Immunoassay-based rapid diagnostic tests (RDTs) currently represent the leading means for point-of-care diagnosis of infectious diseases in developing contexts. These assays typically employ surface-immobilized IgG antibodies as affinity agents for the capture of disease-relevant biomarkers from patient samples. However, antibodies are prone to thermal denaturation and nonspecific binding events that can render test results unreliable, and their development is costly and time-intensive, which can increase costs to the end user. These characteristics limit the potential utility of antibody-based diagnostics in resource-constrained contexts, where cold chain storage may not be feasible and financial resources are limited. In order to better address these technological gaps, we are developing robust, minimalist, immuno-orthogonal affinity agents based on thermostable protein scaffolds, using yeast surface display and flow cytometric analysis. By incorporating these robust affinity agents into low-cost, multiplexed assay formats, we aim to enable the sensitive, specific, and timely diagnosis of high-priority infectious diseases at the point-of-care.
Polymer reaction engineering for affordable medical diagnostics
In addition to developing affinity agents better-suited for application in challenging environments, our group is seeking to further improve upon the RDT format by developing a new method of signal amplification for the transduction of positive binding events. Traditional colorimetric signal amplification methods such as enzymatic dye development or nanoparticle concentration are slow, they tend to produce low-contrast results, and they can produce false negative or false positive results if interpreted outside of the ideal time window for test development. In order to improve upon these techniques, our group has developed a novel means of signal read-out, termed photopolymerization-based amplification (PBA). This method, which uses a macrophotoinitiator conjugated to an affinity agent in the place of the dye-cleaving enzyme or gold nanoparticle, gives rise to a polymer film, visible to the unaided eye, upon exposure of a positive test strip to green light. PBA has been shown to yield a high-contrast, rapid, sensitive, and time-decoupled signal read-out, which could further enhance the suitability of RDTs for communities that could benefit. Our design choices made in incorporating PBA into the RDT format are informed by an awareness of the needs of the end-user, as well as a nuanced understanding of the reaction chemistry, developed over the course of studies exploring the capabilities of PBA on numerous surfaces and at varying reaction conditions.