TITLE: Critical angle reflection imaging (CARi) for label-free quantification of molecular interactions SUMMARY Measuring molecular interactions of proteins are critical for understanding protein functions and cellular processes, for discovery and validating biomarkers, and for developing and screening drugs. In particular, membrane proteins play key roles in many cellular functions and are the largest class of drug targets. Most popular methods for measuring membrane protein interaction kinetics involves extraction and purification of membrane proteins and stabilizing the proteins in an artificial lipid environment, which is not only time consuming and labor intensive, but also may introduce bias due to the loss of the native cellular microenvironment. We proposed to develop critical angle reflection imaging (CARi) as a breakthrough technology for in-situ cell- based studies of membrane protein binding interaction kinetics to advance the field of biomarker discovery and drug development. CARi builds upon surface plasmon resonance imaging (SPRi), acquiring many of its unique advantages, but overcoming many of its limitations. CARi uses an optical configuration similar to SPRi that measures light reflected from below the sensing surface, which is sensitive to molecular bindings induced refractive index changes above the sensing surface. This enables CARi to detect molecular interaction label- free and in real-time. However, unlike SPRi, CARi exhibits several distinct technological advances, including a ~10 times greater sensitivity, ~100 times greater vertical detection range for measuring entire cell surfaces, simultaneous fluorescence compatibility for orthogonal validation, broader wavelength of light selection, convenient use of glass-based surface chemistries, and simple low-cost glass sensor chips. In this fast-track STTR project, Biosensing Instrument Inc. (BI) will work with the inventor of CARi technology at Arizona State University to develop a commercial prototype multi-functional CARi instrument that can perform CARi, SPRi, and fluorescence imaging. We will also collaborate with potential customers in biomedical research and pharmaceutical industries to validate CARi performance and develop key applications. The success of this project will enable ultra-high sensitivity for label-free kinetic quantification of small molecule interactions on membrane proteins with single-cell resolution and permit simultaneous fluorescence imaging for orthogonal validation. This powerful capability of label-free in-situ cell-based kinetic binding analysis is greatly needed for expediting biomarker discovery, disease diagnosis and drug screening.