UCLA

The ability to compartmentalize reactions into extremely small, nanoliter – femtoliter, volumes has enabled unprecedented sensitivity, and new research into biology and early stages of disease pathophysiology. Current paradigm of compartmentalization leverages ordered microwell arrays and microfluidic droplet generators to great monodisperse reaction compartments. However, these require significant specialized and costly infrastructure to build, maintain, and operate. These barriers inhibit their widespread adoption, limiting research progress. The aim of the work presented in this dissertation is to democratize these compartmentalized assays for the detection of protein biomarkers.

The first chapter serves as an introduction to the work. The second chapter outlines the development of a portable reader and multi-material particle-based assay to enable droplet compartmentalization in a standard well plate format, and readout on easily deployable reader. I show the utility of this platform to measure concentrations of a heart failure biomarker, N-Terminal pro-brain natriuretic peptide (NT-proBNP), down to current clinical cut-off of ~0.1 ng/ml. Through this system, we can enable testing at the current standard of care in low-resource settings and local clinics to quicken treatment decision times for patients.

Given the shift from a disease reactive to preventive care, it is critical to not only be able to diagnose patients but also longitudinally measure them to predict susceptibility to diseases before onset of symptoms, or to measure efficacy of current treatment towards preventing disease relapse. This requires accessible ultrasensitive technologies that can enable biomarker discovery, validation, and testing at larger scales. Such techniques are not only useful for clinical research, but can be used to discover new cellular pathways where effector proteins could be below the detection limits of current techniques. Chapters three and four describe the development of a hydrogel particle-based method to capture proteins from sample solution, and template monodisperse picolitre droplets. By leveraging an excess number of particles to number of target protein molecules in solution, this method enables digital enzyme-linked immunosorbent assay and single molecule sensitivity. The loading and capture of proteins per particle is guided by Poisson statistics, and the picolitre volume enables quick concentration of single enzyme amplified signals to detectable levels.

These work, leveraging particles to enable recognition of proteins and produce a measurable output lay the foundation for new lab on a particle technology for sensitive protein measurements.