úú PROJECT SUMMARY/ABSTRACT Delivering diagnostic services at the point-of-care (POC) can improve the quality of healthcare in clinics, in emergency settings, or at home, which can potentially ease hospitals’ burden, for instance, during the COVID- 19 pandemic. Precision and personalized medicine revolution also require POC testing to provide readily available biomarker information to clinicians. The goal of this career development proposal is to create fast, inexpensive, sensitive, and reliable molecular diagnostics to address the 21st-century healthcare challenges. The central hypothesis is that we can efficiently utilize computational protein design to create modular allosteric protein switches, named LOCKR (Latching Orthogonal Cage–Key pRotein), that enable the rapid and reversible conformational changes upon interaction. As a proof of principle, we demonstrate that LOCKR- based biosensors can be configured to produce bioluminescence upon the addition of clinical targets (e.g., botulinum toxin, cardiac troponin I, HER2 receptor, Fc domain, anti-HBV mAb, anti-SARS-CoV2 antibodies, and SARS-CoV2 receptor-binding domain/spike protein, Fig 1 and 2) in homogeneous “all-in-solution” assays. Due to the modularity of LOCKR sensor platform and the advance in de novo binder design for arbitrary protein targets, we proposed the integration of both features as the universal strategy to develop tailored biosensors for user-defined targets. The main specific aims for the independent phase are to iteratively expand LOCKR-based diagnostics with the synergy of (1) de novo protein binder design to directly detect various disease protein biomarkers, and (2) indirectly detect the antibodies that compete with the designed interface, as POC devices; and (3) to repurpose the original luminescence signal with other compatible readouts by exchanging the reporter modules. For more specific proof-of-concept projects during the mentored phase, I describe in Aim 1 the use of state-of-the-art computational protein design methods to create an interleukin-6 binder and biosensor. In Aim 2, I propose a general way to develop antibody biosensors by demonstrating COVID-19 serological tests as an example. With my expertise in biosensor engineering, I attempt in Aim 3 to develop a ratiometric bioluminescence resonance energy transfer (BRET) biosensor to analyze the HBV antibody and a colorimetric biosensor to measure human cardiac troponin I level. Ultimately, I anticipate this new sensor platform is significant for the development of robust protein sensors that will be broadly applicable to arbitrary targets and enabling its POC compatible readouts for future diagnostics.

úú PROJECT NARRATIVE Point-of-care diagnostics have shown the potential to transform health care by the real-time screening of disease states and treatment outcomes as needed. Alongside the computational protein design of de novo switches and binders, this proposal aims to develop a new class of reliable, rapid, and inexpensive protein biosensors at point-of-care that generate measurable light or color signals only when mixed with patient samples containing disease biomarkers with a drop of patient specimens. By enabling detection, the proposed projects align with the National Institute of Health’s mission to reduce illness and disability and to advance basic research and medical care.