High-volume biological sample processing using microwaves

Abstract

This paper describes the design and optimization of a 10 ml cartridge for patient sample processing using a 3.5 GHz (empty resonant frequency) TM010 cylindrical microwave cavity. The cartridge has been designed to augment a novel approach for the rapid diagnosis of M. tuberculosis (the causative agent of Ttuberculosis), which uses the direct application of microwaves to a bacteria-containing sample to release pathogen-specific DNA. The target bacterial DNA is then captured and recovered using magnetic nanoparticles coated with pathogen-specific DNA probes. Excitation parameters were optimized using three surrogates for M. tuberculosis, namely, M. smegmatis, M. abscessus, and M. bovis suspended in water and simulated sputum. The paper also explores the mechanism of microwave-mediated DNA release from bacteria using scanning electron microscopy. Examination of bacteria exposed to microwaves at power levels known to mediate the release of DNA reveals no obvious signs of permanent cell disruption, suggesting that a more subtle interaction is taking place. Finally, the presence of microwave-liberated M. bovis DNA was able to be detected at a level of sensitivity comparable to that achieved using microscopy.