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Introduction: Multiple factors influence the viability of aerosolized bacteria. The delivery of aerosols is affected by chamber conditions (humidity, temperature, and pressure) and bioaerosol characteristics (particle number, particle size distribution, and viable aerosol concentration). Measurement of viable aerosol concentration and particle size is essential to optimize viability and lung delivery. The Madison chamber is widely used to expose small animals to infectious aerosols., Methods: A multiplex sampling port was added to the Madison chamber to measure the chamber conditions and bioaerosol characteristics. Aerosols of three pathogens (Bacillus anthracis, Yersinia pestis, and Mycobacterium tuberculosis) were generated under constant conditions and their bioaerosol characteristics were analyzed. Airborne microbes were captured using an impinger or BioSampler. The particle size distribution of airborne microbes was determined using an aerodynamic particle sizer (APS). Viable aerosol concentration, spray factor (viable aerosol concentration/inoculum concentration), and dose presented to the mouse were calculated. Dose retention efficiency and viable aerosol retention rate were calculated from the sampler titers to determine the efficiency of microbe retention in lungs of mice., Results: B. anthracis, Y. pestis, and M. tuberculosis aerosols were sampled through the port. The count mean aerodynamic sizes were 0.98, 0.77, and 0.78 μm with geometric standard deviations of 1.60, 1.90, and 2.37, and viable aerosol concentrations in the chamber were 211, 57, and 1 colony-forming unit (CFU)/mL, respectively. Based on the aerosol concentrations, the doses presented to mice for the three pathogens were 2.5e5, 2.2e4 and 464 CFU., Discussion: Using the multiplex sampling port we determined whether the animals were challenged with an optimum bioaerosol based on dose presented and respirable particle size., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Aerosol particles generated by inhalers for respiratory drug delivery acquire electrostatic charge during the dispersion process. The electrostatic charge distribution of the particles can affect the efficiency of drug delivery by influencing both the transport and deposition of inhaled particles in the human lung. To analyze the electrostatic charge acquired by the aerosol particles, two sets of metered-dose inhaler (MDI) and dry powder inhaler (DPI) devices were investigated. Both the particle size and charge distributions were measured simultaneously by using an electrical single-particle aerodynamic relaxation time (E-SPART) analyzer. The analyzer was calibrated with particles of known size, which were generated by a vibrating orifice aerosol generator (TSI Inc.) and charge using the Faraday cup method. The charge distributions of the pharmaceutical aerosols from both the DPI and MDI devices were bipolar in nature. Although the net charge-to-mass ratio was less than 0.2 microC/g, the individual particles were charged with a relatively high charge: -2 to + 2 microC/g. The count mean aerodynamic diameter of the aerosols generated from these devices was 3-5 microm.

A nose-only inhalation exposure system (NOIES) was evaluated for its performance in this study using test polystyrene latex spheres (PLS) and ectromelia virus (ECTV), which is a surrogate for variola virus, the causative agent of smallpox. The test aerosol sampled at the various ports of the NOIES was found to be consistent in particle size and number concentration. ECTV bio-aerosol was delivered to A/J mice strain and the lethal dose (LD50) value at which mortality was 50% was found to be 41 PFU/mL. The airborne ECTV particles were sampled and collected on TEM grids for particle size imaging using a scanning electron microscope (SEM) and structural integrity imaging using a transmission electron microscope (TEM). SEM images of ECTV after aerosolization showed the virions to be coated with the smaller size solute particles generated from the buffer solution during the aerosolization process. TEM images showed the ECTV to be structurally intact after undergoing the process of aerosolization. From the viable ECTV particle size distribution, the geometric mean diameter (GMD) of the airborne ECTV particles was calculated to be 278 nm with a geometric standard deviation (GSD) of 1.73. [ABSTRACT FROM AUTHOR]