changes in the delay line phase were recorded. The reported results demonstrating the capability of these devices for sensitive biochemical recognition in acequous solutions reveals an important development in SAW based biosensor technology.