Stanley H. Sakai

Disrupting bacterial spores and cells using ultrasound applied through a solid interface

DNA sample processing cartridges that perform cell lysis using ultrasound require a sonication chamber with a wall, or interface, for the transfer of ultrasonic energy to the solution. The interface must present matched impedance to the transfer of energy, yet also provide a barrier to safely contain potential hazardous biological material. The use of a thin but solid polymeric interface was studied using interfaces with a range of frequency response characteristics to the ultrasonic excitation. Measurements of ultrasonically generated acoustic pressure, visual images of cavitation, and measurements of released nucleic acid from sonicated bacterial spores and cells were used to determine the parameters for optimum transfer of ultrasound. Data and theory presented show that cell lysis is a function of the natural frequency of the interface, the preload force between the interface and the ultrasonic transducer, and the amplitude of the transducer.