Aluminum-based materials for inactivation of aerosolized spores of Bacillus anthracis surrogates

Abstract

Energetic materials generating biocidal combustion products to disable airborne pathogenic microorganisms (including bio-threat agents) were designed as compounds of halogens and metals with high heats of oxidation. Thermally stable Al-based powders containing iodine and chlorine were prepared using ball-milling at room and cryogenic temperatures. Such powders can replace pure aluminum in metallized energetic formulations. Their stability and halogen release were quantified using thermo-gravimetric analysis. Ignition temperatures were determined by coating prepared powders onto an electrically heated filament. All prepared composites had lower ignition temperatures and longer combustion times compared to pure Al. In separate experiments, combustion products generated by injecting the prepared powders into an air-acetylene flame were mixed with a well-characterized bioaerosol. Inactivation of viable bioaerosol particles exposed to the heated combustion products for a short period of time (estimated to be 0.33 s) was quantified. The combustion products of materials investigated in this study effectively inactivated the aerosolized spores of two tested surrogates of Bacillus anthracis (B. atrophaeus and B. thuringiensis var kurstaki). A ternary composite with 20 wt% of iodine, 40 wt% of aluminum and 40 wt% of boron was found to be most attractive based on both its stability and efficiency in inactivating the aerosolized spores. The inactivation achieved was primarily attributed to chemical stresses as the thermal effect could not solely produce the high measured levels of inactivation. The findings point to a possible synergy of the thermal and chemical spore inactivation mechanisms.

Inactivation of aerosolized surrogates of Bacillus anthracis spores by combustion products of aluminum- and magnesium-based reactive materials: Effect of exposure time

“…Extensive researches have been recently carried out to develop ingredients for explosives and incendiaries, which produce combustion products capable of a drastic reduction of the spore viability at temperatures and on time scales typical for munition-target interactions. The present study builds upon the foundation created by previous efforts of this team (Zhang et al 2012;Grinshpun et al 2010aGrinshpun et al ,b, 2012Grinshpun et al , 2017Zhang et al 2010;Aly et al 2014;Wang et al 2016aWang et al ,b, 2017Abraham et al 2016). To be effective in a typical military application, aerosolized spores should be inactivated by factors of 10 4 or better, above 100 C, and within seconds or less.…”

“…Studies have generated substantial data on the spore inactivation by specific treatments, e.g., through exposure to heat and certain chemicals (Mullican et al 1971;Setlow et al 2002;Melly et al 2002;Rice et al 2005;Setlow 2006; Grinshpun et al 2010a;Johansson et al 2011;Adhikari et al 2016;Li et al 2017). Some studies have demonstrated that stressresistant bacterial spores exposed to elevated temperatures and products released from combustion of certain compositions can be effectively inactivated even over short exposure time intervals (Aly et al 2014;Wang et al 2015;Abraham et al 2016;Grinshpun et al 2017). A variety of halogens, especially iodine and chlorine, has been explored for inactivation of viable airborne spores (Tennen et al 2000;Burton et al 2008).…”

“…A variety of halogens, especially iodine and chlorine, has been explored for inactivation of viable airborne spores (Tennen et al 2000;Burton et al 2008). Iodine-containing metallic powders have been introduced as efficient combustible materials for inactivating aerosolized bioagents (Clark and Pantoya 2010;Zhang et al 2012;Grinshpun et al 2012Grinshpun et al , 2017Aly et al 2014). Novel aluminum-and magnesium-based powders with biocidal properties were synthesized by high-energy mechanical milling; some of these were evaluated under laboratory conditions against surrogates of Ba (Zhang et al 2010(Zhang et al , 2012Wang et al 2016a;Abraham et al 2016).…”

Reactive Structural Materials: Preparation and Characterization

“…Burn times measured for several nanocomposite RM powders prepared by mechanical milling and injected in an air‐acetylene flame are shown in Figure . These RMs contain such additives as I 2 , Cl 2 , or S, expected to generate biocidal combustion products aimed to inactivate biological agents, such as anthrax‐laced powders.…”

“…Burn times as a function of particle sizes for some RM powders containing biocidal additives, I 2 , Cl 2 , or S, burning while being injected in an air‐acetylene flame. Results for pure Al and Mg are shown for reference …”