In 1997, the Defense Advanced Research Projects Agency (DARPA) tasked us to develop a non-toxic decontamination agent that would be safe for decontamination of humans, surfaces and buildings following bio-terrorism and bio-warfare attacks. Bleach and gaseous paraformaldehyde are commonly used to decontaminate surfaces, but they can be highly toxic and are hard to use. We developed and tested water-in-soybean oil nanoemulsions, comprised of oil, detergent, solvent, and salts in water. The nanoemulsions have an average size in the range of 400-800 nm. These surfactant lipid preparations are stable for long periods of time and are non-toxic to skin and mucous membranes. We optimized the formulations so they have broad spectrum activity against bacteria (e.g., E. coli, Salmonella, S. aureus), enveloped viruses (e.g., HIV, Herpes simplex), fungi (e.g., Candida, Dermatophytes), and after addition of germination enhancers to the nanoemulsion, sporicidal activity was also achieved (e.g. for anthrax). This enhanced formulation achieves killing of B. anthracis, including spores, in 45-60 minutes by inducing germination and disrupting the germinating spores.
We performed extensive testing at the U.S. Army Proving Grounds at Dugway, Utah using an Anthrax simulant, Bacillus subtilus var. niger (B. globigii), which is a commonly used biological agent simulant. Using our nanoemulsion plus germination enhancer, we obtained a greater than 6 log reduction in B. globigii spores on various surfaces (carpet, ceiling tile, cement, painted metal, painted wallboards, and panel fabric) over a period of 4 days. Our treatment was the least toxic and irritant in comparison to all other treatment groups. Unlike other testing groups, some of which required facemask and complete body cover, our decontamination did not require special personal protection. These tests were further confirmed at appropriate biosafety level facilities for B. anthracis with similarly excellent results.
Accordingly, our nanoemulsion is an effective method for environmental decontamination of biological agents. Furthermore, our nanoemulsions have selective toxicity to microbes at concentrations that are non-irritating to skin or mucous membrane. This safety has been tested in several animal species and has been verified during human clinical trials. The safety margin of the nanoemulsion is due to the low level of detergent in each droplet, yet when acting in concert, these droplets have sufficient energy and surfactant to destabilize the targeted microbes without damaging healthy cells. As a result, the nanoemulsion can achieve a level of topical antimicrobial activity that has only been previously achieved by systemic antibiotics. For more information on topical applications, see Antimicrobial Nanoemulsions.