Bacteriophage-derivitized resonant cantilevers for the highly-specific detection of bacteria
A. Singh, N. Glass, S. Evoy
National Institute for Nanotechnology, CA
Keywords: bacteriophage, E.coli, chemical immobilization, gold surface, specific detection
Abstract:We have investigated protocols to perform covalent attachment of wild-type phages onto gold surfaces. The T4 phage was chosen as the model system using E. coli EC12 strain as the host bacteria. Control experiments were performed with 3 non-host bacterial strains (E. coli 6M1N1, NP 30 and NP 10) to ensure specificity of the bacterial capture. The immobilization technique enabled a density of attached phage as high as 18 ± 3 phages/µm2. These surfaces successfully captured the host E Coli with a density of 5 cells/100m2 while the non-host strains showed negligible binding confirming the high specificity of the attachment. This protocol was employed for the specific detection of E Coli using resonant microcantilevers. Higher resonant bending modes (7th and 8th) were used to quantify the mass of the attached bacteria. In the case of E. coli capture, shifts of resonant frequencies associated to the bacteria capture indicated the binding of 4.85 cells/100m2, in close agreement with the surface densities observed by fluorescence. No resonant shift was observed for the negative control strain, confirming again the specificity of the detection. This approach for specific detection of pathogenic bacteria could be employed in numerous other sensing platforms such as surface plasmon resonance and quartz-crystal microbalance.