Low-Level Detection of a Bacillus Anthracis Simulant using Love-Wave Biosensors on 36 Degree YX LiTaO3

Abstract

Crucial to low-level detection of biowarfare agents in aqueous environments is the mass sensitivity optimization of Love-wave acoustic sensors. 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 (DL) 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 magnitude and phase shift across each sensor. Polyimide had the lowest mass detection limit with an estimated value of 1-2 ng/cm 2 , as compared to polystyrene where DL = 2.0 ng/cm 2 .Suitable chemistries were used to orient antibodies on the Love-wave sensor using adsorbed 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 4 preparation. This work demonstrates that Love-wave devices can be used to detect B. anthracis simulant below reported infectious levels.5

Identifying experimental surrogates for Bacillus anthracis spores: a review

“…B. anthracis stand-ins have also played an important role in evaluating the broad arsenal of techniques used to detect and identify bio-threat agents in the environment. At least 17 methods have been employed to detect spores of B. anthracis and its relatives, including: electron microscopy [ 64 ], atomic force microscopy [ 65 - 68 ], photothermal spectroscopy [ 69 ], microcalorimetric spectroscopy [ 70 ], biochip sensors [ 71 , 72 ], Raman spectroscopy [ 73 ], polymerase chain reaction methods [ 74 - 80 ], optical chromatography [ 81 ], differential mobility spectroscopy [ 82 ], laser induced breakdown spectroscopy [ 83 - 86 ], flow cytometry sorting [ 87 ], mass spectroscopy [ 88 - 96 ], proteomics [ 97 , 98 ], luminescence analysis [ 99 ], long-wave biosensors [ 100 ], lytropic liquid sensors [ 101 ] and fluorescent labelling [ 102 - 105 ]. Although most of these studies used B. anthracis directly, some included close relatives for comparisons of detectability across species.…”