Droplet-Based Microfluidic Platform for High-Throughput, Multi-Parameter Screening of Photosensitizer Activity

Abstract

We present a fully integrated droplet-based microfluidic platform for the high-throughput assessment of photodynamic therapy photosensitizer (PDT) efficacy on Escherichia coli. The described platform is able to controllably encapsulate cells and photosensitizer within pL-volume droplets, incubate the droplets over the course of several days, add predetermined concentrations of viability assay agents, expose droplets to varying doses of electromagnetic radiation, and detect both live and dead cells online to score cell viability. The viability of cells after encapsulation and incubation is assessed in a direct fashion, and the viability scoring method is compared to model live/dead systems for calibration. Final results are validated against conventional colony forming unit assays. In addition, we show that the platform can be used to perform concurrent measurements of light and dark toxicity of the PDT agents and that the platform allows simultaneous measurement of experimental parameters that include dark toxicity, photosensitizer concentration, light dose, and oxygenation levels for the development and testing of PDT agents.

Time-resolved, single-cell analysis of induced and programmed cell death via non-invasive propidium iodide and counterstain perfusion

“…Microscopic imaging approaches employing microfluidic devices containing cells prestained with PI and cell-wall permeant SYTO 9 have been reported for the live/dead quantification of bacterial cells111213, sperm cells14, and yeast15 and are, in principle, comparable to studies using fluorescence activated cell sorting (FACS). Conventional staining protocols using PI concentrations higher than 1 μM intended for sorting414, confirmation of cell lysis16, or cellular analytics17181920 have been described for prokaryotes and eukaryotes.…”

A self-triggered picoinjector in microfluidics

“…It should be noted that in the normal working region II of the picoinjector, the voltage is relatively low and comparable to others' work. 17,19,20 Moreover, there is an insulation layer between the electrode and the reagent, which avoids reagent contacting with electrodes directly. Therefore, reagent contamination and occurrence of electrochemical reactions are excluded in the picoinjector.…”

Discovery in Droplets

“…Culture of single yeast and bacteria cells in picoliter droplets suspended in fluorinated oil/surfactant systems over the course of 4–5 days is possible, 32,33 with encapsulated E. coli cell cultures demonstrating ~80% viability in droplets after 5 days. 34 …”