Thermal Inactivation of Bacillus anthracis Using Laser Irradiation of Micro-Etched Platforms

The purpose of this research was to determine the probability of kill for a thermal inactivation strategy for use against biological agents; specifically the resilient endospore of Bacillus anthracis (Ba). The effort focused on short durations (milliseconds to several seconds) and temperatures (300 to 1300 K) simulating the periphery effects after an explosion generated by conventional munitions. For an improved statistical counting, applied microlithography techniques were used to produce micro-etched glass platforms consisting of 532 circular sample wells, evenly spaced. Small carbon black radiators, which provide fast heating/cooling rate and confined temperature distribution, were produced by populating the etched wells with fine carbon particles for good contact with the spores. In order to prevent the carbon black from oxidation at high temperatures in air, a multifunctional sol-gel coating was designed to cover both the hydrophilic glass surface and hydrophobic carbon surface. Ba spores were sparely populated into the small wells on another micro-etched platform for improved statistical counting. The platform with carbon wells was paired with the other platform populated with the spores by aligning row by row and column by column using a laser diffraction method aided with an infrared beam finder. The study refined techniques to populate the sample wells with as few as one Ba spore per well. This enables researchers to qualify, quantify, treat and measure small samples of spores over time. Spores were heated against black carbon wells using a solid state laser (Nd:YAG). Heating temperatures were varied by using different laser powers. The heating times were controlled by adjusting the raster rate of the sample relative to the laser beam