Detection of Bacillus anthracis Spores Using Phage-Immobilized Magnetostrictive Milli/Micro Cantilevers

A type of biosensor based on filamentous phage as bioprobe and magnetostricitve milli/micro-cantilever (MSMC) as a sensor platform is developed for in situ detection of Bacillus anthracis spores in water. The phages are immobilized onto the MSMCs' surface through physical absorption. It is found that the immobilized phages are attached onto the MSMCs' surface through their ends and have a highly packed 2-D configuration. The real-time detection of B. anthracis spores in water with different concentrations was conducted. The experimental results indicate that the smaller the MSMC, the better the detection limit. For example, the detection limit is 104 spores/ml and 105 spores/ml for the MSMCs in size of 1.4 mm × 0.8 mm × 35 μm and 2.8 mm × 1.0 mm × 35 μm, respectively. The SEM observations confirm that the shift in the characteristic frequency of the biosensor is due to the binding of spores on the sensor surface. It is also found that the density of the spores binding at the tip of the cantilever is higher than that in the middle. The specificity of the sensor was studied. It is found that the sensor can detect B. anthracis spores with a much higher binding affinity than the spores of B. cereus and B. megaterium.