Under-oil open microfluidic system (UOMS) for studying systemic fungal infection

Project Summary/Abstract
Opportunistic fungal pathogens are a leading cause of healthcare associated bloodstream infections. Candida
yeasts, specifically, cause 80-90% of biofilm-associated invasive fungal infections and mortality rates can
approach 50%. Furthermore, the incidence of Candida infections is rising with the increased use of catheter and
other device-based interventions. To date, the majority of work related to fungal infections and potential
treatments has focused on biofilms and their prevention. However, recent evidence suggests that the dispersion
of yeast cells from the biofilm (into the bloodstream) and the persistence of these dispersed cells are
perhaps more important virulence factors and represent significant but underutilized treatment targets.
Further, existing assays and instrumentation are not amenable to measuring dispersion and phenotyping
dispersed cells. Nor do they recapitulate in vivo conditions (e.g. flow, interaction with host cells). Thus, here we
will develop a new type of under-oil open microfluidic system (UOMS) to quantify the dispersive capacity of
biofilms and assess the phenotype of dispersed cells in Candida mutants and clinical isolates. The UOMS
platform is built on the foundation of a newly observed phenomena called Exclusive Liquid Repellency (ELR).
ELR provides a unique environment where liquid is completely repelled from a solid surface to eliminate
biofouling. Additionally, ELR expands the capabilities of simple open microfluidic devices allowing us to
overcome the limitations of current methods and provide a system capable of quantitatively studying fungal
dispersion. We will first (Aim 1) develop an under-oil microchannel device to measure the dispersive capacity of
Candida biofilms and virulence phenotypes. Second (Aim 2) we will automate the UOMS and develop a single-
cell distribution assay to measure the phenotype of individual dispersed cells. And finally (Aim 3), we will use the
UOMS platform to develop dispersion phenotype profiles for Candida mutant libraries and clinical isolates. We
will measure the dispersive capacity and phenotype of dispersed cells from hundreds of Candida albicans clinical
isolates and mutants available in existing libraries, providing clues to the genetic determinants of dispersion.

Grant Number: 5R01AI154940-05
NIH Institute/Center: NIH
Principal Investigator: David Beebe