Carbon nanotubes-based chemiresistive biosensors for detection of microorganisms

The paper reports carbon nanotube (CNT)-based immunosensors for the detection of two types of microorganisms, bacteria and viruses. The pathogen Escherichia coli O157:H7 and the bacteriophage T7 were selected as model for bacteria and viruses, respectively, while E. coli K12 and the bacteriophage MS2 were used to assess the selectivity of the biosensor. The transduction element consisted of single-walled carbon nanotubes aligned in parallel bridging two gold electrodes to function as a chemiresistive biosensor. Single-walled carbon nanotubes (SWNTs) were functionalized with specific antibodies (Ab) for the different microorganisms by covalent immobilization to the non-covalently bound 1-pyrene butanoic acid succinimidyl ester. A significant increase in the resistance of the device was observed when the biosensor was exposed to E. coli O157:H7 whole cells or lysates with a limit of detection of 105 and 103 CFU (colony forming units)/mL, corresponding to 103 and 101 CFU/chip, respectively, while no response was observed when the biosensor was exposed to the E. coli K12. In the case of virus detection, a significant resistance increase was detected due to interaction of the bacteriophages with the Abs, with a limit of detection of 103 PFU/mL corresponding to 101 PFU/chip and excellent selectivity against MS2 bacteriophage. The sensor exhibited a fast response time of ∼5 min in the case of bacteriophage detection, while the response time for the detection of bacteria was 60 min.