Point of care assays for therapeutic monitoring of HIV medication
Therapeutic drug monitoring (TDM) may become an essential component of personalized medicine, but the tools to facilitate TDM are currently too cumbersome and expensive for routine clinical use especially in resource-limited settings. The need for TDM is urgent in human immunodeficiency virus (HIV) care, where maintaining therapeutic levels of antiretroviral therapy (ART) is critical, and yet nearly half of the over 20 million people receiving ART do not maintain adequate adherence. Subtherapeutic drug concentrations put people at risk for developing drug-resistant virus, having persistent HIV viremia, immune dysregulation, and death. The long-term goal of this project is to develop point- of-care (POC) technologies for TDM and precision medicine in global health settings. We recently developed the REverSe TRanscrIptase Chain Termination (RESTRICT) enzymatic assay for rapid measurement of nucleotide reverse transcriptase inhibitors (NRTIs) – the backbone of HIV treatment and prevention regimens and thus an optimal target for HIV TDM. RESTRICT infers drug levels based on DNA chain termination. I demonstrated proof-of-concept RESTRICT assays with tenofovir diphosphate (TFV-DP), an NRTI used in over 90% of HIV treatment regimens and in all HIV prevention regimens. RESTRICT has immediate applications for measuring adherence to HIV medication and screening patients during HIV vaccine efficacy trials. We will develop assays for therapeutic monitoring of other enzyme inhibitors used in infectious and chronic disease management.
Capillary microfluidics for user-friendly, minimally instrumented, and scalable liquid delivery
The conventional view in the field was that self-powered and self-regulated microfluidic devices, that move liquids using only capillary forces defined by microchannel geometry and surface chemistry, required the high precision (∼10 um) and sub-micron surface roughness provided by cleanroom fabrication. Cleanroom fabrication increases the time and cost required to develop new designs and limits self-powered microfluidics to small volumes (≤10 uL) preventing their use in applications that where large sample volumes (>100 uL) need to be screened (e.g., bacteria detection in urine). We 3D-printed capillary microfluidics, developed design rules to ensure that they remained functional even with the larger dimensions and rougher surfaces achievable by 3D printing, and conducted proof of concept experiments to demonstrate pre-programmed liquid delivery. We applied these 3D-printed capillary microfluidic devices to detect clinically relevant bacteria concentrations in < 7 min. These self-powered microchips could provide rapid, sensitive, and user-friendly diagnosis of urinary tract infections in vulnerable and non-verbal populations such as infants. We also introduced a new design paradigm, called microfluidic chain reactions, that use identical air conduits to enable scalable sequential and/or simultaneous liquid delivery from hundreds of reservoirs without any external instruments. Microfluidic chain reactions are simple to design, can be rapidly prototyped with bench-top 3D printers, and can provide user-friendly and minimally instrumented automation in basic and translational research settings.