Electrospray-Assisted Ultraviolet Aerodynamic Particle Sizer Spectrometer for Real-time Characterization of Bacterial Particles

摘要

The ultraviolet aerodynamic particle sizer (UVAPS) spec-ntrometer is a novel, commercially available aerosol counternfor real-time, continuous monitoring of viable bioaerosolsnbased on the fluorescence induced from living microor-nganisms. For aerosolization of liquid-based microorgan-nisms, general aerosolization methods such as atomizationnor nebulization may not be adequate for an accurate andnquantitative characterization of the microorganisms be-ncause of the formation of agglomerated particles. In suchncases, biological electrospray techniques have an advan-ntage because they generate nonagglomerated particles,nattributable to the repulsive electrical forces amongnparticles with unipolar charges. Biological electrospraysnare quickly gaining potential for the detection and controlnof living organisms in applications ranging from massnspectrometry to developmental microbiology. In thisnstudy, we investigated the size distribution, total concen-ntration, and fluorescence percentage of bacterial particlesnin a real-time manner by electrospray-assisted UVAPS. Ansuspension containing Escherichia coli as a test micro-norganism was sprayed in a steady cone-jet mode using anspecially designed electrospray system with a point-to-norifice-plate configuration based on charge-reduced elec-ntrospray size spectrometry.With the electrospray process,n98% of the total E. coli particle number concentration hadna size of 1 µm and the geometric mean diameter wasn0.779 µm, as compared with the respective values of 78%nand 0.907 µm after nebulization. The fractions of fluo-nrescence responsive particles and of particles that con-ntained viable organisms in culture were 12% and 7%,nrespectively, from the electrospray process and 34% andn24% from nebulization. These results demonstrate thatn(1) the presence of agglomerated particles can lead tonmarkedly overestimated fluorescence and culturabilitynpercentages compared with the values obtained fromnnonagglomerated particles, and (2) electrospray-assistednUVAPS can provide more accurate and quantitative real-