Low-level detection of a Bacillus anthracis simulant using Love-wave biosensors on 36°YX LiTaO 3

Abstract

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°YX cut LiTaO 3 based Love-wave devices for detection of pathogenic spores in aqueous conditions. Given that the detection limit ( D l) 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/cm 2, as compared to polystyrene where D l=2.0 ng/cm 2. 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.