Generation of nonagglomerated airborne bacteriophage particles using an electrospray technique

Biological electrospray techniques are rapidly becoming a promising means for controlling living organisms in applications ranging from mass spectrometry to developmental biology. We investigated the generation characteristics of airborne MS2 bacteriophage particles <30 nm in size, using an electrospray technique. A suspension containing bacteriophage MS2 was sprayed in cone-jet mode using a specially designed electrospray system with a point-to-orifice-plate configuration mentioned in previous studies based on a charge reduced electrospray size spectrometry. The highly charged droplets were discharged rapidly into a radioactive neutralizer of Po(210). The electrosprayed airborne MS2 particles (23.8 +/- 0.49 nm GMD) maintained their monodisperse size distribution with good stability and uniformity for >1 h. Compared with the generation characteristics observed using the previous nebulization process (51.5 +/- 0.86 nm GMD), this electrospray technique produced nonagglomerated particles, resulting in a narrow size range of generated particles. The total MS2 particle number concentration and GMD increased with changes in the suspension flow rate from 5 to 25 microL/h. As the applied voltage increased in cone-jet mode, the GMD and culturable bacteriophage concentration decreased slightly. Our investigation shows that the electrospray process, driven by high-intensity electric fields, can be used for nanometer-sized living organisms.