Droplet Microfluidics Technologies for Rapid Pathogen Identification and Susceptibility Testing
Tza-Huei (Jeff) Wang, Fellow IEEE
Mechanical Engineering & Biomedical Engineering Departments, Institute for NanoBioTechnology
Johns Hopkins University Baltimore, Maryland, USA
The talk focuses on the development of droplet microfluidic-based molecular tests for pathogen identification (ID) and phenotypic antimicrobial susceptibility testing (AST). First, I will talk about the “droplet magnetofluidics” technology that eliminates the need for large, complex instrumentation and fluidics typically associated with clinical laboratory nucleic acid amplification testing (NAAT). We have demonstrated that droplet magnetofluidics facilitates streamlined capturing and purification of nucleic acids from clinical samples for PCR detection in a USB disk-sized cartridge with a turn-around time of < 30 min. Automated transport of the nucleic acids captured on magnetic particles through discrete droplets of reagents within the cartridge provides integration of sample preparation and nucleic acid detection. Our recently developed platforms have demonstrated clinically relevant sensitivity and specificity for Hepatitis C viral tests from patient blood and detection of sexually transmitted diseases (STDs) from self-collected vaginal and urethral swab samples. Meanwhile, I will also introduce a rapid and integrated single-cell biosensing platform, termed dropFAST, for bacterial growth detection and antimicrobial susceptibility assessment. DropFAST utilizes a rapid resazurin-based fluorescent growth assay coupled with stochastic confinement of bacteria in 20 pL droplets to detect signal from growing bacteria after 1 h incubation, equivalent to 2–3 bacterial replications. Full integration of droplet generation, incubation, and detection into a single, uninterrupted stream also renders this platform uniquely suitable for in-line bacterial phenotypic growth assessment. To illustrate the concept of rapid digital antimicrobial susceptibility assessment, we employ the dropFAST platform for rapid AST of various pathogens associated with urinary tract infections (UTI) directly using urine samples.