Bioluminescent engineered Escherichia coli strains for testing of carbon nanotubes toxicity

The utilization of bacteria based biosensors for the study of toxic compounds is regarded as a key advancement for rapid and reliable detection of hazards for health and environment, such as the use of carbon nanotubes products in medicine and engineering. In this study the toxicity of carbon nanotubes, both multi-walled and single-walled configuration, was tested using the engineered bioluminescent Escherichia coli TV1061 and Escherichia coli DPD2794. The E. coli TV1061 strain is sensitive to protein damage, while the E. coli DPD2794 strain is sensitive to DNA damage. To compare the toxicity of the carbon nanotubes a standard for comparison was created using some elements of known toxicity such as alumina, copper and nickel, in nanoparticle form. Different protocols for the interaction between bacteria and toxic agents at different concentrations, temperatures and times were tested. The bioluminescent signal given off by the bacteria was analysed with luminometer and normalized as induction factor. Scanning electron microscope was used to evaluate cell surface modifications and damage, focusing on the interaction between nanoparticles and bacterial cells. For both strains the luminescence damage response followed a peculiarly shaped curve, which correlated to the toxic agent concentration and the maximum luminescence in a double peak, as shown in the table below.