Microfluidic-based Point-of-Care Testing for Global Health

Point-of-care (POC) tests can improve the management of infectious diseases and clinical outcomes, through prompt diagnosis and appropriate delivery of treatments for preventable and treatable diseases, especially in resource-limited settings where health care infrastructure is weak, and access to quality and timely medical care is challenging. Microfluidics or lab-on-chip technology is appropriate for POC tests when general design constraints such as integration, portability, low power consumption, automation, and ruggedness are met. Although many POC tests have been designed for use in developed countries, they might not be readily transferable to resource-limited settings. These new technologies need to be accessible, affordable and practical to be implemented at resource-limited settings to save lives in developing countries. The overall goal of this dissertation is to develop microfluidic diagnostic devices which are practical and reliable for global health. We first focused on immunoassays, an important class of diagnostic tests which utilize antibodies to quantify host immunity or pathogen protein markers. We developed and evaluated a rapid, accurate, multiplexed, and portable microfluidic immunoassay for diagnosis of HIV and syphilis on hundreds of archived specimens (whole blood, plasma, and sera). Our assay exhibited performance equal to lab-based immunoassays in less than 20 minutes. In addition, our technique quantified signals using a handheld instrument, allowing for objective measurements as opposed to current rapid HIV tests which require subjective interpretation of band intensities. We further integrated three important off-chip processes in a diagnostic test - liquid handling, optical signal detection, and data communication – in a low-cost, versatile, handheld instrument capable of performing immunoassays on reagent-loaded (i.e. “ready-to-run”) cassettes at high analytical performance characteristic of ELISA but with the speed, portability and ease-of-use of a rapid test. We also evaluated this immunoassay device in Rwanda on archived samples and achieved analytical performance comparable to that of benchtop standards. To simplify the user interface and reduce the cost of the diagnostic device, we integrated our microfluidic immunoassay with a smartphone to replace computers or high-cost processors for diagnostic devices in low-resource settings. Our low-cost ($34), smartphone-supported device for a multiplexed immunoassay detected three antibody markers from HIV, treponemal- and non-treponemal syphilis from fingerstick whole blood simultaneously in 15 minutes. This device was designed to eliminate the number of manual steps, through the use of lyophilized secondary antibodies and anti-coagulant, preloaded reagents on cassette, and an automatic result readout. A step-by-step user guide was included on the smartphone to make the device simple enough to be used by an untrained operator. The analytical performance of the device was evaluated in Rwanda by local health care workers. We also accessed user experiences for improvement of the device in future. While immunoassays offer rapid and accurate diagnosis for infectious diseases, various infections cannot be confirmed using protein markers. Due to increasing clinical demand for detection of DNA and RNA signatures for diagnosis and monitoring of patients in resource-limited settings, we also explored how microfluidic and nanoparticle technologies can improve nucleic acid amplification test at the point of care. Nucleic acid tests are arguably some of the most challenging assays to develop due to additional steps required for sample pre-treatment (e.g. cell sorting, isolation, and lysis, as well as nucleic acid extraction), signal amplification (due to low physiological concentrations, target contamination, and instability) and product detection. Here we developed a sputum processor to isolate and lyse mycobacteria (M.smegmatis) from a more complex sample matrix, using magnetic beads-based target isolation to replace the need of a centrifuge or other complicated sample preparation technique. We also investigated a technique to detect Mycobacterium tuberculosis using multiplex polymerase chain reaction (PCR) and silver-gold amplification detection.