Quantum Dot Nanocrystals Coupled to DNA Aptamer Sensors for Biological Weapons Detection

We developed a sensor for the detection of microbial and molecular biological warfare agents. The completed sensor consists of a semiconducting nanocrystal quantum dot covalently linked to the 5 end of a pathogen-specific aptamer. The second portion of the sensor is an oligomer strand that is complementary to the aptamer and has a gold nanoparticle covalently bound to its 3 terminus. In testing the sensor against pathogen stimulants, it was found that molecular targets provided great reproducibility and selectivity. After optimizing the sensor parameters, detection limits for molecular stimulants were found to be at the nanomolar range, even in the presence of interfering species. On the other hand, microbial stimulants showed much less selectivity when tested against control spores. This was due, in part, to the inadequate onoff signaling of a solid substrate as opposed to the solution target described above. Similar behavior was observed false positives when testing against other biological entities such as E. coli and fungus. As well, it was found that the physiological state of the test spores strongly controls selectivity, i.e., spore state, vegetative state, or somewhere between, and should be the subject of future studies.