Low-level detection of a bacillus anthracis simulant using Love-wave biosensors on 36 degrees YX LiTaO3

We present an acoustic Love-wave biosensor for detection of the Bacillus anthracis simulant, Bacillus thuringiensis at or below inhalational infectious levels. The present work is an experimental study of 36 degrees YX cut LiTaO3 based Love-wave devices for detection of pathogenic spores in aqueous conditions. Given that the detection limit (D1) of Love-wave-based sensors is a strong function of the overlying waveguide, two waveguide materials have been investigated, which are polyimide and polystyrene. To determine the mass sensitivity of Love-wave sensor, bovine serum albumin (BSA) protein was injected into the Love-wave test cell while recording the magnitude and phase shift across each sensor. Polyimide had the lowest mass detection limit with an estimated value of 1.0-2.0 ng/cm2, as compared to polystyrene where D1 = 2.0 ng/cm2. Suitable chemistries were used to orient antibodies on the Love-wave sensor using protein G. The thickness of each biofilm was measured using ellipsometry from which the surface concentrations were calculated. The monoclonal antibody BD8 with a high degree of selectivity for anthrax spores was used to capture the non-pathogenic simulant B. thuringiensis B8 spores. Bacillus subtilis spores were used as a negative control to determine whether significant non-specific binding would occur. Spore aliquots were prepared using an optical counting method, which permitted removal of background particles for consistent sample preparation. This work demonstrates that Love-wave biosensors are promising for low-level detection for whole-cell biological pathogens.